DGCA POF 10. Stability - Pilotexam.in

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Q1. An aeroplane which is inherently stable will:

require less effort to control.

be difficult to stall.

not spin.

have a built-in tendency to return to its original state following the removal of any disturbing force.

Ans: – have a built-in tendency to return to its original state following the removal of any disturbing force.

Q2. After a disturbance in pitch an aircraft oscillates in pitch with increasing amplitude. It is:

statically and dynamically unstable.

statically stable but dynamically unstable.

statically unstable but dynamically stable.

statically and dynamically stable.

Ans: – statically stable but dynamically unstable.

Q3. Longitudinal stability is given by:

the fin.

the wing dihedral.

the horizontal tailplane.

the ailerons.

Ans: – the horizontal tailplane.

Q4. An aircraft is constructed with dihedral to provide:

lateral stability about the longitudinal axis.

longitudinal stability about the lateral axis.

lateral stability about the normal axis.

directional stability about the normal axis.

Ans: – lateral stability about the longitudinal axis.

Q5. Lateral stability is reduced by increasing:

anhedral.

dihedral.

sweepback.

fuselage and fin area.

Ans: – anhedral.

Q6. If the wing AC is forward of the CG:

changes in lift produce a wing pitching moment which acts to reduce the change of lift.

changes in lift produce a wing pitching moment which acts to increase the change of lift.

changes in lift give no change in wing pitching moment.

when the aircraft sideslips the CG causes the nose to turn into the sideslip thus applying a restoring moment.

Ans: – changes in lift produce a wing pitching moment which acts to increase the change of lift.

Q7. The longitudinal static stability of an aircraft:

is increased by the effects of wing downwash.

is reduced by the effects of wing downwash.

is not affected by wing downwash.

is reduced for nose-up displacements, but increased for nose-down displacements by the effects of wing downwash.

Ans: – is increased by the effects of wing downwash.

Q8. To ensure some degree of longitudinal stability in flight, the position of the CG:

must always coincide with the AC.

must be forward of the Neutral Point.

must be aft of the Neutral Point.

must not be forward of the aft CG limit.

Ans: – must be forward of the Neutral Point.

Q9. When the CG is close to the forward limit:

very small forces are required on the control column to produce pitch.

longitudinal stability is reduced.

very high stick forces are required to pitch because the aircraft is very stable.

stick forces are the same as for an aft CG.

Ans: – very high stick forces are required to pitch because the aircraft is very stable.

Q10. The static margin is equal to the distance between:

the CG and the AC.

the AC and the neutral point.

the CG and the neutral point.

the CG and the CG datum point.

Ans: – the CG and the neutral point.

Q11. If a disturbing force causes the aircraft to roll:

wing dihedral will cause a rolling moment which reduces the sideslip.

the fin will cause a rolling moment which reduces the sideslip.

dihedral will cause a yawing moment which reduces the sideslip.

dihedral will cause a nose-up pitching moment.

Ans: – wing dihedral will cause a rolling moment which reduces the sideslip.

Q12. With flaps lowered, lateral stability:

will be increased because of the effective increase of dihedral.

will be increased because of increased lift.

will be reduced because the centre of lift of each semi-span is closer to the wing root.

will not be affected.

Ans: – will be reduced because the centre of lift of each semi-span is closer to the wing root.

Q13. Dihedral gives a stabilizing rolling moment by causing an increase in lift:

on the up-going wing when the aircraft rolls.

on the down-going wing when the aircraft rolls.

on the lower wing if the aircraft is sideslipping.

on the lower wing whenever the aircraft is in a banked attitude.

Ans: – on the lower wing if the aircraft is sideslipping.

Q14. A high wing configuration with no dihedral, compared to a low wing configuration with no dihedral, will provide:

greater longitudinal stability.

the same degree of longitudinal stability as any other configuration because dihedral gives longitudinal stability.

less lateral stability than a low wing configuration.

greater lateral stability due to the airflow pattern around the fuselage when the aircraft is sideslipping increasing the effective angle of attack of the lower wing.

Ans: – greater lateral stability due to the airflow pattern around the fuselage when the aircraft is sideslipping increasing the effective angle of attack of the lower wing.

Q15. At a constant IAS, what effect will increasing altitude have on damping in roll?

It remains the same.

It increases because the TAS increases.

It decreases because the ailerons are less effective.

It decreases because the density decreases.

Ans: – It decreases because the density decreases.

Q16. Sweepback of the wings will:

not affect lateral stability.

decrease lateral stability.

increases lateral stability at high speeds only.

increases lateral stability at all speeds.

Ans: – increases lateral stability at all speeds.

Q17. At low forward speed:

increased downwash from the wing will cause the elevators to be more responsive.

due to the increased angle of attack of the wing the air will flow faster over the wing giving improved aileron control.

a large sideslip angle could cause the fin to stall.

a swept-back wing will give an increased degree of longitudinal stability.

Ans: – a large sideslip angle could cause the fin to stall.

Q18. Following a lateral disturbance, an aircraft with Dutch roll instability will:

go into a spiral dive.

develop simultaneous oscillations in roll and yaw.

develop oscillations in pitch.

develop an unchecked roll.

Ans: – develop simultaneous oscillations in roll and yaw.

Q19. To correct Dutch roll on an aircraft with no automatic protection system:

use roll inputs.

use yaw inputs.

move the CG.

reduce speed below $M_{MO}$

Ans: – use roll inputs.

Q20. A yaw damper:

increases rudder effectiveness.

must be disengaged before making a turn.

augments stability.

increases the rate of yaw.

Ans: – augments stability.

Q21. A wing which is inclined downwards from root to tip is said to have:

wash out.

taper.

sweep.

anhedral.

Ans: – anhedral.

Q22. The lateral axis of an aircraft is a line which:

passes through the wing tips.

passes through the centre of pressure, at right angles to the direction of the airflow.

passes through the quarter chord point of the wing root, at right angles to the longitudinal axis.

passes through the centre of gravity, parallel to a line through the wing tips.

Ans: – passes through the centre of gravity, parallel to a line through the wing tips.

Q23. Loading an aircraft so that the CG exceeds the aft limits could result in:

loss of longitudinal stability, and the nose to pitch up at slow speeds.

excessive upward force on the tail, and the nose to pitch down.

excessive load factor in turns.

high stick forces.

Ans: – loss of longitudinal stability, and the nose to pitch up at slow speeds.

Q24. The tendency of an aircraft to suffer from Dutch roll instability can be reduced:

by sweeping the wings.

by giving the wings anhedral.

by reducing the size of the fin.

by longitudinal dihedral.

Ans: – by giving the wings anhedral.

Q25. What determines the longitudinal static stability of an aeroplane?

The relationship of thrust and lift to weight and drag.

The effectiveness of the horizontal stabilizer, rudder, and rudder trim tab.

The location of the CG with respect to the AC.

the size of the pitching moment which can be generated by the elevator.

Ans: – The location of the CG with respect to the AC.

Q26. Dihedral angle is:

the angle between the main plane and the longitudinal axis.

the angle measured between the main plane and the normal axis.

the angle between the quarter chord line and the horizontal datum.

the upward and outward inclination of the main planes to the horizontal datum.

Ans: – the upward and outward inclination of the main planes to the horizontal datum.

Q27. Stability around the normal axis:

is increased if the keel surface behind the CG is increased.

is given by the lateral dihedral.

depends on the longitudinal dihedral.

is greater if the wing has no sweepback.

Ans: – is increased if the keel surface behind the CG is increased.

Q28. If the Centre of Gravity of an aircraft is found to be within limits for take-off:

the C of G will be within limits for landing.

the C of G for landing must be checked, allowing for fuel consumed.

the C of G will not change during the flight.

the flight crew can adjust the CG during flight to keep it within acceptable limits for landing.

Ans: – the C of G for landing must be checked, allowing for fuel consumed.

Q29. The ailerons are deployed and returned to neutral when the aircraft has attained a small angle of bank. If the aircraft then returns to a wings-level attitude without further control movement it is:

neutrally stable.

statically and dynamically stable.

statically stable, dynamically neutral.

statically stable.

Ans: – statically and dynamically stable.

Q30. The property which tends to decreases rate of displacement about any axis, but only while displacement is taking place, is known as:

stability.

controllability.

aerodynamic damping.

manoeuvrability.

Ans: – aerodynamic damping.

Q31. If an aircraft is loaded such that the stick force required to change the speed is zero:

the CG is on the neutral point.

the CG is behind the neutral point.

the CG is on the manoeuvre point.

the CG is on the forward CG limit.

Ans: – the CG is on the neutral point.

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