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ATPL POF > High Speed Flight + contamination > Flashcards

High Speed Flight + contamination Flashcards

(84 cards)

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1
Q

What is the equation for local speed of sound

A

LSS = 39squarerootk

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2
Q

What is the equation to work out the Mach number

A

Mach number = TAS / LSS

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3
Q

In subsonic flight describe the Mach. Numbers

A

All local Mach numbers are below 1

For low subsonic Mfs = <0.4

For high subsonic Mfs = >0.4

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4
Q

Describe transonic Mach numbers

A

Somewhere

Ml <1
Ml = 1
Ml >1

Somewhere in transonic region Mfs = 1

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5
Q

Describe supersonic Mach numbers

A

All local Mach numbers >1

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6
Q

What is Mcrit

A

The free steam Mach number which somewhere on your aircraft you have a local flow of Mach 1

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7
Q

What is Mdet

A

Mach detachment speed

Measures as free stream

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8
Q

Where do normal shockwaves occur

A

In the transonic region

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9
Q

Can air flow normally through a normal shockwave

A

Yeh

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10
Q

What speed is the airflow infront of the normal shockwave

A

Supersonic

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11
Q

What speed is the airflow behind the normal shockwave

A

Subsonic

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12
Q

If the air infront of the normal shockwave is 10% above Mach 1 what is the air behind the shockwave like

A

10% below Mach 1

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13
Q

How thick is the normal shockwave

A

0.0025mm

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14
Q

What is the most violent shockwave

A

Normal shockwave

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15
Q

What shockwave creates the most drag

A

Normal shockwave

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16
Q

What does a shockwave do to temperature and density

A

Temperature increases (energy comes from total pressure decrease)

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17
Q

When do oblique shockwaves occur

A

At a higher speed than normal shockwaves

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18
Q

If the speed of the airflow is above Mach 1 infront of the oblique shockwave what speed it is behind

A

Above Mach 1 but slower

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19
Q

Does the oblique shockwave change direction of the airflow

A

Yes it does

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20
Q

What creates a bow wave

A

Normal shockwave
+
Oblique shockwave

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21
Q

What happens to the bow wave as speed increases

A

Stagnation point (which creates the normal wave) decreases and eventually the bow wave attaches to leading edge creating just a oblique wave

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22
Q

At what speed does the bow wave attach or detach from the leading edge

A

Mdet

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23
Q

What shockwave do we feel / creates the sonic boom we hear

A

Oblique shockwaves

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24
Q

How does speed affect the oblique shockwave

A

Faster we go the more pushed back they become

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25
How does speed affect the Mach cone
Faster you go the smaller the Mach cone around aircraft
26
What is the Mach cone angle
Angle between flight path and the oblique shockwaves
27
What is the equation for the Mach cone angle
Sin *angle*= LSS/TAS Or = 1/Mach n
28
What is the expansion wave
NOT A SHOCKWAVE Air curving round a surface Speed or air flow in an expansion increase Temp decreases Density decreases Pressure / energy the same
29
What happens to Mach number when you go into warmer air
Constant Mach number Temp ^ Density down
30
What is chicken tikka masala
In tropopause = chicken. Tikkamasala In isotherm = chicken masala tika
31
What happens to AOA as you climb at high speed on constant Mach
Increases (small increase)
32
What happens to flight path angle if you’re climbing at high speed on a constant Mach
Decreases
33
What happens to pitch as you’re climbing on a constant Mach at high speed
Decreases
34
What happens to AOA as you’re climbing on a constant CAS at high speed
Remains constant
35
What happens to flight path angle as you climb at a contact CAS
Decreases
36
What happens to pitch at you climb at a content CAS
Decreases
37
What happens to AOA as you descent on a constant Mach
Decreases
38
What happens to flight path angle as you descend on a constant Mach
Increases
39
What happens to pitch angle as you descend on a constant Mach
Decreases
40
What happens to AOA Flight path angle And pitch angle when descending on a constant CAS
Remain constant
41
What is Mcrit
The free stream Mach number at which somewhere on the aircraft reaches Mach 1 Assuming load factor of 1
42
How does a thick wing affect Mcrit
Lower Mcrit
43
What happens above Mcrit
A normal shock wave is formed
44
As you increase speed up to what point does the cp keep moving rearwards
Just before Mach drag divergence
45
What happens when separation for normal shockwaves occurs at the trailing edge for both upper and lower normal shockwaves
Most drag
46
What happens when normal shockwave transforms into an oblique wave
Centre of pressure shoots back to 50%
47
What happens at Mach 1 Mfs
Normal shockwaves attach to trailing edge and also a bow wave forms
48
Life of a shockwave
See notes in jotted = can’t type it well
49
Describe the pressure distribution when there is oblique waves at the trailing edge and a bow wave at the leading edge
Uniform pressure distribution over the wing
50
When is a aircraft super sonic
After Mdet
51
When is the Mach drag divergence
Just beyond Clmax
52
When is the worst Cl/Cd ratio for high speed flight
Mfs 1
53
What happens when the cp shoots aft in high speed flight
Pitch forward = Mach tuck Aircraft needs a Mach trimmer = needs all moving tailplane
54
What happens to stick force gradient after Mcrit
Stick force gradient becomes neutral (doesn’t get harder to move with height) After even more speed increase eventually becomes negative
55
What is the aerodynamic ceiling
At this height any increase / decrease in speed results in stall or shock stall
56
What is the buffer margin
A range of speeds below the ceiling to ensure u don’t stall and to allow for turbulence / disturbance
57
What does aerodynamic ceiling reduce with
Anything that increases stall speed
58
What is the manoeuvre ceiling
Aerodynamic ceiling adjusted for the ability to manoeuvre
59
How does thickness to chord ratio affect Mcrit number
High thickness to chord ratio = lower Mcrit number
60
What is a super critical wing
Large radius leading edge Flatter upper surface Both negatively and positively cambered aerofoil Better for high speed flight than a normal wing of similar thickness to chord ratio
61
How does sweep back wings affect Mcrit
Increases effective chord length Reduces thickness to chord ratio Increases Mcrit
62
What can you put infront of the usually places for separation to occur due to shockwaves
Vortex generators
63
What is wave dependant on
Surface area (cross sectional area)
64
How can you reduce wave drag
Area ruling Intending the fuselage for wings to reduce cross sectional area
65
What are the disadvantages of s supercritical aerofoil
can produce rapid and unpredictable movement of the separation point Poor low speed handling Large nose down pitching moment because majority of lift occurs in the rear 30% of wing Isn’t practical wing shape for root which makes installation of trailing edge devices difficult
66
What happens to Mcrit when you sweep back a wing
Effective chord longer = reduces thickness - chord ratio = increases Mcrit
67
What is airframe contamination
Anything that is going to change the surface of the aircraft
68
Where is frost most likely to form on a aircraft
Under the wing due to cool fuel Brush off or de-ice
69
What airspeed does frost not tend to form above
250knots
70
Where does snow form inflight usually
Stagnation points Leading edges
71
What airspeed does rime ice not tend to form over
250 knots
72
How can you get rid of rime ice
Warming leading edge Or Inflatable boots (however they need to let ice build up first)
73
What aircraft is most at risk from clear ice
Turbo props as they usually fly in the altitudes associated with it
74
What effect does contamination have on drag
Skin friction drag increase Increased weight = induced drag increase
75
What thickness aerofoil is worst for icing
Thin aerofoil
76
What aircraft surface is most susceptible to icing
Tailplane because it’s a thin aerofoil
77
What phase of flight is tailplane icing the biggest risk
Approach = slow speeds, large downwash
78
What effect could flaps have on the tailplane if it is iced
Flaps down = greater Downwash = greater AOA on tailplane = if iced could stall
79
How to recover from a tailplane stall due to flaps in icing conditions
Return to previous flap setting
80
What anti icing is left on permanently
Pitots Pilot window (more stronger protection against bird strikes if warm)
81
What is deformation
Damage twisting buckling Changing shape
82
What is degradation
Surface worn away over time Solved by repainting
83
Eqn for local speed of sound
39 *squareroot* temp in kelvin
84
How to calculate the Mach cone angle
Sin*angle* = 1/Mach number Or Sin*angle* = LSS/TAS

ATPL POF (12 decks)

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