Service difficulty report · Bearing · Robsin R44RAVENII

Difficulty date
March 19, 2011
Submitted
September 14, 2015
Operation
General aviation
Make and model
Robsin R44RAVENII
Aircraft time
2,245 hours
Engine
Lyc IO540AE1A5
Part
Bearing
Part number
10357426
Condition
Loose
Location
Magneto
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) MAGNETO WAS REMOVED APPROXIMATELY 320 HOURS AFTER 500 HR INSPECTION BECAUSE OF MISSING TEETH ON THE NYLON DISTRIBUTOR GEAR. WHEN RECEIVED, THE MAG WAS DISASSEMBLED AND THE BUSHING INSIDE THE DISTRIBUTOR BLOCK WAS NO LONGER ATTACHED TO THE DISTRIBUTOR BLOCK. THIS ALLOWED THE DISTRIBUTOR GEAR TO TILT AND WEAR WHICH CAUSED 6 TEETH TO BREAK OFF THE GEAR. THE MAG INTERNAL TIMING WOULD HAVE BEEN AFFECTED. THE INSIDE DIAMETER OF THE BUSHING WAS AT THE HIGH END OF THE ALLOWED LIMITS BUT THIS DOES NOT APPEAR TO BE A FACTOR IN THE FAILURE OF THE BUSHING TO BLOCK ATTACHMENT. IT IS UNKNOWN THE TOTAL NR OF HOURS ON THE PART BUT THE BATCH CODE ON THE DISTRTIBUTOR BLOCK IS 0908. A 500 HOUR INSPECTION WAS PERFORMED, THE BLOCK AND GEAR WERE REPLACED, AND THE MAGNETO WAS RETURNED TO SERVICE.