Introduction
On 24 March 2013, an Avro 146-RJ100 aircraft, registration HB-IYY, operated by Swiss European Air Lines under call sign SWR35R, was involved in a serious incident near waypoint LUSAR, approximately 50 nautical miles northwest of Geneva Airport. The event was investigated by the Swiss Transportation Safety Investigation Board (STSB).
Incident Details
The serious incident occurred during a flight from London City Airport to Geneva. According to the safety board's final report, the aircraft experienced a loss of control of the pneumatic supply system. This system is critical for regulating cabin pressure through control of the cabin pressure outflow valves. The investigation noted that a prior incident had occurred on 8 March 2013 involving the same aircraft, and a first flight on 24 March 2013 from Geneva to Nice had been conducted before the event flight.
Investigation Findings
The investigation determined that the loss of control was most likely due to two factors: icing of the pneumatic lines that control the cabin pressure valves, and excessive friction that impaired the function of the secondary cabin regulation valve. These conditions disrupted the normal operation of the pressurization system. The aircraft's cabin pressure control system (CPC) and associated outflow valves were examined, and the findings pointed to the pneumatic supply system as the origin of the malfunction.
Probable Cause
Probable cause: The serious incident was caused by a loss of control of the pneumatic supply system, most likely resulting from icing of the pneumatic lines of the control system for the cabin pressure valves and excessive friction that impaired the function of the secondary cabin regulation valve.