Carburator Synchronization

by agustin arango in 912 / 914 Technical Questions 13 years ago

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Re: Carburator Synchronization

by Andy Buchan » 13 years ago

Andy Buchan

1 10 0

Roger,
Agree with what you say about using the throttle stop screws to set idle - but your idle RPM seems high? I thought that 1400rpm was the figure to aim for on both the 912 and 912S engines?
Having the idle RPM at 1800 can make landings a little long!

AndyB

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Re: Carburator Synchronization

by Roger Lee » 13 years ago

Roger Lee

126 5.13k 4.58k

You have to remember that the manual covers different 912's (i.e. the 80 hp and the 100hp versions). The 80 hp 912UL has a lower compression and no slipper clutch and can idle at the lower rpms without beating the crud out of the gearbox and all the other components that don't like vibration including your engine mounts. The 912ULS 100 hp at 10.5:1 compression is to high to idle well at low rpms (i.e. 1400-1600). This beats up the gearbox components as the engine "chugs" along and vibrates something awful. In school they recommend that the 912ULS with the higher compression be set somewhere close to 1800 rpm and during warm up at 2000 or more. I set the 912ULS at 1750-1800 and the 912UL at 1600-1700 depending on the planes they are on. Not one 912ULS client has ever complained or had any landing issues at 1750-1800 rpm for landing. Your speed is controlled by the stick and not the throttle on landing. I have a Flight Design CTSW with a glide ratio of 14:1. A slippery little plane. I land at 2700-2900 depending if I'm loaded heavy all the time and at the same speed regardless of the throttle setting. You just pull the stick back a little more 50-60 knts is the same no matter how you do it. You can pull the stick back at any landing throttle setting and drop out of the sky from being too slow. Yes I do land at idle sometimes too. With the light LSA aircraft, carrying a little throttle to touch makes landings simple and better more often plus you get a nice solid feel in the controls with a little prop wash. Nothing wrong with idle landings it just makes things easier with a little throttle in light planes especially with heavy cross winds. With a really low idle rpm for the 912ULS you also stand a little better chance of loosing an engine at idle during approach. I'm all in for the better safe than sorry approach.

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

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Carburator Synchronization

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