Amateur-built DB-1 N828X accident near Mayland, Tennessee

Probable cause

The pilot’s failure to maintain helicopter control following a high-side governor failure for reasons that could not be determined during postaccident examination.

NTSB analysis

The pilot was hover-taxiing an experimental amateur-built helicopter about 3 feet above ground level when the engine suddenly accelerated, and the helicopter started to gyrate violently. An engine power increase such as this is indicative of a high-side governor failure, which requires immediate reaction to maintain control of the helicopter. The pilot attempted to maintain control of the helicopter, but it began to drift to the left where his truck and trailer where parked. To avoid a collision with the truck, the pilot raised the collective to climb over the truck. Once clear of the truck, the pilot lowered the collective and landed on a downward slope. The helicopter impacted the ground with the right skid and rolled over on its left side, which resulted in the main rotor blades striking the ground.

The pilot, who was also the owner/operator, had installed an aftermarket governor and had logged a total of 0.5 hour in the helicopter before the accident. The governor was examined and appeared to have been installed correctly. It could not be determined why the governor failed. The pilot had attended transition training for this helicopter, but it did not cover governor failures.

Text from the NTSB. Open the NTSB docket for ERA13LA087 for the full record.