Equilibrium, Stalling & Spinning Flashcards
What are the 4 forces in flight
Lift
Weight
Thrust
Drag
In un-accelerated level flight;
LIFT equals ??
THRUST equals ??
LIFT equals WEIGHT
THRUST equals DRAG
In what direction does lift force act in relation to the aerofoil
Perpendicular
How does weight act in relation to the earth
Always acts straight down
If an aircraft is banked, what can a pilot normally do to ensure the perpendicular component of lift equals weight
Increase the AoA
What component of lift produces a turning force which “pulls” the aircraft nose in the direction of the bank angle
Horizontal Component
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
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
What force acts opposite and equal to the horizontal component of lift
Centrifugal force
The resultant force of Centrifugal force and weight is known as what
G load
What happens to G load as bank angle is increased
Load Increases
In a steady climb, weight is supported by what
Lift and a component of thrust
As AoA increases, the Center of Lift moves FORWARDS or AFT of the leading edge
FORWARD
As AoA increases, airflow separation beings to occur at the LEADING EDGE or TRAILING EDGE
TRAILING EDGE
Once airflow separation has begun, as AoA increases, separation moves FORWARD or AFT of the leading edge
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
What must happen to recover from a stall
AoA MUST be reduced
For a given clearn aerofoil
Stall occurs at the same AoA irrespective of what
Weight and Speed
The stall for a given clean aerofoil always occurs at the same AoA irrespective of weight and airspeed
3 basic factors that can influence the stall
Ground Effect
Aerofoil shape
Propeller Slipstream
Contaminated aerofoils will INCREASE or DECREASE the stall speed
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
Propeller slipstream can do what to boundary layer separation
DELAY
Low speed/High power may result in lower stalling speed
What effect does tailplane downforce have
Increased effect to TOTAL WEIGHT
What is required if there is an increase in tailplane downforce
INCREASED LIFT
For a given velocity
What happens to stall speed if CoG is moved forward
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
For a given velocity
What happens to stall speed if wing load is reduced (aircraft weights less)
REDUCED
Less load (weight) requires less lift, meaning a reduced AoA for a given airspeed
For a given load
What happens to stall speed if more thrust power is used
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
Assuming no more power available
Why does altitude effect a stall
Increased altitude means less air density and pressure
To maintain lift where there is less density and no more speed available, AoA must be increased
An increased bank angle results in HIGHER or LOWER stall speed
HIGHER
To maintain lift in a bank, AoA is increased. To overcome increased drag from increased AoA, more thrust is applied
What is the formula for the new stall speed with an increase in load factor
New Vs = Old Vs x √ Load Factor
What is the formula for wingloading
wingloading (n) = Aircraft weight / wing area
What is the formula for load factor
load factor = lift / weight
What is the formula for determining stall speed in a turn
Vs (turn) = Vs1 √ 1 / cosӨ
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)
What is a dynamic stall
Stall occuring at a higher critical AoA at which aerofoil normally stalls
Example; sudden vertical upwards gust significantly increases the AoA to the RAF
What % are approach speeds factored by of the landing configuration stall speed
30%
A stall speed in landing configuration is 35 kts. What is the approach speed
45.5 kts
Approach speed factored by 30% of landing configuration stall speed
35 x 1.3 = 45.5 kts
At what margin above the stall speed are stall warners typically designed to operate at
4 kt to 12 kt
What 2 elements must be present for a spin
Spin = Stall + Yaw
In a spin, which wing is more stalled and creates more drag
Down-going wing
Has a higher AoA
Outside wing is travelling faster in the turn
What are the 3 stages of spin stalling
Incipient Stage
Fully Developed Spin
Spin Recovery
What are the stages to recover from a spin
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
When Acrit is exceeded, what happens to the Coefficient of Lift
DECREASES
Once wing is stalled, there is significant loss of lift
Stalling speed (IAS) is dependent upon which 4 factors
- Weight of aircraft
- Center of Gravity
- Load Factor
- Power Setting
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.
