Service difficulty report · Compression Ring · Gulstm G44

Difficulty date
September 26, 2006
Submitted
November 13, 2006
Operation
General aviation
Aircraft
N645DH
Make and model
Gulstm G44
Aircraft serial
1329
Engine
Lyc GO480B1C
Part
Compression Ring
Part number
SI74673
Condition
Improper
Location
Piston
Stage of operation
IN
How discovered
B
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

SUPERIOR COMPRESSION RINGS PN 74673 WERE INSTALLED DURING OVERHAUL, AFTER 3.0 HRS OF RUNNING A BORE SCOPE INSPECTION REVEALED SOME STRANGE BLACKENING OF THE CYLINDER WALLS. A CYLINDER WAS REMOVED TO INVESTIGATE AND THE TOP (2) COMPRESSION RINGS ONLY SHOWED CONTACT ON THE BOTTOM HALF INDICATING THAT THE BEVEL ON THE FACE OF THE RING WAS FACING THE WRONG WAY FOR A COMPRESSION RING. AFTER COMPARING THIS SUPERIOR RING TO A MFG RING IT APPEARS THE SUPERIOR RING IS DEFECTIVE, NUMBERED WRONG, BUT DOES NOT MATCH THE SHAPE OF THE RING AND INFORMATION OBTAINED FROM MFG TECH SUPPORT. SUBSEQUENTLY ALL CYLINDER HAVE BEEN REMOVE TO REPLACE THESE RINGS. RECOMMEND THAT ALL RINGS FROM MFG BE RECALLED FROM THE SYSTEM FOR SAF