NTSB Identification: NYC93LA129.
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Accident occurred Sunday, June 27, 1993 in WEST MILFORD, NJ
Probable Cause Approval Date: 09/13/1994
Aircraft: PIPER PA-28-236, registration: N8220J
Injuries: 2 Serious.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

AFTER TAKEOFF, THE ENGINE EXPERIENCED A PARTIAL POWER LOSS. THE PILOT SET UP FOR A FORCED LANDING ON A LAKE. PRIOR TO LANDING, THE AIRPLANE STRUCK A TREE, AND THEN CAME TO REST IN THE LAKE. POST ACCIDENT INVESTIGATION FOUND THE TWO MAGNETOS WERE DRIVEN BY A SINGLE DRIVE WHICH HAD A BROKEN IMPULSE COUPLING SPRING. THE BROKEN SPRING ALLOWED THE ENGINE TIMING TO RETARD APROXIMATELY 20 DEGREES. WHEN THE ENGINE WAS RUN, IT WOULD NOT EXCEED 1900 RPM AND WAS IT RAN ROUGH. WHEN THE IMPULSE COUPLING WAS REPLACED, THE ENGINE PRODUCED 2800 RPM. METALLURGICAL EXAMINATION OF THE FAILED SPRING FOUND THE FRACTURE ORIGINATED WITH FATIGUE AND THEN FAILED IN OVERLOAD. ACCORDING TO THE NTSB METALLURGICAL REPORT, THE CRACKS FOUND AT THE ORIGIN OF THE FAILURE WERE CREATED WHEN THE SPRING WAS MANUFACTURED.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A manufacturer's defect which resulted in fatigue failure of the magneto impluse coupling spring and the loss of engine power. A factor was unsuitable terrain.

Full narrative available

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