Turning Flashcards
Explain how the required turning (centripetal) force is generated.
a force toward the centre of the turn must be generated, done by banking the aircraft and tilting the lift force so that it has a horizontal component.
It is this horizontal component of lift, the centripetal force which pulls the aircraft into a turn and keeps it turning.
What is CPF formula?
CPF = Wv^2 / Gr
G = gravity R = radius
Define load factor.
The ratio of the lift force being generated by the wings at any given moment compared to the weight of the aircraft.
LF = L/W
Describe how load factor increases with bank angle
In a turn, lift force generated must be greater than weight so it can produce a VCL to oppose weight and a horizontal component (centripetal force) to provide the necessary acceleration toward the center of the curve.
As lift force is being increased in a turn the load factor thus will also increase as load factor = Lift being generated/weight.
As the bank angle is increased the lift will increase and if lift is increasing the load factor will also increase with increasing bank angle.
What are the load factor increases with bank angle
30-degree bank, the load factor is 1.15 (wings are producing 15% more lift and the pilot will feel 15% heavier
● 60-degree bank, the load factor is 2g (wing is required to produce lift equal to twice the weight to maintain altitude) pilot will also feel twice as heavy.
● At a little over 70-degree bank angle, the load factor is 3g
Explain the connection between load factor and percentage increase in stalling speed.
In each turn with a steeper bank angle, the AoA must be increased to provide the increase in lift needed for the turn.
As aircraft maintains a constant speed, this means that at each AOB, the AoA is closer to stall until at critical stall angle.
Increase in lift needed for turn = LF increase, the amount for the increase in stalling speed in a turn is proportional to LF.
What is turning/new stall speed formula and the percentage increase with each AOB?
Stall speed = basic stall x √load factor
7% = 30º 19% = 45º 41%= 60º 100% = 75º
Explain the conditions for a maximum rate/minimum radius turn
Max Rate - rate of turn is given by speed/radius. So max rate we need highest speed and smallest radius. Aircraft must therefore be flown on verge of stall, with highest airspeed possible and AOB that can be sustained.
Best speed for max rate turn is Va, as above Va LF and AOB must be restricted resulting in lower rate of turn, Below it, they’re naturally restricted by stall boundary layer.
Minimum radius - an aircraft being flown in a level turn at the verge of the stall speed and at the maximum AOB that can be sustained without stalling.
achieved at the design maneuvering speed VA. If aircraft is flown on the verge of the stall above this speed, the aircraft ‘g’ limits will be exceeded. Thus above VA the restriction in load factor and thus angle of bank will cause the radius of the turn to increase above VA.
Explain the effect of wind during:
(a) a constant-bank turn;
(b) a constant-radius turn around a ground feature.
(A) aircraft turning at a constant angle of bank and airspeed, the radius of the turn will be constant.
If a wind is blowing, the flight path with reference to the ground is no longer circular as aircraft and air mass drift.
If angle of bank is maintained, the ground radius of the turn will change, greatest when downwind and least when into wind.
(B) Maintaining a constant radius around a ground feature,(CPF) must be adjusted to allow for the differences in ground speed as the aircraft flies around the turn. Thus the higher the ground speed the higher the CPF(and angle of bank).
In a climbing, descending turn describe the effect on rate of climb/descent
Rate of climb - climbing turn requires a tilted lift vector and increased lift to provide CPF needed to turn which also has an increase in drag as well as lift.
To offset this increase in drag and maintain climbing speed, excess power used in the climb is absorbed by the turn. Less power = less rate of climb. If same speed is maintained, reduction in rate of climb is proportional to AOB used.
Rate of descent - descending turn, drag increases with AOB for the same reason as in level flight and climbing turns.
If the speed for the straight descent is maintained in the turn, the rate of descent will increase, increasing power will compensate for this
In climbing and descending turns, describe the tendency to overbank/underbank
Overbank - tendency to overbank, caused by the outer wing having a higher effective AoA then inner wing.
Both wings travel through the same vertical distance in the climb, but the outer wing travels on a wider arc and therefore through a greater horizontal distance, this results in a difference in angle of attacks between the inner and outer wing in the turn.
Underbank - In a descending turn, this is a tendency for the aircraft to roll out of the turn. The inner wing has a higher angle of attack, and thus generates more lift. This has a tendency to roll out of the turn as a result.
Identify the the factors affecting the radius of a looping manoeuvre
The radius of a looping maneuver is proportional to V^2/g (TAS/load factor).
