Sport Pilot Talk

SkySteve · Posted: Wed Mar 12, 2008 5:03 pm Post subject: Rotax 912 80HP Idle RPM

I have a Rotax 912A. At what RPM do you set your 80 HP Rotax 912 when the throttle is pulled all the way back (and the engine will still run)? I understand Rotax suggests 2,000 to 2,500 RPM at idle, but I'm referring to when the throttle is all the way back and you are about to land, without killing the engine, or when you want to taxi slowly?

eurofoxjames · Joined: 08 Apr 2006 Posts: 56 Location: Atlanta, Ga

I’m not a mechanic but…
I would think if you set your RPM to 1800-2000 static on the ground, you should see 2000-2200 respectively when about to land…seems you should see an extra 200-300 rpm over static when landing.

SkySteve · Posted: Fri Mar 14, 2008 10:46 pm Post subject:

Eurofoxjames,
What engine do you have in your Euro Fox?

eurofoxjames · Joined: 08 Apr 2006 Posts: 56 Location: Atlanta, Ga

Hi Steve
I have the “912 uls” . I would think both engines are similar in RPM just different compressions/size. Mine is set at 1800rpm min on the ground (though I warm mine up at around 2000-2200 rpm.

I would not set yours up below 1800 or not much lower (bad on the gear box). Other know more then I and maybe they will chime in.

SkySteve · Posted: Sat Mar 15, 2008 8:49 am Post subject:

James,
Mine is currently set at 1800 rpm, also. My problem is that it taxis really fast and I have to ride the brakes all the time if I want to go slow. Also, I am thinking it would be nice to have it at a slower rpm for touch down in short field applications. But I also understand the propeller gear box rattle issue.

CharlieTango · Posted: Sat Mar 15, 2008 9:40 am Post subject:

steve,

i too have the 912uls and wouldn't the idle to be the same due to the compression ratio difference.

however the min idle rpm has mostly to do with a smooth setting for the gearbox and on that issue i would think the highest number you can use would be best.

as far as taxiing too fast at 1800, there is another component to consider and that is your prop pitch.

many of us find that a finer pitch improves all around performance, what is your max rpm at wide open throttle? and what is the max cruise rpm for your 80 hp 912?

SkySteve · Posted: Sat Mar 15, 2008 1:07 pm Post subject:

Charlie,
My max static RPM right now is 5,000 rpm. I am in the testing stages of a rebuild from a tail dragger to a trigear during the winter (still have 2 1/2 ft of snow on each side of the runway) so I have just been taxiing to date (with a few "wheelies" and short lift offs). Weather permitting I should be doing the test flights this next week and I will then find out the max rpm and cruise speed. Just trying to anticipate possible problems and solve them ahead of time right now. With the new Warp Drive propeller the nosewheel is ready to come off the ground within about 75 to 80 feet, and we are located at 5,200' MSL.