Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 220; Flight Crew Total 30000; Flight Crew Type 2378
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Aircraft; Procedure; Human Factors
The airplane was dispatched under MEL (Minimum Equipment List); left Bleed Sensor Status displayed. I read the MEL and looked for any associated procedures. There were no unusual procedures; just that we may see a status message about the bleed sensor. There is however; a note at the bottom of this procedure stating in bold letters that the Associated Duct Pressure will be imperative. This should have been a clue that this was a bit more complex than it seemed. After engine start; we got an L Bleed Pressure EICAS (Engine Indicating and Crew Alerting System) message. Remembering the note I had read earlier; I assumed that was part of the MEL hence; normal in this situation.We departed with no issues on a beautiful 10 hour flight to ZZZZ. After a few hours in flight; we began a discussion about this MEL and the fact that we had departed with a bleed inoperative or a least not producing any air. Are there not some sort of altitude restrictions or takeoff weight restrictions etc with a bleed inoperative? More importantly; was that bleed supposed to be inoperative just because some sensor wasn't working properly? We wondered; can the bleed be reset now that we were in flight?We opened a discussion with [Maintenance Control] about all of this. They studied it and came back with a response. They felt that it was actually the HPSOV (High Pressure Shutoff Valve) that caused the bleed trip on engine start. This is associated with the EICAS Status message we had earlier; but slightly different. Had we returned to the gate after engine start; we would have probably been dispatched under a different MEL procedure; PRSOV (Pressure-Regulating and Shutoff Valves) inoperative. This MEL procedure is the one with all of the various takeoff weight penalties and altitude restrictions. [Maintenance Control] felt that the bleed trip could be safely reset in flight by simply turning the bleed switch off and then on.After a bit more discussion; we tried it. The bleed trip was reset and we had normal indications on both bleed systems for the remainder of the flight with the exception of the EICAS status message Bleed Sensor. My issue is that if we have a condition that can cause a bleed to be inoperative; shouldn't we follow all of the procedures associated with a bleed inop? In retrospect; I probably should have called [Maintenance Control] right after engine start and asked all of those questions.
After push and engine start we got a L bleed engine caution; we discussed this and associated it with the current MEL. We departed without any issue and climbed up to altitude without problem. In cruise there was a further discussion and [Maintenance Control] was involved. They advised that it was ok to reset in flight which we did. The flight continued without the caution returning; and we landed uneventfully. After further discussion with the crew after flight we should have called [Maintenance Control] after push back; since the actual problem was unclear. Was it a bleed valve or the sensor; what cautions and or status messages would we see?
B777 Captain and First Officer reported a problem with the aircraft; checked with Maintenance; departed but when airborne after more discussion decided they should have stayed on the ground to have the problem looked into more.