A B757 crew reported excessive noise in flight making communications with ATC and between themselves difficult. The left recirculation was turned off to reduce noise but the cabin altitude climbed above 10;000 FT on a single pack. An emergency was declared and the crew descended.
Synopsis
A B757 crew reported excessive noise in flight making communications with ATC and between themselves difficult. The left recirculation was turned off to reduce noise but the cabin altitude climbed above 10;000 FT on a single pack. An emergency was declared and the crew descended.
Narrative
The aircraft had been written up on previous flight with excessive cockpit noise. While climbing out it was very difficult to communicate to other pilot. Decided to stay at FL270 and turn off left pack for noise considerations. After about 5 minutes at cruise got cabin warning horn and master cautions. Cabin indicated above 10;000 FT. Followed QRH procedures; declared emergency to get lower altitude. Was able to get cabin below 10;000 FT at lower altitude. With concurrence from Dispatch continued to our destination. O2 masks did not deploy and no passenger problems. Aircraft has history of very loud cockpit noise with both packs and recirculation fans on. Very difficult to communicate without having to talk very loud. Although maintenance says 80-100 decibels is acceptable some planes have been continuously written up for high noise levels. A review across the board should be done of all 757s to ensure any modifications have been done correctly and all duct work is clean and working properly.
Second reporter narrative
This arrived with an open maintenance logbook entry for excessive cockpit noise written up by the inbound crew. Our flight was delayed due to Maintenance trying to get a waiver to release the flight with this logbook entry. Release was finally granted. Logbook item closed and the flight was released. During taxi and climb; the cockpit noise level with both packs operating was very high. The noise level made ATC instructions and checklist usage difficult. The Captain elected not to climb to the filed cruise FL330; and requested FL270 as a precaution to possible further action regarding the cockpit noise level. As the noise level made it difficult to hear both ATC instructions; and each other; the Captain elected to turn off the left pack to lower the decibel level in order to safely hear ATC and cockpit dialog. The cabin altitude indicated that it was holding and one pack would be sufficient to continue at FL270. After 5- 10 minutes the CABIN WARNING illuminated and sounded. We initiated an emergency descent; declared an emergency; and complied with the appropriate checklist procedures. The Dispatcher; Flight Attendants and passengers were notified as time permitted. CRM procedures were always utilized. Cabin O2 masks did not deploy. No passenger injuries or discomfort reported. The flight continued to the destination as per the concurrence of the Dispatcher with no further issues.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.