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Royal Navy Merlin Mk4 Helicopter Ditches During Night Exercise, One Serviceman Killed

By Drooid · · How we work

Fatal Crash Overview

On September 4 2024, a Royal Navy Merlin Mk4 helicopter operating from Royal Naval Air Station (RNAS) Yeovilton in Somerset conducted a night-flying training exercise. The aircraft, carrying three crew members, ditched deliberately in the sea about 25 nautical miles south of Lyme Regis, Dorset, at approximately 20:50 GMT. The right-hand seat pilot, Lt Rhodri Leyshon, sustained serious injuries and was unable to escape as the aircraft entered the water, resulting in his death.

Service Inquiry Findings

A formal service inquiry examined the incident and identified a mechanical fault as a primary factor. The inquiry reported that a diaphragm inside the engine split, allowing fuel to leak into the engine and cause it to run at an excessively high speed. Misinterpreting the situation, the crew manually shut down the number one and number three engines, believing they had failed. This action triggered the remaining engine to exceed its “overspeed trip threshold,” leading to its automatic shutdown. The loss of power from all three engines forced the helicopter to descend into the sea.

Technical Cause Summary

  • Engine diaphragm rupture -> fuel ingress -> engine overspeed.
  • Crew response: manual shutdown of two engines based on erroneous assessment.
  • Result: automatic shutdown of the third engine and total loss of thrust.

Impact and Official Response

The incident underscores the risks inherent in night-time maritime helicopter operations and highlights the importance of accurate engine-failure diagnostics. The Royal Navy has initiated a review of training protocols for emergency engine failures and is assessing whether additional safeguards or procedural changes are needed to prevent similar misinterpretations in future exercises.

Future Actions

The service inquiry’s recommendations will be forwarded to senior naval leadership for implementation. A timetable for any procedural revisions or technical modifications has not yet been announced, but the Navy has indicated that corrective measures will be pursued promptly to enhance flight-safety standards.