One Air 747-400 crew praised after electrical failure and depressurisation

A One Air Boeing 747-400 freighter diverted to Amsterdam Schiphol after a cascade of technical failures on 8 February 2024, a UK Air Accident Investigation Branch inquiry found. The aircraft had departed London Heathrow for Hong Kong. The crew landed safely.

Rainwater entered through a forward door left open during maintenance and reached generator control units below the main deck. Two AC electrical busses were lost during takeoff and climb. The failures caused multiple warning messages and loss of pitot-tube heating.

The crew levelled at 25,000ft to run checklists and decided to divert to Amsterdam. A stuck outflow valve then triggered a depressurisation alert, prompting a descent. At 12,000ft the aircraft entered icing conditions, and the unheated pitot tubes froze. All three airspeed indicators began reading erroneously low.

With the autopilot in flight-level change mode, the aircraft pitched nose-down 7.6 degrees to correct the apparent speed loss. Descent rate increased to 6,240ft/min and the aircraft experienced an 18kt overspeed. After leaving icing conditions, airspeed indications recovered and the autopilot pitched up.

The crew declared an emergency and, after dealing with a flap issue, landed safely in Amsterdam. The inquiry praised the crew's structured response to the failures.