What happened
On November 21, 2007, an Airbus A330-202, registration F-WWKK, was conducting a delivery flight demonstration for Air Mauritius. While cruising at FL 410 over southern France, a flight test engineer began verifying the cabin pressurization systems. During the transition between controllers, the outflow valves (OFV) unexpectedly opened to their maximum position.
The rapid loss of pressure caused the cabin altitude to climb sharply, reaching approximately 30,000 feet. The sudden depressurization resulted in barotrauma for the pilot and caused three individuals to lose consciousness because they could not don oxygen masks quickly enough. The flight crew initiated an emergency descent, manually managing the outflow valves to attempt to stabilize the cabin. After the crew successfully restored pressure regulation by switching to the secondary controller, the aircraft stabilized at FL 100 and proceeded to Toulouse.
The investigation
The BEA examined the flight data recorders and the non-volatile memory of the cabin pressure controllers (CPC). The investigation established that after a period of normal operation, the active controller commanded the outflow valves to open at maximum speed. Investigators identified an abnormal angular displacement in the valve position just prior to the rapid opening.
Further testing using a test bench demonstrated that this malfunction—characterized by the rapid, full opening of the valves—could be reproduced by inducing memory corruption within the controller. The investigation also noted that the presence of several extra personnel in the cockpit and near the cockpit entrance, combined with the fact that oxygen generators were in a test configuration, exacerbated the impact of the event.