DGCA Technical General: Stability & Control Questions
172 exam-style Stability & Control questions for the DGCA Technical General paper (CPL · ATPL · PPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
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Q1
What is short period mode?
- A Pilot induced oscillation.
- B Oscillation about the lateral axis.
- C Oscillation about the longitudinal axis.
- D Oscillation about the normal axis.
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Correct answer: B. Oscillation about the lateral axis.
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Q2
468.Dynamic stability is ___________at high altitude due to_____________aerodynamic damping
- A Increased, Reduced
- B Reduced; Reduced
- C Reduced, Increased
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Correct answer: B. Reduced; Reduced
Dynamic stability is reduced at high altitude because the lower air density reduces aerodynamic damping. Disturbance-induced oscillations therefore die away more slowly than they would in the denser air at low level, even though static stability is essentially unchanged.
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Q3
What is phugoid motion?
- A Short period longitudinal oscillations.
- B Long period longitudinal oscillations.
- C Long period lateral oscillations.
- D Long period yawing oscillations.
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Correct answer: B. Long period longitudinal oscillations.
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Q4
Choose the correct statement: 1. AFT CG limit is set to ensure a minimum degree static longitudinal stability 2.. FWD CG limit is set to ensure a minimum degree of controllability under the worst circumstances
- A 1 is correct
- B 2 is correct
- C Both 1 & 2 are correct
- D Both 1 & 2 are incorrect
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Correct answer: C. Both 1 & 2 are correct
Both statements are correct: the aft centre of gravity limit is set so that a minimum acceptable degree of static longitudinal stability is always retained, while the forward limit guarantees sufficient elevator authority to control, rotate and flare the aircraft under the most demanding conditions.
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Q5
Dynamic stability is ___________at high altitude due to _____________aerodynamic damping
- A Increased, reduced
- B Reduced, reduced
- C Reduced, increased
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Correct answer: B. Reduced, reduced
The thin air at high altitude produces much weaker aerodynamic damping forces for a given disturbance, so oscillations die away more slowly and dynamic stability is reduced.
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Q6
Where is the aft C of G limit of an aircraft?
- A Behind the neutral point.
- B Ahead of the neutral point.
- C On the neutral point.
- D On the manoeuvre point.
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Correct answer: B. Ahead of the neutral point.
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Q7
At what position on an aircraft must the C of G be to make it neutrally longitudinally stable during pull up manoeuvres?
- A The neutral point.
- B The transition point.
- C The aerodynamic centre.
- D The manoeuvre point.
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Correct answer: D. The manoeuvre point.
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Q8
Which of the following contribute to lateral stability?
- A Anhedral, sweepback, high wing, high fin.
- B Dihedral, sweepback, low wing, high fin.
- C Anhedral, aspect ratio, high wing, ventral fin.
- D Dihedral, sweepback, high wing, high fin.
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Correct answer: D. Dihedral, sweepback, high wing, high fin.
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Q9
472.Positive static stability is
- A If an A/C has a tendency to continue in the direction of disturbance
- B If an A/C is subject to a disturbance and has neither the tendency to return nor the continue in the displacement direction
- C If an A/C is disturbed from equilibrium and has the tendency to return to equilibrium
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Correct answer: C. If an A/C is disturbed from equilibrium and has the tendency to return to equilibrium
Positive static stability means that when disturbed from equilibrium the aircraft generates forces and moments that initially tend to return it to its original condition; continuing in the direction of the disturbance would be negative stability, and doing neither is neutral.
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Q10
What purpose is served by a dorsal fin at high sideslip angles?
- A Decreases effectiveness of the fin in order to reduce lateral instability.
- B Decreases effectiveness of the fin in order to reduce Dutch roll.
- C Increases effectiveness of the fin by increasing its area.
- D lncreases effectiveness of the fin by reducing its aspect ratio.
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Correct answer: D. lncreases effectiveness of the fin by reducing its aspect ratio.
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Q11
416.The dihedral construction of an aircraft wing causes
- A directional stability about the lateral axis
- B Lateral stability about the longitudinal axis
- C Longitudinal stability about the lateral axis
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Correct answer: B. Lateral stability about the longitudinal axis
Dihedral provides lateral stability, which acts about the longitudinal axis: in a sideslip the lower wing meets the relative airflow at a greater angle of attack, producing a rolling moment that restores the wings to level.
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Q12
433.The disadvantage of "conventional" elevator and trim tabs is that the aircraft
- A Nose up pitch authority reduces with forward CG movement
- B Nose up pitch authority increase with forward CG movement
- C There is no effect of CG movement to pitch
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Correct answer: A. Nose up pitch authority reduces with forward CG movement
With a conventional elevator and trim-tab arrangement, moving the CG forward increases the nose-down moment the elevator must overcome, so the available nose-up pitch authority, needed most in the landing flare, reduces as the CG moves forward.
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