FlySafair Boeing 737-400 Emergency Descent at George Aerodrome (ZS-OAF)

Incident Overview and Flight Details On 22 November 2020, FlySafair flight FA146, operating a Boeing 737-400 with registration ZS-OAF, departed Cape Town International Aerodrome (FACT) for East London Aerodrome (FAEL). The aircraft carried six crew members and 158 passengers. During the climb to its assigned cruising altitude of 33,000 feet, the crew encountered a cabin depressurisation warning. The cabin altitude was recorded at 10,000 feet and climbing at approximately 700 feet per minute. The crew subsequently broadcast a Cabin Altitude Warning and declared a Mayday, requesting an emergency descent. ## Emergency Descent and Diversion Following the warning, the aircraft commenced an emergency descent to 10,000 feet. The area controller, who had the aircraft on primary surveillance radar, inquired whether the crew intended to return to Cape Town. The crew opted to divert to George Aerodrome (FAGG), as it was the closest suitable aerodrome available at the time. The aircraft landed at George Aerodrome at 0820Z. ## Injuries and Aircraft Damage Following the emergency descent, nine passengers required medical attention or reported symptoms. One passenger required medical attention, three complained of nosebleeds, and five suffered from severe ear pain. All medical treatments were classified as minor. No fatalities were reported, and the aircraft sustained minor damage. ## Probable Cause The investigation concluded that the serious incident was likely the result of two primary failures. First, the air/ground proximity sensor became defective, causing certain cockpit cues to remain in ground mode and triggering warning lights that required crew intervention. Second, a loss of cabin pressure occurred due to air leaking from the fuselage, including a worn seal on the aft cargo compartment door. This situation was further aggravated by a fracture in the left air-conditioning pack outlet duct in a previously repaired area, which reduced the air supply to the system.