Incident Overview
On 10 March 2016, a Boeing 737-800 was en route at cruise level when approximately one hour after departure, the LOW PRESSURE warning for hydraulic system A illuminated. The flight crew followed the HYDRAULIC PUMP LOW PRESSURE checklist, deactivating the mechanical pump for that system. After several minutes, the warning reactivated. Inspection revealed a complete loss of hydraulic fluid and zero pressure in system A.
Crew Actions
The crew then executed the LOSS OF SYSTEM A checklist and continued toward the intended destination. After entering the EPWW flight information region, they consulted with the operator's operations department and decided to divert to EPWA (Warsaw Chopin Airport). In accordance with the checklist, the crew extended the landing gear using the alternate extension system prior to landing. They requested landing priority from air traffic control without declaring an emergency. The landing was completed without incident.
Maintenance Findings
Maintenance personnel identified that the hydraulic fluid leak originated from the valve of the transducer adapter module in hydraulic system A. The transducer adapter module and the system A hydraulic pump were replaced. After replenishing hydraulic fluid and conducting system leak tests, the aircraft was returned to unrestricted service.
Cause
The incident was caused by a seal failure in the transducer adapter module of hydraulic system A. The investigating commission did not issue any safety recommendations.