Service difficulty report · Washer · Aerosp AS355*

Difficulty date
February 10, 2006
Submitted
June 6, 2006
Operation
General aviation
Make and model
Aerosp AS355*
Engine
Allsn 250C20R1
Part
Washer
Part number
6820588
Condition
Missing
Location
Gearbox
Component
Gearbox · Allsn
Component part number
23053350
Stage of operation
NR
How discovered
9
Nature of condition
O
Precautionary procedure
O

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

What was found

(CAN) AS ENG NR 2 WAS INCREASED, EXCEEDANCE ON INSTR PANEL, M/R READING HIGH ON TRIPLE TACH, NO INDICATION OF N2 SPEED ON TACH INDICATOR. FOUND N2 GOV GEAR FREEWHEELING, DISENGAGED FROM INTERNAL GB N2 DRV SYS. TEARDOWN OF GB REVEALED BRG RETAINING WASHER WAS MISSING, N2 PWR TRAIN IDLER GEAR ASSY. WASHER RETAINS BRG ON IDLER GEAR SUPT SHAFT. KEY WASHER RETAINED BRG ON IDLER SUPT SHAFT, UNTIL BRG INNER RACE WORE EDGE OF KEY WASHER ALLOWING BRG TO SLIDE AXIALLY, DISENGAGE N2 TACH DRV GEARTRAIN. WITH N2 TACH DRV GEARTRAIN DISENGAGED FROM N2 DRV, ENG COULD OVERSPEED. WEAR ON ID OF N2 PWR TRAIN IDLER BRG, PORTION OF KEY WASHER, IDLER GEAR. PREVIOUS CHIP LIGHTS REPORTED ARE RESULT OF WEAR. (TC NR 20060214006)