What happened
On 2 July 2012, an AVRO 146-RJ100, registration HB-IXW, was climbing through flight level 244 near Rolampont, France, when a significant technical failure occurred. A defect in the right bleed air system triggered several warning lights, including high-temperature indicators and valve closure alerts. Shortly thereafter, the cabin altitude began to rise rapidly, signaling a loss of pressurization.
In response to the rising cabin altitude, the flight crew initiated an emergency descent. During the descent, passenger oxygen masks were deployed, and the crew transitioned the aircraft' and transponder to emergency code A7700. The crew faced communication difficulties with air traffic control due to the use of oxygen masks. The aircraft eventually reached a safe altitude of flight level 100, after which the crew decided to return to Zurich for landing.
The investigation
The Swiss Accident Investigation Board (SAIB) examined the technical failure of the aircraft's air supply and pressurization systems. The investigation focused on the sequence of events leading to the loss of pressure, the functionality of the air conditioning packs, and the mechanical cause of the bleed air leak. Investigators also reviewed the crew's response to the emergency and the operational status of the aircraft's air conditioning components prior to departure.
Findings
- The primary cause of the serious incident was a defect in the right bleed air system that led to a complete failure of the cabin pressurization system at flight level 244.
- A contributing factor was that the air conditioning pack 1 had been deactivated before the flight commenced.
- A leak was identified in the bleed air duct located near the engine number 4 pylon, specifically involving a broken clamp.