Service difficulty report · Pinion Gear · Bell 407

Difficulty date
April 25, 2002
Submitted
June 21, 2002
Operation
Air carrier
Aircraft
N467AL
Make and model
Bell 407
Aircraft serial
53190
Engine
Allsn 250C47B
Part
Pinion Gear
Part number
6893672
Part serial
NN78493
Condition
Galled
Location
Gearbox
Part time
619 hours
Stage of operation
IN
How discovered
V
Nature of condition
O
Precautionary procedure
K

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

What was found

GEARBOX WAS REMOVED DUE TO FWU BORE DAMAGE. UPON INSPECTION OF CHIP DETECTORS, FOUND METAL ON BOTH PLUGS. AFTER DISASSEMBLY FOUND EXCESSIVE GALLING ON TM AND PINION GEARS CAUSE FOR METAL. METAL CONTAMINATION WAS GENERATED FROM UNFINISHED MACHINING OF TM GEAR TEETH AT RADIUS. THIS CAUSED GALLING TO PINION GEARS. ASSURE PROPER MACHINING AND MESHING OF GEAR TEETH AND RADIUS AT FACTORY.

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