Stalling, spinning, stability, control Flashcards
A primary reason for designing a wing with washout is to -
[a] reduce induced drag at cruising speed.
[b] ensure that the wing tip will not stall before the wing root.
[c] improve aileron effectiveness throughout the speed range.
[d] increase the rate at which the aircraft rolls.
B
There are two main reasons for washout. By reducing the angle of attack at the wing tip induced drag is reduced, but that effect is most noticeable at low speed. It is insignificant at cruising speed, so [a] is not correct. The other reason for washout is to ensure that during the progression of the stall, the wing tip is the last section of the wing to stall.
The dihedral angle on a high wing aircraft is usually less than that on a low wing design because the high wing
design has -
[a] stronger lateral stability.
[b] stronger longitudinal stability.
[c] weaker lateral stability.
[d] weaker longitudinal stability.
A
The high wing design features the ‘pendulum effect’ which gives the aircraft natural lateral stability because the weight is below the lift. Aircraft with this design feature need little else to enhance stability in roll. Some high wing aircraft have no dihedral at all e.g. the Cessna 152. Some even have slight anhedral to prevent the lateral stability from becoming excessive.
anhedral: downward inclination of an aircraft’s wing
If no control inputs are made by the pilot, an aircraft which has rolled to the left from the level attitude will have
a natural tendency to -
[a] yaw to the right.
[b] pitch the nose down.
[c] pitch the nose up.
[d] yaw to the left.
D
After the roll, the aircraft sideslips to the left causing the directional stability to induce a yaw in the direction of the slip.
Spiral instability is a result of an interaction between -
[a] rolling and yawing.
[b] rolling and pitching.
[c] yawing and pitching.
[d] low speed and high speed
A
During the yaw the outside wing travels faster than the inside wing, generating more lift. This produces a further roll which causes the slip to continue inducing a further yaw and so on.
Select the combination that would increase the tendency for an aircraft to spiral dive -
[a] strong lateral stability and weak directional stability.
[b] weak lateral stability and strong longitudinal stability.
[c] weak lateral stability and strong directional stability.
[d] strong lateral stability and strong directional stability.
C
After an initial roll, the weak lateral stability attempts to return the wings to level attitude but this effect is overcome by the strong yaw which results from the strong directional stability. As the outside wing accelerates it produces extra lift which makes the roll continue in spite of the lateral stability’s feeble attempt to correct it. A spiral dive results.
Longitudinal dihedral enhances stability in pitch by providing an angle of incidence of the -
[a] tailplane which is greater than that of the mainplane.
[b] tailplane which is less than that of the mainplane.
[c] tailplane which is the same as that of the mainplane.
[d] left wing which is the same as that of the right wing.
B
The lower incidence of the tailplane ensures that for a given angle of attack change, the tailplane increases its lift by a greater proportion than the mainplanes. This ensures that the nose will eventually pitch down after an increase in angle of attack.
Compared to the upper wing, the lower wing of an aircraft in a spin is experiencing -
[a] more lift and more drag.
[b] less lift and less drag.
[c] more lift and less drag.
[d] less lift and more drag.
D
After the stall any increase in angle of attack will produce less lift. The dropping wing will always suffer an increase in angle of attack and so experience less lift. No such thing happens to drag however. Drag which has been increasing up to the stall, simply goes on increasing as angle of attack increases.
A device which encourages the airflow to separate from a wing surface during stall progression is a -
[a] slat. [b] flap.
[c] stall strip. [d] wing fence.
C
When a stall occurs it is desirable that the separation progresses from the root to the tip. If for any reason the wing root or centre section tends to ‘hang on’ as the stall progresses towards the tip, a stall strip is used to ‘trip’ the airflow and encourage it to separate as it should.
For a given angle of attack and power setting, an aircraft leaving ground effect will
[a] experience an increase in lift [b] experience an increase in induced drag
[c] experience an increase in IAS [d] experience an increase in rate of climb
B
The vortex formation is inhibited by the proximity of the ground. As the aircraft leaves the ground effect region [about one wing span], the induced drag increases.
If the nose of an aircraft is suddenly raised in level flight, the angle of attack increases because
[a] the relative airflow changes direction
[b] inertia prevents a change in the flight path
[c] there is a corresponding change in the flight path
[d] the aircraft begins to climb
B
The aircraft will always respond to elevator input by rotating about its lateral axis.
However the flight path does not change immediately because of inertia.
Which of the following indications would positively establish that an aircraft is in a spin and not a spiral dive?
[a] low nose attitude
[b] rapid rate of turn
[c] indicated air speed low and almost unchanging
[d] steadily increasing indicated air speed
C
When a spin develops, the IAS remains at a low value. In a spiral dive, the IAS is high and rapidly increasing.
Which of the following applies to an aircraft which stalls during a sudden pull out from a dive?
[a] the stalling speed and stalling angle will both increase
[b] the stalling speed will increase while the stalling angle will remain the same
[c] the stalling speed will increase while the stalling angle will decrease
[d] the stalling speed will remain the same while the stalling angle will increase
B
An aerofoil stalls at a certain angle, not at a certain speed. The nose rises in response to elevator command, but the flight path remains the same due to inertia. The stalling angle is reached at a higher IAS.
Which of the following combination of factors would cause a change in the indicated stalling speed of an
aeroplane?
[a] power and weight [b] altitude and load factor
[c] turbulence and air density [d] air density and wing loading
A
Anything that changes the lift that the wings must produce will change the stalling IAS.
Density and altitude cause the stall to occur at a higher TAS but the same IAS.
What effect will the formation of ice on the leading edges of the wings of an aircraft during flight have on the
stalling characteristics of the aircraft?
[a] the stalling angle will be increased
[b] the stall will occur at a lower indicated air speed
[c] both the stalling angle and the stalling indicated air speed will be increased
[d] the stalling indicated air speed will increase and the stalling angle will decrease
D
Ice changes the aerodynamic shape of the wings allowing flow reversal and separation to occur at a lower angle of attack. Because the angle of attack is lower, the IAS must be higher.
For an aircraft to enter a spin
[a] it must first be stalled
[b] it must be loaded outside the aft limit of the centre of gravity range
[c] it must be banked in the direction of the spin
[d] the pilot must apply rudder in the direction of the spin
A
A spin requires that lift decrease and drag increase when angle of attack is increased. This can only happen after the stall.
