Alert Extracted From:
AC No. 43-16A
Alert No. 316
November 2004

APPLIANCES
Slick; Model 6310; Impulse Coupling Failure; ATA 7414

During an engine run for a 50-hour aircraft inspection, the right hand magneto was inoperative.

A technician found the magneto lying on top of the engine with a broken mounting flange. He also found the impulse coupling had come apart during the engine run, seizing the magneto, and then breaking the flange.

The submitter indicates the magneto had 125 hours since the last 500-hour inspection. At that time, the impulse couplings were within specifications as indicated in the Slick maintenance and overhaul manual. A search of the FAA Service Difficulty Reporting System database revealed 9 other reports of magneto failure.

They are as follows:
(Installed on Continental)
Impulse coupling broke, breaking the mounting flange    
IO-520-F     July 1995

Left and right impulse couplings failed             O-470-R     November 2001

Impulse coupling failed, magneto case broke at
mount pad, metal contamination to engine        
O-470-U     May 2002

Impulse coupling failed, magneto separated from
the engine, metal contamination to engine        
IO-520         July 2002

Impulse coupling disintegrated, metal contamination
to engine                        
IO-550-C     November 2002

Impulse coupling failed, magneto separated from
engine                            
IO-520-L     July 2003

Impulse coupling broken                
IO-550-C     September 2004

Impulse coupling failed, breaking the magneto housing    
O-470-S     September 2004