Free ATPL principles of flight 081 questions: 9 with answers
9 principles of flight questions from the ATPL bank of ForAllPilots, with no account and no sign-up. Answer in your head, then open the answer: the right letter and its explanation are under each question. The full bank has 1,335 questions for this subject.
The 9 questions
Question 1 · 081 01 Subsonic aerodynamics
In steady level flight, CL is 0.86 at 180 kt. If speed changes to 190 kt with weight unchanged, the new CL is approximately:
- A0.46
- B0.86
- C1.08
- D0.77
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Answer: D. 0.77
In level flight lift equals weight, so CL is inversely proportional to V². CL2 = 0.86 x (180 / 190)² = 0.86 x 0.897 = about 0.77.
Question 2 · 081 01 Subsonic aerodynamics
Compared with the flap up configuration the maximum angle of attack for the flaps down configuration is
- Alarger.
- Bunchanged.
- Csmaller or larger depending on flap deflection.
- Dsmaller.
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Answer: D. smaller.
Trailing edge flaps increase camber and CLmax, but the flow separates at a lower angle of attack. The critical angle of attack with flaps down is therefore smaller than with flaps up.
Question 3 · 081 01 Subsonic aerodynamics
An aeroplane accelerates from 80 kt to 160 kt at a load factor equal to 1. The induced drag coefficient (i) and the induced drag (ii) alter with the following factors:
- A(i) 1/2 (ii) 1/16
- B(i) 1/4 (ii) 2
- C(i) 4 (ii) 1/2
- D(i) 1/16 (ii) 1/4
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Answer: D. (i) 1/16 (ii) 1/4
In level flight CL is proportional to 1/V², and the induced drag coefficient to CL², so to 1/V⁴. Doubling the speed divides CDi by 16. Induced drag = CDi x ½ρV²S is proportional to 1/V², so it is divided by 4.
Question 4 · 081 02 High-speed aerodynamics
Climbing at a constant Mach Number up to FL 350 the TAS will:
- Aincrease.
- Bdecrease.
- Cremain constant.
- Dfirst increase, then decrease.
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Answer: B. decrease.
Climbing at constant Mach with falling temperature (up to the tropopause), the local speed of sound decreases, so TAS (=M×a) decreases too.
Question 5 · 081 03 stall and upset prevention
Compared with level flight prior to the stall, the lift (1) and drag (2) in the stall change as follows :
- A(1) decreases (2) decreases.
- B(1) decreases (2) increases.
- C(1) increases (2) decreases.
- D(1) increases (2) increases.
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Answer: B. (1) decreases (2) increases.
At the stall the flow separates from the upper surface: lift falls and drag (mostly pressure drag) rises sharply compared with level flight before the stall.
Question 6 · 081 04 Stability
An aircraft is said to be statically stable if, following an increase in angle of attack, the gradients ΔCm/ΔCL or ΔCm/Δα are:
- Anegative
- Bpositive
- Czero
- Dequal to Cm0
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Answer: A. negative
An aeroplane is statically stable in pitch if an increase in angle of attack produces a nose-down pitching moment, which opposes the disturbance. This means the slope dCm/dCL (or dCm/dα) is negative.
Question 7 · 081 06 Limitations
VMO :
- Ais equal to the design speed for maximum gust intensity.
- Bshould be chosen in between VC and VD
- Cshould be not greater than VC.
- Dis the calibrated airspeed at which MMO is reached at 35 000 ft.
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Answer: C. should be not greater than VC.
Under CS 25.1505, the maximum operating limit speed VMO may not exceed the design cruising speed VC, and must be sufficiently below VD.
Question 8 · 081 06 Limitations
An aeroplane has VS1g=130 kt and a positive limit load factor of 2.5g. The approximate design manoeuvring speed VA is:
- A144 kt
- B130 kt
- C268 kt
- D206 kt
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Answer: D. 206 kt
The design manoeuvring speed is about VS x square root of the limit load factor: 130 x square root of 2.5 = 130 x 1.58 = about 206 kt.
Question 9 · 081 08 Flight mechanics
An aeroplane in a coordinated turn at TAS 170 kt and 20° bank angle has an approximate rate of turn of:
- A3.28 °/sec
- B3.34 °/sec
- C1.4 °/sec
- D2.34 °/sec
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Answer: D. 2.34 °/sec
Rate of turn (°/s) = 1,091 x tan bank / TAS (kt) = 1,091 x tan 20° / 170 = 1,091 x 0.364 / 170 = about 2.34°/s.
Each answer was checked again before publication; like every explanation on the site, these may contain errors. Some explanations were rewritten for this page, sometimes with the help of an AI. Spotted a mistake? Write to us at contact@forallpilots.com.
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