Pitot Heat

Ralph925

Ralph925

New member
There I was (because all good airplane stories start that way) in the clear at 7000 ft heading back to Michigan from a drizzly West Virginia. In front of us the weather is slowly rising up into the flight levels. The tops eventually rise past our altitude putting us in the very wet cloud tops and rain is running up the windshield. I reached down and flipped on the Pitot heat. After a few minutes I am horrified to see the rain stop moving up the windshield, the temperature has dropped well below the forecast temp, we are covered in clear ice, and I am talking to ATC. In spite of my best attempt to use my “right stuff” voice I sound panicked at I ask for higher. Cruisemasters climb well and in a few minutes we are at 9000ft in a beautiful frozen world of glittering snow crystals. About this time I can smell the very sharp odor of hot wires. Because the pitot heat is the last thing I turned on I turned it off and the smell slowly subsided, the amp meter shows charging and everything else is working (except my “right stuff radio voice” is now totally broken) so I keep heading home. The rest of the flight was uneventful and the sky was clear at home.

When I turn on the pitot heat is draws 20 amps. That seems like a lot to me. What is is supposed to draw? Are the heaters replaceable? Why do things have to break when you are already in over your head?
 
My Pitot heat intially draws 20 amps and drops down to ~11 amps as it heats up. Haven't really had to use it much,and considering that I have a 25 amp gen, hope I don't really need it. I'd be pushing my poor old gen for all it's worth if I had the p heat on and nav lights, strobes, radio and txpr. I'd be drawing some off the battery initially.
 
That’s interesting, maybe I just have a corroded connection to the switch. I will check the switch and wires to it this evening. That is a lot of amps for the Gen to support. With that much power it should deice that part of the wing as well;)
 
After cleaning the somewhat corroded contacts, the switch still got way to hot with the pitot heat on. So I took the switch out and got a magnifying glass to look at the numbers. The switch is rated at 6A-125VAC. It is not DC rated or is it anywhere near the 20A the circuit carries. I have replaced it with a very nice new (sort of expensive for a switch) toggle switch rated at 20A DC. On a test flight last night the wiring stayed cool and the pitot hot. :D
 
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