Narrative:

On taxi for departure, the captain and I recognized low pneumatic pressure on the left side (approximately 5 psi) which caused the left pack off light and appropriate EICAS message. Maintenance was contacted and a return to the gate to secure the left engine high stage bleed valve commenced. The mechanic greeting the plane suggested another way of turning off the engine bleed air. This was by turning off the engine bleed switch on the pneumatic panel in the cockpit. Maintenance dispatch, and the flight crew all conferred to operate the flight under the limitations caused by the deferred item. (Authority/authorized by MEL). We requested a new dispatch release to account for the increased fuel burn at FL250 and to reflect the inoperative bleed and pack. A release was sent which included the fuel burn at FL250, but there is apparently no MEL restrs for flts planned below FL350. So, the MEL notes were omitted from our flight plan. Dispatch relayed that the original flight plan at FL330 would still be acceptable. The heat generated by the aircraft system, electronics, and our passenger had raised the temperature of the cabin to about 94 degrees. I checked the flight manual to find an irregular procedure to follow for dispatch with either an engine bleed inoperative or pack inoperative. Both of these procedures are listed to solve en route system failures, not planning to operate the aircraft cooling and pressurization system inoperative. The checklists refer to keeping the isolation valve closed (to separate left and right pneumatics) unless necessary to provide anti-ice protection. They also state that cabin pressurization should be able to be maintained up to an altitude of FL350. Our flight departed with the hopes that at altitude the cabin temperature would cool. All went well during the initial climb. At FL280 we began to be concerned that the temperature was still 92 degrees. Both the captain and I thought to start the APU to provide additional cooling from the left pack. When we did this, the duct pressure never changed. We continued the climb to FL330. Upon level off, we noticed the cabin pressure rising at about 1000 FPM. We continued to observe this and the rate decreased to 800 FPM as the cabin pressure altitude neared 9000 ft. I asked the captain to get a descent clearance in case the pressurization did not stop climbing. The clearance was received and a descent was initiated. In the descent, (speed brakes extended, throttles at thrust to give pneumatic pressure) the cabin altitude warning horn sounded as the cabin exceeded 10000 ft. In the descent, the cabin corrected to the proper altitude, and the remainder of the flight was completed at FL240. I feel the following problems led to the events mentioned: 1) lack of pneumatic APU limits listed in the flight manual. 2) lack of appropriate irregular procedures for dispatch with bleed or pack inoperative condition. 3) slight misleading wording of the airplane manual pneumatic description. 4) our crew's delay to take appropriate action to prevent the rise in cabin altitude. 5) our mistakes in operation of the second pneumatic pack. This reduced flow from the operating pack. Our APU will only supply pneumatics to an altitude of about FL230, thus the lack of air to the second pack that we turned on in flight.

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Original NASA ASRS Text

Title: AN ACR B757 CREW, ALONG WITH HELP FROM ITS MAINT AND DISPATCH DEPTS, ATTEMPTED TO USE THE APU FOR BLEED AIR ABOVE ITS LIMITS WHILE OPERATING WITH ONE HIGH STAGE BLEED INOP. ERROR ADMITTED.

Narrative: ON TAXI FOR DEP, THE CAPT AND I RECOGNIZED LOW PNEUMATIC PRESSURE ON THE L SIDE (APPROX 5 PSI) WHICH CAUSED THE L PACK OFF LIGHT AND APPROPRIATE EICAS MESSAGE. MAINT WAS CONTACTED AND A RETURN TO THE GATE TO SECURE THE L ENG HIGH STAGE BLEED VALVE COMMENCED. THE MECH GREETING THE PLANE SUGGESTED ANOTHER WAY OF TURNING OFF THE ENG BLEED AIR. THIS WAS BY TURNING OFF THE ENG BLEED SWITCH ON THE PNEUMATIC PANEL IN THE COCKPIT. MAINT DISPATCH, AND THE FLC ALL CONFERRED TO OPERATE THE FLT UNDER THE LIMITATIONS CAUSED BY THE DEFERRED ITEM. (AUTH BY MEL). WE REQUESTED A NEW DISPATCH RELEASE TO ACCOUNT FOR THE INCREASED FUEL BURN AT FL250 AND TO REFLECT THE INOP BLEED AND PACK. A RELEASE WAS SENT WHICH INCLUDED THE FUEL BURN AT FL250, BUT THERE IS APPARENTLY NO MEL RESTRS FOR FLTS PLANNED BELOW FL350. SO, THE MEL NOTES WERE OMITTED FROM OUR FLT PLAN. DISPATCH RELAYED THAT THE ORIGINAL FLT PLAN AT FL330 WOULD STILL BE ACCEPTABLE. THE HEAT GENERATED BY THE ACFT SYS, ELECTRONICS, AND OUR PAX HAD RAISED THE TEMP OF THE CABIN TO ABOUT 94 DEGS. I CHKED THE FLT MANUAL TO FIND AN IRREGULAR PROC TO FOLLOW FOR DISPATCH WITH EITHER AN ENG BLEED INOP OR PACK INOP. BOTH OF THESE PROCS ARE LISTED TO SOLVE ENRTE SYS FAILURES, NOT PLANNING TO OPERATE THE ACFT COOLING AND PRESSURIZATION SYS INOP. THE CHKLISTS REFER TO KEEPING THE ISOLATION VALVE CLOSED (TO SEPARATE L AND R PNEUMATICS) UNLESS NECESSARY TO PROVIDE ANTI-ICE PROTECTION. THEY ALSO STATE THAT CABIN PRESSURIZATION SHOULD BE ABLE TO BE MAINTAINED UP TO AN ALT OF FL350. OUR FLT DEPARTED WITH THE HOPES THAT AT ALT THE CABIN TEMP WOULD COOL. ALL WENT WELL DURING THE INITIAL CLB. AT FL280 WE BEGAN TO BE CONCERNED THAT THE TEMP WAS STILL 92 DEGS. BOTH THE CAPT AND I THOUGHT TO START THE APU TO PROVIDE ADDITIONAL COOLING FROM THE L PACK. WHEN WE DID THIS, THE DUCT PRESSURE NEVER CHANGED. WE CONTINUED THE CLB TO FL330. UPON LEVEL OFF, WE NOTICED THE CABIN PRESSURE RISING AT ABOUT 1000 FPM. WE CONTINUED TO OBSERVE THIS AND THE RATE DECREASED TO 800 FPM AS THE CABIN PRESSURE ALT NEARED 9000 FT. I ASKED THE CAPT TO GET A DSCNT CLRNC IN CASE THE PRESSURIZATION DID NOT STOP CLBING. THE CLRNC WAS RECEIVED AND A DSCNT WAS INITIATED. IN THE DSCNT, (SPD BRAKES EXTENDED, THROTTLES AT THRUST TO GIVE PNEUMATIC PRESSURE) THE CABIN ALT WARNING HORN SOUNDED AS THE CABIN EXCEEDED 10000 FT. IN THE DSCNT, THE CABIN CORRECTED TO THE PROPER ALT, AND THE REMAINDER OF THE FLT WAS COMPLETED AT FL240. I FEEL THE FOLLOWING PROBS LED TO THE EVENTS MENTIONED: 1) LACK OF PNEUMATIC APU LIMITS LISTED IN THE FLT MANUAL. 2) LACK OF APPROPRIATE IRREGULAR PROCS FOR DISPATCH WITH BLEED OR PACK INOP CONDITION. 3) SLIGHT MISLEADING WORDING OF THE AIRPLANE MANUAL PNEUMATIC DESCRIPTION. 4) OUR CREW'S DELAY TO TAKE APPROPRIATE ACTION TO PREVENT THE RISE IN CABIN ALT. 5) OUR MISTAKES IN OP OF THE SECOND PNEUMATIC PACK. THIS REDUCED FLOW FROM THE OPERATING PACK. OUR APU WILL ONLY SUPPLY PNEUMATICS TO AN ALT OF ABOUT FL230, THUS THE LACK OF AIR TO THE SECOND PACK THAT WE TURNED ON IN FLT.

Data retrieved from NASA's ASRS site as of July 2007 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.