Menu Sign In Contact FAQ
Welcome to our forums

Why does ice sometimes form on the top of a wing and not on the leading edge?

This is rare but I’ve had it on some occassions. It was clear ice, not rime. It formed just aft of the uppermost point of the wing

Shoreham EGKA, United Kingdom

Interesting. From the location that looks to be around the point where the laminar flow turns turbulent, so perhaps some small droplets which are following the flow just above the wing surface impact here? Just a guess.

Biggin Hill

I recall the temperature was -7C.

Shoreham EGKA, United Kingdom

Could it be due to a pressure change perhaps, a drop may cool it enough to form ice?

Interesting. @Cobalt sounds reasonable. Other theory: Ram rise decreasing? Temperature of fuel? Do you have a picture?

EASA CB IR Training

Could be from cold fuel after a longer flight. I get it sometimes.

Could glycol spread until that point, but not farther?


This was a few years ago and I have no pics. It happened some 30 mins after takeoff.

The temp variation at piston GA speeds is of the order of 1-2C only.

Ice thickness was about 3mm and it covered large areas.

Shoreham EGKA, United Kingdom

I have had this, and I think it is cold fuel. I have only seen it relatively shortly after take off. Peter, was the aircraft outside overnight, or was the hangar heated, or at ambient temperature? Was it very cold overnight?

I have seen the opposite happen which is also easier to explain.

Flying down to Venice last year the OAT was 0C and we were getting a little ice on the wing tips and inboard section but not the fuel tanks. We had filled up the tanks at Dole and the heat from the fuel was just enough to stop the ice forming over that area of the wing.

EGLK, United Kingdom

I am not sure if it is fuel related, my guess 30min after takeoff fuel temps and wing temps will match OAT quickly (otherwise happy to warm up wing & fuel to 40 deg in a heated hangar and use it as de-ice in my non-FIKI aircraft )

Cobalt seems plausible were large supercooled droplets did hit separation turbulence and suddenly freeze, sort of shock induced freezing of supercooled water, the question why did not freeze when impacting the leading edge? my guess this has a thermal explanation: TKS was effective to heat them up just about not to freeze at leading edge but not very effective to raise their temperature so high to avoid re-freezing again on the back of the wing?

Last Edited by Ibra at 23 Mar 12:10
ESSEX, United Kingdom
13 Posts
Sign in to add your message

Back to Top