Originally Posted by
BMatthews
Consider too that full size aircraft have much higher stall angles of attack than the same design as a model. That old Reynolds number issue again. So if you want a model to be at the stall angle when in a flat 3 point attitude you need to flatten the angle. Models up to around 4 foot span will stall at around 7'ish degrees AoA. The big gas engine models of over 15 lbs and at 100 inch span and bigger will stall at a more full size angle of up around 10'ish degrees. Meanwhile the full size stall angles are likely up around 15 or more degrees. That's why we see airliners "gliding" in at around a 10 to 15 degree glide slope even with their nose well up in the air. For that size and at that sort of Reynolds number the stall angle is way up well over 15 degrees. We simply can't match that with our models.
So in the end if we can land a Spitfire or Mustang model of modest to medium wing span with a nice 3 point landing it's likely that we timed the stall to the landing "just so". The model was in the process of stopping and pitching down just as the wheels touched down. But a landing without this sort of well time aggressive stall for a model will need to be a rolling landing. We just can't NOT end up with a lot of bouncing otherwise other than by sheerest luck.
BMatthews is right about the different stall angles of models due to the lower Reynolds Number. I think he is right that a model of a taildragger (e.g. P-51 or Hurricane) will stall before the tailwheel touches, but if it is done correctly, an inch above the ground, the model will still settle neatly in a smooth looking landing.
Slapping a taildragger onto the ground at a speed way above its stalling speed will always result in a mighty bounce.
When learning to fly on a taildragger (Chipmunk) we always tried for a 3-pointer. The secret is speed control, and the secret to that is Trimming. Most model pilots approach too fast, and most do not retrim for a correct approach speed. They leave the trim set for high speed cruise (or even full throttle) and then fly the approach with a handful of up elevator. That is very hard to do accurately (and would earn a severe b*ll*cking from an instructor on full size).
BTW BMatthews, I am surprised that I have to correct your statement
"That's why we see airliners "gliding" in at around a 10 to 15 degree glide slope even with their nose well up in the air."
Airliners ALWAYS approach at an angle of 3 degrees. ALL ILS glideslopes, and PAPIs and VASIs are set at 3 degrees. The reason the nose is well up in the air is because they have LE slats. Watch the traffic at a busy airport and you can spot airliners that use flaps (all of them) but no slats (very few) by the nose down sit in the air on approach.