Royal Navy Pilot Died After Crew Mistakenly Shut Down Engines During Emergency

A Royal Navy pilot, Lieutenant Rhodri Leyshon, 31, died when his Merlin Mk4 helicopter crashed into the English Channel during a night training exercise on September 4, 2024. A Defence Safety Authority inquiry determined that the accident began when a component failure in one engine caused excessive power output, leading to confusing cockpit warnings that led the crew to believe the other two, perfectly functional engines, had also failed. The crew then deliberately switched off the two serviceable engines.

Moments later, the malfunctioning engine automatically shut down after reaching its overspeed limit, leaving the helicopter without power. Investigators found the crew had initially planned a running landing on the carrier HMS Queen Elizabeth, a maneuver that would likely have succeeded.

The aircraft, ZJ135 of 846 Naval Air Squadron, was conducting deck-landing training approximately 25 nautical miles south of Lyme Regis. Lieutenant Leyshon was in the right-hand seat, with the aircraft commander on the left and an aircrewman in the rear. At 8:46 p.m., when the helicopter was at 125 feet above the sea, a rubber diaphragm in the No. 2 engine's fuel system split, increasing fuel flow and causing engine torque to exceed 136 percent.

The Merlin's automatic systems reduced power from engines No. 1 and No. 3 to manage rotor speed. However, the crew was faced with a master warning, an audible engine failure alert, and a red 'ENG FAIL' warning that did not clearly indicate the malfunctioning engine. The crew interpreted the low torque readings from engines one and three as evidence of their failure. Investigators noted that the cockpit alerts likely dominated Lieutenant Leyshon's attention, and he stated three times within 21 seconds that the helicopter was flying on one engine, an assessment not formally challenged by the other crew members.

A Mayday was declared reporting a double engine failure, and the crew began maneuvering toward the Queen Elizabeth for a running landing. Approximately one minute into the emergency, the aircraft commander discussed shutting down the two engines perceived as failed. The switches for engines one and three were moved directly from 'FLIGHT' to 'OFF' without the confirmation required by Merlin procedures for flight-critical switches. Once these engines were shut down, the faulty No. 2 engine accelerated until its protection system cut off the fuel supply. Attempts to restart the engines were unsuccessful.

Three minutes after the initial component failure, the Merlin struck the sea at approximately 62 knots while descending at nearly 2,000 feet per minute. The impact generated forces exceeding 10G, causing the main rotor to strike the water, the tail to break away, and the fuselage to overturn. The aircraft commander and aircrewman escaped, but Lieutenant Leyshon sustained serious injuries and was unable to exit the aircraft. He was recovered nearly two hours later and pronounced dead at a hospital.

The inquiry also highlighted concerns regarding training and flying currency. Both pilots needed to regain deck-landing currency, and the aircraft commander was not current for night-vision deck landings. He had not met the target of 15 flying hours per month in four of the preceding six months and had flown only once in the previous 40 days. Investigators concluded that a collective 'skill fade' very likely undermined the crew's ability to manage the emergency. The report also criticized crew coordination, finding that members worked in isolation rather than collectively challenging their diagnosis.

The initial fault was traced to a diaphragm in the No. 2 engine, weakened by an engineering procedure introduced by manufacturer Safran in 2020. Of 117 suspect diaphragms examined, ten showed potentially dangerous damage. The inquiry also found issues with crash protection, including Lieutenant Leyshon's energy-absorbing seat being set for a weight below his actual flying weight, and only two of the helicopter's four rear flotation bags operating as intended. The Defence Safety Authority has issued 44 recommendations covering engine maintenance, cockpit warning systems, pilot training, rescue equipment, and aircraft survivability.

Lieutenant Leyshon was remembered as a talented aviator and a keen rugby player. He had been associated with the Royal Navy for approximately 14 years, qualifying as a Commando Helicopter Force pilot in 2018 and deploying to various international locations. During the final 18 months of his career, he trained new aviators. His family described him as a 'talented, passionate, strong and loyal man.'