MD-11
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Human-Machine Interface; Communication Breakdown; Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Human Factors; Company Policy; Aircraft; Procedure
EDP [Engine Driven Pump] 2R was not producing pressure and was entered in the logbook on the previous night. Maintenance Control deferred the depressurization function instead of the pump because deferring the pump involved too much time to remove the pump. Their words; not mine. The number 2 hydraulic system failed the after start self test so the manual after start test was accomplished; and the test failed. The MEL does not mention the fact that the system will fail in the manual mode although it does say the system may fail the test in auto. Maintenance Control said the pump would fail because the MEL means the pump will produce no pressure. This is not stated in the MEL. When the hydraulic system was returned to auto; all indications were normal and all messages disappeared; placing the system back in its previous condition. But if the 2L pump failed; I believe there would be a 'HYD 2' failure. There is definitely confusion on the function of the 'depressurization function' either on my part or Maintenance Control's part. At the very least; the MEL is poorly written if what they were correct in what they were telling me about the pump not producing pressure. It should clearly state the pump will not produce any pressure at all; and the respective system will fail in the event of the opposite pump failing.
An MD-11 Captain addressed concerns about the wording of an MEL regarding dispatch with the 'depressurization function' of a hydraulic system deferred rather than the Engine Driven Pump which was responsible for the 'function' failure. The Captain implies that MEL was utilized because deferring the pump would have required too much time to accomplish.