Aerodynamics/ CG

Question 1

What is Stability?

Answer 1

Stability is an aircraft’s ability to maintain/Return to its original flight path.

Question 2

What are the types of static stability?

Answer 2

Positive
Neutral
Negative

Question 3

What is static stability?

Answer 3

A aircraft’s initial tendencies

Question 4

What is dynamic stability?

Answer 4

A aircraft’s tendencies over time

Question 5

What are the types of dynamic Stability?

Answer 5

Positive
Neutral
Negative

Question 6

What is Positive Static Stability?

Answer 6

The initial tendency to return to an undisturbed state after a disturbance.

Question 7

What is Neutral Static Stability?

Answer 7

Initial tendency to stay in new attitude when disturbed.

Question 8

What is negative static stability?

Answer 8

Aircraft’s initial tendency to diverge further when disturbed.

Question 9

What is positive dynamic stability?

Answer 9

The tendency to dampen towards its original position once disturbed.

Question 10

What is neutral dynamic stability?

Answer 10

The oscillations continue in the same motions once disturbed, neither increasing or decreasing.

Question 11

What is negative neutral stability.

Answer 11

The oscillations continue in a worse manner once disturbed?

Question 12

What are the 4 types of left turning tendencies?

Answer 12

•P-factor
•Torque
•Spiraling Slipstream
•Gyroscopic Precession

Question 13

What is P-Factor?

Answer 13

Downward blade is at a higher angle of attack generating more lift on that side. More noticeable during slow climbs at high AOA.

Question 14

What is the Torque Turning tendency?

Answer 14

For every action there is an equal and opposite reaction- prop moves clockwise airplane wants to move counter clockwise.

Question 15

What is the Spiraling Slipstream turning tendency?

Answer 15

Air corkscrews around the airplane pushing on the rudder, pushing aircraft to the left.

Question 16

What is the Gyroscopic Procession turning tendency?

Answer 16

Any force applied to a spinning object will be felt 90 degrees ahead of the turn in the direction it’s spinning.
•when pushing the nose down the tendency is to turn left
•when pulling nose up tendency is to turn right

Question 17

What is Va?

Answer 17

Va is the planes maneuvering speed?

Question 18

Does Va change with weight? If so why?

Answer 18

Yes Va changes with weight because at the same speed as a lighter aircraft a heavier aircraft needs to fly at a higher angle of attack to produce enough lift to counter the aircraft’s weight in level flight.

Question 19

What is the weight shift computation formula?

Answer 19

Weight of cargo moved/ airplane weight= distance CG moved/distance between arm locations(stations)

(Cross multiply)

Question 20

What is load factor?

Answer 20

It is the ratio of the lift provided by the lifting surfaces divided by the total weight of the aircraft.

Question 21

How does Load Factor change?

Answer 21

Increases as you increase bank(Gs) because it increases the “load”
60 degrees is 2G so 2000 pounds is now 4000 pounds.

Question 22

What happens when load factor increases?

Answer 22

The higher the load factor the higher the stall speed.

Question 23

What is CG?

Answer 23

Center of Gravity- The point about which an aircraft would balance if it was possible to suspend it on that point.

Question 24

How do you get CG?

Answer 24

Total Aircraft weight decided by Total Moment.

Question 25

How does an aft CG effect a planes flying characteristics?

Answer 25

•Less stable •More performance •less tail trim drag •decreases stall speed The arm between your CG and tail downforces decreases thus making it more unstable.

Question 26

How does a forward CG affect flying characteristics?

Answer 26

•More tail down force •Increased AOA= Increased Drag •More stable because distance between CG and Tail is greater. •Stall speed increases

Question 27

What happens to the CG as fuel burns?

Answer 27

CG can shift so Calculate both takeoff and landing CG.

Question 28

What is a stall?

Answer 28

When an aircraft’s wings stop producing lift due to an excessive AOA?

Question 29

What is the Critical Angle of Attack?

Answer 29

It is the difference between the relative wind and the cord line.

Question 30

What is Relative wind and Chord line?

Answer 30

•Relative wind- direction of the wind relative to the airfoil. •Chord Line- Imaginary Straight line going through the leading edge to the trailing edge of a wing.

Question 31

What are the Different types of Stalls? (7)

Answer 31

•Power-On stall •Power-Off stall •Accelerated Stall •Secondary stall •Cross-Control stall •Elevator Trim Stall •Tail Stall

Question 32

What is a Power-On stall?

Answer 32

Stall in Takeoff and Climb configurations.

Question 33

What is a Power-Off stall?

Answer 33

Stall in landing and approach configuration.

Question 34

What is an Accelerated Stall?

Answer 34

Caused by abrupt or excessive control movements, usually involve a high load factor.

Question 35

What is a Secondary Stall?

Answer 35

Usually occurs during an attempt to get out of a stall either by increasing AOA to fast or soon, or by not decreasing angle of attack enough.

Question 36

What is a cross controlled stall?

Answer 36

This occurs when flight controls are crossed and a lot of back pressure or slow speed is applied, usually happens on base to final turn. Excessive inside rudder is used to tighten the turn plus back pressure equals a cross controlled stall.

Question 37

What is an Elevator Trim stall?

Answer 37

Most likely to occur during a go around, when trim is set for landing. When full power is applied a lot of positive pressure must be applied or the aircraft will want to keep pitching up. Usually a lot of left turning tendency as well and can lead to uncoordinated flight/ a spin.

Question 38

What is a tail stall?

Answer 38

Usually more common in tail daggers. Tail stalls before the wings dropping the nose a lot. To recover add lots of back pressure unlike a regular stall.

Question 39

What is a spin?

Answer 39

Plane must be stalled first, when one wing is stalled less than the other.

Question 40

What are the phases of a spin? (4)

Answer 40

Entry-stalls Incipient- time from rotation starts to a fully developed spin Fully developed spin-when one turn to the next is stabilized Recovery- begins when anti-spin forces overcome the pro-spin forces.

Question 41

What are the different names for high speeds?

Answer 41

Subsonic Transonic Supersonic Hypersonic

Question 42

Subsonic flight speed

Answer 42

Mach below .75

Question 43

Transonic flight speed

Answer 43

Mach from .75 to 1.20

Question 44

Supersonic Flight speed

Answer 44

Mach 1.20 to 5.00

Question 45

Hypersonic flight speed

Answer 45

Mach above 5.00

Question 46

What is critical Mach number?

Answer 46

Speed of an aircraft in which airflow over any part of the aircraft or structure first reaches (but does not exceed) Mach 1.0

Question 47

What is Induced drag VS parasite Drag?

Answer 47

Induced Drag- by product of lift being created by the wings. Parasite Drag-increases with speed, square of the airspeed.

Question 48

Different types of Parasite Drag?

Answer 48

Form drag- based on the shape of the airplane and how well it is streamlined. Interference drag- airflow around one part of the airplane interacts with the airflow around an adjacent part. Skin friction Drag- Air molecules giving up some of there energy as they contact the skin, smoother the skin= less drag.