POF Q29 - Longitudinal Stability Flashcards
If the airspeed increases and decreases during longitudinal phugoid oscillations, the aircraft:
Select one:
a.can be easily controlled by the pilot.
b.is constantly changing AoA making it difficult to reduce the magnitude of the oscillations.
c.Is displaying lateral dynamic instability.
d.will display poor trimming qualities.
a.can be easily controlled by the pilot.
Which statement is correct? 1) Stick force per g is independent of altitude. 2) Stick force per g increases when the centre of gravity moves forward.
Select one:
a.1) is incorrect; 2) is correct.
b.1) is correct; 2) is correct.
c.1) is correct; 2) is incorrect.
d.1) is incorrect; 2) is incorrect.
a.1) is incorrect; 2) is correct.
In a twin engine jet aeroplane (engines mounted below the low wings) the thrust is suddenly increased. Which elevator deflection will be required to maintain the pitching moment zero ?
Select one:
a.It depends on the position of the centre of gravity.
b.Up.
c.Down.
d.No elevator movement will required because the thrust line of the engines remains unchanged.
c.Down.
During a phugoid the speed:
Select one:
a.varies significantly, whereas during a short period oscillation it does not (remains approximately constant).
b.remains approximately constant, as it does during a short period oscillation.
c.remains approximately constant, whereas during a short period oscillation it varies significantly.
d.varies significantly, as it does during a short period oscillation.
a.varies significantly, whereas during a short period oscillation it does not (remains approximately constant).
The effect of the wing downwash on the static longitudinal stability of an aeroplane is:
Select one:
a.negative.
b.positive.
c.negligible.
d.smallest at high values of the lift coefficient.
a.negative.
The most forward CG location may be limited by: 1) Insufficient flare capability. 2) Excessive in-flight manoeuvrability. 3) Insufficient in-flight manoeuvrability. The combination that regroups all of the correct statements is:
Select one:
a.1, 3
b.2
c.3
d.1, 2
a.1, 3
The neutral point of an aeroplane is the point where:
Select one:
a.assuming no flow separation, the pitching moment coefficient does not change with varying angle of attack.
b.the aeroplane becomes longitudinally unstable when the CG is moved beyond it in an aft direction.
c.the boundary layer changes from laminar to turbulent.
d.the velocity of the relative airflow is reduced to zero.
b.the aeroplane becomes longitudinally unstable when the CG is moved beyond it in an aft direction.
If an airplane exhibits poor longitudinal stability in flight, what can be done to the design of the aircraft to increase the stability?
Select one:
a.Decrease the range of movement of the elevator.
b.Install a yaw damper.
c.Reduce in keel surface area.
d.Increase the horizontal stabilizer surface area.
d.Increase the horizontal stabilizer surface area.
If a stick force of 20 lbs is required to pull 4g from the position of trim, the stick force gradient is:
Select one:
a.6.7 lbs/g
b.20 lbs/g
c.5 lbs/g
d.60 lbs/g
a.6.7 lbs/g
Considering the CM - 𝛼a graph below, complete the following sentences.
1.The red line represents [a longitudinally unstable aircraft]
2.The blue line represents [a longitudinally neutral aircraft]
- The grey line represents [a longitudinally stable aircraft]
The pitching moment is much greater at higher IAS because
a.of the forward movement of the CG
b.dynamic pressure is proportional to V2
c.CM being proportional to V2
d.of the movement of the CP
b.dynamic pressure is proportional to V2
designing an aircraft with a low stick force per g can be useful to relieve stress on the pilot. However, what is the danger of creating an extremely low stick force per g?
a.the aircraft becomes too stable.
b.the aircraft becomes too hard to flare.
c.There is no feel in the cockpit for the pilot.
d.It becomes very easy to overstress the aircraft.
d.It becomes very easy to overstress the aircraft.
An aircraft that has its CG located ahead of the AC will create a [ ] pitching moment. The further forward the CG the [ ] the moment with the tailplane, [ ] tailplane effectiveness. However, if the CG is too far forward the aircraft can become too [ ] .
[nose down] [greater] [increasing] [stable]
Why in aviation is stick position stability desirable?
a.so the of force exerted by the pilot on the control column is proportional to the load factor present.
b.If there is an increase in speed the aircraft creates an automatic pitch down movement.
c.to increase the longitudinal stability of the aircraft
d.so control column movements move the aircraft the way the pilot is expecting it to.
d.so control column movements move the aircraft the way the pilot is expecting it to.
