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DC9-31 had automatic pressurization failure, but flight crew was able to use manual pressurization until FL310 when the left air conditioning pack tripped. At that time cabin pressure climbed rapidly and flight crew initiated emergency descent while unable to contact ATC due to frequency congestion. Pressurization control was regained at 14000 ft where they stayed.
| Attributes | |
| ACN | 401550 |
| Time | |
| Date | 199805 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : rod |
| State Reference | OH |
| Altitude | msl bound lower : 30000 msl bound upper : 31000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 30 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other descent other other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : instrument pilot : atp pilot : flight engineer pilot : commercial |
| Experience | flight time last 90 days : 250 flight time total : 2850 flight time type : 400 |
| ASRS Report | 401550 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : overcame equipment problem flight crew : declared emergency |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
Narrative:
Climbing through 9000 ft AGL departing pit, automatic- pressurization failed. With first officer flying, captain switched to manual pressurization. Aircraft leveled at 12000 ft so that cabin altitude could stabilize. After stabilization a climb to FL310 was initiated. After several mins of cruise at FL310 the left air conditioning pack tripped causing an uncontrolled ascent of the cabin altitude to approximately 13000-15000 ft. First officer was commanded by the captain to begin a descent to lower altitude. First officer departed FL310 while captain attempted to regain control of cabin and obtain ATC clearance. Due to frequency congestion and pressurization problem ATC clearance for a descent to FL240 then to 14000 ft was not obtained until aircraft was passing FL300. No emergency declared. Captain was able to regain pressurization control. Flight continued normally and without incident to its destination, flying at 14000 ft. During emergency descent, TCASII was closely monitored and no other traffic was observed in area. No passenger or crew complaints occurred due to physiological nature of incident.
Original NASA ASRS Text
Title: DC9-31 HAD AUTO PRESSURIZATION FAILURE, BUT FLC WAS ABLE TO USE MANUAL PRESSURIZATION UNTIL FL310 WHEN THE L AIR CONDITIONING PACK TRIPPED. AT THAT TIME CABIN PRESSURE CLBED RAPIDLY AND FLC INITIATED EMER DSCNT WHILE UNABLE TO CONTACT ATC DUE TO FREQ CONGESTION. PRESSURIZATION CTL WAS REGAINED AT 14000 FT WHERE THEY STAYED.
Narrative: CLBING THROUGH 9000 FT AGL DEPARTING PIT, AUTO- PRESSURIZATION FAILED. WITH FO FLYING, CAPT SWITCHED TO MANUAL PRESSURIZATION. ACFT LEVELED AT 12000 FT SO THAT CABIN ALT COULD STABILIZE. AFTER STABILIZATION A CLB TO FL310 WAS INITIATED. AFTER SEVERAL MINS OF CRUISE AT FL310 THE L AIR CONDITIONING PACK TRIPPED CAUSING AN UNCTLED ASCENT OF THE CABIN ALT TO APPROX 13000-15000 FT. FO WAS COMMANDED BY THE CAPT TO BEGIN A DSCNT TO LOWER ALT. FO DEPARTED FL310 WHILE CAPT ATTEMPTED TO REGAIN CTL OF CABIN AND OBTAIN ATC CLRNC. DUE TO FREQ CONGESTION AND PRESSURIZATION PROB ATC CLRNC FOR A DSCNT TO FL240 THEN TO 14000 FT WAS NOT OBTAINED UNTIL ACFT WAS PASSING FL300. NO EMER DECLARED. CAPT WAS ABLE TO REGAIN PRESSURIZATION CTL. FLT CONTINUED NORMALLY AND WITHOUT INCIDENT TO ITS DEST, FLYING AT 14000 FT. DURING EMER DSCNT, TCASII WAS CLOSELY MONITORED AND NO OTHER TFC WAS OBSERVED IN AREA. NO PAX OR CREW COMPLAINTS OCCURRED DUE TO PHYSIOLOGICAL NATURE OF INCIDENT.
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.