Equilibrium, Stalling & Spinning

Question 1

What are the 4 forces in flight

Answer 1

Lift
Weight
Thrust
Drag

Question 2

In un-accelerated level flight;
LIFT equals ??
THRUST equals ??

Answer 2

LIFT equals WEIGHT
THRUST equals DRAG

Question 3

In what direction does lift force act in relation to the aerofoil

Answer 3

Perpendicular

Question 4

How does weight act in relation to the earth

Answer 4

Always acts straight down

Question 5

If an aircraft is banked, what can a pilot normally do to ensure the perpendicular component of lift equals weight

Answer 5

Increase the AoA

Question 6

What component of lift produces a turning force which “pulls” the aircraft nose in the direction of the bank angle

Answer 6

Horizontal Component

Question 7

If an aircraft is climbing with level wings at a given rate of climb and a bank is introduced, what will happen to the rate of climb

Answer 7

DECREASES / REDUCED
Lift no longer equals weight as lift acts perpendicular to the aerofoil, which is now banked.
Another component must compensate i.e. increased AoA or increased thrust

Question 8

What force acts opposite and equal to the horizontal component of lift

Answer 8

Centrifugal force

Question 9

The resultant force of Centrifugal force and weight is known as what

Answer 9

G load

Question 10

What happens to G load as bank angle is increased

Answer 10

Load Increases

Question 11

In a steady climb, weight is supported by what

Answer 11

Lift and a component of thrust

Question 12

As AoA increases, the Center of Lift moves FORWARDS or AFT of the leading edge

Answer 12

FORWARD

Question 13

As AoA increases, airflow separation beings to occur at the LEADING EDGE or TRAILING EDGE

Answer 13

TRAILING EDGE

Question 14

Once airflow separation has begun, as AoA increases, separation moves FORWARD or AFT of the leading edge

Answer 14

FORWARD

Airflow separation begins to occur on the upper surface trailing edge, moving forward along the upper surface towards the leading edge ias AoA increases further

Question 15

What must happen to recover from a stall

Answer 15

AoA MUST be reduced

Question 16

For a given clearn aerofoil

Stall occurs at the same AoA irrespective of what

Answer 16

Weight and Speed

The stall for a given clean aerofoil always occurs at the same AoA irrespective of weight and airspeed

Question 17

3 basic factors that can influence the stall

Answer 17

Ground Effect
Aerofoil shape
Propeller Slipstream

Question 18

Contaminated aerofoils will INCREASE or DECREASE the stall speed

Answer 18

INCREASED

INCREASED meaning the onset of stall will happen faster at a given airspeed
i.e. 100 kts airspeed, stall WAS 50 kts, NOW 80 kts

Question 19

Propeller slipstream can do what to boundary layer separation

Answer 19

DELAY

Low speed/High power may result in lower stalling speed

Question 20

What effect does tailplane downforce have

Answer 20

Increased effect to TOTAL WEIGHT

Question 21

What is required if there is an increase in tailplane downforce

Answer 21

INCREASED LIFT

Question 22

For a given velocity

What happens to stall speed if CoG is moved forward

Answer 22

INCREASES

Forward CoG creates a pitch down tendency
CoG is forward of the CoL (Center of Lift)
Nose down tendency requires MORE tailplane downforce
More downforce = increase in total weight
For a given speed, only way to maintain lift when weight increased is increase AoA
Increased AoA brings it closer to Acrit, meaning it will be reached sooner

Question 23

For a given velocity

What happens to stall speed if wing load is reduced (aircraft weights less)

Answer 23

REDUCED

Less load (weight) requires less lift, meaning a reduced AoA for a given airspeed

Question 24

For a given load

What happens to stall speed if more thrust power is used

Answer 24

REDUCED

Thrust includes a vertical vector.
More thrust increases velocity
If velocity increases, overall lift will increase
To maintain steady flight with increase velocity, Less AoA is required to provide lift

Question 25

# Assuming no more power available Why does altitude effect a stall

Answer 25

Increased altitude means less air density and pressure ## Footnote To maintain lift where there is less density and no more speed available, **AoA must be increased**

Question 26

An increased bank angle results in HIGHER or LOWER stall speed

Answer 26

HIGHER ## Footnote To maintain lift in a bank, AoA is increased. To overcome increased drag from increased AoA, more thrust is applied

Question 27

What is the formula for the new stall speed with an increase in load factor

Answer 27

New Vs = Old Vs x √ Load Factor

Question 28

What is the formula for wingloading

Answer 28

wingloading (n) = Aircraft weight / wing area

Question 29

What is the formula for load factor

Answer 29

load factor = lift / weight

Question 30

What is the formula for determining stall speed in a turn

Answer 30

Vs (turn) = Vs1 √ 1 / cosӨ ## Footnote Vs (turn) is what we want to determine Vs1 is stall speed in straight and level flight Wing loading in a turn is 1 / cos (angle of bank)

Question 31

What is a dynamic stall

Answer 31

Stall occuring at a higher critical AoA at which aerofoil normally stalls ## Footnote Example; sudden vertical upwards gust significantly increases the AoA to the RAF

Question 32

What % are approach speeds factored by of the landing configuration stall speed

Answer 32

30%

Question 33

A stall speed in landing configuration is 35 kts. What is the approach speed

Answer 33

**45.5 kts** Approach speed factored by 30% of landing configuration stall speed 35 x 1.3 = 45.5 kts

Question 34

At what margin above the stall speed are stall warners typically designed to operate at

Answer 34

4 kt to 12 kt

Question 35

What 2 elements must be present for a spin

Answer 35

Spin = Stall + Yaw

Question 36

In a spin, which wing is more stalled and creates more drag

Answer 36

Down-going wing Has a higher AoA ## Footnote Outside wing is travelling faster in the turn

Question 37

What are the 3 stages of spin stalling

Answer 37

Incipient Stage Fully Developed Spin Spin Recovery

Question 38

What are the stages to recover from a spin

Answer 38

Power to idle Centralise flying controls Full OPPOSITE rudder Control column forward Once spinning stops, centralise controls Recover from dive (pull back gently) Reset power

Question 39

When Acrit is exceeded, what happens to the Coefficient of Lift

Answer 39

DECREASES ## Footnote Once wing is stalled, there is significant loss of lift

Question 40

Stalling speed (IAS) is dependent upon which 4 factors

Answer 40

1. Weight of aircraft 2. Center of Gravity 3. Load Factor 4. Power Setting ##FOOTNOTE If aircraft weights more, stall speed increases as more AoA needed to create same lift If centre of gravity is forward, more downforce required to keep straight and level. More downforce = more weight = more lift through increase AoA More load = more weight to lift. Means more AoA needed to increase lift. Increased AoA means increase of stall speed Less power means less airspeed. Less airspeed needs more AoA to maintain lift.