What happened
On July 6, 2015, a De Havilland Canada Dash 8 (400) was initiating its descent into Warsaw Chopin Airport (EPWA) when a "No 1 HYD HOT FLUID" message appeared on the Caution Warning Panel. The crew followed the appropriate checklists and monitored the hydraulic system. During this process, a drop in pressure was observed in hydraulic system number 1, even though the reservoir remained full.
Following the "HYD PUMP" checklist, the crew activated the standby pump. This action resulted in a rapid loss of hydraulic fluid from reservoir number 1, prompting the crew to immediately deactivate the standby pump. At that point, approximately 45% of the fluid remained in the reservoir. The crew determined that the remaining fluid was sufficient to operate the landing gear and extend the flaps to position 15.
During the final approach on the long runway, the crew extended the flaps to position 15, which caused further fluid loss and triggered a "LOSS OF FLUID FROM HYDRAULIC NO1 SYSTEM" alert. The crew performed the necessary checklist items and requested priority landing from Air Traffic Control, though they did not declare a formal emergency. The aircraft landed without further incident.
The investigation
Upon arrival at the parking stand, maintenance personnel identified a hydraulic fluid leak originating from the engine nacelle. The investigation focused on the failure of the hydraulic pump. Subsequent analysis of the pump by the manufacturer revealed that the unit had seized, leading to internal damage, overheating of components, and the loss of various internal parts.
Findings
- The primary cause of the incident was a failure of the main hydraulic pump in system number 1.
- The activation of the standby pump contributed to the rapid depletion of the hydraulic reservoir.
- The investigation noted that when a hydraulic leak occurs, the Fire Shut Off valve on the Fire Protection Panel can influence the initial warnings. If the valve is closed, the first alert triggered is for the "#1 ENG HYD PUMP," which may lead a crew to incorrectly conclude that the pump itself is the source of the issue, potentially leading to the activation of the standby pump and worsening the fluid loss.