How to check if pitot heat is working?

PA28 checklist, on the ground – turn pitot heat on, check it straight away with you hand (gets slightly worm), while you check the lights, turn it off.

Slightly warm isn’t going to do much. It should be a lot hotter than that. I used to fly a C210 and among its defects was a slightly warm pitot that used to ice up in flight.

It warms up to really hot if you wait, but you usually don’t wait that much so as not to drain the battery…

One method that would work both in flight and on the ground and would also detect a “slightly warm” situation is comparing ammeter readings with pitot on and off (though in flight it would obviously require turning off the alternator for a few seconds).

I check it on the ground but the obvious problem is that to avoid draining the battery you cannot realistically wait until it’s ‘hot’. So, in essence, I check manually that the heating element is, in fact, working. How hot the thing gets is a different question altogether.

Slightly warm is useless for ice protection, and probably defective. The PA28 ones I saw in my PPL training were like that, and some never got warm at all

The pitot tube should be too hot to hold in the time it takes to walk around the aircraft.

The pitot heat element either works, or not, there’s not really a condition of sort of working. It will take several minutes to heat the pitot to its normal operating temperature. Allowing it to reach full temperature stationary on the ground is unwise, as it may simply get needlessly hot, as it is not being air cooled as it will in flight. The heater usually draws about 5 amps, so may only just display a pointer move on the old ammeters. If you have a digital ammeter, the draw from the heater should show, though you have to know how the ammeter is wired into the aircraft as to whether to look for the reading engine running or stopped (a whole separate discussion).

So, as suggested, turn it on during your preflight, and as soon as you detect it is warm at all, you’ve confirmed it’s working, turn it off. If. after several minutes, you cannot confirm it’s getting hot, have a mechanic investigate. Of course, be cautious, as a “hot” pitot tube will be so hot that it will burn skin. If in doubt subject a candle or crayon to the risk of the test, rather than your finger (or worse, palm!). The operation of pitot heat for a normally operating pitot heat system, in clear flying conditions, will have zero affect on the ASI reading, and cannot be used as a check. There is no “ASI” check in flight for pitot heat operation, other than waiting to see if it ices over. Note, that if the pitot ices right over in flight, and fails to read dynamic pressure any more, the ASI does not necessarily drop to zero, it will just be wrong. Detecting this is very skill based. Depending upon what ammeter you have, and how it is wired, you might be able to check the electrical consumption in flight – but again, if you don’t understand how the ammeter is wired in the plane, that method may not be conclusive. There is no harm in operating the pitot heat, and watching the ammeter. If you can see a pointer deflection, that promising.

As for its effect in flight, if you suspect that you may enter icing conditions, it should be on early, so it is warm before needing to deice. Otherwise, it may have to catch up. Ice can certainly accumulate faster than a pitot tube, recently heated, can melt it. If you’re accumulating ice in flight in a non FIKI airplane, you should be planning a rapid exit with greater urgency.

I wonder if there are different grades of pitot heaters. Mine draws 5A at 24V which is obviously a lot more heat than 5A at 12V.

Slightly warm is usualy a good indication that the battery is at the end of its life not problems with the pitot heater. If you held the pitot head with the engine running it would tell a different story………… but no one does that !