What happened
On March 15, 2019, a Boeing 737-800, registration SP-ENN, was operating a flight that had departed from Fuerteventura (GCFV) approximately 80 to 90 minutes prior. While operating within the Canarias FIR, the crew observed a "Master Caution" alert. Upon inspecting the overhead panel, the crew noted a momentary "Low Pressure" indication on the System A engine-driven hydraulic pump.
As the crew initiated the "HYDRAUL and Pump Low Pressure" procedures, they identified a progressive leak in System A, with fluid levels steadily decreasing. While System B initially remained stable at 96%, the pressure in System A dropped rapidly until the fluid level reached zero and a "Loss Pressure of SYS A" alert was triggered.
Due to the deteriorating situation, the crew decided to divert to Katowice-Pyrzowice (EPKT). During the descent, approximately 40NM from the destination, the crew declared an "URGENCY" (PAN PAN) status. Shortly after, the hydraulic fluid level in System B began to deplete rapidly, dropping from 96% to 60% within two to three minutes. To ensure a safe arrival, the crew manually extended the landing gear and set the flaps to 40°. The aircraft landed at EPKT without further incident.
The investigation
The PKBWL investigation focused on the mechanical cause of the fluid loss and the integrity of the hydraulic system components. The investigation examined the condition of the landing gear assembly and the installation of hydraulic pump components.
Findings
- A malfunction of the right-side shimmy damper caused the initial hydraulic fluid leak.
- The improper installation of the standby electric motor-driven pump (EMDP) case filter contributed to the system failure.
- The rapid depletion of System B was linked to the ongoing loss of hydraulic fluid following the initial failure.