Narrative:

Our boeing 777 return aircraft was dispatched with the right prsov (pressure-regulating shutoff valve) closed and locked. The entire right side bleed source was inoperative. This left us with the left engine bleed and the APU as the backup pneumatic source for pressurization. The MEL was over 2 pages long with multiple crew actions at different phases of flight. We weighed all the risks we could think of; called the [operations manager] and [maintenance control] and decided that we had enough redundancy and a plan to cross the open water to [destination]. Our thoughts were:1. One operating engine bleed2. 2 packs operating3. APU bleed for backup4. Fuel for APU operation for entire flight5. If the APU quit; we turn around.we fueled the aircraft for a loss of the other bleed and ran the APU the entire way. If the APU quit; we would turn back. After takeoff and level off at FL350; we both realized the seriousness of the situation. We are at FL350 and the APU will not start to pressurize until 22;000 ft. [Maintenance control] couldn't answer question as to the procedure for losing the other bleed source. Our flight manual does not have any non-normal for bleed loss. When and how does the APU bleed open to give us air? How long does it take to descend from FL350 to FL220; which is APU operating range? The APU bleed has to open during landing to power the adp's (air-driven pump) to raise the gear during a G/a (go around). When and how does this happen? The MEL says to close both bleeds in the event of system failure. That's all we had to go on for landing. If the APU bleed fails to open; do we divert? We had more questions than answers. We both realized that we should have never taken the aircraft especially over open water. Even though this is MEL and ETOPS legal it wasn't the right thing to do. To summarize the concerns:1. No non-normal for losing both bleeds.2. How long does the cabin hold pressure with no bleed air?3. Can we descend in time before the cabin runs out of air?4. What happens if the APU bleed fails to open or the isolation valves fail to isolate the center for gear retraction on a G/a?5. What keys the APU to open the bleed on landing? The MEL says APU required to be used as air source for center system. How do we do this?there needs to be a rewrite for the loss of both bleeds and how to fly with one bleed inoperative. The questions that the MEL brought up and lack of information in the flight manual should be fixed so we have a better understanding as to the risk environment that crews will put themselves in with this type of deferral.

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Original NASA ASRS Text

Title: Boeing 777 Captain reported that when assigned an aircraft with one engine bleed inoperative; the Flight Crew questioned the lack of Flight Manual information regarding use of the Auxiliary Power Unit bleed system and single bleed operation.

Narrative: Our Boeing 777 return aircraft was dispatched with the right PRSOV (Pressure-Regulating Shutoff Valve) closed and locked. The entire right side bleed source was inoperative. This left us with the left engine bleed and the APU as the backup pneumatic source for pressurization. The MEL was over 2 pages long with multiple crew actions at different phases of flight. We weighed all the risks we could think of; called the [Operations Manager] and [Maintenance Control] and decided that we had enough redundancy and a plan to cross the open water to [destination]. Our thoughts were:1. One operating engine bleed2. 2 packs operating3. APU bleed for backup4. Fuel for APU operation for entire flight5. If the APU quit; we turn around.We fueled the aircraft for a loss of the other bleed and ran the APU the entire way. If the APU quit; we would turn back. After takeoff and level off at FL350; we both realized the seriousness of the situation. We are at FL350 and the APU will not start to pressurize until 22;000 ft. [Maintenance Control] couldn't answer question as to the procedure for losing the other bleed source. Our Flight Manual does not have any non-normal for bleed loss. When and how does the APU bleed open to give us air? How long does it take to descend from FL350 to FL220; which is APU operating range? The APU bleed has to open during landing to power the ADP's (Air-Driven Pump) to raise the gear during a G/A (Go Around). When and how does this happen? The MEL says to close both bleeds in the event of system failure. That's all we had to go on for landing. If the APU bleed fails to open; do we divert? We had more questions than answers. We both realized that we should have never taken the aircraft especially over open water. Even though this is MEL and ETOPS legal it wasn't the right thing to do. To summarize the concerns:1. No non-normal for losing both bleeds.2. How long does the cabin hold pressure with no bleed air?3. Can we descend in time before the cabin runs out of air?4. What happens if the APU bleed fails to open or the isolation valves fail to isolate the center for gear retraction on a G/A?5. What keys the APU to open the bleed on landing? The MEL says APU required to be used as air source for center system. How do we do this?There needs to be a rewrite for the loss of both bleeds and how to fly with one bleed inoperative. The questions that the MEL brought up and lack of information in the Flight Manual should be fixed so we have a better understanding as to the risk environment that crews will put themselves in with this type of deferral.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.