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Sprung Open/Close Throttle Carb System

in General Tech Discussion 12 years ago
Hi,
From the Rotax 912 installation manual, Rotax recommend the sprung open throttle system for the fail-safe.
I agree that the throttle valve open when it is not activated or if there is a fracture in the bowden cable.

But, in many Weight-Shift-Control aircrafts like Tanarg 912 (by Aircreation), QuikR (by P&M Aviation Ltd.), its manufacturers install the sprung close throttle system as default.
I wonder is there any special reason for the WSCs?

Regards.
Tanarg912.JPG (You do not have access to download this file.)
QuikR.JPG (You do not have access to download this file.)

  • Re: Sprung Open/Close Throttle Carb System

    by » 12 years ago

    Hi HS,


    Just a guess.
    It may spring from the thinking that on a weight shift that you may not be able to keep it from climbing and or an over speed (VNE) at full throttle? Weight shifts tend to fly a little slower than some aircraft and can land in shorter distances. maybe that influenced their thinking? Maybe someone else here can help us out.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: HS Park
      
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  • Re: Sprung Open/Close Throttle Carb System

    by » 12 years ago

    Hi Roger,

    As you said, this may be the flight characteristics problem in the weight shifts.
    Abrupt and/or continuous max power may induce flight instability during flight.
    I will send this question to the weight shift manufacturers also.

    Thank you.
      
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  • Re: Sprung Open/Close Throttle Carb System

    by » 12 years ago

    HS,

    I can't speak for weight shift, but powered parachutes climb rapidly with a 912 at full throttle. since they usually fly at lower altitudes, the sprung open throttle is an advantage. It gives you the opportunity to climb for a while, thereby increasing the chances of finding a good landing spot when you do shut down.

    Bill.
      
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  • Re: Sprung Open/Close Throttle Carb System

    by » 12 years ago

    While on this subject, I remember an italian company who was offering an equalizer tubefor the 912 whose I.D. was over an inch. It bolted directly onto the manifold where the carb sockets were mounted and then the carb socket bolted to it. When a carb throttle cable or spring failed, The engine could still be throttled up or down with the one good carb and run well enough to get you home even with a huge carb sync imbalance. It was not new technology. This application has been used on dual carb setups on cars for years. I have never really understood why the 912 equalizer tube is so small.

    Anyone have any input?

    Bill.
      
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