A B757-200 was dispatched with a single pack and enroute at FL350 the remaining pack malfunctioned s...

Attributes
ACN	941869
Time
Date	201104
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Component
Aircraft Component	Air Conditioning and Pressurization Pack
Person 1
Function	Pilot Not Flying Relief Pilot
Person 2
Function	First Officer Pilot Not Flying
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

[Our flight was a] single pack operation due to deferral. I was on the first crew rest break when speed brakes extended and I was summoned to the cockpit. When I arrived [there was a] cabin altitude warning on EICAS [and the] aircraft descending through 29;000. Donned mask and established communication. Cabin was brought down below 10;000 when the aircraft was in the mid 20's. I assisted crew with checklists and radio calls to company. [We made an] overweight landing at a diversion airport without incident. Maintenance found operating pack had a problem and we were dispatched another aircraft.

Original NASA ASRS Text

Title: A B757-200 was dispatched with a single pack and enroute at FL350 the remaining pack malfunctioned so the crew declared an emergency; descended to 10;000 FT and diverted to an enroute airport.

Narrative: [Our flight was a] single pack operation due to deferral. I was on the first crew rest break when speed brakes extended and I was summoned to the cockpit. When I arrived [there was a] Cabin Altitude Warning on EICAS [and the] aircraft descending through 29;000. Donned mask and established communication. Cabin was brought down below 10;000 when the aircraft was in the mid 20's. I assisted crew with checklists and radio calls to company. [We made an] overweight landing at a diversion airport without incident. Maintenance found operating pack had a problem and we were dispatched another aircraft.

Data retrieved from NASA's ASRS site as of April 2012 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.

A B757-200 was dispatched with a single pack and enroute at FL350 the remaining pack malfunctioned so the crew declared an emergency; descended to 10;000 ft and diverted to an enroute airport.