What happened
On 12 July 2006, an Airbus A321-231, registration G-MIDJ, was performing a public transport flight descending from FL310 toward London Heathrow. Shortly after the descent began, the aircraft's air conditioning packs ceased operation, accompanied by an 'ENG 1 BLEED LEAK' caution. As the aircraft descended, the cabin altitude rose at a rate of approximately 1,000 ft/min, eventually exceeding 10,000 ft.
Upon reaching 10,000 ft, a 'CAB PR EXCESS CAB ALT' warning illuminated. In response to the rising cabin altitude, the crew donned oxygen masks and deployed the passenger oxygen masks. The commander notified Air Traffic Control of the pressurisation issue and requested a descent to FL200. After completing the necessary Electronic Centralised Aircraft Monitoring (ECAM) procedures, the crew descended further to FL80, at which point they determined it was safe to remove their masks and briefed the cabin crew to do the same. The flight continued with a controlled descent rate of 70 and landed safely at Heathrow with no injuries to the 125 passengers or 5 crew members.
The investigation
The investigation established that the aircraft had a history of intermittent bleed problems dating back to late June 2006, though previous inspections had not identified a permanent fault. Following the incident, ground inspections revealed air leaks in both air conditioning packs. Maintenance crews also identified and rectified several other defects, including issues with the No 2 engine bleed, its shut-off valves, and the engine transducer. Additionally, seals on both engines were replaced to ensure system integrity.
Findings
- The primary cause of the cabin altitude increase was air leaks associated with both air conditioning packs.
- The aircraft had previously experienced intermittent bleed-related issues that had not been definitively resolved.
- Ground checks also identified and corrected faults regarding engine seals and the engine transducer.