In the Sling TSi POH, 3.8.3, for Generator 1 failure, it says, "in this event Generator 2 output is (or only partially) available to the aircraft systems / charge the main battery.”

However, in the Rotax 915is Operator's Manual, 4.1.1, for Failure of Generator 1, it says, "If Generator 2 is used for supplying the EMS, the airframe will not be supplied with electrical power by an internal generator."


So, which is correct? In the event of Gen 1 failure, can Gen 2 still provide partial power to the airframe, or none at all?

  • Re: Question re: Gen 1 failure

    by » 5 weeks ago

    When Gen A Fails, Gen B is commandeered to power the ECU Bus to allow the engine to continue to operate.
    This removes Gen B from the Airframe Bus and the house loads are then all dependent on the Battery for power.

    Gen B has ~3X the ampacity that Gen A did.  So, While Ben B can easily power the ECU, it has a lot of capacity going unused.

    The Sling POH Instruction is covertly referring to the backdoor procedure that makes it possible to reattach Gen B to the Airframe Bus - - - with Conditions.

    The BACKUP Power switch connects the AIrframe Bus directly to the ECU Bus allowing the Battery to power the ECU in the event of a DUAL Gen Failure.
    However, this connection works in Both Directions.

    It allows the surplus power available from Gen B to be used to Power the Airframe Bus and "Maintain" the battery charge.
    After reducing any unnecessary electrical loads from the Airframe Bus, the BACKUP Power Switch can be activated.
    NAV Light, Strobes, Landing Lights, and other equipment not essential to flight and should be turned OFF.
    It is important that if you are going to utilize BACKUP Power in reverse, you do it soon after GEN A fails.
    If you delay, and the battery becomes significantly depleted, it is possible to overtax GEN B in the attempt to "Recharge" the Battery.
    Lightly Charging and "Maintaining" a fully charged battery is possible.
    Trying to recharge a nearly dead battery that you have been draining for a half-hour will be a problem,

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

    Thank you said by: Mike Tiffee

  • Re: Question re: Gen 1 failure

    by » 5 weeks ago

    Thanks Bill!

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