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Rotax 912 gearbox exposed

Roger Lee

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Hi All,


Here are some pictures from a Rotax 912 gearbox. This is being torn down and examined from a prop strike on an RV-12.

You will see a gearbox clutch in one of the pictures and they are installed in the 912ULS 100 hp, but not the 912UL 80 hp. Everything has to come out including the oil seal and bearing. A dye penetrant test now needs to be done down by the bearing opening. The shaft was checked for run out tolerances on the flange and crankcase shaft. These happen to be okay on this plane, this time. that isn't always the case. If you are going to have a prop strike do it at idle or engine off. High speed strikes don't do the prop shaft any favors.


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  • 2 years later...

Hi Chris,


He can if he knew how to do it. Just follow the Heavy Maint manual. Make sure they check the prop flange run out on the face and edge before they pull the gearbox off.


But for the gearbox inspection I personally would not let anyone touch it without having gone and done the procedure in a Rotax class. (because it needs to be torn down)You can mess this up and it will be expensive.

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It is supposed to be inspected. It needs to have the areas checked for cracks and you need the chemical dyes to do it. You will need the bearings replaced too. How fast was the engine turning (rpm), how much of the blade hit (tips or the whole thing gone), what did you hit? What prop was this?

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Prop was at idle.

Contact we with one of those highway traffic cones. The rubber ones.

The damage is shown on the attached picture.

None of the blade is missing.

It looks like it sort of punched the cone top.

No damage to the cone, but you can see what thappened to the blade.



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Hi Dick,


The clutch in the gearbox mainly protects the crankshaft and the gearbox second , but the crankshaft is more than one piece and can twist. There is a check for this twist too and you need a special tool. It is done with the gearbox off.


The light construction of composite props help with this protection because they come apart so easy and the Warp causes more damage do to the solid carbon fiber construction. That said if you land on a gavel or dirt strip with a composite and get a good size ding you may not be going anywhere, but if the warp sustains the same ding you are most likely still flying home.



Give and take.

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