POF Q4 - Intro to Lift

Question 1

Calculate the lift produced by a wing with an area of 125 m2, CL 0.78, at a TAS of 240 knots where the air density is 0.44 kg/m3.

a.1,235,520 Newtons

b.326,928 Newtons

c.2648 Newtons

d.1,235,520 kg/m3

Answer 1

b.326,928 Newtons

Question 2

Which Aerofoil produces zero lift at zero Alpha?

a.Negatively cambered

b.Symmetrical aerofoil

c.Any aerofoil

d.Positively cambered

Answer 2

b.Symmetrical aerofoil

Question 3

What are the effects of decreased wing thickness?

a.CLmax decreases and the stalling angle decreases.

b.CLmax decreases but the stalling angle remains unchanged.

c.CLmax decreases and stalling angle increases.

d.CLmax increases and the stalling angle increases.

Answer 3

a.CLmax decreases and the stalling angle decreases.

Question 4

CL generally varies with which factors?

a.Alpha, surface area, thickness

b.Alpha and camber

c.Density, velocity, altitude

d.Alpha, thickness, camber

Answer 4

d.Alpha, thickness, camber

Question 5

Which unit is the Coefficient of lift measured in?

a.Joules

b.kg

c.m/s

d.It is a unitless measurement

e.Newtons

Answer 5

d.It is a unitless measurement

Question 6

The lift formula is:
Select one

a.L = 1/2 𝜌 v S CL2

b.L= 1/2 𝜌 v2 S CL

c.L= 1/2 𝜌 v S CL

d.L = 2 𝜌 v2 S CL

Answer 6

b.L= 1/2 𝜌 v2 S CL

Question 7

The terms ‘q’ and ‘S’ in the lift formula are:
Select one

a.q = dynamic pressure, S= area of the wing

b.q =static pressure, S= wing surface area

c.S = square root of surface q=wing loading

d.S = static pressure, q = dynamic pressure

Answer 7

a.q = dynamic pressure, S= area of the wing

Question 8

The critical angle of attack:
Select one

a.remains unchanged regardless of gross weight

b.increases if the CG is moved forward

c.increases if the CG is moved aft

d.changes with an increase in gross weight

Answer 8

a.remains unchanged regardless of gross weight

Question 9

An aircraft is producing 225,000 newtons of lift. The aircraft doubles its airspeed in flight. How much lift is the aircraft producing?

Answer 9

900000

If airspeed doubles then dynamic pressure will increase by 4.

225,000 x 4 = 900000

Question 10

Calculate the speed (in knots) the aircraft is flying given the following information.

Air Density: 0.52 kg/m3

Wing Surface Area: 320m2

CL: 0.82

Lift: 479,639N

Answer 10

163

Using the lift equation:
L = ½ ρ V2 S CL