B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 52; Flight Crew Total 3700; Flight Crew Type 350
Workload; Time Pressure; Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL
General Maintenance Action
Human Factors; Aircraft; Procedure
Aircraft was flown with an improper MEL on an engine hydraulic pump. Because it was flown with a pump inoperative the pump overheated badly; there was significant hydraulic leakage including into the engine cowling and a pretty good risk of hydraulic fluid loss and loss of pressure in the system. Our crew arrived [for] a cargo flight to [a foreign destination]. When we arrived at the aircraft it had just returned from maintenance runs from changing a main engine fuel control. The logbook was not on board the aircraft. After verifying we could proceed; we loaded; preflighted and set up the aircraft for departure. [Eight] minutes before departure maintenance brought the logbook to the aircraft. We were informed that the right engine hydraulic pump did not work during the engine runs and had been deferred under MEL 29-11-01 (engine driven hydraulic pumps - depressurization function) This had not been entered into the MEL list at the front of the logbook yet. There were also a couple of MELS that had been cleared as a result of maintenance that needed to be closed out of the MEL list as well. Maintenance updated the logbook MEL list; I made a quick call to Dispatch to update the MEL's listed on our flight plan and took a quick look at the logbook and at the MEL before we blocked out. The flight proceeded normally with no problems or additional discrepancies. Hydraulic pressure and quantity were both normal for the flight. On arrival at [destination] post flight [inspection] revealed a large puddle of fluid under the right engine and in the right engine cowling. When the cowling was opened the right hydraulic pump was saturated with fluid and leaking. I wrote this up and our flight Mechanic proceeded to remove and replace the right hydraulic pump. An operational check after the pump was changed showed it still not to be putting out pressure. At this time I was informed we had operated under an MEL that did not apply and that we would have to fix the problem before we departed. A review of the MEL showed it applies to not being able to depressurize an engine hydraulic pump. There is no relief for an engine pump that does not put out pressure. Contributing factors; rushed and focused on other factors. The logbook was not presented until last minute and with a strong push to depart there was not a lot of time to review the log book or the MEL. Additionally I was focused on preparation for flight; calling Dispatch to update the flight release. Reliance on Maintenance; they had already deferred the hydraulic pump and I took for granted they had checked that this MEL applied to our situation. I reviewed the MEL but did not catch the specific conditions it applied to. Coordination between Maintenance and the flight crew; there were several clerical items that needed to be addressed in the logbook; Maintenance wanted to drop the book and run and they wanted me to get moving for an on time departure. How it was discovered; by Maintenance when we had a subsequent problem and they read the MEL more carefully. Corrective actions; not rushing; Maintenance [should be] taking the time to make sure the MEL applies to the specific problem. By my taking the time to thoroughly review and understand the log book and the MEL so I know it applies and what conditions I will be operating under; taking the time for a more thorough review with maintenance. Not allowing pressure to depart on time to have an impact. This should have been caught in at least three separate places; By Maintenance when the looked to see if the pump could be deferred; by maintenance control when they issued the deferral and after both of those failed; by me in a review of the deferral and MEL. I should have seen it did not apply. The pump was replaced and subsequently failed on the next flight. This time we did lose fluid; but not pressure but that is another story. Full corrective action is still underway but will be to replace the pump; filters and ensure proper operation of the system.
B767-300 Captain reported he was dispatched with an incorrect MEL that resulted in an overheating hydraulic pump and resultant fluid leak.