What happened
On August 21, 2016, a Bombardier DHC-8-400 operated by PLL LOT SA was performing its approach to landing within the Warsaw (EPWA) control zone. During the execution of the approach checklist, the crew identified a total loss of hydraulic fluid from the No. 2 hydraulic system, accompanied by a PTU control failure amber light indication. While no other warnings appeared on the upper panel, the crew noted an informational light indicating the Engine 2 hydraulic valve had closed.
In response to the failure, the crew followed the Quick Reference Handbook (QRH) procedures for a No. 2 hydraulic system failure and loss of all fluid, as well as the procedures for alternate landing gear extension. Due to the complete loss of pressure within the hydraulic installation, the crew performed an emergency gear extension. The aircraft landed safely and taxied to the parking stand, after which an Air Safety Report (ASR) was filed and the aircraft was handed over to maintenance personnel.
The investigation
Technical services inspected the aircraft and discovered that the Engine 2 nacelle was contaminated with hydraulic fluid. The investigation established that a component of the hydraulic system hardware on the Engine Driven Pump (EDP) No. 2 pressure line had failed, leading to a leak and the subsequent loss of system fluid. Because the EDP No. 2 had operated without fluid for a period of time, maintenance crews decided to replace the pump. The repair process included flushing and bleeding the hydraulic system, as well as replacing the EDP and PTU line filters. A successful test of the primary landing gear extension and retraction system was subsequently performed.
Findings
- The primary cause of the incident was a loss of hydraulic system integrity caused by a failed hardware component on the pressure line of the No. 2 Engine Driven Pump.