I think that many know that the 912 can run very rough when the carburetors are out of synchronization by even a relatively small amount. It does not take much to have these engines feel as if they might come off of the engine mounts or even stop running. The other night I was thinking about this behavior and wondering what would happen if I was flying along and had one of the throttles break? Talk about an out of synchronization condition! What would the correct action be for the unlucky pilot? If the carbs were set-up as Rotax recommends to go full-on I guess the thing to do would be to go to full throttle in an attempt to keep the engine in synchronization but I would bet that most pilot’s would do the opposite and pull the throttle off when the failure occurred. It seems to me that this would be a catastrophe in the making and might well stop the engine or worse. If the aircraft set-up was to have the throttle go to idle I doubt that you could go to full power and would have a lot of trouble staying in the air with both carb in sync at idle or relatively near to it. I wonder what folks are instructed to do by their instructors or what recommendations are given to pilots for this situation by the various LSA manuals? Ideas and comments?
  • Re: In-Flight Throttle Failure-What To Do?

    by » 9 years ago

    Hi James,

    I have never had this happen in the air, but I have had it happen on the ground. VIBRATION CITY for sure.
    This has been brought up before and here is a good place to add that if you have a ground adjustable prop which is the most common for us and you have set it up to get 5500 WOT then when you loose one cable and that carb goes wide open and you then freak out from all the vibration the very next quick check is to try WOT. If it goes wide open and smooths out then you know what happened and then you can fly to where ever you want to go to land. If you have the prop pitch to get 5600-5800 rpm WOT then you have 5 minutes of run time to land. Bottom line is you are going to land, for some it will just happen a little sooner than later and the sooner's may not get the best pick of landing spots.

    It would certainly get your attention. :woohoo:

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell

  • Re: In-Flight Throttle Failure-What To Do?

    by » 4 years ago

    I would want full throttle regardless of pitch. If I was over bad terrain, idle would suck big time. Even if I had to go into a climb to stay under 5500 rpm, then I will have more glide distance when I have to shut it down. Generally, I will eventually hit an altitude where the engine won't exceed 5500 even in level flight. So worst case, climb until I have a good landing spot, turn off fuel, glide, and land. On a side note, my s6 with 80hp has been to 17,000 feet.

  • Re: In-Flight Throttle Failure-What To Do?

    by » 9 months ago

    Reviving this thread! Here’s my hypothetical situation. You have a broken throttle cable scenario where you have full power, smooth enough not to overly concern you, but now you need to reduce power to descend or slow down or whatever reason but you really don’t want to shut off the engine and then need to restart it knowing it’s going to instantly jump to full power when it restarts.

    Could you simply switch off one ignition module to reduce power, fly for a while as needed, then switch back on to both ignition modules if you needed full power again, without causing other internal engine problems as a result? I guess this is the long way around of asking does operating a 912 on just one ignition module for a few minutes in flight cause any internal issues to the engine (fuel flooding, wet spark plugs, etc) that would prevent you from quickly returning to full power again? Along the same lines, what if you engaged the carb start circuits, just a bit, to reduce power in order to descend or slow down, what would be the ramifications, if any, of doing so during a emergency situation? 


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