Mod 11 - High Speed Flight

Question 1

Whats the speed of sound and the Mach No Equation?

Answer 1

• 761mph / 661knots

- True Air Speed of Aircraft/Local Speed of Local = Mach No.

Question 2

Whats the Critical Mach Number?

Answer 2

• The critical Mach number is the Mach number at which when supersonic airflow begins to occur.

Question 3

Give the four ranges of high-speed flight.

Answer 3

• Subsonic: Below 0.75
• Transonic: 0.75 - 1.20
• Supersonic: 1.20 - 5.00
• Hypersonic: Above 5

Question 4

Whats Buffeting?

Answer 4

• Buffeting is the vibrations felt through the airframe when the A/C is reaching the critical Mach number.

Question 5

What happens when an A/C reaches supersonic?

Answer 5

• As the A/C reaches the critical Mach number, a normal shock wave occurs as the airflow turns supersonic on the upper aerofoil surface. As the A/C gets to Mach 1, the shockwave moves towards the leading edge.

Question 6

2 Ways of Mach trimming?

Answer 6

1 - Moving the fuel around the A/C.

2 - Trimming the horizontal stabilizer.

Question 7

2 Ways to avoid fluttering?

Answer 7

• Mass balancing.

- Stiffer Structure.

Question 8

Why is sweepback bad?

Answer 8

Causes spanwise flow which causes wing tip stall.