Incident Overview
On 12 December 2006, an Avro 146-RJ100 aircraft, registration HB-IXU, operated by Swiss European Airlines as flight LX1105, was involved in a serious incident approximately 20 km north of Kempten, Germany, while at flight level 200 (FL200). The event was investigated by the Swiss Bureau d’enquête sur les accidents d’aviation (BFU).
Aircraft and Crew
The aircraft was an AVRO 146-RJ100 with the registration HB-IXU. The flight was operated by Swiss European Airlines AG. Details of the crew composition and their experience are documented in the full report but are limited to factual statements. The aircraft was equipped with a pneumatic system for air conditioning and pressurization.
Sequence of Events
According to the investigation, the cockpit crew did not engage the air conditioning and pressurization system after starting the engines. This oversight was not noticed during the subsequent climb. The cabin altitude warning system failed to alert the crew because the cabin altitude warning switch (cabin altitude warning switch) was defective and could not trigger the CABIN HI ALT warning.
Investigation Findings
The BFU identified that a defective cabin altitude warning switch prevented the activation of the cabin altitude warning. Additionally, the procedures and checklists used by the airline were found to be not well adapted to the complexity of the onboard pneumatic system. These factors contributed to the crew's failure to detect the omission.
Causes
The direct cause of the serious incident was the crew's failure to activate the air conditioning and pressurization system after engine start and their subsequent failure to notice this during climb. Contributing factors included a defective cabin altitude warning switch that could not trigger the CABIN HI ALT warning, and inadequate procedures and checklists that did not properly address the complexity of the pneumatic system.