Yesterday’s stall test was done with full flap, engine on idle.
I think, from testing after the TKS installation was done, that one gets the left wing drop regardless of flap setting.
I will try the “RHS heavier” next time 
Alan Cassidy, Better Aerobatics
Peter wrote:
full flap
Full flap, effectively “tapers” the wing, so the tips will stall earlier than they would otherwise. It also effects the roll stability. Two contrasting training aircraft to consider are the c-152 and the tomahawk.
This paper local copy also says that changing the profile of leading edge of the profile, changes where the airflow separates. This has a three dimensional effect as if effects the lift distribution across the plan form of the wing. As an example a sharp profile combined with a swept wing gives more lift, and more rounded shape gives more lift with an un-swept wing.
Skip to page 6, is where the interesting stuff starts.
Also, were you stalling flying into wind? I would expect crosswind to have an effect.
changing the profile of leading edge of the profile, changes where the airflow separates.
Yes that is interesting, despite being “heavy stuff”
The TKS panels do make the leading edge “sharper”, but only very little. The leading edge is extended forward by something like 15mm. On a TB20 you would hardly notice, but yes it must change the aerofoil somewhat.
One other side effect is that the stall warning somes on quite a lot earlier, even though the actual stall speed appears unchanged. And yes we have installed the correct (longer) stall warner switch from Socata; many TKS installations have the original one, unsurprising since the STC says nothing about it.
were you stalling flying into wind?
Wind doesn’t affect an aircraft in steady state flight – unless I mis-understand.
Peter wrote:
Wind doesn’t affect an aircraft in steady state flight – unless I mis-understand.
Oh I understand. Only a gust would have an effect then.
loco wrote:
I would expect crosswind to have an effect.
Actually wind should not matter if the ball is centered, say crabbing into a true heading
Of course if the ball is not initially centered because you are flying a fixed track heading on your compass with wing down it will matter…
I was thinking about aerobatic sequences which always have the spin starting into wind. But that may be for other reasons, such as not flying a long distance when waiting for the plane to slow down. Didn’t think that over.
The reason for precision spin entry into wind is, I believe, to show a clean line – with a tailwind the spin axis would drift downwind.
I would suspect that due to tiny inaccuracies in the fabrication and fitting of the TKS panels the aerofoil shape has been changed in a slightly different way on one wing. It only needs to be a fraction, once a wing drop starts it tends to continue, hence how a spin is a stable state.
It certainly only needs to be a tiny difference. I was once demonstrating an aircraft for someone and did a stall, and although I had stalled it before with totally benign results, this time the wing dropped violently into an incipient spin. The difference was a very small non structural tape patch on one wing, where the fabric had been damaged and taped over with duct tape.
