FlySafair Boeing 737-400 Emergency Descent After Rapid Decompression (ZS-JRM)

Incident Overview On 20 August 2019, a FlySafair Boeing 737-400 with registration ZS-JRM departed Cape Town International Aerodrome (FACT) on a scheduled domestic flight to King Shaka International Aerodrome (FALE). The aircraft carried two pilots, four crew members, and 134 passengers. ## Emergency Descent At approximately 1825Z, while climbing through flight level 310, the crew declared an emergency by broadcasting a Mayday. Both pilots reported hearing two loud thuds from the rear of the aircraft. The pressurisation gauge then showed a gradual increase in cabin altitude, which quickly became uncontrollable, triggering the Cabin Altitude Warning System. The aircraft was cleared for an unrestricted emergency descent. Oxygen masks deployed automatically in the cabin, and the cockpit crew fitted their oxygen masks. At approximately 1831Z, the crew levelled off at flight level 100 and was vectored back to Cape Town. ## Landing and Inspection The aircraft landed safely on Runway 19 at approximately 1857Z. No one on board was injured. After stopping on the runway, the crew requested an external inspection. Aerodrome rescue and fire-fighting personnel found no external damage, and the aircraft taxied to its parking bay. ## Investigation Findings The investigation determined that the rapid decompression resulted from the failure of the lower part of the aft cargo door pressure seal. This allowed pressurised cabin air to leak into the atmosphere faster than the pressurisation system could compensate, preventing the aircraft from maintaining a safe and comfortable environment.