Open door in rain led to dangerous chain reaction on Boeing 747

Water entered a Boeing 747-400 through a door left open during overnight maintenance in heavy rain, leading to a chain of electrical failures on a freighter flight from London Heathrow to Hong Kong on 8 February 2024, according to a final report by the UK Air Accidents Investigation Branch.

During the takeoff roll, the crew received the first fault message. More followed during the climb. Several systems failed. The autopilot later commanded a descent of almost 2,000 metres per minute, and the crew struggled with unreliable airspeed indications.

The aircraft, registered G-ONEE and operated by One Air, had five crew members on board and was flying without cargo. Investigators found that maintenance had been performed overnight with the forward left door open. Heavy rain fell during the last two hours of that work, with wind blowing toward the open door. Crew later noticed water on the door mat and cabin floor, and water was subsequently found in two areas of the electrical power supply beneath the cargo floor. The open door was the only identifiable source of the water ingress.