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Backup battery switch

in 915iS Technical Questions 6 years ago

  • Re: Backup battery switch

    by » 6 years ago

    Wow Bill, you have given me lots of good information. Yes, there is another start switch. It is a momentary push button.
    Since the Backup-Off-Start switch is momentary in the Start position, I understand that the proper emergency procedure, when all alternators fail in flight, is to move the 3 position toggle switch to "Backup" and leave it there. Then press the separate momentary start push button.
    I think that my friend would have been better off installing two separate switches for backup and start. But he already has the switches installed and labeled.
    Thanks again,
    Joe
      
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  • Re: Backup battery switch

    by » 6 years ago

    Hopefully, the two momentary Buttons are close enough to be operated by one hand.
    The other hand will need to be on the throttle.
    Holding Two Momentaries could be a little awkward! especially if one is a Toggle Switch and the other is a Push Button.
    That might work if you can operate the toggle with your index finger and push the button with your thumb.
    The switch layout will need to be carefully thought out.

    I set up mine with a conventional Key type Off/On/Start Ignition switch.
    The ON position activates the start power relays.
    The START position engages the starter.
    I added a flashing Yellow indicator next to the Key to remind me to turn it to OFF after it starts.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: Backup battery switch

    by » 6 years ago

    If both generators fail in flight, how will the pilot know? All he will notice is that engine has quit. Of course the voltage will be low. But that is to be expected with the engine not running. So what is the proper engine restart procedure?
    Switch lanes
    Switch fuel pumps
    Turn on backup switch
    Attempt restart
    ?
    Thanks, Joe
      
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  • Re: Backup battery switch

    by » 6 years ago

    The natural reaction will be to attempt a Normal start with Start Power.
    Once the engine starts the LANE Lamps will remain illuminated due to the failed generators.
    The wise pilot will keep his fingers off the Start Power switch as long as the LANE warning lamps are illuminated.
    The not so wise Pilot may turn the Start Power switch OFF because "That's what he always did".
    Hopefully, he turns the switch back ON before the engine stops, or at least learns from the mistake.

    A Double Simultaneous Generator failure is a once in a Million-hour event probably caused by gross mechanical trauma.
    Something in the engine shattered taking out both generator windings, or more likely from small arms fire from the ground. :ohmy:

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report
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