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Phenom Info > MEPT Principles of Flight Revision Questions V2.0 > Flashcards

MEPT Principles of Flight Revision Questions V2.0 Flashcards

1
Q

What basic formula can express the % power efficiency of an engine?

A

(Power output ÷ Power input) × 100

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2
Q

How can the power output of a turbo-prop engine be expressed?

A

Propeller thrust × TAS

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3
Q

How can the power input of a turbo-prop engine be expressed?

A

Torque × Propeller RPM

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4
Q

How does the efficiency of a turboprop vary with speed?

A

It increases rapidly at low speed but falls to zero at high speeds

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5
Q

How do you increase the solidity of a propeller?

A

Increase the number of propeller blades

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6
Q

What does increasing the solidity of a propeller achieve?

A

Adding more propeller blades absorbs the extra torque available from a more powerful engine
and converts it to extra thrust.

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7
Q

What design features of a propeller blade mitigate against the adverse effects of
compressibility due to high speeds at the propeller tips?

A

Broader chord to reduce blade aspect ratio and curved blades increasing the sweep at the tips
both reduce compressibility effects.

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8
Q

What is the benefit gained by having counter-rotating propellers?

A

It mitigates any swing caused by asymmetric blade effect.

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9
Q

What is the formula for turbo-jet thrust?

A

M × (Ve - Vi).

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10
Q

What is the formula for turbo-jet power?

A

M × (Ve - Vi) × TAS.

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11
Q

How does the efficiency of a turbo-jet vary with speed?

A

It increases slowly at low speed but the efficiency continues to increase into the supersonic
speed range.

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12
Q

How can a turbo-jet enhance its thrust without overheating the turbine stages?

A

Using afterburner/reheat to increase exhaust velocity.

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12
Q

Approximately how much fuel energy is wasted producing heat rather than thrust in a turbo-jet
engine?

A

75%.

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13
Q

How does a turbo-fan produce more thrust without increasing combustion temperature?

A

It uses mechanical energy from an additional turbine stage to drive a fan stage, significantly
increasing by-pass mass flow to produce more thrust.

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14
Q

How does the efficiency of a turbo-fan engine vary with speed?

A

Increased by-pass thrust mean efficiency increases quickly even at low speed, however, the
efficiency will decrease into the supersonic speed range due to drag from the fan.

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15
Q

What is the immediate control effect of asymmetric thrust?

A

Yaw towards the failed (dead) engine.

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16
Q

Which way will the sideslip indicator move following asymmetric engine failure?

A

Towards the operating (live) engine.

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17
Q

What is the secondary control effect of asymmetric thrust?
.

A

Roll towards the failed (dead) engine

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18
Q

Would flying at a higher speed make asymmetric control more or less difficult?

A

Less difficult.

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19
Q

Would using maximum thrust make asymmetric control more or less difficult?

A

More difficult.

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20
Q

Would the loss of a critical engine make asymmetric control more or less difficult?

A

More difficult.

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21
Q

What would be the preferred method of regaining control in the event of an asymmetric engine
failure below V1?

A

Reducing all thrust to idle.

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22
Q

What would be the preferred method of regaining control in the event of an asymmetric engine
failure after take-off?

A

Maintaining wings level and stopping yaw with rudder.

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23
Q

At or near VMCA, what additional action is required to prevent yaw if full rudder is already
applied?

A

Apply up to 5° of bank towards to live engine.

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24
Q

What is the term for the minimum speed required to maintain directional control on the runway,
during take-off, by rudder alone?

A

VMCG.

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25
Q

The mnemonic for priority actions following EFATO is CIC-TDT-RAF. What does TDT stand
for?

A

Thrust-Drag-Trim.

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26
Q

The mnemonic for priority actions following EFATO is CIC-TDT-RAF. What does CIC stand
for?

A

Control-Identify-Confirm.

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27
Q

The mnemonic for priority actions following EFATO is CIC-TDT-RAF. What does RAF stand
for?

A

Radio-After Take-Off Checks-FRC.

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28
Q

What is the VMCA of the Phenom?

A

97 KIAS

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29
Q

Below what speed does air behave like an incompressible fluid?

A

250-300 kts

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30
Q

What is the only variable when calculating the local speed of sound?

A

Temperature

31
Q

How is the Mach number calculated?

A

Ratio of TAS over the local speed of sound

32
Q

If an aircraft is travelling at 85% of the local speed of sound, What Mach number would this
be?

A

Mach 0.85

33
Q

What is the Free Stream Mach Number (MFS)?

A

Mach number of the airflow past an aircraft that is unaffected by its passage

34
Q

What is the Local Mach Number (ML)?

A

Mach number of the airflow over the aircraft as measured by a localised point

35
Q

What is the Critical Mach Number (MCRIT)?

A

MFS at which the ML of flow about an aircraft first reaches Mach 1.0.

36
Q

What happens at MCRIT?

A

Shockwaves begin to form at this speed

37
Q

What does the Detachment Mach Number (MDET) indicate?

A

The end of transonic flight and beginning of true supersonic flight

38
Q

As MFS increases towards Mach 1.0 an aircraft’s centre of pressure moves rearwards, causing
an increasing nose down pitch force. What is this known as?

A

Mach Tuck

39
Q

On large multi-engine aircraft, what is used as a solution to Mach Tuck?

A

The all-flying tail plane

40
Q

What are the principal developments in transonic aerodynamics that help to delay the
Formation of Shockwaves?

A

Thin wings
Swept wings
Area ruling
Supercritical wings

41
Q

What are some disadvantages of thin wings?

A

Poor lift at low speeds
Small volume makes it difficult to incorporate flight controls, flaps and slats, landing gear and
integral fuel tanks
Difficult to ensure structural integrity and stiffness

42
Q

In aircraft design, what ensures a smooth change in cross-sectional area from nose to tail?

A

Area Ruling

43
Q

What is the altitude where both MMO and the aerodynamic stalling speed converge called?

A

The Buffet Boundary

44
Q

What are the disadvantages of a swept wing?

A

Difficult to construct a swept wing with sufficient structural stiffness
Reduced CLMAX leads to high approach and landing speed at high AoA
Formation of ‘ram’s horn’ vortex caused by requisite high AoA

45
Q

What are the advantages of a supercritical aerofoil?

A

Requires less sweep angle
More space for fuel
Higher thickness/chord ratio gives greater strength.
Reduced fuel consumption
Greater payload
Greater range

46
Q

What are the characteristics of a supercritical aerofoil?

A

Increased Leading Edge Radius
Flattened Middle Region of the Upper Surface
Thicker Trailing Edge
Higher Thickness To Chord Ratio
Increased Aft Camber

47
Q

If lift increases in proportion to the square of an aircraft’s increase in size, why do large aircraft
need lift augmentation?

A

Because their weight increases in proportion to the cube of their size increase, i.e. weight increases faster than lift.

48
Q

What effect does lift augmentation have on the take-off and landing performance of large,
heavy, transonic aircraft?

A

Reduces landing and take-off speeds and therefore the take-off and landing distances required.

49
Q

What type of flap system is found on most aircraft due to its high degree of lift augmentation?

A

The slotted Fowler flap.

50
Q

Apart from using slats and double slotted Fowler flaps, how does a C-17 further increase lift
augmentation?

A

Engine thrust is directly blown over the flaps to enhance lift.

51
Q

What affect do flaps have on the wings critical (stalling) AoA?

A

Critical AoA is reduced.

52
Q

What affect do leading edge slats have on the wings critical (stalling) AoA?

A

Critical AoA is increased.

53
Q

What type of flap is, in fact, a leading-edge lift augmentation device?

A

Kruger flap.

54
Q

Deploying trailing edge flaps increase the camber of the wing, enhancing CL. How does the
Fowler flap further augment the lift produced by a wing?

A

Fowler flaps extend to increase chord length, increasing the wings surface area and thereby further increasing lift.

55
Q

How do slots in flaps increase lift?

A

Higher pressure air from the lower surface of a wing is accelerated through the slot to the upper surface, re-energising the boundary layer and delaying flow separation.

56
Q

What is the difference between a leading-edge slot and a leading-edge slat?

A

Slots are fixed and feature on the wings of low speed STOL aircraft, leading-edge slats can be retracted and deployed to provide lift augmentation on faster and larger aircraft.

57
Q

What force on an aircraft is generated by the formation of wingtip vortices?

A

Induced or lift dependant drag

58
Q

How do winglets mitigate the adverse effects of wingtip vortices?

A

They reduce the size of vortices produced and move them above and away from the outer wing lift generation area.

59
Q

What terms define the design parameters of a winglet?

A

Cant Angle, Toe Angle and Twist.

60
Q

What wing design factors enhance lateral stability?

A

Wing dihedral; wing sweep; wing, fuselage and fin configuration.

61
Q

How does wing dihedral enhance lateral stability?

A

Any lateral disturbance produces sideslip, which increases the angle of attack, and therefore lift, in the down going wing if dihedral is present. This provides a restoring force returning the
wings to level.

62
Q

How does wing sweep enhance lateral stability?

A

Any lateral disturbance produces sideslip, which increases the aspect ratio, and therefore lift, in the down going wing if sweep is present. This provides a restoring force returning the wings
to level.

63
Q

How does a high wing and T-tail configuration enhance lateral stability?

A

Any lateral disturbance produces sideslip, all element of the fuselage, wing, and tail above the CofG will produce a weathercock effect, providing a restoring lateral force.

64
Q

What is the effect of speed on lateral stability?

A

High speed reduces lateral stability.

65
Q

Why do aircraft with a high, swept wing need anhedral?

A

High mounted swept wings are strongly laterally stable and anhedral balances control and stability.

66
Q

What is adverse yaw?

A

Adverse yaw is the tendency for an aircraft to yaw in the opposite direction to a commanded roll due to induced drag from the ailerons.

67
Q

What is the alternative method of lateral control to ailerons?

A

Differential spoilers.

68
Q

What control functions can be performed by aircraft spoiler systems?

A

Lateral (roll) control, speed-brakes, lift dumping (landing spoilers).

69
Q

What is Spiral Stability?

A

The tendency for an aircraft to roll wings level when controls are released in a level turn.

70
Q

What is the cause of spiral instability?

A

Sideslip induced yaw can cause an aircraft to roll into a steepening spiral dive with insufficient
lateral control to recover.

71
Q

What factors increase spiral instability?

A

High angles of bank, large fin area, Low airspeed.

72
Q

What effect does the size of an aircraft’s fin have on stability?

A

A large fin area gives good directional stability but poor spiral stability. A small fin area is good
for spiral stability but weakens directional stability.

73
Q

What is Dutch Roll?

A

Dutch roll is a form of dynamic instability caused by weak directional stability coupled with
strong lateral stability. This leads to an increasing roll/yaw oscillation that can cause structural
failure.

74
Q

What effect does altitude have on the tendency to Dutch Roll?

A

Increasing altitude reduces the effectiveness of the fin (vertical stabilizer) due to high TAS/IAS
ratio and reduced density. This increases the tendency for Dutch Roll to develop.

75
Q

What device is used to enhance an aircraft’s directional stability?

A

Yaw damper.

76
Q
A

Phenom Info (35 decks)

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