1957 C172 Pitot mast alignment question

Hi - I'm a new owner - The airspeed does not come alive on my 1957 C172 until after I have rotated, and continues to indicate a lower airspeed throughout the flight. On the older models, the pitot mast is only a piece of tubing sticking out of the front of the wing. I suspect that it might be bent slightly out of the airstream enough to read wrong. Should this tube be parallel with the chord line of the wing? Also, it comes out of the wing through an oblong opening that allows approximately an 1/8" to 1/4" of play. Is that common, or should there be a grommet? Do those with older models have any experience with this? Thank you for your thoughts!


  • JgoaviationJgoaviation Flight Captain

    The service manual has a template to check for the correct angle of the tube coming out of the wing. There should be a grommet in the wing that keeps the tube from moving around. You may want to poke your head under the panel and see if anything obvious stands like a cracked line, lose connection, or anything out of the ordinary. I would suggest getting a pitot static check done on the plane to verify that it is not leaking somewhere between the pitot tube and the airspeed indicator. I have attached screenshots from the service manual pertaining to pitot tube maintenance.

  • Scott ShererScott Sherer COO Forum Moderator

    Thanks so much, JGO. Even after alignment the possibility of a cracked tube is fairly high. A pitot / Static check is definitely the right thing to do. Thanks very much for your comments.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Exactly the information I was looking for - thank you so much!

  • JgoaviationJgoaviation Flight Captain

    You’re welcome!

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