Chapter 29: Effects of High Speed Flight

Question 1

Transonic Flight

Steps (5)

Answer 1

1. Normal shockwave after Mcrit, Cp moves back
2. High speed shock stall. Too big adverse P gradient
3. Bot shockwave goes to back, Cp moves forward
4. Both shockwaves almost meet at M = .99 still M stall, max D, CP moves 50% aft
5. M = 1 bow wave

Question 2

Clmax as function of M

Vary with Mach, when start, finish, steps?

Answer 2

Starts at Mcrit
Cl increase until shock stall
decrease until bottom shock goes aft and intensifies
increases until top shock goes aft and intensifies
decreases and stabilises at oblique wave / bow wave
Finishes at Mdet

Question 3

Cd

Vary with Mach

Answer 3

Starts at Mcrit
Significantly increases at Mdivergence with shock stall
Max at M = 1
decreases and stabilises
Ends at Mdet

Question 4

Stick Force Gradient

Stability?

Answer 4

Stable until Mcrit

Question 5

Control Effectiveness

Vary with Mach

Answer 5

Increase until Mcrit
Decrease
Increase when normal shockwave over surface

Question 6

Aerodynamic Ceiling

What is?

Answer 6

Altitiude at which shockwave stall meets stall

Question 7

Shockwave Effect

How to reduce (5)

Answer 7

Higher Mcrit
Thin aerofoil (but less camber, less room for flaps...)
Super critical aerofoil
Sweepback
Area ruling

Question 8

Super Critical Aerofoil

Characteristics (4)

Answer 8

Blunt LE
Flattened upper surface
Relatively thick TE
S-shaped camberline

Question 9

Sweepback

How affects Shockwave, calculation? Difference between short and long haul?

Answer 9

Increase finesse ratio
Mcrit = Mcrit / cos (sweep angle)
Short = 25°
Long haul = 37°

Question 10

Supersonic Wing

Straight vs. Sweepback

Answer 10

Straight better for supersonic (less D)

Sweepback better for becoming supersonic

Question 11

Hypersonic

Answer 11

M > 5