What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
The aircraft was engaged in aerial application operations. The pilot stated that he had just sprayed a small field to the west of Norfolk Nebraska and was climbing away from the field en route to another spray location when the engine quit. He landed the aircraft in an adjacent field of soy beans. The landing did not result in any injury and only minor damage to the aircraft. The aircraft was removed from the field and relocated to the Norfolk airport where the engine was removed and sent to central cylinder service in omaha Nebraska for teardown
Inspection and repair.
The left idler gear in the accessory case was found to have become loose disengaging its connection between the crankshaft and the camshaft. This caused the engine to stop. The idler gear was found to have migrated aft and ground into the accessory case housing to a depth that allowed the gear to come off of the idler shaft. The idler shaft is fixed between a mouning pad on the engine case by means of a flange at the forward end of the idler shaft and held in place with 2 bolts that have a lock retainer to prevent loosening of the bolts and the aft end of the idler shaft is supported by a machined counterbore in the accessory case housing. The idler gear rotates freely on the idler shaft and provides the connection between the aft crankshaft gear and the camshaft gear driving the camshaft and maintaining camshaft to crankshaft timing.
The idler gear has a dual purpose and simultaniously drives the left magneto from a second set of teeth machined into the gear. It was also found that the magneto bearing which is pressed onto end of the impulse coupling and rides in a crankcase counterbore and is a selfcontained bearing with an inner and outer race supported by ball bearings, had lost 5 ball bearings at some point.
Examination of aircraft records presented for the time since major overhaul represent a solid maintenance history of the aircraft and engine.
As the FAA filed it
THE AIRCRAFT WAS ENGAGED IN AERIAL APPLICATION OPERATIONS. THE PILOT STATED THAT HE HAD JUST SPRAYED A SMALL FIELD TO THE WEST OF NORFOLK NEBRASKA AND WAS CLIMBING AWAY FROM THE FIELD EN ROUTE TO ANOTHER SPRAY LOCATION WHEN THE ENGINE QUIT. HE LANDED THE AIRCRAFT IN AN ADJACENT FIELD OF SOY BEANS. THE LANDING DID NOT RESULT IN ANY INJURY AND ONLY MINOR DAMAGE TO THE AIRCRAFT. THE AIRCRAFT WAS REMOVED FROM THE FIELD AND RELOCATED TO THE NORFOLK AIRPORT WHERE THE ENGINE WAS REMOVED AND SENT TO CENTRAL CYLINDER SERVICE IN OMAHA NEBRASKA FOR TEARDOWN
INSPECTION AND REPAIR.
THE LEFT IDLER GEAR IN THE ACCESSORY CASE WAS FOUND TO HAVE BECOME LOOSE DISENGAGING ITS CONNECTION BETWEEN THE CRANKSHAFT AND THE CAMSHAFT. THIS CAUSED THE ENGINE TO STOP. THE IDLER GEAR WAS FOUND TO HAVE MIGRATED AFT AND GROUND INTO THE ACCESSORY CASE HOUSING TO A DEPTH THAT ALLOWED THE GEAR TO COME OFF OF THE IDLER SHAFT. THE IDLER SHAFT IS FIXED BETWEEN A MOUNING PAD ON THE ENGINE CASE BY MEANS OF A FLANGE AT THE FORWARD END OF THE IDLER SHAFT AND HELD IN PLACE WITH 2 BOLTS THAT HAVE A LOCK RETAINER TO PREVENT LOOSENING OF THE BOLTS AND THE AFT END OF THE IDLER SHAFT IS SUPPORTED BY A MACHINED COUNTERBORE IN THE ACCESSORY CASE HOUSING. THE IDLER GEAR ROTATES FREELY ON THE IDLER SHAFT AND PROVIDES THE CONNECTION BETWEEN THE AFT CRANKSHAFT GEAR AND THE CAMSHAFT GEAR DRIVING THE CAMSHAFT AND MAINTAINING CAMSHAFT TO CRANKSHAFT TIMING.
THE IDLER GEAR HAS A DUAL PURPOSE AND SIMULTANIOUSLY DRIVES THE LEFT MAGNETO FROM A SECOND SET OF TEETH MACHINED INTO THE GEAR. IT WAS ALSO FOUND THAT THE MAGNETO BEARING WHICH IS PRESSED ONTO END OF THE IMPULSE COUPLING AND RIDES IN A CRANKCASE COUNTERBORE AND IS A SELFCONTAINED BEARING WITH AN INNER AND OUTER RACE SUPPORTED BY BALL BEARINGS, HAD LOST 5 BALL BEARINGS AT SOME POINT.
EXAMINATION OF AIRCRAFT RECORDS PRESENTED FOR THE TIME SINCE MAJOR OVERHAUL REPRESENT A SOLID MAINTENANCE HISTORY OF THE AIRCRAFT AND ENGINE.