A300
Flight Crew Air Transport Pilot (ATP)
Confusion; Training / Qualification
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem
Aircraft; Human Factors
During cruise flight; we got an ECAM warning of low Green #2 Pump pressure.  We turned off the pump according to ECAM procedures and checked the QRH.  As I was the pilot flying; the First Officer read through the checklist and we concurred that since pressure was not lost in the entire Green system that we would turn on the electric pumps on approach as a backup.  As it turned out; on final approach; we got another ECAM warning that Green #1 Pump had low pressure and we turned that pump off.  The system was still pressurized by the electric pumps and no other indications or warnings were received of loss of system pressure or quantity.  We continued to configure for landing and all systems operated normally through touchdown and taxi in.  Sometime later in the day after landing and more thoroughly looking at the QRH; it appears some of the procedures may be ambiguous; but since we never had an indication of complete loss of system pressure or quantity; it may have only served to complicate the issue more to drop the gear manually and request a tow-in after landing as the checklist might have led us to accomplish.
After level off at FL350; green system hydraulic pump #2 faulted. Followed ECAM and turned pump off. Reviewed 'HYD SYS LO PR (approach)' checklist but at that time green system was still powered by #1 green system engine driven hydraulic pump so only turning on electric pumps during the approach phase applied. On approach at 11;000; turned on green system electric hydraulic pumps in accordance with the QRH; but at the time the #1 green system pump was still operating normally. Turning visual final; #1 green system hydraulic pump faulted; secured in accordance with the ECAM; but green system pressure remained normal with electric pumps on and received no other ECAM guidance. I had moved past the 'system recovered' sub-bullet in the QRH before that since; at the time that we reviewed that part of the checklist; the #1 green system engine driven pump was still operating normally. I therefore missed 'If SYS RECOVERED By ELEC PUMP' sub-bullet on the procedure's first page that indicates if the green system is recovered by the electric pumps; the gear should be extended by the gravity extension procedure and BRK A/SKID selected to ALTN/ON. The subsequent 'If GREEN SYSTEM affected' review of ECAM procedures; which we never got on the ECAM; calls for an increase in landing speed of +5 KTS and for landing distance to be increased by 1.1; and for the L/G GRAVITY EXT procedure. I did note this in the QRH on page 2 of the procedure. However; reading down in the expanded notes starts; the section starts with 'If Green system remains unpressurized' and explains why the approach speed is increased and the landing distance is expanded. I interpreted this in error to indicate that the 'Green SYS affected' applied if it was unpressurized -- but in this case it was pressurized by the electric pumps. All configuration and gear extension accomplished normally. Had the second pump faulted earlier in the flight I probably would have caught the 'If SYS RECOVERED' sub-bullet of 'by ELEC PUMP' but when it actually occurred; I was on the next page where the 'If Green SYS affected' bullet appeared with the notes that discussed if the green system remained unpressurized. Additionally; we were in the process of preparing to configure. The expanded notes would be strengthened by stating that anytime the green system is powered by the electric pumps; the gear needs to be extended by the gravity method.After landing; I questioned what seemed to be an inconsistency in the procedure; and a conflict with what I believed to be the system status of the airplane; i.e. the green system functioning normally and pressurized via the electric pumps. My review of the procedure revealed my error in performing it; and backing up the Captain; who was the pilot flying.Cause:-- Sequence of the green system pump failures being almost an hour apart; with the second occurring as we were turning final with the electric pumps already selected on. Having already reviewed the checklist as it applied at the time; and having moved to the second page; I missed the note about 'if the system was restored by the electric pumps.' Additionally; what seemed to be a conflict between the notes and the procedure; use of the word 'affected' relative to the green system on page 2 of the procedure; which seemed to indicate along with the following note if unpressurized; vice something more definitive like 'unpressurized' and/or 'pressurized by electric pumps.'-- Training and Recurrent Training scenarios: I don't remember any ever addressing powering the green system solely by the electric pumps; it seemed all that I have had were either a loss of fluid or an overheat. Thus; my misunderstood system/procedural knowledge wasn't corrected.-- QRH HYD SYS LO PR checklist organization. Plus; the seemingly conflicting 'if Green system remains unpressurized' note's wording on the second page which implies that the procedure applies if the system isn't pressurized. In our scenario; we never lost pressure so weren't keyed to look at 'if recovered' steps.-- Not thoroughly reviewing the beginning page of the checklist once the second pump faulted since I thought we had already covered all the applicable items on that page; thereby missing the 'if SYS RECOVERED by ELEC PUMP' sub-bullet.-- Faulty system knowledge that led me to believe that with the electric pumps on and green system restored; that normal landing gear extension procedures and brake settings could be used since the green system was powered. Misinterpreting the notes section reinforced this belief.-- No note explaining why gravity extension is required even with green system powered by the electric pumps in a similar manner to why BRK ALT/ON is selected; five knots added to landing speed; and landing distance increased by 1.1 if the system is unpressurized (recommend adding to the notes 'or if pressurized solely by the electric pumps').Suggestions:-- Discontinue the approach and start the procedure over when the second engine driven Green system pump was lost. I was too much in the 'continue to land' mode since all green system components were operating normally; reinforcing my incorrect system knowledge/problem diagnosis.-- Better system knowledge/training about what the electric hydraulic pumps actually are meant to provide; and that if they are powering the green system; gravity gear extension and alternate brakes MUST be used.-- A better organized and written QRH checklist/notes for green system hydraulic system low pressure.-- Once again relearning the old aviation lesson about taking that extra time to ensure you have it right.
A300 flight crew reported green hydraulic system anomalies and stated the QRH procedure is complex and confusing.