AA1219 High Speed Flight

Question 1

Define mach number

Answer 1

Relationship between the speed of an object and speed of sound (M = V/a)

Question 2

What is the single factor that determines the speed of sound in air

Answer 2

Temperature. Higher the temperature, greater the speed of sound

Question 3

How does the speed of sound change as altitude increases (standard atmospheric conditions)?

Answer 3

The speed of sound decreases at altitude (lower temperature)

Question 4

In a constant TAS climb, your mach number ___

Answer 4

increases (speed of sound decreases)

Question 5

In a constant CAS climb, your mach number ____ and your TAS ____

Answer 5

Increases/increases

Question 6

In a constant Mach number climb, your TAS ___ and your CAS___

Answer 6

decreases/decreases

Question 7

Define critical mach number (Mcrit)

Answer 7

The free stream Mach number at which some point in the flow reaches Mach 1

Question 8

Define force divergence mach number (FDMN)

Answer 8

The point after Mcrit but before Mach 1 where parasite drag begins to increase dramatically and continues throughout the transonic regime

Question 9

Define wave drag

Answer 9

Increase in parasite drag due to the shockwave forming during transonic flight

Question 10

Define shock stall

Answer 10

Airflow separation at the base of the shock wave that impairs control effectiveness and can cause flutter or buzz

Question 11

What are the three key design features of the T-38 that limit the detrimental effects of transonic flight?

Answer 11

1. Irreversible controls (no flutter or buzz) 2. Large moveable slab 3. Thin, symmetric, swept wings 4. Area rule (coke bottle) fuselage

Question 12

What are the four primary changes to T-38C flight characteristics during transonic flight?

Answer 12

1. High thrust required to sustain airspeed 2. Aircraft more stable 3. Given slab input results in less pitch change 4. No buffet (wingtip vortices)