ASN Wikibase Occurrence # 249444
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| Date: | Sunday 22 November 2020 |
| Time: | 08:20 UTC |
| Type: |  Boeing 737-4S3 |
| Owner/operator: | Safair |
| Registration: | ZS-OAF |
| MSN: | 25116/2061 |
| Year of manufacture: | 1991 |
| Fatalities: | Fatalities: 0 / Occupants: 162 |
| Aircraft damage: | Unknown |
| Category: | Serious incident |
| Location: | near George -
 South Africa
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Cape Town International Airport (CPT/FACT) |
| East London Airport (ELS/FAEL) | |
| Investigating agency: | CAA S.A. |
| Confidence Rating: |  Accident investigation report completed and information captured |
The crew of ZS-OAF was preparing to taxi for take-off from Cape Town International Airport to East London Airport. Before taxi, one of the crew members reported that she thought that doors number 1R and 2R ware not closed properly. The doors were disarmed, and technicians were asked to check if the doors were closed from outside. The doors were opened and closed 3 times before it could be confirmed that they were closed properly. The technicians confirmed that both doors looked closed from the outside.
The aircraft routed via VORs. GRV, PEV, ELV. When the aircraft was passing 32500 feet (ft), there was a cabin altitude warning and the cabin altitude was at 10 000 ft. Cabin climbing was at approximately 700 ft per minute. The crew commenced with memory item and decided to not deploy masks to avoid causing panic because the nature of the leak was slow. Maximum cabin was approximately 12 500 ft. The out-flow valve was fully closed already when they went to manual mode during memory items. During decent, the low idle light illuminated.
The pilot added a little bit of thrust to extinguish the light and then descended to 10000ft and assessed the situation. A very loud noise was heard from 1 of the left doors and the crew descended to 8 000 ft at GRV, in a hold. The pilot broadcasted a mayday call and commenced the approach. The aircraft landed safely in George.
Fire trucks and medical personnel were on standby but were not used. Cabin crew confirmed no one required medical assistance. There were 3 pax with nose bleeds and 5 with ear pain.
The Aircon Bay Pack/Machine Compressor Outlet Duct Assembly that was installed on the left air-conditioning pack was found to have fractured in an area that was subjected to a previous welding repair.
Probable Cause
It is likely that this serious incident occurred as a result of the following failures:
(i) The air/ground proximity sensor becoming defective, which rendered certain cues to remain in ground mode and causing certain warning lights to illuminate in the cockpit which required crew intervention, whilst certain cues functioned normally.
(ii) Loss of cabin pressure, which was attributed to air leaking from the fuselage, including the aft cargo compartment door seal that was worn out. This situation was further aggravated by the left air-conditioning pack outlet duct fracture in an area that was previously repaired, which resulted in reduced air supply to the system.
Accident investigation:
 |
|
Sources:
http://www.caa.co.za/Latest%20Accident%20Reports/Interim%20Report%20-%20ZS-OAF.pdf
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 04-Apr-2021 19:29 | harro | Added |
| 10-Feb-2022 10:15 | harro | Updated [Time, Total occupants, Source, Embed code, Narrative] |
| 15-Apr-2022 08:51 | harro | Updated [[Time, Total occupants, Source, Embed code, Narrative]] |
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