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ATPL AASA > Aerodynamics > Flashcards

Aerodynamics Flashcards

1
Q

When flying at a constant Mach number, the CAS will

A

Decrease

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2
Q

When climbing at a constant Mach number, the TAS will

A

Decrease if temperature decreases

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3
Q

The difference between leading edge slats and leading edge flaps is

A

Slats reenergise the boundary layer and flaps alter the effective camber of the leading edge

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4
Q

As an aircraft climbs above FL300, the IAS and EAS stall speeds will

A

IAS and EAS stall speeds both increase

*Ie the number gets bigger and buffer between speed and stalling gets smaller

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5
Q

As an aircraft accelerates from subsonic speeds through 1.0M to supersonic speeds, the C*D (coefficient of drag) will

A

Increase then decrease

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6
Q

In a constant Mach number climb in the isothermal layer above the tropopause, TAS will

A

Remain constant due to the constant temperature

*Isothermal is where temp doesn’t behave normally
TAS = temp dependant

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7
Q

In a constant Mach number climb in the isothermal layer above the tropopause, IAS will

A

Decrease due to decreasing pressure

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8
Q

M-crit is

A

The speed above which supersonic local airflow first occurs

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9
Q

The variable most affecting the speed of sound is

A

Temperature

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10
Q

An aircraft exceeds its M-crit. Assuming no Mach Trimmer is fitted, the first thing to occur would be

A

Nose pitch down

*Because the CP moves rearward

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11
Q

For high subsonic cruise speeds, the reason it is best to delay the formation of wing shockwaves is

A

To keep the drag penalty to a minimum,m

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12
Q

Fast transport aircraft may have a supercritical wing section. This is to

A

Reduce the top wing surface acceleration

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13
Q

Aileron control reversal can be caused by

A

The wing twisting about its lateral axis due to high aerodynamic loads at high speed

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14
Q

Exceeding M-crit results in a nose down pitch in the aircraft. This is because

A

The CP moves rearward

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15
Q

An aircraft is slowly accelerating through its M-crit to transonic cruise. The coefficient of lift

A

Will increase then decrease

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16
Q

A Mach trimmer

A

Ensures that with increasing speed the aircraft will tend to pitch up

*Because aircraft will pitch down when M-crit is reached because the CP moves rearward so it needs to counter the nose down trims

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17
Q

At transonic speeds, the reason some aircraft use spoilers for roll control even though they have ailerons fitted is

A

To overcome loss of aileron effectiveness due to flow separation ahead of the aileron

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18
Q

A yaw damper

A

Minimises the need for rudder control inputs at high altitude and high Mach number

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19
Q

Wing sweep results in an increase in the stalling angle of attack. This is because

A

The swept wing C-lift is less than a straight wing C-life for any given body angle

*Think about fast jets to airliners - fast jets have less drag (and less lift) compared to straight airliners that have more lift and more drag

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20
Q

Wing sweep is an important feature for high speed flight because

A

It delays the drag effects of shockwaves

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21
Q

On swept wing aircraft, nose pitch up at the stall is caused by

A

Wing tip stall and the effective Cp moving forwards

*Cp effects the pitch

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22
Q

Most swept wing aircraft are fitted with a stick pusher because

A

The combination of wing design and powered controls does not provide adequate stall protection and recovery may be very difficult or impossible in some cases

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23
Q

Jet aircraft max rate of climb (Vy) is determined by

A

Excess power over weight

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24
Q

Vs when related to transport category aircraft is

A

Minimum steady flight speed

*CHECK THIS

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25
Q

You want your jet aircraft to stay airborne as long as possible. You would achieve this by flying

A

At an altitude where use of engine design RPM would result in a speed of V-IMD

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26
Q

To achieve maximum angle of climb (Vx), you would climb at

A

V-IMD using maximum thrust

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27
Q

Large jet aircraft have a large speed band where the rate of climb is fairly constant. This is because

A

For this band, the power available and power required curves are nearly parallel

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28
Q

V-A is

A

Manoeuvring speed

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29
Q

The Cp of a transport category aircraft wing should ideally have minimal movement with variations in aircraft speed because

A

Large trim changes would be needed with large CP movements

*Think of nose pitch up and down and how you need a mach trimmer to counter the CP movement
*Think of Cp as lift so as it moves back, lift of the tail goes up = nose down

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30
Q

You have descended to hold at 3000ft. At this altitude, your ideal holding speed would be primarily determined by

A

IAS considerations

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31
Q

Considering flap extension increases lift, they are not used for climb because

A

Min drag speed is higher with flap up and the extra drag cancels the lift benefit

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32
Q

Swept wing aircraft employ a ‘stall identification alarm system’ (stick pusher). This operates at

A

The speed below which controlled level flight is not sustainable

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33
Q

Jet aircraft overspeed warnings will operate

A

Slightly above Vmo/Mmo

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34
Q

Vmo/Mmo is

A

The max operating speed at which an aircraft may be intentionally flown

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35
Q

M-FS (free stream) is

A

The actual Mach number of the aircraft through the air

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36
Q

M-DET is

A

The aircraft speed above which all the local flow is supersonic

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37
Q

Airflow through a shockwave will experience

A

Increase in temp, density and pressure but decrease in velocity

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38
Q

An emergency climb on encountering severe low level wind shear would be achieved by

A

Climbing at a target 1.1Vs and using takeoff power

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39
Q

Jet aircraft SAR as a comparison of air distance per tonne of fuel consumed would be expr3essed in the form

A

100 anm / 1000 kg

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40
Q

To achieve maximum range at a given flight level, you would fly at

A

1.32 V-IMD

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41
Q

Optimum range is achieved by flying at

A

Cruise climb, 1.32V-IMD and design RPM

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42
Q

Climb IAS decreases with increased altitude because

A

Maximum excess power occurs at a lower IAS at high altitude

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43
Q

A jet aircraft climbs at a constant Mach number after reaching a certain altitude because

A

It equates with the required reducing IAS and to prevent Mach overspeed

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44
Q

For a given altitude and weight, the IAS variation for maximum angle of climb is flap is extended is

A

It decreases to maintain a lower minimum drag speed

*Think of takeoff with flaps being at a lower speed

45
Q

The theoretical requirement (as far as the airframe is concerned) for max range cruise is

A

An IAS of 1.32 V-IMD at a cruise level as high as possible

46
Q

If required to cruise at a level with significant headwind when maximum range is required

A

You would fly faster than the nil wind max range speed because you need to achieve the best GS/drag ratio

*Range is distance

47
Q

In a steady climb, compared to nil headwind, a headwind will affect

A

Angle of climb only

*Rate of climb is unchanged

48
Q

V-A for an aircraft (manoeuvring speed)

A

Is higher at higher gross weights and lower at lower gross weights

*Think of being at max weight punching through turbulence, you have to go faster because you’re heavier because the airframe gets stressed quicker because it’s got more load on it
*If you’re lighter through turbulence, you get bounced around more but airframe doesn’t get as stressed because it’s not as heavy so your speed can be lower

49
Q

As airflow passes through a normal (vertical) shockwave

A

Velocity changes from supersonic to subsonic with no changes in direction

50
Q

Concerning slotted flaps and/or Fowler flaps

A

Slotted flaps increase the camber and preserve energy in the boundary layer of the airflow while Fowler flaps increase the camber and the chord

51
Q

Flap extension at high altitude is not permitted on most aircraft because

A

Flap extension speed may be below the stalling speed at high altitude

52
Q

The speed of the airflow through a normal shockwave changes from

A

Supersonic to subsonic

53
Q

A nose down pitch change in an aircraft flying near M-CRIT would most likely be caused by

A

A rearwards CP shift

54
Q

The one which is not an advantage of a swept back wing compared to a straight wing is:
A. Less gust sensitivity
B. Higher M-CRIT
C. Less drag at high speed
D. More effective trailing edge devices

A

More effective trailing edge devices

55
Q

An internal flexible seal attached to the leading edge of a control surface is designed to

A

Assist control load balancing

56
Q

The minimum control speed ground (V-MCG) is lower than the minimum control speed air (V-MCA) because

A

The main wheels are on the ground

57
Q

When flying at very high altitude in a swept wing jet transport category aircraft, vibration felt through the airframe during manoeuvres would be caused by

A

Either high or low speed buffet

58
Q

If the best lift/drag ratio for an aircraft is achieved at a speed of X, then for best angle of climb, the aircraft should fly at a speed of

A

Equal to X

59
Q

True or false
Cruising at a high FL will always increase specific air range (SAR)

A

False

60
Q

True or false
Max endurance is achieved at best L/D ratio

A

True

*Endurance is time

61
Q

At all altitudes, Mach number is the ratio of TAS to LSS at MSL (local speed of sound)

A

False

*Look it up, I suspect it has something to do with density/pressure

62
Q

True or false
Any headwind or tailwind will reduce the distance to a PNR

A

True

*PNR is distance based
*Headwind or tail wind will mean when you turn around you have the distance to return so is shorter

63
Q

True or false
The Mach number required for maximum range cruise is independent of head or tail wind component

A

False

*Range is distance so is effected by wind (think about PNR being effected by wind)

64
Q

True or false
Low SFC (specific fuel consumption) is best achieved at low altitude and low engine RPM

A

False

*High altitude and design RPM

65
Q

True or false
The AoA required for maximum range cruise does not vary with aircraft gross weight

A

True

*AoA always remains constant regardless of weight

66
Q

True or false
For a given FL and GW, induced drag will decrease with increasing IAS

A

True

67
Q

True or false
For a constant IAS and FL, Mach number is affected by changes in air temperature

A

False

68
Q

True or false
Maximum static thrust increases with increasing ambient temperature

A

False

*Thrust decreases with an increase in temp

69
Q

True or false
During constant altitude cruise, a reduction in aircraft gross weight will require a redacting in wing angle of attack to maintain the optimum lift coefficient for subsonic cruise

A

False

*AoA always remains constant

70
Q

True or false
M-CRIT is that free stream Mach number below which all airflow is subsonic

A

True

71
Q

True or false
High propulsion efficiency is typified by low mass flow and maximum possible velocity change

A

False

72
Q

True or false
The component of Total Reaction force parallel to the remote free airstream is termed induced drag

A

True

73
Q

True or false
Engine specific fuel consumption is directly proportional to engine thrust

A

False

74
Q

True or false
For a single sector flight at a constant TAS, an increased wind component will always decrease the distance from departure to PNR

A

True

75
Q

True or false
For cruise at a constant Mach number and constant altitude, buffet boundary margins increase with increasing gross weight

A

False

76
Q

True or false
Wing sweep back will increase M-CRIT

A

True

77
Q

True or false
Maximum static thrust decreases with decreasing altitude

A

False

*Thrust increases with decreasing altitude because air density increases

78
Q

True or false
For any flight sector, an increasing headwind component increases the distance to the CP/ETP

A

True

*ETP/CP is time based so with a headwind, you can go further before you have to turn around
*When you turn around you’ll have the tailwind choofing you home so can go further distance to start

79
Q

True or false
For a single stage and constant tailwind component outbound, the distance from departure to the CP increases with increasing TAS

A

True

80
Q

True or false
Maximum range is achieved at CL/CD max

A

False

*Range is distance, also dependant on wind

81
Q

True or false
Specific fuel consumption (SFC) decreases with increasing inlet air temperature

A

False

*SFC is thrust produced per hour per unit of fuel use per hour
*Thrust decreases with increasing temp

82
Q

True or false
Induced drag increases with increasing AoA

A

True

83
Q

True or false
At constant cruise level, the long range cruising Mach number (M-LRC) decreases with decreasing gross weight

A

True

84
Q

True or false
The AoA for best endurance at a constant altitude decreases with decreasing gross weight

A

False

*AoA always remains constant

85
Q

True or false
In the isothermal layer above the tropopause, a constant velocity (TAS) cruise climb would produce a constant Mach number

A

True

86
Q

True or false
SFC increases as engine RPM increases towards design RPM

A

False

*SFC is unit of thrust produced per unit of fuel used per hour

87
Q

True or false
Engine efficiency decreases rapidly past 70-75% of max RPM during engine acceleration

A

False

88
Q

True or false
At constant altitude, max available engine thrust does not vary with changes in aircraft speed

A

False

*It does change with aircraft speed

89
Q

True or false
At constant altitude, specific duel consumption increases with increasing engine RPM towards design RPM

A

False

90
Q

True or false
Gas turbine engine thrust varies linearly with engine RPM

A

False

91
Q

True or false
Gas turbine engine compressor stalls are characterised by both low engine RPM and low exhaust gas temperatures

A

False

92
Q

True or false
Engine airflow undergoes the greatest pressure change through the compressor

A

True

*Pressure increases through the compressor
Pressure remains constant through combustion

93
Q

True or false
Wing sweep back will delay the onsets of wing compressibility effects

A

True

94
Q

True or false
Airflow behind a normal (vertical) shockwave is always subsonic

A

True

95
Q

True or false
At constant speed and altitude, induced drag is independent of bank angle

A

False

*Induced drag is dependant on bank angle

96
Q

True or false
Induced drag decreases with increasing aspect ratio

A

True

*Think of gliders having minimum drag with their huge wings

97
Q

True or false
Average cruise EPR require is independent of TAT

A

True

98
Q

True or false
The minimum thrust and minimum angle of descent is obtained at L/D max

A

True

99
Q

True or false
At constant altitude, Mach number is the ratio of the local TAS to the MSL speed of sound

A

False

100
Q

True or false
At constant IAS and FL, Mach number is not affected by changes in air temperature

A

True

101
Q

True or false
The maximum range cruise Mach number is independent of head or tail wind component

A

False

102
Q

True or false
At constant cruise level, the long range cruise Mach number increases with decreasing gross weight

A

False

103
Q

True or false
Below the tropopause, a constant Mach number cruise climb would produce a constant IAS

A

False

104
Q

True or false
Specific fuel consumption increases with increasing engine RPM toward design RPM

A

False

105
Q

True or false
At constant cruise level, SGR will always increase as cruise TAS increases

A

False

106
Q

True or false
The maximum quick turn around weight increases with increasing runway downslope

A

False

107
Q

True or false
The limiting IAS for flight with the 727 yaw damper system U/S is independent of aircraft altitude

A

False

*Think about the king air MEL not being able to fly above FL190

108
Q

True or false
Both maximum endurance and maximum climb angle performance occur at L/D max

A

True

ATPL AASA (3 decks)

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