B757-200
Flight Crew Air Transport Pilot (ATP)
Confusion; Human-Machine Interface; Troubleshooting
Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; General Declared Emergency
Aircraft; Procedure; Manuals
We were dispatched with the right air conditioning pack inoperative under normal MEL procedures. Due to weather along the SCOTT Arrival; we were being vectored south along the west coast of southern Florida and had been given a clearance to descend to 8;000 and to proceed direct to CARNU to join the CURSO 2 RNAV Arrival. Passing through approximately 13;000 feet at 280 knots with the throttles at idle I looked up to see that the left air conditioning pack had failed - 'INOP' and 'PACK OFF' lights in the pack switch were both illuminated. There were no EICAS messages displayed to correspond with the pack shutdown indications; but the cabin altitude was climbing rapidly and it was clear that the pack was indeed off. I immediately declared an emergency with Miami Center and increased the rate of descent in order to get below 10;000 before the cabin altitude rose to meet the aircraft altitude. In doing so; I exceeded 250 knots below 10;000 for a few minutes; slowing once we leveled off at our cleared altitude of 8;000.We had difficulty locating the proper QRH checklist - the PACK OFF checklist gave guidance only on the need to descend below 10;000 but gave no guidance whatsoever to attempt pack restoration. That guidance was eventually found in the PACK TEMPERATURE checklist - even though there is no caution light labeled 'Pack temperature' (only an INOP light) and we had no EICAS message indicating 'Pack temperature.' Following this checklist; we reinstated the left pack to STBY-N after about 5 minutes of unpressurized flight. The cabin altitude never exceeded approximately 6;000 as we were cleared to descend to 3;000 shortly after our level-off at 8;000 and we hurried down to minimize cabin altitude. The pack operated in STBY mode without tripping again and we landed without further incident.It would be helpful if the QRH index could be changed to 'PACK OFF - PACK TEMP' to allow a search for the actual indication. Also; the PACK OFF checklist should refer to the Pack Temp checklist to assist in attempting to restore the pack; if appropriate.
Dispatched with the right AC pack inoperative the flight crew of a B757-200 was alerted to the failure of the left pack while in the descent for landing.  They expedited their descent with ATC's assistance and regained sufficient control to complete their arrival.  Difficulties in determining and accessing the correct checklists for the condition led the reporter to advocate for checklist titles more representative of the abnormality in question.