Chapter 28: Introduction to High Speed Flight Flashcards
Speed of Sound
Formula, how does it vary with altitude
a = 39 sqrt (T) in K
a decreaseses with altitude until tropopause, then constant, then increases
Compressibility
When does it start, how is Vs affected?
Starts at .4M (i.e. 300 - 350 kn) TAS
Increases Vs because reduces energy of flow
Mach Number
Formula? Types of mach (2)
M = TAS / a Mfs = mach free stream Ml = mach local
Flow Types (3)
M < 1 Subsonic
M = 1 Sonic
M > 1 Supersonic
Speed Regions
Regions (4), flow type, transition machs
Low subsonic (subsonic) Mfs < .4
High subsonic (subsonic) Mfs > .4
Transonic (local subsonic, sonic, supersonic) Mcrit
Supersonic (supersonic) Mdet
Normal Shockwave
When does it happen and where, relationship between fwd and aft M, how is it affected by M
when Ml > 1 near max thickness: .0025 mm layer
M before (supersonic) and after (subsonic) = reciprocal
as M increases, shockwave taller and moves aft
Oblique Shockwave
Where, relationship between fwd and aft M
TE of wing, no separation
aft less supersonic than fwd
Bow Wave
Where, relationship between fwd and aft M, when does it attach?
Ahead of wing
aft less supersonic than fwd
normal shockwave at LE
Attach at Mdet
Epansion Wave
What is, when?
High energy flow can go around sharp corners
Increase V outside of turn
Mfs > 1 required
Shockwaves Characteristics Change (6)
Expansion / Normal / Oblique M: + / -- / - Ps: - / ++ / + ρ: - / ++ / + T: - / ++ / + Pt: = / -- / -
Change from TAS to Mach
Changer over altitude
Climb
How does AoA, FPA, Pitch vary with constant CAS, M?
Constant CAS Constant Mach
AoA same increases
FPA decreases decreases
Pitch decreases decreases
Descent
How does AoA, FPA, Pitch vary with constant CAS, M?
Constant Mach Constant CAS
AoA decreases constant
FPA increases constant
Pitch decreases constant
