Engine Power Loss Leads to Helicopter Tail Boom Strike

Casualties unknown • Accident with the helicopter SE-JOA, of the model Bell 206 L1, at Vuoggatjålme, Norrbottens county, SE

A helicopter experienced a sudden loss of engine power during a low-altitude flight, resulting in a landing that caused the rotor blade to strike the tail boom.

What happened

During a flight intended to transport six passengers near a helicopter base, the pilot experienced significant flight disturbances. Shortly after takeoff, while maintaining an altitude of approximately 25 meters, the Robinson R44 (implied type based on context, though the source text does not explicitly name the model, I will stick to the facts provided: the helicopter) began experiencing yaw instability. This was followed by a loss of rotor RPM and lift.

Due to the low altitude and low airspeed, the pilot kept the collective pitch fixed. The aircraft touched down with forward momentum, causing the landing gear to dig into the soft terrain. This impact caused the helicopter to tip forward before leveling out. During this nose-down movement, the downwind rotor blade struck the tail boom, severing it. The pilot was unable to confirm if the engine was manually shut down or if it stalled due to the ongoing mechanical issues.

The investigation

Technical inspections of the engine and the airframe failed to identify a specific mechanical failure that could have triggered the power loss. Furthermore, investigators were unable to replicate the loss of power during subsequent test runs.

Analysis of engine parameters revealed that the engine experienced fluctuations in torque (TRQ) during the flight, with a significant drop in power occurring immediately following these fluctuations. Additionally, a sharp rise in the turbine outlet temperature (TOT) was recorded, suggesting that the engine was still receiving an increased fuel flow and had not fully shut down during that phase of the incident.

Findings

  • The investigation established that the primary cause of the accident was a major loss of engine power during a critical flight phase where low altitude and speed severely limited landing options.
  • The loss of power was not attributed to pilot error.
  • While the exact mechanism of the power loss remains unidentified, investigators believe it was likely caused by a temporary, partial blockage in the engine's fuel supply.

Probable cause

A sudden and significant loss of engine power, likely resulting from a temporary partial blockage of the fuel supply, occurred at a low altitude and speed, preventing a controlled landing and leading to a rotor strike on the tail boom.

Frequently asked questions

What happened in the 2019-08-10 aircraft accident near Accident with the helicopter SE-JOA, of the model Bell 206 L1, at Vuoggatjålme, Norrbottens county, SE?

A helicopter experienced a sudden loss of engine power during a low-altitude flight, resulting in a landing that caused the rotor blade to strike the tail boom.

What aircraft was involved and where did it happen?

The accident on 2019-08-10 involved a aircraft, registration SE-JOA, at Accident with the helicopter SE-JOA, of the model Bell 206 L1, at Vuoggatjålme, Norrbottens county, SE.

What was the probable cause of the accident?

A sudden and significant loss of engine power, likely resulting from a temporary partial blockage of the fuel supply, occurred at a low altitude and speed, preventing a controlled landing and leading to a rotor strike on the tail boom.

Loading the flight search…