ROTORWAY EXEC 162-F N8006A accident near Titusville, Florida

Probable cause

A failure of the No. 4 exhaust valve spring retainer, which resulted in a partial loss of engine power.

NTSB analysis

The flight instructor, who was also the owner of the experimental amateur-built helicopter, said that shortly after takeoff, while about 150 ft above ground level, the helicopter’s engine lost partial power with “severe backfiring.” He declared an emergency, turned back to the airport, and landed on a grassy area. Upon touchdown, the helicopter’s front left skid dug into the grass and the helicopter rolled over. Postaccident examination of the engine revealed the No. 4 exhaust valve spring retainer was missing. The engine maintenance manual required inspection of the valve train system, including the spring retainer, every 25 hours. A review of the engine maintenance logbook revealed that the flight instructor/owner had performed the 25-hour inspection about 8.8 hours before the accident. The reason for the separation of the valve spring retainer was not determined.

Text from the NTSB. Open the NTSB docket for ERA23LA073 for the full record.