What happened
On January 15, 2023, a Boeing 737-3H4, registration YV645T, operated by RUTAS AEREAS, C.A. (RUTACA), departed from Maiquetía International Airport (SVMI) bound for Puerto Ordaz. The aircraft was carrying 93 occupants, including the flight crew and 85 passengers.
During the initial climb following a 19:52 UTC departure, the flight crew observed a low pressure (LOW PRESS) light indicating an issue with the mechanical pump of hydraulic system #1 located on engine #1. The crew immediately performed the Quick Reference Handbook (QRH) procedures and notified Air Traffic Services of their decision to return to Maiquetía. The aircraft landed safely at 20:22 UTC; there were no injuries and no damage to the aircraft.
The investigation
The JIAAC investigation involved inspections of the hydraulic system and maintenance records. Investigators examined engine #1 and found no external leaks at the hydraulic pump, which had been replaced the previous day. However, an inspection of the landing gear well revealed a leak in the hydraulic fluid reservoir of system #1 at the connection of the hydraulic pressure transmitter located above the autopilot aileron actuator.
Following the discovery, maintenance personnel replaced the pressure switch (P/N S271T51) and replenished the hydraulic fluid. During subsequent functional testing, it was discovered that hydraulic fluid was being diverted to the system drain, causing a drop in the reservoir level for hydraulic system #2. Further testing identified failures in two hydraulic shuttle valves. Consequently, the aircraft was moved to a hangar where hydraulic shuttle valves #1 and #4 were replaced, and the system was successfully repressurized and tested.