Service difficulty report · Breaker Points · Cessna 172N

Difficulty date
February 5, 2010
Submitted
March 1, 2010
Operation
General aviation
Make and model
Cessna 172N
Aircraft time
12,231 hours
Engine
Lyc O320H2AD
Propeller
Mcauly 1C160CTM
Part
Breaker Points
Part number
AB10382585
Condition
Worn
Location
Magneto
Part time
200 hours
Component
Magneto · Bendix
Component part number
D4RN3000
Stage of operation
IN
How discovered
9
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

(CAN) WHILE PERFORMING ROUTINGE INSP THE MAGNETO TO ENGINE TIMING WAS NOTED TO BE 5 DEGREES OFF. THE MAGNETO WAS REMOVED TO INSPECT AND ADJUST THE POINTS AND IT WAS FOUND THAT THE POINTS WERE JUST BARELY OPENING (WHICH MEANT THAT THE MAGNETO WAS CLOSE TO FAILING). THESE POINTS HAD ONLY 200 HOURS TIME IN SERVICE. THIS HAS BEEN AN ONGOING PROBLEM IN THE LAST NUMBER OF YEARS IN THAT THE PLASTIC/NYLON CAM WARS PREMATURELY CAUSING THE MAGNETO, SO IN THEORY IF ONE FAILED THE OTHER HALF OF THE MAGNETO SHOULD CONTINUE TO OPERATE BUT IN PRACTICE BOTH SETS OF POINTS TEND TO WEAR EQUALLY SO THAT IF ONE SET OF POINTS FAIL, THE OTHER IS CLOSE TO FAILURE AS WELL, WHICH WOULD THE CAUSE THE ENGINE TO QUIT. (THIS HAS HAPPENED TO 1 OF OUR ACFT IN THE PAST. (TC 20100208007)

More about the Cessna 172N