912ULS idle

[Dick B in KY]

For you 912 ULS operators - what do get for your low idle RPM without engine stoppage on landing?? I'm having trouble getting mine to idle at 1800 without wanting to rattle the gearbox or stop. Yes the carbs are synced mechanically and pneumatically. Any thoughts?

Dick B

[Av8r3400]

Just an off the cuff question, but what tach are you using?

Your engine should idle fine at 1800 with no gearbox rattle.

Second off the cuff questions: how many hours on the engine? Has the gearbox ever been serviced?

[DesertFox4]

Dick,
I usually shoot for 1300 to 1400 rpms idle. Lower than Rotax recommends but this is to reduce float on landing. With air loads on the prop during final approach there are no gear noises.
Staying out of these lower rpms while on the ground and running 1800 and above keeps me out of gear noises.

[Dorsal]

I tend to run ~1600 and boost it back up over 1800 once down.

[Agfoxflyer]

I idle at 1800 & on shut down I can pull it back to 1400, then shut down.

[Dick B in KY]

Thanks for the replys everyone. Av8r3400 to your questions - tach is standard Rotax, hours are over 100+ and the gear box has never been serviced. 3 blade Whirlwind and all blade angles are equal. No noise until below 1800. No one has a tendency to stop at low RPM? Everything else is fine with the engine.

Dick B

[Dave S]

Dick,

My experience has been similar to others who set the idle stop below 1800 so the throttle can be closed further for shutdown and to add some additional drag on final. I have mine set to 1600; and, it runs very smoothly at that setting with no tendency to quit due to the reduced rpm. Also makes for an easy startup.

Do you have the gearbox with the slipper clutch? I do have the slipper clutch and no tendency to chatter down to 1600.

[Flybyjim]

I also set mine around 1400 but it never gets below 1600 on my final until the last part of the flair. I really helps on the days with heat on the runway. I do not let the rpm stay below 1800 once landed and I have not heard gear sounds doing it this way.

[chrisag]

Just a thought... has the accuracy of the tacho been checked. I have seen these up to 200 rpm out when checked with my prop balancer tacho. Makes a big difference once re calibrated.

[Av8r3400]

Just a thought... has the accuracy of the tacho been checked...

This is good advise. Analog (needle) tachometers are notoriously inaccurate over time on these engines. The Rotax tach I had in the yellow plane was reading 250 rpm low when I replaced it with a digital unit.

I would try to borrow a TinyTach from somewhere so that you can at least cross check your needle tach.