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Why does the breaker keep tripping when I try to use the flaps in my 1965 Cessna 172G? It’s a 15 amp breaker. After I reset the breaker, the flaps will go up but then the breaker trips when attempting to lower the flaps.

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2 Answers 2

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Something is wrong with your flaps, the wiring leading to them, or the breaker itself. The breaker is tripping to keep your plane from starting on fire. Stop resetting it and have a mechanic look at it.

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    $\begingroup$ Very well said! $\endgroup$
    – Ralph J
    Sep 24, 2023 at 20:39
  • $\begingroup$ Thanks will do. I forgot to mention that after I reset the breaker the flaps will go up but then the breaker trips when attempting to lower the flaps. $\endgroup$
    – C Pruette
    Sep 24, 2023 at 22:59
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    $\begingroup$ Electricity can be very moody if you have a fault somewhere. Any! movement of the plain, even you shifting your position on the seat can shift cables and affect a short circuit, cause the cables move a little and then there is no shortcut anymore, until the next movement. Also these kind of shortcuts are very dangerous, cause they can create an electric arc, which really can set you plane on fire. It's also possible that the flaps are clogged and move with more resistance than they should, especially overcoming initial static friction (in any system) takes a lot of force and hence current. $\endgroup$
    – juwens
    Sep 25, 2023 at 12:48
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    $\begingroup$ We used to say that a tripped circuit breaker is an electrical fire "push-to-start" button. $\endgroup$ Sep 25, 2023 at 16:46
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    $\begingroup$ Thanks everybody confirming the plane has been grounded since first experiencing tripped breaker. $\endgroup$
    – C Pruette
    Sep 27, 2023 at 5:35
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Question: does the breaker open immediately when you command a flap setting, or is it more intermittent ie it occasionally trips when commanding a flap setting? An immediate and instantaneous trip typically indicates a short circuit either in the flap drive motor, the control switch unit or the wiring. Intermittent tripping of the breaker might indicate problems with the flap drive motor i.e. damage to the windings, etc. Either way, the flap system is a secondary flight control and must be functional in order to fly the airplane safely. Therefore cease operation of that aircraft until the flap system can be inspected and repaired by qualified mechanic.

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  • $\begingroup$ Thank you for this. The breaker trips immediately. Trying now to get a mechanic to return my calls. If anybody can refer a mechanic in or near Byron, CA please send me their contact info. Thx. $\endgroup$
    – C Pruette
    Sep 27, 2023 at 5:37

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