Avior Airlines Flight Returns to Maiquetía After Bleed Air System Fault (YV3158)

Incident Overview and Flight Details On June 28, 2021, at 16:10 UTC, a Boeing 737-401 with registration YV3158, serial number 23984, and owned by Avior Airlines, C.A., departed from Simón Bolívar International Airport (SVMI) in Maiquetía, Venezuela, bound for Presidente Juscelino Kubitschek International Airport (SBBR) in Brasília, Brazil. The aircraft carried 10 people: a pilot, a copilot, four cabin crew members, and four extra crew. The planned flight time was 4 hours and 45 minutes, with 35,400 pounds of fuel and an endurance of 6.37 hours. ## In-Flight Event and Return During the initial climb, as the aircraft crossed approximately 15,000 feet, the right-side Bleed Trip Off light illuminated. The flight crew applied the Quick Reference Handbook (QRH) procedure, which instructed them to press the Engine Bleed button to close the valve. The action did not produce a satisfactory result. Because the altitude limitation compromised the flight plan, the crew contacted the Area Control Center (ACC-SVMI) and returned to Maiquetía due to a fault in the aircraft's pneumatic system. The aircraft landed without incident, and all persons on board were unharmed. ## Aircraft and Maintenance Background The aircraft was a commercial transport category Boeing 737-401 with FAA Type Certificate A6WE. It was airworthy under Certificate of Airworthiness No. 013223, had a passenger capacity of 144, and was powered by two CFM International CFM56-3B-2 turbofan engines. The last preventive and scheduled maintenance was performed by OMAC-N 440: Avior Airlines, C.A., located at José Antonio Anzoátegui International Airport in Barcelona, Venezuela. ## Investigation and Findings The investigation included crew interviews, collection of crew and operator documentation, and review of maintenance records. During a maintenance inspection to validate corrective actions, technicians performed troubleshooting in accordance with Aircraft Maintenance Manual (A.M.M) 36-11-05/101 and SSM 36-10-01/104. They examined the sensor lines for the high-stage valve and regulator valve for pneumatic leaks. A loose fitting on the right-hand Bleed Regulator Valve sensor line was found. The fitting was adjusted per A.M.M 20-50-11, and a Bleed Air Control Systems operational test was completed satisfactorily. Engine run-up verification also produced satisfactory results. ## Conclusion The investigation determined that the right-hand Bleed Regulator Valve sensor line fitting was loose due to an inadequate check, which caused the Bleed Trip Off light to illuminate in the cockpit. The fitting was realigned and the corresponding tests were performed according to the aircraft maintenance manual, restoring correct system operation. The investigation was closed based on these findings.