912 gearbox backlash... does idle speed damage the gearbox?

[hallschuch]

Hello fellas,
A year ago I flew 5KA in Idaho (912 rotax) and the instructor told me to keep some power on at all times rather than idle during decent and landing to prevent gear chatter... I can't find anything in the Rotax manuals about it.
Anybody heard of this ?

[neville]

I never go under 2000 RPM, even when taxing. It is less expensive to replace brake pads than rebuild a gear box. On the 912iS there is no play in the dog gear faces but they will still work enough to cause vibration in the gear box. By the time I had 250 hrs on the gearbox it had been repaired 4 times because of the dog gear problem. Which was corrected by a mod to the oil system which added a port to inject oil directly on to the dog gear faces. The loading and unloading between the prop and engine due to things such as turbulence or uneven surface while taxing is the main cause of dog gear wear, which leads to repair of the gearbox.

[Meyer]

Agree with neville's guidance. Min rpm is 2,000. I know S&R teaches this. Many others follow it too.

[alexM]

Just flew at Stick & Rudder a week ago. I can confirm that it was considered very important to maintain the 2000 rpm minimum to protect the gearbox.
In flight it never seemed to get that low but immediately after landing it would immediately drop and require attention.