Boeing 737-3H4 Returns to Maiquetía After Hydraulic Low-Pressure Indication (YV645T)

Incident Overview and Aircraft Details On January 15, 2023, a Boeing 737-3H4 with registration YV645T and serial number 27932, operated by Rutas Aereas, C.A. (RUTACA), departed from Simón Bolívar International Airport (SVMI) in Maiquetía, Venezuela, bound for Manuel Carlos Piar International Airport in Puerto Ordaz. The aircraft carried 93 people: a pilot, a copilot, four cabin crew members, three other crew members, and 85 passengers. It took off at 19:52 UTC. The aircraft was a twin-engine, turbofan-powered, land-based transport category airplane with a tricycle retractable landing gear. Its two underwing engines were CFM International CFM-56-3C turbofans, each rated at a maximum thrust of 21,850 lbs. The maximum takeoff weight was 56,470 kg (124,495.04 lbs). The aircraft held valid registration, airworthiness, and radio station certificates issued by Venezuela’s INAC, and its insurance was in force at the time of the event. ## Event Sequence During the initial climb after takeoff, the flight crew observed a low-pressure (LOW PRESS) light for the mechanical pump of hydraulic system #1, located in engine #1. After completing the applicable quick reference handbook (QRH) actions, the captain notified air traffic services of the decision to return to Maiquetía (SVMI). The aircraft landed at 20:22 UTC. All occupants were unharmed, and the aircraft sustained no damage. ## Maintenance and Investigation Findings The maintenance organization responsible for the aircraft was OMAC N° 038B1 Taller Aeronáutico Mares, S.R.L., located at Simón Bolívar International Airport. The mechanical pump for hydraulic system #1 had been replaced the day before the incident. Investigators inspected engine #1 for leaks in the hydraulic pump area and found no evidence of leaks. Inspection of the landing gear bay revealed indications of a leak in the hydraulic system #1 oil reservoir at the connection of the Transmitter Press Hyd located on the aileron autopilot actuator. On January 17, the switch P/N S271T51 in hydraulic system #1 was replaced, and the hydraulic system #1 oil reservoir was refilled. Pressure and functional tests were performed. During the functional test, oil was found to be directed to the system drain, causing the hydraulic system #2 reservoir to show a low level. A test specified in AMM 29-15-00, pages 103 and 104, indicated a failure in two hydraulic shuttle valves, which were required to be replaced. The aircraft was moved to the hangar of OMAC N° 681 Estelar Technik, where hydraulic shuttle valves #1 and #4 were replaced. The hydraulic system #2 reservoir was refilled, and pressure, purge, and functional tests were completed without nonconformities. Full custody of the aircraft was then returned. ## Crew and Weather The pilot, aged 41, held a valid medical certificate, aeronautical license, and ratings issued by INAC, including Instrument Flight and B733 Captain/PIC. The copilot, aged 27, held a valid medical certificate, aeronautical license, and ratings issued by INAC, including Instrument Flight and B732/B733 Copilot/SIC. Weather conditions were reported as winds of 0 knots, unlimited visibility, and generally good weather throughout the day. ## Notifications In accordance with Chapter 4 of Annex 13 to the Convention on International Civil Aviation, the incident was reported using form MPPT-JIAA-F014 under case number 004/2023 and entered into the ICAO ADREP system. The United States of America, as the State of Design and State of Manufacture, was notified by email and responded by assigning an accredited representative.