What happened
On April 30, 2023, at 20:46 UTC, a Boeing 737-4H6, registration YV621T, operated by Turbial Airlines, was performing a domestic flight from Margarita's General Santiago Mariño International Airport to Valencia's Arturo Michelena International Airport. The aircraft was carrying 134 passengers and 6 cabin crew members.
While cruising at 27,000 feet, the crew received a "cabin altitude" alert, indicating that the cabin pressure had risen above 10,000 feet and was continuing to climb. Upon recognizing the situation, the crew attempted to level the aircraft and perform memory items. They identified that the left-hand (LH) pack was without pressure. Following Quick Reference Handbook (QRH) procedures, the crew requested permission from Maiquetía Control to descend to 12,000 feet. During the descent, pneumatic pressure was restored to the left side, and cabin altitude returned to standard limits.
The flight continued normally, and the aircraft landed at Valencia without further incident. All occupants were unharmed, and the aircraft sustained no structural damage.
The investigation
The JIAAC investigation included interviews with the flight crew and a review of their licenses and medical certifications. Investigators examined the aircraft's maintenance records, including airworthiness certificates and recent service reports from the operator's maintenance organization.
Technical inspections involved visual examinations and troubleshooting according to the Aircraft Maintenance Manual (AMM). Specifically, investigators performed tests on the bleed air system and replaced "BAR #1" (the left bleed air regulator) in accordance with AMM procedures. Following the replacement, operational tests confirmed that the aircraft could maintain cabin pressure while operating on a single pack.