Enstrom 280F N280F accident near Jordan Valley, Oregon

Probable cause

A partial loss of engine power due to a worn engine air induction hose, and a subsequent uncontrolled descent into terrain. Contributing to the accident was the failure of maintenance personnel to adequately inspect the hose, and the pilot’s decision to fly the helicopter at a speed and altitude that provided limited time to enter and establish an autorotation following the loss of power.

NTSB analysis

The pilot was performing low-level flight over high desert terrain. The passenger reported that, during the flight, the pilot became concerned over a low “rpm” indication. The pilot began to manipulate the flight controls, and the helicopter rapidly descended, yawed to the right, and impacted terrain.

Examination revealed that significant sections of the outer liner of the engine’s air induction hose were abraded, consistent with long-term wear, and had worn away from the supporting structure, allowing the hose liner to collapse and restrict airflow into the engine. Given this condition, the engine would have experienced a partial power loss due to the restricted airflow; damage signatures indicated that the engine was producing some power at the time of impact. The helicopter’s most recent annual inspection was completed about three months before the accident, and the worn hose should have been apparent at the time of the inspection.

Automatic Dependent Surveillance-Broadcast (ADS-B) data indicated that, before the accident, the helicopter was traveling at a speed and altitude such that, in the event of an engine failure, the pilot would have had limited time to enter and establish a controlled autorotative descent. The helicopter’s operating handbook stated that, at low altitude and low speed, sufficient altitude may not be available to increase rotor rpm following a loss of engine power. Impact damage to the helicopter was consistent with an uncontrolled collision with terrain.

The helicopter was equipped with a current emergency locator transmitter (ELT), but it had been incorrectly installed inside the metal baggage compartment in a portable configuration and was not equipped with the required external antenna. Therefore, although the ELT activated, it’s signal was likely shielded by the metal compartment, and not received by search and rescue personnel. As a result, the helicopter was not discovered until the following morning. Even if the ELT signal had been received, the unit was not registered with the current owner; this could potentially have resulted in a delay as search and rescue personnel attempted to track down the owner and ascertain the validity of the alert.

Text from the NTSB. Open the NTSB docket for WPR20FA016 for the full record.