Loss of pressurization Serious incident Boeing 737-85F (WL) ZS-SJF,
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ASN Wikibase Occurrence # 247989
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Date:Monday 25 January 2021
Type:Silhouette image of generic B738 model; specific model in this crash may look slightly different    
Boeing 737-85F (WL)
Owner/operator:Mango Airlines
Registration: ZS-SJF
MSN: 30006/688
Year of manufacture:2000
Fatalities:Fatalities: 0 / Occupants: 125
Aircraft damage: None
Category:Serious incident
Location:NW of Durban -   South Africa
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Johannesburg-O.R. Tambo International Airport (JNB/FAOR)
Destination airport:Durban-King Shaka International Airport (DUR/FALE)
Investigating agency: CAA S.A.
Confidence Rating: Accident investigation report completed and information captured
A Boeing 737-800 aircraft with registration ZS-SJF operated by Mango Airlines as flight JE251 departed O.R. Tambo International Airport (FAOR) on a scheduled flight to King Shaka International Airport (FALE). On-board the aircraft were eight crew (two pilots and six cabin crew) members and 117 passengers. Before take-off, pressurisation and air-conditioning system switches were set in accordance with (IAW) pre-take-off checks. The aircraft climbed and levelled off at flight level (FL) 350. During descent to FALE and after passing FL270 at 1232Z, a “Cabin Altitude” warning light illuminated, followed by an aural warning. The crew declared an emergency by broadcasting a MAYDAY call to the area controller who had the aircraft on primary surveillance radar. The crew promptly donned their oxygen masks and manually deployed the passengers’ oxygen masks. The captain called for Cabin Alt warning checks as stipulated in the aircraft’s Quick Reference Handbook (QRH). The aircraft levelled off at FL090 and a normal landing was carried out on runway 24 at FALE.

After the incident the aircraft was test flown on 3 and 6 February before it resumed service on 7 February 2021.

Probable Cause/s
The aircraft was unable to maintain cabin pressure for a safe environment of the passengers and the crew members due to the right-side air-conditioning pack bleed air leak; the left-side pack was unable to compensate for a defective right-side pack due to the No.1 engine’s 9th stage bleed air valve being locked closed prior to departing FAOR.
Contributing factor/s:
Defective right-side air-conditioning pack components that included the primary heat exchanger, air cycle machine, sense line and the trim air check valve.

Accident investigation:
Investigating agency: CAA S.A.
Report number: 
Status: Investigation completed
Duration: 3 months
Download report: Final report



History of this aircraft

Other occurrences involving this aircraft
17 August 2015 ZS-SJF South African Airways 0 East London Airport (ELS/FAEL) min

Revision history:

19-Feb-2021 17:21 harro Added

Corrections or additions? ... Edit this accident description

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