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how hot are the newer pitots?

rocketbob

rocketbob

Well Known Member
I'm making my own heated pitot for the rocket which I finished machining last night. Only thing I have left is to make a heating element. I have a AN5814 pitot on my -6 that I'm going to check the temperature of, but as I recall they heat to a level thats way overkill and the newer heated pitots such as the Dynon don't get that hot. Can anyone tell me how hot is hot for one of the newer pitots, like when turning the unit on at ambient what the temp rise is?
 
Yes I have but judging by the current draw from looking at the Dynon (10A) its heating up the pitot significantly less than a 5814.
 
melting pitot cover

Hot enough to melt a vinyl pitot tube cover. Don't ask me how I know...
:eek:
 
Over the weekend I had a non-pilot friend over at the hangar and showed him the heated pitot I made. As soon as I said the word "pitot" he started cracking up thinking I said something else....

Anyway...

I don't think these things need to be hot enough to melt plastic to get the job done so I'm aiming for 250 deg F.
 
Pitot cover melting

The pitot cover actually started to melt with the pitot heat having been turned off quite a while before. Just putting the airplane to bed and had been on in flight, parked the airplane and didn't wait long enough for it to cool down before putting the cover on and it started to melt! ooops.
 
Thinking Out Loud...

No experience with heated pitot tubes, just an instrumentation engineer thinking out loud:

Do the newer units like the Dynon use temperature feedback (from an embedded sensor) to regulate the tempurature, or do all of them just run "wide open" all the time? With feedback control I wouldn't think you'd have to run it more than 40 - 50F, anything above freezing with a little margin to handle rapidly decreasing OAT. You might also want some kind of bypass in the event of failure of the feedback circuitry, maybe an OFF/AUTO/ON switch. Display the feedback temp on an EIS, maybe?
 
The Dynon unit does sense the temperature and pull higher draw to heat up but then levels out to maintain the temperature it wants. Not sure what that is or how it does it, but that's what the manual says!
 
An AN5812 pitot will get hot enough to melt solder if turned on without any airflow. I imagine an AN5814 will do the same thing. Not sure what the ultimate temperature limit is in still air, but it's probably not a good idea to leave one on without air cooling. If the Dynon tube regulates the temperature to match the demand, this is a good thing - in safety and also in power consumption.
 
molson309 said:
An AN5812 pitot will get hot enough to melt solder if turned on without any airflow. I imagine an AN5814 will do the same thing. Not sure what the ultimate temperature limit is in still air, but it's probably not a good idea to leave one on without air cooling. If the Dynon tube regulates the temperature to match the demand, this is a good thing - in safety and also in power consumption.
Click to expand...

Yes as I recall the wires in the 5812 are silver soldered. Maybe the things need to be at the same core temperature as the sun if one wants to melt a foot of snow off of it in a few nanoseconds. But, I think since I'll be a little more proactive when theres a chance of encountering icing conditions I think 250 deg. F is more than adequate. Unless someone can convince me otherwise...
 
Pitot Heat Iced over

Well, I do know my pitot tip iced over while heat was ON and I lost AS. If it was during VFR, no biggie, however, it was IMC and I'm still picking seat cushion out! ;) wasn't expecting to loose speed indication-was ready for ice on the RV and had an escape plan though. Diverted to VFR conditions and after a few minutes AS came back. Err on the HOT side is my suggestion.
 
It only needs to be above freezing, but it's got to stay that hot while shedding heat into basically an ice water environment, with the water being changed at 200 mph. It's not the temperature, it's how much energy it takes to maintain that temperature.

Radiators can freeze in cars even while driving....

Charlie
 
It needs to be hot enough to remove ice as well as prevent ice buildup. It will take significantly more heat to remove ice than it will to prevent ice. Err on the hot side.
 
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