Date: 201307
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: B757 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Landed As Precaution; Flight Crew Diverted; General Declared Emergency
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The flight was dispatched with the left pack inoperative. The temperature had been difficult to regulate throughout all three cabins; but that is not altogether uncommon when operating on a single pack for air conditioning. Due to these complications with the temperature; close attention was being paid to the air conditioning panel on the overhead. Eventually we noticed a couple of rapid spikes in the cabin altitude; followed shortly thereafter by a sudden complete failure of the right pack. The aircraft cabin began to depressurize at what I would consider a moderate rate. We were at cruise; FL350 (max single pack altitude). The Captain and I both immediately donned our oxygen masks. I switched the microphone selector to MASK; ensured the speaker volume was turned up all the way and depressed the FLIGHT INTERPHONE selector with the associated volume slide lever nearly full up; but could not establish communications with the Captain. It appeared as though the oxygen mask microphone was not operating properly (though it did test for flow on the ground prior to departure). I could not hear the Captain through his oxygen mask via the interphone either. I had been the pilot flying for the leg; but did not want to embark on a course of action regarding aircraft manipulation until I could be sure the Captain and I were on the same page and would be procedurally synchronized to meet a common goal. Obviously our inability to communicate was a roadblock to this aspiration. After a few awkward moments; we both realized communications were hamstrung and the Captain assumed control of the aircraft and declared an emergency with ATC; also requesting an immediate descent. Shortly thereafter the Captain confirmed a loss of pressurization with ATC as the reason for the descent. At this time; being able to hear the Captain communicate with ATC it became clear to me that we were both thinking the same thing procedurally. Since the Captain had assumed control of the aircraft and was communicating with ATC already (the traditional role of the pilot flying in emergency scenarios) I then immediately assumed the role of the pilot not flying and retrieved the QRH for CABIN ALTITUDE or RAPID DEPRESSURIZATION or EMERGENCY DESCENT checklist. ATC did not give us an immediate descent to 10;000 feet. There were; I believe; two relatively brief restrictions on the way down - one at 27;000 feet and another at 23;000 feet. This combined with our delay in starting the appropriate checklist due to the communications roadblock had caused us to fall behind in our quest to reach 10;000 feet before the cabin altitude became excessive At this moment; I thought it prudent to activate the PASS OXY switch in advance of reaching that juncture in the checklist. We were somewhere near the mid 20;000s in altitude; and the cabin altitude was already somewhere between 11;000 feet and 12;000 feet; climbing at the same moderate clip. It was clearly evident to me at that moment that the cabin altitude would exceed 14;000 feet; so I thought it prudent for the continued safety of our passengers and crew to activate the switch in advance. I pointed to the switch while gaining the Captain's attention and when he nodded his concurrence; I activated the switch and then proceeded with the remainder of the checklist. I held the checklist over the center pedestal and up near the front of the forward panel in hopes that the captain could see the checklist as I accomplished the items within. The checklist was completed by me reading (shouting) each single item with the mask pulled away from my face momentarily; the re-securing the mask to take a breath prior to accomplishing the next item in succession in the same manner until the checklist was complete. We did; in fact; get the CABIN ALTITUDE aural warning and EICAS warning. I recall it to be somewhere in the range of 20;000 feet to 18;000 feet in our descent. I do not think the cabin altitude exceeded 15;000 feet throughout the entire event. Dispatch had been notified via ACARS of our predicament and our intention to divert after the checklist was completed and prior to reaching 10;000 feet. I think we caught them at a shift change as their response time was a bit slower than I would have anticipated under the circumstances. Upon reaching 10;000 feet we removed our masks. I made a PA to the flight attendants that it was safe to remove their masks and answer the interphone. They were then advised of our situation and time to landing. At this time; while completing a review of the EICAS messages it was noted that the RIGHT PACK OVERTEMP EICAS was illuminated. It appeared to be a pack trip. The Captain agreed and it was reset successfully and operated normally throughout the remainder of the flight. I checked for landing performance numbers via ACARS; but it would default to the planned landing weight; not our actual weight; so I had to ask dispatch to send those numbers for us; which they did. The performance numbers were good. I found this process to be a bit cumbersome; perhaps it could be refined in the future. The Captain made a PA to the passengers at 10;000 feet. We accomplished the approach/descent and landing checklists in order as the Captain continued to fly the aircraft to a normal landing without further incident. The landing was not over weight and the weather was VFR.




Synopsis: B757 First Officer experiences the loss of the remaining pack at FL350; after being dispatched with the other inoperative. The intercom system cannot be made to function during the descent and hand signals are used along with shouting with the oxygen mask momentarily lifted.