POF Q11 - Stalling Part 1

Question 1

Where on the surface of a typical aerofoil will flow separation normally start at high angles of attack?

a.upper side trailing edge

b.lower side leading edge

c.upper side leading edge

d.lower side trailing edge

Answer 1

a.upper side trailing edge

Question 2

On a swept wing aeroplane at low airspeed, the ‘pitch up’ phenomenon:

a.is caused by boundary layer fences mounted on the wings

b.never occurs, since a swept wing is a ‘remedy’ to pitch up

c.is caused by wingtip stall

d.is caused by extension of trailing edge lift augmentation devices

Answer 2

c.is caused by wingtip stall

Question 3

Entering the stall the centre of pressure of a straight (1) wing and of a strongly swept back wing (2) will:

a.(1) move aft, (2) not move

b.(1) move aft, (2) move aft

c.(1) move aft, (2) move forward

d.(1) not move (2) move forward

Answer 3

c.(1) move aft, (2) move forward

Question 4

Which of the following statements about stall speed is correct?

a.Decreasing the angle of sweep of the wing will decrease the stall speed

b.Increasing the anhedral of the wing will decrease the stall speed

c.Increasing the angle of sweep of the wing will decrease the stall speed

d.Use of a T-tail will decrease the stall speed

Answer 4

a.Decreasing the angle of sweep of the wing will decrease the stall speed

Question 5

Which of the following statements about the stall of a straight wing aeroplane is correct?

a.Just before the stall the aeroplane will be have an increased nose-down tendency

b.Buffeting is the result of tailplane flow separation

c.The horizontal tail will stall at a higher speed than the wing

d.The nose down effect is the result of increasing downwash, due to flow separation

Answer 5

a.Just before the stall the aeroplane will be have an increased nose-down tendency

Question 6

Which combination of design features is known to be responsible for deep stall?

a.Swept back wings and wing mounted engines

b.Swept back wings and a T-tail

c.Straight wings and a T-tail

d.Straight wings and aft fuselage mounted engines

Answer 6

b.Swept back wings and a T-tail

Question 7

Which type of stall has the largest associated angle of attack?

a.Shock stall

b.Deep stall

c.Low speed stall

d.Accelerated stall

Answer 7

b.Deep stall

Question 8

When an aeroplane is flying at an airspeed which is 1.3 times its basic stalling speed, the coefficient of lift as a percentage of the maximum lift coefficient (CLmax) would be:

a.59%

b.169%

c.130%

d.77%

Answer 8

a.59%

new CL = 100 x (1 ÷ 1.3)²
new CL = 59.17%

Question 9

A boundary layer fence on a swept wing will:

a.improve the high speed characteristics

b.increase the critical Mach Number

c.improve the lift coefficient of the trailing edge flap

d.improve the low speed characteristics

Answer 9

d.improve the low speed characteristics

Question 10

Label the correct lines on the CL-Alpha graph to represent different slats and flaps effects on the stalling angle and CLMAX.

Answer 10

trailing edge flap - green line
leading edge flap - blue line
clean wing - black line
slats/slots - dotted blue line