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Pitot Tube Question

Posted by Chris Card on April 10, 2012 at 7:59pm

I just got one of the new style pitot tubes with combined static & dynamic tubes.

I noticed that if I plug the four holes around the tube and plug the hole at the tip, that there is cross flow of air between the static & dynamic sections.

Is this normal?

I thought that the two parts were supposed to be sealed from each other.

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Replies

  • Tom in NOVA January 13, 2013 at 11:58am

    3692590751?profile=original

    To add to Leo's photos, the photo shows the breakdown of the pitot tube. The arrow points to the area where the leak is. The dynamic pitot tube is not sealed into the end cap, and the end cap is not sealed into the large main tube.

    The crossflow leak seemed really small in my case and not sure if the low pressure of air streaming in as the plane moves in the air would have effected it, but I rather eliminate any potential for a crossflow.

    I am personally not asking for any refund or credit from 3DR, I understand that things may not always work out when you innovate, but this issue seems to be a problem since April 2012 and I do not see it officially being addressed. If the leak is bad enough, it may lead to some crashes or at least countless hours of frustration of tuning.

    I used Leo's suggestion of heating the epoxy at the end. I used a soldering iron.

  • elad orbach January 13, 2013 at 11:08am

    they should offer all the broken 3dr pitot tube owners a replacement or a low price for a fixed pitot

     

  • Vince Hogg January 13, 2013 at 8:50am

    Id bet £50 that every one has this problem.

    Vince (Leos dad)

  • Tom in NOVA January 12, 2013 at 10:12pm

    I also have the same crossflow leaky pitot tube problem and this is Jan 2013!!!  Hello 3DR Robotics/DIY Drones Store, I just bought this two weeks ago and this problem first surfaced in April 2012. Inexusable!

  • Calle December 20, 2012 at 4:23am

    Nice tutorial!

    I received mine 3 weeks ago, same problem as you and then a new replacement 1 week ago and guess what - same problem! None of the pitot tubes cant really work well without this mod right?

    Im doing the same this weekend.

    Thanks,

    Carl

  • Leo Hogg November 9, 2012 at 2:00am

    I received my airspeed sensor a few days ago and I had this same problem. There defiantly should not be any air path between the pitot and static lines.

    I took the thing apart by warming the epoxy at the end with a paint stripper to see what the problem was.

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    The long internal pitot tube is pushed inside the end cap with no attempt to seal it and it is a very sloppy fit.

     3692542588?profile=original

     

    I simply sealed it up with epoxy in assembled again. Its a bit fiddly as the small static tube is very short and its difficult to keep its internal free of epoxy.

     3692542659?profile=original

     

    I either had one that was not assembled properly or, more likely, they are all made this way. Surely everyone would do a blow test before installation?

      

  • Greg Fletcher April 10, 2012 at 8:15pm

    You are right, that shouldn't be. Wiggle the tubes, is there an insufficient solder joint maybe? The pitot tube goes strait thu. The static is the 4 holes on the outside. Or maybe they drilled to far and hit the inner tube. Should be drilled before assembling.

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