Aircraft in Equilibrium - Answers T=D, L=W, Mcg = 0
Longitudinal Trim and Static Stability Conditions - Answers 1. Cm0 > 0
2. Cmalpha < 0
3. Cl must fall within the flight range of the airplane
Neutral Point - Answers Location of CG where Cmalpha = 0
Static Margin - Answers SM = xn - xcg
Static Stability Conditions - Answers 1. CG must be ahead of the neutral point
2. SM must be positive
Effect of CG Location - Answers as CG moves aft, Cm stays at the same point and CG rotates radially
upward
Effect of Elevator Position - Answers As elevator position becomes more negative, the slope remains
the same and Cm becomes higher.
As elevator position becomes more positive, slope remains the same and the Cm becomes lower.
Conditions for Isentropic Flow - Answers Flow must be adiabatic and no shocks
Quantities constant across oblique shock - Answers Enthalpy and Total Temperature
Quantities that increase across oblique shock - Answers Static Pressure, Static temperature, and
density
Quantities that decrease across oblique shock - Answers Mach number and velocity
What does the Prandtl-Meyer function give us? - Answers hypothetical deflection angle from sonic
state to current Mach number
What is Prandtl-Meyer the consequence of? - Answers 1. Tangential Momentum Conservation
2. Smooth flow turning
3. Adiabatic, isentropic flow
How do flow properties change in P-M expansion? - Answers 1. Velocity accelerates
2. Mach number increases
3. Static pressure, temp, and density decrease
4. Stagnation properties remain constant
What does SWBLI stand for? - Answers Shock Wave Boundary Layer Interaction
Solution for Homework 11, Problem 4 - Answers Supersonic Linear Theory
Where is AC located in supersonic flight and how does this compare with the low-speed thin airfoil
case? - Answers It is further towards the trailing edge (approximately at the 1/2 chord location)
Supercritical Airfoils Qualities - Answers 1. Shape flatter; shock farther back
2. Supersonic region closer to airfoil
3. No shock at design condition
4. Generally weaker shock; milder separation
5. Drag reduced; drag rise delayed
More Supercritical Airfoil Qualities - Answers 6. Pressure distribution flatter (Rooftop shape)
7. Blunter nose: quicker pressure rise at LE
8. Lower pressures on lower surface due to thickness
9. Rear highly cambered to make up for loss of lift
10. Pitch-down moment because most lift from TE region
11. Strong adverse pressure gradient near TE
Swept Wings Qualities - Answers 1. if normal Mach > critical Mach the pressure distribution is like a
subsonic flow even if freestream Mach > critical Mach
2. Drag divergence delayed to higher Mach number
3. Any shock waves that do appear are weaker
Normal Mach component - Answers Freestream Mach*cos(angle between freesteam and airfoil)