Flight Performance

Question 1

What 2 equations govern the balance of forces in level flight? How do these differ if we also assume steady flight?

Answer 1

T-D=m*dV/dt
L=mg

if steady - T=D

Question 2

What is the equation relating the stall speed to the maximum value of Cl?

Answer 2

sort(2mg/rhoscl)

Question 3

Write the ratio of lift to drag in terms of Cl and Cd

Answer 3

L/D=Cl/Cd

Question 4

What is the condition on the ratio of the lift and drag coefficients to minimise drag?

Answer 4

Cd/Cl is a minimum, Cl/Cd is maximum

Question 5

What is the condition on the ratio of the lift and drag coefficients to minimise power?

Answer 5

Cd/Cl^3/2 is a minimum

Question 6

Assuming that Cd=a+bCl^2 that are the expressions for Cl at minimum drag and Cl at minimum power?

Answer 6

Clmd = sqrt(a/b) Clmp=sqrt(3a/b)

Question 7

Define the safe operating range of an aircraft?

Answer 7

Maximum distance between 2 airfields. taking into account headwind, diversion, stacking, take off, climb and land

Question 8

Aerodynamically, at what flight condition should an aircraft fly at to maximise its range?

Answer 8

Minimum drag condition

Question 9

What are the 4 phases an aircraft undertakes during take off?

Answer 9

Ground run
rotation
flare
initial climb

Question 10

What are the forces acting on the aircraft during the ground run?

Answer 10

Lift
Weight
Thrust
Drag
Rolling Friction

Question 11

What factors affect the take-off distance of an aircraft?

Answer 11

Aircraft weight

Altitude

Question 12

What is the purpose of the rotation manoeuvre during take off?

Answer 12

Increases angle of attack and coefficient of lift until the lift exceeds the weight and lift off is achieved

Question 13

What aircraft motion is used to execute a correctly banked turn?

Answer 13

roll

Question 14

In a correctly banked turn does the bank angle increase or decrease with speed in the turn if the radius of the turn is fixed?

Answer 14

Increase

Question 15

What is the definition of the load factor?

Answer 15

Lift in the turn/weight of the aircraft

Question 16

What value of Cl minimises the radius of a correctly banked turn?

Answer 16

Clmax

Question 17

At what flight condition should an aircraft fly at to minimise the sink speed when gliding?

Answer 17

minimum power condition

Question 18

What 2 performance criteria are we interested in when an aircraft is climbing?

Answer 18

Rate of climb

angle of climb

Question 19

What affect does flying an aircraft at the absolute ceiling altitude have on manoeuvrability?

Answer 19

rate and angle of climb fall to zero.