What happened
On February 27, 2020, a SpiceJet Boeing 737-800, registration VT-SXE, was operating a scheduled passenger flight from Mumbai to Varanasi. During the initial climb phase, the crew observed the #1 Bleed Trip Off annunciator. Following standard non-normal checklists, the crew deactivated the #1 pack, allowing the flight to proceed using a single pack system.
While descending from 37,000 feet, the flight crew noticed a steady rise in cabin altitude. As the aircraft passed 33,200 feet, the cabin altitude horn activated. The crew immediately declared a "MAYDAY," donned oxygen masks, and initiated an emergency descent to 10,000 feet. During the descent, oxygen masks were deployed for the passengers. Once the aircraft reached a safe altitude and cabin pressure was stabilized, the crew cancelled the distress situation and landed safely at Varanasi Airport. There were no injuries to the 191 passengers or the six crew members on board.
The investigation
The AAIB India investigation examined the aircraft's pneumatic system, maintenance history, and flight data. Investigators reviewed the aircraft's technical logs, which revealed a recurring pattern of issues regarding the Pneumatic Control Component Valves (PCCV). The investigation scrutinized the serviceability of the bleed air system and the recent maintenance actions taken on the engine bleed components.
Findings
- The aircraft experienced an uncontrolled cabin pressurization event during descent.
- The crew successfully managed the emergency by performing the required non-normal checklists and executing a rapid descent.
- Maintenance records indicated a high failure rate and frequent replacements of the PCCV components across the fleet.
- Recent logs for VT-SXE showed that the #1 bleed trip light had illuminated during a previous climb, leading to the use of a single pack for the remainder of the flight.