A319
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 90; Flight Crew Total 15000; Flight Crew Type 9000
Confusion; Situational Awareness; Workload; Troubleshooting; Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Gate; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Procedure; MEL; Human Factors
Due to multiple ECAM (Electronic Centralized Aircraft Monitoring) notifications prior to takeoff and a return to the gate; the maintenance release in question had two deferrals and associated MEL flight crew procedures that seem incompatible with each other. On this Flight Pack 2 was deferred inop due to a faulty flow control valve and the No.1 engine HP (High Pressure) valve deactivated. Despite independent and numerous cross checks of the pilot procedures to make sure they didn't conflict with each other; another flight crew pointed out an important pressurization issue having these two items deferred at the same time. The pilot procedures for [the MEL] (deactivated HP valve in closed position) state that during flight at low power settings; the associated engine bleed switch should be selected off and the operative bleed pre-cooler outlet temp monitored. If the temp exceeds 240 degrees; the pack associated with the inoperative bleed system should be selected off. If this occurred; the only operative pack would be shut down and a pressurization problem would ensue. Consequently; these two MELs are not compatible with each other.
An A319 with conflicting MEL's was issued a Maintenance Release and taxied for takeoff. The crew realized a #1 Pack Flow Control Valve MEL'ed inoperative and a failed #2 Engine High Pressure Bleed Valve could not simultaneously be inoperative. The flight returned to the gate.