NORMAL AND CROSSWIND
TAKEOFF AND CLIMB
With the “before takeoff” checklist complete and
air traffic control (ATC) clearance received, the airplane
should be taxied into position on the runway
centerline. If departing from an airport without an
operating control tower, a careful check for
approaching aircraft should be made along with a
radio advisory on the appropriate frequency. Sharp
turns onto the runway combined with a rolling
takeoff are not a good operating practice and may
be prohibited by the AFM/POH due to the possibility
of “unporting” a fuel tank pickup. (The takeoff itself
may be prohibited by the AFM/POH under any circumstances
below certain fuel levels.) The flight controls
should be positioned for a crosswind, if present.
Exterior lights such as landing and taxi lights, and
wingtip strobes should be illuminated immediately
prior to initiating the takeoff roll, day or night. If
holding in takeoff position for any length of time,
particularly at night, the pilot should activate all
exterior lights upon taxiing into position.
Takeoff power should be set as recommended in the
AFM/POH. With normally aspirated (non-turbocharged)
engines, this will be full throttle. Full
throttle is also used in most turbocharged engines.
There are some turbocharged engines, however,
that require the pilot to set a specific power setting,
usually just below red line manifold pressure. This
yields takeoff power with less than full throttle travel.
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Turbocharged engines often require special consideration.
Throttle motion with turbocharged engines
should be exceptionally smooth and deliberate. It is
acceptable, and may even be desirable, to hold the
airplane in position with brakes as the throttles are
advanced. Brake release customarily occurs after significant
boost from the turbocharger is established. This
prevents wasting runway with slow, partial throttle
acceleration as the engine power is increased. If runway
length or obstacle clearance is critical, full power should
be set before brake release, as specified in the performance
charts.
As takeoff power is established, initial attention should
be divided between tracking the runway centerline and
monitoring the engine gauges. Many novice multiengine
pilots tend to fixate on the airspeed indicator
just as soon as the airplane begins its takeoff roll.
Instead, the pilot should confirm that both engines
are developing full-rated manifold pressure and
r.p.m., and that the fuel flows, fuel pressures, exhaust
gas temperatures (EGTs), and oil pressures are matched
in their normal ranges. A directed and purposeful scan
of the engine gauges can be accomplished well before
the airplane approaches rotation speed. If a crosswind is
present, the aileron displacement in the direction of the
crosswind may be reduced as the airplane accelerates.
The elevator/stabilator control should be held neutral
throughout.
Full rated takeoff power should be used for every takeoff.
Partial power takeoffs are not recommended.
There is no evidence to suggest that the life of modern
reciprocating engines is prolonged by partial power
takeoffs. Paradoxically, excessive heat and engine
wear can occur with partial power as the fuel metering
system will fail to deliver the slightly over-rich
mixture vital for engine cooling during takeoff.
There are several key airspeeds to be noted during the
takeoff and climb sequence in any twin. The first speed
to consider is VMC. If an engine fails below VMC while
the airplane is on the ground, the takeoff must be
rejected. Directional control can only be maintained by
promptly closing both throttles and using rudder and
brakes as required. If an engine fails below VMC while
airborne, directional control is not possible with the
remaining engine producing takeoff power. On takeoffs,
therefore, the airplane should never be airborne
before the airspeed reaches and exceeds VMC. Pilots
should use the manufacturer’s recommended rotation
speed (VR) or lift-off speed (VLOF). If no such speeds
are published, a minimum of VMC plus 5 knots should
be used for VR.
The rotation to a takeoff pitch attitude is done
smoothly. With a crosswind, the pilot should ensure
that the landing gear does not momentarily touch the
runway after the airplane has lifted off, as a side drift
will be present. The rotation may be accomplished
more positively and/or at a higher speed under these
conditions. However, the pilot should keep in mind
that the AFM/POH performance figures for acceleratestop
distance, takeoff ground roll, and distance to clear
an obstacle were calculated at the recommended VR
and/or VLOF speed.
After lift-off, the next consideration is to gain altitude
as rapidly as possible. After leaving the ground,
altitude gain is more important than achieving an
excess of airspeed. Experience has shown that
excessive speed cannot be effectively converted into
altitude in the event of an engine failure. Altitude
gives the pilot time to think and react. Therefore, the
airplane should be allowed to accelerate in a shallow
climb to attain VY, the best all-engine rate-of-climb
speed. VY should then be maintained until a safe
single-engine maneuvering altitude, considering
terrain and obstructions, is achieved.
To assist the pilot in takeoff and initial climb profile,
some AFM/POHs give a “50-foot” or “50-foot barrier”
speed to use as a target during rotation, lift-off, and
acceleration to VY.
Landing gear retraction should normally occur after a
positive rate of climb is established. Some
AFM/POHs direct the pilot to apply the wheel brakes
momentarily after lift-off to stop wheel rotation prior
to landing gear retraction. If flaps were extended for
takeoff, they should be retracted as recommended in
the AFM/POH.
Once a safe single-engine maneuvering altitude has
been reached, typically a minimum of 400-500 feet
AGL, the transition to an enroute climb speed should
be made. This speed is higher than VY and is usually
maintained to cruising altitude. Enroute climb speed
gives better visibility, increased engine cooling, and a
higher groundspeed. Takeoff power can be reduced, if
desired, as the transition to enroute climb speed is
made.
Some airplanes have a climb power setting published
in the AFM/POH as a recommendation (or sometimes
as a limitation), which should then be set for enroute
climb. If there is no climb power setting published, it is
customary, but not a requirement, to reduce manifold
pressure and r.p.m. somewhat for enroute climb. The
propellers are usually synchronized after the first
power reduction and the yaw damper, if installed,
engaged. The AFM/POH may also recommend leaning
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12-14
the mixtures during climb. The “climb” checklist
should be accomplished as traffic and work load allow.
LEVEL OFF AND CRUISE
Upon leveling off at cruising altitude, the pilot should
allow the airplane to accelerate at climb power until
cruising airspeed is achieved, then cruise power and
r.p.m. should be set. To extract the maximum cruise
performance from any airplane, the power setting
tables provided by the manufacturer should be closely
followed. If the cylinder head and oil temperatures are
within their normal ranges, the cowl flaps may be
closed. When the engine temperatures have stabilized,
the mixtures may be leaned per AFM/POH recommendations.
The remainder of the “cruise” checklist should
be completed by this point.
Fuel management in multiengine airplanes is often
more complex than in single-engine airplanes.
Depending upon system design, the pilot may need to
select between main tanks and auxiliary tanks, or
even employ fuel transfer from one tank to another.
In complex fuel systems, limitations are often found
restricting the use of some tanks to level flight only,
or requiring a reserve of fuel in the main tanks for
descent and landing. Electric fuel pump operation can
vary widely among different models also, particularly
during tank switching or fuel transfer. Some fuel
pumps are to be on for takeoff and landing; others are
to be off. There is simply no substitute for thorough
systems and AFM/POH knowledge when operating
complex aircraft.
NORMAL APPROACH AND LANDING
Given the higher cruising speed (and frequently, altitude)
of multiengine airplanes over most single-engine
airplanes, the descent must be planned in advance. A
hurried, last minute descent with power at or near idle
is inefficient and can cause excessive engine cooling.
It may also lead to passenger discomfort, particularly
if the airplane is unpressurized. As a rule of thumb, if
terrain and passenger conditions permit, a maximum
of a 500 f.p.m. rate of descent should be planned.
Pressurized airplanes can plan for higher descent rates,
if desired.
In a descent, some airplanes require a minimum EGT,
or may have a minimum power setting or cylinder
head temperature to observe. In any case, combinations
of very low manifold pressure and high
r.p.m. settings are strongly discouraged by engine
manufacturers. If higher descent rates are necessary,
the pilot should consider extending partial flaps or
lowering the landing gear before retarding the power
excessively. The “descent” checklist should be initiated
upon leaving cruising altitude and completed before
arrival in the terminal area. Upon arrival in the terminal
area, pilots are encouraged to turn on their landing
and recognition lights when operating below
10,000 feet, day or night, and especially when
operating within 10 miles of any airport or in conditions
of reduced visibility.
Figure 12-7.Takeoff and climb profile.
Lift-off
Published VR or VLOF
if not Published,
VMC + 5 Knots
Positive Rate - Gear Up
Climb at VY
500 ft
1. Accelerate to Cruise Climb
2. Set Climb Power
3. Climb Checklist
Ch 12.qxd 5/7/04 9:54 AM Page 12-14
The traffic pattern and approach are typically flown at
somewhat higher indicated airspeeds in a multiengine
airplane contrasted to most single-engine airplanes.
The pilot may allow for this through an early start on
the “before landing” checklist. This provides time for
proper planning, spacing, and thinking well ahead of
the airplane. Many multiengine airplanes have partial
flap extension speeds above VFE, and partial flaps can
be deployed prior to traffic pattern entry. Normally, the
landing gear should be selected and confirmed down
when abeam the intended point of landing as the downwind
leg is flown.
The Federal Aviation Administration (FAA) recommends
a stabilized approach concept. To the greatest
extent practical, on final approach and within 500 feet
AGL, the airplane should be on speed, in trim, configured
for landing, tracking the extended centerline
of the runway, and established in a constant angle of
descent towards an aim point in the touchdown
zone. Absent unusual flight conditions, only minor
corrections will be required to maintain this approach
to the roundout and touchdown.
The final approach should be made with power and
at a speed recommended by the manufacturer; if a recommended
speed is not furnished, the speed should be
no slower than the single-engine best rate-of-climb
speed (VYSE) until short final with the landing assured,
but in no case less than critical engine-out minimum
control speed (VMC). Some multiengine pilots prefer
to delay full flap extension to short final with the landing
assured. This is an acceptable technique with appropriate
experience and familiarity with the airplane.
In the roundout for landing, residual power is gradually
reduced to idle. With the higher wing loading of
multiengine airplanes and with the drag from two
windmilling propellers, there will be minimal float.
Full stall landings are generally undesirable in twins. The
airplane should be held off as with a high performance
single-engine model, allowing touchdown of the main
wheels prior to a full stall.
Under favorable wind and runway conditions, the
nosewheel can be held off for best aerodynamic braking.
Even as the nosewheel is gently lowered to the
runway centerline, continued elevator back pressure
will greatly assist the wheel brakes in stopping the
airplane.
If runway length is critical, or with a strong crosswind,
or if the surface is contaminated with water, ice or
snow, it is undesirable to rely solely on aerodynamic
braking after touchdown. The full weight of the airplane
should be placed on the wheels as soon as
practicable. The wheel brakes will be more effective
than aerodynamic braking alone in decelerating the
airplane.
Once on the ground, elevator back pressure should be
used to place additional weight on the main wheels and
to add additional drag. When necessary, wing flap
retraction will also add additional weight to the wheels
and improve braking effectivity. Flap retraction during
the landing rollout is discouraged, however, unless
there is a clear, operational need. It should not be
accomplished as routine with each landing.
Some multiengine airplanes, particularly those of the
cabin class variety, can be flown through the roundout
and touchdown with a small amount of power. This is
an acceptable technique to prevent high sink rates and
to cushion the touchdown. The pilot should keep in
mind, however, that the primary purpose in landing is
to get the airplane down and stopped. This technique
should only be attempted when there is a generous
Approaching Traffic Pattern
1. Descent Checklist
2. Reduce to Traffic Pattern Airspeed and Altitude
Downwind
1. Flaps - Approach Position
2. Gear Down
3. Before Landing Checklist
Base Leg
1. Gear-Check Down
2. Check for Conflicting
Traffic
Final
1. Gear-Check Down
2. Flaps-Landing Position
Airspeed- 1.3 Vs0 or
Manufacturers Recommended
Figure 12-8. Normal two-engine approach and landing.
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12-16
margin of runway length. As propeller blast flows
directly over the wings, lift as well as thrust is produced.
The pilot should taxi clear of the runway as soon as
speed and safety permit, and then accomplish the “after
landing” checklist. Ordinarily, no attempt should be
made to retract the wing flaps or perform other checklist
duties until the airplane has been brought to a halt
when clear of the active runway. Exceptions to this
would be the rare operational needs discussed above,
to relieve the weight from the wings and place it on the
wheels. In these cases, AFM/POH guidance should be
followed. The pilot should not indiscriminately reach
out for any switch or control on landing rollout. An
inadvertent landing gear retraction while meaning to
retract the wing flaps may result.
CROSSWIND APPROACH
AND LANDING
The multiengine airplane is often easier to land in a
crosswind than a single-engine airplane due to its
higher approach and landing speed. In any event, the
principles are no different between singles and twins.
Prior to touchdown, the longitudinal axis must be
aligned with the runway centerline to avoid landing
gear side loads.
The two primary methods, crab and wing-low, are
typically used in conjunction with each other. As
soon as the airplane rolls out onto final approach, the
crab angle to track the extended runway centerline is
established. This is coordinated flight with adjustments
to heading to compensate for wind drift either
left or right. Prior to touchdown, the transition to a
sideslip is made with the upwind wing lowered and
opposite rudder applied to prevent a turn. The airplane
touches down on the landing gear of the upwind wing
first, followed by that of the downwind wing, and
then the nose gear. Follow-through with the flight
controls involves an increasing application of aileron
into the wind until full control deflection is reached.
The point at which the transition from the crab to the
sideslip is made is dependent upon pilot familiarity
with the airplane and experience. With high skill and
experience levels, the transition can be made during
the roundout just before touchdown. With lesser skill
and experience levels, the transition is made at
increasing distances from the runway. Some multiengine
airplanes (as some single-engine airplanes)
have AFM/POH limitations against slips in excess of
a certain time period; 30 seconds, for example. This is
to prevent engine power loss from fuel starvation as
the fuel in the tank of the lowered wing flows towards
the wingtip, away from the fuel pickup point. This
time limit must be observed if the wing-low method
is utilized.
Some multiengine pilots prefer to use differential
power to assist in crosswind landings. The asymmetrical
thrust produces a yawing moment little
different from that produced by the rudder. When
the upwind wing is lowered, power on the upwind
engine is increased to prevent the airplane from
turning. This alternate technique is completely
acceptable, but most pilots feel they can react to
changing wind conditions quicker with rudder and
aileron than throttle movement. This is especially
true with turbocharged engines where the throttle
response may lag momentarily. The differential
power technique should be practiced with an
instructor familiar with it before being attempted
alone.
SHORT-FIELD TAKEOFF AND CLIMB
The short-field takeoff and climb differs from the
normal takeoff and climb in the airspeeds and initial
climb profile. Some AFM/POHs give separate
short-field takeoff procedures and performance
charts that recommend specific flap settings and airspeeds.
Other AFM/POHs do not provide separate
short-field procedures. In the absence of such specific
procedures, the airplane should be operated only as
recommended in the AFM/POH. No operations should
be conducted contrary to the recommendations in the
AFM/POH.
On short-field takeoffs in general, just after rotation
and lift-off, the airplane should be allowed to accelerate
to VX, making the initial climb over obstacles at
VX and transitioning to VY as obstacles are cleared.
Figure 12-9. Short-field takeoff and climb.
VX
VY
50 ft
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When partial flaps are recommended for short-field
takeoffs, many light-twins have a strong tendency to
become airborne prior to VMC plus 5 knots. Attempting
to prevent premature lift-off with forward elevator
pressure results in wheelbarrowing. To prevent this,
allow the airplane to become airborne, but only a few
inches above the runway. The pilot should be prepared
to promptly abort the takeoff and land in the event of
engine failure on takeoff with landing gear and flaps
extended at airspeeds below VX.
Engine failure on takeoff, particularly with obstructions,
is compounded by the low airspeeds and steep
climb attitudes utilized in short-field takeoffs. VX and
VXSE are often perilously close to VMC, leaving scant
margin for error in the event of engine failure as VXSE
is assumed. If flaps were used for takeoff, the engine
failure situation becomes even more critical due to the
additional drag incurred. If VX is less than 5 knots
higher than VMC, give strong consideration to reducing
useful load or using another runway in order to
increase the takeoff margins so that a short-field
technique will not be required.
SHORT-FIELD APPROACH
AND LANDING
The primary elements of a short-field approach and
landing do not differ significantly from a normal
approach and landing. Many manufacturers do not
publish short-field landing techniques or performance
charts in the AFM/POH. In the absence of specific
short-field approach and landing procedures, the
airplane should be operated as recommended in the
AFM/POH. No operations should be conducted
contrary to the AFM/POH recommendations.
The emphasis in a short-field approach is on configuration
(full flaps), a stabilized approach with a constant
angle of descent, and precise airspeed control. As part
of a short-field approach and landing procedure,
some AFM/POHs recommend a slightly slower than
normal approach airspeed. If no such slower speed is
published, use the AFM/POH-recommended normal
approach speed.
Full flaps are used to provide the steepest approach
angle. If obstacles are present, the approach should be
planned so that no drastic power reductions are
required after they are cleared. The power should be
smoothly reduced to idle in the roundout prior to
touchdown. Pilots should keep in mind that the propeller
blast blows over the wings, providing some lift
in addition to thrust. Significantly reducing power just
after obstacle clearance usually results in a sudden,
high sink rate that may lead to a hard landing.
After the short-field touchdown, maximum stopping
effort is achieved by retracting the wing flaps, adding
back pressure to the elevator/stabilator, and applying
heavy braking. However, if the runway length permits,
the wing flaps should be left in the extended position
until the airplane has been stopped clear of the runway.
There is always a significant risk of retracting the landing
gear instead of the wing flaps when flap retraction
is attempted on the landing rollout.
Landing conditions that involve either a short-field,
high-winds or strong crosswinds are just about the only
situations where flap retraction on the landing rollout
should be considered. When there is an operational
need to retract the flaps just after touchdown, it must
be done deliberately, with the flap handle positively
identified before it is moved.
GO-AROUND
When the decision to go around is made, the throttles
should be advanced to takeoff power. With adequate
airspeed, the airplane should be placed in a climb pitch
attitude. These actions, which are accomplished
simultaneously, will arrest the sink rate and place the
airplane in the proper attitude for transition to a
climb. The initial target airspeed will be VY, or VX if
obstructions are present. With sufficient airspeed, the
flaps should be retracted from full to an intermediate
position and the landing gear retracted when there is
a positive rate of climb and no chance of runway
contact. The remaining flaps should then be
retracted.
Figure 12-10. Go-around procedure.
Retract Remaining
Flaps
Positive Rate
of Climb, Retract
Gear, Climb
at VY
500'
Cruise Climb
Timely Decision to
Make Go-Around Apply Max Power
Adjust Pitch Attitude
to Arrest Sink Rate
Flaps to
Intermediate
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12-18
If the go-around was initiated due to conflicting traffic
on the ground or aloft, the pilot should maneuver to the
side, so as to keep the conflicting traffic in sight. This
may involve a shallow bank turn to offset and then parallel
the runway/landing area.
If the airplane was in trim for the landing approach
when the go-around was commenced, it will soon require
a great deal of forward elevator/stabilator pressure as the
airplane accelerates away in a climb. The pilot should
apply appropriate forward pressure to maintain the
desired pitch attitude. Trim should be commenced immediately.
The “balked landing” checklist should be
reviewed as work load permits.
Flaps should be retracted before the landing gear for
two reasons. First, on most airplanes, full flaps produce
more drag than the extended landing gear. Secondly,
the airplane will tend to settle somewhat with flap
retraction, and the landing gear should be down in the
event of an inadvertent, momentary touchdown.
Many multiengine airplanes have a landing gear retraction
speed significantly less than the extension speed.
Care should be exercised during the go-around not to
exceed the retraction speed. If the pilot desires to
return for a landing, it is essential to re-accomplish the
entire “before landing” checklist. An interruption to a
pilot’s habit patterns, such as a go-around, is a classic
scenario for a subsequent gear up landing.
The preceding discussion of go-arounds assumes that
the maneuver was initiated from normal approach
speeds or faster. If the go-around was initiated from a
low airspeed, the initial pitch up to a climb attitude must
be tempered with the necessity of maintaining adequate
flying speed throughout the maneuver. Examples of
where this applies include go-arounds initiated from the
landing roundout or recovery from a bad bounce as well
as a go-around initiated due to an inadvertent approach
to a stall. The first priority is always to maintain control
and obtain adequate flying speed. A few moments of
level or near level flight may be required as the airplane
accelerates up to climb speed.
REJECTED TAKEOFF
Atakeoff can be rejected for the same reasons a takeoff
in a single-engine airplane would be rejected. Once the
decision to reject a takeoff is made, the pilot should
promptly close both throttles and maintain directional
control with the rudder, nosewheel steering, and
brakes. Aggressive use of rudder, nosewheel steering,
and brakes may be required to keep the airplane on
the runway. Particularly, if an engine failure is not
immediately recognized and accompanied by
prompt closure of both throttles. However, the primary
objective is not necessarily to stop the airplane
in the shortest distance, but to maintain control of
the airplane as it decelerates. In some situations, it
may be preferable to continue into the overrun area
under control, rather than risk directional control loss,
landing gear collapse, or tire/brake failure in an
attempt to stop the airplane in the shortest possible
distance.
ENGINE FAILURE AFTER LIFT-OFF
A takeoff or go-around is the most critical time to suffer
an engine failure. The airplane will be slow, close
to the ground, and may even have landing gear and
flaps extended. Altitude and time will be minimal.
Until feathered, the propeller of the failed engine will
be windmilling, producing a great deal of drag and
yawing tendency. Airplane climb performance will be
marginal or even non-existent, and obstructions may
lie ahead. Add the element of surprise and the need for
a plan of action before every takeoff is obvious.
With loss of an engine, it is paramount to maintain
airplane control and comply with the manufacturer’s
recommended emergency procedures. Complete failure
of one engine shortly after takeoff can be broadly
categorized into one of three following scenarios.
1. Landing gear down. If the
engine failure occurs prior to selecting the landing
gear to the UP position, close both throttles
and land on the remaining runway or overrun.
Depending upon how quickly the pilot reacts to
the sudden yaw, the airplane may run off the
side of the runway by the time action is taken.
There are really no other practical options. As
discussed earlier, the chances of maintaining
directional control while retracting the flaps (if
extended), landing gear, feathering the propeller,
and accelerating are minimal. On some airplanes
with a single-engine-driven hydraulic pump,
failure of that engine means the only way to
raise the landing gear is to allow the engine to
windmill or to use a hand pump. This is not a
viable alternative during takeoff.
2. Landing gear control selected up, singleengine
climb performance inadequate.
When operating near or above
the single-engine ceiling and an engine failure is
experienced shortly after lift-off, a landing must
be accomplished on whatever essentially lies
ahead. There is also the option of continuing
ahead, in a descent at VYSE with the remaining
engine producing power, as long as the pilot
is not tempted to remain airborne beyond the
airplane’s performance capability. Remaining
airborne, bleeding off airspeed in a futile
attempt to maintain altitude is almost invariably
fatal. Landing under control is paramount. The
greatest hazard in a single-engine takeoff is
attempting to fly when it is not within the per-
Ch 12.qxd 5/7/04 9:54 AM Page 12-18
12-19
formance capability of the airplane to do so. An
accident is inevitable.
Analysis of engine failures on takeoff reveals a very
high success rate of off-airport engine inoperative
landings when the airplane is landed under control.
Analysis also reveals a very high fatality rate in stallspin
accidents when the pilot attempts flight beyond
the performance capability of the airplane.
As mentioned previously, if the airplane’s landing gear
retraction mechanism is dependent upon hydraulic
pressure from a certain engine-driven pump, failure
of that engine can mean a loss of hundreds of feet of
altitude as the pilot either windmills the engine to
provide hydraulic pressure to raise the gear or raises
it manually with a backup pump.
3. Landing gear control selected up, singleengine
climb performance adequate. [Figure
12-13] If the single-engine rate of climb is
adequate, the procedures for continued flight
should be followed. There are four areas of
concern: control, configuration, climb, and
checklist.
• CONTROL— The first consideration following
engine failure during takeoff is control of the airplane.
Upon detecting an engine failure, aileron
should be used to bank the airplane and rudder
pressure applied, aggressively if necessary, to
counteract the yaw and roll from asymmetrical
thrust. The control forces, particularly on the
rudder, may be high. The pitch attitude for VYSE
will have to be lowered from that of VY.
Figure 12-11. Engine failure on takeoff, landing gear down.
If Engine Failure Occurs at
or Before Lift-off, Abort the
Takeoff.
If Failure of Engine Occurs After Lift-off:
1. Maintain Directional Control
2. Close Both Throttles
Figure 12-12. Engine failure on takeoff, inadequate climb performance.
Liftoff
Engine Failure
Descend at VYSE
Land Under Control
On or Off Runway
Over Run Area
Ch 12.qxd 5/7/04 9:54 AM Page 12-19
At least 5° of bank should be used, if necessary,
to stop the yaw and maintain directional control.
This initial bank input is held only momentarily,
just long enough to establish or ensure directional
control. Climb performance suffers when
bank angles exceed approximately 2 or 3°, but
obtaining and maintaining VYSE and directional
control are paramount. Trim should be adjusted
to lower the control forces.
• CONFIGURATION—The memory items from
the “engine failure after takeoff” checklist
should be promptly executed to
configure the airplane for climb. The specific
procedures to follow will be found in the
AFM/POH and checklist for the particular airplane.
Most will direct the pilot to assume VYSE,
set takeoff power, retract the flaps and landing
gear, identify, verify, and feather the failed
engine. (On some airplanes, the landing gear is
to be retracted before the flaps.)
The “identify” step is for the pilot to initially
identify the failed engine. Confirmation on the
engine gauges may or may not be possible,
depending upon the failure mode. Identification
should be primarily through the control inputs
required to maintain straight flight, not the
engine gauges. The “verify” step directs the pilot
to retard the throttle of the engine thought to have
failed. No change in performance when the suspected
throttle is retarded is verification that the
correct engine has been identified as failed. The
corresponding propeller control should be
brought fully aft to feather the engine.
• CLIMB—As soon as directional control is established
and the airplane configured for climb, the
bank angle should be reduced to that producing
best climb performance. Without specific
guidance for zero sideslip, a bank of 2° and
one-third to one-half ball deflection on the
slip/skid indicator is suggested. VYSE is maintained
with pitch control. As turning flight
reduces climb performance, climb should be
made straight ahead, or with shallow turns to
avoid obstacles, to an altitude of at least 400
feet AGL before attempting a return to
the airport.
Obstruction Clearance
Altitude or Above
At 500' or Obstruction Clearance Altitude:
7. Engine Failure Checklist
Circle and Land
3. Drag - Reduce - Gear, Flaps
4. Identify - Inoperative Engine
5. Verify - Inoperative Engine
6. Feather - Inoperative Engine
If Failure of Engine Occurs After Liftoff:
1. Maintain Directional Control - VYSE,
Heading, Bank into Operating Engine
2. Power - Increase or Set for Takeoff
Figure 12-13. Landing gear up—adequate climb performance.
Figure 12-14.Typical “engine failure after takeoff” emergency
checklist.
12-20
ENGINE FAILURE AFTER TAKEOFF
Airspeed . . . . . . . . . . . . . . . . . . . Maintain VYSE
Mixtures . . . . . . . . . . . . . . . . . . . RICH
Propellers . . . . . . . . . . . . . . . . . .HIGH RPM
Throttles . . . . . . . . . . . . . . . . . . . FULL POWER
Flaps . . . . . . . . . . . . . . . . . . . . . . . UP
Landing Gear . . . . . . . . . . . . . . . UP
Identify . . . . . . . . . . . . . . . . . . . . Determine failed
engine
Verify Close throttle of
failed engine
Propeller . . . . . . . . . . . . . . . . . . . FEATHER
Trim T abs . . . . . . . . . . . . . . . . . . . ADJUST
Failed Engine . . . . . . . . . . . . . . . SECURE
As soon as practical . . . . . . . . . . LAND
Bold - faced items require immediate action and
are to be accomplished fro m mem ory.
. . . . . . . . . . . . . . . . . . . . . . . .
Ch 12.qxd 5/7/04 9:55 AM Page 12-20
12-21
• CHECKLIST—Having accomplished the
memory items from the “engine failure after
takeoff” checklist, the printed copy should be
reviewed as time permits. The “securing failed
engine” checklist should then be
accomplished. Unless the pilot suspects an
engine fire, the remaining items should be
accomplished deliberately and without undue
haste. Airplane control should never be sacrificed
to execute the remaining checklists. The priority
items have already been accomplished from
memory.
Figure 12-15. Typical “securing failed engine” emergency
checklist.
Other than closing the cowl flap of the failed engine,
none of these items, if left undone, adversely affects
airplane climb performance. There is a distinct possibility
of actuating an incorrect switch or control if the procedure
is rushed. The pilot should concentrate on flying
the airplane and extracting maximum performance. If
ATC facilities are available, an emergency should be
declared.
The memory items in the “engine failure after takeoff”
checklist may be redundant with the airplane’s existing
configuration. For example, in the third takeoff scenario,
the gear and flaps were assumed to already be retracted,
yet the memory items included gear and flaps. This is
not an oversight. The purpose of the memory items is
to either initiate the appropriate action or to confirm
that a condition exists. Action on each item may not
be required in all cases. The memory items also
apply to more than one circumstance. In an engine
failure from a go-around, for example, the landing
gear and flaps would likely be extended when the
failure occurred.
The three preceding takeoff scenarios all include the
landing gear as a key element in the decision to land or
continue. With the landing gear selector in the DOWN
position, for example, continued takeoff and climb is
not recommended. This situation, however, is not justification
to retract the landing gear the moment the
airplane lifts off the surface on takeoff as a normal
procedure. The landing gear should remain selected
down as long as there is usable runway or overrun
available to land on. The use of wing flaps for takeoff
virtually eliminates the likelihood of a single-engine
climb until the flaps are retracted.
There are two time-tested memory aids the pilot may
find useful in dealing with engine-out scenarios. The
first, “Dead foot–dead engine” is used to assist in identifying
the failed engine. Depending on the failure
mode, the pilot won’t be able to consistently identify
the failed engine in a timely manner from the engine
gauges. In maintaining directional control, however,
rudder pressure will be exerted on the side (left or right)
of the airplane with the operating engine. Thus, the
“dead foot” is on the same side as the “dead engine.”
Variations on this saying include “Idle foot–idle
engine” and “Working foot–working engine.”
The second memory aid has to do with climb performance.
The phrase “Raise the dead” is a reminder that
the best climb performance is obtained with a very
shallow bank, about 2° toward the operating engine.
Therefore, the inoperative, or “dead” engine should be
“raised” with a very slight bank.
Not all engine power losses are complete failures.
Sometimes the failure mode is such that partial power
may be available. If there is a performance loss when
the throttle of the affected engine is retarded, the pilot
should consider allowing it to run until altitude and airspeed
permit safe single-engine flight, if this can be
done without compromising safety. Attempts to save a
malfunctioning engine can lead to a loss of the entire
airplane.
ENGINE FAILURE DURING FLIGHT
Engine failures well above the ground are handled
differently than those occurring at lower speeds and
altitudes. Cruise airspeed allows better airplane control,
and altitude may permit time for a possible
diagnosis and remedy of the failure. Maintaining
airplane control, however, is still paramount.
Airplanes have been lost at altitude due to apparent
fixation on the engine problem to the detriment of
flying the airplane.
Not all engine failures or malfunctions are catastrophic
in nature (catastrophic meaning a major mechanical
failure that damages the engine and precludes further
engine operation). Many cases of power loss are
related to fuel starvation, where restoration of power
may be made with the selection of another tank. An
orderly inventory of gauges and switches may reveal
the problem. Carburetor heat or alternate air can be
selected. The affected engine may run smoothly on just
one magneto or at a lower power setting. Altering the
SECURING FAILED ENGINE
Mixture . . . . . . . . . . . . . . . . . . . . . . . IDLE CUT OFF
Magnetos . . . . . . . . . . . . . . . . . . . . . OFF
Alternator . . . . . . . . . . . . . . . . . . . . . OFF
Cowl Flap . . . . . . . . . . . . . . . . . . . . . CLOSE
Boost Pump . . . . . . . . . . . . . . . . . . . .OFF
Fuel Selector . . . . . . . . . . . . . . . . . . OFF
Prop Sync . . . . . . . . . . . . . . . . . . . . . OFF
Electrical Load . . . . . . . . . . . . . . . . . . . Reduce
Crossfeed . . . . . . . . . . . . . . . . . . . . . Consider
Ch 12.qxd 5/7/04 9:55 AM Page 12-21
12-22
mixture may help. If fuel vapor formation is suspected,
fuel boost pump operation may be used to eliminate
flow and pressure fluctuations.
Although it is a natural desire among pilots to save an
ailing engine with a precautionary shutdown, the
engine should be left running if there is any doubt as to
needing it for further safe flight. Catastrophic failure
accompanied by heavy vibration, smoke, blistering
paint, or large trails of oil, on the other hand, indicate
a critical situation. The affected engine should be
feathered and the “securing failed engine” checklist
completed. The pilot should divert to the nearest suitable
airport and declare an emergency with ATC for
priority handling.
Fuel crossfeed is a method of getting fuel from a tank
on one side of the airplane to an operating engine on
the other. Crossfeed is used for extended single-engine
operation. If a suitable airport is close at hand, there is
no need to consider crossfeed. If prolonged flight on a
single-engine is inevitable due to airport non-availability,
then crossfeed allows use of fuel that would
otherwise be unavailable to the operating engine. It
also permits the pilot to balance the fuel consumption
to avoid an out-of-balance wing heaviness.
AFM/POH procedures for crossfeed vary widely.
Thorough fuel system knowledge is essential if crossfeed
is to be conducted. Fuel selector positions and fuel
boost pump usage for crossfeed differ greatly among
multiengine airplanes. Prior to landing, crossfeed
should be terminated and the operating engine returned
to its main tank fuel supply.
If the airplane is above its single-engine absolute
ceiling at the time of engine failure, it will slowly
lose altitude. The pilot should maintain VYSE to minimize
the rate of altitude loss. This “drift down” rate
will be greatest immediately following the failure
and will decrease as the single-engine ceiling is
approached. Due to performance variations caused
by engine and propeller wear, turbulence, and pilot
technique, the airplane may not maintain altitude
even at its published single-engine ceiling. Any further
rate of sink, however, would likely be modest.
An engine failure in a descent or other low power
setting can be deceiving. The dramatic yaw and performance
loss will be absent. At very low power
settings, the pilot may not even be aware of a failure.
If a failure is suspected, the pilot should advance both
engine mixtures, propellers, and throttles significantly,
to the takeoff settings if necessary, to correctly identify
the failed engine. The power on the operative engine
can always be reduced later.
ENGINE INOPERATIVE APPROACH
AND LANDING
The approach and landing with one engine inoperative
is essentially the same as a two-engine approach and
landing. The traffic pattern should be flown at similar
altitudes, airspeeds, and key positions as a two-engine
approach. The differences will be the reduced power
available and the fact that the remaining thrust is
asymmetrical. A higher-than-normal power setting
will be necessary on the operative engine.
With adequate airspeed and performance, the landing
gear can still be extended on the downwind leg. In
which case it should be confirmed DOWN no later
than abeam the intended point of landing. Performance
permitting, initial extension of wing flaps (10°, typically)
and a descent from pattern altitude can also be
initiated on the downwind leg. The airspeed should be
no slower than VYSE. The direction of the traffic pattern,
and therefore the turns, is of no consequence as
far as airplane controllability and performance are
concerned. It is perfectly acceptable to make turns
toward the failed engine.
On the base leg, if performance is adequate, the flaps
may be extended to an intermediate setting (25°, typically).
If the performance is inadequate, as measured
by a decay in airspeed or high sink rate, delay further
flap extension until closer to the runway. VYSE is still
the minimum airspeed to maintain.
On final approach, a normal, 3° glidepath to a landing
is desirable. VASI or other vertical path lighting aids
should be utilized if available. Slightly steeper
approaches may be acceptable. However, a long, flat,
low approach should be avoided. Large, sudden power
applications or reductions should also be avoided.
Maintain VYSE until the landing is assured, then slow
to 1.3 VSO or the AFM/POH recommended speed. The
final flap setting may be delayed until the landing is
assured, or the airplane may be landed with partial
flaps.
The airplane should remain in trim throughout. The
pilot must be prepared, however, for a rudder trim
change as the power of the operating engine is reduced
to idle in the roundout just prior to touchdown. With
drag from only one windmilling propeller, the airplane
will tend to float more than on a two-engine approach.
Precise airspeed control therefore is essential, especially
when landing on a short, wet and/or slippery surface.
Some pilots favor resetting the rudder trim to neutral
on final and compensating for yaw by holding rudder
pressure for the remainder of the approach. This eliminates
the rudder trim change close to the ground as
Ch 12.qxd 5/7/04 9:55 AM Page 12-22
the throttle is closed during the roundout for landing.
This technique eliminates the need for groping for the
rudder trim and manipulating it to neutral during final
approach, which many pilots find to be highly distracting.
AFM/POH recommendations or personal
preference should be used.
Single-engine go-arounds must be avoided. As a practical
matter in single-engine approaches, once the airplane
is on final approach with landing gear and flaps
extended, it is committed to land. If not on the intended
runway, then on another runway, a taxiway, or grassy
infield. The light-twin does not have the performance
to climb on one engine with landing gear and flaps
extended. Considerable altitude will be lost while
maintaining VYSE and retracting landing gear and
flaps. Losses of 500 feet or more are not unusual. If the
landing gear has been lowered with an alternate means
of extension, retraction may not be possible, virtually
negating any climb capability.
ENGINE INOPERATIVE
FLIGHT PRINCIPLES
Best single-engine climb performance is obtained at
VYSE with maximum available power and minimum
drag. After the flaps and landing gear have been
retracted and the propeller of the failed engine feathered,
a key element in best climb performance is
minimizing sideslip.
With a single-engine airplane or a multiengine airplane
with both engines operative, sideslip is eliminated
when the ball of the turn and bank instrument is centered.
This is a condition of zero sideslip, and the
airplane is presenting its smallest possible profile to
the relative wind. As a result, drag is at its minimum.
Pilots know this as coordinated flight.
In a multiengine airplane with an inoperative engine,
the centered ball is no longer the indicator of zero
sideslip due to asymmetrical thrust. In fact, there is no
instrument at all that will directly tell the pilot the
flight conditions for zero sideslip. In the absence of a
yaw string, minimizing sideslip is a matter of placing
the airplane at a predetermined bank angle and ball
position. The AFM/POH performance charts for single-
engine flight were determined at zero sideslip. If
this performance is even to be approximated, the zero
sideslip technique must be utilized.
There are two different control inputs that can be used
to counteract the asymmetrical thrust of a failed
engine: (1) yaw from the rudder, and (2) the horizontal
component of lift that results from bank with the
ailerons. Used individually, neither is correct. Used
together in the proper combination, zero sideslip and
best climb performance are achieved.
Three different scenarios of airplane control inputs are
presented below. Neither of the first two is correct.
They are presented to illustrate the reasons for the zero
sideslip approach to best climb performance.
1. Engine inoperative flight with wings level and
ball centered requires large rudder input towards
the operative engine. The result is
a moderate sideslip towards the inoperative
engine. Climb performance will be reduced by
the moderate sideslip. With wings level, VMC will
be significantly higher than published as there is
no horizontal component of lift available to help
the rudder combat asymmetrical thrust.
Figure 12-16. Wings level engine-out flight.
Rudder Force
Yaw
String
Fin Effect
Due to Sideslip
Slipstream
Wings level, ball centered, airplane slips toward dead engine.
Results: high drag, large control surface deflections required,
and rudder and fin in opposition due to sideslip.
12-23
Ch 12.qxd 5/7/04 9:55 AM Page 12-23
2. Engine inoperative flight using ailerons alone
requires an 8 - 10° bank angle towards the operative
engine. This assumes no
rudder input. The ball will be displaced well
towards the operative engine. The result is a
large sideslip towards the operative engine.
Climb performance will be greatly reduced by
the large sideslip.
3. Rudder and ailerons used together in the proper
combination will result in a bank of approximately
2° towards the operative engine. The
ball will be displaced approximately one-third
to one-half towards the operative engine. The
result is zero sideslip and maximum climb performance.
Any attitude other
than zero sideslip increases drag, decreasing
performance. VMC under these circumstances
will be higher than published, as less than the
5° bank certification limit is employed.
The precise condition of zero sideslip (bank angle and
ball position) varies slightly from model to model, and
with available power and airspeed. If the airplane is
not equipped with counter-rotating propellers, it will
also vary slightly with the engine failed due to P-factor.
The foregoing zero sideslip recommendations apply to
Yaw
String
Excess bank toward operating engine, no rudder input.
Result: large sideslip toward operating engine and greatly
reduced climb performance.
12-24
Rudder Force
Yaw
String
Bank toward operating engine, no sideslip. Results: much
lower drag and smaller control surface deflections.
Figure 12-17. Excessive bank engine-out flight. Figure 12-18. Zero sideslip engine-out flight.
Ch 12.qxd 5/7/04 9:55 AM Page 12-24
12-25
reciprocating engine multiengine airplanes flown at
VYSE with the inoperative engine feathered. The zero
sideslip ball position for straight flight is also the zero
sideslip position for turning flight.
When bank angle is plotted against climb performance
for a hypothetical twin, zero sideslip results in the best
(however marginal) climb performance or the least rate
of descent. Zero bank (all rudder to counteract yaw)
degrades climb performance as a result of moderate
sideslip. Using bank angle alone (no rudder) severely
degrades climb performance as a result of a large
sideslip.
The actual bank angle for zero sideslip varies among
airplanes from one and one-half to two and one-half
degrees. The position of the ball varies from one-third
to one-half of a ball width from instrument center.
For any multiengine airplane, zero sideslip can be confirmed
through the use of a yaw string. A yaw string is
a piece of string or yarn approximately 18 to 36 inches
in length, taped to the base of the windshield, or to the
nose near the windshield, along the airplane centerline.
In two-engine coordinated flight, the relative wind will
cause the string to align itself with the longitudinal axis
of the airplane, and it will position itself straight up the
center of the windshield. This is zero sideslip.
Experimentation with slips and skids will vividly display
the location of the relative wind. Adequate altitude and
flying speed must be maintained while accomplishing
these maneuvers.
With an engine set to zero thrust (or feathered) and the
airplane slowed to VYSE, a climb with maximum power
on the remaining engine will reveal the precise bank
angle and ball deflection required for zero sideslip and
best climb performance. Zero sideslip will again be
indicated by the yaw string when it aligns itself vertically
on the windshield. There will be very minor
changes from this attitude depending upon the
engine failed (with noncounter-rotating propellers),
power available, airspeed and weight; but without
more sensitive testing equipment, these changes are
difficult to detect. The only significant difference
would be the pitch attitude required to maintain VYSE
under different density altitude, power available, and
weight conditions.
If a yaw string is attached to the airplane at the time
of a VMC demonstration, it will be noted that VMC
occurs under conditions of sideslip. VMC was not
determined under conditions of zero sideslip during
aircraft certification and zero sideslip is not part of a
VMC demonstration for pilot certification.
To review, there are two different sets of bank angles
used in one-engine-inoperative flight.
• To maintain directional control of a multiengine
airplane suffering an engine failure at low speeds
(such as climb), momentarily bank at least 5°,
and a maximum of 10° towards the operative
engine as the pitch attitude for VYSE is set. This
maneuver should be instinctive to the proficient
multiengine pilot and take only 1 to 2 seconds to
attain. It is held just long enough to assure directional
control as the pitch attitude for VYSE is
assumed.
• To obtain the best climb performance, the airplane
must be flown at VYSE and zero sideslip,
with the failed engine feathered and maximum
available power from the operating engine. Zero
sideslip is approximately 2° of bank toward the
operating engine and a one-third to one-half ball
deflection, also toward the operating engine. The
precise bank angle and ball position will vary
somewhat with make and model and power
available. If above the airplane’s single-engine
ceiling, this attitude and configuration will result
in the minimum rate of sink.
In OEI flight at low altitudes and airspeeds such as the
initial climb after takeoff, pilots must operate the airplane
so as to guard against the three major accident factors:
(1) loss of directional control, (2) loss of performance,
and (3) loss of flying speed. All have equal potential to
be lethal. Loss of flying speed will not be a factor,
however, when the airplane is operated with due regard
for directional control and performance.
SLOW FLIGHT
There is nothing unusual about maneuvering during
slow flight in a multiengine airplane. Slow flight may
be conducted in straight-and-level flight, turns, in the
clean configuration, landing configuration, or at any
other combination of landing gear and flaps. Pilots
should closely monitor cylinder head and oil temperatures
during slow flight. Some high performance
multiengine airplanes tend to heat up fairly quickly
under some conditions of slow flight, particularly in
the landing configuration.
Simulated engine failures should not be conducted during
slow flight. The airplane will be well below VSSE
and very close to VMC. Stability, stall warning or stall
avoidance devices should not be disabled while
maneuvering during slow flight.
STALLS
Stall characteristics vary among multiengine airplanes
just as they do with single-engine airplanes, and
therefore, it is important to be familiar with them. The
application of power upon stall recovery, however,
has a significantly greater effect during stalls in a
Ch 12.qxd 5/7/04 9:55 AM Page 12-25
12-26
twin than a single-engine airplane. In the twin, an
application of power blows large masses of air from
the propellers directly over the wings, producing a
significant amount of lift in addition to the expected
thrust. The multiengine airplane, particularly at light
operating weights, typically has a higher thrust-toweight
ratio, making it quicker to accelerate out of a
stalled condition.
In general, stall recognition and recovery training in
twins is performed similar to any high performance
single-engine airplane. However, for twins, all stall
maneuvers should be planned so as to be completed at
least 3,000 feet AGL.
Single-engine stalls or stalls with significantly more
power on one engine than the other should not be
attempted due to the likelihood of a departure from
controlled flight and possible spin entry. Similarly,
simulated engine failures should not be performed during
stall entry and recovery.
POWER-OFF STALLS
(APPROACH AND LANDING)
Power-off stalls are practiced to simulate typical
approach and landing scenarios. To initiate a power-off
stall maneuver, the area surrounding the airplane
should first be cleared for possible traffic. The airplane
should then be slowed and configured for an approach
and landing. Astabilized descent should be established
(approximately 500 f.p.m.) and trim adjusted. The pilot
should then transition smoothly from the stabilized
descent attitude, to a pitch attitude that will induce a
stall. Power is reduced further during this phase, and
trimming should cease at speeds slower than takeoff.
When the airplane reaches a stalled condition, the
recovery is accomplished by simultaneously reducing
the angle of attack with coordinated use of the flight
controls and smoothly applying takeoff or specified
power. The flap setting should be reduced from full to
approach, or as recommended by the manufacturer.
Then with a positive rate of climb, the landing gear is
selected up. The remaining flaps are then retracted as a
climb has commenced. This recovery process should
be completed with a minimum loss of altitude, appropriate
to the aircraft characteristics.
The airplane should be accelerated to VX (if simulated
obstacles are present) or VY during recovery and climb.
Considerable forward elevator/stabilator pressure will
be required after the stall recovery as the airplane accelerates
to VX or VY. Appropriate trim input should be
anticipated.
Power-off stalls may be performed with wings level, or
from shallow and medium banked turns. When recovering
from a stall performed from turning flight, the
angle of attack should be reduced prior to leveling the
wings. Flight control inputs should be coordinated.
It is usually not advisable to execute full stalls in
multiengine airplanes because of their relatively high
wing loading. Stall training should be limited to
approaches to stalls and when a stall condition occurs.
Recoveries should be initiated at the onset, or decay of
control effectiveness, or when the first physical
indication of the stall occurs.
POWER-ON STALLS
(TAKEOFF AND DEPARTURE)
Power-on stalls are practiced to simulate typical
takeoff scenarios. To initiate a power-on stall
maneuver, the area surrounding the airplane should
always be cleared to look for potential traffic. The
airplane is slowed to the manufacturer’s recommended
lift-off speed. The airplane should be configured in the
takeoff configuration. Trim should be adjusted for this
speed. Engine power is then increased to that recommended
in the AFM/POH for the practice of power-on
stalls. In the absence of a recommended setting, use
approximately 65 percent of maximum available
power while placing the airplane in a pitch attitude that
will induce a stall. Other specified (reduced) power
settings may be used to simulate performance at higher
gross weights and density altitudes.
When the airplane reaches a stalled condition, the
recovery is made by simultaneously lowering the
angle of attack with coordinated use of the flight
controls and applying power as appropriate.
However, if simulating limited power available for
high gross weight and density altitude situations, the
power during the recovery should be limited to that
specified. The recovery should be completed with a
minimum loss of altitude, appropriate to aircraft characteristics.
The landing gear should be retracted when a positive
rate of climb is attained, and flaps retracted, if flaps
were set for takeoff. The target airspeed on recovery is
VX if (simulated) obstructions are present, or VY. The
pilot should anticipate the need for nosedown trim as
the airplane accelerates to VX or VY after recovery.
Power-on stalls may be performed from straight flight
or from shallow and medium banked turns. When
recovering from a power-on stall performed from turning
flight, the angle of attack should be reduced prior
to leveling the wings, and the flight control inputs
should be coordinated.
SPIN AWARENESS
No multiengine airplane is approved for spins, and
their spin recovery characteristics are generally very
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12-27
poor. It is therefore necessary to practice spin avoidance
and maintain a high awareness of situations that
can result in an inadvertent spin.
In order to spin any airplane, it must first be stalled. At
the stall, a yawing moment must be introduced. In a
multiengine airplane, the yawing moment may be
generated by rudder input or asymmetrical thrust. It
follows, then, that spin awareness be at its greatest
during VMC demonstrations, stall practice, slow
flight, or any condition of high asymmetrical thrust,
particularly at low speed/high angle of attack. Singleengine
stalls are not part of any multiengine training
curriculum.
A situation that may inadvertently degrade into a spin
entry is a simulated engine failure introduced at an
inappropriately low speed. No engine failure should
ever be introduced below safe, intentional one-engineinoperative
speed (VSSE). If no VSSE is published, use
VYSE. The “necessity” of simulating engine failures
at low airspeeds is erroneous. Other than training
situations, the multiengine airplane is only operated
below VSSE for mere seconds just after lift-off or
during the last few dozen feet of altitude in preparation
for landing.
For spin avoidance when practicing engine failures,
the flight instructor should pay strict attention to the
maintenance of proper airspeed and bank angle as the
student executes the appropriate procedure. The
instructor should also be particularly alert during stall
and slow flight practice. Forward center-of-gravity
positions result in favorable stall and spin avoidance
characteristics, but do not eliminate the hazard.
When performing a VMC demonstration, the instructor
should also be alert for any sign of an impending stall.
The student may be highly focused on the directional
control aspect of the maneuver to the extent that
impending stall indications go unnoticed. If a VMC
demonstration cannot be accomplished under existing
conditions of density altitude, it may, for training purposes,
be done utilizing the rudder blocking technique
described in the following section.
As very few twins have ever been spin-tested (none
are required to), the recommended spin recovery
techniques are based only on the best information
available. The departure from controlled flight may
be quite abrupt and possibly disorienting. The direction
of an upright spin can be confirmed from the turn
needle or the symbolic airplane of the turn coordinator,
if necessary. Do not rely on the ball position or other
instruments.
If a spin is entered, most manufacturers recommend
immediately retarding both throttles to idle, applying
full rudder opposite the direction of rotation, and
applying full forward elevator/stabilator pressure (with
ailerons neutral). These actions should be taken as near
simultaneously as possible. The controls should then
be held in that position. Recovery, if possible, will take
considerable altitude. The longer the delay from entry
until taking corrective action, the less likely that recovery
will be successful.
ENGINE INOPERATIVE—LOSS OF
DIRECTIONAL CONTROL
DEMONSTRATION
An engine inoperative—loss of directional control
demonstration, often referred to as a “VMC demonstration,”
is a required task on the practical test for a
multiengine class rating. A thorough knowledge of
the factors that affect VMC, as well as its definition,
is essential for multiengine pilots, and as such an
essential part of that required task. VMC is a speed
established by the manufacturer, published in the
AFM/POH, and marked on most airspeed indicators
with a red radial line. The multiengine pilot must
understand that VMC is not a fixed airspeed under all
conditions. VMC is a fixed airspeed only for the very
specific set of circumstances under which it was
determined during aircraft certification.
In reality, VMC varies with a variety of factors as
outlined below. The VMC noted in practice and
demonstration, or in actual single-engine operation,
could be less or even greater than the published
value, depending upon conditions and technique.
In aircraft certification, VMC is the sea level calibrated
airspeed at which, when the critical engine is suddenly
made inoperative, it is possible to maintain control of
the airplane with that engine still inoperative and then
maintain straight flight at the same speed with an angle
of bank of not more than 5°.
The foregoing refers to the determination of VMC under
“dynamic” conditions. This technique is only used by
highly experienced flight test pilots during aircraft certification.
It is never to be attempted outside of these
circumstances.
In aircraft certification, there is also a determination of
VMC under “static,” or steady-state conditions. If there
is a difference between the dynamic and static speeds,
the higher of the two is published as VMC. The static
determination is simply the ability to maintain straight
flight at VMC with a bank angle of not more than 5°. This
more closely resembles the VMC demonstration required
in the practical test for a multiengine class rating.
The AFM/POH-published VMC is determined with the
“critical” engine inoperative. The critical engine is the
Ch 12.qxd 5/7/04 9:55 AM Page 12-27
12-28
engine whose failure has the most adverse effect on
directional control. On twins with each engine rotating
in conventional, clockwise rotation as viewed from the
pilot’s seat, the critical engine will be the left engine.
Multiengine airplanes are subject to P-factor just as
single-engine airplanes are. The descending propeller
blade of each engine will produce greater thrust than
the ascending blade when the airplane is operated
under power and at positive angles of attack. The
descending propeller blade of the right engine is also
a greater distance from the center of gravity, and
therefore has a longer moment arm than the descending
propeller blade of the left engine. As a result,
failure of the left engine will result in the most
asymmetrical thrust (adverse yaw) as the right
engine will be providing the remaining thrust.
Many twins are designed with a counter-rotating right
engine. With this design, the degree of asymmetrical
thrust is the same with either engine inoperative. No
engine is more critical than the other, and a VMC
demonstration may be performed with either engine
windmilling.
In aircraft certification, dynamic VMC is determined
under the following conditions.
• Maximum available takeoff power. VMC
increases as power is increased on the operating
engine. With normally aspirated engines, VMC is
highest at takeoff power and sea level, and
decreases with altitude. With turbocharged
engines, takeoff power, and therefore VMC,
remains constant with increases in altitude up to
the engine’s critical altitude (the altitude where
the engine can no longer maintain 100 percent
power). Above the critical altitude, VMC
decreases just as it would with a normally aspirated
engine, whose critical altitude is sea level.
VMC tests are conducted at a variety of altitudes.
The results of those tests are then extrapolated to
a single, sea level value.
• Windmilling propeller. VMC increases with
increased drag on the inoperative engine. VMC is
highest, therefore, when the critical engine propeller
is windmilling at the low pitch, high
r.p.m. blade angle. VMC is determined with the
critical engine propeller windmilling in the
takeoff position, unless the engine is equipped
with an autofeather system.
• Most unfavorable weight and center-of-gravity
position. VMC increases as the center of gravity
is moved aft. The moment arm of the rudder is
reduced, and therefore its effectivity is reduced,
as the center of gravity is moved aft. At the same
time, the moment arm of the propeller blade is
increased, aggravating asymmetrical thrust.
Invariably, the aft-most CG limit is the most
unfavorable CG position. Currently, 14 CFR
part 23 calls for VMC to be determined at the
most unfavorable weight. For twins certificated
under CAR 3 or early 14 CFR part 23,
the weight at which VMC was determined was
not specified. VMC increases as weight is
reduced.
• Landing gear retracted. VMC increases when
the landing gear is retracted. Extended landing
gear aids directional stability, which tends to
decrease VMC.
Figure 12-19. Forces created during single-engine operation.
C L C L
D1 D2
Arm Arm
Inoperative
Engine
Inoperative
Engine
Operative
Engine
Operative
Engine
(Critical Engine)
Ch 12.qxd 5/7/04 9:55 AM Page 12-28
12-29
• Wing flaps in the takeoff position. For most
twins, this will be 0° of flaps.
• Cowl flaps in the takeoff position.
• Airplane trimmed for takeoff.
• Airplane airborne and the ground effect negligible.
• Maximum of 5° angle of bank. VMC is highly
sensitive to bank angle. To prevent claims of
an unrealistically low VMC speed in aircraft
certification, the manufacturer is permitted to
use a maximum of a 5° bank angle toward the
operative engine. The horizontal component of
lift generated by the bank assists the rudder in
counteracting the asymmetrical thrust of the
operative engine. The bank angle works in the
manufacturer’s favor in lowering VMC.
VMC is reduced significantly with increases in bank
angle. Conversely, VMC increases significantly with
decreases in bank angle. Tests have shown that VMC
may increase more than 3 knots for each degree of
bank angle less than 5°. Loss of directional control
may be experienced at speeds almost 20 knots above
published VMC when the wings are held level.
The 5° bank angle maximum is a regulatory limit
imposed upon manufacturers in aircraft certification.
The 5° bank does not inherently establish zero sideslip
or best single-engine climb performance. Zero sideslip,
and therefore best single-engine climb performance,
occurs at bank angles significantly less than 5°. The
determination of VMC in certification is solely concerned
with the minimum speed for directional control
under a very specific set of circumstances, and has
nothing to do with climb performance, nor is it the
optimum airplane attitude or configuration for climb
performance.
During dynamic VMC determination in aircraft certification,
cuts of the critical engine using the mixture
control are performed by flight test pilots while
gradually reducing the speed with each attempt. VMC
is the minimum speed at which directional control
could be maintained within 20° of the original entry
heading when a cut of the critical engine was made.
During such tests, the climb angle with both engines
operating was high, and the pitch attitude following
the engine cut had to be quickly lowered to regain
the initial speed. Pilots should never attempt to
demonstrate VMC with an engine cut from high
power, and never intentionally fail an engine at
speeds less than VSSE.
The actual demonstration of VMC and recovery in flight
training more closely resembles static VMC determination
in aircraft certification. For a demonstration,
the pilot should select an altitude that will allow
completion of the maneuver at least 3,000 feet AGL.
The following description assumes a twin with
noncounter-rotating engines, where the left engine
is critical.
With the landing gear retracted and the flaps set to the
takeoff position, the airplane should be slowed to
approximately 10 knots above VSSE or VYSE
(whichever is higher) and trimmed for takeoff. For the
remainder of the maneuver, the trim setting should not
be altered. An entry heading should be selected and
high r.p.m. set on both propeller controls. Power on the
left engine should be throttled back to idle as the right
engine power is advanced to the takeoff setting. The
landing gear warning horn will sound as long as a
Figure 12-20. Effect of CG location on yaw.
A
B
Inoperative
Engine
Operative
Engine
B x R = A x T
Inoperative
Engine
Operative
Engine
A
R
B
R
T T
Ch 12.qxd 5/7/04 9:55 AM Page 12-29
12-30
throttle is retarded. The pilots should continue to carefully
listen, however, for the stall warning horn, if so
equipped, or watch for the stall warning light. The left
yawing and rolling moment of the asymmetrical thrust
is counteracted primarily with right rudder. A bank
angle of 5° (a right bank, in this case) should also be
established.
While maintaining entry heading, the pitch attitude is
slowly increased to decelerate at a rate of 1 knot per
second (no faster). As the airplane slows and control
effectivity decays, the increasing yawing tendency
should be counteracted with additional rudder pressure.
Aileron displacement will also increase in order
to maintain 5° of bank. An airspeed is soon reached
where full right rudder travel and a 5° right bank can
no longer counteract the asymmetrical thrust, and the
airplane will begin to yaw uncontrollably to the left.
The moment the pilot first recognizes the uncontrollable
yaw, or experiences any symptom associated
with a stall, the operating engine throttle should be
sufficiently retarded to stop the yaw as the pitch
attitude is decreased. Recovery is made with a minimum
loss of altitude to straight flight on the entry heading at
VSSE or VYSE, before setting symmetrical power. The
recovery should not be attempted by increasing power
on the windmilling engine alone.
To keep the foregoing description simple, there were
several important background details that were not
covered. The rudder pressure during the demonstration
can be quite high. In certification, 150 pounds of force
is permitted before the limiting factor becomes rudder
pressure, not rudder travel. Most twins will run out of
rudder travel long before 150 pounds of pressure is
required. Still, it will seem considerable.
Maintaining altitude is not a criterion in accomplishing
this maneuver. This is a demonstration of
controllability, not performance. Many airplanes will
lose (or gain) altitude during the demonstration. Begin
the maneuver at an altitude sufficient to allow completion
by 3,000 feet AGL.
As discussed earlier, with normally aspirated engines,
VMC decreases with altitude. Stalling speed (VS),
however, remains the same. Except for a few models,
published VMC is almost always higher than VS. At
sea level, there is usually a margin of several knots
between VMC and VS, but the margin decreases with
altitude, and at some altitude, VMC and VS are the
same.
Should a stall occur while the airplane is under asymmetrical
power, particularly high asymmetrical power,
a spin entry is likely. The yawing moment induced
from asymmetrical thrust is little different from that
induced by full rudder in an intentional spin in the
appropriate model of single-engine airplane. In this
case, however, the airplane will depart controlled
flight in the direction of the idle engine, not in the
direction of the applied rudder. Twins are not required
to demonstrate recoveries from spins, and their spin
recovery characteristics are generally very poor.
Where VS is encountered at or before VMC, the departure
from controlled flight may be quite sudden, with
strong yawing and rolling tendencies to the inverted
position, and a spin entry. Therefore, during a VMC
demonstration, if there are any symptoms of an
impending stall such as a stall warning light or horn,
airframe or elevator buffet, or rapid decay in control
effectiveness, the maneuver should be terminated
immediately, the angle of attack reduced as the throttle
is retarded, and the airplane returned to the entry
airspeed. It should be noted that if the pilots are
wearing headsets, the sound of a stall warning horn
will tend to be masked.
The VMC demonstration only shows the earliest onset
of a loss of directional control. It is not a loss of control
of the airplane when performed in accordance with
the foregoing procedures. A stalled condition should
never be allowed to develop. Stalls should never be
performed with asymmetrical thrust and the VMC
demonstration should never be allowed to degrade into
a single-engine stall. A VMC demonstration that is
allowed to degrade into a single-engine stall with high
asymmetrical thrust is very likely to result in a loss of
control of the airplane.
An actual demonstration of VMC may not be possible
under certain conditions of density altitude, or with
airplanes whose VMC is equal to or less than VS. Under
those circumstances, as a training technique, a demonstration
of VMC may be safely conducted by artificially
limiting rudder travel to simulate maximum available
rudder. Limiting rudder travel should be accomplished
at a speed well above VS (approximately 20 knots).
Density Altitude
Indicated Airspeed
Stall
Occurs
First
Yaw
Occurs
First
Recovery
May Be
Difficult
Altitude Where
VMC = Stall Speed
Engine-Out
Power-On
Stall Speed (VS)
VMC
Figure 12-21. Graph depicting relationship of VMC to VS.
Ch 12.qxd 5/7/04 9:55 AM Page 12-30
The rudder limiting technique avoids the hazards of
spinning as a result of stalling with high asymmetrical
power, yet is effective in demonstrating the loss of
directional control.
The VMC demonstration should never be performed
from a high pitch attitude with both engines operating
and then reducing power on one engine. The preceding
discussion should also give ample warning as to why
engine failures are never to be performed at low airspeeds.
An unfortunate number of airplanes and pilots
have been lost from unwarranted simulated engine
failures at low airspeeds that degenerated into loss of
control of the airplane. VSSE is the minimum airspeed
at which any engine failure should be simulated.
MULTIENGINE TRAINING
CONSIDERATIONS
Flight training in a multiengine airplane can be safely
accomplished if both the instructor and the student are
cognizant of the following factors.
• No flight should ever begin without a thorough
preflight briefing of the objectives, maneuvers,
expected student actions, and completion standards.
• Aclear understanding must be reached as to how
simulated emergencies will be introduced, and
what action the student is expected to take.
The introduction, practice, and testing of emergency
procedures has always been a sensitive subject.
Surprising a multiengine student with an emergency
without a thorough briefing beforehand has no place
in flight training. Effective training must be carefully
balanced with safety considerations. Simulated engine
failures, for example, can very quickly become actual
emergencies or lead to loss of the airplane when
approached carelessly. Pulling circuit breakers can
lead to a subsequent gear up landing. Stall-spin accidents
in training for emergencies rival the number of
stall-spin accidents from actual emergencies.
All normal, abnormal, and emergency procedures can
and should be introduced and practiced in the airplane
as it sits on the ground, power off. In this respect, the
airplane is used as a cockpit procedures trainer (CPT),
ground trainer, or simulator. The value of this training
should never be underestimated. The engines do not
have to be operating for real learning to occur. Upon
completion of a training session, care should be taken
to return items such as switches, valves, trim, fuel selectors,
and circuit breakers to their normal positions.
Pilots who do not use a checklist effectively will be at
a significant disadvantage in multiengine airplanes.
Use of the checklist is essential to safe operation of
airplanes and no flight should be conducted without
one. The manufacturer’s checklist or an aftermarket
checklist for the specific make, model, and model year
should be used. If there is a procedural discrepancy
between the checklist and AFM/POH, then the
AFM/POH always takes precedence.
Certain immediate action items (such as the response
to an engine failure in a critical phase of flight) should
be committed to memory. After they are accomplished,
and as work load permits, the pilot should verify the
action taken with a printed checklist.
Simulated engine failures during the takeoff ground
roll should be accomplished with the mixture control.
The simulated failure should be introduced at a speed
no greater than 50 percent of VMC. If the student does
not react promptly by retarding both throttles, the
instructor can always pull the other mixture.
The FAA recommends that all in-flight simulated
engine failures below 3,000 feet AGL be introduced
with a smooth reduction of the throttle. Thus, the
engine is kept running and is available for instant use,
if necessary. Throttle reduction should be smooth
rather than abrupt to avoid abusing the engine and possibly
causing damage. All inflight engine failures must
be conducted at VSSE or above.
If the engines are equipped with dynamic crankshaft
counterweights, it is essential to make throttle reductions
for simulated failures smoothly. Other areas leading to
dynamic counterweight damage include high r.p.m. and
low manifold pressure combinations, overboosting, and
propeller feathering. Severe damage or repetitive abuse
to counterweights will eventually lead to engine failure.
Dynamic counterweights are found on larger, more
complex engines—instructors should check with
maintenance personnel or the engine manufacturer to
determine if their engines are so equipped.
When an instructor simulates an engine failure, the
student should respond with the appropriate memory
items and retard the propeller control towards the
FEATHER position. Assuming zero thrust will be set,
the instructor should promptly move the propeller
control forward and set the appropriate manifold
pressure and r.p.m. It is vital that the student be kept
informed of the instructor’s intentions. At this point
the instructor may state words to the effect, “I have the
right engine; you have the left. I have set zero thrust
and the right engine is simulated feathered.” There
should never be any ambiguity as to who is operating
what systems or controls.
Following a simulated engine failure, the instructor
should continue to care for the “failed” engine just as
the student cares for the operative engine. If zero thrust
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12-32
is set to simulate a feathered propeller, the cowl flap
should be closed and the mixture leaned. An occasional
clearing of the engine is also desirable. If possible,
avoid high power applications immediately following
a prolonged cool-down at a zero-thrust power setting.
The flight instructor must impress on the student multiengine
pilot the critical importance of feathering the
propeller in a timely manner should an actual engine
failure situation be encountered. Awindmilling propeller,
in many cases, has given the improperly trained
multiengine pilot the mistaken perception that the
failed engine is still developing useful thrust, resulting
in a psychological reluctance to feather, as feathering
results in the cessation of propeller rotation. The flight
instructor should spend ample time demonstrating
the difference in the performance capabilities of the
airplane with a simulated feathered propeller (zero
thrust) as opposed to a windmilling propeller.
All actual propeller feathering should be performed at
altitudes and positions where safe landings on established
airports could be readily accomplished.
Feathering and restart should be planned so as to be
completed no lower than 3,000 feet AGL. At certain
elevations and with many popular multiengine training
airplanes, this may be above the single-engine service
ceiling, and level flight will not be possible.
Repeated feathering and unfeathering is hard on the
engine and airframe, and should be done only as
absolutely necessary to ensure adequate training. The
FAA’s practical test standards for a multiengine class
rating requires the feathering and unfeathering of one
propeller during flight in airplanes in which it is safe to
do so.
While much of this chapter has been devoted to the
unique flight characteristics of the multiengine airplane
with one engine inoperative, the modern,
well-maintained reciprocating engine is remarkably
reliable. Simulated engine failures at extremely low
altitudes (such as immediately after lift-off) and/or
below VSSE are undesirable in view of the non-existent
safety margins involved. The high risk of simulating
an engine failure below 200 feet AGL does not warrant
practicing such maneuvers.
For training in maneuvers that would be hazardous in
flight, or for initial and recurrent qualification in an
advanced multiengine airplane, a simulator training
center or manufacturer’s training course should be
given consideration. Comprehensive training manuals
and classroom instruction are available along with system
training aids, audio/visuals, and flight training
devices and simulators. Training under a wide variety
of environmental and aircraft conditions is available
through simulation. Emergency procedures that would
be either dangerous or impossible to accomplish in an
airplane can be done safely and effectively in a flight
training device or simulator. The flight training device
or simulator need not necessarily duplicate the specific
make and model of airplane to be useful. Highly
effective instruction can be obtained in training
devices for other makes and models as well as generic
training devices.
The majority of multiengine training is conducted in
four to six-place airplanes at weights significantly less
than maximum. Single-engine performance, particularly
at low density altitudes, may be deceptively good.
To experience the performance expected at higher
weights, altitudes, and temperatures, the instructor
should occasionally artificially limit the amount of
manifold pressure available on the operative engine.
Airport operations above the single-engine ceiling can
also be simulated in this manner. Loading the airplane
with passengers to practice emergencies at maximum
takeoff weight is not appropriate.
The use of the touch-and-go landing and takeoff in
flight training has always been somewhat controversial.
The value of the learning experience must be weighed
against the hazards of reconfiguring the airplane for
takeoff in an extremely limited time as well as the loss
of the follow-through ordinarily experienced in a full
stop landing. Touch and goes are not recommended
during initial aircraft familiarization in multiengine
airplanes.
If touch and goes are to be performed at all, the student
and instructor responsibilities need to be carefully
briefed prior to each flight. Following touchdown, the
student will ordinarily maintain directional control
while keeping the left hand on the yoke and the right
hand on the throttles. The instructor resets the flaps
and trim and announces when the airplane has been
reconfigured. The multiengine airplane needs considerably
more runway to perform a touch and go than a
single-engine airplane. A full stop-taxi back landing is
preferable during initial familiarization. Solo touch
and goes in twins are strongly discouraged.
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13-1
TAILWHEEL AIRPLANES
Tailwheel airplanes are often referred to as
conventional gear airplanes. Due to their design and
structure, tailwheel airplanes exhibit operational and
handling characteristics that are different from those of
tricycle gear airplanes. Tailwheel airplanes are not
necessarily more difficult to takeoff, land, and/or taxi
than tricycle gear airplanes; in fact under certain
conditions, they may even handle with less difficulty.
This chapter will focus on the operational differences
that occur during ground operations, takeoffs, and
landings.
LANDING GEAR
The main landing gear forms the principal support of
the airplane on the ground. The tailwheel also supports
the airplane, but steering and directional control are its
primary functions. With the tailwheel-type airplane, the
two main struts are attached to the airplane slightly
ahead of the airplane’s center of gravity (CG).
The rudder pedals are the primary directional controls
while taxiing. Steering with the pedals may be
accomplished through the forces of airflow or propeller
slipstream acting on the rudder surface, or through a
mechanical linkage to the steerable tailwheel. Initially,
the pilot should taxi with the heels of the feet resting on
the cockpit floor and the balls of the feet on the bottom
of the rudder pedals. The feet should be slid up onto the
brake pedals only when it is necessary to depress the
brakes. This permits the simultaneous application of
rudder and brake whenever needed. Some models of
tailwheel airplanes are equipped with heel brakes rather
than toe brakes. In either configuration the brakes are
used primarily to stop the airplane at a desired point, to
slow the airplane, or as an aid in making a sharp
controlled turn. Whenever used, they must be applied
smoothly, evenly, and cautiously at all times.
TAXIING
When beginning to taxi, the brakes should be tested
immediately for proper operation. This is done by first
applying power to start the airplane moving slowly
forward, then retarding the throttle and simultaneously
applying pressure smoothly to both brakes. If braking
action is unsatisfactory, the engine should be shut down
immediately.
To turn the airplane on the ground, the pilot should
apply rudder in the desired direction of turn and use
whatever power or brake that is necessary to control
the taxi speed. The rudder should be held in the
direction of the turn until just short of the point where
the turn is to be stopped, then the rudder pressure
released or slight opposite pressure applied as needed.
While taxiing, the pilot will have to anticipate the
movements of the airplane and adjust rudder pressure
accordingly. Since the airplane will continue to turn
slightly even as the rudder pressure is being released,
the stopping of the turn must be anticipated and the
rudder pedals neutralized before the desired heading is
reached. In some cases, it may be necessary to apply
opposite rudder to stop the turn, depending on the taxi
speed.
The presence of moderate to strong headwinds and/or a
strong propeller slipstream makes the use of the
elevator necessary to maintain control of the pitch
attitude while taxiing. This becomes apparent when
considering the lifting action that may be created on
the horizontal tail surfaces by either of those two
factors. The elevator control should be held in the aft
position (stick or yoke back) to hold the tail down.
When taxiing in a quartering headwind, the wing on
the upwind side will usually tend to be lifted by the
wind unless the aileron control is held in that direction
(upwind aileron UP). Moving the aileron into the UP
position reduces the effect of wind striking that wing,
thus reducing the lifting action. This control movement
will also cause the opposite aileron to be placed in the
DOWN position, thus creating drag and possibly some
lift on the downwind wing, further reducing the
tendency of the upwind wing to rise.
When taxiing with a quartering tailwind, the elevator
should be held in the full DOWN position (stick or
yoke full forward), and the upwind aileron down. Since
the wind is striking the airplane from behind, these
control positions reduce the tendency of the wind to get
under the tail and the wing possibly causing the
airplane to nose over. The application of these
crosswind taxi corrections also helps to minimize the
weathervaning tendency and ultimately results in
increased controllability.
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13-2
An airplane with a tailwheel has a tendency to
weathervane or turn into the wind while it is being
taxied. The tendency of the airplane to weathervane is
greatest while taxiing directly crosswind;
consequently, directional control is somewhat difficult.
Without brakes, it is almost impossible to keep the
airplane from turning into any wind of considerable
velocity since the airplane’s rudder control capability
may be inadequate to counteract the crosswind. In
taxiing downwind, the tendency to weathervane is
increased, due to the tailwind decreasing the
effectiveness of the flight controls. This requires a
more positive use of the rudder and the brakes,
particularly if the wind velocity is above that of a light
breeze.
Unless the field is soft, or very rough, it is best when
taxiing downwind to hold the elevator control in the
forward position. Even on soft fields, the elevator
should be raised only as much as is absolutely
necessary to maintain a safe margin of control in case
there is a tendency of the airplane to nose over.
On most tailwheel-type airplanes, directional control
while taxiing is facilitated by the use of a steerable
tailwheel, which operates along with the rudder. The
tailwheel steering mechanism remains engaged when
the tailwheel is operated through an arc of about 16 to
18° each side of neutral and then automatically
becomes full swiveling when turned to a greater angle.
On some models the tailwheel may also be locked in
place. The airplane may be pivoted within its own
length, if desired, yet is fully steerable for slight turns
while taxiing forward. While taxiing, the steerable
tailwheel should be used for making normal turns and
the pilot’s feet kept off the brake pedals to avoid
unnecessary wear on the brakes.
Since a tailwheel-type airplane rests on the tailwheel
as well as the main landing wheels, it assumes a
nose-high attitude when on the ground. In most cases
this places the engine cowling high enough to restrict
the pilot’s vision of the area directly ahead of the
airplane. Consequently, objects directly ahead of the
airplane are difficult, if not impossible, to see. To
observe and avoid colliding with any objects or
hazardous surface conditions, the pilot should
alternately turn the nose from one side to the
other—that is zigzag, or make a series of short S-turns
while taxiing forward. This should be done slowly,
smoothly, positively, and cautiously.
NORMAL TAKEOFF ROLL
After taxiing onto the runway, the airplane should be
carefully aligned with the intended takeoff direction,
and the tailwheel positioned straight, or centered. In
airplanes equipped with a locking device, the tailwheel
should be locked in the centered position. After
releasing the brakes, the throttle should be smoothly
and continuously advanced to takeoff power. As the
airplane starts to roll forward, the pilot should slide
both feet down on the rudder pedals so that the toes or
balls of the feet are on the rudder portions, not on the
brake portions.
An abrupt application of power may cause the airplane
to yaw sharply to the left because of the torque effects
of the engine and propeller. Also, precession will be
particularly noticeable during takeoff in a tailwheeltype
airplane if the tail is rapidly raised from a three
point to a level flight attitude. The abrupt change of
attitude tilts the horizontal axis of the propeller, and
the resulting precession produces a forward force on
the right side (90° ahead in the direction of rotation),
yawing the airplane’s nose to the left. The amount of
force created by this precession is directly related to
the rate the propeller axis is tilted when the tail is
raised. With this in mind, the throttle should always be
advanced smoothly and continuously to prevent any
sudden swerving.
Smooth, gradual advancement of the throttle is very
important in tailwheel-type airplanes, since
peculiarities in their takeoff characteristics are
accentuated in proportion to how rapidly the takeoff
power is applied.
As speed is gained, the elevator control will tend to
assume a neutral position if the airplane is correctly
trimmed. At the same time, directional control should
be maintained with smooth, prompt, positive rudder
corrections throughout the takeoff roll. The effects of
torque and P-factor at the initial speeds tend to pull the
nose to the left. The pilot must use what rudder
pressure is needed to correct for these effects or for
existing wind conditions to keep the nose of the
airplane headed straight down the runway. The use of
brakes for steering purposes should be avoided, since
they will cause slower acceleration of the airplane’s
speed, lengthen the takeoff distance, and possibly
result in severe swerving.
When the elevator trim is set for takeoff, on
application of maximum allowable power, the airplane
will (when sufficient speed has been attained)
normally assume the correct takeoff pitch attitude on
its own—the tail will rise slightly. This attitude can
then be maintained by applying slight back-elevator
pressure. If the elevator control is pushed forward
during the takeoff roll to prematurely raise the tail, its
effectiveness will rapidly build up as the speed
increases, making it necessary to apply back-elevator
pressure to lower the tail to the proper takeoff attitude.
This erratic change in attitude will delay the takeoff
and lead to directional control problems. Rudder
pressure must be used promptly and smoothly to
Ch 13.qxd 5/7/04 10:04 AM Page 13-2
13-3
counteract yawing forces so that the airplane continues
straight down the runway.
While the speed of the takeoff roll increases, more and
more pressure will be felt on the flight controls,
particularly the elevators and rudder. Since the tail
surfaces receive the full effect of the propeller
slipstream, they become effective first. As the speed
continues to increase, all of the flight controls will
gradually become effective enough to maneuver the
airplane about its three axes. It is at this point, in the
taxi to flight transition, that the airplane is being flown
more than taxied. As this occurs, progressively smaller
rudder deflections are needed to maintain direction.
TAKEOFF
Since a good takeoff depends on the proper takeoff
attitude, it is important to know how this attitude
appears and how it is attained. The ideal takeoff
attitude requires only minimum pitch adjustments
shortly after the airplane lifts off to attain the speed for
the best rate of climb.
The tail should first be allowed to rise off the ground
slightly to permit the airplane to accelerate more
rapidly. At this point, the position of the nose in
relation to the horizon should be noted, then elevator
pressure applied as necessary to hold this attitude. The
wings are kept level by applying aileron pressure as
necessary.
The airplane may be allowed to fly off the ground
while in normal takeoff attitude. Forcing it into the air
by applying excessive back-elevator pressure would
result in an excessively high pitch attitude and may
delay the takeoff. As discussed earlier, excessive and
rapid changes in pitch attitude result in proportionate
changes in the effects of torque, making the airplane
more difficult to control.
Although the airplane can be forced into the air, this is
considered an unsafe practice and should be avoided
under normal circumstances. If the airplane is forced
to leave the ground by using too much back-elevator
pressure before adequate flying speed is attained, the
wing’s angle of attack may be excessive, causing the
airplane to settle back to the runway or even to stall.
On the other hand, if sufficient back-elevator pressure
is not held to maintain the correct takeoff attitude after
becoming airborne, or the nose is allowed to lower
excessively, the airplane may also settle back to the
runway. This occurs because the angle of attack is
decreased and lift is diminished to the degree where it
will not support the airplane. It is important to hold the
attitude constant after rotation or lift-off.
As the airplane leaves the ground, the pilot must
continue to maintain straight flight, as well as holding
the proper pitch attitude. During takeoffs in strong,
gusty wind, it is advisable that an extra margin of speed
be obtained before the airplane is allowed to leave the
ground. A takeoff at the normal takeoff speed may
result in a lack of positive control, or a stall, when the
airplane encounters a sudden lull in strong, gusty wind,
or other turbulent air currents. In this case, the pilot
should hold the airplane on the ground longer to attain
more speed, then make a smooth, positive rotation to
leave the ground.
CROSSWIND TAKEOFF
It is important to establish and maintain the proper
amount of crosswind correction prior to lift-off; that is,
apply aileron pressure toward the wind to keep the
upwind wing from rising and apply rudder pressure as
needed to prevent weathervaning.
As the tailwheel is raised off the runway, the holding
of aileron control into the wind may result in the
downwind wing rising and the downwind main wheel
lifting off the runway first, with the remainder of the
takeoff roll being made on one main wheel. This is
acceptable and is preferable to side-skipping.
If a significant crosswind exists, the main wheels
should be held on the ground slightly longer than in a
normal takeoff so that a smooth but definite lift-off can
be made. This procedure will allow the airplane to
leave the ground under more positive control so that it
will definitely remain airborne while the proper
amount of drift correction is being established. More
importantly, it will avoid imposing excessive side
loads on the landing gear and prevent possible damage
that would result from the airplane settling back to the
runway while drifting.
As both main wheels leave the runway, and ground
friction no longer resists drifting, the airplane will be
slowly carried sideways with the wind until adequate
drift correction is maintained.
SHORT-FIELD TAKEOFF
Wing flaps should be lowered prior to takeoff if
recommended by the manufacturer. Takeoff power
should be applied smoothly and continuously, (there
should be no hesitation) to accelerate the airplane as
rapidly as possible. As the takeoff roll progresses, the
airplane’s pitch attitude and angle of attack should be
adjusted to that which results in the minimum amount
of drag and the quickest acceleration. The tail should
be allowed to rise off the ground slightly, then held in
this tail-low flight attitude until the proper lift-off or
rotation airspeed is attained. For the steepest climb-out
and best obstacle clearance, the airplane should be
allowed to roll with its full weight on the main wheels
and accelerated to the lift-off speed.
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13-4
SOFT-FIELD TAKEOFF
Wing flaps may be lowered prior to starting the takeoff
(if recommended by the manufacturer) to provide
additional lift and transfer the airplane’s weight from
the wheels to the wings as early as possible. The
airplane should be taxied onto the takeoff surface
without stopping on a soft surface. Stopping on a soft
surface, such as mud or snow, might bog the
airplane down. The airplane should be kept in
continuous motion with sufficient power while lining
up for the takeoff roll.
As the airplane is aligned with the proposed takeoff
path, takeoff power is applied smoothly and as rapidly
as the powerplant will accept it without faltering. The
tail should be kept low to maintain the inherent
positive angle of attack and to avoid any tendency of
the airplane to nose over as a result of soft spots, tall
grass, or deep snow.
When the airplane is held at a nose-high attitude
throughout the takeoff run, the wings will, as speed
increases and lift develops, progressively relieve the
wheels of more and more of the airplane’s weight,
thereby minimizing the drag caused by surface
irregularities or adhesion. If this attitude is accurately
maintained, the airplane will virtually fly itself off the
ground. The airplane should be allowed to accelerate
to climb speed in ground effect.
TOUCHDOWN
The touchdown is the gentle settling of the airplane
onto the landing surface. The roundout and touchdown
should be made with the engine idling, and the airplane
at minimum controllable airspeed, so that the airplane
will touch down at approximately stalling speed. As
the airplane settles, the proper landing attitude must be
attained by applying whatever back-elevator pressure
is necessary. The roundout and touchdown should be
timed so that the wheels of the main landing gear and
tailwheel touch down simultaneously (three-point
landing). This requires proper timing, technique, and
judgment of distance and altitude.
When the wheels make contact with the ground, the
elevator control should be carefully eased fully back
to hold the tail down and to keep the tailwheel on the
ground. This provides more positive directional
control of the airplane equipped with a steerable
tailwheel, and prevents any tendency for the airplane
to nose over. If the tailwheel is not on the ground,
easing back on the elevator control may cause the
airplane to become airborne again because the change
in attitude will increase the angle of attack and
produce enough lift for the airplane to fly.
It is extremely important that the touchdown occur
with the airplane’s longitudinal axis exactly parallel to
the direction the airplane is moving along the runway.
Failure to accomplish this not only imposes severe
side loads on the landing gear, but imparts
groundlooping (swerving) tendencies. To avoid these
side stresses or a ground loop, the pilot must never
allow the airplane to touch down while in a crab or
while drifting.
AFTER-LANDING ROLL
The landing process must never be considered
complete until the airplane decelerates to the normal
taxi speed during the landing roll or has been brought
to a complete stop when clear of the landing area. The
pilot must be alert for directional control difficulties
immediately upon and after touchdown due to the
ground friction on the wheels. The friction creates a
pivot point on which a moment arm can act. This is
because the CG is behind the main wheels.
Any difference between the direction the airplane is
traveling and the direction it is headed will produce a
moment about the pivot point of the wheels, and the
airplane will tend to swerve. Loss of directional
control may lead to an aggravated, uncontrolled, tight
turn on the ground, or a ground loop. The combination
of inertia acting on the CG and ground friction of the
main wheels resisting it during the ground loop may
cause the airplane to tip or lean enough for the outside
Main Gear and Tailwheel
Touch Down Simultaneously
Hold Elevator
Full Up
Normal
Glide
Start Roundout
to Landing Attitude
Figure 13-1.Tailwheel touchdown.
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13-5
wingtip to contact the ground, and may even impose a
sideward force that could collapse the landing gear.
The airplane can ground loop late in the after-landing
roll because rudder effectiveness decreases with the
decreasing flow of air along the rudder surface as the
airplane slows. As the airplane speed decreases and the
tailwheel has been lowered to the ground, the steerable
tailwheel provides more positive directional control.
To use the brakes, the pilot should slide the toes or feet
up from the rudder pedals to the brake pedals (or apply
heel pressure in airplanes equipped with heel brakes).
If rudder pressure is being held at the time braking
action is needed, that pressure should not be released
as the feet or toes are being slid up to the brake pedals,
because control may be lost before brakes can be
applied. During the ground roll, the airplane’s
direction of movement may be changed by carefully
applying pressure on one brake or uneven pressures on
each brake in the desired direction. Caution must be
exercised, when applying brakes to avoid
overcontrolling.
If a wing starts to rise, aileron control should be
applied toward that wing to lower it. The amount
required will depend on speed because as the forward
speed of the airplane decreases, the ailerons will
become less effective.
The elevator control should be held back as far as
possible and as firmly as possible, until the airplane
stops. This provides more positive control with
tailwheel steering, tends to shorten the after-landing
roll, and prevents bouncing and skipping.
If available runway permits, the speed of the airplane
should be allowed to dissipate in a normal manner by
the friction and drag of the wheels on the ground.
Brakes may be used if needed to help slow the airplane.
After the airplane has been slowed sufficiently and has
been turned onto a taxiway or clear of the landing area,
it should be brought to a complete stop. Only after this
is done should the pilot retract the flaps and perform
other checklist items.
CROSSWIND LANDING
If the crab method of drift correction has been used
throughout the final approach and roundout, the crab
must be removed before touchdown by applying
rudder to align the airplane’s longitudinal axis with its
direction of movement. This requires timely and
accurate action. Failure to accomplish this results in
severe side loads being imposed on the landing gear
and imparts ground looping tendencies.
If the wing-low method is used, the crosswind
correction (aileron into the wind and opposite rudder)
should be maintained throughout the roundout, and the
touchdown made on the upwind main wheel.
During gusty or high-wind conditions, prompt
adjustments must be made in the crosswind correction
to assure that the airplane does not drift as it touches
down.
As the forward speed decreases after initial contact,
the weight of the airplane will cause the downwind
main wheel to gradually settle onto the runway.
An adequate amount of power should be used to
maintain the proper airspeed throughout the approach,
and the throttle should be retarded to idling position
after the main wheels contact the landing surface. Care
must be exercised in closing the throttle before the
pilot is ready for touchdown, because the sudden or
premature closing of the throttle may cause a sudden
increase in the descent rate that could result in a hard
landing.
CROSSWIND AFTER-LANDING ROLL
Particularly during the after-landing roll, special
attention must be given to maintaining directional
control by the use of rudder and tailwheel steering,
while keeping the upwind wing from rising by the use
of aileron. Characteristically, an airplane has a greater
profile, or side area, behind the main landing gear than
forward of it. With the main wheels
acting as a pivot point and the greater surface area
exposed to the crosswind behind that pivot point, the
airplane will tend to turn or weathervane into the wind.
This weathervaning tendency is more prevalent in the
tailwheel-type because the airplane’s surface area
behind the main landing gear is greater than in
nosewheel-type airplanes.
Point of
Wheel Pivoting
C.G.
Figure 13-2. Effect of CG on directional control.
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13-6
Pilots should be familiar with the crosswind component
of each airplane they fly, and avoid operations in
wind conditions that exceed the capability of the
airplane, as well as their own limitations.
While the airplane is decelerating during the
after-landing roll, more aileron must be applied to keep
the upwind wing from rising. Since the airplane is
slowing down, there is less airflow around the ailerons
and they become less effective. At the same time, the
relative wind is becoming more of a crosswind and
exerting a greater lifting force on the upwind wing.
Consequently, when the airplane is coming to a stop,
the aileron control must be held fully toward the wind.
WHEEL LANDING
Landings from power approaches in turbulence or in
crosswinds should be such that the touchdown is made
with the airplane in approximately level flight attitude.
The touchdown should be made smoothly on the main
wheels, with the tailwheel held clear of the runway.
This is called a “wheel landing” and requires careful
timing and control usage to prevent bouncing. These
wheel landings can be best accomplished by holding
the airplane in level flight attitude until the main
wheels touch, then immediately but smoothly
retarding the throttle, and holding sufficient forward
elevator pressure to hold the main wheels on the
ground. The airplane should never be forced onto the
ground by excessive forward pressure.
If the touchdown is made at too high a rate of descent
as the main wheels strike the landing surface, the tail is
forced down by its own weight. In turn, when the tail is
forced down, the wing’s angle of attack increases
resulting in a sudden increase in lift and the airplane
may become airborne again. Then as the airplane’s
speed continues to decrease, the tail may again lower
onto the runway. If the tail is allowed to settle too
quickly, the airplane may again become airborne. This
process, often called “porpoising,” usually intensifies
even though the pilot tries to stop it. The best
corrective action is to execute a go-around procedure.
SHORT-FIELD LANDING
Upon touchdown, the airplane should be firmly held in
a three-point attitude. This will provide aerodynamic
braking by the wings. Immediately upon touchdown,
and closing the throttle, the brakes should be applied
evenly and firmly to minimize the after-landing roll.
The airplane should be stopped within the shortest
possible distance consistent with safety.
SOFT-FIELD LANDING
The tailwheel should touch down simultaneously with
or just before the main wheels, and should then be held
down by maintaining firm back-elevator pressure
throughout the landing roll. This will minimize any
tendency for the airplane to nose over and will provide
aerodynamic braking. The use of brakes on a soft field
is not needed because the soft or rough surface itself
will provide sufficient reduction in the airplane’s
forward speed. Often it will be found that upon
landing on a very soft field, the pilot will need to
increase power to keep the airplane moving and from
becoming stuck in the soft surface.
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. It is not
always caused by drift or weathervaning, 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
cause the airplane to ground loop.
Due to the characteristics of an airplane equipped with
a tailwheel, the forces that cause a ground loop
increase as the swerve increases. The initial swerve
develops inertia and this, acting at the CG (which is
located behind the main wheels), swerves the airplane
even more. If allowed to develop, the force produced
may become great enough to tip the airplane until one
wing strikes the ground.
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.
Figure 13-3.Weathervaning tendency.
Profile
Behind Pivot Point
N S
W E
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14-1
GENERAL
The turbopropeller-powered airplane flies and handles
just like any other airplane of comparable size and
weight. The aerodynamics are the same. The major
differences between flying a turboprop and other
non-turbine-powered airplanes are found in the powerplant
and systems. The powerplant is different and
requires operating procedures that are unique to gas
turbine engines. But so, too, are other systems such as
the electrical system, hydraulics, environmental, flight
control, rain and ice protection, and avionics. The
turbopropeller-powered airplane also has the advantage
of being equipped with a constant speed, full feathering
and reversing propeller—something normally not
found on piston-powered airplanes.
THE GAS TURBINE ENGINE
Both piston (reciprocating) engines and gas turbine
engines are internal combustion engines. They have a
similar cycle of operation that consists of induction,
compression, combustion, expansion, and exhaust. In a
piston engine, each of these events is a separate distinct
occurrence in each cylinder. Also, in a piston engine an
ignition event must occur during each cycle, in each
cylinder. Unlike reciprocating engines, in gas turbine
engines these phases of power occur simultaneously
and continuously instead of one cycle at a time.
Additionally, ignition occurs during the starting cycle
and is continuous thereafter.
The basic gas turbine engine contains four sections:
intake, compression, combustion, and exhaust.
To start the engine, the compressor section is rotated by
an electrical starter on small engines or an air driven
starter on large engines. As compressor r.p.m.
accelerates, air is brought in through the inlet duct,
compressed to a high pressure, and delivered to the
combustion section (combustion chambers). Fuel is
then injected by a fuel controller through spray
nozzles and ignited by igniter plugs. (Not all of the
compressed air is used to support combustion. Some of
the compressed air bypasses the burner section and circulates
within the engine to provide internal cooling.) The
fuel/air mixture in the combustion chamber is then burned
in a continuous combustion process and produces a very
high temperature, typically around 4,000°F, which heats
INTAKE COMPRESSION COMBUSTION EXHAUST
Air Inlet Compression Combustion Chambers Turbine Exhaust
Cold Section Hot Section
Figure 14-1. Basic components of a gas turbine engine.
Ch 14.qxd 5/7/04 10:08 AM Page 14-1
14-2
the entire air mass to 1,600 – 2,400°F. The mixture of
hot air and gases expands and is directed to the turbine
blades forcing the turbine section to rotate, which in
turn drives the compressor by means of a direct shaft.
After powering the turbine section, the high velocity
excess exhaust exits the tail pipe or exhaust section.
Once the turbine section is powered by gases from the
burner section, the starter is disengaged, and the
igniters are turned off. Combustion continues until the
engine is shut down by turning off the fuel supply.
High-pressure exhaust gases can be used to provide
jet thrust as in a turbojet engine. Or, the gases
can be directed through an additional turbine to drive a
propeller through reduction gearing, as in a
turbopropeller (turboprop) engine.
TURBOPROP ENGINES
The turbojet engine excels the reciprocating engine in
top speed and altitude performance. On the other hand,
the turbojet engine has limited takeoff and initial climb
performance, as compared to that of a reciprocating
engine. In the matter of takeoff and initial climb
performance, the reciprocating engine is superior to
the turbojet engine. Turbojet engines are most efficient
at high speeds and high altitudes, while propellers are
most efficient at slow and medium speeds (less than
400 m.p.h.). Propellers also improve takeoff and climb
performance. The development of the turboprop
engine was an attempt to combine in one engine the
best characteristics of both the turbojet, and propeller
driven reciprocating engine.
The turboprop engine offers several advantages over
other types of engines such as:
• Light weight.
• Mechanical reliability due to relatively few
moving parts.
• Simplicity of operation.
• Minimum vibration.
• High power per unit of weight.
• Use of propeller for takeoff and landing.
Turboprop engines are most efficient at speeds
between 250 and 400 m.p.h. and altitudes between
18,000 and 30,000 feet. They also perform well at the
slow speeds required for takeoff and landing, and are
fuel efficient. The minimum specific fuel consumption
of the turboprop engine is normally available in the
altitude range of 25,000 feet up to the tropopause.
The power output of a piston engine is measured in
horsepower and is determined primarily by r.p.m. and
manifold pressure. The power of a turboprop engine,
however, is measured in shaft horsepower (shp). Shaft
horsepower is determined by the r.p.m. and the torque
(twisting moment) applied to the propeller shaft. Since
turboprop engines are gas turbine engines, some jet
thrust is produced by exhaust leaving the engine. This
thrust is added to the shaft horsepower to determine
the total engine power, or equivalent shaft horsepower
(eshp). Jet thrust usually accounts for less than
10 percent of the total engine power.
Although the turboprop engine is more complicated
and heavier than a turbojet engine of equivalent size
and power, it will deliver more thrust at low subsonic
airspeeds. However, the advantages decrease as flight
speed increases. In normal cruising speed ranges, the
propulsive efficiency (output divided by input) of a
turboprop decreases as speed increases.
The propeller of a typical turboprop engine is
responsible for roughly 90 percent of the total thrust
under sea level conditions on a standard day. The
excellent performance of a turboprop during takeoff
and climb is the result of the ability of the propeller to
accelerate a large mass of air while the airplane is
moving at a relatively low ground and flight speed.
“Turboprop,” however, should not be confused with
“turbosupercharged” or similar terminology. All
turbine engines have a similarity to normally aspirated
(non-supercharged) reciprocating engines in that
maximum available power decreases almost as a direct
function of increased altitude.
Although power will decrease as the airplane climbs
to higher altitudes, engine efficiency in terms of
specific fuel consumption (expressed as pounds of fuel
consumed per horsepower per hour) will be increased.
Decreased specific fuel consumption plus the
increased true airspeed at higher altitudes is a definite
advantage of a turboprop engine.
All turbine engines, turboprop or turbojet, are defined
by limiting temperatures, rotational speeds, and (in the
case of turboprops) torque. Depending on the
installation, the primary parameter for power setting
might be temperature, torque, fuel flow or r.p.m.
(either propeller r.p.m., gas generator (compressor)
r.p.m. or both). In cold weather conditions, torque
limits can be exceeded while temperature limits are
still within acceptable range. While in hot weather
conditions, temperature limits may be exceeded
without exceeding torque limits. In any weather, the
maximum power setting of a turbine engine is usually
obtained with the throttles positioned somewhat aft of
the full forward position. The transitioning pilot must
understand the importance of knowing and observing
limits on turbine engines. An overtemp or overtorque
condition that lasts for more than a very few seconds
can literally destroy internal engine components.
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14-3
TURBOPROP ENGINE TYPES
FIXED SHAFT
One type of turboprop engine is the fixed shaft
constant speed type such as the Garrett TPE331.
In this type engine, ambient air is
directed to the compressor section through the engine
inlet. An acceleration/diffusion process in the twostage
compressor increases air pressure and directs it
rearward to a combustor. The combustor is made up of
a combustion chamber, a transition liner, and a turbine
plenum. Atomized fuel is added to the air in the
combustion chamber. Air also surrounds the
combustion chamber to provide for cooling and
insulation of the combustor.
The gas mixture is initially ignited by high-energy
igniter plugs, and the expanding combustion gases
flow to the turbine. The energy of the hot, high
velocity gases is converted to torque on the main shaft
by the turbine rotors. The reduction gear converts the
high r.p.m.—low torque of the main shaft to low
r.p.m.—high torque to drive the accessories and the
propeller. The spent gases leaving the turbine are
directed to the atmosphere by the exhaust pipe.
Only about 10 percent of the air which passes through
the engine is actually used in the combustion process.
Up to approximately 20 percent of the compressed air
may be bled off for the purpose of heating, cooling,
cabin pressurization, and pneumatic systems. Over
half the engine power is devoted to driving the
compressor, and it is the compressor which can
potentially produce very high drag in the case of a
failed, windmilling engine.
In the fixed shaft constant-speed engine, the engine
r.p.m. may be varied within a narrow range of 96
percent to 100 percent. During ground operation, the
r.p.m. may be reduced to 70 percent. In flight, the
engine operates at a constant speed, which is
maintained by the governing section of the propeller.
Power changes are made by increasing fuel flow and
propeller blade angle rather than engine speed. An
increase in fuel flow causes an increase in temperature
and a corresponding increase in energy available to the
turbine. The turbine absorbs more energy and
transmits it to the propeller in the form of torque. The
increased torque forces the propeller blade angle to be
increased to maintain the constant speed. Turbine
temperature is a very important factor to be considered
in power production. It is directly related to fuel flow
and thus to the power produced. It must be limited
because of strength and durability of the material in the
combustion and turbine section. The control system
schedules fuel flow to produce specific temperatures
and to limit those temperatures so that the temperature
tolerances of the combustion and turbine sections are
not exceeded. The engine is designed to operate for its
entire life at 100 percent. All of its components, such
as compressors and turbines, are most efficient when
operated at or near the r.p.m. design point.
Planetary
Reduction Gears
Air
Inlet
First-Stage
Centrifugal
Compressor
Second-Stage
Centrifugal
Compressor
Reverse-Flow
Annular Combustion
Chamber
Three-Stage
Axial Turbine
Fuel
Nozzle
Igniter
Exhaust
Outlet
Figure 14-2. Fixed shaft turboprop engine.
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14-4
Powerplant (engine and propeller) control is achieved
by means of a power lever and a condition lever for
each engine. There is no mixture control
and/or r.p.m. lever as found on piston engine airplanes.
On the fixed shaft constant-speed turboprop engine,
the power lever is advanced or retarded to increase or
decrease forward thrust. The power lever is also used
to provide reverse thrust. The condition lever sets the
desired engine r.p.m. within a narrow range between
that appropriate for ground operations and flight.
Powerplant instrumentation in a fixed shaft turboprop
engine typically consists of the following basic
indicator.
• Torque or horsepower.
• ITT – interturbine temperature.
• Fuel flow.
• RPM.
Torque developed by the turbine section is measured
by a torque sensor. The torque is then reflected on a
cockpit horsepower gauge calibrated in horsepower
times 100. Interturbine temperature (ITT) is a
measurement of the combustion gas temperature
between the first and second stages of the turbine
section. The gauge is calibrated in degrees Celsius.
Propeller r.p.m. is reflected on a cockpit tachometer as
a percentage of maximum r.p.m. Normally, a vernier
indicator on the gauge dial indicates r.p.m. in 1 percent
graduations as well. The fuel flow indicator indicates
fuel flow rate in pounds per hour.
Propeller feathering in a fixed shaft constant-speed
turboprop engine is normally accomplished with the
condition lever. An engine failure in this type engine,
however, will result in a serious drag condition due to
the large power requirements of the compressor being
absorbed by the propeller. This could create a serious
airplane control problem in twin-engine airplanes
unless the failure is recognized immediately and the
Power Levers
Condition Levers
Figure 14-3. Powerplant controls—fixed shaft turboprop engine.
Figure 14-4. Powerplant instrumentation—fixed shaft
turboprop engine.
Ch 14.qxd 5/7/04 10:09 AM Page 14-4
14-5
affected propeller feathered. For this reason, the fixed
shaft turboprop engine is equipped with negative
torque sensing (NTS).
Negative torque sensing is a condition wherein
propeller torque drives the engine and the propeller is
automatically driven to high pitch to reduce drag. The
function of the negative torque sensing system is to
limit the torque the engine can extract from the
propeller during windmilling and thereby prevent large
drag forces on the airplane. The NTS system causes a
movement of the propeller blades automatically
toward their feathered position should the engine
suddenly lose power while in flight. The NTS system
is an emergency backup system in the event of sudden
engine failure. It is not a substitution for the feathering
device controlled by the condition lever.
SPLIT SHAFT/ FREE TURBINE ENGINE
In a free power-turbine engine, such as the Pratt &
Whitney PT-6 engine, the propeller is driven by a
separate turbine through reduction gearing. The
propeller is not on the same shaft as the basic engine
turbine and compressor. Unlike the fixed
shaft engine, in the split shaft engine the propeller can
be feathered in flight or on the ground with the basic
engine still running. The free power-turbine design
allows the pilot to select a desired propeller governing
r.p.m., regardless of basic engine r.p.m.
A typical free power-turbine engine has two
independent counter-rotating turbines. One turbine
drives the compressor, while the other drives
the propeller through a reduction gearbox. The
compressor in the basic engine consists of three axial
flow compressor stages combined with a single centrifugal
compressor stage. The axial and centrifugal
stages are assembled on the same shaft, and operate as
a single unit.
Inlet air enters the engine via a circular plenum near
the rear of the engine, and flows forward through the
successive compressor stages. The flow is directed
outward by the centrifugal compressor stage through
radial diffusers before entering the combustion
chamber, where the flow direction is actually reversed.
The gases produced by combustion are once again
reversed to expand forward through each turbine stage.
After leaving the turbines, the gases are collected in a
peripheral exhaust scroll, and are discharged to the
atmosphere through two exhaust ports near the front of
the engine.
Apneumatic fuel control system schedules fuel flow to
maintain the power set by the gas generator power
lever. Except in the beta range, propeller speed within
the governing range remains constant at any selected
propeller control lever position through the action of a
propeller governor.
The accessory drive at the aft end of the engine
provides power to drive fuel pumps, fuel control, oil
pumps, a starter/generator, and a tachometer
transmitter. At this point, the speed of the drive (N1) is
the true speed of the compressor side of the engine,
approximately 37,500 r.p.m.
Reduction
Gearbox
Propeller
Drive Shaft Fr ee (Power)
Tu r bine Compressor
Tu r bine
(Gas Producer)
Three Stage
Axial Flow
Compressor
Exhaust Outlet
Air Inlet
Centrifugal
Compressor
Igniter
Fuel Nozzle
Igniter
Fuel Nozzle
Accessory
Gearbox
Figure 14-5. Split shaft/free turbine engine.
Ch 14.qxd 5/7/04 10:09 AM Page 14-5
14-6
Powerplant (engine and propeller) operation is
achieved by three sets of controls for each engine: the
power lever, propeller lever, and condition lever.
The power lever serves to control engine
power in the range from idle through takeoff power.
Forward or aft motion of the power lever increases or
decreases gas generator r.p.m. (N1) and thereby
increases or decreases engine power. The propeller
lever is operated conventionally and controls the
constant-speed propellers through the primary
governor. The propeller r.p.m. range is normally from
1,500 to 1,900. The condition lever controls the flow
of fuel to the engine. Like the mixture lever in a
piston-powered airplane, the condition lever is located
at the far right of the power quadrant. But the condition
lever on a turboprop engine is really just an on/off
valve for delivering fuel. There are HIGH IDLE and
LOW IDLE positions for ground operations, but condition
levers have no metering function. Leaning is not
required in turbine engines; this function is performed
automatically by a dedicated fuel control unit.
Engine instruments in a split shaft/free turbine engine
typically consist of the following basic indicators.
• ITT (interstage turbine temperature) indicator.
• Torquemeter.
• Propeller tachometer.
• N1 (gas generator) tachometer.
• Fuel flow indicator.
• Oil temperature/pressure indicator.
Figure 14-6. Powerplant controls—split shaft/free turbine
engine.
Figure 14-7. Engine instruments—split shaft/free turbine
engine.
Ch 14.qxd 5/7/04 10:09 AM Page 14-6
14-7
The ITT indicator gives an instantaneous reading of
engine gas temperature between the compressor
turbine and the power turbines. The torquemeter
responds to power lever movement and gives an
indication, in foot-pounds (ft/lb), of the torque being
applied to the propeller. Because in the free turbine
engine, the propeller is not attached physically to the
shaft of the gas turbine engine, two tachometers are
justified—one for the propeller and one for the gas
generator. The propeller tachometer is read directly in
revolutions per minute. The N1 or gas generator is read
in percent of r.p.m. In the Pratt & Whitney PT-6
engine, it is based on a figure of 37,000 r.p.m. at 100
percent. Maximum continuous gas generator is limited
to 38,100 r.p.m. or 101.5 percent N1.
The ITT indicator and torquemeter are used to set
takeoff power. Climb and cruise power are established
with the torquemeter and propeller tachometer while
observing ITT limits. Gas generator (N1) operation is
monitored by the gas generator tachometer. Proper
observation and interpretation of these instruments
provide an indication of engine performance
and condition.
REVERSE THRUST AND BETA RANGE
OPERATIONS
The thrust that a propeller provides is a function of the
angle of attack at which the air strikes the blades, and
the speed at which this occurs. The angle of attack
varies with the pitch angle of the propeller.
So called “flat pitch” is the blade position offering
minimum resistance to rotation and no net thrust for
moving the airplane. Forward pitch produces forward
thrust—higher pitch angles being required at higher
airplane speeds.
The “feathered” position is the highest pitch angle
obtainable. The feathered position
produces no forward thrust. The propeller is generally
placed in feather only in case of in-flight engine failure
to minimize drag and prevent the air from using the
propeller as a turbine.
In the “reverse” pitch position, the engine/propeller
turns in the same direction as in the normal (forward)
pitch position, but the propeller blade angle is
positioned to the other side of flat pitch.
In reverse pitch, air is pushed away from the airplane
rather than being drawn over it. Reverse pitch results
in braking action, rather than forward thrust of the airplane.
It is used for backing away from obstacles when
taxiing, controlling taxi speed, or to aid in bringing the
airplane to a stop during the landing roll. Reverse pitch
does not mean reverse rotation of the engine. The
engine delivers power just the same, no matter which
side of flat pitch the propeller blades are positioned.
With a turboprop engine, in order to obtain enough
power for flight, the power lever is placed somewhere
between flight idle (in some engines referred to as
“high idle”) and maximum. The power lever directs
signals to a fuel control unit to manually select fuel.
The propeller governor selects the propeller pitch
needed to keep the propeller/engine on speed. This is
referred to as the propeller governing or “alpha” mode
of operation. When positioned aft of flight idle, however,
the power lever directly controls propeller blade
angle. This is known as the “beta” range of operation.
The beta range of operation consists of power lever
positions from flight idle to maximum reverse.
Power Prop Condition
Reverse
Beta
Idle
Feather
Normal
"Forward" Pitch
Feather
"Maximum Forward
Pitch"
Flat Pitch
Reverse Pitch
Fuel
Cut
Off
Reverse
Fuel
Cut
Off
Reverse Feather
Fuel
Cut
Off
Feather
Fuel
Cut
Off
Low
Idle
Flt
Idle
Low
Idle
Flt
Idle
Low
Idle
Flt
Idle
Low
Idle
Flt
Idle
Pull
Up
Figure 14-8. Propeller pitch angle characteristics.
Ch 14.qxd 5/7/04 10:09 AM Page 14-7
14-8
Beginning at power lever positions just aft of flight
idle, propeller blade pitch angles become progressively
flatter with aft movement of the power lever until they
go beyond maximum flat pitch and into negative pitch,
resulting in reverse thrust. While in a fixed shaft/
constant-speed engine, the engine speed remains
largely unchanged as the propeller blade angles
achieve their negative values. On the split shaft PT-6
engine, as the negative 5° position is reached, further
aft movement of the power lever will also result in a
progressive increase in engine (N1) r.p.m. until a
maximum value of about negative 11° of blade angle
and 85 percent N1 are achieved.
Operating in the beta range and/or with reverse thrust
requires specific techniques and procedures depending
on the particular airplane make and model. There are
also specific engine parameters and limitations for
operations within this area that must be adhered to. It
is essential that a pilot transitioning to turboprop
airplanes become knowledgeable and proficient in
these areas, which are unique to turbine-enginepowered
airplanes.
TURBOPROP AIRPLANE ELECTRICAL
SYSTEMS
The typical turboprop airplane electrical system is a
28-volt direct current (DC) system, which receives
power from one or more batteries and a starter/
generator for each engine. The batteries may either be
of the lead-acid type commonly used on pistonpowered
airplanes, or they may be of the
nickel-cadmium (NiCad) type. The NiCad battery
differs from the lead-acid type in that its output
remains at relatively high power levels for longer
periods of time. When the NiCad battery is depleted,
however, its voltage drops off very suddenly. When
this occurs, its ability to turn the compressor for engine
start is greatly diminished and the possibility of engine
damage due to a hot start increases. Therefore, it is
essential to check the battery’s condition before every
engine start. Compared to lead-acid batteries, highperformance
NiCad batteries can be recharged very
quickly. But the faster the battery is recharged, the
more heat it produces. Therefore, NiCad battery
equipped airplanes are fitted with battery overheat
annunciator lights signifying maximum safe and
critical temperature thresholds.
The DC generators used in turboprop airplanes double
as starter motors and are called “starter/generators.”
The starter/generator uses electrical power to produce
mechanical torque to start the engine and then uses the
engine’s mechanical torque to produce electrical power
after the engine is running. Some of the DC power
produced is changed to 28 volt 400 cycle alternating
current (AC) power for certain avionic, lighting,
and indicator synchronization functions. This is
accomplished by an electrical component called an
inverter.
The distribution of DC and AC power throughout the
system is accomplished through the use of power distribution
buses. These “buses” as they are called are
actually common terminals from which individual
electrical circuits get their power.
Buses are usually named for what they power (avionics
bus, for example), or for where they get their power
(right generator bus, battery bus). The distribution of
DC and AC power is often divided into functional
groups (buses) that give priority to certain equipment
5 GEAR WARN
5 TRIM INDICATOR
3 TRIM ELEVATOR
5 TRIM AILERON
5 STALL WARNING
5 ACFT ANN-1
5 L TURN & BANK
5 TEMP OVRD
5 HP EMER L & R
5 FUEL QUANTITY
5 L ENGINE GAUGE
5 R ENGINE GAUGE
5 MISC ELEC
5 LDG LT MOTOR
5 BLEED L
3 WSHLD L
3 LIGHTS AUX
5 FUEL FLOW
POWER DISTRIBUTION BUS
Figure 14-9.Typical individual power distribution bus.
Ch 14.qxd 5/7/04 10:09 AM Page 14-8
14-9
during normal and emergency operations. Main buses
serve most of the airplane’s electrical equipment.
Essential buses feed power to equipment having top
priority.
Multiengine turboprop airplanes normally have
several power sources—a battery and at least one
generator per engine. The electrical systems are
usually designed so that any bus can be energized by
any of the power sources. For example, a typical
system might have a right and left generator buses
powered normally by the right and left engine-driven
generators. These buses will be connected by a
normally open switch, which isolates them from each
other. If one generator fails, power will be lost to its
bus, but power can be restored to that bus by closing a
bus tie switch. Closing this switch connects the buses
and allows the operating generator to power both.
Power distribution buses are protected from short
circuits and other malfunctions by a type of fuse called
a current limiter. In the case of excessive current
supplied by any power source, the current limiter will
open the circuit and thereby isolate that power source
and allow the affected bus to become separated from
the system. The other buses will continue to operate
normally. Individual electrical components are
connected to the buses through circuit breakers. A
circuit breaker is a device which opens an electrical
circuit when an excess amount of current flows.
PRIMARY
INVERTER
SECONDARY
INVERTER
LEFT
MAIN
BUS
RIGHT
MAIN
BUS
LEFT
ESSENTIAL
BUS
RIGHT
ESSENTIAL
BUS
AMPS
0
100
200
300
400 DC
VOLTS
0
28
35
AMPS
0
100
200
300
400
REGULATOR REGULATOR
LEFT
GENERATOR
BUS
BATTERY
CHARGING
BUS
RIGHT
GENERATOR
BUS
LEFT
GENERATOR/
STARTER
LEFT
GENERATOR/
STARTER
G.P.U.
LEFT
BATTERY
RIGHT
BATTERY
OVER
VOLTAGE
CUTOUT
Current Limiter
Circuit Breaker
Bus
Figure 14-10. Simplified schematic of turboprop airplane electrical system.
Ch 14.qxd 5/7/04 10:09 AM Page 14-9
14-10
OPERATIONAL CONSIDERATIONS
As previously stated, a turboprop airplane flies just like
any other piston engine airplane of comparable size
and weight. It is in the operation of the engines and
airplane systems that makes the turboprop airplane
different from its piston engine counterpart. Pilot
errors in engine and/or systems operation are the most
common cause of aircraft damage or mishap. The time
of maximum vulnerability to pilot error in any gas
turbine engine is during the engine start sequence.
Turbine engines are extremely heat sensitive. They
cannot tolerate an overtemperature condition for more
than a very few seconds without serious damage being
done. Engine temperatures get hotter during starting
than at any other time. Thus, turbine engines have
minimum rotational speeds for introducing fuel into
the combustion chambers during startup. Hypervigilant
temperature and acceleration monitoring on
the part of the pilot remain crucial until the engine is
running at a stable speed. Successful engine starting
depends on assuring the correct minimum battery
voltage before initiating start, or employing a ground
power unit (GPU) of adequate output.
After fuel is introduced to the combustion chamber
during the start sequence, “light-off” and its associated
heat rise occur very quickly. Engine temperatures may
approach the maximum in a matter of 2 or 3 seconds
before the engine stabilizes and temperatures fall into
the normal operating range. During this time, the pilot
must watch for any tendency of the temperatures to
exceed limitations and be prepared to cut off fuel to
the engine.
An engine tendency to exceed maximum starting
temperature limits is termed a hot start. The temperature
rise may be preceded by unusually high initial fuel
flow, which may be the first indication the pilot has
that the engine start is not proceeding normally.
Serious engine damage will occur if the hot start is
allowed to continue.
A condition where the engine is accelerating more
slowly than normal is termed a hung start or false
start. During a hung start/false start, the engine may
1. Before Takeoff
Checks – Completed
2. Lineup Checks – Completed
Heading Bug – Runway Heading
Command Bars – 10 Degrees Up
3. Power – Set
850 ITT / 650 HP
Max: 923 ITT / 717.5 HP
7. Ign Ovrd – Off
6. Gear Up
8. After T/O
Checklist
Yaw Damp
– On
9. Climb Power – Set
850 ITT / 650 HP
98 – 99% RPM
11. Climb Speed – Set
Climb Checks –
Completed
10. Prop Sync – On
These are merely typical procedures. The
pilot maintains his or her prerogative to
modify configuration and airspeeds as
required by existing conditions, as long as
compliance with the FAA approved Airplane
Flight Manual is assured.
NOTE:
5. Rotate at 96 – 100 KIAS
4. Annunciators – Check
Engine Inst. – Check
PRESSURE
ALTITUDE
FT
Sea Level
CLIMB
SPEED
KIAS
139
139
134
128
123
118
113
112
5,000
10,000
15,000
20,000
25,000
30,000
31,000
12. Cruise Checks – Completed
Figure 14-11. Example—typical turboprop airplane takeoff and departure profile.
Ch 14.qxd 5/7/04 10:09 AM Page 14-10
14-11
stabilize at an engine r.p.m. that is not high enough for
the engine to continue to run without help from the
starter. This is usually the result of low battery power
or the starter not turning the engine fast enough for it
to start properly.
Takeoffs in turboprop airplanes are not made by
automatically pushing the power lever full forward to
the stops. Depending on conditions, takeoff power may
be limited by either torque or by engine temperature.
Normally, the power lever position on takeoff will be
somewhat aft of full forward.
Takeoff and departure in a turboprop airplane
(especially a twin-engine cabin-class airplane) should
be accomplished in accordance with a standard takeoff
and departure “profile” developed for the particular
make and model. The takeoff and
departure profile should be in accordance with the
airplane manufacturer’s recommended procedures as
outlined in the FAA-approved Airplane Flight Manual
and/or the Pilot’s Operating Handbook (AFM/POH).
The increased complexity of turboprop airplanes
makes the standardization of procedures a necessity
for safe and efficient operation. The transitioning pilot
should review the profile procedures before each
takeoff to form a mental picture of the takeoff and
departure process.
For any given high horsepower operation, the pilot can
expect that the engine temperature will climb as
altitude increases at a constant power. On a warm or
hot day, maximum temperature limits may be reached
at a rather low altitude, making it impossible to
maintain high horsepower to higher altitudes. Also, the
engine’s compressor section has to work harder with
decreased air density. Power capability is reduced by
high-density altitude and power use may have to be
modulated to keep engine temperature within limits.
In a turboprop airplane, the pilot can close the
throttles(s) at any time without concern for cooling the
engine too rapidly. Consequently, rapid descents with
the propellers in low pitch can be dramatically steep.
Like takeoffs and departures, approach and landing
should be accomplished in accordance with a standard
approach and landing profile.
A stabilized approach is an essential part of the
approach and landing process. In a stabilized approach,
the airplane, depending on design and type, is placed
in a stabilized descent on a glidepath ranging from 2.5
to 3.5°. The speed is stabilized at some reference from
the AFM/POH—usually 1.25 to 1.30 times the stall
speed in approach configuration. The descent rate is
stabilized from 500 feet per minute to 700 feet per
minute until the landing flare.
2. Arrival 160 KIAS
250 HP Level Flt –
Clean Config.
3. Begin Before
Landing Checklist
7. Final
120 KIAS
Flaps – As Desired
6. Base
Before Landing Checklist
120 – 130 KIAS
8. Short Final
110 KIAS
Gear – Recheck
Down
9. Threshold
96 – 100 KIAS
11. After Landing Checklist
10. Landing
Cond. Levers – Keep Full Fwd.
Power – Beta/Reverse
These are merely typical procedures. The
pilot maintains his or her prerogative to
modify configuration and airspeeds as
required by existing conditions, as long as
compliance with the FAA approved Airplane
Flight Manual is assured.
NOTE:
5. 130 – 140 KIAS
4. Midfield Downwind
140 – 160 KIAS
250 HP
Gear – Down
Flaps – Half
1. Leaving Cruise Altitude
Descent/Approach
Checklist
Figure 14-12. Example—typical turboprop airplane arrival and landing profile.
Ch 14.qxd 5/7/04 10:09 AM Page 14-11
14-12
Landing some turboprop airplanes (as well as some
piston twins) can result in a hard, premature
touchdown if the engines are idled too soon. This is
because large propellers spinning rapidly in low pitch
create considerable drag. In such airplanes, it may be
preferable to maintain power throughout the landing
flare and touchdown. Once firmly on the ground,
propeller beta range operation will dramatically reduce
the need for braking in comparison to piston airplanes
of similar weights.
TRAINING CONSIDERATIONS
The medium and high altitudes at which turboprop
airplanes are flown provide an entirely different
environment in terms of regulatory requirements,
airspace structure, physiological requirements, and
even meteorology. The pilot transitioning to turboprop
airplanes, particularly those who are not familiar with
operations in the high/medium altitude environment,
should approach turboprop transition training with this
in mind. Thorough ground training should cover all
aspects of high/medium altitude flight, including the
flight environment, weather, flight planning and
navigation, physiological aspects of high-altitude
flight, oxygen and pressurization system operation,
and high-altitude emergencies.
Flight training should prepare the pilot to demonstrate
a comprehensive knowledge of airplane performance,
systems, emergency procedures, and operating
limitations, along with a high degree of proficiency in
performing all flight maneuvers and in-flight
emergency procedures.
The training outline below covers the minimum
information needed by pilots to operate safely at high
altitudes.
a. Ground Training
(1) The High-Altitude Flight Environment
(a) Airspace
(b) Title 14 of the Code of Federal Regulations
(14 CFR) section 91.211, requirements for
use of supplemental oxygen
(2) Weather
(a) The atmosphere
(b) Winds and clear air turbulence
(c) Icing
(3) Flight Planning and Navigation
(a) Flight planning
(b) Weather charts
(c) Navigation
(d) Navaids
(4) Physiological Training
(a) Respiration
(b) Hypoxia
(c) Effects of prolonged oxygen use
(d) Decompression sickness
(e) Vision
(f) Altitude chamber (optional)
(5) High-Altitude Systems and Components
(a) Oxygen and oxygen equipment
(b) Pressurization systems
(c) High-altitude components
(6) Aerodynamics and Performance Factors
(a) Acceleration
(b) G-forces
(c) MACH Tuck and MACH Critical (turbojet
airplanes)
(7) Emergencies
(a) Decompression
(b) Donning of oxygen masks
(c) Failure of oxygen mask, or complete loss of
oxygen supply/system
(d) In-flight fire
(e) Flight into severe turbulence or thunderstorms
b. Flight Training
(1) Preflight Briefing
(2) Preflight Planning
(a) Weather briefing and considerations
(b) Course plotting
(c) Airplane Flight Manual
(d) Flight plan
(3) Preflight Inspection
(a) Functional test of oxygen system, including
the verification of supply and pressure, regulator
operation, oxygen flow, mask fit, and
cockpit and air traffic control (ATC)
communication using mask microphones
(4) Engine Start Procedures, Runup, Takeoff, and
Initial Climb
(5) Climb to High Altitude and Normal Cruise
Operations While Operating Above 25,000
Feet MSL
(6) Emergencies
(a) Simulated rapid decompression, including
the immediate donning of oxygen masks
(b) Emergency descent
(7) Planned Descents
(8) Shutdown Procedures
(9) Postflight Discussion
Ch 14.qxd 5/7/04 10:09 AM Page 14-12
15-1
GENERAL
This chapter contains an overview of jet powered
airplane operations. It is not meant to replace any
portion of a formal jet airplane qualification course.
Rather, the information contained in this chapter is
meant to be a useful preparation for and a supplement
to formal and structured jet airplane qualification
training. The intent of this chapter is to provide
information on the major differences a pilot will
encounter when transitioning to jet powered airplanes.
In order to achieve this in a logical manner, the major
differences between jet powered airplanes and piston
powered airplanes have been approached by
addressing two distinct areas: differences in
technology, or how the airplane itself differs; and
differences in pilot technique, or how the pilot deals
with the technological differences through the
application of different techniques. If any of the
information in this chapter conflicts with information
contained in the FAA-approved Airplane Flight
Manual for a particular airplane, the Airplane Flight
Manual takes precedence.
JET ENGINE BASICS
A jet engine is a gas turbine engine. A jet engine
develops thrust by accelerating a relatively small mass
of air to very high velocity, as opposed to a propeller,
which develops thrust by accelerating a much larger
mass of air to a much slower velocity.
As stated in Chapter 14, both piston and gas turbine
engines are internal combustion engines and have a
similar basic cycle of operation; that is, induction,
compression, combustion, expansion, and exhaust. Air
is taken in and compressed, and fuel is injected and
burned. The hot gases then expand and supply a
surplus of power over that required for compression,
and are finally exhausted. In both piston and jet
engines, the efficiency of the cycle is improved by
increasing the volume of air taken in and the
compression ratio.
Part of the expansion of the burned gases takes place in
the turbine section of the jet engine providing the
necessary power to drive the compressor, while the
remainder of the expansion takes place in the nozzle of
the tail pipe in order to accelerate the gas to a high
velocity jet thereby producing thrust.
In theory, the jet engine is simpler and more directly
converts thermal energy (the burning and expansion of
gases) into mechanical energy (thrust). The piston or
reciprocating engine, with all of its moving parts, must
convert the thermal energy into mechanical energy and
then finally into thrust by rotating a propeller.
One of the advantages of the jet engine over the piston
engine is the jet engine’s capability of producing much
greater amounts of thrust horsepower at the high
altitudes and high speeds. In fact, turbojet engine
efficiency increases with altitude and speed.
Direction of Flight
Air
Enters
Inlet
Duct Exhaust
Combustion
Drive Shaft
Six-Stage Compressor
TURBOJET ENGINE
Two-Stage
Turbine
Figure 15-1. Basic turbojet engine.
Ch 15.qxd 5/7/04 10:22 AM Page 15-1
15-2
Although the propeller driven airplane is not nearly as
efficient as the jet, particularly at the higher altitudes
and cruising speeds required in modern aviation, one
of the few advantages the propeller driven airplane has
over the jet is that maximum thrust is available almost
at the start of the takeoff roll. Initial thrust output of the
jet engine on takeoff is relatively lower and does not
reach peak efficiency until the higher speeds. The fanjet
or turbofan engine was developed to help compensate
for this problem and is, in effect, a compromise
between the pure jet engine (turbojet) and the propeller
engine.
Like other gas turbine engines, the heart of the turbofan
engine is the gas generator—the part of the engine
that produces the hot, high-velocity gases. Similar to
turboprops, turbofans have a low pressure turbine section
that uses most of the energy produced by the gas
generator. The low pressure turbine is mounted on a
concentric shaft that passes through the hollow shaft of
the gas generator, connecting it to a ducted fan at the
front of the engine.
Air enters the engine, passes through the fan, and splits
into two separate paths. Some of it flows around—
bypasses—the engine core, hence its name, bypass
air. The air drawn into the engine for the gas generator
is the core airflow. The amount of air that bypasses
the core compared to the amount drawn into the gas
generator determines a turbofan’s bypass ratio.
Turbofans efficiently convert fuel into thrust because
they produce low pressure energy spread over a large
fan disk area. While a turbojet engine uses all of the
gas generator’s output to produce thrust in the form of
a high-velocity exhaust gas jet, cool, low-velocity
bypass air produces between 30 percent and 70 percent
of the thrust produced by a turbofan engine.
The fan-jet concept increases the total thrust of the jet
engine, particularly at the lower speeds and altitudes.
Although efficiency at the higher altitudes is lost (turbofan
engines are subject to a large lapse in thrust with
increasing altitude), the turbofan engine increases
acceleration, decreases the takeoff roll, improves initial
climb performance, and often has the effect of
decreasing specific fuel consumption.
OPERATING THE JET ENGINE
In a jet engine, thrust is determined by the amount of
fuel injected into the combustion chamber. The power
controls on most turbojet and turbofan powered airplanes
consist of just one thrust lever for each engine,
because most engine control functions are automatic.
The thrust lever is linked to a fuel control and/or electronic
engine computer that meters fuel flow based
upon r.p.m., internal temperatures, ambient conditions,
and other factors.
In a jet engine, each major rotating section usually has
a separate gauge devoted to monitoring its speed of
rotation. Depending on the make and model, a jet
engine may have an N1 gauge that monitors the low
pressure compressor section and/or fan speed in
turbofan engines. The gas generator section may be
monitored by an N2 gauge, while triple spool engines
may have an N3 gauge as well. Each engine section
rotates at many thousands of r.p.m. Their gauges
therefore are calibrated in percent of r.p.m. rather than
actual r.p.m., for ease of display and interpretation.
Direction of Flight
Inlet
Air
Exhaust
Combustion
Combustion
Fan Air
Fan Air
Figure 15-2.Turbofan engine.
Ch 15.qxd 5/7/04 10:22 AM Page 15-2
15-3
The temperature of turbine gases must be closely
monitored by the pilot. As in any gas turbine engine,
exceeding temperature limits, even for a very few
seconds, may result in serious heat damage to turbine
blades and other components. Depending on the make
and model, gas temperatures can be measured at a
number of different locations within the engine. The
associated engine gauges therefore have different
names according to their location. For instance:
• Exhaust Gas Temperature (EGT)—the temperature
of the exhaust gases as they enter the tail
pipe, after passing through the turbine.
• Turbine Inlet Temperature (TIT)—the temperature
of the gases from the combustion section of
the engine as they enter the first stage of the turbine.
TIT is the highest temperature inside a gas
turbine engine and is one of the limiting factors
of the amount of power the engine can produce.
TIT, however, is difficult to measure. EGT
therefore, which relates to TIT, is normally the
parameter measured.
• Interstage Turbine Temperature (ITT)—the
temperature of the gases between the high
pressure and low pressure turbine wheels.
• Turbine Outlet Temperature (TOT)—like EGT,
turbine outlet temperature is taken aft of the
turbine wheel(s).
JET ENGINE IGNITION
Most jet engine ignition systems consist of two igniter
plugs, which are used during the ground or air starting
of the engine. Once the start is completed, this ignition
either automatically goes off or is turned off, and from
this point on, the combustion in the engine is a
continuous process.
CONTINUOUS IGNITION
An engine is sensitive to the flow characteristics of the
air that enters the intake of the engine nacelle. So long
as the flow of air is substantially normal, the engine
will continue to run smoothly. However, particularly
with rear mounted engines that are sometimes in a
position to be affected by disturbed airflow from the
wings, there are some abnormal flight situations that
could cause a compressor stall or flameout of the
engine. These abnormal flight conditions would usually
be associated with abrupt pitch changes such as
might be encountered in severe turbulence or a stall.
In order to avoid the possibility of engine flameout
from the above conditions, or from other conditions
that might cause ingestion problems such as heavy
rain, ice, or possible bird strike, most jet engines are
equipped with a continuous ignition system. This system
can be turned on and used continuously whenever
the need arises. In many jets, as an added precaution,
this system is normally used during takeoffs and landings.
Many jets are also equipped with an automatic
ignition system that operates both igniters whenever
the airplane stall warning or stick shaker is activated.
FUEL HEATERS
Because of the high altitudes and extremely cold outside
air temperatures in which the jet flies, it is possible
to supercool the jet fuel to the point that the small
Figure 15-3. Jet engine power controls.
Figure 15-4. Jet engine r.p.m. gauges.
Ch 15.qxd 5/7/04 10:22 AM Page 15-3
15-4
particles of water suspended in the fuel can turn to ice
crystals and clog the fuel filters leading to the engine.
For this reason, jet engines are normally equipped with
fuel heaters. The fuel heater may be of the automatic
type which constantly maintains the fuel temperature
above freezing, or they may be manually controlled by
the pilot from the cockpit.
SETTING POWER
On some jet airplanes, thrust is indicated by an engine
pressure ratio (EPR) gauge. Engine pressure ratio can
be thought of as being equivalent to the manifold
pressure on the piston engine. Engine pressure ratio is
the difference between turbine discharge pressure and
engine inlet pressure. It is an indication of what the
engine has done with the raw air scooped in. For
instance, an EPR setting of 2.24 means that the
discharge pressure relative to the inlet pressure is
2.24 : 1. On these airplanes, the EPR gauge is the
primary reference used to establish power settings.
Fan speed (N1) is the primary indication of thrust on
most turbofan engines. Fuel flow provides a secondary
thrust indication, and cross-checking for proper fuel
flow can help in spotting a faulty N1 gauge. Turbofans
also have a gas generator turbine tachometer (N2).
They are used mainly for engine starting and some
system functions.
In setting power, it is usually the primary power
reference (EPR or N1) that is most critical, and will be
the gauge that will first limit the forward movement of
the thrust levers. However, there are occasions where
the limits of either r.p.m. or temperature can be
exceeded. The rule is: movement of the thrust levers
must be stopped and power set at whichever the limits
of EPR, r.p.m., or temperature is reached first.
THRUST TO THRUST LEVER
RELATIONSHIP
In a piston engine propeller driven airplane, thrust is
proportional to r.p.m., manifold pressure, and propeller
blade angle, with manifold pressure being the most
dominant factor. At a constant r.p.m., thrust is
proportional to throttle lever position. In a jet engine,
however, thrust is quite disproportional to thrust lever
position. This is an important difference that the pilot
transitioning into jet powered airplanes must become
accustomed to.
On a jet engine, thrust is proportional to r.p.m. (mass
flow) and temperature (fuel/air ratio). These are
matched and a further variation of thrust results from
the compressor efficiency at varying r.p.m. The jet
engine is most efficient at high r.p.m., where the
engine is designed to be operated most of the time. As
r.p.m. increases, mass flow, temperature, and efficiency
also increase. Therefore, much more thrust is
produced per increment of throttle movement near the
top of the range than near the bottom.
One thing that will seem different to the piston pilot
transitioning into jet powered airplanes is the rather
large amount of thrust lever movement between the
flight idle position and full power as compared to the
small amount of movement of the throttle in the piston
engine. For instance, an inch of throttle movement on
a piston may be worth 400 horsepower wherever the
throttle may be. On a jet, an inch of thrust lever
movement at a low r.p.m. may be worth only 200
pounds of thrust, but at a high r.p.m. that same inch of
movement might amount to closer to 2,000 pounds of
thrust. Because of this, in a situation where
significantly more thrust is needed and the jet engine
is at low r.p.m., it will not do much good to merely
“inch the thrust lever forward.” Substantial thrust lever
movement is in order. This is not to say that rough or
abrupt thrust lever action is standard operating
procedure. If the power setting is already high, it may
take only a small amount of movement. However,
there are two characteristics of the jet engine that work
against the normal habits of the piston engine pilot.
One is the variation of thrust with r.p.m., and the other
is the relatively slow acceleration of the jet engine.
VARIATION OF THRUST WITH RPM
Whereas piston engines normally operate in the range
of 40 percent to 70 percent of available r.p.m., jets
operate most efficiently in the 85 percent to 100
percent range, with a flight idle r.p.m. of 50 percent to
60 percent. The range from 90 percent to 100 percent
in jets may produce as much thrust as the total
available at 70 percent.
SLOW ACCELERATION OF THE JET
ENGINE
In a propeller driven airplane, the constant speed
propeller keeps the engine turning at a constant r.p.m.
within the governing range, and power is changed by
varying the manifold pressure. Acceleration of the
Figure 15-5. EPR gauge.
