Engine Power Loss Leads to Autorotation and Crash of Kit Helicopter near Koblenz-Winningen

Casualties unknown • Nahe Flugplatz Koblenz-Winningen, DE

A RotorWay Exec 162F kit helicopter experienced a sudden loss of engine power and rotor RPM during a training flight, resulting in a forced autorotation and heavy damage.

What happened

On March 25, 2018, a pilot and a passenger were conducting a training flight in a homebuilt RotorWay Exec 162F helicopter. The flight originated from the Koblenz-Winningen airfield (EDRK) with the intention of practicing emergency procedures and autorotations. After performing maneuvers at a landing site in Ochtendung, the crew began the return flight to Koblen and Winningen.

At approximately 18:17 local time, while on the right-hand base leg for runway 24 near the village of Bisholder, the helicopter experienced a sudden loss of engine power and a drop in main rotor RPM. Although the pilot attempted to manually increase the governor by advancing the throttle to its limit, the engine speed failed to recover. The pilot issued an emergency call to the Koblenz-Winningen flight controller and initiated an autorotation from an altitude of approximately 900 feet AGL. The helicopter struck a sloping meadow near a power line, causing the aircraft to tip onto its side. Both occupants were able to exit the heavily damaged aircraft without injury.

The investigation

The BFU examined the wreckage and the engine components. An inspection of the piston engine, including spark plugs, valves, and a borescope examination of the combustion chambers, revealed no signs of internal damage or mechanical failure. However, investigators found that the two fuel filters were heavily contaminated. A portion of the debris in the filters appeared to be black plastic, similar in composition to the material used for the fuel tanks.

Additionally, investigators discovered a missing stop screw at the throttle linkage. While the pilot believed this screw was present during the initial assembly of the helicopter, its absence was noted during the post-crash inspection. The manufacturer stated that, contrary to technical drawings, this specific stop screw is not installed in their units.

Findings

  • The primary cause of the power loss was heavy contamination within the fuel filters, which included plastic debris resembling the tank material.
  • The absence of the throttle stop screw was noted, though its impact on the specific sequence of the engine failure could not be definitively determined.
  • The aircraft was a homebuilt unit with approximately 30 flight hours since its initial flight authorization.

Probable cause

The engine power loss and subsequent loss of rotor RPM were caused by significant contamination in the fuel filters, which included plastic particles likely originating from the fuel tanks.

Frequently asked questions

What happened in the 2018-03-25 Eigenbau RotorWay Exec 162F accident near Nahe Flugplatz Koblenz-Winningen, DE?

A RotorWay Exec 162F kit helicopter experienced a sudden loss of engine power and rotor RPM during a training flight, resulting in a forced autorotation and heavy damage.

What aircraft was involved and where did it happen?

The accident on 2018-03-25 involved a Eigenbau RotorWay Exec 162F, at Nahe Flugplatz Koblenz-Winningen, DE.

What was the probable cause of the accident?

The engine power loss and subsequent loss of rotor RPM were caused by significant contamination in the fuel filters, which included plastic particles likely originating from the fuel tanks.

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