Dynon Heated Pitot

Time: 8 Hours

I finally got back to working on the RV. When I built the wings one of the items I planned for was the Dynon heated pitot, for the non pilots it’s the tube that measures the air pressure to determine airspeed and angle of attack. I had installed the mast that would hold the pitot since it needed to be riveted and the hole cut into the wing so it made sense to install this early on. I had also wired for the pitot which includes the power, ground and indication wire. The wiring is for the heat controller that allows the pitot tube to keep ice from forming as you fly through moisture which could freeze on an I heated pitot and block it’s function. First task was about getting the pitot attachment screws drilled, tapped and countersunk.

This pitot has a special function in that it has one hole on the tip to measure pressure indicating airspeed but also has one in the angled face. This hole compares pressure between the two and as the angled ones pressure increases and the tip decreases it can measure the angle of attack, the angle of the wing relative to the air it’s traveling through. This angle of attack or AOA is used to determine when the wing stalls or no longer produces lift.

First up was to determine where the screws need to go. The pitot has some thicker sections on the wall to allow for the screw holes. I transferred where those would line up on a piece of tape I put around the edge so that I could reference them onto the mast.

I also used some electrical tape to help make the fitting tight. I put the pitot tube in place on the mast and used the reference lines on the blue tape to transfer those marks onto the mast. I then used those marks to drill the initial holes after removing the pitot.

I then returned the pitot tube back to the mast and used the previously drilled holes to mark the pitot tube itself. This way I could remove the pitot tube and drill in a more controlled environment as you need to be careful to not drill too deep and hit Bart if the inner tubes or wires.

With the holes drilled in the pitot I could then use my tap for 6-32 screws. I then countersunk the mast to accommodate the screws to be flush.

Once the pitot was secured into place with its new countersunk screws I marked the ends of the aluminum tubes inside the wing so that I would have good clearance. I need to transition from the aluminum tubes to the plastic SafAir pitot/static hose that I had installed a few years ago. I removed the pitot again so that I could cut the aluminum tubes to the final length. I decided to stager them to help with installing the pitot with the fittings installed. I needed to flare the the aluminum tube to work with a compression fitting that allows to transition to the push-to-connect fitting that allows the plastic hose to connect.

The next step was to mount the heater controller. I searched several websites prior to this and decided that I would mount the controller directly to the access panel. This allows for easy installation and removal as needed. So I took some measurements and decided exactly where to mount it on the panel. I made some reference marks and clamped the controller to the panel so I could drill the four mounting holes.

After I had the holes drilled in the panel I went to work on the attachment hardware on the controller. I decide to use nutplates to make installation of the controller as easy as possible. This included drilling for the nutplate rivers and countersinking for the dimples that would be in the panel. Once all cleaned up I riveted the nutplates and dimpled the panel for the #8 screws. Overall a pretty easy process just time consuming.

Now I needed to figure out exactly how to route the wires to make sure they don’t interfere with the aileron bellcrank or the edge of the rib. Once that was decided I started lacing the wires so that they would lay correctly. I also added a couple of adhesive zip tie attach points to help secure the wires.

I laced up the wires that come off the pitot so they look good as well.

The last task is to cut the two plastic lines inside the wing. I had left these long when I installed them a few years ago since I wasn’t sure how they would be routed in the final install. I made some marks where I thought the should end up and cut them about an inch long to start with. After a few trial fits I removed a little at a time to get a perfect fit. I decide to go with two 90° push connect fittings versus bending the aluminum tubes which will all for easy removal of the pitot should it need replacing.

just need to order and install some edge guard along the rib lightning hole to protect the tubing. I also did a pitot test with a 12cc syringe and some surgical hose following the HomeBuiltHelp technique from this video: Leak Testing. My system stayed pressurized and a constant indicated airspeed help for several minutes which tells me I have no leaks. I will test the static side after I crawl into the tail to add a tee fitting. I then tested the heating function of the pitot by powering up the RV and flipping the Pitot switch on. I watched the VP-X screen to see the AMP draw increase indicating the that controller and pitot are drawing power. The indicator I created on the Dynon screen turned green, that’s how I programmed it, to give an indication that the pitot was turned on and is functioning properly. I also tried to use a laser thermometer to see if the probe was actually heating. I could get a good reading so I quickly touched it with the back of my hand. It was hot but not so hot to burn me so that was good enough for me to say it’s working. One more task done on the RV!

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