What happened
On September 22, 2015, an Embraer SB20, registration HB-IZP, was performing a commercial ferry flight from Geneva to Rome. While cruising at flight level 270, the flight crew observed a rapid increase in cabin altitude, accompanied by a "CAB ALT HI" warning message. As the cabin altitude climbed above 14,000 feet, the "PAX OXY ACTIVATED" alarm illuminated, prompting the two pilots to don their oxygen masks.
The crew declared a MAYDAY and initiated an emergency descent to flight level 100. During the descent, the crew executed the rapid decompression checklist. Once the aircraft reached 14,000 feet, the pilots removed their masks and stabilized the aircraft in cruise at the lower altitude. After canceling the distress call, the crew elected to continue the flight to their destination. There were no passengers on board during this operation, and no injuries were reported.
The investigation
Following the incident, the aircraft was repositioned to Geneva without pressurization for technical evaluation. Initial maintenance efforts included replacing the exhaust regulating valve and performing a visual inspection. The crew also replaced the computer responsible for cabin pressure control; however, a subsequent test flight revealed that the sudden loss of pressure persisted.
Further investigation focused on the aircraft fuselage. Inspectors discovered that the cargo door seal had become detached from its housing along a section approximately 40 cm in length. The displacement of the seal was caused by the internal cabin overpressure.
Findings
- The primary cause of the rapid decompression was the failure of the cargo door seal, which had partially popped out of its track.
- The internal pressure within the cabin forced the upper portion of the seal out of its seating, creating a leak path.
- The aircraft was returned to service after the seal was re-adhered to its original position and a successful check flight was completed.