High Speed Flashcards
Mach number =
TAS/LSS
LSS=
TAS/Mach
39 x square root of the temp in K
How does compressibility effect the stall speed
Increases it
Mfs
Mach number, can be seen in the f/d
ML
Local mach numbers, varies due to a/c shape
3 categories of ML
Subsonic <1
Sonic = 1
Supersonic >1
3 speed regions
Subsonic - all ML are less than 1, above 0.4 and compressibility will occur
Transonic - mixture of ML that are sonic, subsonic and supersonic
Supersonic - ML are all greater than 1 and the whole a/c is supersonic
Mcrit
Highest speed you can reach without going supersonic and a shockwave occurring
Border of subsonic and transonic speed region
Mfs number
Normal shockwave facts
Perpendicular to the flow Only forms in the transonic region only Supersonic infront, sub behind Gets more powerful with speed Most violent Thickness, 0.0025m never changes Extends to a greater height with faster speed Can get a wave in front of the leading edge
Oblique shockwave facts
Forms on the trailing edge Supersonic infront and behind Not as violent as normal Only occurs at mfs >1- transonic region Stretch on forever due to less energy transfer and travel at the same ground speed of the a/c across the ground Faster we go the angles reduce
Mdet
Speed where the bow wave attaches to the leading edge, the whole wing is supersonic
Bow wave
A normal shockwave before the leading edge with oblique on each side
Cone
Have to make sure all control surfaces are in the cone
Sinu = 1/mach no
Cone angle = angle from the oblique wave to the flight path
Expansion wave
Airflow is forced around tight corners of the a/c, creates wave
Changes in mach, ps, density, temp and pt with an expansion wave
Mach increases
Ps,density, temp decreases
Pt remains the same
Changes in mach, ps, density, temp and pt with a normal/oblique wave
Mach decreases
Ps,density,temp increases
Pt,decreases
Climbing/descending beneath the tropopause
C,T,M
Climbing and descending in the isothermal stratosphere
C,TM
Climbing and descending in the ozone layer up to the stratospause
C,M,T
Climbing below change over CAS
AoA constant
FPA decreases
Pitch decreases
Passing the change over altitude when climbing to mach
AoA increases
FPA decreases
Pitch decreases
Descending above the change over in mach
AoA increases
FPA in decent - steeper
Pitch - decreases
Descending below the change over in CAS
AoA, FPA, pitch remain constant
In the event of failure of the mach trimmer what must be done
Mach speed must be limited
Temp behind an oblique shockwave
Higher than in-front of it
The push over manoeuvre
LF is less tan 1, stall speed reduces
Reduces the value of the low speed buffet and increases the value of the high speed buffet
Vortex generators
Decrease wave drag
Reenergise the boundary layer
Increasing sweepback
Increases the mach drag divergence number
Through an expansion wave heat happens to LSS
Decreases
