Navy_Flyer,

I still don't know about the airplane keeping the same trimmed airspeed with flap deployment. My experience was that from a hands-off trim of 80 MPH on downwind to hands-off trim of 65 MPH with power off and full flaps deployed had zero change in elevator trim setting with the C-150's I flew. I'd cut the throttle, deploy the flaps, and turn towards the runway. It was a good exercise. I'd cut power and deploy full flaps when abeam the touchdown point and then turn as soon as the flaps hit the stop. I'd use pressure on the yoke to prevent the typical nose-up tendency of the airplane as the flaps came out, but did not alter the trim at all.

The airplane would change its trim airspeed with flap deployment if you did not re-trim the elevator...and that would be because flap deployment changed the complex relationship between all of the surfaces involved.

At any rate, it was a fun exercise to see if you could touch down just beyond the numbers from downwind without having to touch the throttle. My instructor used the full flaps example because he said I could lose all power, engine and electrical at any time, and should learn how to handle the airplane in the 'worst' configuration. Of course, you can't do this if it's bumpy or with much of a crosswind because those conditions mitigate against flap usage, per the Pilot's Operating Handbook.