Flight.Training
AVIATION COURSE CONTENTS Home Contents The Airplane ..................Illustrates basic airplane parts. Lift ................................Illustrates the Principles of Lift. Basic Aerodynamics.......Basic Flight principles. Pitot and Static Systems .Airspeed, Altimeter, Vertical Speed Gyroscopic Instruments..Attitude Indicator, Turn Indicators. Magnetic Compass.........Magnetic Compass and Compass Errors Engine Operation...........Throttle and Mixture Control Fuel System...................Components of the fuel system. Induction System...........Carbuerator Operation. Electrical System............General Electrical Busses and Breakers. Propulsion System .........Propeller and Controls. Stall Warning System .....Warnings of Impending Stall. Weight and Balance........How to calculate W/B. Aircraft Performance......Effects of air density on performance. Types of Airspace...........Airspace Definition, Airport Types and Flight Rules. Aeronautical Charts........Aeronautical Chart Synbols and their Meaning. Airport and AIM Data ...Airport Markings, Signs and Aircraft Operations. Navigation Methods .......Pilotage, VOR, LORAN, GPS Nav. Planning the Flight....... ....Terminology and Procedures. Principles of Weather......Air Masses, Fronts, Clouds, Fog, Ice. Weather Reports and Services ..WX Report Interpretation. Other Aviation Publications ....Important Information to consult. FAA Regulations...........Rules of the Road. Preflight Briefing....How to get preflight briefing from FAA. OTHER AVIATION STUFF OF INTEREST FAA Test Questions....FAA Test Prep Questions Guide to Meterology ... Basic Meterology and Weather Info Other Aviation Links ....A whole host of aviation information. Weather Links.............Actual weather & Educational material. Student Pilot Guide......Information concerning student training. http://www.uncletom2000.com/gs/contents.htm (1 of 2) Flight Planning Data .....Fuel Prices, Planning Software, etc. LANDINGS................A host of aviation links. AVIATION COURSE CONTENTS http://www.uncletom2000.com/gs/contents.htm (2 of 2) The Airplane Major Airplane Components A single engine airplane typically used by student pilots is shown above. The fuselage is the structure which houses the Pilot and passengers, as well as the instrument panel and controls. The Wings provide the major LIFT for the airplane. Ailerons are located near the outer portion of the wing. The ailerons operate in opposition to each other; i.e. when the left aileron is up, the right aileron is down. This configuration causes the aircraft to "roll" to the left. Placing the ailerons in the opposite position causes a roll to the right. Flaps are located on the inboard end of the wing, next to the fuselage. Flaps can be deployed during decent to landing to provide increased lift, and increased drag to slow the aircraft. Flaps permit a steeper decent without build-up of excessive speed. The horizontal stabilizer and elevators are located on the tail of the fuselage. The horizontal stabilizers are fixed. The elevators are hinged at the aft end of the stabilizers. The Elevators control the pitch (noseup or nose-down ) state of the aircraft. The vertical stabilizer is attached to the tail of the fuselage. The Rudder is hinged to the aft end of the vertical stabilizer. The Rudder permits the pilot to move the tail of the aircraft left or right by use of the rudder pedals in the cockpit.. The landing gear shown above is a "tricycle" type, which is comprised of the Main Gear and the Nose Wheel. Some aircraft, however, have a tail wheel instead of the nose wheel. These aircraft are usually of earlier design, and are lovingly called "tail draggers" by many pilots. Most "training type" aircraft have http://www.uncletom2000.com/gs/airplane.htm (1 of 2) "fixed" landing gear; i.e. the gear remains stationary in flight and cannot be "retracted". Higher performance aircraft usually are equipped with "retractable" landing gear to reduce aerodynamic drag during flight.. The engine and propeller provide the forward thrust necessary to attain sufficient speed to achieve flight.The engine is housed under the cowl, at the nose of the aircraft.
Some aircraft have secondary control surfaces called Trim Tabs. These tabs can be located on the
elevators to aid in maintaining pitch of the aircraft. Other tabs can also be located on the ailerons and
rudder to aid in stabilizing the roll and yaw characteristics as an assist in maintaining the flight
configuration selected by the pilot.
Axes of Rotation
The aircraft is free to move around 3 different axes.
l The LONGITUDINAL AXIS is an imaginary line( line X - X ) from nose to tail. Rotation around
the LONGITUDINAL axis is called ROLL. Roll is controlled by the ailerons. When the pilot turns
the CONTROL WHEEL (or in some aircraft a control stick), to the RIGHT the right aileron
deflects upward, while the left aileron deflects downward. This causes the right wing to produce
less lift and the left wing to produce greater lift. This unequal lift causes the airplane to ROLL to
the right as long as the ailerons remain in this condition. In order to stop the roll, it is necessary to
neutralize the ailerons. The aircraft will remain in a "banked" condition until rolled back to level
by application of opposite aileron action.
l The LATERAL AXIS is an imaginary line ( line Y-Y ) from wingtip to wingtip. Rotation around
the LATERAL axis is called PITCH. The "nose up" or "nose down" pitch of the aircraft is
controlled by use of the elevator surfaces of the tail. When the pilot pulls the control wheel (or
control stick) rearward, the elevators deflect upward, forcing the tail downward. This is referred to
as a "nose up attitude". When the control wheel or stick is moved forward, the opposite reactions
occur, causing a "nose down attitude".
l The VERTICAL AXIS is an imaginary vertical line (line Z_Z )running through the center of
gravity of the aircraft. Rotation around the VERTICAL axis is called YAW. Yaw is predominately
controlled by use of the rudder. Left rudder pedal depression in the cockpit deflects the rudder
surface to the left. This causes the tail of the aircraft to move to the right, creating a yaw to the left
about the vertical axis. Application of right rudder similarly causes yaw to the right.
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The Airplane
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LIFT
When Lift is mentioned, most people think primarily of the wings. However there are several other
surfaces which generate lift, although not necessarily in an upward direction. These are the Propeller,
Elevators, Rudder, Ailerons, and Flaps.
l Principles of Lift The structure of the wing best demonstrates the principle of airfoil lift. In the 19th century a scientist
named Bernoulli discovered that the intenal pressure of a fluid (liquid or gas) reduces the faster the fluid
flows. If you take a tube, and make the tube smaller in diameter in the middle, this creates a "neckeddown" section called a venturi. When air is forced through the pipe, as much air has to come out the exit
as goes in the tube entrance. The air in the venturi section must travel faster to get through. Bernoulli
found that the pressure at the venturi section was less than at the two ends of the pipe. This is because the
speed of the air through the venturi section is traveling faster than at the ends of the tube.
l The Airfoil
The shape of a wing is called an AIRFOIL. Usually the bottom of the wing is flat or nearly flat. The top
of the wing is curved, with the wing being thicker at the front edge of the wing, and tapering to a thin
surface at the trailing edge of the wing.
When a wing airfoil surface passes through the atmosphere, the atoms of the air on the top of the airfoil
(shown as minus) must travel faster than their cousins (shown as plus) passing along the lower and flater
surface. This occurs because the distance the air must pass over the curved top of the wing is longer than
the distance along the lower surface. According to the Bernoulli Principle, the pressure above the wing is
less than the pressure of air below it. Consequently, a pressure difference between the lower and upper
surfaces exist. This results in LIFT being produced. The amount of lift depends on the airfoil design and
the speed of the air over its surfaces.
l Camber
The curved surface of an airfoil is called Camber. It can be both Positive and Negative. The curved upper
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surface of a wing is called Positive Camber. If the lower surface of the airfoil is curved downward, this
would constitute a negative camber.
l Chord
The chord of a wing is an imaginary line from the leading edge to the trailing edge of the wing. The term
is used in the definition of "Angle of Incidence" and "Angle of Attack" (defined later).
l Angle Of Incidence
The angle which the chord of the wing makes with the longitudinal centerline of the aircraft is known as
the Angle of Incidence. This angle in a given aircraft never changes. It is fixed by the construc tion of the
aircraft.
l Angle Of Attack
As the aircraft passes through the air it traverses a particular line of flight. The air passing by the surfaces
of the aircraft in the opposite direction of travel is called the Relative Wind. The angle which the wing
chord makes with this Relative Wind is called Angle of Attack. An increase in angle of attack increases
both lift and drag. If the angle becomes to great, it will pass the Critical Angle of Attack. This is a point
where the airflow over the wing becomes so disturbed that the wing ceases to produce lift. The wing then
enters into a Stalled condition. Stalls will be described more fully later in this chapter.
l Center of Pressure
Even though the lift of an airfoil is distributed along its surface, the resultant force of all the lift forces
can be considered to be at single point along the wing known as the Center of Pressure.
l Center of Lift
The Center of Lift( shown as CL in the diagram) is the same point as the Center of Pressure. You can
think of all the lift of the wing as being a single force concentrated at this point on the wing.
l Dihedral
When you stand in front of an aircraft, looking toward the tail, the wings are usually higher at the wing
tips than at the wing root (where the wing attaches to the fuselage). This upward angle from wing root to
tip is called DIHEDRAL.
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On an aircraft with dihedral, when one wing drops, it will produce slightly greater lift than the other
wing. The aircraft tends to return to a level status providing lateral stability to the aircraft.
Back to Home Back to Table of Conents To Aerodynamics
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Aerodynamics
Principles of Aerodynamics
Flight involves a balance of forces. These forces are THRUST, DRAG, LIFT and WEIGHT.
When Thrust and Drag are equal, the speed of the
aircraft through the air (airspeed) will remain
constant in smooth air. When Lift and Weight are
equal, the aircraft will neither ascend or decend.
Attitude
The Attitude of an aircraft refers to it's relationship to the ground. When in a level attitude, the
longitudinal centerline of the aircraft is approximately paralell to the earth's surface. In this attitude, the
horizon will appear to be just about on the nose of the aircraft( i.e. the top of the engine cowling is
approximately aligned with the horizon).
When the nose of the aircraft is above the horizon, this is called a nose high attitude. If the nose is below
the horizon, the aircraft is in a nose low attitude.
Center Of Gravity
The weight of the airplane, pilot and
passengers, fuel and baggage is distributed
throughout the aircraft, as shown by the small
downward arrows in the diagram. However,
the total weight can be considered as being
concentrated at one given point, shown by the
larger downward arrow. This point is referred
to as the Center of Gravity. If the plane were
suspended by a rope attached at the center of
gravity ( referred to as the CG) it would be in
balance.
The Center of Gravity (CG) is affected by the
way an aircraft is loaded. For example, if in a
4 place aircraft, there are 2 rather large
individuals in the front seats, and no rear seat passengers or baggage, the CG will be somewhat toward
the nose of the aircraft. If however, the 2 front seat passengers are smaller, with 2 large individuals in the
rear seats, and a lot of baggage in the rear baggage compartment, the CG will be located more aft.
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Every aircraft has a maximum forward and rearward CG position at which the aircraft is designed to
operate. Operating an aircraft with the CG outside these limits affects the handling characteristics of the
aircraft. Serious "out of CG" conditions can be dangerous.
Aircraft Balance
An aircraft in straight and level flight is similar to a childs "teeter-totter". There is a balance point in the
middle (called a fulcrum), with weight on both sides of the fulcrum. For the "teeter-totter" to be in
balance, the downward forces on both sides of the fulcrum must be equal.
In the diagram at right, the fulcrum of an aircraft in
flight is the center of lift. Generally the CG is
forward of the Center of Lift, causing the aircraft to
naturally want to "nose down". The elevator located
at the aft end of the aircraft provides the counterbalancing force to provide a level attitude in normal
flight. Normally, the pilot will "trim" the elevators,
by use of the trim tab control in the cockpit, to
cause the elevators to provide the correct elevator
balance force to relieve the pilot from constant
elevator control.
You can readily see that loading of the aircraft, which affects the CG, is a critical consideration in
properly balancing the aircraft and it's controllability.
If the pilot pulls back on the control wheel, an "up-elevator" condition results. This forces the tail
downward, causing the aircraft to assume a "nose up" attitude. Likewise, a forward movement of the
control wheel by the pilot causes a "down elevator" state. This causes the tail to rise, forcing the aircraft
into a "nose low" attitude. By use of the elevator trim control (a small wheel or crank in the cockpit), the
pilot can cause the aircraft to remain in a nose-up, level, or nose down attitude.
As can be seen in the diagram above, when the CG is forward, a greater downward force is required by
the elevators to produce a level attitude. Likewise, when the CG is aft, the elevators must produce less
downward force to maintain level flight. NOTE: If the CG gets behind the Center of lift (the fulcrum) the
aircraft becomes unstable because the CG is aft of the fulcrum. IT MAY BE POSSIBLE TO EXCEED
THE TRIM CAPABILITY OF THE ELEVATORS SUCH THAT THE AIRCRAFT ALWAYS WANTS
TO NOSE UP, AND BE UNSTABLE. Therefore the pilot must pay attention to proper loading of the
aircraft. This will be discussed in greater detain under the subject of Weight and Balance.
Effects Of Attitude Change
Aerodynamics
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When the wing is in a given attitude with respect to the Relative Wind (R W) as shown in the diagram
below, the wing produces a Vertical Lift Force (LIFT) which is perpendicular to the Relative Wind..
There is also a DRAG component operating parallel
to the Relative Wind in opposition to the forward
motion of the wing. Drag is created as a natural part
of producing lift. These two forces intersect at a
point called the CL (center of lift}, or is also called
the CP (center of pressure]. The LIFT and DRAG
force vectors can be resolved into a single force
vector called the RESULTANT force.
Envision if the Angle of Attack is increased. The
Vertical Lift decreases in value, and the horizontal
force of Drag increases. Therefore, when a pilot
wants to slow the aircraft, the nose of the aircraft must be slowly raised into a greater "nose up" attitude,
causing drag to increase, thus slowing the aircraft. This increase of angle of attack has limits, however.
The wing design of most small aircraft, the wing has a "Critical Angle Of Attack" (somewhere around
18° to 20°) at which point the wing ceases to create sufficient lift to fly, and the wing STALLS. The air
flowing over the wing becomes so disturbed that adequate lift to sustain flight ceases, and the aircraft
pitches "nose down". This is a STALL.
The primary way to recover from a stall is to push the nose further downward, thus decreasing the Angle
Of Attack so that the wing flies again.
Also, envision in the diagram, when the pilot pushes the nose down by use of forward elevator, the Angle
of Atack decreases, thus decreasing the drag. Therefore, when power is held constant, the angle of attack
(nose high, level, or nose low) provides "Airspeed Control".
Assume for example, an aircraft has been cruising at 120 knots. When the aircraft enters the landing
pattern of an airport, the pilot may want to reduce speed to 90 knots. The pilot must reduce power to
prevent an altitude increase, and concurrently raise the nose of the aircraft so that the drag is increased
sufficiently to slow the aircraft to 90. Later, when on the final approach for landing, the pilot may wish to
slow even further, say to 70 knots. Power can be further reduced and the nose raised further, to again
increase drag. In addition, the pilot may add 10,20 or 30 degrees of flaps to add an additional drag and
lift.
The important point is that ATTITUDE is the primary control of airspeed; not THROTTLE! However, if
level flight is to be maintained, appropriate changes in power must be made whenever the pitch attitude
is made to prevent gaining or loosing altitude.
The Turn
Aerodynamics
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In order to turn the aircraft, it must be placed into a BANKED state, where one wing is high, the other
low. This state is pictured below.
In order to bank the aircraft, the pilot must turn the control wheel (or
move the control stick) to the left. The Right Aileron lowers This
increases the angle of attack of that part of the right wing, causing the
right wing to rise. At the same time, the Left Aileron raises. The
angle of attack of that part of the left wing decreases, causing the left
wing to lower. This increased lift of the Right and decreased lift of
the Left Wing causes the aircraft to roll to the Left.
NOTE: During the time the Right aileron is down, the right wing has MORE DRAG than does the left
wing. The effects of this unequal drag is discussed later under Adverse Yaw.
When the aircraft reaches the bank angle the pilot wishes, the ailerons must be neutralized. This causes
equal lift by left and right wing, and the aircraft roll stops. Basically, the aircraft will remain in this
banked attitude until the pilot rolls the aircraft back to level attitude by operating the control wheel ( or
stick) in the opposite direction.
Note in the diagram that some of theTotal Lift ( force T) goes into a Horizontal Force ( H ). This is the
force which pulls the aircraft in a circular motion (turn). Note also that the Vertical Lift ( force V)
becomes less. If the bank angle becomes large, say 45 degrees, the vertical lift is appreciably less. The
pilot may have to hold some up elevator and/or add power to prevent loosing altitude.
Adverse Yaw
During the time that the ailerons are activated, an unwanted effect occurs. In the left turn shown above
the pilot turns the control wheel to the left, raising the left aileron, and lowering the right aileron. The
intent is to turn left.
Unfortunately while the ailerons are activated, the left wing has less drag; the right wing has more drag.
This causes the airplane to want to turn to the Right, and not to the left. This tendency to turn in a
direction opposite to the intended turn direction is called ADVERSE YAW. So how does the pilot
overcome this tendency to initially turn in the wrong direction? He uses the Rudder. By applying just the
right amount of rudder in the direction of the turn, the pilot can offset the adverse yaw. When the pilot
does this correctly, applying just the right amount of rudder, a Coordinated turn results. If the pilot
applies too little or too much rudder, anUn-Coordinated turn results. How the quality of the turn is
measured will be covered in the Instruments section.
If the pilot uses too little rudder, the nose of the aircraft wants to stay yawed opposite the turn. The rest
of the aircraft wants to "slip" toward the inside of the turn.
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If the pilot applies too much rudder, the tail wants to remain outside the radius of the turn, and a "skid"
results. Its similar to the rear end of an automobile wanting to skid outside the turning radius of a car.
Therefore, a principle use of the rudder is to control the adverse yaw while rolling into a bank.
Slips
A slip is created by applying rudder in the opposite direction to the turn. This is called Cross
Controlling. There are 2 forms of the slip.
l Side Slip
l Forward Slip
Side Slip
This manuever is primarially used to compensate for a cross wind while landing. If the wind is from the
right of the aircraft, the aircraft will drift to the left side of the runway unless some force is applied in the
opposite direction keep the aircraft straight with and on the centerline of the runway. The pilot uses a
Right Side Slip to compensate for the leftward drift caused by the wind. The pilot turns the control wheel
to the right to initiate a right turn, but simultaneously applies opposite Left rudder just enough to keep the
aircraft from turning. Thus the pilot induces just enough right side slip to offset the leftward wind drift.
This way, the pilot can keep the aircraft both over the centerline of the runway, and aligned with the
runway. This prevents a "side load" on the landing gear on touchdown.
Forward Slip
The forward slip is used primarially on aircraft with no flaps. This configuration is used to loose altitude
quickly without increasing airspeed.
In this manuever, the pilot simultaneously turns the aircraft left or right, and applies a lot of opposite
rudder so the side of the aircraft is presented to the relative wind. It is almost like slipping a sled down a
hill somewhat sideways. The pilot maintains this configuration until the desired altitude is lost,
whereupon he neutralizes controls to continue straight flight.
Since most modern aircraft have effective flaps to slow the aircraft on landing, and to allow a steeper
decent, the forward slip in usually unnecessary. Some aircraft manufacturers state that forward slips
should not be made with flaps deployed.
Stalls and Spins
The angle of attack which produces maximum lift is a function of the wing design, and is called the
CRITICAL ANGLE OF ATTACK. A stall occurs when the Critical Angle of Attack is exceeded.
Smooth air flow across the upper surface of the wing begins to separate and turbulence is created along
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the wing surface. Lift is lost and the wing quits “flying”. THE STALL IS A FUNCTION OF
EXCEEDING THE CRITICAL ANGLE OF ATTACK, AND CAN OCCUR AT ANY AIRSPEED ,
ANY ATTITUDE, AND ANY POWER SETTING.
On most aircraft, the stall starts at the wing root, and progresses outward to the wing-tip. The wings are
designed in this manner so that the ailerons are the last wing elements to loose lift. Flap and gear
extension affect the stall characteristics. In general, flap extension creates more lift, thus lowering the
airspeed at which the aircraft stalls.
Recovery from a stall requires that the angle of attack be DECREASED to again achieve adequate lift.
This means that the back pressure on the elevators must be reduced. If one wing has stalled more than the
other, the first priority is to recover from the stall, then correct any turning that may have developed.
A CG that is too far rearward can significantly affect the ease of stall recovery. The aft CG may inhibit
the natural tendency of the nose to fall during the stall. It may be necessary to force a “nose down”
attitude to recover.
Although weight does not have a direct bearing on the stall, an overloaded aircraft will have to be flown
at an unusually higher angle of attack to generate sufficient lift for level flight. Therefore the closer
proximity to the critical angle of attack can make an inadvertent stall due to pilot inattention more likely.
Snow, ice or frost on the wings can drastically affect lift of the wing. Even a small accumulation can
significantly inhibit lift and increase drag. Due to the reduced lift, the aircraft can stall at a higher-thannormal airspeed. Takeoff with ice, snow or frost on the wings should never be attempted.
Stall recognition can come several ways. Modern aircraft are equipped with stall warning devices
(usually an audible signal) to warn of proximity to the critical angle of attack. The aircraft may vibrate,
control pressures are probably "mushy", the "seat of the pants" sensation that the aircraft is on the verge
of loosing lift, and other sensations can tip off the pilot of an impending stall. Practice of slow flight and
stalls at altitude is invaluable training in stall recognition.
A spin is a stall that has continued, with one wing more stalled than the other. The aircraft will begin
rotation around the more stalled wing. The spin may become progressively faster and tighter until the
stalled condition is "broken" (stopped).
Usually spin recovery procedures are covered in the Pilot Operating Handbook (POH) for the given type
of aircraft. If one is not available, the following is the suggested spin recovery technique.
a. Close the throttle. Power usually aggravate the spin. b. Stop the rotation by applying opposite rudder.
c. Break the stall with positive forward elevator pressure. d. Neutralize the rudder when rotation has
stopped. e. Return to level flight.
Secondary Controls
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Trim
There are some secondary "pilot-controlled" functions which can "trim" the elevators, rudder and
ailerons for improved straight and level flight, thus freeing the pilot from constant attention and control
of the major control surfaces. Most small aircraft have only Elevator Trim. As the sophistication of an
aircraft design increases, Rudder Trim and Aileron Trim are added. In most cases, the elevator trim is an
additional moveable surface on one of the elevator assemblies which causes a “nose up”, “level”, or
“nose Down” trimmed attitude.
In some aircraft, rudder trim and aileron trim can also be accomplished by pilot from the cockpit.. The
purpose of the trim action is to compensate for variations in aircraft loading or other minor factors which
may tend to cause deviation from straight and level flight.
Flaps
Flaps are moveable surfaces on the trailing edge of the wing similar in shape to the ailerons. they are
usually larger in surface area. They are located on inboard end if the wing next to the fuselage. Both
sides are activated together so they do not produce a rolling action like the ailerons.
Flaps are usually deployed in "degree" increments. In small aircraft deployment is usually in 10 degree
increments from zero degrees (non-deployed) to 40 degrees maximum. Larger or more sophisticated
aircraft may have a different range of settings. Normally, the flaps operate electrically through a 4 or 5
position switch located on the instrument panel. In earlier aircraft the flaps were operated using a manual
flap handle.
Deployment of flaps increases both the lift and drag of the wing. Flap activation increases the angle of
attack across the wing / flap section. At 10 degrees, more lift than drag is produced. As the flap angle is
increased more drag and less lift is produced for each increment of deployment.
The primary use of flaps is in landing. They permit a steeper decent without increase in airspeed. Flaps
may be used in certain take-off situations(usually 10°) on short or soft fields.
Dynamics of Flight
Drag
Just as wind friction causes drag in an automobile, aerodynamic friction and displacement of air during
flight creates aerodynamic DRAG. Drag occurs any time that air is displaced from its normal stable
condition. Air has density and weight, and although compressible, it still requires energy to displace.
l INDUCED DRAG occurs as a by-product of lift.
l PARASITE DRAG results from friction with surfaces and appendages, and impact with structures
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such as struts, landing gear, antennas, etc..
Induced Drag
Induced drag results from the creation of lift. The amount of drag depends on the airfoil design of the
wing, its camber and angle of attack. Also due to the way the air flows across the wing during flight,
vortices are generated at the wing tips which add to the induced drag component. .
Parasite Drag
Parasite drag is an unwanted resistance of the air to an object traveling through e air. The 3 types of
parasite drag are Form, Skin and Interference as demonstrated below.
Form Drag
The form of the
object and the
effective frontal
surface it
presents to the
air has a
significant effect on the amount of drag generated. As shown in (A), a surface such as shown would
present much more "frontal" drag than it would is it were rotated 90 degrees as in (B). Drag can be
reduced in the aircraft design by streamlining objects such as wing struts to minimize the frontal
appearance to the air flow.
Skin Friction
Even though the form in (A) above is re-oriented to shape (B), there is still some form drag. In addition,
there is friction between the skin of the surface and the air flow. It is obvious that if the surface is dirty,
has frost, ice or other obstructions, that drag will increase. Effects of skin drag can be reduced by smooth
surfaces and flush riveting in the design, and by keeping the surface clean and waxed by the owner.
Interference Drag
Surfaces at angles to each other as in (C) create turbulence in the region of the joint. This occurs most
frequently at the intersection of the fuselage and wing
Pitch, Power and Performance
The amount of lift that a wing generates is a function of it's design (camber, area, etc.), speed through the
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air, air density, and angle of attack. The effects of air density will be treated in more detail in a later
chapter.
The three aircraft
shown above can
all be in constant
altitude flight, but
at different
airspeeds. Maintaining a fixed altitude at a given airspeed requires the pilot to control two factors; (1)
Angle of Attack and (2) Power. The angle of attack is controlled by the up, neutral, or downward trim
position of the elevators. The power, is controlled by the "power setting" of the engine and propeller. For
a "fixed pitch" propeller, this means adjusting the engine RPM. For a variable pitch propeller, this means
adjusting both the throttle and the propeller pitch control.
The left aircraft could be at a 10 degree nose-up attitude with an indicated airspeed of say 70 nautical
miles per hour (knots). The center aircraft could be at cruise with a 0 degree attitude and 110 knots. The
right aircraft could be in a slightly high speed decent at minus 3 degrees of pitch and an indicated
airspeed of 140 knots (abbreviated kts).
The pilot can control the Pitch, Power and Performance of the aircraft and can fly at a considerable range
of attitudes, speeds and power settings.
Lift versus Drag
An aircraft with a given total gross weight can be operated in level flight over a range of power settings
and airspeeds. Since Lift and Weight must be equal in order to maintain level flight, it is obvious that
there is a relationship between Lift (L), Airspeed (V), and Angle of Attack (AT). This relationship can be
"generalized" with the following expression. (Note: the expression is not an exact equation).
Lift = Angle of Attack x Velocity
Since angle of attack and speed also have a relationship to Induced Drag and Parasite Drag, the
relationship of Lift/Drag is shown by the graph below.
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Parasite drag increases with
speed. Induced drag decreases
with speed. The SUM of the
two drags (Total Drag curve)
shows that there is only one
airspeed for a given airplane
and load that provides
MINIMUM total drag. This is
the point M which is the
maximum lift over drag ratio
(L/D). It is the airspeed at which
the aircraft can glide the farthest
without power (maximum glide
range). This is the airspeed
which should immediately be
set up in the event of a power
failure. This maximum glide
airspeed is different for each
aircraft design. The Pilot
Operating Handbook should be
consulted for this airspeed and the pilot should memorize it to eliminate need to search manuals during
an emergency.
Ground Effect
An aircraft can be flown near the ground or water at a slightly slower airspeed than at altitude. This is
known as Ground Effect.
The airflow
around the left
aircraft at
altitude can
flow around the
surface of the
aircraft in a
normal manner. The airflow around thr right aircraft is disturbed by the proximity to the ground. The
normal downwash of air produced by the wing and tail surfaces cannot occur, and the air becomes
compressed under these surfaces. A "cushioning" effect occurs which allows the airplane to fly at slightly
slower airspeed than at altitude.
The maximum ground effect occurs at approximately 1/2 the wingspan above the ground. It is this effect
which causes the plane to seem to float when near the ground on landing. It also allows the aircraft to be
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"pulled" off the ground before adequate climb speed is achieved.
Load Factor
The load factor is the total load supported by the wings divided by the total weight of the airplane. In
straight and level flight, the load factor is 1; i.e. the weight supported by the wings is equal to the weight
of the loaded aircraft. The load factor is described as 1G Force. With a load factor of 1, the G force is 1.
In other terms, the load supported by the wings equals the total weight of the loaded aircraft.
In a turn, the weight of the aircraft increases due to the addition of centrifugal force. The rate of turn
determines the total weight increase. A faster turn (steeper bank) generates greater centrifugal force. The
centrifrugal force is straight out from the center of the turn. When the downward weight of the aircraft is
mathematically resolved with the horizontal centrifrugal force, the load on the wings is the Resultant
Load.
In a
45
degree banked turn, the resultant load factor is approximately 1.4 G. In other words, the load on the
wings is 1.4 times the loaded weight of the aircraft. In a 60 degree banked turn, the load factor is 2G. The
load on the wings is TWICE the loaded weight of the aircraft. The G force is greater than 1 in a loop
maneuver for the same reason; i.e. a centrifugal force adds to the airplane’s weight. An abrupt change
from level to nose down creates an upward centrifugal force, decreasing the G load to less than 1G.
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Aerodynamics
The effects of the bank angle is shown in the graph on the right. The G
Force is shown on the Left Side, and the Bank Angle is shown on the
bottom of the graph.
The maneuver of most importance to the private pilot is the forces in a
turn. The most critical time is in tu rns in the traffic patern, when
airspeeds are low, and the attention to bank angle and airspeed may be
distracted by other duties.
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Pitot and Static System
Pitot and Static System
The Pressure System
The pitot-static pressure system provides the source of air pressure for the
l ALTIMETER (ALT)
l VERTICAL SPEED INDICATOR (VSI)
l AIRSPEED INDICATOR (ASI)
>
The two parts of the system are
(1) the pitot tube and pressure line
(2) the static pressure system and lines.
The pitot tube is normally mounted on the leading edge of a wing. The pitot tube on an aircraft used
only for flight under Visual Flight Rules (VFR) may not be heated to prevent icing. Aircraft to be used
under Instrument Flight Rules (IFR) are heated electrically, to prevent icing when operating in visible
moisture and cold temperatures. A switch in the cockpit controls Pitot heat.
The static pressure port is normally found on the side of the fuselage. On later model aircraft, an
alternate static source is provided inside the cockpit. The pilot can select the internal static source if the
outside source becomes clogged with ice.. When the pilot selects the alternative source, the instruments
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relying on the static pressure may operate slightly differently.
1. The altimeter (ALT) may indicate a higher-than-actual altitude.
2. The vertical speed indicator (VSI) will momentarily indicate a climb, then will settle back the initial
indication.
3. The Airspeed Iindicator (ASI) will indicate greater-than-normal airspeed. Altimeter (ALT)
THE ALTIMETER
The Altimeter (ALT) allows the pilot to determine the height above Mean Sea Level (MSL). Correct
altitude indication is very important for several reasons.
a) The pilot must be sure the aircraft is being flown high enough to clear terrain and other obstacles.
b) The pilot must maintain altitude according to certain air traffic rules and instructions to minimize the
possibility of mid-air collision.
c) The pilot can often select more favorable winds at certain altitudes.
d) True Airspeed calculation requires that the altitude be known.
The Altimeter measures the pressure of the outside air. A small bellows inside the altimeter which
contains a constant pressure inside expands when the aircraft climbs, and contracts when the aircraft
decends. This bellows is connected to a gear arrangement which causes the hands to turn as the bellows
expands or contracts. The altimeter is essentially a barometer which is measuring the outside air pressure,
but the indications on the dial indicate hundreds and thousands of feet.
Most altimeters have either 2 or 3 pointers. If 2 pointers, the longer one indicates hundreds of feet, and
the shorter pointer indicates thousands of feet. A third very short pointer which indicates ten's of
thousands altitude exist on some altimeters. The indication in the diagram shown below is 1,430 feet.
Altimeter Setting.
The altimeter is an aneroid barometer. It is correct only when in a known atmosphere. An International
Standard Atmosphere has been defined as a barometric Sea Level pressure of 29.92 inches of Mercury
(Hg), and a temperature of 15 degrees Celsius.
Effects of Atmospheric Pressure Changes
Whenever the altimeter is in a non-standard temperature and pressure the altimeter reads incorrectly, and
an adjustment means must be provided to compensate for the non-standard conditions. Atmospheric
pressure change has the greatest effect on the instrument.
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On modern altimeters, an adjusting knob and scale is provided to allow adjustment for non-standard
pressure. In the diagram of the altimeter face above, a window on the right of the instrument shows a
graduated barometric scale, called the altimeter setting. The pilot can adjust the altimeter setting with the
knob on the lower left. The setting shown is 30.00. If the altimeter is not periodically readjusted to the local barometric pressure, the plane will be too high if
the local sea level pressure pressure is higher than 29.92 and will be too low if the local sea level
pressure is less than 29.92 in. Hg.
As one flies cross country, the altimeter should be adjusted every 100 miles or so. If flying from a low to
a higher pressure area, the aircraft will be higher than indicated if appropriate altimeter adjustment is not
made periodically. For example, if the altimeter indicates 5000 feet, it will actually be above 5000 feet
when in the higher pressure area.
Likewise, when flying from a high pressure area to a lower pressure area, the aircraft will be falsely low
if no adjustment is made. If the altimeter is indicating 5000 feet, the aircraft will be below 5000 feet
when in the lower pressure area..
The altimeter setting can be obtained in flight from any Air Traffic Control facility or from any FAA
Flight Service Station. If taking off from an airport where no contact can be made with such a facility, set
the altimeter to the altitude of the airport prior to takeoff.
When flying at or above 18,000 feet (Flight Level 180) the altimeter must be set to 29.92. These altitudes
are primarially used by fast jet aircraft. Since there is no possibility of ground collision, all aircraft
operate with the same altimeter setting.
Effects of Temperature
Temperature affects the indicated altitude. The effect is not as drastic as pressure changes. Altimeters in
small aircraft have no simple means to compensate for non-standard temperature. The effect is similar to
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high and low pressure changes. When going from low temperature to higher temperature, the aircraft will
be higher than the indicated altitude. When going from high temperature to low, the aircraft will be lower
than indicated on the altimeter. The pilot should keep this in mind if terrain clearance is a factor in the
flight.
MEMORY AID: From high to low (pressure or temperature) LOOK OUT BELOW.
When flying over mountainous terrain, atmospheric conditions can cause the altimeter to indicate
erroneous altitude by as much as 1,000 feet. Therefore, a generous margin of safety should be planned
when flying over mountainous terrain..
Vertical Speed Indicator (VSI)
The mechanism of the VSI is similar to the altimeter except the bellows contains a small calibrated hole
that allows the pressure inside the bellows to slowly adjust to the same pressure as in the case. Therefore
the pressure inside the bellows is similar to what it was a few seconds ago.
If the change in pressure is slow, the up or down reading will be small. If the up or down altitude change
is large over a short time, the rate of climb or decent will be large. If the pressure both inside and outside
the bellows stays the same, the VSI will indicate zero.
The single pointer indicates level flight (indicating 0), climb in feet per minute ( pointer deflected
upward), and decent in feet per minute (pointer deflected downward).
In small piston engine powered aircraft, the rate of climb will usually be less that 1000 feet per minute.
Usual rate of decent enroute or approach to landing will be in the 500 feet per minute range. When flying
straight and level, the instrument should indicate zero. Also when sitting stable on the ground the
instrument should indicate zero. Most instruments are equipped with a small adjusting screw to calibrate
the zero position when the aircraft is at rest on the ground.
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Airspeed Indicator (ASI)
The Airspeed Indicator (ASI) measures the speed of the aircraft through the air. This should not be
confused with groundspeed. Winds can affect how fast the aircraft tracks over the ground. Groundspeed
is seldom the same as airspeed.
Principle of Operation
"Impact" air hiting the opening of the pitot tube which is pointing in the direction of travel creates a
pressure in the pitot tube line. This pressure is connected by a small tube to the inside of a bellows in the
ASI instrument. The outside atmospheric static pressure enters the case from the static line. The
mechanism inside the ASI therefore measures the difference between the pitot pressure and the static
pressure. Since the impact pressure of the pitot tube is proportional to the speed through the air, the speed
through the air is indicated by the instrument.
Indicated Airspeed (IAS)
The color coding of the airspeed indicator has meaning. The color arcs are as follows.
White Arc - Stall Speeds and Flap operating Range
----- -- Lower end of arc is the Power Off Stall speed with flaps and landing gear in the landing position.
----- -- Upper end of arc is the maximum flaps extend speed.
Green Arc - Normal operating airspeed range
------- Lower end of arc is the power off stall speed clean (flaps and gear up)
------- Upper end of arc is maximum structural cruise speed. (Max normal operating speed).
Yellow Arc - Caution range. Avoid this area unless in smooth air.
Red Line - Never exceed speed.
-------This is the maximum speed at which the aircraft can operate safely. ------- It should never be
intentionally exceeded.
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Calibrated Airspeed (CAS)
Although aircraft designers attempt to keep airspeed errors to a minimum, it is not possible to achieve
complete accuracy throughout the complete range of the instrument. Two types of errors can be
introduced.
a. Installation error caused by the static ports sensing erroneous pressure. This is due to the
unpredictability of the effects of the slipstream around the aircraft at various speeds and attitudes.
b. The pitot tube does not always present the same frontal appearance to the atmosphere at varying
attitudes.
The pilot should consult the Pilot Operating Handbook (POH) for the table applicable to the aircraft
being flown.
True Airspeed (TAS)
As altitude increases , air density decreases. The impact pressure at the port of the pitot tube is less at
higher altitudes. The airplane is actually traveling through the air faster than indicated on the ASI.
Consequently as altitude increase, Indicated Airspeed decreases.
A mathematical correction factor must be applied to Indicated Airspeed (or Calibrated Airspeed) to
arrive at a correct True Airspeed (TAS). This calculation can be made with he E6B Flight computer, or
an approximate correction can be made by adding 2 percent per 1,000 feet of altitude to the IAS.
EXAMPLE: Given IAS is 140kt and ALT is 6,000 feet. Find TAS.
2% x 6 = 12% (.12)
140 x 0.12 = 16.8
140 + 16.8 = 156.8 kt. (TAS)
Some airspeed indicators have built-in adjustment scales that allows the pilot to adjust the instrument for
temperature and pressure. Both the IAS and TAS can be read from such an airspeed indicator.
V Speeds
The Pilot Operating Handbook normally lists various airspeeds for differing situations and conditions.
The definition of the usual V speeds is shown below. is an abbreviation for Velocity.
VA. ..... design maneuvering speed
VFE.... Maximum flap extend speed
VLE.... maximum landing gear extend speed
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VLO....maximum landing gear operating speed
VNE....never exceed speed
VNO...maximum structural cruising speed
VR......rotation speed
VS0.... the power-off stalling speed or minimum flight speed in landing configuration
VS1.... the power-off stalling speed (clean) with flaps and landing gear retracted.
VX...... best angle of climb speed
VY......best rate of climb speed
Best Glide Speed
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GYROSCOPIC INSTRUMENTS
Gyroscopic Instruments
Gyroscopic instruments may be driven either electrically or by vacuum. In most light aircraft the Turn
Coordinator (TC) is electrically driven. Usually the Heading Indicator (HI) and Attitude Indicator (AI)
are vacuum driven.
Gyroscopic Principles
Any spinning object possesses gyroscopic characteristics. The central mechanism of the gyroscope is a
wheel similar to a bycycle wheel. It's outer rim has a heavy mass. It rotates at high speed on very low
friction bearings. When it is rotating normally, it resists changes in direction.
The gyroscope exhibits two predominant characteristics.
Rigity in Space
Precession
Rigidity in Space.
The gyroscope resists turning. When it is "gimbaled" ( free to move in a given direction) such that it is
free to move either in 1, 2 or 3 dimensions, any surface such as an instrument dial attached to the gyro
assembly will remain rigid in space even though the case of the gyro turns. The Attitude Indicator (AI)
and the Heading Indicator (HI ) use this property of rigidity in space for their operation. The HI
responds only to change of heading. The AI responds to both changes in Pitch and in Roll.
Precession
Precession is the deflection of a spinning wheel 90 ° to the plane of rotation when a deflective force is
applied at the rim. If a force is applied the top of the rim (the plane of rotation), the precession (turn) will
be 90° in the horizontal plane to the left. The Turn Coordinator (TC) uses this precession property. For
example, then taxiing on the ground, the Turn Coordinator will move, with the small airplane in the
instrument showing a bank, even though the aircraft is level. The banking of the small aircraft
presentation indicates only that the aircraft is turning.
The Vacuum System
The Attitude Indicator (AI) and the Heading Indicator (HI) n light aircraft are usually driven by a
vacuum system. The principal components are shown below. Not shown are auxillary devices such as
valves, filters etc. A pump provides the vacuum to the AI and HI through a system of vacuum lines. A
Vacuum Gauge is attached to the lines which gives the pilot an indication that adequate vacuum is being
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generated.
Heading Indicator (HI)
The Heading Indicator (HI) uses the principle of Rigidity In Space for it’s operation. The Gyro is
mounted such that it registers changes around the vertical axis only; i.e. direction changes. The compass
card attached to the gyro appears to the pilot as though it is turning. In reality, it and the attached gyro are
remaining rigid in space, while the aircraft and case turn about the gyro.
The HI is not automatically synchronized with the magnetic compass. It must be set to the compass
heading while level on the airport surface prior to take-off.
The HI gyroscope may precess in small amounts over time. Therefore, the HI should be checked against
the compass in 15 minute intervals. The check should be done only while flying in straight, level and unaccelerated flight. If adjustment is required, the heading can be reset using the adjustment knob shown.
The compass card has letters for the cardinal headings N, E, S, and W. Each numbered interval is every
30 degrees. The graduations are further divided by the longer marks every 10 degrees, and intervening
short marks at the 5 degree points.
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A significant advantage of the HI over the magnetic compass is its steadiness in turbulence and various
aircraft movements. As will be discussed later in the section on the magnetic compass, the compass can
have several errors introduced during turns, acceleration and deceleration. The HI is unaffected by these
maneuvers and by turbulence, and is a reliable instrument as long as the precession re-adjustment in
made in timely fashion.
Some makes of HI’s may "tumble" , loosing their gyroscopic characteristics, if subjected to more than 55
degrees of pitch or bank. In this condition, the heading card spins rapidly, and cannot be used for
navigation until reset by the adjustment knob.
Attitude Indicator (AI)
The Attitude Indicator shows rotation about both the longitudinal axis to indicate the degree of bank, and
about the lateral axis to indicate pitch (nose up, level or nose down). It utilizes the rigidity characteristic
of the gyro. It is gimbaled to permit rotation about the lateral axis indicating pitch attitude, and about the
longitudinal axis to indicate roll attitude.
The principal parts of interest to the pilot are:
· The miniature wings attached to the case remain parallel to the wings of the aircraft.
· The horizon bar which separates the top (light) and bottom (dark) halves of the ball
· The degree marks on the upper periphery of the dial. The first 3 on both sides of center are 10 degrees
apart, then 60 degree bank marks, and 90 degree bank arks. Fifteen degrees of bank is called a standard
rate turn.
The adjustment knob is used to adjust the wings up or down to align with the horizon bar. This allows
adjustment to the height of the pilot. Preferably, the adjustment should be made when level on the
ground.
When the wings are aligned with the horizon bar, the aircraft is in level flight. If the wings are above the
horizon bar, the aircraft is in a climb. Wings below the horizon bar indicates a decent. The upper blue
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part of the ball represents the sky. The miniture airplane wings (fixed to the case) represent the wings of
the aircraft. In the past, the instrument has been refered to as "an artificial horizon". When in a left turn,
the blue portion of the ball will have rolled to the right, as tho you were looking at the horizon over the
nose of the aircraft. In a right turn, the blue portion will have rolled to the left.
Turn and Slip Indicator
The instrument is comprised of two components.
· The turn needle is an electrically driven gyroscope which indicates the rate of turn. The marks (often
called the doghouse) on either side of center represents a bank angle of 15 degrees. This is termed a
Standard Rate Turn. The rate of turn is 3 degrees per second. It takes 2 minutes to turn 360 degrees.
· The glass level containing the black ball is called the Inclinometer. It provides the pilot with a measure
of the Turn Quality. During both straight and level flight and during turns the ball should stay centered.
The Turn and Slip Indicator acts as a partial backup to the Attitude Indicator in that it shows rate of
turn. This type of instrument is usually found in older aircraft.
Turn Coordinator
The Turn Coordinator is similar to the Turn and Slip indicator. It is found in more modern aircraft. The
main difference is in the presentation of the turn. A miniature airplane is used to show the bank instead of
a needle.
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There are 2 marks on each side. The upper ones indicate level flight when the wing align with them. The
lower marks indicates a bank angle of 15 degrees, which produces a standard rate turn. When the aircraft
turns right, the minature aircraft in the instrument indicated a right bank. When turning left, it indicates a
left bank.
Turn Quality
The inclinometer in both the Turn and Slip Indicator and the Turn Coordinator measures the turn quality.
As mentioned previously, when in a turn, part of the lift of the wing goes into "turning" the aircraft. This
is called the Horizontal Component of Lift (HCL). This HCL is directed toward the center of the turn.
Also, a force directed outward and away from the center of the turn exists. This is called Centrifugal
Force (CF). For the turn to be coordinated these two opposing forces must be equal. When they are
equal, the ball in the inclinometer will remain in the middle.
When too much rudder is applied, a skid results. The Centrifrugal Force is bigger than the Horizontal
Component of Lift (HCL). This makes the ball go toward the outside of the inclinomenter (i.e. the ball in
NOT in the middle).
When insufficient rudder is applied, a slip results. The Horizontal Component of Lift (HCL) is larger
than the Centrifrugal Force (CF). The ball rolls toward the lower side( or inside) on the inclinometer.
The term step on the ball is often used as a memory aid in overcoming a slip or skid. In actuality, more
rudder pressure (or less bank) must be applied in a slip. Less rudder pressure (or more bank) must be
applied in a skid. In both cases correction must be made so that HCL = CF to keep the ball centered.
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Magnetic Compass
Magnetic Compass
The magnetic compass is the only instrument in the aircraft by which the pilot determines the direction of flight.
Magnets in the compass cause it to align with the Magnetic North Pole.
The compass card has the four cardinal headings shown as N, E, S, and W. Numbers appear every 30 degrees.
Long vertical marks occur in 10 degree increments, with intervening short marks at 5 degree points.
The compass card containing the magnets are mounted on a small pivot point in the center of the card assembly.
This allows the compass card to rotate and float freely. It is somewhat like suspending a paper cup, upside down,
on a pencil point located at the center of the cup bottom. The enclosure is filled with white kerosene to provide a
medium to dampen out some vibration and unwanted oscillations. A "lubber line" in etched on the glass face of
the instrument to enable exact reading of the compass.
Magnets in the compass align themselves along a Magnetic North-South orientation. Whenever the aircraft is
headed toward magnetic North, the compass will indicate N. If the aircraft turns from this direction, the magnets
in the compass still align to this N-S direction. Similar to a gyro, the case of the compass and the lubber line is
fixed to the aircraft. Thus when the airplane turns, the the case turns about the compass card. The lubber line will
then show a reading other than North.
Compass Errors
Magnetic lines of force surround the Earth, flowing from the North to South Magnetic poles. The magnetic field
strength is greatest near the magnetic poles and weakest at the Equator. Several compass errors can occur.
These are:
1. Magnetic Variation
2. Compass Deviation
3. Magnetic dip
4. Compass Card oscillation
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Magnetic Variation
The Magnetic North Pole and the True North Pole are not at the same location on the surface of the earth.
Magnetic Variation at any given location on the earth’s surface is the difference between the Compass North and
True North. The map below shows the magnetic variation at various locations in the US.
The Agonic Line is the line of zero degree variation. It proceeds from upper Michigan through central South
Carolina. Variation values to the East of the agonic line are called Westerly Variation; i.e. the magnetic north
pole is West of True North. Likewise, the variation values west of the agonic line are known as Easterly
Variation; i.e. the Magnetic North Pole is East of True North.
Magnetic North changes in small amounts each year. Aeronautical charts are updated periodically to correct for
this yearly change.
When plotting a course on an aeronautical chart, the degrees of heading are measured against latitude and
longitude lines. This is called a True Course (TC) because it is being measured relative to the True North Pole.
Since the pilot relies on the magnetic compass for direction, the pilot will be steering the aircraft relative to the
Magnetic North Pole. Therefore, the pilot must convert the True Course (TC), as plotted on the navigation chart,
to a Magnetic Course (MC) by which to steer using the compass. . To convert from TC to MC, Westerly
Variations must be ADDED to TC to get MC (see right hand example below). MC = TC + VAR. (MC = 45° +
10° = 55°). In other words, the pilot must steer 55° magnetic to fly over a true course of 45°. Likewise, Easterly
Variation must be SUBTRACTED from TC to get MC (see left hand example below).
Compass Deviation
Magnetic deviation is the difference between the compass indications when installed in the aircraft compared to
the indications when the compass is outside the aircraft. The cause of this difference is that the compass magnets
can be influenced by magnetic fields within the aircraft due to electronic equipment and other factors. These
magnetic disturbances may cause the compass readings to be slightly in error. Such errors are called Compass
Deviation.. In other words, the compass reading when inside the aircraft "deviates" from a normal reading.
To determine compass deviation, the aircraft is parked on a compass rose painted on a level surface such as a
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ramp or taxiway. All of the electronic equipment is powered on as in normal operation. The nose of the aircraft is
placed on the Magnetic North marking on the ground. Deviation in the compass reading (from North) is recorded.
The aircraft is then rotated to 30 degrees to the right, and the deviation noted. The aircraft is turned in increments
of thirty degrees through the 360 degrees, and deviation from the proper reading is noted. This procedure is called
swinging the compass. These errors are posted on a Deviation Card placed at the lower portion of the compass.
For example, it may state for a course of 180, steer 178°.
Usually the errors are only a few degrees, but should be taken into consideration by the pilot then tracking a given
magnetic course.
Compass Dip Errors
Any time the compass card is not perfectly level, the magnets dip downward toward the earth. The result is that
the compass does not correctly align with Magnetic North the same as when the card is level. This results in
erroneous indication while in the non-level state. Dip occurs under 2 conditions.
1. During turns from the north and south. (i.e. Plane is in a bank.
2. During acceleration or deceleration while on an East or West heading.
Compass Turning Errors
When the aircraft initiates a right turn from the North, the dip of the compass causes the compass to initially
indicate a turn IN THE OPPOSITE DIRECTION (i.e. the compass turns left). The amount of initial error is
approximately equal to the Latitude position of the aircraft. If at a 30 degree latitude, and a right turn from North
is initiated, the compass card will initially turn LEFT to 330 degrees. As the right turn to the EAST proceeds,
the compass will start to catch up, so that when EAST (090) degrees is reached the compass will indicate
correctly, even though the aircraft is still banked.
If the turn is LEFT from NORTH, the compass will turn right to 030 degrees, and will catch up by the time
WEST (270) degrees is reached. THEREFORE, WHEN TURNING FROM NORTH, THE COMPASS LAGS. If turning to the North, you will
have to roll back to straight and level approximately 30 degrees prior to reaching North on the compass.
When turning from SOUTH, the opposite action occurs; the compass LEADS by the amount of the degrees
Latitude. If at 30 degrees Latitude, the lead will be approximately 30 degrees. If you are turning to the South, you
will have to roll back to straight and level approximately 30 degrees past South reading.
MEMORY AID: Turn to N, Under Shoot. Turn to South, Over Shoot.
Compass Acceleration Errors
When the aircraft is on an East or West heading, acceleration or deceleration of the aircraft causes the compass
card to tilt forward or backward, respectively. This tilting causes the compass card magnets to swing downward
toward the earth, which in turn causes the compass to rotate to an incorrect indication.
This error is maximum when on an East or West heading, and gradually diminishes to zero when a North or
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South heading is reached. Acceleration of the aircraft causes the compass to erroneously swing to the North.
Deceleration causes erroneous rotation toward the South
.
Again, the error is approximately equal to the Latitude degrees of the aircraft location. At 30 degrees Latitude,
acceleration causes the swing to a northerly reading to be approximately 30 degrees. Once the acceleration ceases,
and the aircraft assumes a constant forward velocity, the compass will return to it’s original East or West reading.
In like manner, deceleration of he aircraft causes an erroneous swing to a southerly reading of approximately 30
degrees at the same Latitude.. MEMORY AID: A N D S - Accelerate North, Decelerate South
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The Engine
Engine
Most light aircraft use a conventional 4 stroke engine. It operates similarly to an automobile engine.
There may be 4, 6, or 8 pistons in the engine. The four strokes are:
1. Intake
2. Compression
3. Power
4. Exhaust
· Intake Stroke - The piston goes downward during the intake stroke. A valve called the Intake Valve is
open, such that an air/fuel mixture enters the cylinder through the carburetor. During this operation a
second valve, the Exhaust Valve closed.
· Compression Stroke - During this stroke, the piston is forced upward by the crankshaft. Both the Intake
and Exhaust valves are closed. Consequently the air/fuel mixture in the closed cylinder is compressed by
the upward movementof the piston.
·
Power Stroke - As the piston nears the top of the cylinder, the spark plugs fire under control of the
magnetos. There are 2 spark plugs in each cylinder, with a separate magneto supplying the electrical
spark current to each plug. The spark ignites the fuel/air mixture, causing an explosion to occur in the
cylinder. This forces the cylinder downward, and imparts power to the crankshaft. While one cylinder is
performing the power stroke, other cylinders are in some phase of the other three strokes. Therefore the
power stroke is the only one contributing to propulsion of the aircraft.
·
Exhaust Stroke - When the piston reaches the bottom of the power stroke, the Exhaust Valve opens. The
piston is pushed upward by the crankshaft, causing the burned fuel / air mixture to be purged from the
cylinder. The exhaust valve closes, and the piston is now in a position for another intake stroke.
The pistons connect to the crankshaft through connecting rods. They attach the piston, which has an updown motion, to the crankshaft which turns in a rotary motion. The crankshaft is usually directly
connected to the propeller. In some aircraft, a gear arrangement connects the propeller to the crankshaft.
The crankshaft may also drive auxiliary devices such as the Magnetos, Vacuum Pumps, Alternator and
other devices. The connection may be directly or through lleys, belts and gears.
The ignition system is comprised of the magnetos and spark plugs, and is independent of the electrical
system. Even if the alternator and battery are inoperable, the ignition system continues to function. If
there is insufficient battery power to crank the engine, the engine can be started on most small aircraft by
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“hand propping”. This is a procedure wherein the propeller is turned swiftly by hand to get the magneto
system to fire, and start the engine. It is similar to pulling the starter cord on a lawn mower.
EXTREME CAUTION MUST BE EXERCISED WHEN HAND PROPPING AN ENGINE.
A meter within the cockpit called the Tachometer indicates the engine Revolutions per Minute (RPM).
Monitoring devices such as the Oil Pressure and Oil Temperature gauge in the cockpit may be attached
to the engine.
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The Engine
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Fuel System
Fuel System
Most modern aircraft are equipped with 2 or more fuel tanks (or cells). In high wing aircraft, the cells are
housed in the wings. Since they are higher than the engine, the fuel flows down to the engine by the force
of gravity. A typical high wing system is shown at right.
On low wing aircraft fuel pumps are required. To initially get fuel to the engine for starting, an electrical
“boost pump” is turned on to pump fuel to the engine. After the engine is started, a mechanical fuel pump
driven by the engine feeds fuel to the engine. The electric boost pump can now be turned off.
Each fuel tank is equipped with a drain valve located at the lowest point in the tank. This drain allows the
pilot during preflight walk-around to check for and drain off any water which may have accumulated in
the fuel tank. There is usually another drain located at the lowest part of the fuel piping system. This
valve must also be drained during pre-flight to eliminate any water which may have accumulated in the
fuel lines. Associated with this drain is a fuel strainer which filters out foreign matter which may be in
the fuel system.
A vent line allows air to enter the tank as fuel is used. During hot weather, fuel may expand and overflow
through the vent when tanks are full.
A fuel selector valve located inside the cockpit allows the pilot to select which tank(s) are to be in use
during flight. Most small aircraft operate with the selector set on Both, such that both the left and right
fuel tanks are simultaneous feeding fuel to the engine. The pilot may set the selector on Left or Right
tank as a means of equalizing the loading of the aircraft. Usually, the selector should be set to both for
take-off and landing. Pilots of low wing aircraft should exercise caution in their fuel management if tank
selection is other than both. Running a tank dry can cause the engine to quit and vapor lock to occur in
the fuel lines. It may be impossible to restart the engine under these conditions.
There is a fuel gauge in the cockpit for each fuel tank. The lower 1/4 of the fuel gauge indication is
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marked with a red line as a caution to the pilot of a low fuel condition. The pilot should never rely on the
fuel gauge as the sole measure of fuel remaining. The gauges on aircraft are subject to a variety of
indicator errors. The pilot should therefore double check the fuel remaining based on the power setting of
the engine in flight and time in flight.
Inside the cockpit a fuel mixture control and a fuel primer pump are located on the instrument panel. The
mixture control is used to adjust the air/fuel mixture for the altitude being flown. It allows the pilot to
adjust the fuel/air ratio entering the engine. As altitude is gained, the intake air becomes less dense. Less
fuel must be fed through the carburetor to permit the fuel/air mixture to remain correct proportion. If
leaning is not accomplished by the pilot, a rich mixture (too much fuel) results. This is not only wasteful
of fuel, but can result in fouled spark plugs due to carbon and soot buildup on the spark plugs. A rough
running engine results. An additional gauge called an Exhaust Gas Temperature Gauge can be installed
in the aircraft as an aid in achieving the proper “leaning” of the engine.
The fuel primer is a plunger that can be used in cold weather to inject fuel directly into the carburetor as
an assist in starting the engine in cold conditions.
Three different grades of fuel are used in reciprocating engine aircraft. These grades are designated by
octane rating and are color coded so the pilot can insure the proper grade of fuel is being pumped into the
tanks.
These grades are:
OCTANE RATING..........FUEL COLOR
· ..... 80/87........ ..... ..... .........Red
· .......100LL (low lead). ..... ....Blue
· ...... 100/130.... ..... ..............Green
When refueling, if the appropriate grade of fuel is not available, USE THE NEXT HIGHER GRADE.
Using a lower grade can cause overheating and damage to the engine. Sparks during refueling can be an
extreme fire hazard. The following precautions should be taken when refueling is in progress.
1. Attach a ground wire between the fuel pump or truck to a metal part of the aircraft. This will neutralize
any static charge which may exist between the pump and the aircraft.
2. The fuel nozzle should be grounded to the side of the fuel filler hole during refueling.
3. The fuel truck should be grounded to both the aircraft and the ground.
Do not use automotive fuel unless the engine has been specially modified for automotive fuel use.
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Fuel System
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Fuel System
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INDUCTION SYSTEM
Induction System
The engine receives ram air through an intake in the lower front portion of the engine cowling. An air
filter is placed at the intake end of the duct. This filter removes dirt, dust and foreign matter from
entering the carburetor. The air passes through an airbox, then to the carburetor intake. In the event that
the airflow to the carburetor becomes blocked by carburetor ice or intake ice, an alternate heated air
source can be selected by the pilot by pulling out a carburetor heat control in the cockpit. Use of the
heated air will result in approximately 75 to 100 RPM drop.
A throttle is located on the instrument panel in the cockpit. When the throttle is closed, it is pulled
rearward toward the pilot until it is stopped by mechanical means. At this setting, the engine continues to
run, but at “idle” speed (a few hundred RPM). As the throttle is moved forward, the throttle valve in the
carburetor opens allowing more air into the carburetor, thus increasing the RPM. When the throttle is full
forward maximum RPM results. The throttle can be locked into a set position with a friction lock so that
in cruise flight the power setting will remain set. This relieves the pilot from constant attention to the
throttle.
Carburetor
The carburetor provides 2 principal functions.
· It mixes the fuel with the air in the proper proportion
· It regulates the amount of air (and thus fuel) that enters the engine.
The the air is routed from the intake through ducts into the carburetor. The carburetor on most engines
are of the updraft type; i.e. the carburetor is mounted on the bottom of the engine, and the fuel/air
mixture is sucked upwardto the engine.
When the carbuerator heat control in the cockpit is pulled on, heated air enters the carbuerator. The air
source comes from inside the cowling, and passes through a “heat” box to warm the intake air. The
heated air can be selected when atmospheric conditions are conducive to carburetor icing or the normal
intake duct become blocked by ice at the induction port and air filter.
The carburetor is equipped with a small chamber containing fuel and a float valve. The valve maintains a
constant amount of fuel in the chamber. This provides a constant and sufficient source of fuel to satisfy
the fuel demands of the engine.
The main air duct of the carburetor is a tubular structure which decreases in diameter near the middle of
the duct, then increases in diameter near the intake manifold end of the carburetor. This is called the
“venturi”. This decreased diameter creates a vacuum in accordance to the Bernoulli principle. The fuel
intake port is located in this section. A metered amount of fuel is sucked into the carburetor. The fuel
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vaporizes into fine particles in the intake air flow. This atomized fuel and air mixture is of proper
proportion to cause correct burning of the fuel/air mixture in the engine.
The fuel / air mixture is set by design to be correct for operation at sea level. As the engine is operated
over a range of altitudes and air densities, the pilot can adjust the mixture via manual means in the
cockpit. It is called the “mixture control”. The correct mixture adjustment procedure is covered in the
Pilot Operating Handbook (POH) for the given aircraft. Some aircraft are equipped with an Exhaust Gas
Temperature Gauge in the cockpit. A proper fuel/air mixture will produce a given exhaust gas
temperature. The pilot can adjust the fuel / air mixture to a fairly accurate measurement by observing that
the exhaust gas temperature is within the proper range.
The throttle regulates the amount of fuel/air that enters the engine, thereby controlling the power that the
engine develops. On aircraft with a “fixed pitch” propeller, the throttle directly controls the engine RPM.
On aircraft with a variable pitch propeller, a Manifold Pressure Gauge directly measures the engine
power being developed. A propeller pitch control controls the propeller blade angle. The power setting of
the engine requires adjustment of both the throttle and propeller pitch control.
The carbuerator has an accelerator pump which will provide a “burst” of additional fuel for quick
development of maximum horsepower, such as performing a go around from landing approach. An
economizer valve allows the engine to idle when the throttle closed.
Icing
The predominate forms of icing affecting engine operation are carbuerator ice, throttle ice and induction
ice.
Carbuerator Icing
Carburetor icing is a constant concern to the pilot when operating in high
humidity and visible moisture conditions. Whenever the outside
temperature is 20° to 70° F, ice creation in the throat of the carburetor is a
possibility. Due to the Bernoulli effect and the vaporization of the fuel in
the venturi, the temperature of the fuel / air mixture can be as much as 50
degrees lower than the outside air.
Induction Icing
INDUCTION SYSTEM
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The air induction port at the front of the cowling can become partially or totally clogged with ice when
air temperatures are 32° F or below while flying in visible mousture. This is known as “impact” ice, and
is most prevalent when the Outside Air Temperature (OAT) in around 25° F and super-cooled moisture
exists.
Throttle Ice
Throttle ice in the carburetor occurs most often when the throttle is partially closed. This can occur at
low cruise speeds or near idle situations such as approach to landing. Some manufacturers recommend
that the alternate air source (carburetor heat on) be used anytime the power setting of the aircraft is below
a certain point even though high atmospheric moisture content is not present. For fixed pitch propeller
configurations, most aircraft should use carburetor heat below 2000 - 2100 RPM. The location of ice in
the carbuerator is shown in the diagram at right.
The vaporization of the fuel in the venturi additionally cools the throttle area. Even a small amount of ice
in the carburetor or the induction system will reduce power. Usually this condition is detected by a
gradual drop in RPM (or Manifold Pressure). Application of carburetor heat will usually cause an
additional temporary decrease in power, but as the ice melts, the power should be restored. If icing is
persistent, it may be necessary to operate with some carburetor heat on continuously.
Fuel Injection
In these systems, the air intake system is similar to carbuerated systems. However, the fuel is not
vaporized in a venturi, but rather is injected directly into the engine cylinder just prior to the spark plugs
firing. A specific amount of fuel is injected and an appropriate amount of air is vented though the air
induction system to provide for proper combustion.
There are several advantages to fuel injected systems.
· Less susceptibility to icing
· Fuel flow is better controlled
· Faster throttle response since the fuel is directly injected into the cylinder.
· Better distribution of fuel to each cylinder.
· Easier starting in cold weather.
Some disadvantages are:
· Starting a hot engine can sometimes be difficult.
· Vapor lock during ground operations on hot days.
· Difficult engine re-start if engine quit due to fuel starvation. INDUCTION SYSTEM
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INDUCTION SYSTEM
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Electrical System
Electrical System
Most small aircraft are equipped with a 28 volt direct current electrical system. The system is powered by
an Alternator which drives the electrical devices and stores energy in the battery.
A simplified diagram is shown at below. Not shown are the starter, and starter switch, and various other
electrical regulators and devices.
Electrical System
The Master Switch (labled MS) causes the electrical system to connect the electrical buses and devices to
the battery. The battery provides the power to crank the starter. Once the engine is running, power is
supplied by the alternator and the battery is recharged.
Numerous circuit breakers feed off the Primary Electrical Bus, and provide individual circuits to power
the electrical devices. Although the arrangement will vary from one make and model aircraft to another,
the basic principles are the same. By providing numerous circuit breakers and dividing the electrical load
into several different circuits, a malfunction in one system can be turned off without adversely affecting
the other circuits. The breakers will be labeled as to their general use, and the amperage will be marked
on the face of the breaker push button. On older model aircraft, fuses are used instead of circuit breakers.
Usually an alternator light is located on the instrument panel to provide a means for the pilot to determine
alternator is providing power to the system. In addition, an ammeter on the instrument panel can
determine the general health of the electrical system. After the battery is used for starting, a considerable
“charge” should be shown, indicating that the alternator is replenishing the power drained from the
battery during engine cranking. If the indicator shows zero while electronic equipment is ON, failure of
the alternator to charge the battery is indicated.
A second bus is provided to power the electronic and avionics equipment. This bus is connected to the
Primary Bus via the Avionics Switch. This switch should not be turned on until the engine is started to
prevent the possibility of high voltage transient currents resulting from engine starting from feeding into
sensitive electronic equipment. The pilot should also turn this switch OFF prior to engine shut-down for
the same reason.
Prior to start-up the pilot should check the status of all circuit breakers as a part of the pre-flight check. A
“tripped” breaker will project out farther from the control panel than does a properly functioning breaker.
Pushing the breaker in will reset it to it’s normal operating position. If it pops out again, there is a
malfunction in the circuit which it feeds, and repair should be made prior to flight.
The pilot should turn on the master switch during the walk-around pre-flight inspection to insure that the
rotating beacon and strobe lights (If present) are functioning. If all or part of the flight is to occur at
night, the navigation lights, instrument panel lights, taxi and landing lights should also be checked for
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proper operation.
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Electrical System
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Propulsion System
Propulsion System
The propeller is a rotating airfoil. It is subject to drag, stalls and other aerodynamic factors that apply to
any airfoil. The propeller provides the thrust to pull the aircraft through the air. As seen at right, the cross
section near the hub of the propeller is thick, and has a fairly large angle of attack. The angle of attack
and the thickness decreases toward the tip of the blade. Since the linear speed at the tip is much faster
than at the hub the change in angle of attack provides uniform thrust along the surface of the blade.
The propeller is normally connected directly to the engine crankshaft. Some aircraft , however, employ
gear arrangements between the engine and the propeller.
Propellers fall into two main categories.
· Fixed Pitch
· Controllable pitch
Controllable pitch propellers allow the pilot to set the pitch of the blades, either directly or via a
governor, to the best angle for the flight condition and performance desired. Usually for takeoff, a fairly
“flat” angle of attack and high engine RPN is used to produce maximum horsepower and thrust. As
altitude is gained the pilot can reduce RPM and increase pitch for a cruise climb condition. Once cruise
altitude is reached the throttle, mixture and propeller pitch can be adjusted for the desired cruise
performance.
The pilot has only one method of controlling thrust on fixed pitch propellers; that being adjusting engine
RPM. With controllable pitch propellers, the pilot can adjust two controls; these being RPM (throttle)
and Manifold Pressure (propeller pitch control). The Tachometer indicates RPM and the Manifold
Pressure Gauge indicates the manifold pressure.
On constant speed propellers, a governor automatically adjusts the pitch of the propeller blade whenever
the engine throttle setting is changed. Low RPM and High Manifold pressure should be avoided, as this
places undue stress on engine components, and can lead to eventual engine failure.
For any given blade angle, the propeller has an ideal geometric pitch. It is designed to travel a certain
distance in one revolution. However, due to slippage, the ideal geometric pitch is never attained.
Therefore the effective pitch is always less than the geometric pitch. The propeller is never 100%
efficient.
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Stall Warning System
Most aircraft are equipped with a Stall Warning system of some type. On some older aircraft, a small
moveable flap located on the leading edge of the wing engages an electrical switch in the cabin, which
activates a stall warning buzzer or horn. On some later aircraft, the system is pneumatic, with a small slot
in the leading edge of the wing. Both types sense approach to stall, and sounds a device in the cabin,
warning of impending stall.
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Weight and Balance
WEIGHT AND BALANCE
Overview
Weight affects the flight performance of an aircraft in many respects. An airplane which is overloaded
will be deficient in performance because:
Higher takeoff speed is required.
Longer take-off run.
Reduced rate of climb performance
Shorter range of flight
Reduced cruise speed
Reduced maneuverability
Higher stall speed
Higher landing speed
Longer landing roll
Balance Principles
As shown in the figure below, the aircraft is somewhat like a childs "teeter-totter" with respect to
longitudinal balance. For the plank to be in balance, The sum of the moment s on each side of the pivot
point (fulcrum) must be equal. A MOMENT is simply the weight multiplied by a moment arm
(distance) from some reference point. In this example, the moments are measured from the center
fulcrum point.
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As seen, the plank is in balance because the sum of the moments on each side equals 5000 pound inches.
If a weight on either side is moved, or a weight is changed, the plank will no longer be in balance.
An aircraft in flight is very similar. The pivot point (fulcrum) is the located at the Center of Lift of the
wing. The load on the left is the total weight of the aircraft located at the Center of Gravity (CG) with a
counter-balancing force on the right provided by the elevators.
Note that if the location of the CG or the weight on the left changes, the elevator force must also change
in order to maintain the balance. Also note, if the fulcrum (center of wing lift) changes, the elevator force
must be changed to maintain a balanced condition. Such an event can occur when the angle of attack
and/or engine thrust is changed.
The Center of Gravity
As previously stated, the weight of an aircraft and its load is distributed throughout the aircraft as shown
below by the small downward arrows. All of the small individual weights can be resolved into one single
weight acting at the Center of Gravity and shown as the large arrow..
Weight and Balance
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From the analogy of the plank above, we can see that if we change either the weight of the aircraft, or the
center of gravity, this in turn changes the force (either up or down) that the elevator must produce.
For each aircraft design, the manufacturer specifies a maximum weight for operation of the aircraft, and
also a maximum forward and rearward location of the Center of Gravity (CG). This is called the CG
RANGE. For safe operation, the aircraft must be operated within these parameters.
In order to calculate where the center of gravity is located, the manufacturer specifies some point in the
aircraft as a reference point (DATUM). In many Cessna 172 type aircraft, the datum is located at the
lower firewall of the cabin, just ahead of the rudder pedals. You as a pilot do not need to know where this
is located in order to calculate weight and balance, as the manufactirer provided moment arm and/or
Weight and Balance
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moment in the weight and balance tables for the aircraft. An aircraft mechanic must know where whis
point is, however, if equipment change is made to the aircraft which changes either the aircraft CG or
Empty Weight.
An airplane is designed and certified to withstand specified loading on it’s structure. As long as the gross
weight and load factor are within limits, the aircraft can be operated safely. Continued operaton of an
aircraft in an overloaded condition can cause structural failures. Metal fatigue is hastened, and can lead to
stress failures even in normal operating modes.
Effect on Wing Loading
The location of the CG affects the total load which the wings must sustain. If the CG is at or near the
Center of Lift of the wing the elevators do not have to generate much (if any) downward force. If the CG
is aft of the center of lift, the elevators must produce an upward force. If the aircraft is nose heavy
(forward CG) the load on the wing and elevator surfaces will be greater.
An aft CG location causes the airplane to require more "nose down" elevator for stall recovery. A
forward CG enhances stall recovery as the aircraft will naturally want to "nose down".
Definitions
MOMENT ARM -- a horizontal distance of an object measured from a defined “datum” point to the CG
of the object, usually measured in inches. A (+) arm means the object is behind the datum. A (-) arm
indicates the object is forward off the datum point.
MOMENT -- the product of a moment arm and the associated weight. (Weight x Arm)
EMPTY WEIGHT-- the combined weight of the aircraft, and permanently mounted equipment. It
includes unusable fuel and hydraulic fluid. Most manufactures include the oil in the empty weight.
Center of Gravity -- the point at which the airplane will be in balance.
CG Limits -- the most forward and most rearward CG points specified by the manufacturer for safe
control.
CG Range -- the distance from the most forward and rearward CG points as specified for the given
aircraft.
DATUM -- a point in the aircraft from which all moment arms are measured.
FUEL LOAD -- the weight of the useable fuel. It does not include unusable fuel in the tanks and lines.
GROSS WEIGHT-- Total weight of aircraft, fuel, passengers and baggage.
Weight and Balance
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MAX LANDING WEIGHT - Maximum gross weight allowed for landing.
MAX RAMP WEIGHT -- Maximum gross weight prior to taxi and take-off.
MAX TAKEOFF WEIGHT -- the maximum allowable weight at start of takeoff run
USEFUL LOAD -- Gross weight minus the empty aircraft weight.
STANDARD WEIGHTS -- Gasoline 6 lb. per gal; Oil 7.5 lb. per gal. (US Measure)
Methods of Determining Weight and Balance
The method of determining weight and balance may vary with aircraft manufacturer and type of aircraft. These methods are:
1. Center of Gravity Calculations
2. Center of Gravity Graphs
3. Center of Gravity Tables
4. Loading Schedules (Placards)
Center of Gravity Calculations
To determine the location CG, add up all the weights and all the moments. Divide the sum of the
moments by the sum of the weights. This is illustrated in the diagram.
All moments aft of the datum are positive numbers. All moments forward of the datum are negative. In
the example, the oil is the only negative moment since it is forward of the DATUM.. Calculate the
weight of oil at 7.5 pounds per gallon. Calculate fuel at 6 pounds (US) per gallon.
The procedure to calculate the CG is as follows:
1. Add up all weights, including empty aircraft
2. Multiply each weight by it’s moment arm in inches to get the moment for that item.
3. Add up all the moments
4. Divide the sum of the moments by the total weight to get the CG
A TYPICAL W/B PROBLEM
ITEM WEIGHT lbs MOMENT ARM in. MOMENT LB IN
Weight and Balance
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A = AIRCRAFT 1000 6 6000
P = PILOT 150 11 1650
B = BAGGAGE 40 32 1280
O = OIL 7.5 -4 -30
F = FUEL 120 16 1920
TOTAL 1317.5 CG? 10820
In the example, CG? = 10820/1317.5 = 8.21 in. aft of the datum.
Loading Graph
Frequently the manufacturer provides a graphical method for determining weight and balance.
Determine the load moment for each load item using the appropriate line in the graph. For example, for
pilot and front seat passenger, total the combined load weight. Go up the Load Weight axis (Y axis) to
the pilot & passenger weight. Then go horizontal to the pilot & passenger line (Red line). Then go down
to the X axis to find the load moment/1000. Do the same for fuel (blue line), rear passengers (green Line)
and baggage (black line). Total up the weight and the Load Moments.
EXAMPLE: Determine the Load and moment from the loading graph above for each of the following
load items.
Weight and Balance
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Weight and Balance Using
Loading Graphs
Weight and Balance
Weight **Moment
Empty Weight 1,364 51.7
Front Seats 400 15.0
Baggage 120 11.5
Fuel (38 gal) 228 11.0
Oil (2 gal) 15 - 0.2
TOTAL 2,127 89.0
Derive the values as follows:
1. Empty Weight and moment are values provided by the manufacturer.
2. Pilot & Passenger - Add weight for Pilot and Passenger. In this example 400lb. Go up the left side (Y
axis) of the graph to 400 lb. weight, then horizontal to the “Pilot & Passenger” line. Read vertically down
from the intersection to the horizontal (X) axis, and read a Moment/1000 value of 15.0.
3. Baggage - The baggage weight is 120 lb. Go up left side of the upper graph to a load of 120 lb.
Continue horizontally to intersect the “baggage” line. Go downward from this intersection and read a
Moment/1000 value of 11.5.
4. Fuel -- 38 gallons at 6 pounds per gallon is 228 pounds. Go up the left side of graph to a weight value
of 228 lbs., then horizontally to intersect the“fuel line. Go downward to read a Moment/1000 value of
11.0.
5. Oil was not included in the empty weight of this aircraft, therefore it must be entered into the
calculation. Two gallons of oil is 15 lb. The moment is -0.2 lb-in.
Loading Envelope
Once the total weight and the total moment/1000 is found, use the load and CG envelope to ascertain that
the aircraft is properly loaded.
Go up the left side to a total load of 2127 lbs. Draw a horizontal line. Go along the bottom scale to find
the loaded aircraft moment / 100 value of 89.0. Draw a vertical line. The aircraft is properly loaded if the
intersection of the horizontal and vertical lines is within the envelope.
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According to this envelope, if the weight is greater than 2300 pounds, the aircraft is overloaded. If the
intersection is outside the envelope laterally, the loading is out of proper CG range.
Center of Gravity Tables
Some manufacturers provide tables instead of graphs or calculation. This method is fairly lengthy, and is
used infrequently for small aircraft. Therefore this method will not be covered herein.
Weight Shift and Change
The approach to solving both Weight Change and Weight Shift is the same. The simplest method is to
REMOVE a changed item, and to ADD the new or shifted item into the new location.
Weight Change
Example 1:
An airplane takes off with a Gross Weight of 6230 lb., and a CG of 79.0. The CG of the fuel is at 87.00
aft of datum. What is the New CG location after 50 gallons of fuel is burned?
Procedure:
Subtract the Weight and Moment of the burned fuel from the initial values to arrive at a new set of
values. At 6 pounds per gallon, the burned fuel weight is 300 pounds.
WEIGHT CHANGE PROBLEM
Weight and Balance
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WEIGHT CG MOMENT
Initial Weight 6230 79.00 492,170
Burned Fuel -300 87.00 -26,100
New Weight 5930 New CG 466,070
NEW CG (after Fuel Burned) = 466,070 / 5930 = 78.59
Weight Shift
Example 2:
The gross weight of the aircraft is 3,000 lbs. with a CG of 60 in. Since takeoff, 25 gallons of fuel has
been used. The fuel cell CG is 65 in. aft of Datum (Station 65).
Also, a 200 pound passenger moves from Station 50 to Station 90. (Note: Some problems will state the
CG location as "Station". The 50 and 90 are CG location in inches aft of datum respectively).
Find New CG.
Procedure:
1. Subtract burned Fuel
2. Subtract Passenger who moves from the old location.
3. Add passenger who moves to the new location.
WEIGHT SHIFT PROBLEM
Weight CG Station Moment
Initial Loading 3000 60.00 180,000
Fuel Burned -150 65.00 9,750
Passenger Off -200 50.00 -10,000
Passenger On +200 90.00 +18,000
New Totals 2850 New CG 178,250
New Cg = 178,250 / 2850 = Station 62.54
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Aircraft Performance
Aircraft Performance
Factors Affecting Performance
Performance of the aircraft depends on the density of the air in which it flies.
Factors affecting air density are:
1. Barometric pressure
2. Altitude
3. Temperature
4. Humidity
Standard Atmosphere Definition
The International Standards Association (ISA) has defined a Standard Atmosphere as:
· Sea Level Barometric Pressure of 29.92 inches of Mercury (in. Hg)
· Sea Level Temperature of 15° Celsius (15° C or 59° F)
· Relative humidity of 0 %
· Standard temperature lapse rate of 2° C per 1000 feet altitude
· Standard pressure lapse rate of 1 in. Hg per 1000 feet altitude
· A standard decrease in density as altitude increases
The standard atmosphere definition provides a means for instrument and aircraft manufacturers to
specify the performance of their products in a uniform way. This definition was arrived at by studying
the average sea level pressure and temperature over a number of years, seasons, and locations around the
world.
Seldom will an aircraft be in standard atmosphere conditions. In order to define peformance of an
instrument or an aircraft in a non-standard atmosphere, conversions must be applied to adjust the
readings or performance numbers to agree with the standard atmosphere. This adjustment is called
Density Altitude, and will be more fully defined later in this chapter.
Effects of Non-standard Air Density
Air Density decreases:
· With Air Temperature Increase
· With Altitude Increase
· With Humidity Increase
· With Barometric Pressure Decrease
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With lower air density:
· The engine develops less power.
· The propeller produces less thrust.
· The wings produce less lift.
This results in:
· Longer takeoff run
· Poorer climb performance
· Longer landing distance
Density Altitude
Density altitude is a way of relating the density of the air you are in compared to the standard
atmosphere. Three atmospheres are illustrated. The Standard Atmosphere (29.92 in. Hg and 15 degrees
Celsius) in middle shown in gray. A less dense atmosphere (A ) (lower pressure and/or Higher
Temperature) is shown on the right in red. A more dense atmosphere (B) (higher pressure and/or Colder
Temperature) is illustrated on the left in blue.
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If you are at an actual (true) altitude at location A in atmosphere (A) (the red atmosphere on the right),
you will have to go to altitude (A') in the Standard Atmosphere to find the same air density. This altitude
in the standard atmosphere at (A') is called the DENSITY ALTITUDE.
Similarly, if you are at atmosphere (B) (colder or high pressure shown as blue on the left) the air will be
more dense than standard. Therefore you will have to go down to a lower actual altitude in the standard
atmosphere at (B') to find the equivalent air density. This equivalent altitude in the Standard Atmosphere
is the DENSITY ALTITUDE.
The reason that you need to convert your actual non-standard altitude (and thus your non-standard air
density) to the standard density altitude is that all performance charts and data is based on a standard
atmosphere. For example, if you are at a high altitude runway already, and the atmosphere pressure is
low and temperature is high, it will require a significantly longer take off run than you may be
accustomed to at your lower home base. If you are not aware of the effects of density altitude on your
aircraft performance, it could lead to serious consequences.
Density Altitude Calculations
Density Altitude can be found in two ways
· Using conversion charts
· Using the E6B Flight Computer Density Altitude calculation is a 2 step process.
Step 1. Find Pressure Altitude
Pressure Altitude adjusts for pressure difference between your air and standard atmosphere. The question
is “What would your altimeter read if you were in a standard atmosphere at your current actual
altitude?” This altitude is called PRESSURE ALTITUDE.
Pressure Altitude can be determined two ways.
· In the aircraft, adjust your altimeter setting to 29.92 in. Hg (standard pressure), and read the altitude
value shown by the altimeter needles. Or...
· Apply a correction factor from a Pressure Altitude Correction Table as shown below.
PRESSURE ALTITUDE CONVERSION TABLE
In. Hg Conv. Factor In. Hg Conf. Factor In. Hg Conv. Factor In. Hg Conv. Factor
28.0 1824 28.8 1053 29.6 298 30.3 -348
28.1 1727 28.9 975 29.7 205 30.4 -440
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28.2 1630 29.0 863 29.8 112 30.5 -531
28.3 1533 29.1 768 29.9 20 30.6 -622
28.4 1336 29.2 673 29.92 0 30.7 -712
28.5 1340 29.3 579 30.0 -73 30.8 -803
28.6 1148 29.4 485 30.1 -175 30.9 -893
28.7 1148 29.5 392 30.2 -257 31.0 -983
EXAMPLE:
Airport Altitude = 2367 ft
Altimeter Setting = 30.40 In. Hg
Conversion Factor= -440 feet (from table )
Pressure Altitude = Airport Altitude + Conversion Factor =2367+(- 440) = 1927
NOTE: If your barometric pressure is not shown in the table (say a value such as 30.35) you will have to
interpolate to get the correct pressure altitude adjustment.
Step 2. Find Density Altitude
Density Altitude uses Pressure Altitude as a basis, and adds in a correction factor for non-standard
temperature.
Calculate Density Altitude using:
1. PRESSURE ALTITUDE and
2. Outside Air Temperature (OAT)
· Use E6B Flight Computer (see E6B instruction book)
· Use Density Altitude Chart like the one shown below.
Density AltFor Example: If you found the Pressure Altitude, doing either of the steps cited above, to be
4000 feet, and the outside Air Temperature (OAT) is 16° , do the following on the chart to
find Density Altitude.
Locate 16° C on bottom scale. Go vertically up to intersect the 4000 foot Pressure Altitude slanted line
(blue line). Go left horizontally (blue line) to read Density Altitude = 5000 feet from the left side scale.
You have now adjusted for the difference from standard temperature by using the chart.
The red line on the chart is a Standard Atmosphere Temperature line.
Performance charts provided by the manufacturer are based on Standard Atmosphere. Therefore you
must adjust your current situation (barometric pressure and temperature) to Standard Atmosphere. This is
done by calculating your Density Altitude, then using this Density Altitude as the altitude in the
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manufacturers performance table when interpreting the performance table data.
Aircraft Performance Charts
Aircraft Performance Charts state performance figures in standard atmosphere conditions.
Takeoff Performance
You should consult the manufacturers Pilot Operating Handbook for the aircraft to be flown for take-off
performance tables or graphs.
Takeoff performance is influenced by several factors.
· Adverse conditions
1. High density altitude (high altitude runway, low pressure, high temperature)
2. Runway conditions - mud, soft field, slush, snow, tall grass, rough surface, uphill
3. Tailwind (downwind takeoff)
4. High gross weight or overload
5. High Humidity
· Favorable conditions
6. Low density altitude (low altitude runway, low temperature, high pressure)
7. Downhill runway
8. Headwind
9. Low weight
10. Low Humidity
Takeoff performance data shown in the manufacturers' charts indicates the minimum runway
requirements necessary for successful takeoff. Any factor that adversely affects the takeoff distance must
be taken into account to insure safe operation. Consider that the listed minimum distance is for standard
atmospheric conditions, ideal runway and wind conditions.
TAKEOFF PERFORMANCE
0000' & 59 deg
F
2500' & 50 deg
F
5000' & 41 deg
F
7500' & 32 deg
F
GROSS
WT.
POUNDS
IAS@50'
MPH
HEAD
WIND
GRND
RUN
CLEAR
50'
OBS
GRND
RUN
CLEAR
50'
OBS
GRND
RUN
CLEAR
50'
OBS
GRND
RUN
CLEAR
50'
OBS
2300 68 0 865 1525 1040 1910 1255 2480 1565 3855
2300 68 10 615 1170 750 1485 920 1955 1160 3110
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2300 68 20 405 850 505 1100 630 1480 810 2425
2000 63 0 630 1095 735 1325 905 1625 1120 2155
2000 63 10 435 820 530 1005 645 1250 810 1685
2000 63 20 275 580 340 730 425 910 595 1255
1700 58 0 435 780 520 920 625 1095 765 1370
1700 58 10 290 570 355 680 430 820 535 1040
1700 58 20 175 385 215 470 270 575 345 745
Wind direction and velocity significantly affect takeoff distance. A direct headwind will greatest provide
takeoff assist. A 90° crosswind will give no assistance in takeoff. A tailwind component significantly
increases the takeoff roll.
Gross weight affects takeoff performance.
Increased gross weight:
· Requires a higher takeoff speed in order to achieve sufficient lift.
· Results in reduced acceleration due to greater inertia.
· Increases rolling friction , further reduceing acceleration.
Gusting or strong crosswinds require that the aircraft be held on the ground until definite liftoff can be
achieved. Once liftoff has occured, sufficient speed is needed to prevent settling back onto the runway. If
the landing gear contacts the runway when in a sideways drift, undue stress is placed on the landing gear.
Glide Performance
Glide performance is the distance that the aircraft will glide with an inoperative engine. The best distance
is attained by gilding at an angle of attack that provides the maximum lift/drag ratio (L/Dmax).
In the event that the engine becomes inoperative, it is important to establish the maximum glide airspeed
as quickly as possible. This will permit the maximum radius of emergency landing options. While
gliding toward a suitable landing area, effort should be made to identify the cause of the failure. If time
permits, an engine restart should be attempted as shown in the start-up check list.
Climb Performance
The Pilot Operating Handbook will contain a Climb Performance chart or Table similar to the one below
for a given aircraft. Note that 4 different tables are provided. (Sea Level, 5000 ft, 10,000 ft and 15,000
ft). Note that these altitudes are PRESSURE ALTITUDES and the respective temperatures are Standard
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MAXIMUM RATE OF CLIMB DATA
Sea Level & 59° F 5000' & 41° F 10,000' & 23° 15,000 & 5° F
Gross
Weight
lbs.
Ind.
Airspeed
mph
Rate
of
climb
ft/min
Fuel
Used
gal.
Ind.
Airspeed
mph
Rate
of
Climb
ft/min
Fuel
Used
gal
Ind.
Airspeed
Ft/min
Rate
of
Climb
ft/min
Fuel
Used
gal.
Ind.
Airspeed
mph
Rate
of
Climb
ft/min
Fuel
Used
gal
2300 82 645 1.0 81 435 2.6 79 230 4.8 78 22 11.5
2000 79 840 1.0 79 610 2.2 76 380 3.6 75 155 6.3
1700 77 1085 1.0 76 825 1.9 73 570 2.9 72 315 4.4
NOTES:
1. Flaps up, full throttle, mixture leaned above 3000 feet for smooth operation.
2. Fuel Used includes, warm-up and take-off allowance.
3. For hot weather, decrease rate of climb 20 ft/min for each 10°F above standard day for the particular altitude.
Example:
Given: Gross weight 2000 lb: Pressure Alt. 5000 ft: Temperature 61° F.
SOLUTION:
The rate of climb is 610 at 5000 feet pressure altitude and standard temperature of 41° F. Since the
temperature is 20° F higher that the standard 41°, subtract 40 feet per minute from the 610, to get a rate
of climb = 610 - 40 = 570 ft/min.
Climb performance depends on the aircraft’s reserve power or thrust. Reserve power is the available
power above that required to maintain level flight at a given airspeed. If an aircraft requires only 120
horsepower for a given cruise, and the engine is capable of delivering 180 hp., then the reserve
horsepower available for climb is 60 hp.
Two airspeeds are important to the climb performance. These are:
Vx Best Angle of Climb
Vy Best Rate of Climb
These V-speeds are defined in the POH. The Best Angle of Climb produces the greatest altitude in a
given distance. The principal use of Best Angle of Climb is for clearing obstacles on take-off. The Best
Rate of Climb produces the greatest altitude over a given period of time. It is predominately used as
climb to cruise altitude.
Many of the same factors that affect take-off and cruise performance also affect climb performance.
Adverse effects:
· Higher than Standard Temperature
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· High Humidity
· Lower than Standard Pressure
· Heavy Weight
Heavy weight requires a higher angle of attack to develop adequate lift. The increased drag results in
poorer climb performance. It takes longer to attain cruise altitude and requires the engine to develop full
power for a longer period of time.
Consult the POH for Climb Performance data for the aircraft to be flown.
Cruise Performance
The cruise performance can be specified two ways.
· Maximum Range
· Maximum Endurance
Maximum Range is the distance that an aircraft can fly at a given power setting. is requires maximum
speed versus fuel flow. Maximum Duration is the maximum time the aircraft can fly. This requires that
the flight condition must provide for a minimum of fuel flow.
CRUISE AND RANGE PERFORMANCE
ALTITUDE RPM % PWR TAS MPH GAL/HR END HRS RANGE MI.
2500 2600 81 136 9.3 3.9 524
2500 2500 73 129 8.3 4.3 555
2500 2400 65 122 7.5 4.8 586
2500 2300 56 115 6.6 5.4 617
2500 2200 52 108 6.0 6.0 645
4500 2600 77 135 8.8 4.0 539
4500 2500 69 129 7.9 4.5 572
4500 2400 62 121 7.1 5.0 601
4500 2300 56 113 6.4 5.5 628
4500 2200 51 106 5.7 6.1 646
6500 2700 81 140 9.3 3.8 530
6500 2600 73 134 8.3 4.2 559
6500 2500 66 126 7.5 4.7 587
6500 2400 60 119 6.8 5.2 611
6500 2300 54 112 6.1 5.7 632
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8500 2700 77 139 8.8 4.0 547
8500 2600 70 132 7.9 4.4 575
8500 2500 63 125 7.2 4.9 599
8500 2400 57 118 6.5 5.3 620
8500 2300 52 109 5.9 5.8 635
10500 2700 73 138 8.3 4.2 569
10500 2600 66 130 7.6 4.6 590
10500 2500 60 122 6.9 5.0 610
10500 2400 55 115 6.3 5.4 625
10500 2300 50 106 5.7 5.9 631
Crosswind Performance
Takeoffs and landings under significant cross wind conditions can be dangerous and should be avoided.
Crosswinds can be so strong that the sideways drift cannot be sufficiently overcome by using a “side slip
” into the wind to compensate for the wind drift. Excessive side load on the landing gear can cause gear
failure or an upset aircraft.
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The Maximum Crosswind Component for the aircraft will be listed in the
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POH. The maximum crosswind is usually
about 20% of the landing configuration stall
speed. The diagram above can be used to
calculate the headwind and crosswind
components. For most light aircraft, the
maximum tested crosswind component is in
the 12 to 15 knot range. In the chart, the
numbers around the periphery of the chart
mark the degrees difference between the
wind and the runway heading (magenta
lines). The radial lines are are in 5°
increments with numbers on each 10° line.
For example, with a wind of 150° at 30 kt
and landing on runway 12 (120°), the
degrees of crosswind will be 150° - 120° =
30°. Locate the 30° radial line out from the
lower left of the graph. This is the
differential between the wind direction and
thr runway heading. Follow the 30° radial
line (magenta) to the 30kt wind arc (blue). A
vertical line (blue) from this intersection will
be the cross-wind component of 15 kts. This
is the same as if you had a wind of 15 kts
directly from the side.
If you plot a horizontal (blue) line, you will see that your headwind component is 26 kts. This is the same
effect as if you had a direct headwind of 26 kts.
Landing Performance
The minimum landing distance is attained by landing at the minimum safe speed which allows sufficient
margin above the stall speed for satisfactory control and go-around capability. Gross weight and
headwind are important considerations in determining minimum landing distance.
Excessive airspeed above that recommended in the POH will significantly increase landing distance.
High density altitude increases landing distance. As a rule of thumb, the increase in landing distance is
about 3.5% for each 1,000 feet in density altitude.
Braking
A number of factors affect braking. A wet, icy or snow covered runway will appreciably decrease
braking ability. In crosswinds or gusty conditions, higher than normal approach speed will improve
controllability, but will require longer rollout to stop. A down-sloping runway also increases stopping
distance.
Braking immediately after touchdown is ineffective because the wings are still producing lift. The pilot
should use the natural aerodynamic drag as much as possible to slow the aircraft. Maintain up-elevator to
a high angle of attack as long as possible. The nose of the aircraft will settle naturally as airspeed is
dissipated. Therefore it is not necessary (and is unwise) to force the nosewheel hard onto the runway.
After touchdown, hold up-elevators during braking to reduce the load on the nosewheel. Avoid severe
braking to minimize stress on the nose gear and scrubbing of rubber from the main gear tires.
Gross weight affects stopping ability. Heavy loads and high touchdown speeds result in greater forward
momentum, and require significantly more runway than normal. The most critical conditions for landing
performance sult from some combination of high gross weight , high density altitude and unfavorable
wind conditions. These conditions produce the greatest landing distance and require the greatest
dissipation of energy by the brakes.
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AIRSPACE AND AIRPORT TYPES
AIRSPACE AND AIRPORT TYPES
In September 1993 the FAA adopted the International Civil Aviation Organization (ICAO) definition of airspace
segments. The ICAO classifications of airspace are named A through G. The classification of “F” is not used in
the USA.
NOTE: It will be helpful while studying this chapter to have a Sectional Aeronautical Chart available. Refer to
the front panel of the chart as well as to content of the chart as you study this chapter.
The 3 predominant types of airspace are:
· Positive Control (Class A) - White
· Controlled (Class E - Yellow )
· Uncontrolled (class G) - Magenta
Class G Airspace
ATC exercises no jurisdiction over Class G airspace. It
is the airspace shown in magenta at left, and generally
extends from the ground up to 1200 feet above ground
level (AGL). As such it is classified as Uncontrolled
airspace.
ATC exercises some jurisdiction, at varying degrees to all other airspace. Thus all other airspace is classifies as
Controlled airspace.
Class A -- Positive Control
ATC exercises complete control in the Positive Controlled airspace. Jet aircraft is the primary user of Class A
airspace. It ranges from 18,000 feet (Flight Level 180) to 60,000 feet (FL600). Altitudes 18,000 feet and above
are called Flight Levels.
Class A airspace is not specifically charted on aeronautical charts. Operation is in accordance to Instrument Flight
Rules (IFR). The aircraft must be equipped with appropriate IFR instrumentation, including a Mode C altitude
reporting Transponder. The Pilot must be Instrument rated. An IFR flight plan is required. ATC exercises full
control of route, speed, and altitude. ATC is responsible for aircraft separation in Class A airspace.
See AIM Chapter 3 for further data on Class A Airspace
Class E -- Controlled
Class E airspace is from altitude 1200 feet Above Ground Level (AGL) up to 18,000 feet. All airspace from
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14,500 feet (MSL) to 18,000 feet (MSL) is Class E. It contains the Low Altitude Victor airway system. These
airways are designated on the aeronautical charts as blue lines about 1/16 inch wide, and have numbers like V12,
V245, etc. written on them. They are roads in the sky. All Victor airways are Class E extending 6 nautical miles
each side of the airway centerline. In mountainous terrain, class G airspace may exist from the surface to 14,500
feet outside the boundaries of the airway. In non-mountainous terain (such as Eastern US) all the airspace above
1200 AGL is Class E unless specified otherwise.
ATC exercises no control over flights operating under Visual Flight Rules (VFR) in Class E airspace. Radio
communication and Transponder are not required. Specific cloud clearance and visibility requirements apply to
Class E airspace. These are listed in the chart at the end of this section. ATC does exercise control of aircraft
operating under Instrument Flight Rules (IFR). IFR flights must maintain altitudes, routes and speeds a directed
by ATC. IFR flights must be capable of communicating with ATC, and must be Mode C Transponder equipped
(capable of reporting altitude to the radar scope).
There are no specific certification requirements, other than normal pilot certificates. Class E airspace may be
designated from the surface upward as extension to class B, C, and D airspace (defined later) to accommodate
IFR traffic requirements. Class E airspace will extend downward to 700 feet AGL around uncontrolled airports
that have published instrument approach procedures. These areas around uncontrolled airports where the Class E airspace goes down to 700 feet AGL instead of the
standard 1200 feet AGL are depicted on Aeronautical Charts by a wide shaded magenta colored band around the
airport. The reason the Class E airspace extends nearer to the ground is to provide a controlled airspace transition
area for aircraft operating IFR and making an IFR approach.
See AIM Chapter 3 for further data on Class E Airspace
Class G -- Uncontrolled
Most Class G airspace is that space from the surface up to 1200 feet. However, there are areas in mountainous
terrain where airspace outside the Victor Airways is Class G from the ground to 14,500 feet AGL. Class G space
may underlie Classes B, C, and D, but has no specific symbol indicated on the chart. The presence of the airspace
is implied. Less stringent minimum cloud clearance and visibility requirements apply to VFR flight in Class G
space since ATC does not maintain jurisdiction over this airspace. See last page of this section.
As mentioned in the Class E section, airports with published instrument approached have class E airspace
extending down to 700 feet AGL. Obviously, in these areas, Class G only extends from the surface to 700 feet
AGL.
Uncontrolled Airports
Airports without a control tower are classifies as uncontrolled. Three types of uncontrolled airports are shown
below.
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The airport on the right does not have an instrument approach or a control zone around the airport. The airspace
overlying this type airport is Class G up to 1200 feet, then Class E above. It is depicted on the charts as a magenta
circle (unpaved) or a solid circle with white runways (paved).
The airport in the middle has a Class E Control Zone around it, depicted by the dotted circle around it. If the line
is magenta in color, it is a control zone at an airport where an FAA Flight Service Station (FSS) is on the field but
no control tower. The FSS provides airport traffic advisory service. Class E airspace extends down to the surface.
The zone is depicted on charts as a dashed MAGENTA circle around the airport. These airports usually have
instrument approach procedures as well.
The airport at left has an instrument approach procedure for the airport. Such airports have a broad lightly shaded
magenta band around them. Within the outer edge of the band, Class G airspace only extends up to 700 feet AGL.
Class E extends down to 700 feet to provide a transition zone for aircraft making instrument approaches to the
airport. The transition area is approximately 5 miles in radius.
Controlled Airports
These are airports that have sufficient air traffic to warrant a Control Tower, and in some cases Approach Control
and Ground Control Radar. They are used by air carrier operations, and can have a mix of jet, high performance
piston and turbine aircraft, as well as smaller single engine aircraft. The control tower is responsible for aircraft
separation within its jurisdiction. Certain clearances must be obtained from ATC for operations on the airport
surface, and within the controlled airspace around the airport.
There are 3 Classes of airspace around controlled airports. The type of airspace depends upon the traffic volume
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and types of flight. These Classes are B, C, and D airspace
Class D -- Airports with Control Tower
The lowest level of control is at airports with a low volume of traffic. It has a control tower and is depicted on the
aeronautical charts as shown below.
Class D airports are depicted on aeronautical charts by a blue dashed circle around the airport symbol. Within the
dashed circle is a number enclosed in a dashed square. This number indicates the top of the Class D airspace,
expressed in hundreds of feet (MSL). In the diagram, the top is 4,600 feet MSL This airspace may have a Class E
extension as shown in the diagram for an IFR approach transition area.
The control tower has jurisdiction within the Class D airspace which is 5 Statute Miles radius around the control
tower. The top of the Class D airspace extends 2500 feet above the surface of the airport. Two way radio contact
must be maintained with the Control Tower while in this airspace. The pilot should contact the control tower
prior to entering the airspace.
See AIM Chapter 3 for further data on Class D Airspace
Terminal Radar Service Areas (TRSA)
Some Class D airports have a local radar service called a Terminal Radar Service Area.(TRSA). The service is
available for conflict resolution and traffic sequencing to departing and arriving aircraft. However contact with
the radar is not mandatory and the pilot may decline the service.
These airports are depicted on the aeronautical charts in the normal Class D manner, but have a dark gray circular
line around the airport out at the boundary of the radar service range. Wilmington N.C. and Augusta Ga. are
examples of airports with TRSA. There is no specified regulatory radius for the radar service.
See AIM Chapter 3 for further data on Terminal Radar Service Area
Class C Airspace (Mandatory Radar)
Class C airspace has two concentric tiers. The inner circle is 5 nautical mile core area extending to 4000 feet
above the surface. It is similar in function to Class D airspace where the tower usually maintains jurisdiction.
A shelf area with an outer radius of 10 nautical miles surrounds the core area. It extends from 1200 feet AGL to
4000 feet AGL. The airspace is depicted on charts as 2 concentric magenta circles.
For example, an airport with a surface altitude of 500 feet MSL is depicted above. The left diagram is a side
profile of the airspace. The right diagran shows how the airspace is depicted on the aeronautical chart.
The ceiling of the Class C airspace is 4,500 feet (MSL). This is calculated as runway altitude of 500 feet plus
4000 feet. The floor of the outer shelf is 1,700 feet MSL. (1200 + 500 feet). The space under the shelf is Class G.
These altitudes are indicated by 45 over SFC for the core circle, and 45 over 17 on the outer shelf.
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Contact with Approach and Departure Radar Control is mandatory within the core and shelf airspace. During
takeoff and landing, the tower and radar controller coordinate their activity. You will be told by either controller
when to switch frequency to the other controller. Aircraft must be capable of two-way communication with the
radar facility and the tower. A 4096 Altitude Reporting (Mode C) Transponder is required when operating within,
under or above Class C airspace.
Before entering Class C airspace, the pilot MUST establish communication with the radar service. Radio contact
with radar and/or tower must be maintained when in this airspace.
You may request Flight Following Radar Service outside the 10 mile shelf. It may be granted on a workload
permitting basis. The service can usually be provided to about a 20 NM radius of the airport.
See AIM Chapter 3 for further data on Class C Airspace
Class B -- Large Terminal Airports
Large terminal areas such as the New York, Chicago, and Los Angeles areas have a high volume of air traffic.
The airspace around these airports is under rigid control of ATC, and are called Class B airspace.
AIRCRAFT MUST HAVE ATC CLEARANCE PRIOR TO ENTRY INTO THIS AIRSPACE.
The airspace is composed generally of three concentric tiers. A core area around the airport is generally is
surrounded by two additional shelf areas extending approximately 30 nautical mile radius from the primary
airport.
The core area extends from the surface to 10,000 feet AGL. The second shelf has a wider radius and has both a
floor and a ceiling. The ceiling is the same as the inner circle. The floor may vary at differing altitudes in various
sections to accommodate smaller airports that underlie the middle tier of airspace.
The third shelf extends out approximately 30 Nm from the airport. It has the same ceiling as the other two tiers,
but has a higher floor than the middle shelf. This floor may also be variable in altitude to accommodate airports
lying beneath the Class B airspace.
The actual configuration of the airspace varies to accommodate local operational requirements. The purpose of
the Class B structure is to allow large high performance jet traffic to transition down to landing at the airport
under IFR procedures, and with positive control and traffic separation.
Class B operational rules require:
· Two way radio capable of communication with ATC.
· Private pilot (or special student certification). Several airports prohibit student operations entirely.
· Altitude reporting Transponder (Mode C).
·If operating IFR, an operable VOR or TACAN receiver.
NOTE: Student pilots must have had training in Class B operations and appropriate sign-off of a Certified Flight
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Instructor.
A student may not operate from the following Class B airports.
Atlanta Hartsfield Airport, GA Newark Airport, NJ Boston Logan Airport, MA New York Kennedy, NY Chicago
O’Hare Airport IL New York LaGuardia, NY Dallas/Ft.Worth Airport, TX San Francisco Airport, CA Loa
Angeles Airport, CA Washington National Airport, DC Miami Airport, FL Andrews AFB, MD
See AIM Chapter 3 for further data on Class B Airspace
Mode C Veil
Around Class B airspace is an area called the Mode C Veil. It is shown as a thin blue concentric line of 30
Nautical Mile radius around the Class B airport. An altitude reporting Transponder (Mode C) is required within
this area and when operating under the floor or above the ceiling of the Class B airspace. Radio communication
with ATC is not required as long as you stay outside the Class B airspace.
Special Use Airspace
A number of “special use” airspace areas exist for various usage. It means that certain activities have been
confined to those areas of airspace. Limitations are placed on aircraft operations in these areas which are not a
part of the activity. These are:
· Prohibited areas
· Restricted areas
· Warning Areas
· Military Operations Areas
· Alert Areas
· Controlled Firing Areas
· Military Training Routes
· Air Defense Identification Zone
· Temporary Restricted Areas
Prohibited and Restricted airspace are regulatory use airspace whose rules are defined by FAR Part 73. Warning
areas, MOA’s, Alert Areas, National Security Areas, and controlled firing areas are non-regulatory special use
airspace.
Prohibited Areas
These are areas over which flight by civilian aircraft is prohibited by FAA Regulation. Operation within such an
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area can be justification for military interception or other action. The area around the White House in Washington
D.C. is an example. The symbol is a blue feathered box shown at right with the words Prohibited in or near the
box.
See Aeronautical Information Manual AIM 3-31 PROHIBITED AREAS .
Restricted Areas
These are designated areas in which flight, although not totally prohibited, are subject to certain restrictions.
These areas denote the existence of unusual, often invisible, hazards to aircraft. Such activities may be artillery
firing, aerial gunnery, or guided missiles. Penetration of these areas without authorization of the controlling
agency may be extremely dangerous. They are marked on the charts by blue feathered boundaries.
An identifying number such as R-5306 will be listed near or within the area. A listing on the bottom of the
aeronautical chart identifies the area by number, and indicates the location of the area, the altitude limits of the
space, the time of use, and the name of the controlling agency. It is good practice to plan to avoid such areas. If
penetration of such an area is planned, the controlling agency should be consulted as to the status of activity in the
area prior to any penetration.
For more information, see AIM 3-32 RESTRICTED AREAS
Warning Areas
These are areas outside the 3 mile limit from shore in international airspace. They are similar to Restricted Areas.
Activities which are unusual or may be dangerous to aircraft may be in progress. They cannot however be
designated as Restricted Areas since they are over international waters
Warning areas are also identified by a blue feathered box with a number (such as W-74). Information concerning
these areas is listed on the aeronautical charts in the same section as Restricted Areas. One should treat a Warning
Area the same as a Restricted area, and follow the same procedures.
For more information, see AIM 3-33. WARNING AREA
Military Operation Areas (MOA)
MOAs consist of airspace of defined vertical and lateral limits for the purpose of separating certain military
training activities and IFR traffic. They are depicted by magenta colored feathered areas similarly to Prohibited,
Restricted and Warning areas. They are denoted by names such as Beaufort MOA within or near the MOAdefined area. ATC can grant clearance to IFR traffic through an MOA if adequate IFR separation can be assured.
If not, ATC will restrict routing IFR traffic through the area.
Most military training activities necessitate acrobatic or abrupt maneuvers. Pilots operating under VFR should
exercise extreme caution whole flying in an MOA when military activity is being conducted. Military pilots on
officially designated operations are exempt from conducting aerobatic maneuvers on the regions of Victor
Airways.
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VFR pilots should maintain caution when flying through an MOA when it is active. Pilots should contact a Flight
Service Station (FSS) within 100 miles of the MOA to obtain real-time report of activity within the MOA. Prior
to entry, pilots should contact the controlling agency for traffic advisories. Information about MOAs is listed in
the same location on the aeronautical chart as the Restricted and Warning area information. The data is printed in
Magenta.
For mor information, see 3-34. MILITARY OPERATIONS AREAS (MOA)
Alert Areas
Alert areas are shown on charts to inform pilots of areas where intensive pilot training or other types of unusual
aerial activity may take place. The area is depicted in a similar manner to the other special use areas, but indicated
by a blue outline with the area crosshatched as shown.
For more information, see AIM 3-35. ALERT AREAS
Controlled Firing Areas
These areas contain operations such as artillery firing. They are not marked on charts, and pilots need not avoid.
Spotter aircraft, radar or ground personnel monitor for aircraft in the area, and firing is suspended immediately
upon the approach of aircraft.
See AIM 3-36. CONTROLLED FIRING AREAS
Military Training Routes
Military training routes are used by high speed military aircraft conducting low and medium level high speed
training activity. The routes above 1500 feet AGL are designed to be flown mostly under IFR rules. They may
occur in either IFR or VFR meteorological conditions. The routes at 1500 feet and below are generally developed
to be flown under VFR rules. Flight visibility must be 5 miles or more, with ceilings 3000 feet or more.
MTR’s with no segment above 1500 feet will be designated by a 4 digit number; i.e. IR 1206, VR 1207. Routes
that include one or more segments above 1500 feet are designated by 3 digit numbers; i.e. IR206, VR207.
The routes are shown on aeronautical charts are gray in color, and will have numbers like IR718 or VR4003.
Vigilance should be observed when operating near or crossing an MTR. Contact FSS within 100 miles to obtain
current information on the activity along the MTRs. Give FSS your altitude and route of flight and destination
when requesting MTR information.
For further information, see 3-41. MILITARY TRAINING ROUTES (MTR)
Temporary Restricted Areas
The FAA may publish temporary restricted areas that may be due natural disaster, or other events, in which
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unauthorized civilian flight is inadvisable or may interfere with rescue or relief efforts. These temporary
restrictions are published through the system called “Notices To Airmen” (NOTAMS). They are disseminated
through the FAA Flight Service Stations. Contact FSS prior to any flight which may be in the vicinity of such
events as air crashes, earthquake damage, floods, etc.
Airspace Rules
The various types of airspace have rules concerning weather limitations and equipment requirements for
operation in the given airspace. The listing below summarizes these requirements.
Standard VFR Cloud Clearance and Visibility
Hereinafter, reference will be made to standard VFR Rules for Cloud Clearance and Visibility. These are:
VFR Couud Clearance and Visibility Rules
Visibility Above Cloud Below Cloud Horizontal
Below 10,000 ft. 3 1000 ft 500 ft 2000 ft
Above 10,000 ft. 5 1000 ft. 1000 ft. 1 SM.
Class A Airspace Rules
l Operations - Instrument Flight Rules Only
l ATC Clearance Required - Yes
l Radio Contact Required - Yes
l Minimum Pilot Qualifications - Instrument Rating
l Mode C Altitude Encoding Transponder Required - Yes
l Cloud Clearance Requirements - None (IFR Rules apply)
Class B Airspace Rules
While in Class B airspace, the following rules apply.
l Operations Permitted - IFR and VFR
l ATC Clearance Required - Yes
l Radio Contact Required - Yes
l Minimum Pilot Qualifications - Private (Student if Signed-Off)
l Mode C Altitude Reporting Transponder required - Yes
l Cloud Clearance Requirements below 10,000 ft. - Clear of Clouds
l Cloud Clearance Requirements above 10,000 ft. - Standard VFR
l VFR Visibility Requirements below 10,000 ft. - Standard VFR
l VFR Visibility Requirements above 10,000 feet - Standard VFR
Class C Airspace Rules
While in Class C airspace, the following rules apply.
l Operations Permitted - IFR and VFR
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l ATC Clearance Required - IFR - Yes : VFR - No
l Radio Contact Required - Yes
l Minimum Pilot Qualifications - Student
l Mode C Altitude Reporting Transponder required - Yes
l Cloud Clearance Requirements below 10,000 ft. - Standard VFR
l Cloud Clearance Requirements above 10,000 ft. - Standard VFR
l VFR Visibility Requirements below 10,000 ft. - Standard VFR
l VFR Visibility Requirements above 10,000 feet - Standard VFR
Airspace Class D Rules
While in Class D airspace, the following rules apply.
l Operations Permitted - IFR and VFR
l ATC Clearance Required - IFR -Yes: VFR - No
l Radio Contact Required - Yes
l Minimum Pilot Qualifications - Student
l Mode C Altitude Reporting Transponder required - No
l Cloud Clearance Requirements below 10,000 ft. - Standard VFR
l Cloud Clearance Requirements above 10,000 ft. - Standard VFR
l VFR Visibility Requirements below 10,000 ft. - Standard VFR
l VFR Visibility Requirements above 10,000 feet - Standard VFR
Airspace Class G Rules
While in Class G airspace, the following rules apply.
l Operations Permitted - VFR
l ATC Clearance Required - No
l Radio Contact Required - No
l Minimum Pilot Qualifications - Student
l Mode C Altitude Reporting Transponder required - No
l Cloud Clearance Requirements below 10,000 ft. - Clear of Clouds (Day) : Standard VFR (night)
l Cloud Clearance Requirements above 10,000 ft. - Standard VFR (day and Night
l VFR Visibility Requirements below 10,000 ft. - 1 SM (day): 3 SM (night)
l VFR Visibility Requirements above 10,000 feet - Standard VFR (day and night)
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Chart Symbols
Aeronautical Charts
Chart Types
Three types of charts are used for VFR flight. These are:
· Wide Area Charts(WAC) - Scale 1:1,000,000 ( 1 inch = 13.7 Nm)
· Sectional Chart.................- Scale 1:500,000 ( 1 inch = 6.86 Nm)
· VFR Terminal Charts........- Scale 1:250,000 ( 1 inch = 3.43 Nm)
Most pilots use the Sectional chart. It provides good detail of topographical features, and is good for both the
Student pilot as well as experienced pilot.
Since the WAC chart covers twice the area of the Sectional, pilots flying higher performance aircraft may prefer
this chart. It shows less topographical features. It contains most of the electronic navigation features that are
shown on the sectional charts. Both the WAC and Sectional charts show the Victor Airways.
VFR Terminal Charts are published for areas of concentrated air traffic, such as Charlotte, NYC, Los Angeles,
etc. These charts show many more details. They contain landmarks often used by controllers not shown on the
other chart types.
Charts show significant terrain and topographical detail, location of cities and towns, airports, navigational aids,
prohibited, restricted and special use airspace, and many other symbols.
Longitude and Latitude
A system of X-Y coordinates is used to define a point
on the earth's surface. These coordinates are called
Meridians (longitude) and Parallels (latitude).
Meridians span from the north pole to the south pole,
and are measured in degrees from the PRIME
MERIDIAN. It runs north and south through
Greenwich, England. Measurement is either EAST or
WEST from the Prime Meridian, and continues
around the earth until they meet at meridian 180.The
measurement, either East or West is measured in
degrees, minutes and seconds. This measurement is
called “Longitude”. The example dot on the diagram
is at Longitude 30° 45’ W ( 30 degrees, 45 minutes
West).
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Meridians are not parallel. They converge at the poles, and have maximum distance between them at the equator.
They represent the direction to True North. At the equator, one minute of arc longitude equals one nautical mile.
The only place where 1° longitude = 1 Nm is on the equator. As one moves toward either pole, the lateral distance
across one degree becomes less and less, and approaches zero at the pole. Since the earth makes one revolution of
360 degrees within 24 hours, it moves 15° in one hour.
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