Rattle at low RPM symptom of ?
in 912 / 914 Technical Questions
12 years ago
At a probably reputable site I read this:
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A loose gearbox has a distinctive “rattle†at low RPM, if allowed to continue, the rattle will get worse and the internal parts will wear progressively faster. Fortunately the Rotax gearbox is easily removed from the engine if any repairs are needed.
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We normally idle at 2000. No rattle there at all.
On the rare occassions where it has briefly dropped down to about 1600 RPM (like after a cold weather start and I released the the choke too early without bringing the throttle up a notch) I DO hear what I would call a rattle. Of course I dont let it stay down there as I (a) it just doesnt cound right and (b) I understood that is hard on the clutch, etc.
But my question is is _that_ a symptom of loose gearbox? Or would it only be considered loose-gearbox symptom if I was hearing it up at 2000 RPM or higher?
My other questions are is if it is a symptom of a loose gearbox --
1) does it seem like something that urgently needs to be addressed (is it causing risk or risk of damage to the engine if I never let it run down that low?)
2) Anyone have any idea how much typically a rotax savvy A&P might charge (parts and labor) to rebuild the gearbox? Or if one removed it and sent it in for rebuild what the typical cost range is?
3) Our 912UL has about 500 hours on it. One rather Rotax experienced A&P guy (the instructor at the 16 hour ELSA inspectors course I took last year) mentioned, if I am remembering right, that it is not unusual for 912s to need the gearbox rebuilt at about 600 to 800 hours.
Can anyone comment on that?
Al
-----------------------------------------
A loose gearbox has a distinctive “rattle†at low RPM, if allowed to continue, the rattle will get worse and the internal parts will wear progressively faster. Fortunately the Rotax gearbox is easily removed from the engine if any repairs are needed.
-----------------------------------------
We normally idle at 2000. No rattle there at all.
On the rare occassions where it has briefly dropped down to about 1600 RPM (like after a cold weather start and I released the the choke too early without bringing the throttle up a notch) I DO hear what I would call a rattle. Of course I dont let it stay down there as I (a) it just doesnt cound right and (b) I understood that is hard on the clutch, etc.
But my question is is _that_ a symptom of loose gearbox? Or would it only be considered loose-gearbox symptom if I was hearing it up at 2000 RPM or higher?
My other questions are is if it is a symptom of a loose gearbox --
1) does it seem like something that urgently needs to be addressed (is it causing risk or risk of damage to the engine if I never let it run down that low?)
2) Anyone have any idea how much typically a rotax savvy A&P might charge (parts and labor) to rebuild the gearbox? Or if one removed it and sent it in for rebuild what the typical cost range is?
3) Our 912UL has about 500 hours on it. One rather Rotax experienced A&P guy (the instructor at the 16 hour ELSA inspectors course I took last year) mentioned, if I am remembering right, that it is not unusual for 912s to need the gearbox rebuilt at about 600 to 800 hours.
Can anyone comment on that?
Al
