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Icing in VMC (and detecting pitot heater failure)

With a defective pitot heat in IMC you should probably have switched off the AP right away. Bigger airplanes have AP problems when the air data etc is missing ….

Alexis, I like to have some pretty standard procedures wrt things that can kill me.

With pitot heat I see no downside to using it all the time and clear downside to not using it. If things get busy, weather comes in you can forget to turn it on. Of course most of the time that isn’t a problem.

People can do whatever they like – I am just pointing out what I do and why.

Last Edited by JasonC at 27 Nov 08:34
EGTK Oxford

Jason,
i can definitely understand that (and i am considering changing my SOP in that point!). I just wanted to point out that for VFR pilots it does not have the same meaning.
Flying your 172 on a sunny day you don’t p.h. , and using it all summer might have the result to damage it.
5 c only

It’s true that a pitot tube in the prop slipstream in flight would be no good but I can tell you there is a lot of draught from the prop when you are siting on the ground at the pilot tube location.

It would be good if the pitot heat came on only when one is airborne but seeming that is judged to be yet another failure mode, which is probably true.

How can Aeroplus’ near-disaster be explained if the DFC90 uses altitude as well?

Administrator
Shoreham EGKA, United Kingdom

JasonC wrote:

Not only possible but common. Decaying airspeed is the classic sign of piot icing.

Been there, seen that. The thing is that the pitot does not necessarily ice up instantly. The airflow will first be restricted and the AS I show a lower airspeed before it gets totally blocked in which case the ASI will remain at the speed that corresponds to the pressure in the tube.

LFPT, LFPN

On the airplanes I fly the pitot is protected by a thermal switch that turns it off if it overheard and you get an annunciator “pitot off”

LFPT, LFPN

Flyer59 wrote:

I am yet to see an airplane where the pitot tube is in the propeller slipstream! What would that be good for?

The Piper PA28R/PA32R landing gear warning/extension pitot tube is. A very special case, of course.

Last Edited by Airborne_Again at 27 Nov 10:23
ESKC (Uppsala/Sundbro), Sweden

;-)

Yes, and there it makes sense. In all other installations the pitot tube is kept out of the slipstream, of course. And the cooling effect is very small where it’s normally installed.

I am just about to change my checklist though. In planes that are flown both VFR and IFR “always on” seems to be the best way to do it.

Rwy20 wrote:

The expensive TKS fluid that you would put in the plane?

I would expect them to use solution meant for deicing aircraft on the ground, not TKS (depending on what you use, it can be cheaper).

Peter wrote:

If you block the front of a pitot tube in flight, it will not show a change in airspeed.

Yes, Peter, decreasing airspeed is a typical sign of pitot icing.

I turn pitot heat on just before take-off run, too.

Centurion_Flyer wrote:

3) anybody has experience with how much of the de-icing fluid must be sprayed (on average) over a normal GA aircraft (say 182 or 210) to get rid of the ice, which has accummulated on the wings & tail during parking? I am planning some skiing with several overnights parking outside and don’t want to carry the full 20 ltr tank if I would only need…. how much??? for one de-frosting..

I had this situation twice, once really badly, with big frozen drops all over the Wing. In both cases 5L de-ice fluied was fine and 30-120 minutes to get the Ice off.

Last Edited by Cheshunt at 27 Nov 21:02
EDAZ
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