Hi Fellow Rotax Owners. I have a question.

I have a Rotax 912ULS fitted with an Airmaster Constant Speed Propeller. About 3 hours flying ago I noticed that the RPM gauge, which is the standard Rotax item (photo enclosed) was reading about 400rpm lower than I expected. I have since “stobed” the prop and it seems that the engine is running at the correct speed but the tacho is reading low. At full power, with the prop controller set to “take-off”, the prop is doing 2350rpm, which, after applying the gearbox ratio of 2.43:1 is 5700rpm which is what the controller is set to. The tacho reads 5250.

Has anyone experienced this before? The tacho is about 20 years old but the engine is only 6 years old. Do the tachos sometimes go wrong or is there likely to be another cause?

Many thanks. Peter

7659_1_Rotax Tacho.JPG (You do not have access to download this file.)
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