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Checking the friction torque on the gearbox / prop

Roger Lee

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Hi All,



People always ask "How do I check the friction Torque on my gearbox / prop?" Many don't even know they should do this at each 100 hr. and / or the Annual Condition Inspection. If you have taken a Rotax maint class you have most likely been taught this. It is a very easy process. If you haven't had a Rotax class then make sure your mechanic does this procedure during the inspection. It is one of the items in the Line Maint. check off sheet for inspections. You have to list the value that you obtain from this test. FD allows for the owner to do some maint and the engine inspection if you have taken an approved appropriate level Rotax class.


Rotax Line maint manual:



The crank shaft lock procedure is in the Rotax Line Maint. manual in section 12-20-00 paragraph 7 page 19.

The actual procedure for the friction torque test is section 12-20-00 paragraph 15 page 67.


This is a fairly easy procedure, but it really helps to have someone show you the first time. I always recommend that everyone take a Rotax class because you will then have the correct knowledge to do a procedure, keep yourself from causing any damage and know what and how a mechainic should being doing for your maint. or inspection. Even if you don't do any of your own work then you will know what needs to be done, why and how.


My last note here is for the SLSA group to make sure you don't do any maint. that you aren't legally allowed to do as per the Mfg. and FAA, or haven't been trained to do and to get the Rotax training so you will be legal and have the knowledge to do it properly so as not to cost you big bucks later. With the proper Rotax training SLSA Mfg's give you permission under certain areas in their manuals to do certain procedures if you have had the proper training.


ELSA can do procedures without classes legally, but I would highly recommend against it. I get many calls where someone has gotten into some kind of trouble doing a procedure without the proper knowledge. Protect your investment and go to a Rotax class. The ELSA group can do their own Annual Condition Inspection with an approved 16 hour class and then send the paperwork to the FAA and they will send you a card back saying you are allowed to do the annual on that plane and no other. You can only do the inspection on the plane or planes that you personally own and nobody elses. If you are an ELSA or experimental and are not sure about a procedure the best medicine is a Rotax class, but if that isn't going to happen then get with a Rotax mechanic that can at least assist you and answer your questions before you start .


Here is a good video on the How to do it from R.O.A.N.





Being educated in your maint is the first step in flying safe. Without a sound engine, well maybe it is a good day to go to the movies and not fly.

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Roger is right about E-LSA owners needing to become familiar with the Rotax before they start working on it. Rotax classes would be good but as a minimum get the manuals and become familiar with them. I bring this up because, as some of you know, I decided to build a Vans RV-12 which is an E-LSA. So, I watch the Vans forum which has a section devoted to the 12. Many of the guys bring up questions about carb balance, purging, spark plug gap, etc. It is obvious they are not using the manuals. For example, one question had to do with plug gap and the old values were being brought up. The new values are in the latest rotax manual. This person was not using these manuals but at least asked the question.


The manuals are free to download from the rotax site.


In addition, the rotax site has all the latest bulletins, etc that affect your engine. You can even register your engine by serial number to get email alerts.

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