Performance and Limitations

Question 1

What are the four dynamic forces that act on an airplane during all maneuvers?

Answer 1

Lift, gravity, thrust, and drag.

FAA-H-8083-25

Question 2

What flight condition will result in the sum of the opposing forces being equal?

Answer 2

In steady-state, straight-and-level, unaccelerated flight the sum of the opposing forces is equal to zero. This is true whether flying level or when climbing or descending.
(FAA-H-8083-25)

Question 3

What is an airfoil?

Answer 3

An airfoil is a device which gest useful reaction from air moving over its surface, namely lift. Wings, horizontal tail surfaces, vertical tail surfaces, and propellers are examples of airfoils.
(FAA-H-8083-25)

Question 4

What is the “angle of incidence”?

Answer 4

The angle of incidence is the angle formed by the longitudinal axis of the airplane and the chord of the wing. It is measured by the angle at which the wing is attached to the fuselage. The angle of incidence is fixed and cannot be changed by the pilot.
(FAA-H-8083-25)

Question 5

What is “relative wind”?

Answer 5

The relative wind is the direction of the airflow with respect to the wing. When a wing is moving forward and downward the relative wind moves backward and upward. The flight path and relative wind are always parallel but travel in opposite directions.
(FAA-H-8083-25)

Question 6

What is the “angle of attack”?

Answer 6

The angle of attack is the angle between the wing chord line and the direction of the relative wind; it can be changed by the pilot.
(FAA-H-8083-25)

Question 7

What is “Bernoulli’s Principle”?

Answer 7

The pressured of a fluid decreases at points where the speed of the fluid increases. In the case of airflow, high speed flow is associated with low pressured and low speed flow with high pressured. The airfoil of an aircraft is designed to increase the velocity of airflow above its surface, thereby decreasing pressure above the airfoil and causing increased pressure below the airfoil to result in lift.
(FAA-H-8083-25)

Question 8

What are several factors that will affect both lift and drag?

Answer 8

Wing area - Lift and drag acting on a wing are roughly proportional to the wing area.
Shape of the airfoil - As the upper curvature of an airfoil is increased the lift produced increases (to a point). Lowering an aileron or flap device can accomplish this. Ice or frost on a wing can disturb normal airflow, changing the camber and disrupting lift capability.
Angle of attack - As angle of attack is increased, both lift and drag are increased (to a point).
Air density - Lift and drag vary directly with density of the air. As air density increases and decreases lift and drag increase and decrease as well. Density is affected by: pressure, temperature, and humidity.

Question 9

What is “torque effect”?

Answer 9

Newton’s third law of physics: for every action, there is an equal and opposite reaction. As the propeller rotates in one direction there is an equal force trying to rotate the airplane in the opposite direction. It is greatest at low airspeeds with high power settings and a high angle of attack (takeoff).
(FAA-H-8083-25)

Question 10

What effect does torque reaction have on an airplane on the ground and in flight?

Answer 10

In flight - Torque reaction acts around the longitudinal axis tending to make the airplane roll. Older planes are rigged to provide more lift on the wing being forced down. Modern planes use engine offset to counteract this effect of torque.
On the ground - During the takeoff roll, torque effect places more weight on the left gear. This results in more ground friction, or drag, on the left wheel causing a turning tendency to the left.
(FAA-H-8083-25)

Question 11

What are the four factors that contribute to torque effect?

Answer 11

Torque reaction of the engine and propeller. Rotation to the right tends to roll or bank the airplane to the left.
Gyroscopic effect of the propeller. If the axis of the propeller is tilted, the resulting force will be exerted 90°ahead of the direction of rotation and in the same direction as the applied force; it is most noticeable on takeoffs in taildraggers when the tail is raised.
Corkscrewing effect of the propeller slipstream. At high propeller speeds and low forward speeds (takeoff) the slipstream strikes the vertical tail surface on the left side pushing the tail to the right and yawing the airplane to the left.
Asymmetrical loading of the propeller. When an airplane is flying with a high angle of attack, the bite of the downward moving propeller blade is greater than the bite of the upward moving blade. This is due ot the downward moving blade meeting the oncoming relative wind at a greater angle of attack than the upward moving blade. Consequently, there is greater thrust on the downward moving right side and the airplane yaws left.
(FAA-H-8083-25)

Question 12

What is “centrifugal force”?

Answer 12

Centrifugal force is the “equal and opposite reaction” of the airplane to the change in direction, and it acts “equal and opposite” to the horizontal component of lift.
(FAA-H-8083-25)

Question 13

What is “load factor”?

Answer 13

It is the actual load supported by the wings divided by the total weight of the plane. Often expressed as a ratio of a given load to the pull of gravity; i.e., “3 Gs.”
(FAA-H-8083-25)

Question 14

For what two reasons is load factor important to pilots?

Answer 14

a. Because of the obviously dangerous overload that it is possible for a pilot to impose on the aircraft structure.
b. Because an increased load factor increases the stalling speed and makes stalls possible at seemingly safe flight speeds
(FAA-H-8083-25)

Question 15

What situations may result in load factors reaching the maximum or being exceeded?

Answer 15

Level Turns - The load factor increase at a terrific rate after a bank has reached 45° or 50°. The load factor in a 60° turn is 2 Gs. the load factor in a 80° turn is 5.76 Gs. The wing must produce lift equal to these load factors if altitude is to be maintained.
Turbulence - Severe vertical gusts can cause a sudden increase in the angle of attack, resulting in large loads which are resisted by the inertia of the airplane.
Speed - The amount of excess load that can be imposed upon the wing depends on how fast the airplane is flying. At speeds below maneuvering speed, the plane will stall before the load factor can become excessive. At speeds above the maneuvering speed, the limit load factor for which an airplane is tested can be exceeded by abrupt or excessive application of the controls or by strong turbulence.
(FAA-H-8083-25)

Question 16

What are the different operational categories for aircraft?

Answer 16

The maximum safe load factors (limit load factors) specified for airplanes in the various categories are as follows:
Normal: +3.8 to -1.52
Utility (mild aerobatics including spins): +4.4 to -1.76
Aerobatic: +6.0 to -3.00
(FAA-H-8083-25)

Question 17

What effect does an increase in load factor have on stall speed?

Answer 17

As load factor increases, stall speed increases. A rule for determining the speed at which a wing will stall is that the stalling speed increases in proportion to the square root of the load factor.
(FAA-H-8083-25)

Question 18

Define the term “maneuvering speed.”

Answer 18

Maneuvering speed is the maximum speed at which abrupt control movement can be applied or at which the airplane could be flown in turbulence without exceeding design load factor limits. When operating below this speed, a damaging positive flight load should not be produced because the airplane should stall before load becomes excessive.
(FAA-H-8083-25)

Question 19

Discuss the effect on maneuvering speed of an increase or decrease in weight.

Answer 19

Maneuvering speed increases with an increase in weight and decreases with a decrease in weight. An aircraft operating at a reduced weight is more vulnerable to rapid accelerations encountered during flight through turbulence or gusts.
(FAA-H-8083-25)

Question 20

What causes an airplane to stall?

Answer 20

The direct cause of every stall is an excessive angle of attack. Each airplane has a particular angle of attack where the airflow separates from the upper surface of the wing and the stall occurs. This critical angle of attack varies from 16° to 20° depending on the airplane’s design, but each airplane has only one specific angle of attack where stall occurs regardless of airspeed, weight, load factor, or density altitude.
(FAA-H-8083-25)

Question 21

What is a “spin”?

Answer 21

A spin in a small airplane or glider is a maneuver in which the airplane or glider descends in a helical path while flying at an angle of attack greater than the critical angle of attack. Spins result from aggravated stalls in either a slip or a skid. If a stall does not occur, a spin cannot occur.
(AC 61-67)

Question 22

What causes a spin?

Answer 22

The primary cause of an inadvertent spin is exceeding the critical angle of attack while applying excessive or insufficient rudder, and to a lesser extent, aileron.
(AC 61-67)

Question 23

When are spins most likely to occur?

Answer 23

A stall/spin is most likely to occur in the following situations:
a. Engine failure during climbout - pilot tries to stretch glide to landing area by increasing back pressure or makes an uncoordinated turn back to departure runway at a relatively low airspeed.
b. Cross-control turn from base to final (slipping or skidding turn) - pilot overshoots final and makes uncoordinated turn at low airspeed.
c. Engine failure on approach to landing - pilot tries to stretch glide to runway by increasing back pressure.
d. Go-around with full nose-up trim - pilot applies power with full flaps and nose-up trim combined with uncoordinated use of rudder.
e. Go-around with improper flap retraction - pilot applies power and retracts flaps rapidly resulting in a rapid sink rate followed by an instinctive increase in back pressure.
(AC 61-67)

Question 24

What procedures should be used to recover fro an inadvertent spin?

Answer 24

a. Close the throttle (if not already accomplished).
b. Neutralize the ailerons.
c. Apply full opposite rudder.
d. Briskly move the elevator control forward to approximately the neutral position.
e. Once the stall is broken the spinning will stop. Neutralize the rudder when the spinning stops.
f. When the rudder is neutralized, gradually apply enough aft elevator pressure to return to level flight.
(AC 61-67)

Question 25

What causes “adverse yaw”?

Answer 25

When turning an airplane (left for example), the downward deflected aileron (right wing) produces more lift. Since the downward deflected aileron (right) produces more lift it also produces more drag. This added drag attempts to pull the airplane’s nose in the direction of the raised wing (right); that is, it tries to turn the airplane in the direction opposite to that desired.
(FAA-H-8083-25)

Question 26

What is “ground effect”?

Answer 26

Ground effect is a condition of improved performance that airplane experiences when it is operating near the ground. The airflow around the wing is restricted by the ground surface; this reduces the wing’s upwash, downwash, and wingtip vortices. In order for ground effect to be of a significant magnitude, the wing must be quite close to the ground.
(FAA-H-8083-25)

Question 27

What major problems can be caused by ground effect?

Answer 27

During landing - at a height of approximately one-tenth of a wing span above the surface, drag may be 40% less than out of ground effect. Any excess speed during landing may result in a significant float distance and the pilot may run out of runway and options at the same time.
During takeoff - due to the reduced drag in ground effect, the aircraft may seem capable of takeoff well below the recommended speed, however, as the airplanes leaves ground effect it may exhibit marginal climb performance or the inability to fly at all.
(FAA-H-8083-25)

Question 28

Define the following:
Empty weight - 
Gross weight - 
Useful load - 
Arm - 
Moment - 
Center of gravity - 
Datum -

Answer 28

Empty weight - The airframe, engines, and all items of operating equipment that have fixed locations and are permanently installed. Includes hydraulic fluid, unusable fuel, and undrainable oil.
Gross weight - The maximum allowable weight of both airplane and its contents.
Useful load - The weight of pilot, copilot, passengers, baggage, usable fuel, and drainable oil.
Arm - The horizontal distance in inches from the reference datum line to the center of gravity of an item.
Moment - The weight of an item multiplied by its arm.
Center of gravity - The point around which an item would balance if it were possible to suspend it at that point.
Datum - An imaginary vertical plane or line from which all measurements of arm are taken. Established by the manufacturer.
(FAA-H-8083-25)

Question 29

What basic equation is used in all weight and balance problems to find the center of gravity location of an airplane and/or its components?

Answer 29

Weight x Arm = Moment

FAA-H-8083-25

Question 30

What performance characteristics will be adversely affected when an aircraft has been overloaded?

Answer 30

Higher takeoff speed.
Longer takeoff run.
Reduced rate and angle of climb.
Lower maximum altitude.
Shorter range.
Reduced cruising speed.
Reduced maneuverability.
Higher stalling speed.
Higher landing speed.
Longer landing roll.
Excessive weight on nosewheel.
(FAA-H-8083-25)

Question 31

What effect does a forward center of gravity have on an aircraft’s flight characteristics?

Answer 31

Higher stall speed - stalling angle of attack is reached at a higher speed due to increased wing loading.
Slower cruise speed - increased drag; greater angle of attack is required to maintain altitude.
More stable - the center of gravity is farther forward from the center of pressure which increases longitudinal stability.
Greater back elevator pressure required - longer takeoff roll; higher approach speeds and problems with landing flare.
(FAA-H-8083-25)

Question 32

What effect does a rearward center of gravity have on an aircraft’s flight characteristics?

Answer 32

Lower stall speed - less wing loading.
Higher cruise speed - reduced drag; smaller angle of attack is required to maintain altitude.
Less stable - stall and spin recovery more difficult; the center of gravity is closer to the center of pressure, causing longitudinal instability.
(FAA-H-8083-25)

Question 33

What are the standard weights assumed for the following when calculating weight and balance problems?

Answer 33

Crew and passengers: 170 lbs each
Gasoline: 6 lbs/U.S. gal
Oil: 7.5 lbs/U.S. gal
Water: 8.35 lbs/U.S.gal
(FAA-H-8083-25)

Question 34

What are some of the main elements of aircraft performance?

Answer 34

a. Takeoff and landing distance
b. Rate of climb
c. Ceiling
d. Payload
e. Range
f. Speed
g. Fuel economy
(FAA-H-8083-25)

Question 35

What factors affect the performance of an aircraft during takeoffs and landings?

Answer 35

a. Air density (density altitude)
b. Surface wind
c. Runway surface
d. Upslope or downslope runway
e. Weight
(FAA-H-8083-25)

Question 36

What effect does wind have on aircraft performance?

Answer 36

Takeoff - a headwind will shorten take off distance and increase the angle of climb, however, a tailwind will decrease performance.
Landing - a headwind will steepen the approach angle and reduce landing distance while a tailwind will reduce performance, decreasing the approach angle and increasing landing distance.
Cruise flight - a headwind will decrease ground speed and increase fuel requirements and a tailwind will increase ground speed and decrease fuel requirements.
(FAA-H-8083-25)

Question 37

How does weight affect takeoff and landing performance?

Answer 37

Increased weight during takeoff results in:
a. Higher liftoff speed
b. Greater mass/slower acceleration
c. Increased retarding force (drag and ground friction)
d. Longer takeoff distance
Increased weight on landing requires greater speed to support the airplane at landing angle of attack resulting in an increased landing distance.
(FAA-H-8083-25)

Question 38

What effect does an increase in density altitude have on takeoff and landing performance?

Answer 38

a. Increased takeoff distance (greater TAS required)
b. Reduced rate of climb (decreased thrust and reduced acceleration)
c. Increased airspeed on approach and landing
d. Increased landing roll distance
(FAA-P-8740-2)

Question 39

Define the term “density altitude.”

Answer 39

Density altitude is pressure altitude corrected for nonstandard temperature. Under standard atmospheric condition, air at each level in the atmosphere has a specific density, and under standard conditions, pressure altitude and density altitude identify the same level. Therefore, density altitude is the vertical distance above sea level in the standard atmosphere at which a given density is found.
(FAA-H-8083-25)

Question 40

How does air density affect aircraft performance?

Answer 40

The density of the air has a direct effect on:
a. Lift produced by the wings
b. Power output of the engine
c. Propeller efficiency
d. Drag forces
(FAA-H-8083-25)

Question 41

What factors affect air density?

Answer 41

Altitude - the higher the altitude, the less dense the air.
Temperature - the warmer the air, the less dense it is.
Humidity - more humid air is less dense.
(FAA-P-8740-2)

Question 42

How does temperature, altitude, and humidity affect density altitude?

Answer 42

Density altitude will increase (low air density) when the following occur:
- High air temperature
- High altitude
- High humidity
Density altitude will decrease (high air density) when the following occur:
- Low air temperature
- Low altitude
- Low humidity
(FAA-P-8740-2)

Question 43

Airplane speeds

Answer 43

VS0 (41 KIAS) - Stall speed in landing configuration.
VS1 (47 KIAS) - Stall speed in clean configuration.
VR (55 KIAS) - Rotation speed.
VX (59 KIAS) - Best angle-of-climb speed.
VY (79 KIAS) - Best rate of climb speed.
VGlide (65 KIAS) - Best glide distance.
VFE (85 KIAS) Maximum flap extension speed.
VA - (80, 89, 97 KIAS @ 1600, 1950, 2300 lbs) - Maneuvering speed, load limit can be imposed.
VNO (128 KIAS) - Normal operating speed.
VNE (160 KIAS) - Never exceed speed.

Question 44

Define the term “pressure altitude”

Answer 44

Pressure altitude is the altitude indicated when the altimeter setting window is adjusted to 29.92. This indicates the altitude above the standard datum plane (29.92 & 15° C) Pressure altitude is used to compute density altitude, true altitude, true airspeed, and performance data.
(FAA-H-8083-3)