Boeing 747 Cargo Plane Declares Mayday After Electrical Failures Cause False Airspeed Readings

A Boeing 747 cargo plane flying from London Heathrow to Hong Kong was forced to declare a mayday after electrical failures led to false airspeed readings, causing the aircraft to plummet at over 6,000ft per minute.

The incident occurred on February 8, 2024. Investigators found that water had entered the aircraft before departure due to a cargo door being left open during rain, which caused power to be cut to two of the plane's electrical systems.

The crew initially declared a PAN, signalling an urgent issue, and began diverting the aircraft to Amsterdam's Schiphol Airport. However, the situation became more serious when a pressurisation problem prompted the crew to initiate a descent through icy conditions.

As a result of the electrical failures and subsequent airspeed sensor issues, the autopilot engaged, attempting to increase speed by pointing the nose down. The aircraft entered a steep descent, reaching 6,240ft per minute with its nose pitched 7.6 degrees downwards.