NTSB Factual Report

On April 24, 2006, about 0820 eastern daylight time, a Mooney M20J, N201BD, was substantially damaged during a forced landing, after a loss of engine power while climbing after takeoff from Norwood Memorial Airport (OWD), Norwood, Massachusetts. The certificated commercial pilot sustained minor injuries. Instrument meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the flight destined for the Solberg-Hunterdon Airport (N51), Readington, New Jersey. The personal flight was conducted under 14 CFR Part 91.

The airplane was departing from runway 35, a 4,008-foot-long, 100-foot-wide, asphalt runway.

The pilot reported that the airplane accelerated and lifted off normally from the runway; however, during the initial climb after takeoff, the airplane experienced a significant loss of engine power. The pilot declared an emergency, and performed a forced landing to a golf course, that was located adjacent to the airport. The airplane came to rest upright; however, the engine was torn away from the firewall, and the airframe was substantially damaged.

The airplane was equipped with a Lycoming IO-360-A3B6D engine. Examination of the engine by a Federal Aviation Administration inspector did not reveal any catastrophic engine failures; however, it was noted that the Bendix single drive, dual magneto was separated from its mount. Additional examination revealed that the mounting clips remained attached to the engine. The magneto mounting flange was fractured on both sides where the mounting clips would normally be located. The magneto assembly was forwarded to the Safety Board's Materials Laboratory, Washington, D.C., for further examination.

Magnified optical examination of the fractures contained on the magneto mounting flange revealed surface features and beach markings indicative of fatigue crack progression. Both fracture surfaces showed surface damage consistent with re-contact between the fracture faces; however, significantly more damage was observed on one side then the other. The clamping nuts and internal toothed lock washers were intact. The nut washer faces contained marks and dents which indicated contact with the locking washers. See the Materials Laboratory Factual Report, located in the public docket for additional information.

The airplane had been operated for about 275 hours since its most recent annual inspection, which was performed on April 1, 2005. The logbook entry for the annual inspection specifically included maintenance performed on the magneto.

On August 15, 2003, Lycoming issued Service Instruction No. 1508A, which included IO-360-A3B6D engines installed on Mooney M20J airplanes. The service instruction stated, in part:

"There have been reports of the hardware attaching the dual magneto to the studs in the engine accessory housing becoming loose after maintenance in the field...It is possible that during magneto maintenance, such as timing changes or checks, the attachment nuts are not being torque to specifications or that hardware has not been installed properly. At the next oil change interval, but not to exceed 50 hours of operation, and any time the magneto is serviced, the correct attachment of the magneto should be verified...."

A weather observation taken at OWD, about the time of the accident, reported: Winds from 360 degrees, at 6 knots; visibility 3 statue miles in mist, ceiling 400 feet overcast; temperature 44 degrees F; dew point 43 degrees F; altimeter 29.85 in/hg.

NTSB Probable Cause

Improper maintenance, which resulted in a fatigue fracture of the dual magneto mounting flange, and a subsequent loss of engine power.