just wondering what makes my spad combat plane roll to the left when it stalls? is it that the wingtip stalls first? or torque from the engine? warped wings??
i know this is probably a dumb question...but if ya don't ask...

You should hear me when I ask questions!

It is pretty much all of the things you mentioned. In a perfect world with no motor and absolutely dead straight surfaces the airplane would probably stall straight ahead. Put a running motor on the front of the airplane and the propwash ensures that the perfect world is gone. Add some asymmetry due to building and hangar rash and you get it falling off on one side or the other.

Why then to the left? I think the spiral propwash tends to raise the local angle of attack on the left wing and lowering the angle of attack on the right wing just enough to cause the left wing to stall first and the airplane to break to the left.

It could also be due to the fact that Spad airplanes are ugly.

haha thank you Ben...you're absolutely right most SPAD's are ugly!LOL
the real reason i asked this question was because of a hand launch accident that happened with my lastest scratch built 1/12th scale P-40 Warhawk. i chucked it myself-too slow-and it just went immediately into a stall and rolled to the left-into the ground. luckily it is re-buildable-thanks in part to the styrofoam,epoxy resin construction...
anyhoo-there was some discussion with some of my clubmates as to the cause and what happened. myself-i know it was a stall but some people think differently.
also there's talk that the prop i used was wrong-normally we use 9x4 props on an o.s. max .25fx, but this time i used a 10x5 because the spinner was 2 1/2" and i wanted to increase the prop effectiveness by adding MORE prop

>>we use 9x4 props on an o.s. max .25fx, but this time i used a 10x5 because the spinner was 2 1/2" and i wanted to increase the prop effectiveness by adding MORE prop<<

The tips do a lot more in a prop than the hub. Losing an inch of prop near the hub due to the spinner does NOT mean you add any diameter to the prop.

usefulness before cleanliness.

Even in a perfect plane, when the stall first occurs you are in an unstable situation about the roll axis. The plane MUST start rolling to become stable again. The direction it rolls is kind of a tossup if the plane is trimmed properly.

Since your's always goes left, that indicates a possible alignment issue but I wouldn't worry about it.

In your "too slow" hand launch, it sounds like the plane was never really flying. With such small aerodynamic forces, it doesn't make much sense to talk about stability and control.

You need to buy one of those "get strong" fitness machines they sell on TV!

Tom

You could try flying it without the engine running (Oh no!) directly into the wind or better yet on a calm evening and try a gentle smooth stall on purpose. See if it ALWAYS stalls to the left. If so then the engine did not influence THAT stall. Solve THIS stall to the left problem. Then when you have it stalling straight ahead try testing with the engine running. I would assume if you notice a change in stall behavior when the engine was running it would more likely be influencing the behavior.

The plane MUST start rolling to become stable again.

Tom

Don't follow your reasoning. Whilst the aircraft's roll stabiltiy at the point of stall is in jeopardy, a straight ahead stall doesn't require any roll - or yaw - input to correct.

Mike

During a hand-launch, the torque effects of the engine are large compared to the aerodynamic forces of the tail and wing, so the plane rolls to the left. At a recent combat contest, we were launching with a pretty sizeable tailwind, and almost all the scale planes went left on launch. All of my scale launches were knife-edge. I'm pretty sure the wing wasn't really stalled (it wasn't rolling like I see when I do snap-roll), but there wasn't enough air over the surfaces to keep the plane from doing whatever it pleased for the first few heartbeats.

That said, did you check your lateral balance? I find that really messes with my combat planes ALOT.

I disagree that when a plane stalls it will roll one way or the other. My Extra just drops its nose and starts flying again. One wing will drop only if their are differences in the wings to cause one half to stall before the other.

ca-ca.

Is CA-CA any thing like BS????

yes i balanced the aircraft laterally. yet it still rolled to the left..why? i think it has to do with several factors: the prop wash coming back over the fuselage, engine torque, etc..
now what do you do when a combat plane (with only aileron and elevator) rolls to the left? well you add right aileron and hope it recovers. but what does that do? the left aileron goes down and tries to increase the angle of attack of the left wing, and what does that do in a stall? ..makes the stall deepen and yer screwed...unless you have rudder control and can capitalize on the prop wash.
i think that even though i balanced the aircraft laterally, there were still enough differences in it's symmetry to help it roll left.
i have read that the curtiss P-40 warhawk (my combat plane) was a ***** when it came to torque effects. maybe this is a design flaw...damn! i knew i shoulda built a p-51B mustang!

A regular airplane in normal flight is aerodynamically stable in roll, meaning any roll rate will generate a moment about the longitudinal axis to counter the roll. Once the wing stalls, this changes and roll stability is lost. When in a stall, if the wing rolls for any reason, the aerodynamic moments will tend to increase the roll rather than stop it. This characteristic is what makes spins and snap rolls possible.

Once a full stall is entered, the wings won't stay level for long unless you apply corrections to keep them level. Geist mentioned the nose drops on his Extra; that ends the stall and puts you back in regular flight.

Godfrey, I agree with everything you said.

Tom

Godfrey, Why not put a little more elevator deflection on the side that drops the aileron. While this may not be a good fix, if the drop is marginal, it may address your problem.

A regular airplane in normal flight is aerodynamically stable in roll, meaning any roll rate will generate a moment about the longitudinal axis to counter the roll. Once the wing stalls, this changes and roll stability is lost. When in a stall, if the wing rolls for any reason, the aerodynamic moments will tend to increase the roll rather than stop it. This characteristic is what makes spins and snap rolls possible.

Once a full stall is entered, the wings won't stay level for long unless you apply corrections to keep them level. Geist mentioned the nose drops on his Extra; that ends the stall and puts you back in regular flight.

Tom

All agreed - it just isn't what your earlier post implied - that to cure a stall, a roll is needed.

Mike

Mike, OK, I'm bad. Sometimes what we think and what we type are two different things. I wonder how many times THAT has caused mass confusion??

Tom

I wonder how many times THAT has caused mass confusion??

Tom - you and me both!

All the best

Mike