Amateur-built 260L N777TC accident near Livingston, Tennessee

Probable cause

A total loss of engine power for reasons that could not be determined. Contributing to the accident was the pilot’s operation of the helicopter in a flight regime that would not allow for a successful autorotative landing.

NTSB analysis

The pilot initiated takeoff in the helicopter, and when passing through effective translational lift, with an airspeed between 40 and 50 knots, and about 100 to 150 ft above ground level (agl), the engine experienced a sudden complete loss of power. He lowered the collective, made a partial throttle reduction, and entered an autorotation, but engine power increased when the helicopter was at 70 to 75 ft agl and 50 knots. He increased the throttle, and the engine power increased to full rpm. As he increased collective, the engine “sputtered and quit instantly.”

The helicopter was operating in the shaded area of the helicopter’s height/velocity diagram, which, according to guidance, may not allow sufficient time or altitude to enter a stabilized autorotative descent. Although the pilot rapidly lowered the collective to gain energy in the main rotor blades, there was not enough inertia in them for a normal autorotative landing. The helicopter landed hard on soft wet terrain resulting in structural damage to one of the steel tubes that attached the tailboom.

During postaccident examination of the helicopter and its engine, one fuel injector nozzle flowed slightly less than the other five; however, it likely did not contribute to the twice-repeated total loss of engine power. The examination of the engine and its systems revealed no other evidence of preimpact failure or malfunction. The reason for the twice-repeated total loss of engine power could not be determined based on the available evidence.

Text from the NTSB. Open the NTSB docket for ERA21LA335 for the full record.