Geared Engines - Failure Mode?

[bob turner]

Anybody know what symptoms indicate gearbox problems on the big 300 hp Lycomings? Does it just quit someday, or do you have plenty of warning?

[aktango58]

Are you talking the R-680?

or are you talking the IO-540.

I did not think that the 540 was geared... but if talking the accessory case, it is a matter of if the engine dies from the mag. impulse coupler shearing off the mag drive and stripping out the gears and sending shrapnel into the rest of the engine which then kills the fuel pump gear which means that you no longer have fuel either...so it is a quick death, most are unexpected.

Do you want to know which accidents/deaths were caused by the mag impulse coupling going bad and seizing the mag drive?

[Ruffair]

If you are talking the GO-480, the gear box will get to "growling" as it ages and has been abused.

I've never seen one that just quit, so can't help ya there

[irishfield]

GSO-480's and such.... keep the prop loaded and don't go throwing them into fine pitch on the downwind and they'll last for ever.. long past TBO.

[bob turner]

What do they sound like on shut- down to a mechanic standing outside? The one I was listening to sounded like a lot of rather large dominoes falling against each other.

I understand the idea of never letting the prop drive the engine, but also understand that not everybody operates them that way.

[louiscc]

Mine had a cracked Geared Box. Discovered and stopped flying it when the mechanic found a lot of metal in the oil. Like rip from a lathe. Lot's of it. When we oppenned the engine, we found metal everywhere. When we openned the gear box, we found a lot of metal, and the gears where pretty bad looking. No strange sound. No oil was coming out from the geared box from the micro fracture. I am sure that we could had see them with a magnetic test when we assembled the motor. The fissure where around some bearings in the case.

Louis