B

BigJohn

Well Known Member
I decided to do the mechanical syncronization now, even though I am a ways off from first engine run. Trying to be a good little doobie I went to the Rotax site and downloaded the most recent version of the Line Maintenance Manual, Edition 2/Rev. 0 dated October 01/2009.

The procedure for mechanical syncronization is in Section 12-20-00, Page 32. Aside from the sometimes poor translation, I was able to discern the procedure. However one point seemed counter intuitive. Step 5 says "Pull out the feeler gauge and then turn each idle speed adjustment screw (2) 1.5 turns counter clockwise."

Since this seemed wrong, I took a look at the version of the manual that came on the CD with the engine, labeled Edition 1/Rev. 0 dated Sept. 01/07. In section 4.1.2 on Page 21 the procedure instructs, "Pull out the feeler gauge and then turn each idle speed adjustment screw (2) 1.5 turns in a clockwise direction." This seems more logical to me.

This discrepancy raises several questions:

Which manual is correct?
Should we be using the most recent version of the manual or not?
Is there a mechanism to report discrepancies in the manuals back to Rotax?
Should Van's be more specific when they refer us to Rotax manuals?

Any advice appreciated.
 
More info......

I looked at the carbs. Both idle speed stops seem to have been set at the factory for the test run, and sealed with some type of torque-seal. Is it really necessary to change these settings, just because the procedure calls for it?
 
Re: Idle stops

I don't know if it's necessary or not but I went through the whole recommended procedure. The factory torque seal was pretty wide, and I wound up within its boundaries. I may have to re-set the idle because I can't get less than about 2100 on final and that seems to carry me a long way down the runway even with 55 knots approach.

Wayne 120241/143WM
 
Idle

Its the idle on the ground that counts not in the air. There was many threads about what the proper idle should be set at on the ground. Set it a about 1500rpm min but after start maintain a min of 1800. But when you shut down then pull throttle to 1500rpm and shut down one Mag switch wait one second then the next Mag (this will give you the lowest rpm for shut down)this will reduce wear and tear on the slipper clutch in the reduction gear. You will most likely not see lower than 2100rpm in the air cause RPM is a function of speed then. Because of the high compression ratio of the Rotax the engine stops very fast when you shut it down. If you shut down at a high RPM then the propeller will try to continue to spin after the engine stops causing unnecessary wear on the slipper clutch. You will just have to change your flying technique to slow the plane down in the air on approach. The recommended approach speed of 50-55kts is just right any faster and float baby float, remember you want that nose up high on landing same as takeoff to reduce wear on the nose wheel strut to. Welcome to Rotax 101.

John
RV12 N1212K
 
Having flown three different 912 equipped planes

All of them have an idle over 2000 in the air, I have added issues that I fly out of Scottsdale so with all the jet traffic I keep final at 65 - 70 cut the power over the numbers slowly and settle in, fortunately its a long runway
 
Rotax Manual Discrepancy

Thanks for all the interesting comments on setting idle speeds, but could someone address the issue of the discrepancy in the manuals? It seems obvious that the correct wording is "clockwise", but how does one confirm that and point out the error in the manual to the Rotax people?
 
You must log in or register to reply here.