1. High Speed Flight
Chapter 7

2. Pressure Change
Pressure change affect the density of air pressure in its vicinity
At low speeds ( mph) the density change is slight
In low speed flight, the air is incompressible meaning that the density of the air flowing over the aircraft does not change from the surrounding ambient air

3. Supersonic Flight
The Bell X-1 was the first taken to supersonic flight by Chuck Yeager Oct. 14, 1947.
The significance of the speed of sound is that sound is due to pressure disturbances in the air.
We hear sounds because of pressure disturbances being transmitted to our ears in wave like fashion through the air.

4. Mach Number M= true airspeed/speed of sound M < 1 = subsonic
M > 1 = supersonic
M= 1= sonic
M < 0.8 = subsonic
M= 0.8 to 1.2= transonic
M= 1.2 to 5.0= supersonic
M> 5.0= hypersonic

5. Shock Waves
Figure 7-2 A B C
Mach Wave
Shock Wave
Oblique Shock Wave

6. Critical Mach Number
Critical mach number is the value of the free stream that causes the flow to reach mach 1 somewhere on the airfoil.
Figure 7-4A B
Bow wave

7. Wave Drag
Wave Drag is the combined effect of energy loss across and the wake formed behind the shock wave.
At speeds slightly above critical mach number is due mostly to the energy dissipation.
Figure 7-5, 7-6, 7-7

8. Swept Wings Swept wings allowed for high critical Mach numbers.
Swept wing pros
Swept wing cons

9. High Speed Airfoils
The ideal supersonic airfoil is one with a sharp leading edge.
Very poor low speed characteristics
Used for military fighters & missiles
Another desirable trait is to have the point of maximum thickness far back on the airfoil.

10. Control Problems
Shock wave can cause separation to occur on the airfoil surfaces and form small wakes behind.
Vortex Generators
Supersonic flight at the junction of stabilizer and elevator can form a shock wave that prevents any influence of the elevator on the stabilizer.
All moveable surfaces

11. Area Rule
Richard Whitcomb experimented with many wing-body shapes in a high speed wind tunnel.
Whitcomb found that for a low aspect ratio the drag rise in the transonic region.
Figure 7-16
Sears-Haack/Coke bottle

12. Hypersonic Flight Traveling at above or below Mach not as good. Why?
Aerodynamic effects
Aircraft Concepts
Propulsion Systems

13. Please take out a sheet of paper Include today’s date and your name
Quiz on Chapter 7
Please take out a sheet of paper
Include today’s date and your name

14. Quiz on Chapter 7 What is a critical Mach number?
List and explain one advantage and one disadvantage to the swept wing.
Explain the purpose of a vortex generator.