Service difficulty report · Bevel Gear · Colhel CH47DCOL

Difficulty date
July 24, 2017
Submitted
July 24, 2017
Operation
General aviation
Aircraft
N471CH
Make and model
Colhel CH47DCOL
Aircraft serial
900198
Aircraft time
7,762 hours
Engine
Hnywl T55GA714A
Engine time
856 hours
Part
Bevel Gear
Condition
Failed
Location
Nr 1 Engine
Part time
856 hours
Stage of operation
FF
How discovered
O
Nature of condition
Y
Precautionary procedure
E

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

What was found

AFTER DROPPING WATER AND TURNING AWAY FROM FIRE, ENGINE STOPPED. ENGINE FAIL LIGHT, ENGINE CHIP LIGHT, REVERSER LIGHT ILLUMINATED. CONTINUED SINGLE ENGINE BACK TO SERVICE LANDING.WHEN THE AIRCRAFT ARRIVED BACK AT THE SERVICE LANDING, NR 1 ENGINE WAS INOPERATIVE. PILOT TRIED TO MOTOR ENGINE. WOULDN'T START. NOTED THE NR 1 ENGINE CHIP LIGHT ILLUMINATED ON MAINTENANCE PANEL. PULLED CHIP DETECTOR AND FOUND SLIVERS AND CHUNKS OF METAL ON DETECTOR. REMOVED AND REPLACED THE NR 1 ENGINE. ONCE ENGINE WAS RECEIVED BACK AT THE REPAIR STATION, THE OUTPUT SHAFT SUPPORT HOUSING WAS REMOVED AND SOURCE OF METAL CONTAMINATION, N1 DISCONNECT WAS FOUND. ACCESSORY DRIVE CARRIER BEVEL GEAR FAILED. FROM APPEARANCE THE CARRIER BEVEL GEAR FAILED AND CONTINUED TO ROTATE UNTIL FINALLY BREAKING COMPLETELY, DISENGAGING FROM THE BEVEL DRIVE GEAR.