Flight Crew Air Transport Pilot (ATP)
Time Pressure; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL
Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed
Aircraft; MEL; Procedure
Taxiing for takeoff; ECAM alerted us that #1 engine anti-ice nacelle valve had failed open.  Anti-ice off for takeoff.  Contacted ATC for taxi instructions to a remote location to work the problem. Received instructions to taxi across duty runway and hold short on the opposite side. Ran ECAM and consulted QRH which directed that a thrust limit penalty is reflected on TRP (Thrust Rating Panel). ATC cleared us to 'line up and wait'.  Replied to ATC that we were still working our problem and needed more time.  ATC reminded us of our slot time; directed us to hold short and advise them when ready.  Recomputed Takeoff data with 'engine anti-ice valve not closed' selected.  We re-briefed our takeoff performance; and told ATC that we were ready for takeoff. Received takeoff clearance; completed the takeoff checklist and made eventful takeoff.  While conducting in-range checklist; check of ECAM Recall reminded me our malfunction and made me realize that we had not consulted the MEL prior to departure.  I referenced the MEL 30-21-01-B Engine Anti Ice Nacelle Valves; which was a Flagged item MEL; requiring maintenance prior to takeoff.  Upon landing; wrote up discrepancy in AML and briefed maintenance personnel.While I do not believe we were rushing in the traditional sense; I think our knowledge of; and desire to takeoff at our assigned slot time; interfered with and broke our normal habit patterns associated with dealing with a relatively simple malfunction after block out.  I failed to recognize this break in my habit pattern; causing me to forget to reference the MEL on the ground prior to departure.I believe this type of event can be prevented if the crew will stop once more; and ask themselves if ALL required cockpit / crew actions have been completed prior to moving the aircraft.  We asked each other if we were 'ready to go'; but didn't really stop and think clearly about whether all required procedures relating the system malfunction had been completed.
The flight crew encountered an Anti-Ice system malfunction while taxiing for takeoff. After completing the appropriate checklists and re-computing the performance data; they accomplished an uneventful takeoff. However; due to pressure to meet an expiring takeoff slot time; they failed to address some MEL implications.