Royal Navy Helicopter Crash Killed Pilot After Crew Mistakenly Switched Off Engines, Inquiry Finds

A Royal Navy pilot, Lieutenant Rhodri Leyshon, 31, was killed when his Merlin Mk4 helicopter crashed into the English Channel during a night training exercise on September 4, 2024. An inquiry by the Defence Safety Authority found that the accident began when a component failure in one engine caused confusing cockpit warnings, leading the crew to believe the other two engines had failed. Consequently, the crew deliberately switched off the two serviceable engines, leaving the aircraft dependent on the malfunctioning one.

Seconds later, the faulty engine shut down automatically after exceeding its operational limits, resulting in a complete loss of power. Investigators determined that the crew had initially planned a running landing on the carrier HMS Queen Elizabeth, a maneuver that would likely have been successful. However, the decision to shut down the healthy engines without proper confirmation, as required by procedure, sealed the aircraft's fate.

The helicopter, part of 846 Naval Air Squadron, was conducting deck-landing training approximately 25 nautical miles south of Lyme Regis. During the emergency, Lieutenant Leyshon reported the helicopter was flying on one engine, an assessment that went unchallenged by other crew members. A Mayday call was made, reporting a double engine failure.

The inquiry revealed the initial fault stemmed from a split rubber diaphragm in the No2 engine's fuel system, exacerbated by an engineering procedure introduced by the manufacturer in 2020. A subsequent examination of suspect diaphragms revealed potentially dangerous damage in ten instances.

Investigators also raised concerns about crew coordination and pilot readiness. They noted that both pilots needed to regain deck-landing currency, and the aircraft commander was not current for night-vision deck landings. The commander had also failed to meet monthly flying hour targets in four of the preceding six months and had flown only once in the previous 40 days. The report suggested that collective "skill fade" likely impacted the crew's ability to manage the emergency.

During the crash, the aircraft struck the sea while descending rapidly, generating forces exceeding 10G. The main rotor impacted the water, the tail separated, and the fuselage overturned. While the aircraft commander and an aircrewman escaped, Lieutenant Leyshon was unable to exit the aircraft. He was recovered nearly two hours later and pronounced dead at a hospital. His energy-absorbing seat was also found to be set incorrectly for his weight, and only two of the helicopter's four rear flotation bags functioned as intended.

The Defence Safety Authority has issued 44 recommendations covering areas such as engine maintenance, cockpit warning systems, pilot training, rescue equipment, and aircraft survivability.

Lieutenant Leyshon was remembered as a talented aviator, a keen rugby player, and a proud Welshman with approximately 14 years of service in the Royal Navy. He qualified as a Commando Helicopter Force pilot in 2018 and served in various deployments. His commanding officer described him as a "consummate professional and a shining light with a bright future."