What happened
On October 8, 2019, a Boeing 737-800, registration SP-ENQ, was operating within the controlled airspace (CTR) of Funchal Airport (LPMA) in Madeira. During the flight, specifically while the crew was retracting the flaps, a "Master Caution" alert was activated in the cockpit.
Upon inspecting the overhead panel, the crew identified a "Low pressure" warning. A subsequent check revealed a loss of hydraulic fluid within the aircraft's System B. In response to this failure, the crew performed the Non-Normal Checklist (NNC) for "Loss of System B." To manage the situation, the crew utilized the NITS (Nature, Intent and Intentions, Time, Special instructions) and TDODAR (Time, Diagnose, Options, Decide, Assign, Review) decision-making frameworks. Following their assessment, the crew decided to continue the flight to the destination, Katowice–Pyrzowice Airport (EPKT), where the aircraft landed safely without further incident.
The investigation
The investigation focused on identifying the source of the hydraulic fluid depletion. Investigators examined the hydraulic lines and components related to the System B architecture to determine why the pressure dropped during the flight.
Findings
The investigation established that the hydraulic leak was caused by the failure of a clamp securing a hydraulic line located upstream of the Electric Motor Driven Pump (EMDP). This failure allowed a hydraulic hose to shift, resulting in the hose rubbing against the housing of the EMDP electrical connector. This continuous friction caused the hose to wear through, leading to the fluid loss. The exact timing of when the clamp failed and the duration of the chafing period could not be definitively determined.
Safety action
Following the investigation, the following preventive measures were proposed:
- The technical department was to develop an information bulletin for organizations maintaining Enter Air Sp. z o. o. aircraft, focusing on inspecting the condition of flexible hydraulic lines and their associated clamps.
- The Deputy Chief Pilot was to issue a directive for pilots to exercise increased vigilance regarding the condition of hydraulic hoses and clamps during Pre-Departure Controls (PDC).