Incident Overview
On 6 July 2015, a De Havilland Canada Dash 8 (400) was operating at EPWA (Warsaw Chopin Airport). During the initial descent, the caution warning panel displayed a "No 1 HYD HOT FLUID" message. The flight crew followed the appropriate checklist and monitored the hydraulic system.
Crew Actions
After some time, the crew observed a pressure drop in hydraulic system No. 1 despite the fluid reservoir being full. They then performed the procedures in the "HYD PUMP" checklist. Activating the standby pump caused a rapid loss of hydraulic fluid from reservoir No. 1, prompting the crew to deactivate the standby pump. At that point, approximately 45% of hydraulic fluid remained in the reservoir. The crew assessed that the remaining fluid was sufficient to extend the landing gear and flaps to the 15-degree position.
On the long final approach, the flaps were extended to 15 degrees, resulting in further fluid loss and a "LOSS OF FLUID FROM HYDRAULIC NO1 SYSTEM" warning. The crew again followed the relevant checklist and requested a priority landing from air traffic control without declaring an emergency. The landing was completed without further incident.
Post-Flight Findings
After taxiing to the parking stand, maintenance personnel discovered a hydraulic fluid leak from the engine nacelle, caused by a faulty hydraulic pump. The pump was sent to the manufacturer for repair. The repair report indicated that the pump had seized, leading to internal damage, overheating of components, and missing parts.
Cause and Preventive Measures
The investigation determined the cause of the incident to be a fault in the main pump of hydraulic system No. 1. The crew's actions following the malfunction were considered correct. As a preventive measure, it was noted that pilots should pay attention to the Fire Shut Off valve on the Fire Protection Panel during hydraulic system failures, as a closed valve—especially after a fluid leak—could cause the first activated warning to be "#1 ENG HYD PUMP," which might be misinterpreted as a pump fault and lead to unnecessary activation of the standby pump, worsening the situation. No safety recommendations were issued.