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Replacement of a stall warner with a heated version - N-reg TB20?

I have found out that the TKS system which I have on order won’t have a heated stall warner.

What is the paperwork route required to certify a heated replacement?

Obviously there is the wiring and a CB but that’s easy, and one could wire it to the heated pitot CB. I am thinking of type certificate related issues.

Are there other issues e.g. it really should not be switched on until flying – like the AoA sensors on jets which actually get damaged if left on? The heater on the pitot is sufficiently far away that it doesn’t damage anything if left on.

Administrator
Shoreham EGKA, United Kingdom

I’m sure you know the full process very well…. there is this FAA guidance that others may find interesting:

http://www.faa.gov/documentLibrary/media/Order/8300_16.pdf

EGPD / OMDW / YPJT, United Kingdom

Be sure to have it OFF on the ground. They are really fragile, basically it is just a thin heating wiring wrapped around a non heated one, on the most common GA ones. So it damages itself (wires going open) or softening the whatever is used to glue the wiring in place.

Last Edited by Jesse at 20 Oct 05:34
JP-Avionics
EHMZ

Yes I know the basic process but there are many exceptions.

Thanks Jesse. I will investigate. We had this discussion in one of the AOA indicator threads e.g. here and this is a huge issue there because the heated AOA sensor (and an unheated one is a waste of money IMHO) will set the paint on fire in no time at all, with its 200W heater… I would have installed a simple temperature switch, as discussed in the thread, to protect it.

Edit: how about interlocking the heater to the landing gear? Seems really obvious. Maybe it isn’t desirable in case of a freezing OAT departure?

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

Edit: how about interlocking the heater to the landing gear? Seems really obvious. Maybe it isn’t desirable in case of a freezing OAT departure?

This is normally the case, as well as a temperature protection. I am unsure on the power of the one showed, I doubt It would by anywhere near 200 Watt. The biggest problem seems to be either burning out the element and/or softening the glue, leaving the wire exposed / loose, such that the connection will break.

JP-Avionics
EHMZ

I would control the heater from the air/ground switch on the landing gear but be sure to write an aircraft jacking check list so you remember to trip the CB before you jack the aircraft for maintanence.

This is my existing one. I wonder if there is a heated version of the same dimensions?

Administrator
Shoreham EGKA, United Kingdom

What’s actually behind the panel? Is it a certified stall warn sensor such as a Safeflight unit or something like this?

Avionics geek.
Fairoaks. EGTF

This is from the IPC:

From the fact that the microswitch itself is listed separately, it looks like something Socata fabricate.

Administrator
Shoreham EGKA, United Kingdom

That’s a shame – not a standard item from another aircraft type. Perhaps something from a Navajo or similar could be made to work if the faceplate could be swapped to keep the correct leading edge profile, but of course you’d need approved data!

Avionics geek.
Fairoaks. EGTF
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