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Starting the Rotax 912 UL(S) Engine(s)

Ed Babovec

One of the more difficult things to do regarding the Rotax engines is starting at different temperatures.  The key is to avoid flooding the carburetors with too much fuel.  To start a cold engine, Rotax engines have an enrichment valve, (commonly called a choke, although this is a misnomer), so as to add fuel for ease of starting.  Too much enrichment on a warm engine can cause problems with starting.  Always start a cold engine with full enrichment and no throttle.  Start a warm engine with no enrichment and just a crack of throttle, maybe 1/8 - 1/4" on Pipistrel throttles.  

While soaring with engine off, you must estimate how "cold" your engine is at the point of restart.  You can check your CHT's and oil temperature to get an idea.  Always add enrichment carefully, you can always add more as needed, but too much enrichment to start with can make for a difficult, or failed start.  Of course, you are in a "glider", so glider rules prevail always.  In case of a failed restart, you should be within gliding range of a suitable landing spot.  Always soar with the idea that the engine "will not restart".  


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