Flight DT-579 | Registration: D2-TBG
Date: 2 December 2024 | Location: Enroute near Windhoek, Namibia
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Introduction
On 2 December 2024, a TAAG Angola Airlines Boeing 737-700, registration D2-TBG, operating flight DT-579 from Luanda (FNLU), Angola, to Cape Town (FACT), South Africa, experienced a significant cabin pressurisation failure while cruising at FL370. The aircraft was approximately 350 nautical miles north of Windhoek, Namibia, when the crew initiated an emergency descent to FL100 following an uncontrollable rise in cabin altitude.
The incident led to the activation of oxygen masks and a diversion to Windhoek Hosea Kutako International Airport (FYWH). Seven people sustained minor injuries during the descent and emergency procedures. The aircraft landed safely, and emergency services were on standby.
Namibia’s Ministry of Works and Transport released a preliminary report on 3 April 2025 detailing the sequence of events and initial findings from the ongoing investigation.
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Flight Details
• Aircraft Type: Boeing 737-7M2
• Engines: 2 × CFM56-7B24
• Operator: TAAG Angola Airlines
• Registration: D2-TBG
• Flight Number: DT-579
• Callsign: DTA579
• Date of Occurrence: 2 December 2024
• Departure Airport: Luanda Quatro de Fevereiro International Airport (FNLU), Angola
• Intended Destination: Cape Town International Airport (FACT), South Africa
• Diversion Airport: Windhoek Hosea Kutako International Airport (FYWH), Namibia
• Phase of Flight: Cruise (FL370)
• Occupants: 99 (93 passengers, 6 crew)
• Injuries: 7 minor (1 flight crew, 1 cabin crew, 5 passengers)
• Fatalities: None
• Damage to Aircraft: None reported
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Sequence of Events
While cruising at FL370 over Namibia, the aircraft’s cabin altitude warning system activated, indicating that the cabin altitude had exceeded the safe threshold of 10,000 feet. The associated warning horn sounded in the cockpit, prompting the crew to initiate emergency procedures. Despite following the SOPs, the cabin altitude continued rising, eventually reaching 15,000 feet.
In response to the uncontrollable pressurisation issue, the flight crew declared an emergency and requested descent clearance from Windhoek ATC. An emergency descent was initiated to FL100, and the oxygen masks were deployed. However, only 46% of the cabin oxygen masks reportedly deployed successfully, a significant anomaly currently under investigation.
The aircraft diverted to Windhoek’s Hosea Kutako International Airport, where it landed without further incident at 11:15 UTC (13:15 local time). Emergency services were on standby, and all occupants were safely evacuated. Medical staff attended to the seven individuals who sustained minor injuries, likely from rapid descent effects and oxygen mask deployment issues.
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Technical Findings and Initial Analysis
Namibia’s Ministry of Works and Transport preliminary report confirmed the following:
• The Right Environmental Control System (ECS) Pack was inoperative for the entire flight.
• The Left ECS Pack, the sole functioning unit, failed during cruise, resulting in the complete loss of cabin pressurisation.
• As cabin altitude exceeded 10,000 feet and continued to rise beyond 15,000 feet, the automatic cabin pressure control system failed to compensate, triggering the warning systems.
• Oxygen masks were deployed, but less than half (46%) functioned correctly—raising serious concerns regarding the aircraft’s emergency oxygen system reliability.
• The aircraft’s descent profile during the emergency was consistent with standard Boeing procedures for decompression events.
The malfunction of both ECS packs represents a dual pack failure, a rare but serious event, as these systems are vital for maintaining safe cabin conditions at cruising altitude.
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Post-Incident Aircraft Status
• The aircraft remained grounded in Windhoek from 2 December to 23 December 2024, during which thorough diagnostics and component replacements were likely conducted.
• It then positioned to Luanda and resumed commercial operations on 7 January 2025.
• Investigations into the failed ECS packs, particularly the root cause of the left pack failure, are ongoing.
• The oxygen mask deployment issue is being treated as a separate but serious system malfunction.
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Cabin Pressure System Overview (Boeing 737-700)
The Boeing 737-700 is equipped with two ECS packs responsible for pressurising and ventilating the cabin. A failure of one pack is normally not hazardous; the aircraft can maintain safe pressurisation with a single functioning pack. However, dual pack failure, particularly during high-altitude cruise, is an emergency scenario necessitating a descent to below 10,000 feet.
The cabin pressure control system is automated, but pilots can manually intervene using the manual pressurisation mode in case of failure. In this case, the automated system failed to prevent pressure loss, and the crew’s descent was the only viable mitigation.
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Injuries and Safety Concerns
Seven individuals—comprising one pilot, one flight attendant, and five passengers—suffered minor injuries. These injuries were likely due to:
• Rapid cabin depressurisation effects
• Oxygen deprivation during the descent
• Improper or delayed oxygen mask use
• Malfunctioning oxygen masks
The reported failure of over half the cabin oxygen masks to deploy is now a focal point of the investigation, as it poses a direct threat to passenger safety during high-altitude depressurisation events.
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Ongoing Investigation
The Namibian accident investigation authority, in coordination with TAAG Angola Airlines and Boeing, is focusing on the following:
• Root cause of the Left ECS Pack failure
• Maintenance history and deferred defect procedures related to the Right ECS Pack
• Cabin oxygen mask system maintenance and deployment performance
• Compliance with minimum equipment list (MEL) provisions that permitted dispatch with one inoperative ECS pack
• Flight crew actions and adherence to decompression protocols
Preliminary results suggest procedural adherence by the flight crew. The cabin system failures, however, raise questions about aircraft airworthiness and maintenance oversight.
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Summary and Safety Implications
The 2 December 2024 incident involving TAAG’s Boeing 737-700 underscores the critical role of redundant pressurisation systems and emergency oxygen provisioning. While the crew’s swift actions prevented a more severe outcome, the partial failure of the oxygen mask system poses serious safety concerns.
This event highlights the risks of dispatching aircraft with degraded environmental systems under MEL exemptions and reinforces the need for enhanced reliability monitoring and preventative maintenance of life-critical systems such as ECS and cabin oxygen distribution.
The investigation remains ongoing, and a final report with safety recommendations is expected in due course.
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Disclaimer
This report is based on publicly available information and preliminary findings as of 4 April 2025. Further details may emerge as the investigation progresses. If you are the rightful owner of any referenced material and wish to request takedown, please email takedown@cockpitking.com.
