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Thread: forced landing-smoke in the cockpit

  1. #11
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    Default Re: forced landing-smoke in the cockpit

    Thanks everyone for the input. When this happened, all that was on was the radio and intercom so no big load. However, up until this day, I have done mostly touch and goes, stalls, etc. so the engine never ran for more than 10-15 minutes or so a full throttle. This day I was out messing around a river so I was at 5500 rpm for over 20-30 minutes so the alternator was putting out full power longer than any other time. I am kind of wondering if this gave the bad connection enough time to to get enough resistance to melt the insulation?

    I think my game plan now is to re-do the connector. I think I am going to solder them to make sure the connection is good. This part of the electrical was done by another builder so I didn't have any input other than checking it to make sure it was right according to the manual.

    The one thing I noticed now is it seems there should be a switch to turn the output from the alternator off. Kind of like a "crow bar" but something I could turn off in case this happens. I always thought that when the master is turned off, it shut all the electrical off but now I realize this is not the case since the alternator is still powering the regulator. After I saw the smoke, I shut the master off and reduced my rpm. The smoke subsided and most blew out during my 2000 fpm slip to the runway. The crazy thing is, in theory, turning the master off did not stop the alternator output so the wire should have continued to burn. I am wondering if reducing the throttle thus reducing the alternator output is what stopped the smoke? Has anyone put a switch in? If that is not a option, is the crow bar just a circuit breaker that I could buy at an auto parts store? I guess a panel mounted C/B would essentially be a switch. If this ever happened again, I could kill the master and pull the breaker. This might be a better option?

  2. #12
    Senior Member Dorsal's Avatar
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    Default Re: forced landing-smoke in the cockpit

    Shutting the master off should remove the load from the Alt, the load at the time of your event may have been charging the Batt. The only place I have seen a switch recommended is after the regulator to disconnect it from the system if it looses it's cookies (also what a crowbar can do). The Alt will not put out much current if there is no load on the Regulator.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  3. #13
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    Default Re: forced landing-smoke in the cockpit

    Interesting. That makes sense. I guess with the load turned off there really would be no need to put switches in.

  4. #14

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    Default Re: forced landing-smoke in the cockpit

    A good crimp is preferred over solder. A soldered joint creates a stress riser at the place where the solder stops. With vibration the wire will break at this location.

  5. #15
    Dave Holl's Avatar
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    Default Re: forced landing-smoke in the cockpit

    My advice for what its worth would be to crimp the connection but get a proper AMP crimper not a cheap crimper from the auto suppliers, if I was more local you could borrow mine?
    Not sure on your wiring but standard practice would be to have a generator field switch this should kill the gen/alternator output when operated!
    Dave Holl
    Building Kitfox MK7
    Rotax 912ULS

  6. #16
    Senior Member War Eagle's Avatar
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    Default Re: forced landing-smoke in the cockpit

    On my plane I installed a solid state switch panel.

    It included a generator field switch for shutting down the output of the Rotax generator just in case you experienced generator related electrical problems in flight. It allows you to keep any needed electrical instruments (and electrical fuel pump) powered up because you don't have to shut down the master.

    The generator field switch is connected to pin C on the voltage regulator. When this switch is shut off your generator output is killed.

    There is a start up and shut down procedure that I follow to make sure the Generator field is turned off after landing and turned on before taxi and take off.

    I concer with others that is very wise to have this feature wired into your electrical system.

  7. #17
    Senior Member Av8r_Sed's Avatar
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    Default Re: forced landing-smoke in the cockpit

    On my 582 installation I have a relay wired in to cut out the lighting coil input to the rectifier. This way I can run purely off of battery or switch in the rectifier circuit. Works fine in ground tests but I'm not flying yet and don't have any long runs on it.

    -- Paul S

  8. #18
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    Default Re: forced landing-smoke in the cockpit

    After speaking to many people, including a tech a popular Rotax repair facility, I am pretty sure it was a bad connection. In fact the tech told me he has seen this same thing several times and actually solders the ends of the wires to the spade connector leaving the crimp to maintain the strain relief on the wire. I have made this repair and will see what the outcome is. I feel pretty sure that it's fixed. When I cut the old connection out, I was able to see the wires moving under the old crimp. I bought a good pair of ratchet crimpers and recrimped all the connections that I could get to. Thanks again for all the input.

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