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Thread: Pitot tube kerfuffle

  1. #1
    Senior Member Dave S's Avatar
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    Default Pitot tube kerfuffle

    When perusing an NTSB file relating to a kitfox engine out/substantial damage deal about two years old (CEN17LA065); I found this comment buried in the text ".....The pilot then performed a takeoff from runway 22 and entered a left crosswind, during which the pitot tube rotated sideways resulting in an airspeed indication of 0 knots......."



    Back when we built our Kitfox, I wondered about the potential for this kind of thing to happen as the fixture is a single failure point. That inspired me to make a bracket to secure the pitot tube in addition to the compression fitting.



    Now, I know, we all practice and should be able to operate an airplane without a referring to the ASI, which I do; however, the ASI is a good thing not to fail unnecessarily for a number of reasons.



    Wondering if anyone else has had a deal like this with a pitot tube coming loose?
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  2. #2
    Senior Member HighWing's Avatar
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    Default Re: Pitot tube kerfuffle

    Never experienced it, but thought about it. I cut the ends of the tubing so they fit in a keyway like orientation. Hysoled a hat shaped fitting over the free end of the tube and screwed in place with a connector fitting - o-ring for seal. When tightened - a slight movement off-center is possible, but nothing like even 5 degrees max.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  3. #3
    Senior Member Delta Whisky's Avatar
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    Default Re: Pitot tube kerfuffle

    Dave - I'm not fond of mounting the pitot tube using the standard bulkhead pass through design for two reasons: 1. the reason you've mentioned (I've seen it happen at least twice) and, 2. the two flared joints are prone to cracking; either during the flaring and it isn't caught by the builder or later in life. (I've seen this happen at least two times as well - caught when trouble shooting less than expected airspeed indications.)


    So I use a slightly different approach. I drill out the next size larger bulk head connector (AN832-5D) to accept the 1/4 inch pitot tube, bend it to shape and Hysol it in place.







    Because the bulk head pass through can still turn (someone bumps into it for example), I restrict that as well:







    Then it is on to final installation:






    The connection to the pitot line/tubing is with a piece of silicon tubing; a laboratory grade I buy from Cole-Palmer. I have pieces I bought over 30 years ago and you can't tell them from the new stuff. Call me crazy but this has worked for me in planes past.

  4. #4
    Senior Member jrevens's Avatar
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    Default Re: Pitot tube kerfuffle

    Darrel (Delta Whisky),
    I used silicone tubing on much of my pitot/static system (terminations) also. Over 28 years of experience with it being used that way has shown it to be extremely reliable and trouble free for me. It's very flexible and capable of relatively small radius bends, especially with the larger wall thicknesses, without kinking. It's also very stretchy and excellent for installing over a tube with a larger OD than the ID of the tubing, and "grabby" enough to not even need a tube clamp in most instances. And of course, as you said, it doesn't degrade like most other materials... lasts "forever".
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  5. #5
    Senior Member Maverick's Avatar
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    Default Re: Pitot tube kerfuffle

    Hi, I am building a Series 5 and I have a question. With the 7 the pitot tube system is different, looking at the builders manual. I have the original fitting made of black plastic. I notice on the new models they use metal fittings. I plan to use the original fitting but, I keep seeing something I wonder if is necessary. It looks like folks are making aluminum tubing to fit in the metal fitting and then splicing the plastic hose to the aluminum tube with tygon or something similar. With the original series 5 builder's manual, there is no reference to doing anything like that. I did a test fit of just putting the tubing in the fitting and routing it with a smooth contour and using zips to hold in place:
    Pitot Tube.jpg Is there a compelling reason not to route the tubing this way?

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