Originally Posted by
JackD
Rob,
it is not that simple. Power and Speed will affect the angle of attack for a specific stick position... Elevator effectiveness is a function of speed, so you cant assume same angle of attack for similar stick position across the whole flight envelope
Unfortunately, for us RC pilots, stall identification is an art. You feel your stick effectiveness, you see your plane, early behavior, etc etc... But hey!, that is part of what makes it fun!!!
Pete, Sorry to hear about your crash. One question: Did you build the plane, are you sure the wings are true? I really suspect a combination of increased wingloading (fuel almost full) and trying to maintain groundspeed (Yes groundspeed) coming out of a headwind direction to a cross wind one. Again, Groundspeed, we know the airspeed is a different story and it is not affected by changes in direction, other than the energy you lose turning...
BTW, thanks for spotting for me and Steve during our failed attempt at a Sabre formation
Later
Jack
Hi Jack,
I agree that there are factors that vary the exact stick position of the stall slightly and power is one of them as I mentioned in my post.
You are right also that elevator effectiveness increases with speed, but so does the
pitching moment of the main wing. The elevator becomes more effective, but the force required to pitch the wing (to increase angle of attack) also increases.
Since they are both affected similarly by any changes in speed, IE double the speed, quadruple the forces, they tend to cancel each other. Prop wash does have a more significant effect as it usually influences elevator more than the main wing.
The main point of my post is that the stall occurs because the pilot is pulling back on the elevator. Aircraft do not stall themselves and a stall can occur at any speed as it is a function of angle of attack.
Once the pilot realises he actually causes the stall by using too much elevator, recovery and/or prevention is easy.
You can't feel the speed of an RC plane, but you can feel the position of your elevator stick and this is the best clue to avoiding a unintentional stall.