Navomatic 300A feels engaded all the time.

Discussion in 'Maintenance Bay' started by eric parks, Sep 13, 2017.

  1. eric parks

    eric parks Filing Flight Plan

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    I joined a flight club that has the Navomatic 300a in there 182. During my preflight the right aileron had a moderate rachety feel ( If that is a word) and the left side had is also, but 50% less. You could also feel it in the yoke. Of course my first thought was the clutch for the autopilot was stuck in the engaged position. I tested the unit on the ground and it performed to the manuals preflight, but again seemed like it didnt disengage when powered down. I had a AP on the field take a look at it and he pulled the inspection plate and said the unit was well lubricated. He also said his experiance with the unit was limited and could tell me if the unit was operating correctly.
    I spoke with some of the senior club members and they say that the feel is normal for the Navomatic.
    Can anybody confirm??????
     
  2. mscard88

    mscard88 Touchdown! Greaser!

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    I dunno but maybe pull the CB and see how it feels, then push the CB back in and see what it's like. Club might have it checked out by an avionics shop if y'all feel it's engaged when it's supposed to be off, or whatever is felt it's doing. That's all I can suggest. Hopefully someone more knowledgable with that model AP will be along.
     
  3. ktup-flyer

    ktup-flyer Pattern Altitude

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    Mine is smooth. Like Mark said, pull the breaker and see if it changes anything.
     
  4. eric parks

    eric parks Filing Flight Plan

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    Thanks for the responses, I just got done pulling the breaker and all is the same.

    Does anyone know of a shop that has experience working on these?
     
  5. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    If it is not disengaged in preflight by either the normal disconnect or pulling the breaker, you have an unairworthy aircraft. You need to have this looked at. The servo may have jammed or even worse, your control cable is binding on something else.
     
  6. 5QK

    5QK Filing Flight Plan

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  7. ktup-flyer

    ktup-flyer Pattern Altitude

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    you'd probably be better off replacing it with something newer. The navomatics are ANCIENT
     
  8. dmspilot

    dmspilot Pattern Altitude

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    Used to fly a 172RG with the 300a. The ratchety feel is normal. There is probably nothing wrong with your plane.
     
  9. eric parks

    eric parks Filing Flight Plan

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    Thank you ll again for all the comments and a special thanks to 5QK. It is highly likely you gave me the answer I was looking for. Will share with the club and have the unit cleaned and lubed.
     
  10. denverpilot

    denverpilot Taxi to Parking

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    The servos do add a little drag in the aileron cables. With both those servos and the bellcranks for moving the flaps and ailerons together on our 182 with the Robertson STOL kit, the two together give a distinct feel both moving an aileron manually during pre-flight and also through the yoke, it's a tad "heavier" in roll.

    I don't think you're seeing a major problem there, just used to the ailerons feeling slightly easier to move.

    We can also feel a slight "ratcheting" as the servo turns. It's more like the feel you'd get turning a stepper motor than a "ratchet". Little "bumps" as it rotates.
     
  11. Skyrys62

    Skyrys62 Line Up and Wait

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    Love this site for this sort of thing...

    btw, how do you interpret this? "bridle cable tension should be 10+3 lbs."
     
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  12. 5QK

    5QK Filing Flight Plan

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    Not to tight, not too loose.
     
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  13. Jeff Oslick

    Jeff Oslick En-Route PoA Supporter

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    We have a 300A in our 182. same. I recall the first time I preflighted a plane with a 300A, and had the same concern as the OP.

    Important - do NOT allow the AP to slam to the stops on the ground, and do not apply much pressure to the yoke on the ground resisting the AP. If you do, you will likely break the servo sheer pin. It is one of the most expensive parts by weight on a plane. Several years ago it was $65 for a part that weighs about 1/3 of a gram. Takes about an hour of A&P time to change out too. Ask me how I know...
     
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