Exam (elaborations) AIRCRAFT MAINTANCE ENGINEERING

DGCA MODULE 8

[AERODYNAMICS ]

TEST NUMBER:-1.

1. If the wing tips stall before the root on a swept wing

aircraft, the aircraft will

a) roll

b) pitch nose up

c) pitch nose down

2) Angle of attack .

a) increases with an increased angle of incidence (angle of

attack)

b) decreases with an increase in angle of incidence (angle of

attack)

c) does not change with a change in angle of incidence

(angle of attack)

3. On a straight wing aircraft, stall commences at the

a) root on a high thickness ratio wing

b) tip on a high thickness ratio wing



c) tip on a low thickness ratio wing

4. On a high wing aircraft in a turn

a) the up-going wing loses lift causing a de-stabilising effect

b) the down-going wing gains lift causing a stabilising effect

c) the down-going wing loses lift causing a de-stabilising

effect




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,5. For the same angle of attack, the lift on a delta wing

a) is greater than the lift on a high aspect ratio wing

b) is lower than the lift on a high aspect ratio wing

c) is the same as the lift on a high aspect ratio wing

6. The ISA?

a) is taken from the equator

b) is taken from 45 degrees latitude

c) assumes a standard day

7. As altitude increases, pressure

a) decreases at constant rate

b) increases exponentially

c) decreases exponentially

8. The thrust-drag couple overcomes the lift-weight couple.

What direction of force is required to be produced by the

tail of the aircraft to maintain straight and level flight

a) upwards

b) downwards

c) sideways

9. When the pressure is half of that

at sea level, what is the altitude?

a) 12,000 ft

b) 8,000 ft

c) 18,000 ft



10. During a turn, the stalling angle




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,a) increases

b) decreases

c) remains the same

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ans[1] = "b";

ans[2] = "a";

ans[3] = "a";

ans[4] = "b";

ans[5] = "b";

ans[6] = "b";

ans[7] = "c";

ans[8] = "a";

ans[9] = "c";

ans[10] = "c";



explain[1]="Picture a side view of a swept wing aircraft. The

wing tips are behind the wing root. Think, therefore, of the lift

on the wing tip holding the tail up. Lose the lift on the tips

and what will happen?";

explain[2]="This question is much easier than it looks at first

read. All wing types (straight, swept, delta etc.) increase lift

with an increase in angle of attack (up to the stall angle).";

explain[3]="Thickness ratio is a red herring. But you must

learn the stall points for different types of wing platforms -




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, they differ greatly.";

explain[4]="The down-going wing has an increased lift due to

an increas in angle of attack (due to the up flow of air). This

opposes the roll which is a stabilizing effect.";

explain[5]="A long slender wing (i.e. high Aspect Ratio) has

a higher lift than a short stubby wing (low Aspect Ratio). A

delta wing is about as low Aspect Ratio as you can get

(about 1:1 for concord for example).";

explain[6]="The properties of a standard day are related to

sea level at latitude 45 degrees with absolutely dry air.";

explain[7]="Pressure decreases - sure! But the rate of

decrease reduces with altitude. At 18000 ft, half the

pressure is lost already, and there is still another 40,000ft or

so to go";

explain[8]="On most aircraft, the thrust-drag couple

produces a nose up pitch moment (think of how low the

thrust line is on a Boeing). It is balanced by the Centre of Lift

being behind the CG. So to correct a nose up moment, what



force do you need at the tail?";

explain[9]="Just one of those facts you have to learn - but it is

quoted in just about every text book on the CAA reading list.";

explain[10]="Do not get cofused between stalling angle and

stalling speed. In a turn the vertical component of lift is less,

so to compensate the pilot must increase speed, but the




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