8.3 Theory of Flight

Question 1

What are the four forces acting on an aircraft?

Answer 1

Lift
Weight
Thrust
Drag

Question 2

Formula for moment?

Answer 2

Force times moment arm/length

Question 3

For stable flight where must the centre of lift located?

Answer 3

Behind the centre of gravity

Question 4

Where is the thrust line located?

Answer 4

Below the drag line

Question 5

What is the glide ratio formula?

Answer 5

Forward speed divided by sink speed (triangle S divided by triangle H)

Question 6

What is the vertical element of lift in a turn?

Answer 6

The vertical element of lift in a turn is the force that opposes the aircrafts weight

Question 7

What is the horizontal element of lift in a turn?

Answer 7

The horizontal element of lift acts towards the centre of the turn, it is also the force that pulls the aircraft into the turn

Question 8

What happens to lift in a turn?

Answer 8

Because of the two split components of lift, vertical and horizontal, the lift force is split, therefore it is reduced, so in order to maintain lift the angle of attack must be increased to maintain the same altitude

Question 9

What is load factor?

Answer 9

Also known as G load, it is the resultant force(lift in a turn) divided by the weight

Question 10

What effects the maximum bank angle? (G loading) ?

Answer 10

Passenger comfort and aircraft structural strength

Question 11

During a turn what must be compensated for?

Answer 11

Extra weight brought about by the resultant of the centrifugal force and the weight

Question 12

What is the flight envelope?

Answer 12

The range of combinations of speed, altitude, angle of attack, etc., within which a flying object is aerodynamically stable.

Question 13

What factors effect the flight envelope?

Answer 13

The aircraft gross weight
The configuration of the aircraft (flaps and landing gear position etc.)
The applicable altitude.

Question 14

What is the limit airspeed?

Answer 14

The limit airspeed is a design reference point for the aircraft, and an aircraft in flight above this speed may encounter a variety of adverse effects, including: destructive flutter, aileron reversal, wing divergence

Question 15

What are structural limits?

Answer 15

These are the allowed positive and negative “g” limits of the aircraft

Question 16

What are structural limits based on?

Answer 16

Structural limits are based on the strength of the aircraft structure

Question 17

What is the effect of a large amount of airframe flexing?

Answer 17

A large amount of airframe flexing will lead to permanent deformation (a bent airframe) or component failure

Question 18

What is the effect of a small amount of airframe flexing?

Answer 18

A lesser amount of flexing affects the lifetime of the airframe due to metal fatigue, etc

Question 19

What are structural limits also known as?

Answer 19

Structural limits are also referred to as acceleration limits or limit load factors

Question 20

What is the effect of overstressing the aircraft?

Answer 20

Exceeding the structural limits (overstress of aircraft) may or may not damage the aircraft. Numerous over stresses will shorten the service life of the aircraft

Question 21

What are aeroelastic limits?

Answer 21

These define the maximum operating speeds in both Knots-Indicated Air Speed and Indicated Mach Number of the aircraft

Question 22

What can occur if the aeroelastic limits are exceeded?

Answer 22

Above the Aeroelastic limits, structural damage or failure may occur as well as a loss of stability and/or control authority

Question 23

What is the aeroelastic limit commonly referred to as ?

Answer 23

“Redline Airspeed”

Question 24

What are the ultimate structural limits?

Answer 24

These define the ultimate operating strength limits of the aircraft. Flight operations beyond the ultimate structural limits will result in structural failure of some component of the aircraft

Question 25

What is the percentage of additional strength with regards to the ultimate structural limit and structural limit?

Answer 25

150 %

Question 26

What does lift augmentation acheive?

Answer 26

Lift augmentation increases the maximum lift coefficient in order to reduce the airspeed at take off and landing

Question 27

What do flaps do to the wing?

Answer 27

Increase its camber

Question 28

What does increased camber do to the airflow?

Answer 28

Accelerates the airflow over the top of the wing increasing lift production

Question 29

What is the secondary effect of flaps for the wing?

Answer 29

It re-energises the boundary layer

Question 30

What are the four main types of flap?

Answer 30

Plain
Split flap
Slotted flap
Fowler flap

Question 31

Negative of the plain flap?

Answer 31

The abrupt change in camber can result in airflow

breaking away from the wing surface

Question 32

A split flap is …

Answer 32

More efficient than the plain flap. The

airflow is less likely to break away

Question 33

A slotted flap works by?

Answer 33

Forming a slot as the flap is lowered

also re-energises the airflow

Question 34

A fowler flap works by?

Answer 34

Travels rearwards and downwards, increasing wing area as well as the camber

Question 35

By what percentage does a fowler flap increase the coefficient of lift max by?

Answer 35

Up to 90%

Question 36

How do slats work?

Answer 36

Slats create a slot in the leading edge and this allows airflow to re energise the boundary layer along with having a high cambered cross section

Question 37

What do slats reduce?

Answer 37

The possibility of flow separation at high angles of attack