12 Total And Polar Drag

Question 1

Vmd

Answer 1

Velocity of minimum drag.

• Point where Parasite and Induced drag lines cross on the Total drag curve.

Question 2

Describe the speed stability states

Answer 2

Speed stable
Speed unstable
Speed neutral

Question 3

Effect of altitude on Total drag curve

Answer 3

Due to the decrease in density at higher altitudes, more speed is required to maintain the same mass flow over the wing.

Therefore against TAS the curve would shift to the right.
- Vmd increases

Against IAS it would stay the same.

Question 4

CD

Answer 4

CD is NOT constant and will vary with speed

CD = CDi + CDp

Question 5

Effect of Flaps on Total drag curve

Answer 5

Flaps / slats extended will increase parasite drag.

Total drag curve will move up and left.

Vmd will decrease.

Question 6

Describe lift to drag ratio

Answer 6

Given by the Polar drag curve.

CL/CD Max = Vmd = 4 degrees AOA

Point at which the tangent line from 0,0 touches the Polar drag curve.
The steeper the tangent the better the lift to drag ratio is.