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Aerodynamics > AER 6: Performance > Flashcards

AER 6: Performance Flashcards

1
Q

Explain engine failure during cruise

A
  1. Decrease in performance
  2. Decrease in operating ceiling
  3. Decrease in airspeed
  4. Alters SAR
  5. Think of safety in terms of safety height.
    Resultant path is a glide down from the original altitude.
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2
Q

Define Vat

A

Vat: Velocity at threshold
Is the speed that an a/c should have as it passes over the THRS to land. Based on 1.3 x stall speed in the landing configuration at max landing weight with the power off.
Aircraft performance categories are based off of this speed. E.g. CAT A: speeds up to 90KIAS.

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3
Q

Define Vmca

A

Vmca: The minimum control airspeed.
The minimum speed with gear up, flaps set for takeoff and failure of a feathered engine, that the remaining live engine can maintain control of the aircraft.

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4
Q

Define SAR

A

Specific Air range.

The maximum flying distance with set fuel or minimum fuel to fly a set distance. (TAS/FF)

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5
Q

Explain how to achieve SAR for turbo props

A
  1. Drag is minimum (gear and flaps up)
  2. Prop efficiency is max
  3. Maintain speed at just above Vimd - minimum drag speed (as otherwise you will slide into increased drag curve)
  4. Engine and air frame variables are set for efficiency.
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6
Q

Define Specific Endurance

A

The amount of time airborne that can be achieved per pound of fuel. (flight hours/Fuel used).

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7
Q

What is specific endurance impacted by?

A
  1. Engine output (SHP)
  2. Engine and prop efficiency
  3. Specific endurance decreases as weight of the aircraft increases.
    WIND DOES NOT EFFECT ENDURANCE.
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8
Q

Disadvantages of Specific endurance?

A

The minimum power speed (Vmp) is in the instability range. Any manoeuvre will increase drag having an immediate effect on airspeed and stall speed.

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9
Q

Define TORA

A

Take off RWY available.

Length of the RWY available for the ground run of takeoff.

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10
Q

Define Stopway

A

Defined rectangular area at the end of the RWY used for an aircraft to stop in the case of an interrupted take - off.

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11
Q

Define RESA

A

RWY End Safety Area.
Is additional to the stopway and is the cleared area at either end of the RWY for use by aircraft undershooting or overrunning the RWY.
Because of RESA, sometimes less than the full length of the RWY is available for takeoff/landing.

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12
Q

Define Clearway

A

Defined area 90m either side of the THRS centre line in the direction of take off over which an aircraft may make a portion of its initial climb.

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13
Q

Define TORr

A

Take off run required

The length of the RWY required for an aircraft to accelerate from a stop to the speed at which it becomes airborne.

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14
Q

Define TORA

A

Take off run available

The amount of the RWY actually available for use in the Take off run. (TORA must always be more than TORr)

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15
Q

Define TODr

A

Take off distance required

The distance required by an aircraft to accelerate from a standing start and climb out to a screen height of 35ft.

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16
Q

Define TODA

A

Take off distance available
The distance available to achieve its screen height.
Usually includes: TORA + Stopway + clearway.
(TODA must always be more than TODr)

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17
Q

Factors affecting TOR and TODr

A
  1. Weight (increase means a longer takeoff roll)
  2. Temperature (increase = reduced thrust due to lower air density and therefore a longer takeoff roll)
  3. Pressure (decrease in pressure =reduced thrust)
  4. Headwind/tailwind
  5. Slope
18
Q

Define V1

A

Decision speed
The speed up until which an abort of takeoff can be safely conducted. Take off must continue if a malfunction occurs past this speed

19
Q

Define V2

A

Aircraft takeoff safety speed

20
Q

Define TOR1

A

Take off run 1
The take off RUN required by an aircraft to accelerate to V1, have an engine failure and continue to take off on one engine.

21
Q

Define TOD1

A

Take off distance 1
The take off DISTANCE required by an aircraft to accelerate to V1, have an engine failure and continue to take off on one engine

22
Q

Define ASDR/EMDR

A

Accelerate/Stop distance or emergency distance required.
The distance required for an aircraft to accelerate to V1, have an engine failure and use max braking to come to a halt on the RWY

23
Q

Define the cruise climb

A

As fuel is burnt, weight of the aircraft reduces.

If TAS, AoA and thrust is kept constant, the aircraft will eventually gradually climb due to excess lift.

24
Q

Explain the effects of altitude on climb performance

A
  1. As altitude increases, both Angle of climb and rate of climb are reduced.
    This is due to thrust reducing with altitude (due to density of the air. (power required increases, power produced decreases).
25
Q

Define climb gradient

A

The distance traveled vertically divided by the distance covered over the ground.
Can be expressed as a ratio or percentage.

26
Q

Factors affecting climb gradient

A
  1. Flaps (increase of flap = more lift, shorter ground roll. Climb is slower and distance across ground shorter)
  2. Air density
  3. Temperature (effects air density)
27
Q

Define LDA

A

Landing distance available

28
Q

Define LDr

A

Landing distance required

29
Q

Define range

A

The DISTANCE covered for a given weight of fuel (in NM)

30
Q

Endurance

A

The TIME airborne for a given weight of fuel

31
Q

Define Specific range

A
  1. the maximum range for a given amount of fuel
    OR
  2. the minimum fuel for a given range/set distance
32
Q

Define the two types of Specific Range

A
  1. SAR (Specific air range) = Air miles traveled (anm)/Fuel used
  2. SGR (specific ground range) = Ground miles traveled (gnm)/Fuel used

NOTE: SGR = SAR +wind velocity

33
Q

Summarise Range

A
  • Distance able to be flown with useable fuel.
  • Optimised for Prop aircraft when flown slightly about Vimd.
  • Range increases with height and tail wind.
  • Decreases with increased weight and increased head wind.
34
Q

What are range and endurance both affected by?

A
  • Altitude
  • Wind velocity
  • Weight
  • Drag (flaps/gear/camera)
35
Q

How does wind affect range?

A
  • Headwind = decrease in range

- Tailwind = increase in range

36
Q

Summarise endurance

A
  • Maximum time spent airborne
  • Optimised for prop aircraft when flown at Vimp
  • Increases with altitude and engine efficiency.
  • Decreases with increased weight
37
Q

Aerodynamic effects of icing

A
  • Reduces performance of the aircraft
  • changes the shape and form of the aerofoil and effects the airflow over this. (reduces lift and causes drag)
  • Ice formation increases thrust required and increases the stall speed.
38
Q

Identify the three different types of icing

A
  • Hoar frost: fine deposit of ice similar to that you’d find on the edges of a freezer. Caused when aircraft skin temp is less than zero in high humidity
  • Rime ice: White opaque, rough deposit, small supercooled water droplets that freeze on impact.
  • Clear ice: transparent sheet of ice, slow freezing and difficult to get visual of - the most dangerous.
39
Q

What areas of the aircraft are more susceptible to ice?

A

areas that face the relative airflow head on (e.g. the engine intakes). The smaller the diameter of the surface, the more likely ice is to form.

40
Q

What factors affect the effectiveness of the primary controls?

A
  • Size and shape of the control surface
  • Moment arm
  • Deflection angle
  • Speed

Aerodynamics (6 decks)

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