Dash 8-400
Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action
Aircraft; Company Policy
When I received the aircraft; the #1 Hydraulic System was at 30%. I contacted Maintenance Control and asked if I needed to enter that into the maintenance log; or if I was permitted to simply pushback; and then follow the supplemental procedure to transfer hydraulic fluid. Maintenance Control responded that I was allowed to simply depart; and accomplish the procedure to get the hydraulic quantity above 40% prior to taking off. Which is ultimately what we did: pushbacked; and then once the engines were running we balanced the hydraulic quantity. We were only able to get both sides to 50%; so the aircraft was lower on hydraulic fluid than is typical for the fleet; but is well within the limitations. Our next two legs were completely uneventful in the aircraft. Later in the day; I heard that aircraft had experienced a hydraulic failure; and I can't help but wonder if my failure to enter the imbalance into the maintenance log might have masked the impending failure.If something might indicate an impending failure; the QRH or supplemental procedure should include specific instruction to enter it into the maintenance log; so that Maintenance can track such issues.
The reporter stated that hydraulic fluid can flow from one system to another if a pilot does not monitor his taxi technique. When the systems do reach a predefined imbalance then a supplemental pilot procedure is approved to balance the systems. The reporter's concern has been and still is; that the maintenance log has no place to record the balance procedure in order to track the hydraulic systems' fluid use. In this event; the balancing procedure was used and at some point during the day; fluid was probably added; but no record of the balancing procedure existed which may have been used as a precursor to the system failure later that day.
A Q400 crew detected a hydraulic system quantity at 30% and transfered fluid to equalize both systems at 50% then learned later in that day the aircraft suffered a hydraulic system failure.