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This descriptive picture popped up in April's AOPA p.103 by author Catherine Cavagnaro. Earlier I had replied to a couple of local Cub pilots who were discussing stall/spins in their PA-18's. "Which way will it roll?" is a common question, especially when low-slow and looking at something of interest on the ground. Like wild game or terrain for landing.
Here's my reply to them. It's mostly right with exceptions as always:
Basically the plane will safely stall in a normal manner providing the T&B ball is centered and ailerons neutral. In straight ahead wings level stalls the nose drops and the higher wing will usually fall off first in a turn but safely. Rudder is the main control surface in a stall, the elevator second. Use the rudder to stop any nose turning and keep the ailerons level while breaking the stall with a lower angle of attack with nose down elevator.
It’ll usually stall and roll away from the ball if the turn is uncoordinated (ball out left plane rolls right; or ball out right plane rolls left) both in a slipping or skidding turn or straight ahead nose yawed condition.
When uncoordinated which ever wing is downwind or further behind the direction of flight usually lets go first. That’s the left in a nose left yaw straight ahead or left skidding turn, and right in a nose right yaw straight ahead or right skidding turn. In a left slipping turn the right wing is downwind and behind and usually stalls first. In a right slipping turn the left wing is downwind and lets go first. There may be exceptions when and how much if the ailerons are deflected in a turn. Nothing is exact in flying.
There are some exceptions to the safe stall in coordinated flight. Obviously aileron position down can stall the wing tip due to higher angle of attack of the wing there, so the aileron position can modify these rules. Even in a coordinated (ball centered) turn the Cub wants to keep rolling into a steep turn (like over about 30 degrees) and we apply down aileron on that low wing to stop that increased angle of the roll into the turn. That wing with the aileron down can stall tip first and the airplane can roll towards the down wing.
Power off stalls and rolls are less violent than power on. Flaps can blank the rudder and elevators some making them less effective. The flapped portion of the wing will stall at a lower angle of attack than with flaps up or the wing tip with ailerons neutral. The plane will fly slower flaps down but stalls at a lower more nose down angle than flaps up.
Maybe.
Gary
Here's my reply to them. It's mostly right with exceptions as always:
Basically the plane will safely stall in a normal manner providing the T&B ball is centered and ailerons neutral. In straight ahead wings level stalls the nose drops and the higher wing will usually fall off first in a turn but safely. Rudder is the main control surface in a stall, the elevator second. Use the rudder to stop any nose turning and keep the ailerons level while breaking the stall with a lower angle of attack with nose down elevator.
It’ll usually stall and roll away from the ball if the turn is uncoordinated (ball out left plane rolls right; or ball out right plane rolls left) both in a slipping or skidding turn or straight ahead nose yawed condition.
When uncoordinated which ever wing is downwind or further behind the direction of flight usually lets go first. That’s the left in a nose left yaw straight ahead or left skidding turn, and right in a nose right yaw straight ahead or right skidding turn. In a left slipping turn the right wing is downwind and behind and usually stalls first. In a right slipping turn the left wing is downwind and lets go first. There may be exceptions when and how much if the ailerons are deflected in a turn. Nothing is exact in flying.
There are some exceptions to the safe stall in coordinated flight. Obviously aileron position down can stall the wing tip due to higher angle of attack of the wing there, so the aileron position can modify these rules. Even in a coordinated (ball centered) turn the Cub wants to keep rolling into a steep turn (like over about 30 degrees) and we apply down aileron on that low wing to stop that increased angle of the roll into the turn. That wing with the aileron down can stall tip first and the airplane can roll towards the down wing.
Power off stalls and rolls are less violent than power on. Flaps can blank the rudder and elevators some making them less effective. The flapped portion of the wing will stall at a lower angle of attack than with flaps up or the wing tip with ailerons neutral. The plane will fly slower flaps down but stalls at a lower more nose down angle than flaps up.
Maybe.
Gary