A runaway pitch trim on a Dassault Falcon 7X caused a 40° pitch up, rapid climb and temporary loss of control, according to an invesitgation report released by BEA on a serious incident in Malaysia in 2011. This incident caused the temporary grounding of the Falcon 7X fleet.
On May 25, 2011, a Dassault Falcon 7X, HB-JFN, departed from Nuremberg, Germany on a ferry flight to Kuala Lumpur in Malaysia with two crew members on board.
While descending through 13000 feet, towards Kuala Lumpur, the elevator pitch trim began to move from neutral to the full nose-up position in 15 seconds time. This resulted in a sudden pith up of the aircraft to 40° and the aircraft entering a climb. Initially both the captain (Pilot Monitoring) and the copilot (Pilot Flying) were both using the side stick in an attempt to regain control. The copilot then used the priority button to override the captain’s side stick inputs and asked him to stop. The copilot, a former military pilot with experience on Mirage IV and Mirage 2000 jets, then put the aircraft in a right hand bank to a maximum of 98 degrees.
Eventually the pitch attitude decreased and the load factor decreased from 4,6 G to about 1.25 – 1.5 G. After 2 minutes and 35 seconds the crew were able to control the airplane again. Meanwhile, the aircraft had reaced an altitude of 22500 feet.
The day after the incident EASA published an Emergency Airworthiness Directive, grounding the Falcon 7X fleet until further notice. As of June 16, 2011 the ban was lifted for a number of aircraft. On July 7 the ban was lifted entirely.
The investigation, delegated by Malaysian authorities to BEA, concluded that there was a production defect in the Horizontal Stabilizer Electronic Control Unit (HSECU) due to defective soldering of a pin of this chip. This caused erroneous orders to be sent to the Tail Horizontal Stabilizer trim.
- BEA report (PDF)