Heated Pitot Tube Question

I purchased this AN5812 heated pitot tube (P.H. 502-12) on VAF about four years ago. Am doing the electrical (finally), and was wondering how I should do the electrical/tube hookup? I hooked up the pitot tube to a battery and she gets hot quick.

ACS has a phenolic connector receptacle for about $60.00http://www.aircraftspruce.com/catalog/inpages/pitottubeconnect.php . I have seen others with this plugged in. I suppose this is required vs connecting the wires to the probe with a regular connector (maybe gets too hot)?

As far as the tube goes, I'm guessing I might have to get a stainless steel pressure fitting (to accept an AN-4 fitting) and get it brazed on? I plan on making this pitot run with aluminum tubing.

The main reason for the post is to see if anybody has had to start from this point like I am, and what they did? Don't know where to get the pressure fitting with a tube already connected? Maybe at the local fitting store (Parker). Do I need the phenolic connector? Any previous experience info on this would be appreciated. Thanks. Dave

PS. Is it ok to paint the pitot heat, or will the paint just peel away from the heat? I could maybe bead blast it to clean it up --don't know if it's stainless, but don't think it would rust (can't imagine)?

Pitot

db8 said:

PS. Is it ok to paint the pitot heat, or will the paint just peel away from the heat? I could maybe bead blast it to clean it up --don't know if it's stainless, but don't think it would rust (can't imagine)?

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As for the paint: Go to an airport and look at several certified planes. I think that you will find none are painted. You are correct it will blister off and be UGLY. The metal polishes up nicely.

I purchased the electrical connector as it does get hot around the contacts and the connector is designed for that heat. As for the connection to the actual pitot pressure tube it is not as hot. Cessna uses some sort of nylon or other plastic material for the connection. The one in your second picture appears to be well built but possibly over built when compared to Cessna's hook up. I might even be concerned about metal fatigue of the tubing with those heavy brass connections waving around unsupported over time. That may be why Cessna uses "nylon" connectors? Anything that would not leak and withstand warm temps should be OK.
It is very helpful to have the fitting brazed onto the pitot pressure tube so that you can connect your line easily and securely. That is the point where Cessna starts the "nylon" lead.

gvgoff99 said:

As for the paint: Go to an airport and look at several certified planes. I think that you will find none are painted. You are correct it will blister off and be UGLY. The metal polishes up nicely.

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I disagree, I see a lot of painted pitot tubes on mostly Cessna aircraft and quite a few experimentals. However, the paint DOES chip away after a few years (usually due to the heat). I think a bare tube looks much better than a painted one.

Powder coat

TCONROY said:

I disagree, I see a lot of painted pitot tubes on mostly Cessna aircraft and quite a few experimentals. However, the paint DOES chip away after a few years (usually due to the heat). I think a bare tube looks much better than a painted one.

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Powder coated one on a C310 before. Used a silver color. Worked fairly well, but even then over time you might see some discoloring.

I cut off the nut and flare at the end of the tube coming out of the pitot tube, am using 1/4" rigid plastic airbrake tubing which fits very snugly over that. A small 1/4" tube clamp will hold it in place. Eliminates ALL of the fittings shown in your 2nd photo. Heat is not a concern as stainless conducts heat very poorly and the nylon is several inches away. Not flying yet.

Excellent customer support

I called Aero Instruments (who is the manufacturer), and they totally took care of me. They had all the parts and were just super. They have excellent customer support (kind of nice to find now-a-days).

I made a bonehead mistake. I thought I'd polish it, so I used a polishing wheel (what I thought was lightly). I ended up blowing through the thin coating. They couldn't help me with that at Aero, so I'm most likely going to powder coat it. There is suppose to be a high temp version of that. Another guy said I could ceramic coat it. Any thoughts on any of those two? Thanks. Dave

I have powder coated...

...a number of non-structural parts on the a/c, but personally would not do this to a heated pitot tube. The powder coating will discolor with high temp (check with your supplier), and if it does not, then you need to think about any insulating qualities that the coating may add to the pitot tube.

The ceramic coating do act as an insulator and will tend to keep the heat "in" the tube. If ice were to form on the outside, the ice reduction properties of the pitot tube may be compromised.

If you are up to an experimentation task, it would be nice if you could plot the temperature vs time vs airflow of a before and after coating effort.