On April 30, 2007, a Cessna 177RG (registration N177R) was involved in an aviation accident near Perris, CA. Investigators recorded the probable cause as: a loss of engine power while in cruise flight due to an improperly installed magneto housing by the owner/pilot. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft lost engine power 12 nautical miles into flight, leading to a forced landing short of the runway, where it collided with trees. Examination revealed a separated magneto cap with missing screws.
Accident Sequence
Approximately 12 nautical miles into the flight, the engine abruptly lost power. The pilot decided to attempt a landing at a nearby airport but determined that the aircraft did not have sufficient altitude to reach the runway. The airplane subsequently landed 2.51 nautical miles short of the runway and collided with trees during the forced landing.
Post-Accident Examination
During the engine examination, investigators noted that the cap and harness assembly of the single drive duel magneto was separated from the magneto. Closer examination revealed significant fretting signatures where the cap is seated against the housing of the magneto, which was supposed to have been secured by four screws. No screws were observed or found. There were no impact energy damage signatures on the cap, magneto, ignition harness, or firewall. The pilot stated that he was the last person to have the harness off the magneto.
Findings
The investigation documented that the magneto cap and harness assembly had separated due to the absence of the four securing screws. The lack of impact damage on the cap and associated components indicated that the separation occurred before the collision.