An MD80 crew reported dual pack failures descending through FL300 IMC while both engine and airfoil anti-ice were on. With oxygen masks on and working the QRH the cabin altitude reached 11;500 before the crew was able to restore both packs to normal operation.
Synopsis
An MD80 crew reported dual pack failures descending through FL300 IMC while both engine and airfoil anti-ice were on. With oxygen masks on and working the QRH the cabin altitude reached 11;500 before the crew was able to restore both packs to normal operation.
Narrative
Enroute; level at FL360 in IMC conditions; engine and airfoil heat on. 'Pressurization Flow' light illuminated; right pack 0 flow; supply temperature 150 with right air mix valve full hot. Both left and right pack temperature controllers where being operated in auto. Almost concurrently; descent clearance received from Center to FL200. Passing through FL300 control of cabin reestablished. Cabin altitude approximately 8;000 FT and descending. A few minutes later the left pack went to zero flow. Air mix value showed mid-position and supply temperature showed 80. Received clearance to 10;000 FT. Cabin climbing 1;500 FT/min. Notified Flight Attendants of nature of situation. 'Cabin Altitude' light illuminated and cockpit masks donned and QRH procedures followed. Left pack began working again passing through 15;000 FT. Maximum cabin altitude reached was approximately 11;500 FT with left pack operating; control of pressurization was regained. Leveled at 10;000 FT; now in VMC conditions. Right pack began operating again after leveling of the 10;000 FT. Continued in VMC conditions to our destination where normal landing occurred. Debriefed event with Maintenance Control where it was determined that both packs had history of write ups going back a number of weeks.
Second reporter narrative
Enroute at FL360; near top of descent; received clearance to descend to FL200. Almost simultaneously with clearance got master caution and pressurization flow lights. Noticed right pack flow gage at zero; right pack valve gage full hot and cabin supply temperature pegged at 150 degrees. Started decent using speed brakes with power up. Complied with QRH procedures for pressure flow light and air conditioning flow below 9 o'clock position. Cabin altitude approximately 8;000 FT and climbing. At approximately FL300 regained control of cabin altitude with cabin at approximately 9;000 FT and now descending. Shortly there after left pack quit and cabin altitude started rising at approximately 1;500 FT per minute. We donned 02 masks checked terrain ahead and told ATC we needed immediate decent to 10;000 FT. Captain quickly called Flight Attendants and told them to prepare for possible cabin depressurization. Complied with QRH for cabin altitude warning as cabin reached 10;000 FT and climbing; and reached a max of 11;500 FT. At approximately 15;000 FT left pack began to operate and cabin began to descend from 11;500 FT. Leveled aircraft at 10;000 FT and right pack also began to work. Pressurization worked normal until landing. Note Maintenance found history of air conditioning problems with this aircraft and upon inspection found right pack turbine sensor loose; and cleaned all cannon plugs and sensors on left pack.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.