Service difficulty report · Alternator · Lear 35A

Difficulty date
July 20, 2010
Submitted
January 4, 2011
Operation
Air carrier
Make and model
Lear 35A
Aircraft time
25,163 hours
Engine
Garrtt TFE7312
Part
Alternator
Part number
A3579000
Condition
Failed
Location
Ac System
Part time
924 hours
Component
Generator · A3579000
Stage of operation
CR
How discovered
O
Nature of condition
H
Precautionary procedure
O

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

PILOTS REPORTED THAT THEY HAD A DOUBLE GENERATOR FAILURE ENROUTE. THEY WERE ABLE TO RESET THE LT GENERATOR BUT COULD NOT RESET THE RT GENERATOR. UPON ARRIVAL, MX FOUND THAT THE CURRENT LIMITER ON THE RT GENERATOR WAS `OPEN`. THE GENERATOR WAS REMOVED IN ORDER TO CHECK THE SPLINE ADAPTOR AND THE MECHANIC NOTED THAT THE GENERATOR PULLED AWAY FROM THE GEARBOX EASILY. THE GENERATOR WAS INSPECTED AND IT WAS FOUND THAT THE DRIVE SHAFT WAS NO LONGER ATTACHED AND HAD SHEARED AT ITS ATTACHMENT POINT. THE SHAFT WAS REMOVED AND THERE WERE ABRASIONS NOTED ALONG THE SHAFT AND THE END THAT ATTATCHES TO THE GENERATOR LOOKS LIKE EITHER A POOR WELD FAILED OR THAT THERE WAS EXCESSIVE HEAT CAUSED BY THE SPINNING SHAFT ONCE IT HAD BECOME DISCONNECTED FROM THE GENERATOR. THE GENERATOR WAS SPUN BY HAND TO CHECK FOR BRG FAILURE AND ROTATION SEEMED SMOOTH WITH LITTLE TO NO NOISE NOTED. THE COOLING FINS ON THE FWD PORTION OF THE GENERATOR WAS INSPECTED FOR DAMAGE, NONE WAS FOUND.

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