Service difficulty report · Impulse Coupling · Bnorm BN2A26

Difficulty date
July 23, 2010
Submitted
January 4, 2011
Operation
General aviation
Make and model
Bnorm BN2A26
Aircraft time
20,550 hours
Engine
Lyc O540E4C5
Propeller
Hartzl HCC2YK2
Part
Impulse Coupling
Part number
M3333
Condition
Broken
Location
Magneto
Part time
1,414 hours
Component
Magneto · Slick · 6351
Stage of operation
IN
How discovered
V
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

MAG WAS RECEIVED DUE TO SEIZED CONDITION. UNKNOWN WHEN IT OCCURRED DURING ENG OPERATION. 1 IMPULSE FLYWEIGHT WAS FOUND BROKEN AWAY FROM IMPULSE ASSY AND WEDGED BETWEEN THE OTHER FLYWEIGHT AND THE MAG HOUSING. THE IMPULSE COUPLING WAS REMOVED AND THE RIVET THAT HOLDS THE FLYWEIGHT TO THE ASSY WAS FOUND WORN AND BROKEN, ONE HALF STILL IN THE IMPULSE ASSY AND THE OTHER HALF IN THE FLYWEIGHT. THE RIVET APPEARS TO HAVE BEEN LOOSE FOR SOME TIME DUE TO WEAR AROUND THE DIAMETER OF THE RIVET AND WEAR IN THE IMPULSE PLATE WHERE THE RIVET IS CONTAINED. THE ALUMINUM HOUSING WAS SCORED AND THE MAG ROTOR WAS FOUND TO BE DIFFICULT TO TURN. THE MAG WAS EXCHANGED FOR A NEW UNIT AND THE CUSTOMER WARNED OF POSSIBLE METAL CONTAMINATION TO THE ENGINE.