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another Autoflight gearbox failure - this time after 34 hrs

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pantdino

Well-Known Member
Joined
Feb 4, 2019
Messages
136
Location
Cerritos
No, this is not the same Autoflight gearbox that failed at 43 hrs.

My LS3 430-equipped Titan T-51 flew from Ohio to Los Angeles at 180 KIAS without problems, taking about 12 hrs at 3000 rpm at 22 inches MAP.
But after half an hour here the prop governor began to hunt, so the plane was landed.
Inspection of the oil in the governor showed a metallic appearance. It shares oil with the Autoflight PSRU.
Interestingly, the gearbox oil was changed in Las Vegas, only about an hour from LA by air.

I sent the gearbox back to their previous chief engineer , (Bill Koleno, who was also their chief test pilot, and is the one who flew it here), who said the idler bearing was installed 0.015" off axis, which caused the bearing to fail and make metal. The gears and everything else looked fine.
The plan is to install a slightly larger bearing on-axis.

0.015" off axis doesn't sound like much to me. Could it really cause a bearing to fail after 34 hrs? Most T-51s get flown at about 160mph for an hour or so, not 215 mph for 2 hr stretches. I wonder if that was part of the reason for this bearing failure-- it overheated locally. (Bill said the gearbox never felt too hot to the touch.)

And in case you're wondering, no, there is no warranty coverage.

Jim
 
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