High Speed

Question 1

Formula for a Mach no

Answer 1

TAS/LSS

Question 2

LSS formula

Answer 2

LSS=39 x square root of the temp in kelvin

Question 3

Speed of sound at 45,000 ft (tropopause)

Answer 3

573kts

Question 4

What happens to the LSS if temp increases

Answer 4

LSS will increase

Question 5

Due to compressibility

Answer 5

Stall speed increases

Question 6

Mfs

Answer 6

Mach free stream number

Can be seen on the flight deck

Question 7

ML

Answer 7

Local mach number, varies due to the shape of the aerofoil

Local mach numbers around an aerofoil

Question 8

3 Categories/flows of ML

Answer 8

Subsonic flow - smaller than 1
Sonic flow - = 1
Supersonic - greater than 1

Question 9

Boundary for high/low subsonic flow

Answer 9

M0.4 or 300kts

Exceed this and you will get compressibility

Question 10

3 speed regions

Answer 10

Subsonic - less than 1
Transonic - mixture of <1 + >1
Supersonic - greater than 1

Question 11

Mcrit

Answer 11

Highest speed you can go without going supersonic

ML=1.0 - transonic
ML=1.01-supersonic

Question 12

Mdet

Answer 12

Mach detachment speed

Question 13

What does drag do in the transonic speed range

Answer 13

Varies with the mach no

Question 14

Impact of swept wings

Answer 14

Have a higher CD in supersonic

Delay the onset of the transonic drag risk

Question 15

Impact on density

Answer 15

Density only changes when the air becomes compressible

Question 16

The sweep angle is the

Answer 16

Angle between the quarter chord line and the lateral axis

Question 17

Increase mcrit by

Answer 17

Low thickness to chord ratio