Amateur-built LONGEZ N499CM accident near Dexter, Kentucky

Probable cause

The loss of engine power due to the chaffing and grounding of the single magneto's ignition lead.

NTSB analysis

A witness observed the experimental, amateur built airplane perform a steep bank in an aerobatic-type maneuver. After about 30 seconds, he observed a large explosion as the airplane’s left wing separated during its collision with trees. The airplane continued its descent and impacted the ground inverted between a residential driveway and the row of trees. The airplane was consumed by the subsequent fire.

A postaccident examination revealed that the engine’s single magneto P-lead terminal end had made contact with an adjacent fabric covered steel braid oil cooler hose line. Closer examination of the ignition lead disclosed that chaffing had exposed the metal strand layer of the hose. The grounding of the magneto would have rendered the engine unable to produce power due to the lack of an ignition source. The condition of the propeller blades at the wreckage was consistent with the engine not operating at the time of ground impact.

Text from the NTSB. Open the NTSB docket for ERA10LA102 for the full record.