Whenever a slow-speed approach is noted, the pilot
should apply power to accelerate the airplane and
increase the lift to reduce the sink rate and to prevent
a stall. This should be done while still at a high
enough altitude to reestablish the correct approach
airspeed and attitude. If too slow and too low, it is
best to EXECUTE A GO-AROUND.
USE OF POWER
Power can be used effectively during the approach and
roundout to compensate for errors in judgment. Power
can be added to accelerate the airplane to increase lift
without increasing the angle of attack; thus, the descent
can be slowed to an acceptable rate. If the proper
landing attitude has been attained and the airplane is
only slightly high, the landing attitude should be
held constant and sufficient power applied to help
ease the airplane onto the ground. After the airplane
has touched down, it will be necessary to close the
throttle so the additional thrust and lift will be
removed and the airplane will stay on the ground.
HIGH ROUNDOUT
Sometimes when the airplane appears to temporarily
stop moving downward, the roundout has been made
too rapidly and the airplane is flying level, too high
above the runway. Continuing the roundout would
further reduce the airspeed, resulting in an increase
in angle of attack to the critical angle. This would
result in the airplane stalling and dropping hard onto
the runway. To prevent this, the pitch attitude should
be held constant until the airplane decelerates enough
to again start descending. Then the roundout can be
continued to establish the proper landing attitude.
This procedure should only be used when there is
adequate airspeed. It may be necessary to add a slight
amount of power to keep the airspeed from decreasing
excessively and to avoid losing lift too rapidly.
Although back-elevator pressure may be relaxed
slightly, the nose should not be lowered any perceptible
amount to make the airplane descend when fairly
close to the runway unless some power is added
momentarily. The momentary decrease in lift that
would result from lowering the nose and decreasing
the angle of attack may be so great that the airplane
might contact the ground with the nosewheel first,
which could collapse.
When the proper landing attitude is attained, the airplane
is approaching a stall because the airspeed is
decreasing and the critical angle of attack is being
approached, even though the pitch attitude is no longer
being increased.
It is recommended that a GO-AROUND be executed
any time it appears the nose must be lowered significantly
or that the landing is in any other way uncertain.
Figure 8-32. Change in glidepath and increase in descent rate for high final approach.
No Flaps
Full Flaps
Steeper Descent Angle
Increased Rate of Descent
8-28
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8-29
LATE OR RAPID ROUNDOUT
Starting the roundout too late or pulling the elevator
control back too rapidly to prevent the airplane from
touching down prematurely can impose a heavy load
factor on the wing and cause an accelerated stall.
Suddenly increasing the angle of attack and stalling the
airplane during a roundout is a dangerous situation
since it may cause the airplane to land extremely hard
on the main landing gear, and then bounce back into
the air. As the airplane contacts the ground, the tail will
be forced down very rapidly by the back-elevator pressure
and by inertia acting downward on the tail.
Recovery from this situation requires prompt and
positive application of power prior to occurrence of
the stall. This may be followed by a normal landing if
sufficient runway is available—otherwise the pilot
should EXECUTE A GO-AROUND immediately.
If the roundout is late, the nosewheel may strike the
runway first, causing the nose to bounce upward. No
attempt should be made to force the airplane back onto
the ground; a GO-AROUND should be executed
immediately.
FLOATING DURING ROUNDOUT
If the airspeed on final approach is excessive, it will
usually result in the airplane floating.
Before touchdown can be made, the airplane may be
well past the desired landing point and the available
runway may be insufficient. When diving an airplane
on final approach to land at the proper point, there will
be an appreciable increase in airspeed. The proper
touchdown attitude cannot be established without producing
an excessive angle of attack and lift. This will
cause the airplane to gain altitude or balloon.
Any time the airplane floats, judgment of speed,
height, and rate of sink must be especially acute. The
pilot must smoothly and gradually adjust the pitch attitude
as the airplane decelerates to touchdown speed
and starts to settle, so the proper landing attitude is
attained at the moment of touchdown. The slightest
Figure 8-33. Rounding out too high.
Figure 8-34. Floating during roundout.
Ch 08.qxd 5/7/04 8:08 AM Page 8-29
error in judgment and timing will result in either ballooning
or bouncing.
The recovery from floating will depend on the amount
of floating and the effect of any crosswind, as well as
the amount of runway remaining. Since prolonged
floating utilizes considerable runway length, it should
be avoided especially on short runways or in strong
crosswinds. If a landing cannot be made on the first
third of the runway, or the airplane drifts sideways, the
pilot should EXECUTE A GO-AROUND.
BALLOONING DURING ROUNDOUT
If the pilot misjudges the rate of sink during a landing
and thinks the airplane is descending faster than it
should, there is a tendency to increase the pitch attitude
and angle of attack too rapidly. This not only
stops the descent, but actually starts the airplane
climbing. This climbing during the roundout is
known as ballooning. Ballooning can
be dangerous because the height above the ground is
increasing and the airplane may be rapidly
approaching a stalled condition. The altitude gained
in each instance will depend on the airspeed or the
speed with which the pitch attitude is increased.
When ballooning is slight, a constant landing attitude
should be held and the airplane allowed to gradually
decelerate and settle onto the runway. Depending on
the severity of ballooning, the use of throttle may be
helpful in cushioning the landing. By adding power,
thrust can be increased to keep the airspeed from
decelerating too rapidly and the wings from suddenly
losing lift, but throttle must be closed immediately
after touchdown. Remember that torque will be created
as power is applied; therefore, it will be necessary
to use rudder pressure to keep the airplane straight as it
settles onto the runway.
When ballooning is excessive, it is best to EXECUTE
A GO-AROUND IMMEDIATELY; DO NOT
ATTEMPT TO SALVAGE THE LANDING. Power
must be applied before the airplane enters a stalled
condition.
The pilot must be extremely cautious of ballooning
when there is a crosswind present because the crosswind
correction may be inadvertently released or it
may become inadequate. Because of the lower airspeed
after ballooning, the crosswind affects the airplane
more. Consequently, the wing will have to be lowered
even further to compensate for the increased drift. It
is imperative that the pilot makes certain that the
appropriate wing is down and that directional control
is maintained with opposite rudder. If there is any
doubt, or the airplane starts to drift, EXECUTE A
GO-AROUND.
BOUNCING DURING TOUCHDOWN
When the airplane contacts the ground with a sharp
impact as the result of an improper attitude or an
excessive rate of sink, it tends to bounce back into the
air. Though the airplane’s tires and shock struts
provide some springing action, the airplane does not
bounce like a rubber ball. Instead, it rebounds into
the air because the wing’s angle of attack was
abruptly increased, producing a sudden addition of
lift.
The abrupt change in angle of attack is the result of
inertia instantly forcing the airplane’s tail downward
when the main wheels contact the ground sharply. The
severity of the bounce depends on the airspeed at the
moment of contact and the degree to which the angle
of attack or pitch attitude was increased.
Since a bounce occurs when the airplane makes contact
with the ground before the proper touchdown
Figure 8-35. Ballooning during roundout.
8-30
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8-31
attitude is attained, it is almost invariably accompanied
by the application of excessive back-elevator
pressure. This is usually the result of the pilot realizing
too late that the airplane is not in the proper attitude
and attempting to establish it just as the second touchdown
occurs.
The corrective action for a bounce is the same as for
ballooning and similarly depends on its severity. When
it is very slight and there is no extreme change in the
airplane’s pitch attitude, a follow-up landing may be
executed by applying sufficient power to cushion the
subsequent touchdown, and smoothly adjusting the
pitch to the proper touchdown attitude.
In the event a very slight bounce is encountered while
landing with a crosswind, crosswind correction must
be maintained while the next touchdown is made.
Remember that since the subsequent touchdown will
be made at a slower airspeed, the upwind wing will
have to be lowered even further to compensate for
drift.
Extreme caution and alertness must be exercised any
time a bounce occurs, but particularly when there is a
crosswind. Inexperienced pilots will almost invariably
release the crosswind correction. When one main
wheel of the airplane strikes the runway, the other
wheel will touch down immediately afterwards, and
the wings will become level. Then, with no crosswind
correction as the airplane bounces, the wind will cause
the airplane to roll with the wind, thus exposing even
more surface to the crosswind and drifting the airplane
more rapidly.
When a bounce is severe, the safest procedure is to
EXECUTE A GO-AROUND IMMEDIATELY. No
attempt to salvage the landing should be made. Full
power should be applied while simultaneously maintaining
directional control, and lowering the nose to a
safe climb attitude. The go-around procedure should
be continued even though the airplane may descend
and another bounce may be encountered. It would be
extremely foolish to attempt a landing from a bad
bounce since airspeed diminishes very rapidly in the
nose-high attitude, and a stall may occur before a
subsequent touchdown could be made.
PORPOISING
In a bounced landing that is improperly recovered,
the airplane comes in nose first setting off a series of
motions that imitate the jumps and dives of a porpoise—
hence the name. The problem is improper
airplane attitude at touchdown, sometimes caused by
inattention, not knowing where the ground is, mistrimming
or forcing the airplane onto the runway.
Ground effect decreases elevator control effectiveness
and increases the effort required to raise the nose. Not
enough elevator or stabilator trim can result in a noselow
contact with the runway and a porpoise develops.
Porpoising can also be caused by improper airspeed
control. Usually, if an approach is too fast, the airplane
floats and the pilot tries to force it on the runway when
the airplane still wants to fly. Agust of wind, a bump in
the runway, or even a slight tug on the control wheel
will send the airplane aloft again.
The corrective action for a porpoise is the same as for
a bounce and similarly depends on its severity. When
it is very slight and there is no extreme change in the
airplane’s pitch attitude, a follow-up landing may be
executed by applying sufficient power to cushion the
subsequent touchdown, and smoothly adjusting the
pitch to the proper touchdown attitude.
Small Angle
of Attack
Decreasing Angle
of Attack
Rapid Increase in
Angle of Attack
Normal Angle
of Attack
Figure 8-36. Bouncing during touchdown.
Ch 08.qxd 5/7/04 8:08 AM Page 8-31
When a porpoise is severe, the safest procedure is to
EXECUTE A GO-AROUND IMMEDIATELY. In a
severe porpoise, the airplane’s pitch oscillations can
become progressively worse, until the airplane strikes
the runway nose first with sufficient force to collapse
the nose gear. Pilot attempts to correct a severe porpoise
with flight control and power inputs will most
likely be untimely and out of sequence with the oscillations,
and only make the situation worse. No attempt
to salvage the landing should be made. Full power
should be applied while simultaneously maintaining
directional control, and lowering the nose to a safe
climb attitude.
WHEELBARROWING
When a pilot permits the airplane weight to become
concentrated about the nosewheel during the takeoff or
landing roll, a condition known as wheelbarrowing will
occur. Wheelbarrowing may cause loss of directional
control during the landing roll because braking action is
ineffective, and the airplane tends to swerve or pivot on
the nosewheel, particularly in crosswind conditions.
One of the most common causes of wheelbarrowing
during the landing roll is a simultaneous touchdown
of the main and nosewheel, with excessive speed,
followed by application of forward pressure on the
elevator control. Usually, the situation can be corrected
by smoothly applying back-elevator pressure.
However, if wheelbarrowing is encountered and
runway and other conditions permit, it may be advisable
to promptly initiate a go-around. Wheelbarrowing will
not occur if the pilot achieves and maintains the correct
landing attitude, touches down at the proper speed, and
gently lowers the nosewheel while losing speed on
rollout. If the pilot decides to stay on the ground rather
than attempt a go-around or if directional control is
lost, the throttle should be closed and the pitch attitude
smoothly but firmly rotated to the proper landing
attitude. Raise the flaps to reduce lift and to increase
the load on the main wheels for better braking action.
HARD LANDING
When the airplane contacts the ground during landings,
its vertical speed is instantly reduced to zero. Unless
provisions are made to slow this vertical speed and
cushion the impact of touchdown, the force of contact
with the ground may be so great it could cause
structural damage to the airplane.
The purpose of pneumatic tires, shock absorbing landing
gears, and other devices is to cushion the impact and to
increase the time in which the airplane’s vertical descent
is stopped. The importance of this cushion may be
understood from the computation that a 6-inch free fall
on landing is roughly equal, to a 340-foot-per-minute
descent. Within a fraction of a second, the airplane must
be slowed from this rate of vertical descent to zero,
without damage.
During this time, the landing gear together with some
aid from the lift of the wings must supply whatever
force is needed to counteract the force of the airplane’s
inertia and weight. The lift decreases rapidly as the
airplane’s forward speed is decreased, and the force
on the landing gear increases by the impact of
touchdown. When the descent stops, the lift will be
practically zero, leaving the landing gear alone to
carry both the airplane’s weight and inertia force.
The load imposed at the instant of touchdown may
easily be three or four times the actual weight of the
airplane depending on the severity of contact.
TOUCHDOWN IN A DRIFT OR CRAB
At times the pilot may correct for wind drift by crabbing
on the final approach. If the roundout and touchdown are
made while the airplane is drifting or in a crab, it will
contact the ground while moving sideways. This will
impose extreme side loads on the landing gear, and if
severe enough, may cause structural failure.
The most effective method to prevent drift in primary
training airplanes is the wing-low method. This technique
keeps the longitudinal axis of the airplane
aligned with both the runway and the direction of
motion throughout the approach and touchdown.
There are three factors that will cause the longitudinal
axis and the direction of motion to be misaligned
during touchdown: drifting, crabbing, or a combination
of both.
Decreasing Angle
of Attack
Decreasing Angle
of Attack
Rapid Increase in
Angle of Attack
Rapid Increase in
Angle of Attack
Normal Angle
of Attack
Normal Angle
of Attack
Figure 8-37. Porpoising.
8-32
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8-33
If the pilot has not taken adequate corrective action to
avoid drift during a crosswind landing, the main
wheels’ tire tread offers resistance to the airplane’s
sideward movement in respect to the ground.
Consequently, any sidewise velocity of the airplane is
abruptly decelerated, with the result that the inertia
force is as shown in figure 8-38. This creates a moment
around the main wheel when it contacts the ground,
tending to overturn or tip the airplane. If the windward
wingtip is raised by the action of this moment, all the
weight and shock of landing will be borne by one main
wheel. This could cause structural damage.
Figure 8-38. Drifting during touchdown.
Not only are the same factors present that are attempting
to raise a wing, but the crosswind is also acting on
the fuselage surface behind the main wheels, tending
to yaw (weathervane) the airplane into the wind. This
often results in a ground loop.
GROUND LOOP
A ground loop is an uncontrolled turn during ground
operation that may occur while taxiing or taking off,
but especially during the after-landing roll. Drift or
weathervaning does not always cause a ground loop,
although these things may cause the initial swerve.
Careless use of the rudder, an uneven ground surface,
or a soft spot that retards one main wheel of the airplane
may also cause a swerve. In any case, the initial
swerve tends to make the airplane ground loop,
whether it is a tailwheel-type or nosewheel-type.
Nosewheel-type airplanes are somewhat less prone to
ground loop than tailwheel-type airplanes. Since the
center of gravity (CG) is located forward of the main
landing gear on these airplanes, any time a swerve
develops, centrifugal force acting on the CG will tend
to stop the swerving action.
If the airplane touches down while drifting or in a crab,
the pilot should apply aileron toward the high wing and
stop the swerve with the rudder. Brakes should be used
to correct for turns or swerves only when the rudder is
inadequate. The pilot must exercise caution when
applying corrective brake action because it is very easy
to overcontrol and aggravate the situation.
If brakes are used, sufficient brake should be applied
on the low-wing wheel (outside of the turn) to stop the
swerve. When the wings are approximately level, the
new direction must be maintained until the airplane has
slowed to taxi speed or has stopped.
In nosewheel airplanes, a ground loop is almost always
a result of wheelbarrowing. The pilot must be aware that
even though the nosewheel-type airplane is less prone
than the tailwheel-type airplane, virtually every type of
airplane, including large multiengine airplanes, can be
made to ground loop when sufficiently mishandled.
WING RISING AFTER TOUCHDOWN
When landing in a crosswind, there may be instances
when a wing will rise during the after-landing roll. This
may occur whether or not there is a loss of directional
Wind Force
Center of
Gravity
Force Resisting
Side Motion
Inertia Force
Weight
Airplane Tips
and Swerves
CG Continues Moving in
Same Direction of Drift
Touchdown
Roundout
Roundout
Figure 8-39. Start of a ground loop.
Ch 08.qxd 5/7/04 8:08 AM Page 8-33
8-34
control, depending on the amount of crosswind and the
degree of corrective action.
Any time an airplane is rolling on the ground in a
crosswind condition, the upwind wing is receiving a
greater force from the wind than the downwind wing.
This causes a lift differential. Also, as the upwind wing
rises, there is an increase in the angle of attack, which
increases lift on the upwind wing, rolling the airplane
downwind.
When the effects of these two factors are great enough,
the upwind wing may rise even though directional
control is maintained. If no correction is applied, it is
possible that the upwind wing will rise sufficiently to
cause the downwind wing to strike the ground.
In the event a wing starts to rise during the landing roll,
the pilot should immediately apply more aileron pressure
toward the high wing and continue to maintain
direction. The sooner the aileron control is applied,
the more effective it will be. The further a wing is
allowed to rise before taking corrective action, the
more airplane surface is exposed to the force of the
crosswind. This diminishes the effectiveness of the
aileron.
HYDROPLANING
Hydroplaning is a condition that can exist when an
airplane is landed on a runway surface contaminated
with standing water, slush, and/or wet snow.
Hydroplaning can have serious adverse effects on
ground controllability and braking efficiency. The
three basic types of hydroplaning are dynamic
hydroplaning, reverted rubber hydroplaning, and viscous
hydroplaning. Any one of the three can render
an airplane partially or totally uncontrollable anytime
during the landing roll.
DYNAMIC HYDROPLANING
Dynamic hydroplaning is a relatively high-speed
phenomenon that occurs when there is a film of water
on the runway that is at least one-tenth inch deep. As the
speed of the airplane and the depth of the water increase,
the water layer builds up an increasing resistance to
displacement, resulting in the formation of a wedge of
water beneath the tire. At some speed, termed the
hydroplaning speed (VP), the water pressure equals the
weight of the airplane and the tire is lifted off the runway
surface. In this condition, the tires no longer contribute to
directional control and braking action is nil.
Dynamic hydroplaning is related to tire inflation
pressure. Data obtained during hydroplaning tests have
shown the minimum dynamic hydroplaning speed (VP)
of a tire to be 8.6 times the square root of the tire
pressure in pounds per square inch (PSI). For an
airplane with a main tire pressure of 24 pounds,
the calculated hydroplaning speed would be
approximately 42 knots. It is important to note that the
calculated speed referred to above is for the start of
dynamic hydroplaning. Once hydroplaning has
started, it may persist to a significantly slower speed
depending on the type being experienced.
REVERTED RUBBER HYDROPLANING
Reverted rubber (steam) hydroplaning occurs during
heavy braking that results in a prolonged locked-wheel
skid. Only a thin film of water on the runway is
required to facilitate this type of hydroplaning.
The tire skidding generates enough heat to cause the
rubber in contact with the runway to revert to its
original uncured state. The reverted rubber acts as a
seal between the tire and the runway, and delays
water exit from the tire footprint area. The water
heats and is converted to steam which supports the
tire off the runway.
Reverted rubber hydroplaning frequently follows an
encounter with dynamic hydroplaning, during which
time the pilot may have the brakes locked in an attempt
to slow the airplane. Eventually the airplane slows
enough to where the tires make contact with the
runway surface and the airplane begins to skid. The
remedy for this type of hydroplane is for the pilot to
release the brakes and allow the wheels to spin up
and apply moderate braking. Reverted rubber
hydroplaning is insidious in that the pilot may not
know when it begins, and it can persist to very slow
groundspeeds (20 knots or less).
VISCOUS HYDROPLANING
Viscous hydroplaning is due to the viscous properties
of water. A thin film of fluid no more than one
thousandth of an inch in depth is all that is needed. The
tire cannot penetrate the fluid and the tire rolls on top
of the film. This can occur at a much lower speed than
dynamic hydroplane, but requires a smooth or smooth
acting surface such as asphalt or a touchdown area
coated with the accumulated rubber of past landings.
Such a surface can have the same friction coefficient
as wet ice.
When confronted with the possibility of hydroplaning,
it is best to land on a grooved runway (if available).
Touchdown speed should be as slow as possible
consistent with safety. After the nosewheel is
lowered to the runway, moderate braking should be
applied. If deceleration is not detected and
hydroplaning is suspected, the nose should be raised
and aerodynamic drag utilized to decelerate to a
point where the brakes do become effective.
Proper braking technique is essential. The brakes
should be applied firmly until reaching a point just
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8-35
short of a skid. At the first sign of a skid, the pilot
should release brake pressure and allow the wheels to
spin up. Directional control should be maintained as
far as possible with the rudder. Remember that in a
crosswind, if hydroplaning should occur, the
crosswind will cause the airplane to simultaneously
weathervane into the wind as well as slide downwind.
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8-36
Ch 08.qxd 5/7/04 8:08 AM Page 8-36
9-1
PERFORMANCE MANEUVERS
Performance maneuvers are used to develop a high
degree of pilot skill. They aid the pilot in analyzing the
forces acting on the airplane and in developing a fine
control touch, coordination, timing, and division of
attention for precise maneuvering of the airplane.
Performance maneuvers are termed “advanced”
maneuvers because the degree of skill required for
proper execution is normally not acquired until a pilot
has obtained a sense of orientation and control feel in
“normal” maneuvers. An important benefit of
performance maneuvers is the sharpening of
fundamental skills to the degree that the pilot can cope
with unusual or unforeseen circumstances occasionally
encountered in normal flight.
Advanced maneuvers are variations and/or
combinations of the basic maneuvers previously
learned. They embody the same principles and
techniques as the basic maneuvers, but require a higher
degree of skill for proper execution. The student,
therefore, who demonstrates a lack of progress in the
performance of advanced maneuvers, is more than
likely deficient in one or more of the basic maneuvers.
The flight instructor should consider breaking the
advanced maneuver down into its component basic
maneuvers in an attempt to identify and correct
the deficiency before continuing with the
advanced maneuver.
STEEP TURNS
The objective of the maneuver is to develop the
smoothness, coordination, orientation, division of
attention, and control techniques necessary for the
execution of maximum performance turns when the
airplane is near its performance limits. Smoothness of
control use, coordination, and accuracy of execution
are the important features of this maneuver.
The steep turn maneuver consists of a turn in either
direction, using a bank angle between 45 to 60°. This
will cause an overbanking tendency during which
maximum turning performance is attained and
relatively high load factors are imposed. Because of the
high load factors imposed, these turns should be
performed at an airspeed that does not exceed the
airplane’s design maneuvering speed (VA). The
principles of an ordinary steep turn apply, but as a
practice maneuver the steep turns should be continued
until 360° or 720° of turn have been completed.
Figure 9-1. Steep turns.
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9-2
An airplane’s maximum turning performance is its
fastest rate of turn and its shortest radius of turn, which
change with both airspeed and angle of bank. Each
airplane’s turning performance is limited by the
amount of power its engine is developing, its
limit load factor (structural strength), and its
aerodynamic characteristics.
The limiting load factor determines the maximum
bank, which can be maintained without stalling or
exceeding the airplane’s structural limitations. In most
small planes, the maximum bank has been found to be
approximately 50° to 60°.
The pilot should realize the tremendous additional load
that is imposed on an airplane as the bank is increased
beyond 45°. During a coordinated turn with a 70°
bank, a load factor of approximately 3 Gs is placed on
the airplane’s structure. Most general aviation type
airplanes are stressed for approximately 3.8 Gs.
Regardless of the airspeed or the type of airplanes
involved, a given angle of bank in a turn, during which
altitude is maintained, will always produce the same
load factor. Pilots must be aware that an additional load
factor increases the stalling speed at a significant
rate—stalling speed increases with the square root of
the load factor. For example, a light plane that stalls at
60 knots in level flight will stall at nearly 85 knots in a
60° bank. The pilot’s understanding and observance of
this fact is an indispensable safety precaution for the
performance of all maneuvers requiring turns.
Before starting the steep turn, the pilot should ensure
that the area is clear of other air traffic since the rate of
turn will be quite rapid. After establishing the
manufacturer’s recommended entry speed or the
design maneuvering speed, the airplane should be
smoothly rolled into a selected bank angle between 45
to 60°. As the turn is being established, back-elevator
pressure should be smoothly increased to increase the
angle of attack. This provides the additional wing lift
required to compensate for the increasing load factor.
After the selected bank angle has been reached, the
pilot will find that considerable force is required on the
elevator control to hold the airplane in level flight—to
maintain altitude. Because of this increase in the force
applied to the elevators, the load factor increases
rapidly as the bank is increased. Additional
back-elevator pressure increases the angle of attack,
which results in an increase in drag. Consequently,
power must be added to maintain the entry altitude
and airspeed.
Eventually, as the bank approaches the airplane’s
maximum angle, the maximum performance or
structural limit is being reached. If this limit is
exceeded, the airplane will be subjected to excessive
structural loads, and will lose altitude, or stall. The
limit load factor must not be exceeded, to prevent
structural damage.
During the turn, the pilot should not stare at any one
object. To maintain altitude, as well as orientation,
requires an awareness of the relative position of the
nose, the horizon, the wings, and the amount of bank.
The pilot who references the aircraft’s turn by
watching only the nose will have difficulty holding
altitude constant; on the other hand, the pilot who
watches the nose, the horizon, and the wings can
usually hold altitude within a few feet. If the altitude
begins to increase, or decrease, relaxing or increasing
the back-elevator pressure will be required as
appropriate. This may also require a power adjustment
to maintain the selected airspeed. A small increase or
decrease of 1 to 3° of bank angle may be used to
control small altitude deviations. All bank angle
changes should be done with coordinated use of
aileron and rudder.
The rollout from the turn should be timed so that the
wings reach level flight when the airplane is exactly
on the heading from which the maneuver was started.
While the recovery is being made, back-elevator
pressure is gradually released and power reduced, as
necessary, to maintain the altitude and airspeed.
Common errors in the performance of steep turns are:
• Failure to adequately clear the area.
• Excessive pitch change during entry or recovery.
• Attempts to start recovery prematurely.
• Failure to stop the turn on a precise heading.
• Excessive rudder during recovery, resulting in
skidding.
• Inadequate power management.
• Inadequate airspeed control.
• Poor coordination.
• Gaining altitude in right turns and/or losing
altitude in left turns.
• Failure to maintain constant bank angle.
• Disorientation.
• Attempting to perform the maneuver
by instrument reference rather than visual
reference.
• Failure to scan for other traffic during the
maneuver.
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9-3
STEEP SPIRAL
The objective of this maneuver is to improve pilot
techniques for airspeed control, wind drift control,
planning, orientation, and division of attention. The
steep spiral is not only a valuable flight training
maneuver, but it has practical application in providing
a procedure for dissipating altitude while remaining
over a selected spot in preparation for landing,
especially for emergency forced landings.
Asteep spiral is a constant gliding turn, during which a
constant radius around a point on the ground is
maintained similar to the maneuver, turns around a
point. The radius should be such that the steepest bank
will not exceed 60°. Sufficient altitude must be
obtained before starting this maneuver so that the
spiral may be continued through a series of at least
three 360° turns. The maneuver should
not be continued below 1,000 feet above the surface
unless performing an emergency landing in
conjunction with the spiral.
Operating the engine at idle speed for a prolonged
period during the glide may result in excessive engine
cooling or spark plug fouling. The engine should be
cleared periodically by briefly advancing the throttle
to normal cruise power, while adjusting the pitch
attitude to maintain a constant airspeed. Preferably,
this should be done while headed into the wind to
minimize any variation in groundspeed and radius
of turn.
After the throttle is closed and gliding speed is
established, a gliding spiral should be started and a turn
of constant radius maintained around the selected spot
on the ground. This will require correction for wind
drift by steepening the bank on downwind headings
and shallowing the bank on upwind headings, just as in
the maneuver, turns around a point. During the
descending spiral, the pilot must judge the direction
and speed of the wind at different altitudes and make
appropriate changes in the angle of bank to maintain a
uniform radius.
A constant airspeed should also be maintained
throughout the maneuver. Failure to hold the airspeed
constant will cause the radius of turn and necessary
angle of bank to vary excessively. On the downwind
side of the maneuver, the steeper the bank angle, the
lower the pitch attitude must be to maintain a given
airspeed. Conversely, on the upwind side, as the bank
angle becomes shallower, the pitch attitude must be
raised to maintain the proper airspeed. This is
necessary because the airspeed tends to change as the
bank is changed from shallow to steep to shallow.
During practice of the maneuver, the pilot should
execute three turns and roll out toward a definite object
or on a specific heading. During the rollout,
smoothness is essential, and the use of controls must
be so coordinated that no increase or decrease of speed
results when the straight glide is resumed.
Figure 9-2. Steep spiral.
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9-4
Common errors in the performance of steep spirals are:
• Failure to adequately clear the area.
• Failure to maintain constant airspeed.
• Poor coordination, resulting in skidding and/or
slipping.
• Inadequate wind drift correction.
• Failure to coordinate the controls so that no
increase/decrease in speed results when straight
glide is resumed.
• Failure to scan for other traffic.
• Failure to maintain orientation.
CHANDELLE
The objective of this maneuver is to develop the pilot’s
coordination, orientation, planning, and accuracy of
control during maximum performance flight.
A chandelle is a maximum performance climbing turn
beginning from approximately straight-and-level
flight, and ending at the completion of a precise 180°
of turn in a wings-level, nose-high attitude at the
minimum controllable airspeed. The
maneuver demands that the maximum flight
performance of the airplane be obtained; the airplane
should gain the most altitude possible for a given
degree of bank and power setting without stalling.
Since numerous atmospheric variables beyond control
of the pilot will affect the specific amount of altitude
gained, the quality of the performance of the
maneuver is not judged solely on the altitude gain, but
by the pilot’s overall proficiency as it pertains to climb
performance for the power/bank combination used,
and to the elements of piloting skill demonstrated.
Prior to starting a chandelle, the flaps and gear (if
retractable) should be in the UP position, power set to
cruise condition, and the airspace behind and above
clear of other air traffic. The maneuver should be
entered from straight-and-level flight (or a shallow
dive) and at a speed no greater than the maximum
entry speed recommended by the manufacturer—in
most cases not above the airplane’s design
maneuvering speed (VA).
After the appropriate airspeed and power setting have
been established, the chandelle is started by smoothly
entering a coordinated turn with an angle of bank
appropriate for the airplane being flown. Normally,
this angle of bank should not exceed approximately
30°. After the appropriate bank is established, a
climbing turn should be started by smoothly applying
back-elevator pressure to increase the pitch attitude at
a constant rate and to attain the highest pitch attitude
as 90° of turn is completed. As the climb is initiated in
airplanes with fixed-pitch propellers, full throttle may
be applied, but is applied gradually so that the
maximum allowable r.p.m. is not exceeded. In
airplanes with constant-speed propellers, power may
be left at the normal cruise setting.
Figure 9-3. Chandelle.
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9-5
Once the bank has been established, the angle of bank
should remain constant until 90° of turn is completed.
Although the degree of bank is fixed during this
climbing turn, it may appear to increase and, in fact,
actually will tend to increase if allowed to do so as the
maneuver continues.
When the turn has progressed 90° from the original
heading, the pilot should begin rolling out of the bank
at a constant rate while maintaining a constant-pitch
attitude. Since the angle of bank will be decreasing
during the rollout, the vertical component of lift will
increase slightly. For this reason, it may be necessary
to release a slight amount of back-elevator pressure in
order to keep the nose of the airplane from rising
higher.
As the wings are being leveled at the completion of
180° of turn, the pitch attitude should be noted by
checking the outside references and the attitude
indicator. This pitch attitude should be held
momentarily while the airplane is at the minimum
controllable airspeed. Then the pitch attitude may be
gently reduced to return to straight-and-level
cruise flight.
Since the airspeed is constantly decreasing throughout
the maneuver, the effects of engine torque become
more and more prominent. Therefore, right-rudder
pressure is gradually increased to control yaw and
maintain a constant rate of turn and to keep the airplane
in coordinated flight. The pilot should maintain
coordinated flight by the feel of pressures being
applied on the controls and by the ball instrument of
the turn-and-slip indicator. If coordinated flight is
being maintained, the ball will remain in the center of
the race.
To roll out of a left chandelle, the left aileron must be
lowered to raise the left wing. This creates more drag
than the aileron on the right wing, resulting in a
tendency for the airplane to yaw to the left. With the
low airspeed at this point, torque effect tries to make
the airplane yaw to the left even more. Thus, there are
two forces pulling the airplane’s nose to the left—
aileron drag and torque. To maintain coordinated
flight, considerable right-rudder pressure is required
during the rollout to overcome the effects of aileron
drag and torque.
In a chandelle to the right, when control pressure is
applied to begin the rollout, the aileron on the right
wing is lowered. This creates more drag on that wing
and tends to make the airplane yaw to the right. At the
same time, the effect of torque at the lower airspeed is
causing the airplane’s nose to yaw to the left. Thus,
aileron drag pulling the nose to the right and torque
pulling to the left, tend to neutralize each other. If
excessive left-rudder pressure is applied, the rollout
will be uncoordinated.
The rollout to the left can usually be accomplished
with very little left rudder, since the effects of aileron
drag and torque tend to neutralize each other.
Releasing some right rudder, which has been applied
to correct for torque, will normally give the same effect
as applying left-rudder pressure. When the wings
become level and the ailerons are neutralized, the
aileron drag disappears. Because of the low airspeed
and high power, the effects of torque become the more
prominent force and must continue to be controlled
with rudder pressure.
A rollout to the left is accomplished mainly by
applying aileron pressure. During the rollout,
right-rudder pressure should be gradually released, and
left rudder applied only as necessary to maintain
coordination. Even when the wings are level and
aileron pressure is released, right-rudder pressure must
be held to counteract torque and hold the nose straight.
Common errors in the performance of chandelles are:
• Failure to adequately clear the area.
• Too shallow an initial bank, resulting in a stall.
• Too steep an initial bank, resulting in failure to
gain maximum performance.
• Allowing the actual bank to increase after establishing
initial bank angle.
• Failure to start the recovery at the 90° point in
the turn.
• Allowing the pitch attitude to increase as the
bank is rolled out during the second 90° of turn.
• Removing all of the bank before the 180° point
is reached.
• Nose low on recovery, resulting in too much
airspeed.
• Control roughness.
• Poor coordination (slipping or skidding).
• Stalling at any point during the maneuver.
• Execution of a steep turn instead of a climbing
maneuver.
• Failure to scan for other aircraft.
• Attempting to perform the maneuver by
instrument reference rather than visual reference.
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9-6
LAZY EIGHT
The lazy eight is a maneuver designed to develop
perfect coordination of controls through a wide range
of airspeeds and altitudes so that certain accuracy
points are reached with planned attitude and airspeed.
In its execution, the dive, climb, and turn are all
combined, and the combinations are varied and applied
throughout the performance range of the airplane. It is
the only standard flight training maneuver during
which at no time do the forces on the controls
remain constant.
The lazy eight as a training maneuver has great value
since constantly varying forces and attitudes are
required. These forces must be constantly coordinated,
due not only to the changing combinations of banks,
dives, and climbs, but also to the constantly varying
airspeed. The maneuver helps develop subconscious
feel, planning, orientation, coordination, and speed
sense. It is not possible to do a lazy eight mechanically,
because the control pressures required for perfect
coordination are never exactly the same.
This maneuver derives its name from the manner in
which the extended longitudinal axis of the airplane is
made to trace a flight pattern in the form of a figure 8
lying on its side (a lazy 8).
A lazy eight consists of two 180° turns, in opposite
directions, while making a climb and a descent in a
symmetrical pattern during each of the turns. At no
time throughout the lazy eight is the airplane flown
straight and level; instead, it is rolled directly from one
bank to the other with the wings level only at the
moment the turn is reversed at the completion of each
180° change in heading.
As an aid to making symmetrical loops of the 8 during
each turn, prominent reference points should be
selected on the horizon. The reference points selected
should be 45°, 90°, and 135° from the direction in
which the maneuver is begun.
Prior to performing a lazy eight, the airspace behind
and above should be clear of other air traffic. The
maneuver should be entered from straight-and-level
flight at normal cruise power and at the airspeed
recommended by the manufacturer or at the airplane’s
design maneuvering speed.
The maneuver is started from level flight with a
gradual climbing turn in the direction of the 45°
reference point. The climbing turn should be planned
and controlled so that the maximum pitch-up attitude
is reached at the 45° point. The rate of rolling into the
bank must be such as to prevent the rate of turn from
becoming too rapid. As the pitch attitude is raised, the
airspeed decreases, causing the rate of turn to increase.
Since the bank also is being increased, it too causes
the rate of turn to increase. Unless the maneuver is
begun with a slow rate of roll, the combination of
increasing pitch and increasing bank will cause the
rate of turn to be so rapid that the 45° reference point
will be reached before the highest pitch attitude
is attained.
At the 45° point, the pitch attitude should be at
maximum and the angle of bank continuing to
Figure 9-4. Lazy eight.
Ch 09.qxd 5/7/04 8:14 AM Page 9-6
9-7
increase. Also, at the 45° point, the pitch attitude
should start to decrease slowly toward the horizon and
the 90° reference point. Since the airspeed is still
decreasing, right-rudder pressure will have to be
applied to counteract torque.
As the airplane’s nose is being lowered toward the 90°
reference point, the bank should continue to increase.
Due to the decreasing airspeed, a slight amount of
opposite aileron pressure may be required to prevent
the bank from becoming too steep. When the airplane
completes 90° of the turn, the bank should be at the
maximum angle (approximately 30°), the airspeed
should be at its minimum (5 to 10 knots above stall
speed), and the airplane pitch attitude should be
passing through level flight. It is at this time that an
imaginary line, extending from the pilot’s eye and
parallel to the longitudinal axis of the airplane, passes
through the 90° reference point.
Lazy eights normally should be performed with no
more than approximately a 30° bank. Steeper banks
may be used, but control touch and technique must be
developed to a much higher degree than when the
maneuver is performed with a shallower bank.
The pilot should not hesitate at this point but should
continue to fly the airplane into a descending turn so
that the airplane’s nose describes the same size loop
below the horizon as it did above. As the pilot’s
reference line passes through the 90° point, the bank
should be decreased gradually, and the airplane’s nose
allowed to continue lowering. When the airplane has
turned 135°, the nose should be in its lowest pitch
attitude. The airspeed will be increasing during this
descending turn, so it will be necessary to gradually
relax rudder and aileron pressure and to
simultaneously raise the nose and roll the wings level.
As this is being accomplished, the pilot should note the
amount of turn remaining and adjust the rate of rollout
and pitch change so that the wings become level and
the original airspeed is attained in level flight just as
the 180° point is reached. Upon returning to the
starting altitude and the 180° point, a climbing turn
should be started immediately in the opposite direction
toward the selected reference points to complete the
second half of the eight in the same manner as the first
half.
Due to the decreasing airspeed, considerable rightrudder
pressure is gradually applied to counteract
torque at the top of the eight in both the right and left
turns. The pressure will be greatest at the point of
lowest airspeed.
More right-rudder pressure will be needed during the
climbing turn to the right than in the turn to the left
because more torque correction is needed to prevent
yaw from decreasing the rate of turn. In the left
climbing turn, the torque will tend to contribute to the
90° POINT
1. BANK APPROX 30°
2. MINIMUM SPEED
3. MAXIMUM ALTITUDE
4. LEVEL PITCH ATTITUDE
135° POINT
1. MAX. PITCH-DOWN
2. BANK 15°(APPROX.)
45° POINT
1. MAX. PITCH-UP
ATTITUDE
2. BANK 15°
(APPROX.)
ENTRY:
1. LEVEL FLIGHT
2. MANEUVERING OR CRUISE
SPEED WHICHEVER IS LESS
OR MANUFACTURER'S
RECOMMENDED SPEED.
180° POINT
1. LEVEL FLIGHT
2. ENTRY AIRSPEED
3. ALTITUDE SAME AS
ENTRY ALTITUDE
Figure 9-5. Lazy eight.
Ch 09.qxd 5/7/04 8:14 AM Page 9-7
9-8
turn; consequently, less rudder pressure is needed. It
will be noted that the controls are slightly crossed in
the right climbing turn because of the need for left
aileron pressure to prevent overbanking and right
rudder to overcome torque.
The correct power setting for the lazy eight is that
which will maintain the altitude for the maximum and
minimum airspeeds used during the climbs and
descents of the eight. Obviously, if excess power were
used, the airplane would have gained altitude when the
maneuver is completed; if insufficient power were
used, altitude would have been lost.
Common errors in the performance of lazy eights are:
• Failure to adequately clear the area.
• Using the nose, or top of engine cowl, instead of
the true longitudinal axis, resulting in
unsymmetrical loops.
• Watching the airplane instead of the
reference points.
• Inadequate planning, resulting in the peaks of the
loops both above and below the horizon not
coming in the proper place.
• Control roughness, usually caused by attempts
to counteract poor planning.
• Persistent gain or loss of altitude with the
completion of each eight.
• Attempting to perform the maneuver
rhythmically, resulting in poor pattern
symmetry.
• Allowing the airplane to “fall” out of the tops of
the loops rather than flying the airplane through
the maneuver.
• Slipping and/or skidding.
• Failure to scan for other traffic.
Ch 09.qxd 5/7/04 8:14 AM Page 9-8
NIGHT VISION
Generally, most pilots are poorly informed about night
vision. Human eyes never function as effectively at
night as the eyes of animals with nocturnal habits, but
if humans learn how to use their eyes correctly and
know their limitations, night vision can be improved
significantly. There are several reasons for training to
use the eyes correctly.
One reason is the mind and eyes act as a team for a person
to see well; both team members must be used
effectively. The construction of the eyes is such that to
see at night they are used differently than during the
day. Therefore, it is important to understand the eye’s
construction and how the eye is affected by darkness.
Innumerable light-sensitive nerves, called “cones” and
“rods,” are located at the back of the eye or retina, a
layer upon which all images are focused. These nerves
connect to the cells of the optic nerve, which transmits
messages directly to the brain. The cones are located in
the center of the retina, and the rods are concentrated
in a ring around the cones.
The function of the cones is to detect color, details, and
faraway objects. The rods function when something is
seen out of the corner of the eye or peripheral vision.
They detect objects, particularly those that are moving,
but do not give detail or color—only shades of gray.
Both the cones and the rods are used for vision during
daylight.
Although there is not a clear-cut division of function,
the rods make night vision possible. The rods and
cones function in daylight and in moonlight, but in the
absence of normal light, the process of night vision is
placed almost entirely on the rods.
The fact that the rods are distributed in a band around
the cones and do not lie directly behind the pupils
makes off-center viewing (looking to one side of an
object) important during night flight. During daylight,
an object can be seen best by looking directly at it, but
at night a scanning procedure to permit off-center
viewing of the object is more effective. Therefore, the
pilot should consciously practice this scanning procedure
to improve night vision.
The eye’s adaptation to darkness is another important
aspect of night vision. When a dark room is entered, it
is difficult to see anything until the eyes become
adjusted to the darkness. Most everyone has experienced
this after entering a darkened movie theater. In
this process, the pupils of the eyes first enlarge to
receive as much of the available light as possible. After
approximately 5 to 10 minutes, the cones become
adjusted to the dim light and the eyes become 100
Cones for:
• Color
• Detail
• Day
Rods for:
• Gray
• Peripheral
• Day & Night
Area of Best
Day Vision
Area of Best
Night Vision
Area of Best
Night Vision
Figure 10-1. Rods and cones.
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Ch 10.qxd 7/13/04 11:10 AM Page 10-1
times more sensitive to the light than they were before
the dark room was entered. Much more time, about 30
minutes, is needed for the rods to become adjusted to
darkness, but when they do adjust, they are about
100,000 times more sensitive to light than they were in
the lighted area. After the adaptation process is complete,
much more can be seen, especially if the eyes are
used correctly.
After the eyes have adapted to the dark, the entire
process is reversed when entering a lighted room. The
eyes are first dazzled by the brightness, but become
completely adjusted in a very few seconds, thereby losing
their adaptation to the dark. Now, if the dark room
is reentered, the eyes again go through the long process
of adapting to the darkness.
The pilot before and during night flight must consider
the adaptation process of the eyes. First, the eyes
should be allowed to adapt to the low level of light
and then they should be kept adapted. After the eyes
have become adapted to the darkness, the pilot should
avoid exposing them to any bright white light that
will cause temporary blindness and could result in
serious consequences.
Temporary blindness, caused by an unusually bright
light, may result in illusions or after images until the
eyes recover from the brightness. The brain creates
these illusions reported by the eyes. This results in
misjudging or incorrectly identifying objects, such as
mistaking slanted clouds for the horizon or populated
areas for a landing field. Vertigo is experienced as a
feeling of dizziness and imbalance that can create or
increase illusions. The illusions seem very real and
pilots at every level of experience and skill can be
affected. Recognizing that the brain and eyes can play
tricks in this manner is the best protection for flying at
night.
Good eyesight depends upon physical condition.
Fatigue, colds, vitamin deficiency, alcohol, stimulants,
smoking, or medication can seriously impair vision.
Keeping these facts in mind and taking adequate precautions
should safeguard night vision.
In addition to the principles previously discussed, the
following items will aid in increasing night vision
effectiveness.
• Adapt the eyes to darkness prior to flight and
keep them adapted. About 30 minutes is needed
to adjust the eyes to maximum efficiency after
exposure to a bright light.
• If oxygen is available, use it during night flying.
Keep in mind that a significant deterioration in
night vision can occur at cabin altitudes as low as
5,000 feet.
• Close one eye when exposed to bright light to
help avoid the blinding effect.
• Do not wear sunglasses after sunset.
• Move the eyes more slowly than in daylight.
• Blink the eyes if they become blurred.
• Concentrate on seeing objects.
• Force the eyes to view off center.
• Maintain good physical condition.
• Avoid smoking, drinking, and using drugs that
may be harmful.
NIGHT ILLUSIONS
In addition to night vision limitations, pilots should be
aware that night illusions could cause confusion and
concerns during night flying. The following discussion
covers some of the common situations that cause
illusions associated with night flying.
On a clear night, distant stationary lights can be mistaken
for stars or other aircraft. Even the northern
lights can confuse a pilot and indicate a false horizon.
Certain geometrical patterns of ground lights, such as
a freeway, runway, approach, or even lights on a moving
train can cause confusion. Dark nights tend to
eliminate reference to a visual horizon. As a result,
pilots need to rely less on outside references at night
and more on flight and navigation instruments.
Visual autokinesis can occur when a pilot stares at a
single light source for several seconds on a dark night.
The result is that the light will appear to be moving.
The autokinesis effect will not occur if the pilot
expands the visual field. It is a good procedure not to
become fixed on one source of light.
Distractions and problems can result from a flickering
light in the cockpit, anticollision light, strobe lights,
or other aircraft lights and can cause flicker vertigo. If
continuous, the possible physical reactions can be
nausea, dizziness, grogginess, unconsciousness,
headaches, or confusion. The pilot should try to eliminate
any light source causing blinking or flickering
problems in the cockpit.
A black-hole approach occurs when the landing is
made from over water or non-lighted terrain where the
runway lights are the only source of light. Without
peripheral visual cues to help, pilots will have trouble
orientating themselves relative to Earth. The runway
can seem out of position (downsloping or upsloping)
and in the worse case, results in landing short of the
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Ch 10.qxd 7/13/04 11:10 AM Page 10-2
runway. If an electronic glide slope or visual approach
slope indicator (VASI) is available, it should be used.
If navigation aids (NAVAIDs) are unavailable, careful
attention should be given to using the flight instruments
to assist in maintaining orientation and a normal
approach. If at any time the pilot is unsure of his or her
position or attitude, a go-around should be executed.
Bright runway and approach lighting systems, especially
where few lights illuminate the surrounding
terrain, may create the illusion of less distance to the
runway. In this situation, the tendency is to fly a
higher approach. Also, when flying over terrain with
only a few lights, it will make the runway recede or
appear farther away. With this situation, the tendency
is common to fly a lower-than-normal approach. If
the runway has a city in the distance on higher terrain,
the tendency will be to fly a lower-than-normal
approach. A good review of the airfield layout and
boundaries before initiating any approach will help
the pilot maintain a safe approach angle.
Illusions created by runway lights result in a variety of
problems. Bright lights or bold colors advance the runway,
making it appear closer.
Night landings are further complicated by the difficulty
of judging distance and the possibility of confusing
approach and runway lights. For example, when a double
row of approach lights joins the boundary lights of
the runway, there can be confusion where the approach
lights terminate and runway lights begin. Under certain
conditions, approach lights can make the aircraft seem
higher in a turn to final, than when its wings are level.
PILOT EQUIPMENT
Before beginning a night flight, carefully consider
personal equipment that should be readily available
during the flight. At least one reliable flashlight is
recommended as standard equipment on all night
flights. Remember to place a spare set of batteries in
the flight kit. A D-cell size flashlight with a bulb
switching mechanism that can be used to select white
or red light is preferable. The white light is used while
performing the preflight visual inspection of the airplane,
and the red light is used when performing cockpit operations.
Since the red light is nonglaring, it will not impair
night vision. Some pilots prefer two flashlights, one
with a white light for preflight, and the other a penlight
type with a red light. The latter can be suspended
by a string from around the neck to ensure the light is
always readily available. One word of caution; if a red
light is used for reading an aeronautical chart, the red
features of the chart will not show up.
Aeronautical charts are essential for night cross-country
flight and, if the intended course is near the edge of
the chart, the adjacent chart should also be available.
The lights of cities and towns can be seen at surprising
distances at night, and if this adjacent chart is not available
to identify those landmarks, confusion could
result. Regardless of the equipment used, organization
of the cockpit eases the burden on the pilot and
enhances safety.
AIRPLANE EQUIPMENT
AND LIGHTING
Title 14 of the Code of Federal Regulations (14 CFR)
part 91 specifies the basic minimum airplane equipment
required for night flight. This equipment includes
only basic instruments, lights, electrical energy source,
and spare fuses.
The standard instruments required for instrument
flight under 14 CFR part 91 are a valuable asset for
aircraft control at night. An anticollision light system,
including a flashing or rotating beacon and position
lights, is required airplane equipment. Airplane position
lights are arranged similar to those of boats and
ships. A red light is positioned on the left wingtip, a
green light on the right wingtip, and a white light on
the tail.
Figure 10-2. Position lights.
This arrangement provides a means by which pilots
can determine the general direction of movement of
other airplanes in flight. If both a red and green light of
another aircraft were observed, the airplane would be
flying toward the pilot, and could be on a collision
course.
Landing lights are not only useful for taxi, takeoffs,
and landings, but also provide a means by which airplanes
can be seen at night by other pilots. The Federal
Aviation Administration (FAA) has initiated a voluntary
pilot safety program called “Operation Lights
ON.” The “lights on” idea is to enhance the “see and
be seen” concept of averting collisions both in the air
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Ch 10.qxd 7/13/04 11:10 AM Page 10-3
and on the ground, and to reduce the potential for bird
strikes. Pilots are encouraged to turn on their landing
lights when operating within 10 miles of an airport.
This is for both day and night, or in conditions of
reduced visibility. This should also be done in areas
where flocks of birds may be expected.
Although turning on aircraft lights supports the see and
be seen concept, pilots should not become complacent
about keeping a sharp lookout for other aircraft. Most
aircraft lights blend in with the stars or the lights of the
cities at night and go unnoticed unless a conscious
effort is made to distinguish them from other lights.
AIRPORT AND NAVIGATION
LIGHTING AIDS
The lighting systems used for airports, runways,
obstructions, and other visual aids at night are other
important aspects of night flying.
Lighted airports located away from congested areas
can be identified readily at night by the lights outlining
the runways. Airports located near or within large
cities are often difficult to identify in the maze of
lights. It is important not to only know the exact location
of an airport relative to the city, but also to be able
to identify these airports by the characteristics of their
lighting pattern.
Aeronautical lights are designed and installed in a variety
of colors and configurations, each having its own
purpose. Although some lights are used only during
low ceiling and visibility conditions, this discussion
includes only the lights that are fundamental to visual
flight rules (VFR) night operation.
It is recommended that prior to a night flight, and
particularly a cross-country night flight, the pilot check
the availability and status of lighting systems at the
destination airport. This information can be found on
aeronautical charts and in the Airport/Facility
Directory. The status of each facility can be determined
by reviewing pertinent Notices to Airmen
(NOTAMs).
A rotating beacon is used to indicate the location of
most airports. The beacon rotates at a constant speed,
thus producing what appears to be a series of light
flashes at regular intervals. These flashes may be one
or two different colors that are used to identify various
types of landing areas. For example:
• Lighted civilian land airports—alternating white
and green.
• Lighted civilian water airports—alternating
white and yellow.
• Lighted military airports—alternating white and
green, but are differentiated from civil airports
by dual peaked (two quick) white flashes, then
green.
Beacons producing red flashes indicate obstructions or
areas considered hazardous to aerial navigation.
Steady burning red lights are used to mark obstructions
on or near airports and sometimes to supplement
flashing lights on en route obstructions. High intensity
flashing white lights are used to mark some supporting
structures of overhead transmission lines that stretch
across rivers, chasms, and gorges. These high intensity
lights are also used to identify tall structures, such as
chimneys and towers.
As a result of the technological advancements in
aviation, runway lighting systems have become
quite sophisticated to accommodate takeoffs and
landings in various weather conditions. However,
the pilot whose flying is limited to VFR only needs
to be concerned with the following basic lighting of
runways and taxiways.
The basic runway lighting system consists of two
straight parallel lines of runway-edge lights defining
the lateral limits of the runway. These lights are
aviation white, although aviation yellow may be
substituted for a distance of 2,000 feet from the far
end of the runway to indicate a caution zone. At
some airports, the intensity of the runway-edge
lights can be adjusted to satisfy the individual needs
of the pilot. The length limits of the runway are
defined by straight lines of lights across the runway
ends. At some airports, the runway threshold lights
are aviation green, and the runway end lights are
aviation red.
At many airports, the taxiways are also lighted. Ataxiway-
edge lighting system consists of blue lights that
outline the usable limits of taxi paths.
PREPARATION AND PREFLIGHT
Night flying requires that pilots be aware of, and operate
within, their abilities and limitations. Although
careful planning of any flight is essential, night flying
demands more attention to the details of preflight
preparation and planning.
Preparation for a night flight should include a thorough
review of the available weather reports and forecasts
with particular attention given to temperature/dewpoint
spread. A narrow temperature/dewpoint spread may
indicate the possibility of ground fog. Emphasis
should also be placed on wind direction and speed,
since its effect on the airplane cannot be as easily
detected at night as during the day.
On night cross-country flights, appropriate aeronautical
charts should be selected, including the
10-4
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appropriate adjacent charts. Course lines should be
drawn in black to be more distinguishable.
Prominently lighted checkpoints along the prepared
course should be noted. Rotating beacons at airports,
lighted obstructions, lights of cities or towns, and
lights from major highway traffic all provide excellent
visual checkpoints. The use of radio navigation aids
and communication facilities add significantly to the
safety and efficiency of night flying.
All personal equipment should be checked prior to
flight to ensure proper functioning. It is very disconcerting
to find, at the time of need, that a flashlight, for
example, does not work.
All airplane lights should be turned ON momentarily
and checked for operation. Position lights can be
checked for loose connections by tapping the light fixture.
If the lights blink while being tapped, further
investigation to determine the cause should be made
prior to flight.
The parking ramp should be examined prior to entering
the airplane. During the day, it is quite easy to see
stepladders, chuckholes, wheel chocks, and other
obstructions, but at night it is more difficult. A check
of the area can prevent taxiing mishaps.
STARTING,TAXIING, AND RUNUP
After the pilot is seated in the cockpit and prior to starting
the engine, all items and materials to be used on the
flight should be arranged in such a manner that they
will be readily available and convenient to use.
Extra caution should be taken at night to assure the
propeller area is clear. Turning the rotating beacon ON,
or flashing the airplane position lights will serve to
alert persons nearby to remain clear of the propeller.
To avoid excessive drain of electrical current from the
battery, it is recommended that unnecessary electrical
equipment be turned OFF until after the engine has
been started.
After starting and before taxiing, the taxi or landing
light should be turned ON. Continuous use of the landing
light with r.p.m. power settings normally used for
taxiing may place an excessive drain on the airplane’s
electrical system. Also, overheating of the landing light
could become a problem because of inadequate airflow
to carry the heat away. Landing lights should be used
as necessary while taxiing. When using landing lights,
consideration should be given to not blinding other
pilots. Taxi slowly, particularly in congested areas. If
taxi lines are painted on the ramp or taxiway, these
lines should be followed to ensure a proper path along
the route.
The before takeoff and runup should be performed
using the checklist. During the day, forward movement
of the airplane can be detected easily. At night, the
airplane could creep forward without being noticed
unless the pilot is alert for this possibility. Hold or
lock the brakes during the runup and be alert for any
forward movement.
TAKEOFF AND CLIMB
Night flying is very different from day flying and
demands more attention of the pilot. The most noticeable
difference is the limited availability of outside
visual references. Therefore, flight instruments should
be used to a greater degree in controlling the airplane.
This is particularly true on night takeoffs and climbs.
The cockpit lights should be adjusted to a minimum
brightness that will allow the pilot to read the instruments
and switches and yet not hinder the pilot’s outside
vision. This will also eliminate light reflections on
the windshield and windows.
After ensuring that the final approach and runway are
clear of other air traffic, or when cleared for takeoff by
the tower, the landing lights and taxi lights should be
turned ON and the airplane lined up with the centerline
of the runway. If the runway does not have centerline
lighting, use the painted centerline and the runwayedge
lights. After the airplane is aligned, the heading
indicator should be noted or set to correspond to the
known runway direction. To begin the takeoff, the
brakes should be released and the throttle smoothly
advanced to maximum allowable power. As the airplane
accelerates, it should be kept moving straight
ahead between and parallel to the runway-edge lights.
The procedure for night takeoffs is the same as for normal
daytime takeoffs except that many of the runway
visual cues are not available. Therefore, the flight
instruments should be checked frequently during the
takeoff to ensure the proper pitch attitude, heading, and
airspeed are being attained. As the airspeed reaches the
normal lift-off speed, the pitch attitude should be
adjusted to that which will establish a normal climb.
This should be accomplished by referring to both outside
visual references, such as lights, and to the flight
instruments.
Figure 10-3. Establish a positive climb.
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10-6
After becoming airborne, the darkness of night often
makes it difficult to note whether the airplane is getting
closer to or farther from the surface. To ensure the
airplane continues in a positive climb, be sure a climb
is indicated on the attitude indicator, vertical speed
indicator (VSI), and altimeter. It is also important to
ensure the airspeed is at best climb speed.
Necessary pitch and bank adjustments should be made
by referencing the attitude and heading indicators. It is
recommended that turns not be made until reaching a
safe maneuvering altitude.
Although the use of the landing lights provides help
during the takeoff, they become ineffective after the
airplane has climbed to an altitude where the light
beam no longer extends to the surface. The light can
cause distortion when it is reflected by haze, smoke, or
fog that might exist in the climb. Therefore, when the
landing light is used for the takeoff, it may be turned
off after the climb is well established provided other
traffic in the area does not require its use for collision
avoidance.
ORIENTATION AND NAVIGATION
Generally, at night it is difficult to see clouds and
restrictions to visibility, particularly on dark nights or
under overcast. The pilot flying under VFR must exercise
caution to avoid flying into clouds or a layer of
fog. Usually, the first indication of flying into restricted
visibility conditions is the gradual disappearance of
lights on the ground. If the lights begin to take on an
appearance of being surrounded by a halo or glow, the
pilot should use caution in attempting further flight in
that same direction. Such a halo or glow around lights
on the ground is indicative of ground fog. Remember
that if a descent must be made through fog, smoke, or
haze in order to land, the horizontal visibility is considerably
less when looking through the restriction than it
is when looking straight down through it from above.
Under no circumstances should a VFR night-flight be
made during poor or marginal weather conditions
unless both the pilot and aircraft are certificated and
equipped for flight under instrument flight rules (IFR).
The pilot should practice and acquire competency in
straight-and-level flight, climbs and descents, level
turns, climbing and descending turns, and steep turns.
Recovery from unusual attitudes should also be practiced,
but only on dual flights with a flight instructor.
The pilot should also practice these maneuvers with all
the cockpit lights turned OFF. This blackout training is
necessary if the pilot experiences an electrical or
instrument light failure. Training should also include
using the navigation equipment and local NAVAIDs.
In spite of fewer references or checkpoints, night crosscountry
flights do not present particular problems if
preplanning is adequate, and the pilot continues to
monitor position, time estimates, and fuel consumed.
NAVAIDs, if available, should be used to assist in
monitoring en route progress.
Crossing large bodies of water at night in singleengine
airplanes could be potentially hazardous, not
only from the standpoint of landing (ditching) in the
water, but also because with little or no lighting the
horizon blends with the water, in which case, depth
perception and orientation become difficult. During
poor visibility conditions over water, the horizon will
become obscure, and may result in a loss of orientation.
Even on clear nights, the stars may be reflected
on the water surface, which could appear as a continuous
array of lights, thus making the horizon difficult
to identify.
Lighted runways, buildings, or other objects may
cause illusions to the pilot when seen from different
altitudes. At an altitude of 2,000 feet, a group of lights
on an object may be seen individually, while at 5,000
feet or higher, the same lights could appear to be one
solid light mass. These illusions may become quite
acute with altitude changes and if not overcome could
present problems in respect to approaches to lighted
runways.
APPROACHES AND LANDINGS
When approaching the airport to enter the traffic pattern
and land, it is important that the runway lights
and other airport lighting be identified as early as
possible. If the airport layout is unfamiliar to the
pilot, sighting of the runway may be difficult until
very close-in due to the maze of lights observed in
the area. The pilot should fly toward
the rotating beacon until the lights outlining the runway
are distinguishable. To fly a traffic pattern of
proper size and direction, the runway threshold and
runway-edge lights must be positively identified.
Once the airport lights are seen, these lights should
be kept in sight throughout the approach.
Figure 10-4. Use light patterns for orientation.
Ch 10.qxd 7/13/04 11:10 AM Page 10-6
Distance may be deceptive
at night due to limited
lighting conditions. A lack
of intervening references
on the ground and the
inability of the pilot to compare
the size and location of
different ground objects
cause this. This also applies
to the estimation of altitude
and speed. Consequently,
more dependence must be
placed on flight instruments,
particularly the altimeter and
the airspeed indicator.
When entering the traffic
pattern, allow for plenty of
time to complete the
before landing checklist. If
the heading indicator contains a heading bug, setting it
to the runway heading will be an excellent reference
for the pattern legs.
Every effort should be made to maintain the recommended
airspeeds and execute the approach and
landing in the same manner as during the day. A low,
shallow approach is definitely inappropriate during
a night operation. The altimeter and VSI should be
constantly cross-checked against the airplane’s position
along the base leg and final approach. A visual
approach slope indicator (VASI) is an indispensable aid
in establishing and maintaining a proper glidepath.
After turning onto the final approach and aligning the
airplane midway between the two rows of runway-edge
lights, the pilot should note and correct for any wind
drift. Throughout the final approach, pitch and power
should be used to maintain a stabilized approach. Flaps
should be used the same as in a normal approach.
Usually, halfway through the final approach, the landing
light should be turned on. Earlier use of the landing
light may be necessary because of “Operation Lights
ON” or for local traffic considerations. The landing
light is sometimes ineffective since the light beam will
usually not reach the ground from higher altitudes. The
light may even be reflected back into the pilot’s eyes
by any existing haze, smoke, or fog. This disadvantage
is overshadowed by the safety considerations provided
by using the “Operation Lights ON” procedure around
other traffic.
The roundout and touchdown should be made in the
same manner as in day landings. At night, the judgment
of height, speed, and sink rate is impaired by the
scarcity of observable objects in the landing area. The
inexperienced pilot may have a tendency to round out
too high until attaining familiarity with the proper
height for the correct roundout. To aid in determining
the proper roundout point, continue a constant
approach descent until the landing lights reflect on the
runway and tire marks on the runway can be seen
clearly. At this point the roundout should be started
smoothly and the throttle gradually reduced to idle
as the airplane is touching down.
During landings without the use of landing lights, the
roundout may be started when the runway lights at the
If both light bars are white,
you are too high.
If you see red over red, you
are below the glidepath.
Above Glidepath Below Glidepath On Glidepath
If the far bar is red and the
near bar is white, you are on
the glidepath. The memory
aid "red over white, you're all
right," is helpful in recalling
the correct sequence of lights.
Figure 10-5.VASI.
Figure 10-6. Roundout when tire marks are visible.
10-7
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10-8
far end of the runway first appear to be rising higher
than the nose of the airplane. This demands a smooth
and very timely roundout, and requires that the pilot
feel for the runway surface using power and pitch
changes, as necessary, for the airplane to settle slowly
to the runway. Blackout landings should always be
included in night pilot training as an emergency
procedure.
NIGHT EMERGENCIES
Perhaps the pilot’s greatest concern about flying a singleengine
airplane at night is the possibility of a complete
engine failure and the subsequent emergency landing.
This is a legitimate concern, even though continuing
flight into adverse weather and poor pilot judgment
account for most serious accidents.
If the engine fails at night, several important procedures
and considerations to keep in mind are:
• Maintain positive control of the airplane and
establish the best glide configuration and airspeed.
Turn the airplane towards an airport or away from
congested areas.
• Check to determine the cause of the engine
malfunction, such as the position of fuel selectors,
magneto switch, or primer. If possible, the
cause of the malfunction should be corrected
immediately and the engine restarted.
• Announce the emergency situation to Air Traffic
Control (ATC) or UNICOM. If already in radio
contact with a facility, do not change frequencies,
unless instructed to change.
• If the condition of the nearby terrain is known,
turn towards an unlighted portion of the area.
Plan an emergency approach to an unlighted
portion.
• Consider an emergency landing area close to
public access if possible. This may facilitate
rescue or help, if needed.
• Maintain orientation with the wind to avoid a
downwind landing.
• Complete the before landing checklist, and
check the landing lights for operation at altitude
and turn ON in sufficient time to illuminate the
terrain or obstacles along the flightpath. The
landing should be completed in the normal landing
attitude at the slowest possible airspeed. If
the landing lights are unusable and outside visual
references are not available, the airplane should
be held in level-landing attitude until the ground
is contacted.
• After landing, turn off all switches and evacuate
the airplane as quickly as possible.
Ch 10.qxd 7/13/04 11:10 AM Page 10-8
11-1
HIGH PERFORMANCE AND COMPLEX
AIRPLANES
Transition to a complex airplane, or a high performance
airplane, can be demanding for most pilots without previous
experience. Increased performance and increased
complexity both require additional planning, judgment,
and piloting skills. Transition to these types of
airplanes, therefore, should be accomplished in a
systematic manner through a structured course of
training administered by a qualified flight instructor.
A complex airplane is defined as an airplane equipped
with a retractable landing gear, wing flaps, and a
controllable-pitch propeller. For a seaplane to be
considered complex, it is required to have wing flaps and
a controllable-pitch propeller. A high performance
airplane is defined as an airplane with an engine of more
than 200 horsepower.
WING FLAPS
Airplanes can be designed to fly fast or slow. High
speed requires thin, moderately cambered airfoils with
a small wing area, whereas the high lift needed for low
speeds is obtained with thicker highly cambered
airfoils with a larger wing area. Many
attempts have been made to compromise this
conflicting requirement of high cruise and slow
landing speeds.
Since an airfoil cannot have two different cambers at
the same time, one of two things must be done. Either
the airfoil can be a compromise, or a cruise airfoil can
be combined with a device for increasing the camber of
the airfoil for low-speed flight. One method for varying
an airfoil’s camber is the addition of trailing edge flaps.
Engineers call these devices a high-lift system.
FUNCTION OF FLAPS
Flaps work primarily by changing the camber of the
airfoil since deflection adds aft camber. Flap deflection
does not increase the critical (stall) angle of attack, and
in some cases flap deflection actually decreases the
critical angle of attack.
Deflection of trailing edge control surfaces, such as the
aileron, alters both lift and drag. With aileron
deflection, there is asymmetrical lift (rolling moment)
and drag (adverse yaw). Wing flaps differ in that
deflection acts symmetrically on the airplane. There is
no roll or yaw effect, and pitch changes depend on the
airplane design.
Straight
Elliptical
Tapered
Sweptback
Delta
Figure 11-1. Airfoil types.
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11-2
Pitch behavior depends on flap type, wing position,
and horizontal tail location. The increased camber
from flap deflection produces lift primarily on the rear
portion of the wing. This produces a nosedown
pitching moment; however, the change in tail load
from the downwash deflected by the flaps over the
horizontal tail has a significant influence on the
pitching moment. Consequently, pitch behavior
depends on the design features of the particular airplane.
Flap deflection of up to 15° primarily produces lift
with minimal drag. The tendency to balloon up with
initial flap deflection is because of lift increase, but the
nosedown pitching moment tends to offset the balloon.
Deflection beyond 15° produces a large increase in
drag. Drag from flap deflection is parasite drag, and
as such is proportional to the square of the speed. Also,
deflection beyond 15° produces a significant noseup
pitching moment in most high-wing airplanes because
the resulting downwash increases the airflow over the
horizontal tail.
FLAP EFFECTIVENESS
Flap effectiveness depends on a number of factors, but
the most noticeable are size and type. For the purpose
of this chapter, trailing edge flaps are classified as four
basic types: plain (hinge), split, slotted, and Fowler.
The plain or hinge flap is a hinged section of the wing.
The structure and function are comparable to the other
control surfaces—ailerons, rudder, and elevator. The
split flap is more complex. It is the lower or underside
portion of the wing; deflection of the flap leaves the
trailing edge of the wing undisturbed. It is, however,
more effective than the hinge flap because of greater
lift and less pitching moment, but there is more drag.
Split flaps are more useful for landing, but the partially
deflected hinge flaps have the advantage in takeoff.
The split flap has significant drag at small deflections,
whereas the hinge flap does not because airflow
remains “attached” to the flap.
The slotted flap has a gap between the wing and the
leading edge of the flap. The slot allows high
pressure airflow on the wing undersurface to energize
the lower pressure over the top, thereby delaying flow
separation. The slotted flap has greater lift than the
hinge flap but less than the split flap; but, because of
a higher lift-drag ratio, it gives better takeoff and
climb performance. Small deflections of the slotted
flap give a higher drag than the hinge flap but less
than the split. This allows the slotted flap to be used
for takeoff.
The Fowler flap deflects down and aft to increase the
wing area. This flap can be multi-slotted making it the
most complex of the trailing edge systems. This
system does, however, give the maximum lift
coefficient. Drag characteristics at small deflections
are much like the slotted flap. Because of structural
complexity and difficulty in sealing the slots, Fowler
flaps are most commonly used on larger airplanes.
OPERATIONAL PROCEDURES
It would be impossible to discuss all the many airplane
design and flap combinations. This emphasizes the
importance of the FAA-approved Airplane Flight
Manual and/or Pilot’s Operating Handbook
(AFM/POH) for a given airplane. However, while
some AFM/POHs are specific as to operational use of
flaps, many are lacking. Hence, flap operation makes
pilot judgment of critical importance. In addition, flap
operation is used for landings and takeoffs, during
which the airplane is in close proximity to the ground
where the margin for error is small.
Since the recommendations given in the AFM/POH are
based on the airplane and the flap design combination,
Plain Flap
Split Flap
Slotted Flap
Fowler Flap
Figure 11-2. Four basic types of flaps.
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11-3
the pilot must relate the manufacturer’s recommendation
to aerodynamic effects of flaps. This requires that
the pilot have a basic background knowledge of flap
aerodynamics and geometry. With this information, the
pilot must make a decision as to the degree of flap
deflection and time of deflection based on runway and
approach conditions relative to the wind conditions.
The time of flap extension and degree of deflection are
related. Large flap deflections at one single point in the
landing pattern produce large lift changes that require
significant pitch and power changes in order to
maintain airspeed and glide slope. Incremental
deflection of flaps on downwind, base, and final
approach allow smaller adjustment of pitch and power
compared to extension of full flaps all at one time. This
procedure facilitates a more stabilized approach.
Asoft- or short-field landing requires minimal speed at
touchdown. The flap deflection that results in minimal
groundspeed, therefore, should be used. If obstacle
clearance is a factor, the flap deflection that results in
the steepest angle of approach should be used. It
should be noted, however, that the flap setting that
gives the minimal speed at touchdown does not
necessarily give the steepest angle of approach;
however, maximum flap extension gives the steepest
angle of approach and minimum speed at touchdown.
Maximum flap extension, particularly beyond 30 to
35°, results in a large amount of drag. This requires
higher power settings than used with partial flaps.
Because of the steep approach angle combined with
power to offset drag, the flare with full flaps becomes
critical. The drag produces a high sink rate that must
be controlled with power, yet failure to reduce power
at a rate so that the power is idle at touchdown allows
the airplane to float down the runway. A reduction in
power too early results in a hard landing.
Crosswind component is another factor to be
considered in the degree of flap extension. The
deflected flap presents a surface area for the wind to
act on. In a crosswind, the “flapped” wing on the
upwind side is more affected than the downwind
wing. This is, however, eliminated to a slight extent
in the crabbed approach since the airplane is more
nearly aligned with the wind. When using a wing low
approach, however, the lowered wing partially
blankets the upwind flap, but the dihedral of the wing
combined with the flap and wind make lateral control
more difficult. Lateral control becomes more difficult
as flap extension reaches maximum and the
crosswind becomes perpendicular to the runway.
Crosswind effects on the “flapped” wing become more
pronounced as the airplane comes closer to the ground.
The wing, flap, and ground form a “container” that is
filled with air by the crosswind. With the wind striking
the deflected flap and fuselage side and with the flap
located behind the main gear, the upwind wing will
tend to rise and the airplane will tend to turn into the
wind. Proper control position, therefore, is essential
for maintaining runway alignment. Also, it may
be necessary to retract the flaps upon positive
ground contact.
The go-around is another factor to consider when
making a decision about degree of flap deflection
and about where in the landing pattern to extend
flaps. Because of the nosedown pitching moment
produced with flap extension, trim is used to offset
this pitching moment. Application of full power in
the go-around increases the airflow over the
“flapped” wing. This produces additional lift
causing the nose to pitch up. The pitch-up tendency
does not diminish completely with flap retraction
because of the trim setting. Expedient retraction of
flaps is desirable to eliminate drag, thereby allowing
rapid increase in airspeed; however, flap retraction
also decreases lift so that the airplane sinks rapidly.
The degree of flap deflection combined with design
configuration of the horizontal tail relative to the
wing requires that the pilot carefully monitor pitch
and airspeed, carefully control flap retraction to
minimize altitude loss, and properly use the rudder
for coordination. Considering these factors, the pilot
should extend the same degree of deflection at the
same point in the landing pattern. This requires that a
consistent traffic pattern be used. Therefore, the pilot
can have a preplanned go-around sequence based on
the airplane’s position in the landing pattern.
There is no single formula to determine the degree of
flap deflection to be used on landing, because a
landing involves variables that are dependent on each
other. The AFM/POH for the particular airplane will
contain the manufacturer’s recommendations for
some landing situations. On the other hand,
AFM/POH information on flap usage for takeoff is
more precise. The manufacturer’s requirements are
based on the climb performance produced by a given
flap design. Under no circumstances should a flap
setting given in the AFM/POH be exceeded
for takeoff.
CONTROLLABLE-PITCH PROPELLER
Fixed-pitch propellers are designed for best efficiency
at one speed of rotation and forward speed. This type
of propeller will provide suitable performance in
a narrow range of airspeeds; however, efficiency
would suffer considerably outside this range. To
provide high propeller efficiency through a wide
range of operation, the propeller blade angle
must be controllable. The most convenient
Ch 11.qxd 5/7/04 8:50 AM Page 11-3
11-4
way of controlling the propeller blade angle is by
means of a constant-speed governing system.
CONSTANT-SPEED PROPELLER
The constant-speed propeller keeps the blade angle
adjusted for maximum efficiency for most conditions
of flight. When an engine is running at constant
speed, the torque (power) exerted by the engine at the
propeller shaft must equal the opposing load provided
by the resistance of the air. The r.p.m. is controlled by
regulating the torque absorbed by the propeller—in
other words by increasing or decreasing the
resistance offered by the air to the propeller. In the
case of a fixed-pitch propeller, the torque absorbed
by the propeller is a function of speed, or r.p.m. If the
power output of the engine is changed, the engine will
accelerate or decelerate until an r.p.m. is reached at
which the power delivered is equal to the power
absorbed. In the case of a constant-speed propeller,
the power absorbed is independent of the r.p.m., for
by varying the pitch of the blades, the air resistance
and hence the torque or load, can be changed without
reference to propeller speed. This is accomplished
with a constant-speed propeller by means of a
governor. The governor, in most cases, is geared to
the engine crankshaft and thus is sensitive to changes
in engine r.p.m.
The pilot controls the engine r.p.m. indirectly by means
of a propeller control in the cockpit, which is
connected to the governor. For maximum takeoff
power, the propeller control is moved all the way
forward to the low pitch/high r.p.m. position, and the
throttle is moved forward to the maximum allowable
manifold pressure position. To reduce power for climb
or cruise, manifold pressure is reduced to the desired
value with the throttle, and the engine r.p.m. is reduced
by moving the propeller control back toward the high
pitch/low r.p.m. position until the desired r.p.m. is
observed on the tachometer. Pulling back on the
propeller control causes the propeller blades to move
to a higher angle. Increasing the propeller blade angle
(of attack) results in an increase in the resistance of the
air. This puts a load on the engine so it slows down. In
other words, the resistance of the air at the higher blade
angle is greater than the torque, or power, delivered to
the propeller by the engine, so it slows down to a point
where the two forces are in balance.
When an airplane is nosed up into a climb from level
flight, the engine will tend to slow down. Since the
governor is sensitive to small changes in engine r.p.m.,
it will decrease the blade angle just enough to keep the
engine speed from falling off. If the airplane is nosed
down into a dive, the governor will increase the blade
angle enough to prevent the engine from overspeeding.
This allows the engine to maintain a constant r.p.m.,
and thus maintain the power output. Changes in
airspeed and power can be obtained by changing
r.p.m. at a constant manifold pressure; by changing
the manifold pressure at a constant r.p.m.; or by
changing both r.p.m. and manifold pressure. Thus
the constant-speed propeller makes it possible to
obtain an infinite number of power settings.
TAKEOFF, CLIMB, AND CRUISE
During takeoff, when the forward motion of the
airplane is at low speeds and when maximum power
and thrust are required, the constant-speed propeller
sets up a low propeller blade angle (pitch). The low
blade angle keeps the angle of attack, with respect to
the relative wind, small and efficient at the low speed.
At the same time, it allows the propeller to “slice it
thin” and handle a smaller mass of air per revolution.
This light load allows the engine to turn at maximum
r.p.m. and develop maximum power. Although the
mass of air per revolution is small, the number of
revolutions per minute is high. Thrust is maximum at
the beginning of the takeoff and then decreases as the
airplane gains speed and the airplane drag increases.
Due to the high slipstream velocity during takeoff,
the effective lift of the wing behind the propeller(s)
is increased.
As the airspeed increases after lift-off, the load on the
engine is lightened because of the small blade angle.
The governor senses this and increases the blade angle
slightly. Again, the higher blade angle, with the higher
speeds, keeps the angle of attack with respect to the
relative wind small and efficient.
Angle of
Attack
Chord
Line
Plane of
Propeller
Rotation
Angle of
Attack
Chord Line
(Blade Face)
STATIONARY FORWARD MOTION
Plane of
Propeller
Rotation
Forward
Airspeed
Relative
Wind
Relative
Wind
Figure 11-3. Propeller blade angle.
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11-5
For climb after takeoff, the power output of the engine
is reduced to climb power by decreasing the manifold
pressure and lowering r.p.m. by increasing the blade
angle. At the higher (climb) airspeed and the higher
blade angle, the propeller is handling a greater mass of
air per second at a lower slipstream velocity. This
reduction in power is offset by the increase in propeller
efficiency. The angle of attack is again kept small by
the increase in the blade angle with an increase
in airspeed.
At cruising altitude, when the airplane is in level flight,
less power is required to produce a higher airspeed
than is used in climb. Consequently, engine power is
again reduced by lowering the manifold pressure and
increasing the blade angle (to decrease r.p.m.). The
higher airspeed and higher blade angle enable the
propeller to handle a still greater mass of air per
second at still smaller slipstream velocity. At normal
cruising speeds, propeller efficiency is at, or near
maximum efficiency. Due to the increase in blade
angle and airspeed, the angle of attack is still small
and efficient.
BLADE ANGLE CONTROL
Once the pilot selects the r.p.m. settings for the
propeller, the propeller governor automatically adjusts
the blade angle to maintain the selected r.p.m. It does
this by using oil pressure. Generally, the oil pressure
used for pitch change comes directly from the engine
lubricating system. When a governor is employed,
engine oil is used and the oil pressure is usually
boosted by a pump, which is integrated with the
governor. The higher pressure provides a quicker blade
angle change. The r.p.m. at which the propeller is to
operate is adjusted in the governor head. The pilot
changes this setting by changing the position of the
governor rack through the cockpit propeller control.
On some constant-speed propellers, changes in pitch
are obtained by the use of an inherent centrifugal
twisting moment of the blades that tends to flatten the
blades toward low pitch, and oil pressure applied to a
hydraulic piston connected to the propeller blades
which moves them toward high pitch. Another type of
constant-speed propeller uses counterweights attached
to the blade shanks in the hub. Governor oil pressure
and the blade twisting moment move the blades toward
the low pitch position, and centrifugal force acting on
the counterweights moves them (and the blades)
toward the high pitch position. In the first case above,
governor oil pressure moves the blades towards high
pitch, and in the second case, governor oil pressure and
the blade twisting moment move the blades toward low
pitch. A loss of governor oil pressure, therefore, will
affect each differently.
GOVERNING RANGE
The blade angle range for constant-speed propellers
varies from about 11 1/2 to 40°. The higher the speed
of the airplane, the greater the blade angle range.
The range of possible blade angles is termed the
propeller’s governing range. The governing range is
defined by the limits of the propeller blade’s travel
between high and low blade angle pitch stops. As long
as the propeller blade angle is within the governing
range and not against either pitch stop, a constant
engine r.p.m. will be maintained. However, once the
propeller blade reaches its pitch-stop limit, the engine
r.p.m. will increase or decrease with changes in
airspeed and propeller load similar to a fixed-pitch
propeller. For example, once a specific r.p.m. is
selected, if the airspeed decreases enough, the
propeller blades will reduce pitch, in an attempt to
maintain the selected r.p.m., until they contact their
low pitch stops. From that point, any further
reduction in airspeed will cause the engine r.p.m.
to decrease. Conversely, if the airspeed increases,
the propeller blade angle will increase until the
high pitch stop is reached. The engine r.p.m. will
then begin to increase.
CONSTANT-SPEED
PROPELLER OPERATION
The engine is started with the propeller control in the
low pitch/high r.p.m. position. This position reduces
the load or drag of the propeller and the result is easier
starting and warm-up of the engine. During warm-up,
the propeller blade changing mechanism should be
operated slowly and smoothly through a full cycle.
This is done by moving the propeller control (with the
Fixed Gear
Retractable
Turbo Retractable
Turbine Retractable
Transport Retractable
Aircraft Type Design Speed
(m.p.h.)
Blade Angle
Range
Pitch
Low High
160
180
225/240
250/300
325
111/2°
15°
20°
30°
40°
101/2°
11°
14°
10°
10/15°
22°
26°
34°
40°
50/55°
Figure 11-4. Blade angle range (values are approximate).
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11-6
manifold pressure set to produce about 1,600 r.p.m.)
to the high pitch/low r.p.m. position, allowing the
r.p.m. to stabilize, and then moving the propeller
control back to the low pitch takeoff position. This
should be done for two reasons: to determine
whether the system is operating correctly, and to
circulate fresh warm oil through the propeller
governor system. It should be remembered that the
oil has been trapped in the propeller cylinder since
the last time the engine was shut down. There is a
certain amount of leakage from the propeller
cylinder, and the oil tends to congeal, especially if
the outside air temperature is low. Consequently, if
the propeller isn’t exercised before takeoff, there is
a possibility that the engine may overspeed
on takeoff.
An airplane equipped with a constant-speed propeller
has better takeoff performance than a similarly powered
airplane equipped with a fixed-pitch propeller. This is
because with a constant-speed propeller, an airplane can
develop its maximum rated horsepower (red line on the
tachometer) while motionless. An airplane with a fixedpitch
propeller, on the other hand, must accelerate down
the runway to increase airspeed and aerodynamically
unload the propeller so that r.p.m. and horsepower can
steadily build up to their maximum. With a constantspeed
propeller, the tachometer reading should come up
to within 40 r.p.m. of the red line as soon as full power is
applied, and should remain there for the entire takeoff.
Excessive manifold pressure raises the cylinder
compression pressure, resulting in high stresses within
the engine. Excessive pressure also produces high
engine temperatures. A combination of high manifold
pressure and low r.p.m. can induce damaging
detonation. In order to avoid these situations, the
following sequence should be followed when making
power changes.
• When increasing power, increase the r.p.m. first,
and then the manifold pressure.
• When decreasing power, decrease the manifold
pressure first, and then decrease the r.p.m.
It is a fallacy that (in non-turbocharged engines) the
manifold pressure in inches of mercury (inches Hg)
should never exceed r.p.m. in hundreds for cruise
power settings. The cruise power charts in the
AFM/POH should be consulted when selecting cruise
power settings. Whatever the combinations of r.p.m.
and manifold pressure listed in these charts—they have
been flight tested and approved by the airframe and
powerplant engineers for the respective airframe and
engine manufacturer. Therefore, if there are power
settings such as 2,100 r.p.m. and 24 inches manifold
pressure in the power chart, they are approved for use.
With a constant-speed propeller, a power descent can
be made without overspeeding the engine. The system
compensates for the increased airspeed of the descent
by increasing the propeller blade angles. If the descent
is too rapid, or is being made from a high altitude, the
maximum blade angle limit of the blades is not
sufficient to hold the r.p.m. constant. When this
occurs, the r.p.m. is responsive to any change
in throttle setting.
Some pilots consider it advisable to set the propeller
control for maximum r.p.m. during the approach to
have full horsepower available in case of emergency.
If the governor is set for this higher r.p.m. early in the
approach when the blades have not yet reached their
minimum angle stops, the r.p.m. may increase to
unsafe limits. However, if the propeller control is not
readjusted for the takeoff r.p.m. until the approach is
almost completed, the blades will be against, or very
near their minimum angle stops and there will be little
if any change in r.p.m. In case of emergency, both
throttle and propeller controls should be moved to
takeoff positions.
Many pilots prefer to feel the airplane respond
immediately when they give short bursts of the
throttle during approach. By making the approach
under a little power and having the propeller control
set at or near cruising r.p.m., this result can
be obtained.
Although the governor responds quickly to any change
in throttle setting, a sudden and large increase in the
throttle setting will cause a momentary overspeeding
of the engine until the blades become adjusted to
absorb the increased power. If an emergency
demanding full power should arise during approach,
the sudden advancing of the throttle will cause
momentary overspeeding of the engine beyond the
r.p.m. for which the governor is adjusted. This
temporary increase in engine speed acts as an
emergency power reserve.
Some important points to remember concerning
constant-speed propeller operation are:
• The red line on the tachometer not only indicates
maximum allowable r.p.m.; it also indicates
the r.p.m. required to obtain the engine’s
rated horsepower.
• Amomentary propeller overspeed may occur
when the throttle is advanced rapidly for takeoff.
This is usually not serious if the rated r.p.m. is
not exceeded by 10 percent for more than
3 seconds.
• The green arc on the tachometer indicates the
normal operating range. When developing
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power in this range, the engine drives the propeller.
Below the green arc, however, it is usually
the windmilling propeller that powers the
engine. Prolonged operation below the green arc
can be detrimental to the engine.
• On takeoffs from low elevation airports, the
manifold pressure in inches of mercury may
exceed the r.p.m. This is normal in most cases.
The pilot should consult the AFM/POH
for limitations.
• All power changes should be made smoothly
and slowly to avoid overboosting and/or
overspeeding.
TURBOCHARGING
The turbocharged engine allows the pilot to maintain
sufficient cruise power at high altitudes where there is
less drag, which means faster true airspeeds and
increased range with fuel economy. At the same time,
the powerplant has flexibility and can be flown at a low
altitude without the increased fuel consumption of a
turbine engine. When attached to the standard
powerplant, the turbocharger does not take any
horsepower from the powerplant to operate; it is
relatively simple mechanically, and some models can
pressurize the cabin as well.
The turbocharger is an exhaust-driven device, which
raises the pressure and density of the induction air
delivered to the engine. It consists of two separate
components: a compressor and a turbine connected by
a common shaft. The compressor supplies pressurized
air to the engine for high altitude operation. The
compressor and its housing are between the ambient
air intake and the induction air manifold. The turbine
and its housing are part of the exhaust system and
utilize the flow of exhaust gases to drive the
compressor.
The turbine has the capability of producing manifold
pressure in excess of the maximum allowable for the
particular engine. In order not to exceed the maximum
allowable manifold pressure, a bypass or waste gate is
used so that some of the exhaust will be diverted
overboard before it passes through the turbine.
The position of the waste gate regulates the output of
the turbine and therefore, the compressed air available
to the engine. When the waste gate is closed, all of the
exhaust gases pass through and drive the turbine. As
the waste gate opens, some of the exhaust gases are
routed around the turbine, through the exhaust bypass
and overboard through the exhaust pipe.
The waste gate actuator is a spring-loaded piston,
operated by engine oil pressure. The actuator, which
adjusts the waste gate position, is connected to the
waste gate by a mechanical linkage.
The control center of the turbocharger system is
the pressure controller. This device simplifies
turbocharging to one control: the throttle. Once the
pilot has set the desired manifold pressure, virtually no
throttle adjustment is required with changes in altitude.
The controller senses compressor discharge
requirements for various altitudes and controls the oil
pressure to the waste gate actuator which adjusts the
waste gate accordingly. Thus the turbocharger
maintains only the manifold pressure called for by the
throttle setting.
GROUND BOOSTING VS. ALTITUDE
TURBOCHARGING
Altitude turbocharging (sometimes called “normalizing”)
is accomplished by using a turbocharger that
will maintain maximum allowable sea level manifold
pressure (normally 29 – 30 inches Hg) up to a certain
altitude. This altitude is specified by the airplane
manufacturer and is referred to as the airplane’s
critical altitude. Above the critical altitude,
EXHAUST GAS
DISCHARGE
WASTE GATE
This controls the amount of exhaust through the turbine.
Waste gate position is actuated by engine oil pressure.
TURBOCHARGER
The turbocharger incorporates a
turbine, which is driven by exhaust
gases, and a compressor that
pressurizes the incoming air.
THROTTLE BODY
This regulates airflow
to the engine.
INTAKE MANIFOLD
Pressurized air from the
turbocharger is supplied to
the cylinders.
EXHAUST MANIFOLD
Exhaust gas is ducted through
the exhaust manifold and is
used to turn the turbine which
drives the compressor.
AIR INTAKE
Intake air is ducted to
the turbocharger where
it is compressed.
Figure 11-5.Turbocharging system.
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11-8
the manifold pressure decreases as additional altitude
is gained. Ground boosting, on the other hand, is an
application of turbocharging where more than the
standard 29 inches of manifold pressure is used in
flight. In various airplanes using ground boosting,
takeoff manifold pressures may go as high as 45
inches of mercury.
Although a sea level power setting and maximum
r.p.m. can be maintained up to the critical altitude,
this does not mean that the engine is developing sea
level power. Engine power is not determined just by
manifold pressure and r.p.m. Induction air
temperature is also a factor. Turbocharged induction
air is heated by compression. This temperature rise
decreases induction air density which causes a
power loss. Maintaining the equivalent horsepower
output will require a somewhat higher manifold
pressure at a given altitude than if the induction air
were not compressed by turbocharging. If, on the
other hand, the system incorporates an automatic
density controller which, instead of maintaining a
constant manifold pressure, automatically positions
the waste gate so as to maintain constant air density
to the engine, a near constant horsepower output
will result.
OPERATING CHARACTERISTICS
First and foremost, all movements of the power
controls on turbocharged engines should be slow and
gentle. Aggressive and/or abrupt throttle movements
increase the possibility of overboosting. The pilot
should carefully monitor engine indications when
making power changes.
When the waste gate is open, the turbocharged engine
will react the same as a normally aspirated engine
when the r.p.m. is varied. That is, when the r.p.m. is
increased, the manifold pressure will decrease slightly.
When the engine r.p.m. is decreased, the manifold
pressure will increase slightly. However, when the
waste gate is closed, manifold pressure variation with
engine r.p.m. is just the opposite of the normally
aspirated engine. An increase in engine r.p.m. will
result in an increase in manifold pressure, and a
decrease in engine r.p.m. will result in a decrease in
manifold pressure.
Above the critical altitude, where the waste gate
is closed, any change in airspeed will result in a
corresponding change in manifold pressure. This is
true because the increase in ram air pressure with an
increase in airspeed is magnified by the compressor
resulting in an increase in manifold pressure. The
increase in manifold pressure creates a higher mass
flow through the engine, causing higher turbine speeds
and thus further increasing manifold pressure.
When running at high altitudes, aviation gasoline may
tend to vaporize prior to reaching the cylinder. If this
occurs in the portion of the fuel system between the
fuel tank and the engine-driven fuel pump, an
auxiliary positive pressure pump may be needed in the
tank. Since engine-driven pumps pull fuel, they are
easily vapor locked. A boost pump provides positive
pressure—pushes the fuel—reducing the tendency to
vaporize.
HEAT MANAGEMENT
Turbocharged engines must be thoughtfully and
carefully operated, with continuous monitoring of
pressures and temperatures. There are two temperatures
that are especially important—turbine inlet
temperature (TIT) or in some installations exhaust gas
temperature (EGT), and cylinder head temperature.
TIT or EGT limits are set to protect the elements in the
hot section of the turbocharger, while cylinder head
temperature limits protect the engine’s internal parts.
Due to the heat of compression of the induction air, a
turbocharged engine runs at higher operating
temperatures than a non-turbocharged engine. Because
turbocharged engines operate at high altitudes, their
environment is less efficient for cooling. At altitude
the air is less dense and therefore, cools less
efficiently. Also, the less dense air causes the
compressor to work harder. Compressor turbine
speeds can reach 80,000 – 100,000 r.p.m., adding
to the overall engine operating temperatures.
Turbocharged engines are also operated at higher
power settings a greater portion of the time.
High heat is detrimental to piston engine operation. Its
cumulative effects can lead to piston, ring, and
cylinder head failure, and place thermal stress on other
operating components. Excessive cylinder head
temperature can lead to detonation, which in turn can
cause catastrophic engine failure. Turbocharged
engines are especially heat sensitive. The key to
turbocharger operation, therefore, is effective heat
management.
The pilot monitors the condition of a turbocharged
engine with manifold pressure gauge, tachometer,
exhaust gas temperature/turbine inlet temperature
gauge, and cylinder head temperature. The pilot
manages the “heat system” with the throttle, propeller
r.p.m., mixture, and cowl flaps. At any given cruise
power, the mixture is the most influential control over
the exhaust gas/turbine inlet temperature. The throttle
regulates total fuel flow, but the mixture governs the
fuel to air ratio. The mixture, therefore, controls
temperature.
Exceeding temperature limits in an after takeoff climb
is usually not a problem since a full rich mixture cools
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11-9
with excess fuel. At cruise, however, the pilot normally
reduces power to 75 percent or less and simultaneously
adjusts the mixture. Under cruise conditions,
temperature limits should be monitored most closely
because it’s there that the temperatures are most likely
to reach the maximum, even though the engine is
producing less power. Overheating in an enroute
climb, however, may require fully open cowl flaps and
a higher airspeed.
Since turbocharged engines operate hotter at altitude
than do normally aspirated engines, they are more
prone to damage from cooling stress. Gradual
reductions in power, and careful monitoring of
temperatures are essential in the descent phase. The
pilot may find it helpful to lower the landing gear to
give the engine something to work against while power
is reduced and provide time for a slow cool down. It
may also be necessary to lean the mixture slightly to
eliminate roughness at the lower power settings.
TURBOCHARGER FAILURE
Because of the high temperatures and pressures
produced in the turbine exhaust systems, any
malfunction of the turbocharger must be treated with
extreme caution. In all cases of turbocharger operation,
the manufacturer’s recommended procedures should
be followed. This is especially so in the case of
turbocharger malfunction. However, in those instances
where the manufacturer’s procedures do not
adequately describe the actions to be taken in the event
of a turbocharger failure, the following procedures
should be used.
OVERBOOST CONDITION
If an excessive rise in manifold pressure occurs during
normal advancement of the throttle (possibly owing to
faulty operation of the waste gate):
• Immediately retard the throttle smoothly to limit
the manifold pressure below the maximum for
the r.p.m. and mixture setting.
• Operate the engine in such a manner as to avoid a
further overboost condition.
LOW MANIFOLD PRESSURE
Although this condition may be caused by a minor
fault, it is quite possible that a serious exhaust leak has
occurred creating a potentially hazardous situation:
• Shut down the engine in accordance with the
recommended engine failure procedures, unless
a greater emergency exists that warrants continued
engine operation.
• If continuing to operate the engine, use the lowest
power setting demanded by the situation and
land as soon as practicable.
It is very important to ensure that corrective
maintenance is undertaken following any
turbocharger malfunction.
RETRACTABLE LANDING GEAR
The primary benefits of being able to retract the
landing gear are increased climb performance and
higher cruise airspeeds due to the resulting decrease in
drag. Retractable landing gear systems may be
operated either hydraulically or electrically, or may
employ a combination of the two systems. Warning
indicators are provided in the cockpit to show the pilot
when the wheels are down and locked and when they
are up and locked or if they are in intermediate
positions. Systems for emergency operation are also
provided. The complexity of the retractable landing
gear system requires that specific operating procedures
be adhered to and that certain operating limitations not
be exceeded.
LANDING GEAR SYSTEMS
An electrical landing gear retraction system utilizes an
electrically driven motor for gear operation. The
system is basically an electrically driven jack for
raising and lowering the gear. When a switch in the
cockpit is moved to the UP position, the electric motor
operates. Through a system of shafts, gears, adapters,
an actuator screw, and a torque tube, a force is
transmitted to the drag strut linkages. Thus, the gear
retracts and locks. Struts are also activated that open
and close the gear doors. If the switch is moved to the
DOWN position, the motor reverses and the gear
moves down and locks. Once activated the gear motor
will continue to operate until an up or down limit
switch on the motor’s gearbox is tripped.
A hydraulic landing gear retraction system utilizes
pressurized hydraulic fluid to actuate linkages to raise
and lower the gear. When a switch in the cockpit is
moved to the UP position, hydraulic fluid is directed
into the gear up line. The fluid flows through
sequenced valves and downlocks to the gear
actuating cylinders. A similar process occurs during
gear extension. The pump which pressurizes the fluid
in the system can be either engine driven or
electrically powered. If an electrically powered pump
is used to pressurize the fluid, the system is referred
to as an electrohydraulic system. The system also
incorporates a hydraulic reservoir to contain excess
fluid, and to provide a means of determining system
fluid level.
Regardless of its power source, the hydraulic pump is
designed to operate within a specific range. When a
sensor detects excessive pressure, a relief valve within
the pump opens, and hydraulic pressure is routed back
to the reservoir. Another type of relief valve prevents
excessive pressure that may result from thermal expansion.
Hydraulic pressure is also regulated by limit
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11-10
switches. Each gear has two limit switches—one
dedicated to extension and one dedicated to retraction.
These switches de-energize the hydraulic pump after
the landing gear has completed its gear cycle. In the
event of limit switch failure, a backup pressure relief
valve activates to relieve excess system pressure.
CONTROLS AND POSITION INDICATORS
Landing gear position is controlled by a switch in the
cockpit. In most airplanes, the gear switch is shaped
like a wheel in order to facilitate positive identification
and to differentiate it from other cockpit controls.
Landing gear position indicators vary with different
make and model airplanes. The most common types of
landing gear position indicators utilize a group of
lights. One type consists of a group of three green
lights, which illuminate when the landing gear is down
and locked. Another type consists of one
green light to indicate when the landing gear is down
and an amber light to indicate when the gear is up. Still
other systems incorporate a red or amber light to
indicate when the gear is in transit or unsafe for
landing. The lights are usually of the
“press to test” type, and the bulbs are interchangeable.
Other types of landing gear position indicators consist
of tab-type indicators with markings “UP” to indicate
the gear is up and locked, a display of red and white
diagonal stripes to show when the gear is unlocked, or
a silhouette of each gear to indicate when it locks in
the DOWN position.
LANDING GEAR SAFETY DEVICES
Most airplanes with a retractable landing gear have a
gear warning horn that will sound when the airplane is
configured for landing and the landing gear is not
down and locked. Normally, the horn is linked to the
throttle or flap position, and/or the airspeed indicator
so that when the airplane is below a certain airspeed,
configuration, or power setting with the gear retracted,
the warning horn will sound.
Accidental retraction of a landing gear may be
prevented by such devices as mechanical downlocks,
safety switches, and ground locks. Mechanical
downlocks are built-in components of a gear retraction
system and are operated automatically by the gear
retraction system. To prevent accidental operation of
the downlocks, and inadvertent landing gear retraction
while the airplane is on the ground, electrically
operated safety switches are installed.
A landing gear safety switch, sometimes referred to as
a squat switch, is usually mounted in a bracket on one
of the main gear shock struts. When the
strut is compressed by the weight of the airplane, the
switch opens the electrical circuit to the motor or
mechanism that powers retraction. In this way, if the
landing gear switch in the cockpit is placed in the
RETRACT position when weight is on the gear, the
gear will remain extended, and the warning horn may
sound as an alert to the unsafe condition. Once the
weight is off the gear, however, such as on takeoff, the
safety switch will release and the gear will retract.
Many airplanes are equipped with additional safety
devices to prevent collapse of the gear when the
airplane is on the ground. These devices are called
ground locks. One common type is a pin installed in
aligned holes drilled in two or more units of the
landing gear support structure. Another type is a
spring-loaded clip designed to fit around and hold two
or more units of the support structure together. All
types of ground locks usually have red streamers
permanently attached to them to readily indicate
whether or not they are installed.
EMERGENCY GEAR EXTENSION SYSTEMS
The emergency extension system lowers the landing
gear if the main power system fails. Some airplanes
Figure 11-6. Typical landing gear switches and position
indicators.
Figure 11-7. Typical landing gear switches and position
indicators.
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11-11
have an emergency release handle in the cockpit,
which is connected through a mechanical linkage to
the gear uplocks. When the handle is operated, it
releases the uplocks and allows the gears to free fall, or
extend under their own weight.
Safety Switch
Landing Gear
Selector Valve
Lock Release
Solenoid
Lock-Pin
28V DC
Bus Bar
Figure 11-8. Landing gear safety switch.
Hand Pump Compressed Gas
Hand Crank
Figure 11-9.Typical emergency gear extension systems.
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11-12
should then turn on the battery master switch and
ensure that the landing gear position indicators show
that the gear is down and locked.
External inspection of the landing gear should
consist of checking individual system components.
The landing gear, wheel well, and
adjacent areas should be clean and free of mud and
debris. Dirty switches and valves may cause false
safe light indications or interrupt the extension cycle
before the landing gear is completely down and
locked. The wheel wells should be clear of any
obstructions, as foreign objects may damage the gear
or interfere with its operation. Bent gear doors may
Figure 11-10. Retractable landing gear inspection
checkpoints.
On other airplanes, release of the uplock is
accomplished using compressed gas, which is directed
to uplock release cylinders.
In some airplanes, design configurations make
emergency extension of the landing gear by gravity
and air loads alone impossible or impractical. In these
airplanes, provisions are included for forceful gear
extension in an emergency. Some installations are
designed so that either hydraulic fluid or compressed
gas provides the necessary pressure, while others use a
manual system such as a hand crank for emergency
gear extension. Hydraulic pressure for
emergency operation of the landing gear may be
provided by an auxiliary hand pump, an accumulator,
or an electrically powered hydraulic pump depending
on the design of the airplane.
OPERATIONAL PROCEDURES
PREFLIGHT
Because of their complexity, retractable landing gears
demand a close inspection prior to every flight. The
inspection should begin inside the cockpit. The pilot
should first make certain that the landing gear selector
switch is in the GEAR DOWN position. The pilot
Ch 11.qxd 5/7/04 8:50 AM Page 11-12
11-13
be an indication of possible problems with normal
gear operation.
Shock struts should be properly inflated and the
pistons clean. Main gear and nose gear uplock and
downlock mechanisms should be checked for general
condition. Power sources and retracting mechanisms
should be checked for general condition, obvious
defects, and security of attachment. Hydraulic lines
should be checked for signs of chafing, and leakage
at attach points. Warning system micro switches
(squat switches) should be checked for cleanliness
and security of attachment. Actuating cylinders,
sprockets, universals, drive gears, linkages and any
other accessible components should be checked for
condition and obvious defects. The airplane structure
to which the landing gear is attached should be
checked for distortion, cracks, and general condition.
All bolts and rivets should be intact and secure.
TAKEOFF AND CLIMB
Normally, the landing gear should be retracted after
lift-off when the airplane has reached an altitude
where, in the event of an engine failure or other
emergency requiring an aborted takeoff, the airplane
could no longer be landed on the runway. This procedure,
however, may not apply to all situations. Landing
gear retraction should be preplanned, taking into
account the length of the runway, climb gradient,
obstacle clearance requirements, the characteristics of
the terrain beyond the departure end of the runway, and
the climb characteristics of the particular airplane. For
example, in some situations it may be preferable, in the
event of an engine failure, to make an off airport forced
landing with the gear extended in order to take
advantage of the energy absorbing qualities of terrain
(see Chapter 16). In which case, a delay in retracting
the landing gear after takeoff from a short runway may
be warranted. In other situations, obstacles in the climb
path may warrant a timely gear retraction after takeoff.
Also, in some airplanes the initial climb pitch attitude
is such that any view of the runway remaining is
blocked, making an assessment of the feasibility of
touching down on the remaining runway difficult.
Premature landing gear retraction should be avoided.
The landing gear should not be retracted until a
positive rate of climb is indicated on the flight
instruments. If the airplane has not attained a positive
rate of climb, there is always the chance it may settle
back onto the runway with the gear retracted. This is
especially so in cases of premature lift-off. The pilot
should also remember that leaning forward to reach the
landing gear selector may result in inadvertent forward
pressure on the yoke, which will cause the airplane to
descend.
As the landing gear retracts, airspeed will increase and
the airplane’s pitch attitude may change. The gear may
take several seconds to retract. Gear retraction and
locking (and gear extension and locking) is
accompanied by sound and feel that are unique to the
specific make and model airplane. The pilot should
become familiar with the sounds and feel of normal
gear retraction so that any abnormal gear operation can
be readily discernable. Abnormal landing gear
retraction is most often a clear sign that the gear
extension cycle will also be abnormal.
APPROACH AND LANDING
The operating loads placed on the landing gear at
higher airspeeds may cause structural damage due to
the forces of the airstream. Limiting speeds, therefore,
are established for gear operation to protect the gear
components from becoming overstressed during flight.
These speeds are not found on the airspeed indicator.
They are published in the AFM/POH for the particular
airplane and are usually listed on placards in the
cockpit. The maximum landing
extended speed (VLE ) is the maximum speed at which
the airplane can be flown with the landing gear
extended. The maximum landing gear operating speed
(VLO) is the maximum speed at which the landing gear
may be operated through its cycle.
The landing gear is extended by placing the gear
selector switch in the GEAR DOWN position. As the
landing gear extends, the airspeed will decrease and
the pitch attitude may increase. During the several
seconds it takes for the gear to extend, the pilot
should be attentive to any abnormal sounds or feel.
The pilot should confirm that the landing gear has
extended and locked by the normal sound and feel of
the system operation as well as by the gear position
indicators in the cockpit. Unless the landing gear has
been previously extended to aid in a descent to traffic
pattern altitude, the landing gear should be extended
by the time the airplane reaches a point on the downwind
leg that is opposite the point of intended
landing. The pilot should establish a standard
procedure consisting of a specific position on the
downwind leg at which to lower the landing gear.
Strict adherence to this procedure will aid the pilot in
avoiding unintentional gear up landings.
Figure 11-11. Placarded gear speeds in the cockpit.
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11-14
Operation of an airplane equipped with a retractable
landing gear requires the deliberate, careful, and
continued use of an appropriate checklist. When on
the downwind leg, the pilot should make it a habit to
complete the landing gear checklist for that airplane.
This accomplishes two purposes. It ensures that
action has been taken to lower the gear, and it
increases the pilot’s awareness so that the gear down
indicators can be rechecked prior to landing.
Unless good operating practices dictate otherwise, the
landing roll should be completed and the airplane
clear of the runway before any levers or switches are
operated. This will accomplish the following: The
landing gear strut safety switches will be actuated,
deactivating the landing gear retract system. After
rollout and clearing the runway, the pilot will be able
to focus attention on the after landing checklist and to
identify the proper controls.
Pilots transitioning to retractable gear airplanes should
be aware that the most common pilot operational
factors involved in retractable gear airplane accidents
are:
• Neglected to extend landing gear.
• Inadvertently retracted landing gear.
• Activated gear, but failed to check gear position.
• Misused emergency gear system.
• Retracted gear prematurely on takeoff.
• Extended gear too late.
In order to minimize the chances of a landing gear
related mishap, the pilot should:
• Use an appropriate checklist. (A condensed
checklist mounted in view of the pilot as a
reminder for its use and easy reference can be
especially helpful.)
• Be familiar with, and periodically review, the
landing gear emergency extension procedures for
the particular airplane.
• Be familiar with the landing gear warning horn
and warning light systems for the particular
airplane. Use the horn system to cross-check the
warning light system when an unsafe condition
is noted.
• Review the procedure for replacing light bulbs
in the landing gear warning light displays for the
particular airplane, so that you can properly
replace a bulb to determine if the bulb(s) in the
display is good. Check to see if spare bulbs are
available in the airplane spare bulb supply as part
of the preflight inspection.
• Be familiar with and aware of the sounds and
feel of a properly operating landing gear system.
TRANSITION TRAINING
Transition to a complex airplane or a high
performance airplane should be accomplished through
a structured course of training administered by a
competent and qualified flight instructor. The training
should be accomplished in accordance with a ground
and flight training syllabus.
This sample syllabus for transition training is to be
considered flexible. The arrangement of the subject
matter may be changed and the emphasis may be
shifted to fit the qualifications of the transitioning
pilot, the airplane involved, and the circumstances of
the training situation, provided the prescribed
proficiency standards are achieved. These standards
are contained in the practical test standards
appropriate for the certificate that the transitioning
pilot holds or is working towards.
The training times indicated in the syllabus are based
on the capabilities of a pilot who is currently active
and fully meets the present requirements for the
issuance of at least a private pilot certificate. The time
periods may be reduced for pilots with higher
qualifications or increased for pilots who do not meet
the current certification requirements or who have had
little recent flight experience.
Ch 11.qxd 5/7/04 8:50 AM Page 11-14
11-15
1. Operations sections of
flight manual
2. Line inspection
3. Cockpit familiarization
1. Flight training maneuvers
2. Takeoffs, landings and
go-arounds
1. Aircraft loading, limitations
and servicing
2. Instruments, radio and
special equipment
3. Aircraft systems
1. Emergency operations
2. Control by reference to
instruments
3. Use of radio and autopilot
As assigned by flight instructor
1. Performance section of
flight manual
2. Cruise control
3. Review
1. Short and soft-field
takeoffs and landings
2. Maximum performance
operations
As assigned by flight instructor
Ground Instruction Flight Instruction Directed Practice*
1 Hour—CHECKOUT
1 Hour 1 Hour
1 Hour 1 Hour 1 Hour
1 Hour 1 Hour 1 Hour
* The directed practice indicated may be conducted solo or with a safety pilot at the discretion of the instructor.
Figure 11-12.Transition training syllabus.
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11-16
Ch 11.qxd 5/7/04 8:50 AM Page 11-16
MULTIENGINE FLIGHT
This chapter is devoted to the factors associated with
the operation of small multiengine airplanes. For the
purpose of this handbook, a “small” multiengine airplane
is a reciprocating or turbopropeller-powered
airplane with a maximum certificated takeoff weight
of 12,500 pounds or less. This discussion assumes a
conventional design with two engines—one mounted
on each wing. Reciprocating engines are assumed
unless otherwise noted. The term “light-twin,”
although not formally defined in the regulations, is
used herein as a small multiengine airplane with a
maximum certificated takeoff weight of 6,000 pounds
or less.
There are several unique characteristics of multiengine
airplanes that make them worthy of a separate class rating.
Knowledge of these factors and proficient flight
skills are a key to safe flight in these airplanes. This
chapter deals extensively with the numerous aspects of
one engine inoperative (OEI) flight. However, pilots
are strongly cautioned not to place undue emphasis
on mastery of OEI flight as the sole key to flying
multiengine airplanes safely. The inoperative engine
information that follows is extensive only because
this chapter emphasizes the differences between flying
multiengine airplanes as contrasted to single-engine
airplanes.
The modern, well-equipped multiengine airplane can
be remarkably capable under many circumstances. But,
as with single-engine airplanes, it must be flown prudently
by a current and competent pilot to achieve the
highest possible level of safety.
This chapter contains information and guidance on the
performance of certain maneuvers and procedures in
small multiengine airplanes for the purposes of flight
training and pilot certification testing. The final
authority on the operation of a particular make and
model airplane, however, is the airplane manufacturer.
Both the flight instructor and the student should be
aware that if any of the guidance in this handbook conflicts
with the airplane manufacturer’s recommended
procedures and guidance as contained in the FAAapproved
Airplane Flight Manual and/or Pilot’s
Operating Handbook (AFM/POH), it is the airplane
manufacturer’s guidance and procedures that take
precedence.
GENERAL
The basic difference between operating a multiengine
airplane and a single-engine airplane is the potential
problem involving an engine failure. The penalties for
loss of an engine are twofold: performance and control.
The most obvious problem is the loss of 50 percent
of power, which reduces climb performance 80 to 90
percent, sometimes even more. The other is the control
problem caused by the remaining thrust, which
is now asymmetrical. Attention to both these factors
is crucial to safe OEI flight. The performance and
systems redundancy of a multiengine airplane is a
safety advantage only to a trained and proficient
pilot.
TERMS AND DEFINITIONS
Pilots of single-engine airplanes are already familiar
with many performance “V” speeds and their definitions.
Twin-engine airplanes have several additional
V speeds unique to OEI operation. These speeds are
differentiated by the notation “SE”, for single engine.
A review of some key V speeds and several new V
speeds unique to twin-engine airplanes follows.
• VR – Rotation speed. The speed at which back
pressure is applied to rotate the airplane to a takeoff
attitude.
• VLOF – Lift-off speed. The speed at which the
airplane leaves the surface. (Note: some manufacturers
reference takeoff performance data to
VR, others to VLOF.)
• VX – Best angle of climb speed. The speed at
which the airplane will gain the greatest altitude
for a given distance of forward travel.
• VXSE – Best angle-of-climb speed with one
engine inoperative.
• VY – Best rate of climb speed. The speed at
which the airplane will gain the most altitude for
a given unit of time.
• VYSE – Best rate-of-climb speed with one engine
inoperative. Marked with a blue radial line on
most airspeed indicators. Above the single-engine
absolute ceiling, VYSE yields the minimum rate of
sink.
• VSSE – Safe, intentional one-engine-inoperative
speed. Originally known as safe single-engine
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speed. Now formally defined in Title 14 of the
Code of Federal Regulations (14 CFR) part 23,
Airworthiness Standards, and required to be
established and published in the AFM/POH. It is
the minimum speed to intentionally render the
critical engine inoperative.
• VMC – Minimum control speed with the critical
engine inoperative. Marked with a red radial line
on most airspeed indicators. The minimum speed
at which directional control can be maintained
under a very specific set of circumstances outlined
in 14 CFR part 23, Airworthiness Standards.
Under the small airplane certification regulations
currently in effect, the flight test pilot must be able
to (1) stop the turn that results when the critical
engine is suddenly made inoperative within 20°
of the original heading, using maximum rudder
deflection and a maximum of 5° bank, and (2)
thereafter, maintain straight flight with not
more than a 5° bank. There is no requirement in
this determination that the airplane be capable
of climbing at this airspeed. VMC only
addresses directional control. Further discussion
of VMC as determined during airplane certification
and demonstrated in pilot training
follows in minimum control airspeed (VMC)
demonstration.
Figure 12-1. Airspeed indicator markings for a multiengine
airplane.
Unless otherwise noted, when V speeds are given in
the AFM/POH, they apply to sea level, standard day
conditions at maximum takeoff weight. Performance
speeds vary with aircraft weight, configuration, and
atmospheric conditions. The speeds may be stated in
statute miles per hour (m.p.h.) or knots (kts), and they
may be given as calibrated airspeeds (CAS) or indicated
airspeeds (IAS). As a general rule, the newer
AFM/POHs show V speeds in knots indicated airspeed
(KIAS). Some V speeds are also stated in knots calibrated
airspeed (KCAS) to meet certain regulatory
requirements. Whenever available, pilots should operate
the airplane from published indicated airspeeds.
With regard to climb performance, the multiengine
airplane, particularly in the takeoff or landing configuration,
may be considered to be a single-engine
airplane with its powerplant divided into two units.
There is nothing in 14 CFR part 23 that requires a
multiengine airplane to maintain altitude while in
the takeoff or landing configuration with one engine
inoperative. In fact, many twins are not required to
do this in any configuration, even at sea level.
The current 14 CFR part 23 single-engine climb
performance requirements for reciprocating enginepowered
multiengine airplanes are as follows.
• More than 6,000 pounds maximum weight
and/or VSO more than 61 knots: the singleengine
rate of climb in feet per minute (f.p.m.) at
5,000 feet MSL must be equal to at least .027
VSO
2. For airplanes type certificated February 4,
1991, or thereafter, the climb requirement is
expressed in terms of a climb gradient, 1.5 percent.
The climb gradient is not a direct equivalent
of the .027 VSO
2 formula. Do not confuse the
date of type certification with the airplane’s
model year. The type certification basis of many
multiengine airplanes dates back to CAR 3 (the
Civil Aviation Regulations, forerunner of today’s
Code of Federal Regulations).
• 6,000 pounds or less maximum weight and VSO
61 knots or less: the single-engine rate of climb
at 5,000 feet MSL must simply be determined.
The rate of climb could be a negative number.
There is no requirement for a single-engine
positive rate of climb at 5,000 feet or any other
altitude. For light-twins type certificated
February 4, 1991, or thereafter, the singleengine
climb gradient (positive or negative) is
simply determined.
Rate of climb is the altitude gain per unit of time, while
climb gradient is the actual measure of altitude gained
per 100 feet of horizontal travel, expressed as a percentage.
An altitude gain of 1.5 feet per 100 feet of
travel (or 15 feet per 1,000, or 150 feet per 10,000) is a
climb gradient of 1.5 percent.
There is a dramatic performance loss associated with
the loss of an engine, particularly just after takeoff.
Any airplane’s climb performance is a function of
thrust horsepower which is in excess of that required
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for level flight. In a hypothetical twin with each engine
producing 200 thrust horsepower, assume that the total
level-flight thrust horsepower required is 175. In this
situation, the airplane would ordinarily have a reserve
of 225 thrust horsepower available for climb. Loss of
one engine would leave only 25 (200 minus 175) thrust
horsepower available for climb, a drastic reduction.
Sea level rate-of-climb performance losses of at least
80 to 90 percent, even under ideal circumstances, are
typical for multiengine airplanes in OEI flight.
OPERATION OF SYSTEMS
This section will deal with systems that are generally
found on multiengine airplanes. Multiengine airplanes
share many features with complex single-engine airplanes.
There are certain systems and features covered
here, however, that are generally unique to airplanes
with two or more engines.
PROPELLERS
The propellers of the multiengine airplane may outwardly
appear to be identical in operation to the
constant-speed propellers of many single-engine
airplanes, but this is not the case. The propellers of
multiengine airplanes are featherable, to minimize
drag in the event of an engine failure. Depending
upon single-engine performance, this feature often
permits continued flight to a suitable airport following
an engine failure. To feather a propeller is to stop
engine rotation with the propeller blades streamlined
with the airplane’s relative wind, thus to minimize
drag.
Feathering is necessary because of the change in parasite
drag with propeller blade angle.
When the propeller blade angle is in the feathered
position, the change in parasite drag is at a minimum
and, in the case of a typical multiengine airplane, the
added parasite drag from a single feathered propeller
is a relatively small contribution to the airplane total
drag.
At the smaller blade angles near the flat pitch position,
the drag added by the propeller is very large. At these
small blade angles, the propeller windmilling at high
r.p.m. can create such a tremendous amount of drag that
the airplane may be uncontrollable. The propeller windmilling
at high speed in the low range of blade angles
can produce an increase in parasite drag which may be
as great as the parasite drag of the basic airplane.
As a review, the constant-speed propellers on almost
all single-engine airplanes are of the non-feathering,
oil-pressure-to-increase-pitch design. In this design,
increased oil pressure from the propeller governor
drives the blade angle towards high pitch, low r.p.m.
In contrast, the constant-speed propellers installed
on most multiengine airplanes are full feathering,
counterweighted, oil-pressure-to-decrease-pitch
designs. In this design, increased oil pressure from the
propeller governor drives the blade angle towards low
pitch, high r.p.m.—away from the feather blade angle.
In effect, the only thing that keeps these propellers
from feathering is a constant supply of high pressure
engine oil. This is a necessity to enable propeller feathering
in the event of a loss of oil pressure or a propeller
governor failure.
Full
Feathered
90°
High
Pitch
Low
Pitch
Figure 12-2. Feathered propeller.
Change in
Equivalent
Parasite
Drag
Propeller Blade Angle
0 15 30 45 60 90
PROPELLER DRAG CONTRIBUTION
Windmilling
Propeller
Stationary
Propeller Feathered
Position
Flat Blade Position
Figure 12-3. Propeller drag contribution.
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The aerodynamic forces alone acting upon a windmilling
propeller tend to drive the blades to low pitch,
high r.p.m. Counterweights attached to the shank of
each blade tend to drive the blades to high pitch, low
r.p.m. Inertia, or apparent force called centrifugal force
acting through the counterweights is generally slightly
greater than the aerodynamic forces. Oil pressure from
the propeller governor is used to counteract the counterweights
and drives the blade angles to low pitch,
high r.p.m. Areduction in oil pressure causes the r.p.m.
to be reduced from the influence of the counterweights.
To feather the propeller, the propeller control is
brought fully aft. All oil pressure is dumped from the
governor, and the counterweights drive the propeller
blades towards feather. As centrifugal force acting on
the counterweights decays from decreasing r.p.m.,
additional forces are needed to completely feather the
blades. This additional force comes from either a
spring or high pressure air stored in the propeller
dome, which forces the blades into the feathered position.
The entire process may take up to 10 seconds.
Feathering a propeller only alters blade angle and stops
engine rotation. To completely secure the engine, the
pilot must still turn off the fuel (mixture, electric boost
pump, and fuel selector), ignition, alternator/generator,
and close the cowl flaps. If the airplane is pressurized,
there may also be an air bleed to close for the failed
engine. Some airplanes are equipped with firewall
shutoff valves that secure several of these systems
with a single switch.
Completely securing a failed engine may not be necessary
or even desirable depending upon the failure
mode, altitude, and time available. The position of the
fuel controls, ignition, and alternator/generator
switches of the failed engine has no effect on aircraft
performance. There is always the distinct possibility
of manipulating the incorrect switch under conditions
of haste or pressure.
To unfeather a propeller, the engine must be rotated
so that oil pressure can be generated to move the
propeller blades from the feathered position. The
ignition is turned on prior to engine rotation with the
throttle at low idle and the mixture rich. With the
propeller control in a high r.p.m. position, the starter
is engaged. The engine will begin to windmill, start,
and run as oil pressure moves the blades out of
feather. As the engine starts, the propeller r.p.m.
should be immediately reduced until the engine has
had several minutes to warm up; the pilot should
monitor cylinder head and oil temperatures.
Should the r.p.m. obtained with the starter be insufficient
to unfeather the propeller, an increase in airspeed
Counterweight
Action
Aerodynamic Force
Hydraulic Force
High-pressure oil enters the cylinder through the center of
the propeller shaft and piston rod. The propeller control
regulates the flow of high-pressure oil from a governor.
A hydraulic piston in the hub of the propeller is connected
to each blade by a piston rod. This rod is attached to forks
that slide over the pitch-change pin mounted in the root of
each blade.
The oil pressure moves the piston toward the front of the
cylinder, moving the piston rod and forks forward.
The forks push the pitch-change pin of each blade
toward the front of the hub, causing the blades to twist
toward the low-pitch position.
A nitrogen pressure charge or mechanical spring in
the front of the hub opposes the oil pressure, and
causes the propeller to move toward high-pitch.
Counterweights also cause the blades to move toward
the high-pitch and feather positions. The counterweights
counteract the aerodynamic twisting force that
tries to move the blades toward a low-pitch angle.
Nitrogen Pressure or Spring
Force, and Counterweight Action
Figure 12-4. Pitch change forces.
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from a shallow dive will usually help. In any event, the
AFM/POH procedures should be followed for the
exact unfeathering procedure. Both feathering and
starting a feathered reciprocating engine on the ground
are strongly discouraged by manufacturers due to the
excessive stress and vibrations generated.
As just described, a loss of oil pressure from the propeller
governor allows the counterweights, spring
and/or dome charge to drive the blades to feather.
Logically then, the propeller blades should feather
every time an engine is shut down as oil pressure falls
to zero. Yet, this does not occur. Preventing this is a
small pin in the pitch changing mechanism of the
propeller hub that will not allow the propeller blades
to feather once r.p.m. drops below approximately
800. The pin senses a lack of centrifugal force from
propeller rotation and falls into place, preventing the
blades from feathering. Therefore, if a propeller is to
be feathered, it must be done before engine r.p.m.
decays below approximately 800. On one popular
model of turboprop engine, the propeller blades do,
in fact, feather with each shutdown. This propeller is
not equipped with such centrifugally-operated pins,
due to a unique engine design.
An unfeathering accumulator is an optional device that
permits starting a feathered engine in flight without the
use of the electric starter. An accumulator is any device
that stores a reserve of high pressure. On multiengine
airplanes, the unfeathering accumulator stores a small
reserve of engine oil under pressure from compressed
air or nitrogen. To start a feathered engine in flight,
the pilot moves the propeller control out of the
feather position to release the accumulator pressure.
The oil flows under pressure to the propeller hub and
drives the blades toward the high r.p.m., low pitch
position, whereupon the propeller will usually begin
to windmill. (On some airplanes, an assist from the
electric starter may be necessary to initiate rotation
and completely unfeather the propeller.) If fuel and
ignition are present, the engine will start and run.
For airplanes used in training, this saves much electric
starter and battery wear. High oil pressure from
the propeller governor recharges the accumulator
just moments after engine rotation begins.
PROPELLER SYNCHRONIZATION
Many multiengine airplanes have a propeller synchronizer
(prop sync) installed to eliminate the annoying
“drumming” or “beat” of propellers whose r.p.m. are
close, but not precisely the same. To use prop sync, the
propeller r.p.m. are coarsely matched by the pilot and
the system is engaged. The prop sync adjusts the r.p.m.
of the “slave” engine to precisely match the r.p.m. of
the “master” engine, and then maintains that relationship.
The prop sync should be disengaged when the
pilot selects a new propeller r.p.m., then re-engaged
after the new r.p.m. is set. The prop sync should always
be off for takeoff, landing, and single-engine operation.
The AFM/POH should be consulted for system
description and limitations.
A variation on the propeller synchronizer is the propeller
synchrophaser. Prop sychrophase acts much
like a synchronizer to precisely match r.p.m., but the
synchrophaser goes one step further. It not only
matches r.p.m. but actually compares and adjusts the
positions of the individual blades of the propellers in
their arcs. There can be significant propeller noise and
vibration reductions with a propeller synchrophaser.
From the pilot’s perspective, operation of a propeller
synchronizer and a propeller syncrophaser are very
similar. A synchrophaser is also commonly referred to
as prop sync, although that is not entirely correct
nomenclature from a technical standpoint.
As a pilot aid to manually synchronizing the
propellers, some twins have a small gauge mounted
in or by the tachometer(s) with a propeller symbol
on a disk that spins. The pilot manually fine tunes
the engine r.p.m. so as to stop disk rotation, thereby
synchronizing the propellers. This is a useful backup
to synchronizing engine r.p.m. using the audible
propeller beat. This gauge is also found installed
with most propeller synchronizer and synchrophase
systems. Some synchrophase systems use a knob for
the pilot to control the phase angle.
FUEL CROSSFEED
Fuel crossfeed systems are also unique to multiengine
airplanes. Using crossfeed, an engine can draw fuel
from a fuel tank located in the opposite wing.
On most multiengine airplanes, operation in the crossfeed
mode is an emergency procedure used to extend
airplane range and endurance in OEI flight. There are
a few models that permit crossfeed as a normal, fuel
balancing technique in normal operation, but these are
not common. The AFM/POH will describe crossfeed
limitations and procedures, which vary significantly
among multiengine airplanes.
Checking crossfeed operation on the ground with a
quick repositioning of the fuel selectors does nothing
more than ensure freedom of motion of the handle. To
actually check crossfeed operation, a complete, functional
crossfeed system check should be accomplished.
To do this, each engine should be operated from its
crossfeed position during the runup. The engines
should be checked individually, and allowed to run at
moderate power (1,500 r.p.m. minimum) for at least 1
minute to ensure that fuel flow can be established from
the crossfeed source. Upon completion of the check,
each engine should be operated for at least 1 minute at
moderate power from the main (takeoff) fuel tanks to
reconfirm fuel flow prior to takeoff.
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12-6
This suggested check is not required prior to every
flight. Infrequently used, however, crossfeed lines are
ideal places for water and debris to accumulate unless
they are used from time to time and drained using their
external drains during preflight. Crossfeed is ordinarily
not used for completing single-engine flights when
an alternate airport is readily at hand, and it is never
used during takeoff or landings.
COMBUSTION HEATER
Combustion heaters are common on multiengine
airplanes. A combustion heater is best described as
a small furnace that burns gasoline to produce
heated air for occupant comfort and windshield
defogging. Most are thermostatically operated, and
have a separate hour meter to record time in service
for maintenance purposes. Automatic overtemperature
protection is provided by a thermal switch mounted on
the unit, which cannot be accessed in flight. This
requires the pilot or mechanic to actually visually
inspect the unit for possible heat damage in order to
reset the switch.
When finished with the combustion heater, a cool
down period is required. Most heaters require that outside
air be permitted to circulate through the unit for at
least 15 seconds in flight, or that the ventilation fan be
operated for at least 2 minutes on the ground. Failure
to provide an adequate cool down will usually trip the
thermal switch and render the heater inoperative until
the switch is reset.
FLIGHT DIRECTOR/AUTOPILOT
Flight director/autopilot (FD/AP) systems are common
on the better-equipped multiengine airplanes. The
system integrates pitch, roll, heading, altitude, and
radio navigation signals in a computer. The outputs,
called computed commands, are displayed on a flight
command indicator, or FCI. The FCI replaces the
conventional attitude indicator on the instrument
panel. The FCI is occasionally referred to as a flight
director indicator (FDI), or as an attitude director
indicator (ADI). The entire flight director/autopilot
system is sometimes called an integrated flight control
system (IFCS) by some manufacturers. Others
may use the term “automatic flight control system
(AFCS).”
The FD/AP system may be employed at three different
levels.
• Off (raw data).
• Flight director (computed commands).
• Autopilot.
With the system off, the FCI operates as an ordinary
attitude indicator. On most FCIs, the command bars
are biased out of view when the flight director is off.
The pilot maneuvers the airplane as though the system
were not installed.
To maneuver the airplane using the flight director, the
pilot enters the desired modes of operation (heading,
altitude, nav intercept, and tracking) on the FD/AP
mode controller. The computed flight commands are
then displayed to the pilot through either a single-cue
or dual-cue system in the FCI. On a single-cue system,
the commands are indicated by “V” bars. On a
dual-cue system, the commands are displayed on
two separate command bars, one for pitch and one
for roll. To maneuver the airplane using computed
commands, the pilot “flies” the symbolic airplane
of the FCI to match the steering cues presented.
On most systems, to engage the autopilot the flight
director must first be operating. At any time thereafter,
the pilot may engage the autopilot through the mode
controller. The autopilot then maneuvers the airplane
to satisfy the computed commands of the flight
director.
Like any computer, the FD/AP system will only do
what it is told. The pilot must ensure that it has been
properly programmed for the particular phase of flight
desired. The armed and/or engaged modes are usually
displayed on the mode controller or separate annunciator
lights. When the airplane is being hand-flown, if
the flight director is not being used at any particular
moment, it should be off so that the command bars are
pulled from view.
Prior to system engagement, all FD/AP computer and
trim checks should be accomplished. Many newer
systems cannot be engaged without the completion of
a self-test. The pilot must also be very familiar with
various methods of disengagement, both normal and
emergency. System details, including approvals and
limitations, can be found in the supplements section
of the AFM/POH. Additionally, many avionics manufacturers
can provide informative pilot operating
guides upon request.
YAW DAMPER
The yaw damper is a servo that moves the rudder in
response to inputs from a gyroscope or accelerometer
that detects yaw rate. The yaw damper minimizes
motion about the vertical axis caused by turbulence.
(Yaw dampers on sweptwing airplanes provide
another, more vital function of damping dutch roll
characteristics.) Occupants will feel a smoother ride,
particularly if seated in the rear of the airplane, when
the yaw damper is engaged. The yaw damper should
be off for takeoff and landing. There may be additional
restrictions against its use during single-engine operation.
Most yaw dampers can be engaged independently
of the autopilot.
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12-7
ALTERNATOR/GENERATOR
Alternator or generator paralleling circuitry matches
the output of each engine’s alternator/generator so that
the electrical system load is shared equally between
them. In the event of an alternator/generator failure,
the inoperative unit can be isolated and the entire
electrical system powered from the remaining one.
Depending upon the electrical capacity of the alternator/
generator, the pilot may need to reduce the
electrical load (referred to as load shedding) when
operating on a single unit. The AFM/POH will contain
system description and limitations.
NOSE BAGGAGE COMPARTMENT
Nose baggage compartments are common on multiengine
airplanes (and are even found on a few single-engine
airplanes). There is nothing strange or exotic about a
nose baggage compartment, and the usual guidance
concerning observation of load limits applies. They
are mentioned here in that pilots occasionally neglect
to secure the latches properly, and therein lies the
danger. When improperly secured, the door will open
and the contents may be drawn out, usually into the
propeller arc, and usually just after takeoff. Even when
the nose baggage compartment is empty, airplanes
have been lost when the pilot became distracted by the
open door. Security of the nose baggage compartment
latches and locks is a vital preflight item.
Most airplanes will continue to fly with a nose baggage
door open. There may be some buffeting from
the disturbed airflow and there will be an increase in
noise. Pilots should never become so preoccupied
with an open door (of any kind) that they fail to fly
the airplane.
Inspection of the compartment interior is also an
important preflight item. More than one pilot has been
surprised to find a supposedly empty compartment
packed to capacity or loaded with ballast. The tow
bars, engine inlet covers, windshield sun screens, oil
containers, spare chocks, and miscellaneous small
hand tools that find their way into baggage compartments
should be secured to prevent damage from
shifting in flight.
ANTI-ICING/DEICING
Anti-icing/deicing equipment is frequently installed on
multiengine airplanes and consists of a combination of
different systems. These may be classified as either
anti-icing or deicing, depending upon function. The
presence of anti-icing and deicing equipment, even
though it may appear elaborate and complete, does not
necessarily mean that the airplane is approved for
flight in icing conditions. The AFM/POH, placards,
and even the manufacturer should be consulted for
specific determination of approvals and limitations.
Anti-icing equipment is provided to prevent ice from
forming on certain protected surfaces. Anti-icing
equipment includes heated pitot tubes, heated or nonicing
static ports and fuel vents, propeller blades with
electrothermal boots or alcohol slingers, windshields
with alcohol spray or electrical resistance heating,
windshield defoggers, and heated stall warning lift
detectors. On many turboprop engines, the “lip”
surrounding the air intake is heated either electrically
or with bleed air. In the absence of AFM/POH guidance
to the contrary, anti-icing equipment is actuated prior to
flight into known or suspected icing conditions.
Deicing equipment is generally limited to pneumatic
boots on wing and tail leading edges. Deicing equipment
is installed to remove ice that has already formed
on protected surfaces. Upon pilot actuation, the boots
inflate with air from the pneumatic pumps to break off
accumulated ice. After a few seconds of inflation, they
are deflated back to their normal position with the
assistance of a vacuum. The pilot monitors the buildup
of ice and cycles the boots as directed in the
AFM/POH. An ice light on the left engine nacelle
allows the pilot to monitor wing ice accumulation at
night.
Other airframe equipment necessary for flight in icing
conditions includes an alternate induction air source
and an alternate static system source. Ice tolerant
antennas will also be installed.
In the event of impact ice accumulating over normal
engine air induction sources, carburetor heat (carbureted
engines) or alternate air (fuel injected engines)
should be selected. Ice buildup on normal induction
sources can be detected by a loss of engine r.p.m. with
fixed-pitch propellers and a loss of manifold pressure
with constant-speed propellers. On some fuel injected
engines, an alternate air source is automatically
activated with blockage of the normal air source.
An alternate static system provides an alternate source
of static air for the pitot-static system in the unlikely
event that the primary static source becomes blocked.
In non-pressurized airplanes, most alternate static
sources are plumbed to the cabin. On pressurized airplanes,
they are usually plumbed to a non-pressurized
baggage compartment. The pilot must activate the
alternate static source by opening a valve or a fitting in
the cockpit. Upon activation, the airspeed indicator,
altimeter, and the vertical speed indicator (VSI) will be
affected and will read somewhat in error. A correction
table is frequently provided in the AFM/POH.
Anti-icing/deicing equipment only eliminates ice from
the protected surfaces. Significant ice accumulations
may form on unprotected areas, even with proper use
of anti-ice and deice systems. Flight at high angles of
Ch 12.qxd 5/7/04 9:54 AM Page 12-7
12-8
attack or even normal climb speeds will permit significant
ice accumulations on lower wing surfaces, which
are unprotected. Many AFM/POHs mandate minimum
speeds to be maintained in icing conditions. Degradation
of all flight characteristics and large performance losses
can be expected with ice accumulations. Pilots should
not rely upon the stall warning devices for adequate stall
warning with ice accumulations.
Ice will accumulate unevenly on the airplane. It will
add weight and drag (primarily drag), and decrease
thrust and lift. Even wing shape affects ice accumulation;
thin airfoil sections are more prone to ice
accumulation than thick, highly-cambered sections.
For this reason certain surfaces, such as the horizontal
stabilizer, are more prone to icing than the wing. With
ice accumulations, landing approaches should be made
with a minimum wing flap setting (flap extension
increases the angle of attack of the horizontal stabilizer)
and with an added margin of airspeed. Sudden and large
configuration and airspeed changes should be avoided.
Unless otherwise recommended in the AFM/POH, the
autopilot should not be used in icing conditions.
Continuous use of the autopilot will mask trim and
handling changes that will occur with ice accumulation.
Without this control feedback, the pilot may not
be aware of ice accumulation building to hazardous
levels. The autopilot will suddenly disconnect when it
reaches design limits and the pilot may find the airplane
has assumed unsatisfactory handling characteristics.
The installation of anti-ice/deice equipment on airplanes
without AFM/POH approval for flight into icing
conditions is to facilitate escape when such conditions
are inadvertently encountered. Even with AFM/POH
approval, the prudent pilot will avoid icing conditions
to the maximum extent practicable, and avoid extended
flight in any icing conditions. No multiengine airplane
is approved for flight into severe icing conditions, and
none are intended for indefinite flight in continuous
icing conditions.
PERFORMANCE AND LIMITATIONS
Discussion of performance and limitations requires the
definition of several terms.
• Accelerate-stop distance is the runway length
required to accelerate to a specified speed (either
VR or VLOF, as specified by the manufacturer),
experience an engine failure, and bring the airplane
to a complete stop.
• Accelerate-go distance is the horizontal distance
required to continue the takeoff and climb
to 50 feet, assuming an engine failure at VR or
VLOF, as specified by the manufacturer.
• Climb gradient is a slope most frequently
expressed in terms of altitude gain per 100 feet
of horizontal distance, whereupon it is stated as
a percentage. A 1.5 percent climb gradient is an
altitude gain of one and one-half feet per 100 feet
of horizontal travel. Climb gradient may also be
expressed as a function of altitude gain per nautical
mile, or as a ratio of the horizontal distance
to the vertical distance (50:1, for example).
Unlike rate of climb, climb gradient is affected
by wind. Climb gradient is improved with a
headwind component, and reduced with a tailwind
component.
• The all-engine service ceiling of multiengine
airplanes is the highest altitude at which the airplane
can maintain a steady rate of climb of 100
f.p.m. with both engines operating. The airplane
has reached its absolute ceiling when climb is
no longer possible.
• The single-engine service ceiling is reached
when the multiengine airplane can no longer
maintain a 50 f.p.m. rate of climb with one engine
inoperative, and its single-engine absolute ceiling
when climb is no longer possible.
The takeoff in a multiengine airplane should be
planned in sufficient detail so that the appropriate
action is taken in the event of an engine failure. The
pilot should be thoroughly familiar with the airplane’s
performance capabilities and limitations in order to
make an informed takeoff decision as part of the preflight
planning. That decision should be reviewed as
the last item of the “before takeoff” checklist.
In the event of an engine failure shortly after takeoff,
the decision is basically one of continuing flight or
landing, even off-airport. If single-engine climb
performance is adequate for continued flight, and
the airplane has been promptly and correctly configured,
the climb after takeoff may be continued. If
single-engine climb performance is such that climb
is unlikely or impossible, a landing will have to be
made in the most suitable area. To be avoided above
all is attempting to continue flight when it is not
within the airplane’s performance capability to do
so.
Takeoff planning factors include weight and balance,
airplane performance (both single and multiengine),
runway length, slope and contamination, terrain and
obstacles in the area, weather conditions, and pilot
proficiency. Most multiengine airplanes have
AFM/POH performance charts and the pilot should
be highly proficient in their use. Prior to takeoff, the
multiengine pilot should ensure that the weight and
balance limitations have been observed, the runway
Ch 12.qxd 5/7/04 9:54 AM Page 12-8
length is adequate, the normal flightpath will clear obstacles
and terrain, and that a definitive course of action has
been planned in the event of an engine failure.
The regulations do not specifically require that the
runway length be equal to or greater than the accelerate-
stop distance. Most AFM/POHs publish
accelerate-stop distances only as an advisory. It
becomes a limitation only when published in the
limitations section of the AFM/POH. Experienced
multiengine pilots, however, recognize the safety
margin of runway lengths in excess of the bare minimum
required for normal takeoff. They will insist
on runway lengths of at least accelerate-stop distance
as a matter of safety and good operating
practice.
50 ft
Brake VR / VLOF
Release
Accelerate-Stop Distance
Accelerate-Go Distance
500 ft
Brake VLOF
Release
5,000 ft
10:1 or 10 Percent Climb Gradient
Figure 12-5. Accelerate-stop distance, accelerate-go distance, and climb gradient.
Figure 12-6. Area of decision.
12-9
VXSE
VYSE
Gear Up and Loss of One Engine
Best Rate of Climb
Best Angle of Climb
Decision Area
VR / VLOF
Brake
Release
ENGINE FAILURE AFTER LIFT-OFF
Ch 12.qxd 5/7/04 9:54 AM Page 12-9
The multiengine pilot must keep in mind that the
accelerate-go distance, as long as it is, has only
brought the airplane, under ideal circumstances, to a
point a mere 50 feet above the takeoff elevation. To
achieve even this meager climb, the pilot had to instantaneously
recognize and react to an unanticipated
engine failure, retract the landing gear, identify and
feather the correct engine, all the while maintaining
precise airspeed control and bank angle as the airspeed
is nursed to VYSE. Assuming flawless airmanship thus
far, the airplane has now arrived at a point little more
than one wingspan above the terrain, assuming it was
absolutely level and without obstructions.
With (for the purpose of illustration) a net 150 f.p.m.
rate of climb at a 90-knot VYSE, it will take approximately
3 minutes to climb an additional 450 feet to reach
500 feet AGL. In doing so, the airplane will have
traveled an additional 5 nautical miles beyond the
original accelerate-go distance, with a climb gradient
of about 1.6 percent. Aturn of any consequence, such
as to return to the airport, will seriously degrade the
already marginal climb performance.
Not all multiengine airplanes have published accelerate-
go distances in their AFM/POH, and fewer still
publish climb gradients. When such information is
published, the figures will have been determined under
ideal flight testing conditions. It is unlikely that this
performance will be duplicated in service conditions.
The point of the foregoing is to illustrate the marginal
climb performance of a multiengine airplane that
suffers an engine failure shortly after takeoff, even
under ideal conditions. The prudent multiengine
pilot should pick a point in the takeoff and climb
sequence in advance. If an engine fails before this point,
the takeoff should be rejected, even if airborne, for a
landing on whatever runway or surface lies essentially
ahead. If an engine fails after this point, the pilot should
promptly execute the appropriate engine failure procedure
and continue the climb, assuming the performance
capability exists. As a general recommendation, if the
landing gear has not been selected up, the takeoff
should be rejected, even if airborne.
As a practical matter for planning purposes, the option
of continuing the takeoff probably does not exist unless
the published single-engine rate-of-climb performance
is at least 100 to 200 f.p.m. Thermal turbulence, wind
gusts, engine and propeller wear, or poor technique in
airspeed, bank angle, and rudder control can easily
negate even a 200 f.p.m. rate of climb.
WEIGHT AND BALANCE
The weight and balance concept is no different than
that of a single-engine airplane. The actual execution,
however, is almost invariably more complex due to a
number of new loading areas, including nose and aft
baggage compartments, nacelle lockers, main fuel
tanks, aux fuel tanks, nacelle fuel tanks, and numerous
seating options in a variety of interior configurations.
The flexibility in loading offered by the multiengine
airplane places a responsibility on the pilot to address
weight and balance prior to each flight.
The terms “empty weight, licensed empty weight,
standard empty weight, and basic empty weight” as
they appear on the manufacturer’s original weight and
balance documents are sometimes confused by pilots.
In 1975, the General Aviation Manufacturers
Association (GAMA) adopted a standardized format
for AFM/POHs. It was implemented by most
manufacturers in model year 1976. Airplanes whose
manufacturers conform to the GAMA standards utilize
the following terminology for weight and balance:
Standard empty weight
+ Optional equipment
= Basic empty weight
Standard empty weight is the weight of the standard
airplane, full hydraulic fluid, unusable fuel, and full
oil. Optional equipment includes the weight of all
equipment installed beyond standard. Basic empty
weight is the standard empty weight plus optional
equipment. Note that basic empty weight includes no
usable fuel, but full oil.
Airplanes manufactured prior to the GAMA format
generally utilize the following terminology for weight
and balance, although the exact terms may vary somewhat:
Empty weight
+ Unusable fuel
= Standard empty weight
Standard empty weight
+ Optional equipment
= Licensed empty weight
Empty weight is the weight of the standard airplane,
full hydraulic fluid and undrainable oil. Unusable fuel
is the fuel remaining in the airplane not available to
the engines. Standard empty weight is the empty
weight plus unusable fuel. When optional equipment
is added to the standard empty weight, the result is
licensed empty weight. Licensed empty weight,
therefore, includes the standard airplane, optional
equipment, full hydraulic fluid, unusable fuel, and
undrainable oil.
The major difference between the two formats
(GAMA and the old) is that basic empty weight
includes full oil, and licensed empty weight does not.
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Ch 12.qxd 5/7/04 9:54 AM Page 12-10
Oil must always be added to any weight and balance
utilizing a licensed empty weight.
When the airplane is placed in service, amended
weight and balance documents are prepared by appropriately
rated maintenance personnel to reflect changes
in installed equipment. The old weight and balance
documents are customarily marked “superseded” and
retained in the AFM/POH. Maintenance personnel are
under no regulatory obligation to utilize the GAMA
terminology, so weight and balance documents
subsequent to the original may use a variety of
terms. Pilots should use care to determine whether
or not oil has to be added to the weight and balance
calculations or if it is already included in the figures
provided.
The multiengine airplane is where most pilots
encounter the term “zero fuel weight” for the first time.
Not all multiengine airplanes have a zero fuel weight
limitation published in their AFM/POH, but many do.
Zero fuel weight is simply the maximum allowable
weight of the airplane and payload, assuming there is
no usable fuel on board. The actual airplane is not
devoid of fuel at the time of loading, of course. This is
merely a calculation that assumes it was. If a zero fuel
weight limitation is published, then all weight in
excess of that figure must consist of usable fuel. The
purpose of a zero fuel weight is to limit load forces on
the wing spars with heavy fuselage loads.
Assume a hypothetical multiengine airplane with the
following weights and capacities:
Basic empty weight . . . . . . . . . . . . . . . . .3,200 lb.
Zero fuel weight . . . . . . . . . . . . . . . . . . . .4,400 lb.
Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.
Maximum usable fuel . . . . . . . . . . . . . . . .180 gal.
1. Calculate the useful load:
Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.
Basic empty weight . . . . . . . . . . . . . . . . .-3,200 lb.
Useful load . . . . . . . . . . . . . . . . . . . . . . . .2,000 lb.
The useful load is the maximum combination of usable
fuel, passengers, baggage, and cargo that the airplane
is capable of carrying.
2. Calculate the payload:
Zero fuel weight . . . . . . . . . . . . . . . . . . . . 4,400 lb.
Basic empty weight . . . . . . . . . . . . . . . . . -3,200 lb.
Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,200 lb.
The payload is the maximum combination of passengers,
baggage, and cargo that the airplane is capable
of carrying. A zero fuel weight, if published, is the
limiting weight.
3. Calculate the fuel capacity at maximum payload
(1,200 lb.):
Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.
Zero fuel weight . . . . . . . . . . . . . . . . . . .-4,400 lb.
Fuel allowed . . . . . . . . . . . . . . . . . . . . . . . .800 lb.
Assuming maximum payload, the only weight permitted
in excess of the zero fuel weight must consist of
usable fuel. In this case, 133.3 gallons.
4. Calculate the payload at maximum fuel capacity
(180 gal.):
Basic empty weight . . . . . . . . . . . . . . . . .3,200 lb.
Maximum usable fuel . . . . . . . . . . . . . . .+1,080 lb.
Weight with max. fuel . . . . . . . . . . . . . . .4,280 lb.
Maximum takeoff weight . . . . . . . . . . . . .5,200 lb.
Weight with max. fuel . . . . . . . . . . . . . . .-4,280 lb.
Payload allowed . . . . . . . . . . . . . . . . . . . . .920 lb.
Assuming maximum fuel, the payload is the difference
between the weight of the fueled airplane and the maximum
takeoff weight.
Some multiengine airplanes have a ramp weight,
which is in excess of the maximum takeoff weight. The
ramp weight is an allowance for fuel that would be
burned during taxi and runup, permitting a takeoff at
full maximum takeoff weight. The airplane must
weigh no more than maximum takeoff weight at the
beginning of the takeoff roll.
A maximum landing weight is a limitation against
landing at a weight in excess of the published value.
This requires preflight planning of fuel burn to ensure
that the airplane weight upon arrival at destination will
be at or below the maximum landing weight. In the
event of an emergency requiring an immediate landing,
the pilot should recognize that the structural
margins designed into the airplane are not fully
available when over landing weight. An overweight
landing inspection may be advisable—the service
manual or manufacturer should be consulted.
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Ch 12.qxd 5/7/04 9:54 AM Page 12-11
Although the foregoing problems only dealt with
weight, the balance portion of weight and balance
is equally vital. The flight characteristics of the
multiengine airplane will vary significantly with
shifts of the center of gravity (CG) within the
approved envelope.
At forward CGs, the airplane will be more stable, with
a slightly higher stalling speed, a slightly slower
cruising speed, and favorable stall characteristics.
At aft CGs, the airplane will be less stable, with a
slightly lower stalling speed, a slightly faster cruising
speed, and less desirable stall characteristics. Forward
CG limits are usually determined in certification by
elevator/stabilator authority in the landing roundout.
Aft CG limits are determined by the minimum
acceptable longitudinal stability. It is contrary to the
airplane’s operating limitations and the Code of
Federal Regulations (CFR) to exceed any weight
and balance parameter.
Some multiengine airplanes may require ballast to
remain within CG limits under certain loading conditions.
Several models require ballast in the aft baggage
compartment with only a student and instructor on
board to avoid exceeding the forward CG limit.
When passengers are seated in the aft-most seats of
some models, ballast or baggage may be required in
the nose baggage compartment to avoid exceeding
the aft CG limit. The pilot must direct the seating of
passengers and placement of baggage and cargo to
achieve a center of gravity within the approved
envelope. Most multiengine airplanes have general
loading recommendations in the weight and balance
section of the AFM/POH. When ballast is added, it
must be securely tied down and it must not exceed
the maximum allowable floor loading.
Some airplanes make use of a special weight and
balance plotter. It consists of several movable parts
that can be adjusted over a plotting board on which
the CG envelope is printed. The reverse side of the
typical plotter contains general loading recommendations
for the particular airplane. A pencil line plot
can be made directly on the CG envelope imprinted
on the working side of the plotting board. This plot
can easily be erased and recalculated anew for each
flight. This plotter is to be used only for the make
and model airplane for which it was designed.
GROUND OPERATION
Good habits learned with single-engine airplanes are
directly applicable to multiengine airplanes for preflight
and engine start. Upon placing the airplane in
motion to taxi, the new multiengine pilot will notice
several differences, however. The most obvious is
the increased wingspan and the need for even
greater vigilance while taxiing in close quarters.
Ground handling may seem somewhat ponderous
and the multiengine airplane will not be as nimble
as the typical two- or four-place single-engine airplane.
As always, use care not to ride the brakes by keeping
engine power to a minimum. One ground handling
advantage of the multiengine airplane over singleengine
airplanes is the differential power capability.
Turning with an assist from differential power minimizes
both the need for brakes during turns and the
turning radius.
The pilot should be aware, however, that making a
sharp turn assisted by brakes and differential power
can cause the airplane to pivot about a stationary
inboard wheel and landing gear. This is abuse for
which the airplane was not designed and should be
guarded against.
Unless otherwise directed by the AFM/POH, all
ground operations should be conducted with the cowl
flaps fully open. The use of strobe lights is normally
deferred until taxiing onto the active runway.
