N409LHPilatus Aircraft PC-12/47E · 2024

On December 8, 2014, at 1115 mountain standard time, an Enstrom Helicopter, N409LH; experienced a total loss of engine power during cruise flight. The student pilot performed an autorotation to a field. The helicopter sustained substantial damage. The student pilot was uninjured. The helicopter was operated by Mountain One Helicopters under 14 Code of Federal Regulations Part 91 as an instructional flight that was operating on a flight plan. The flight last departed from Greeley-Weld County Airport, Greeley, Colorado, and was destined to Platte Valley Airpark, Hudson, Colorado.

During a solo cross country flight flown by a student pilot, the helicopter experienced a total loss of engine power during cruise flight. The pilot performed an autorotation to a field. During landing flare, the helicopter tail struck the ground resulting in the main rotor blades flexing downwards, which severed the tail rotor boom. The helicopter sustained substantial damage to the fuselage and rotor blades. The pilot was uninjured. The engine was test run by the operator without the knowledge and permission of the National Transportation Safety Board Investigator-In-Charge or the Federal Aviation Administration Inspector assigned to the accident investigation. The operator stated the engine was run without any anomalies.

According to the instructor, the student pilot was making a practice autorotation to be followed by a powered recovery in preparation for his taking the private pilot practical test. When power was added, only 2500 rpm (revolutions per minute) instead of 3050 rpm was attained. A forced landing ensued and the helicopter slid approximately 2 feet on a rain-soaked field. The skid toes dug into the soft ground, stopping forward movement and causing the fuselage to shift forward. The main rotor blades contacted and severed the tail rotor driveshaft. In addition, the the tail rotor gearbox, tailboom, and a main rotor blade were damaged.

Post-accident examination of the engine and power train revealed no anomalies that would have prevented the engine from producing full power.