What happened
On March 2, 2025, a Boeing 737-4H6, registration YV622T, was operating a scheduled passenger flight from El Dorado International Airport (SKBO) in Bogotá, Colombia, to Arturo Michelena International Airport (SVVA) in Valencia, Venezuela. The aircraft was carrying 108 passengers and 9 crew members.
Shortly after takeoff from runway 14L, as the aircraft climbed through 16,000 feet, the crew received a cabin altitude warning and a depressurization emergency light. This was accompanied by the deployment of oxygen masks in the cabin. The flight crew immediately notified Air Traffic Control (ATC), requested priority for a return to Bogotá, and set the transponder to emergency code 7700.
During the descent and approach to runway 14R, the crew performed a stabilized approach bypass due to the unstable nature of the approach. The cabin altitude warning light illuminated again once the aircraft reached 14,000 feet. The aircraft landed safely without further incident, and all 117 occupants remained uninjured.
The investigation
The GRIAA investigation included interviews with the flight crew and cabin attendants, as well as technical inspections of the aircraft's pneumatic and oxygen systems. Investigators performed troubleshooting on the engine bleed air systems and conducted leak checks using the APU.
Technical examinations of the oxygen system revealed that several oxygen masks failed to deploy, specifically in seats 2C, 11C, 12E, 24C, 25C, 28, the rear left lavatory, and the position of the second flight attendant. Additionally, while reviewing the flight data recorder (FDR), investigators identified pneumatic leaks in the PRSOV sensor line and a TEE fitting during maintenance testing.
Findings
- The primary cause of the incident was a failure in the aircraft's pressurization system.
- Inspections of specific components identified potential faults, including a leak in the valve body of the Pressure Regulator and Shutoff Valve (PRSOV), excessive flapper movement in the Fan Air/Precooler, and a diaphragm leak in the Valve Fan Air/Pre-cooler.
- A pneumatic leak was confirmed in the sensor line of the PRSOV and at a TEE fitting connected to the valve.
- Certain oxygen masks failed to deploy during the depressurization event.