Basoutos wrote:
Actually the AoA is probably similar to the one in cruise, so the wind would need to be a lot closer to your cruise speed in the configuration than the stall speed. I don’t believe that ground-effect would change that significantly.
True, but, it would be quite possible to raise the nose, by applying elevator input. With enough wind over the horizontal tail surface that should enable you to raise the nose at least a little. Fun question 
Basoutos wrote:
Easy to test: take-off with no back-pressure on the yoke, see at what speed that is actually achieved at lift-off (assuming a flat runway)
Does the trim have any (significant) effect when on the ground?
The trim tab + elevator system works in flight, as a negative feedback control system for maintaining pitch (i.e., for a given load config and power, maintaining airspeed).
But it only works thus if the whole aircraft is free to move in pitch.
On the ground, the trim tab will have only the same effect which it has in flight with a totally jammed elevator i.e. it acts as a tiny adjustable elevator (and it works in the opposite direction to usual 
).
…some of us have variable incidence tail plane trim, just like on a jet…now why didn’t Piper install a Mach trimmer on the Super Cub…
…in a tailwheel you are ideally sitting at stalling AoA on the ground, so a lightly loaded Super Cub should start to levitate with around 40mph winds…
RobertL18C wrote:
…in a tailwheel you are ideally sitting at stalling AoA on the ground, so a lightly loaded Super Cub should start to levitate with around 40mph winds…
That reminds me of the video that was here recently from the Air Force Academy.
Peter wrote:
On the ground, the trim tab will have only the same effect which it has in flight with a totally jammed elevator i.e. it acts as a tiny adjustable elevator (and it works in the opposite direction to usual ).
What do you mean with ‘totally jammed elevator’? The original question was take-off with no back pressure on the yoke … not a frozen yoke.
I also don’t understand why the aircraft can’t move in pitch? How else would you rotate to lift off? The aircraft is free to rotate in pitch both ways on the ground… either as a wheelbarrow, or nosewheel off. The trim will determine how early it lifts off.
I also don’t understand why the aircraft can’t move in pitch? How else would you rotate to lift off? The aircraft is free to rotate in pitch both ways on the ground… either as a wheelbarrow, or nosewheel off. The trim will determine how early it lifts off.
I agree – unless the controls are locked (as they should be).
Peter wrote:
I agree – unless the controls are locked (as they should be).
It was “take-off with no back-pressure on the yoke.” I don’t think controls should be locked for that.
