Self-test

Self-test Subject 080 Principles of Flight

This self-test covers key concepts of Subject 080. Answers at the end.

Properties of air

1. Which two pressure types are distinguished at the aircraft?
2. What does the pitot tube measure?
3. Up to what Mach number does Bernoulli still hold?
4. What does the continuity equation mean in incompressible form?

Airfoil

5. What is the angle of attack (α)?
6. What do the NACA 4-digit numbers mean? Example NACA 2412.
7. Lift equation: L = ?
8. What is CL_max for a typical GA airfoil?
9. What is the shape of the CL-α curve in the stall region?

Wing

10. Aspect ratio: definition and typical value for C172.
11. Which wing shape has minimum induced drag?
12. What is washout? Why used?

High-lift devices

13. Which flap type has the greatest CL_max effect?
14. What does Vfe mean?
15. Spoilers — what do they do?

Stability and controls

16. Define static vs dynamic stability.
17. What are the three axes and their controls?
18. What is adverse yaw? How countered?
19. What is the phugoid?
20. PARE recovery for spin: what do the 4 letters mean?

Turns

21. Load factor n at 60° bank?
22. Vs(60° bank) for an aircraft with Vs = 50 KIAS?
23. Standard rate turn = how many degrees per second?
24. Bank angle for standard rate at 100 KIAS (rule of thumb)?

Va and propeller

25. What does Va mean?
26. C172 (Normal Category) n_max = ?
27. What are the 4 propeller effects?
28. P-factor: in which direction is the yaw?

Answers

1. Static pressure (isotropic, at rest) and dynamic pressure (q = ½ρv²).
2. Total pressure pt = p + q (Bernoulli).
3. M < 0.3 for incompressible assumption.
4. A · v = constant along the flow channel.
5. Angle between chord line and relative wind.
6. 1st digit = % camber, 2nd digit = location of max camber (×10%), 3rd+4th = thickness %. NACA 2412: 2 % camber at 40 % chord, 12 % thickness.
7. L = ½ · ρ · V² · S · CL.
8. CL_max typically 1.2–1.8 without flaps; up to 2.5 with flaps.
9. CL drops abruptly after α_stall.
10. AR = b²/S. C172 ≈ 7.4.
11. Elliptical (Prandtl, ideal minimum induced drag).
12. Washout = tip α lower than root α. Used so root stalls first → ailerons remain effective → benign stall.
13. Fowler flap with CL_max +0.9 to +1.0.
14. Vfe = max speed with full flaps extended.
15. Reduce lift + increase drag (for descent, roll control, landing brake).
16. Static = initial tendency to return; dynamic = time history of response.
17. Longitudinal axis → roll → aileron; lateral axis → pitch → elevator; vertical axis → yaw → rudder.
18. Yaw opposite to roll direction due to unequal drag from ailerons. Counter: differential/Frise ailerons, coordinated rudder input.
19. Long, damped pitch-altitude oscillation (period 30-90 s).
20. Power idle, Ailerons neutral, Rudder full opposite, Elevator forward.
21. n = 1/cos(60°) = 2.0 (load factor doubled).
22. Vs(60° bank) = Vs · √2 = 50 · 1.41 ≈ 71 KIAS.
23. 3°/s = 360°/2 min.
24. Rule of thumb φ ≈ V/10 + 7 → at 100 kt: φ ≈ 17°.
25. Maximum speed at which a full control deflection cannot overload. Va = √(n_max) · Vs.
26. n_max = +3.8 g (Normal Category per CS-23).
27. Torque effect, spiral slipstream, P-factor, gyroscopic precession.
28. Yaw to the left (for US/EU standard propellers with CW rotation).