Narrative:

On apr/xx/97, at approximately XX30 hours local time, in narita, japan, I performed the duties of flight engineer on a flight from narita to honolulu, on B747-100 aircraft. Prior to flight, we, the 3 man crew, were advised by local aircraft maintenance personnel that the aircraft was legal to dispatch with a deferred maintenance write-up of both cabin pressurization outflow valves inoperative in the automatic mode, but ok in manual mode. We discussed the situation and agreed to accept and fly this aircraft to honolulu. On takeoff roll, at the onset of throttle movement to takeoff power, the cabin rate of climb rapidly pegged at 2000 FPM. I soon gained control of this surge in pressurization by toggling the manual outflow valve control switches in the down position to start the valves toward the closed position. The cabin rate of climb stabilized at approximately 500 FPM. I was able to gradually zero out the cabin rate of climb as the aircraft leveled at FL310. With an approximately 30 min ETA to landing in honolulu, a descent from FL350 was initiated. Throttles were retarded smoothly to approximately 1.20 EPR (not idle thrust). However, the cabin pressurization instantaneously pegged at 2000 FPM rate of climb. I immediately toggled the manual outflow valve control switches to further close the outflow valves and regain control of the surge. As the cabin began to rise very rapidly, my actions appeared to have no effect whatsoever. At about the same instant that I noticed the cabin altitude to be over 10000 ft, a series of erratic pressure surges occurred due to throttle movements for the aircraft descent. By this time the cabin altitude warning horn was sounding, the cabin altitude gauge was indicating approximately 13000 ft, the passenger oxygen masks had deployed in the cabin and I still had no control of the outflow valves. Finally, after some delay, the rate of climb began to react to my movement of the switches' position and the surge was under my control. I quickly positioned the valves so as to initiate a rather rapid cabin descent to under 10000 ft, then stabilized the rate of descent to approximately 500 FPM to touchdown in honolulu. During taxi in to the ramp, I had a particularly difficult time depressurizing the aircraft, finally getting it to what I thought was a depressurized condition. Later, the purser told me that the aircraft door at 1L could not be opened from the outside, that the aircraft must have still been partially pressurized, and that he had to open the door from the inside. Also a flight attendant told me that a pair of women's shoes, loose on the floor near some ducting, had apparently been sucked into the ducting, since the shoes could not be found. Later, when exiting the aircraft and discussing the matter with 2 mechanics, I was told that the insulating batts in the interior of the tail section, where the outflow valves are located, had come loose and were tight up against the outflow valves, restricting airflow. This fact could possibly explain my difficulty in depressurizing the aircraft on the ground and could possibly have hampered my attempts to regain, in a timely manner, positive control of the outflow valves during descent.

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Original NASA ASRS Text

Title: A B747-100 AT 35000 FT BEGINNING START OF DSCNT HAD FAILURE OF THE MANUAL MODE OF CABIN PRESSURIZATION SYS. BOTH VALVES. AUTO SYS PREVIOUSLY DEFERRED AS INOP.

Narrative: ON APR/XX/97, AT APPROX XX30 HRS LCL TIME, IN NARITA, JAPAN, I PERFORMED THE DUTIES OF FE ON A FLT FROM NARITA TO HONOLULU, ON B747-100 ACFT. PRIOR TO FLT, WE, THE 3 MAN CREW, WERE ADVISED BY LCL ACFT MAINT PERSONNEL THAT THE ACFT WAS LEGAL TO DISPATCH WITH A DEFERRED MAINT WRITE-UP OF BOTH CABIN PRESSURIZATION OUTFLOW VALVES INOP IN THE AUTOMATIC MODE, BUT OK IN MANUAL MODE. WE DISCUSSED THE SIT AND AGREED TO ACCEPT AND FLY THIS ACFT TO HONOLULU. ON TKOF ROLL, AT THE ONSET OF THROTTLE MOVEMENT TO TKOF PWR, THE CABIN RATE OF CLB RAPIDLY PEGGED AT 2000 FPM. I SOON GAINED CTL OF THIS SURGE IN PRESSURIZATION BY TOGGLING THE MANUAL OUTFLOW VALVE CTL SWITCHES IN THE DOWN POS TO START THE VALVES TOWARD THE CLOSED POS. THE CABIN RATE OF CLB STABILIZED AT APPROX 500 FPM. I WAS ABLE TO GRADUALLY ZERO OUT THE CABIN RATE OF CLB AS THE ACFT LEVELED AT FL310. WITH AN APPROX 30 MIN ETA TO LNDG IN HONOLULU, A DSCNT FROM FL350 WAS INITIATED. THROTTLES WERE RETARDED SMOOTHLY TO APPROX 1.20 EPR (NOT IDLE THRUST). HOWEVER, THE CABIN PRESSURIZATION INSTANTANEOUSLY PEGGED AT 2000 FPM RATE OF CLB. I IMMEDIATELY TOGGLED THE MANUAL OUTFLOW VALVE CTL SWITCHES TO FURTHER CLOSE THE OUTFLOW VALVES AND REGAIN CTL OF THE SURGE. AS THE CABIN BEGAN TO RISE VERY RAPIDLY, MY ACTIONS APPEARED TO HAVE NO EFFECT WHATSOEVER. AT ABOUT THE SAME INSTANT THAT I NOTICED THE CABIN ALT TO BE OVER 10000 FT, A SERIES OF ERRATIC PRESSURE SURGES OCCURRED DUE TO THROTTLE MOVEMENTS FOR THE ACFT DSCNT. BY THIS TIME THE CABIN ALT WARNING HORN WAS SOUNDING, THE CABIN ALT GAUGE WAS INDICATING APPROX 13000 FT, THE PAX OXYGEN MASKS HAD DEPLOYED IN THE CABIN AND I STILL HAD NO CTL OF THE OUTFLOW VALVES. FINALLY, AFTER SOME DELAY, THE RATE OF CLB BEGAN TO REACT TO MY MOVEMENT OF THE SWITCHES' POS AND THE SURGE WAS UNDER MY CTL. I QUICKLY POSITIONED THE VALVES SO AS TO INITIATE A RATHER RAPID CABIN DSCNT TO UNDER 10000 FT, THEN STABILIZED THE RATE OF DSCNT TO APPROX 500 FPM TO TOUCHDOWN IN HONOLULU. DURING TAXI IN TO THE RAMP, I HAD A PARTICULARLY DIFFICULT TIME DEPRESSURIZING THE ACFT, FINALLY GETTING IT TO WHAT I THOUGHT WAS A DEPRESSURIZED CONDITION. LATER, THE PURSER TOLD ME THAT THE ACFT DOOR AT 1L COULD NOT BE OPENED FROM THE OUTSIDE, THAT THE ACFT MUST HAVE STILL BEEN PARTIALLY PRESSURIZED, AND THAT HE HAD TO OPEN THE DOOR FROM THE INSIDE. ALSO A FLT ATTENDANT TOLD ME THAT A PAIR OF WOMEN'S SHOES, LOOSE ON THE FLOOR NEAR SOME DUCTING, HAD APPARENTLY BEEN SUCKED INTO THE DUCTING, SINCE THE SHOES COULD NOT BE FOUND. LATER, WHEN EXITING THE ACFT AND DISCUSSING THE MATTER WITH 2 MECHS, I WAS TOLD THAT THE INSULATING BATTS IN THE INTERIOR OF THE TAIL SECTION, WHERE THE OUTFLOW VALVES ARE LOCATED, HAD COME LOOSE AND WERE TIGHT UP AGAINST THE OUTFLOW VALVES, RESTRICTING AIRFLOW. THIS FACT COULD POSSIBLY EXPLAIN MY DIFFICULTY IN DEPRESSURIZING THE ACFT ON THE GND AND COULD POSSIBLY HAVE HAMPERED MY ATTEMPTS TO REGAIN, IN A TIMELY MANNER, POSITIVE CTL OF THE OUTFLOW VALVES DURING DSCNT.

Data retrieved from NASA's ASRS site as of July 2007 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.