Performance and Limitations

Question 1

What are the 4 dynamic forces that act on an airplane during all maneuvers?

Answer 1

Lift, Weight, Thrust and Drag

Question 2

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

Answer 2

Steady-state, straight-and-level, unaccelerated flight.

Question 3

What is an airfoil? State some examples.

Answer 3

A device which gets a useful reaction from air moving over its surface, namely LIFT.
Wings, horizontal tail surfaces, vertical tail surfaces and propellers.

Question 4

What is the “angle of incidence”?

Answer 4

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. It is fixed and cannot be changed by the pilot.

Question 5

What is “relative wind”?

Answer 5

The direction of the airflow with respect to the wing.

Question 6

What is the “angle of attack”?

Answer 6

The angle between the wing chord line and the relative wind.

Question 7

What is “Bernoulli’s Principle”?

Answer 7

The pressure of a fluid (liquid or gas) decreases at points where the speed of the fluid increases.

Question 8

What factors affect both lift and drag (5)?

Answer 8

Shape of the airfoil
Wing area
Angle of attack
Velocity of the air
Air density

Question 9

What is Torque Effect?

Answer 9

Newton’s 3rd law - equal and opposite reactions
As the internal engine parts and prop are revolving in one direction, an equal force is trying to rotate the airplane in the opposite direction. It is greatest when at low airspeed with high power and high angle of attack.

Question 10

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

Answer 10

In flight - acts around the longitudinal axis, tending to make plane roll
On the ground - during takeoff roll, an additional turning moment around the vertical axis is induced by torque reaction. Puts more weight on left main landing gear which results in more ground friction, or drag, on the left tire, causing a further turning moment to the left.

Question 11

What are the 4 factors that contribute to Torque Effect?

Answer 11

1) Torque reaction of engine & prop
2) Gyroscopic effect of the prop (gyroscopic precession) - force is exerted 90 degrees ahead in the direction of rotation.
3) Corkscrew effect of the prop slipstream - high speed rotation of prop results in a corkscrewing rotation to the slipstream as it moves rearward. Strikes vertical tail surfaces during takeoff.
4) Asymmetrical loading of the prop (P-factor) When flying at a high angle-of-attack, bite of downward prop blade is greater than the bite of the upward moving blade. Consequently, greater thrust on downward blade causing yaw to left.

Question 12

What is “Centrifugal Force”?

Answer 12

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.

Question 13

What is “Load Factor”?

Answer 13

Ratio of lift to weight.

Question 14

For what 2 reasons is load factor important to a pilot?

Answer 14

1) It could impose on aircraft structure

2) Increases the stalling speed and makes stalls possible at seemingly safe speeds.

Question 15

What 3 situations may result in load factors reaching the maximum or being exceeded?

Answer 15

1) Level turns as load factor increases with increased bank angle.
2) Severe vertical gusts cause a sudden increase in AOA.
3) Speed -Amount of excess load that can be imposed upon the wing depends on how fast the airplane is flying.

Question 16

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

Answer 16

As load factor increases, stalling speed increases.

Question 17

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

Answer 17

Higher takeoff speed
Longer takeoff and landing rolls
Reduced rate of climb and angle of climb
Lower max altitude
Shorter range
Reduced cruise speed
Reduced maneuverability
Higher stalling speed
Higher landing speed
Excessive weight on the nosewheel

Question 18

What effect does a forward center of gravity have on an aircraft’s flight characteristics? (4)

Answer 18

Higher stall speed
Slower cruise speed
More stable (longitudinal)
Greater back elevator pressure required

Question 19

What effect does a rearward center of gravity have on an aircraft’s flight characteristics? (3)

Answer 19

Lower stall speed (less wing loading)
Higher cruise speed (reduced drag; smaller AOA to maintain alt)
Less stable - stall & spin recovery more difficult; COG closer to center of pressure, causing longitudinal instability.

Question 20

What are some of the main elements of aircraft performance?

Answer 20

Takeoff and Landing distances
Rate of climb
Ceiling
Payload
Range
Speed
Fuel economy
Stability

Question 21

What factors affect the performance of an aircraft during takeoff and landing?

Answer 21

Air density (density altitude)
Surface wind
Runway surface
Upslope/downslope of runway
Weight

Question 22

What effect does an increase in density altitude have on takeoff and landing performance? (4)

Answer 22

Increased takeoff distance/speed
Reduced rate of climb
Increase true airspeed on approach and landing
Increased landing roll distance

Question 23

How does air density affect aircraft performance? (4)

Answer 23

1) Lift produced by the wings
2) Power output of the engine
3) Propeller efficiency
4) Drag forces

Question 24

What factors affect air density? (3)

Answer 24

1) Altitude (higher = less dense)
2) Temperature (warmer = less dense)
3) Humidity (more humid = less dense)

Question 25

How does temperature, altitude and humidity affect density altitude?

Answer 25

Increase (aka “low air density”) - High temp, high altitude or high humidity
Decrease (aka “high air density) - Low temp, low altitude or low humidity