Emergency descent performed by a DC9-30 PIC with a failure of the pressurization system. PIC noted t...

Attributes
ACN	622083
Time
Date	200406
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zjx.artcc
State Reference	FL
Altitude	msl bound lower : 10000 msl bound upper : 31000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx.artcc
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5500 flight time type : 1500
ASRS Report	622083
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical cabin event other maintenance problem : improper maintenance other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance controller : provided flight assist flight crew : declared emergency flight crew : diverted to another airport flight crew : landed in emergency condition other
Consequence	other other
Factors
Maintenance	performance deficiency : inspection performance deficiency : logbook entry performance deficiency : repair performance deficiency : testing performance deficiency : fault isolation
Supplementary
Problem Areas	Flight Crew Human Performance Maintenance Human Performance Company Aircraft
Primary Problem	Aircraft

Narrative:

During cruise at FL310 experienced a cabin pressure abnormality. Cabin rose rapidly to 10000 ft. Master warning and red cabin pressure high annunciator light illuminated. Performed emergency memory items and initiated emergency rapid descent. Declared emergency. Elected to make precautionary landing at tlh. Autopressurization system had been written up in maintenance aircraft logbook many times during a 3 week period. In addition autopressurization irregularity occurred after takeoff on this flight, but after completing abnormality checklist, system reset and flight continued until emergency. Normally, on the company DC9 aircraft, with oxygen masks on, direct communications are only possible between pilots (intercom switch) and ATC (VHF 1 or 2 switch). The MD82 series aircraft which the company also has, have a direct oxygen mask PA and flight attendant 'int' switch. During the rapid descent, I was unable to talk to the flight attendants or passenger. In part, I was too busy with aircraft, my copilot and the checklist/emergency. I elected to descend to 10000 ft and then remove my oxygen mask and then speak to flight attendant and passenger. Communications under this procedure are very poor via hand set interphone and require oxygen mask removal. A real problem is smoke/fire is present. Postflt inspection and trials indicated DC9-30 lack of direct communication switch. Everyone thought communication was feasible and straight forward but after my emergency it was obviously not the case. Mixed aircraft types, lack of specific training, lax planning and safety procedures and poor consideration on the company's behalf led to a chain of events that led to inability of flight crew to communication with flight attendants via interphone on these aircraft. The company is now going to wire a switch to enable 2-WAY communication in such circumstances, and has implemented an interim measure to facilitate 2-WAY communication, albeit clumsy and invasive, involving transmitting into PA headset via 'int' speaker in the flight deck. The unscheduled landing was uneventful. We all learned a valuable lesson, the hard way.

Original NASA ASRS Text

Title: EMER DSCNT PERFORMED BY A DC9-30 PIC WITH A FAILURE OF THE PRESSURIZATION SYS. PIC NOTED THAT THE OXYGEN MASKS DID NOT ENABLE THE CREW TO COM WITH FLT ATTENDANT OR USE PA SYS.

Narrative: DURING CRUISE AT FL310 EXPERIENCED A CABIN PRESSURE ABNORMALITY. CABIN ROSE RAPIDLY TO 10000 FT. MASTER WARNING AND RED CABIN PRESSURE HIGH ANNUNCIATOR LIGHT ILLUMINATED. PERFORMED EMER MEMORY ITEMS AND INITIATED EMER RAPID DSCNT. DECLARED EMER. ELECTED TO MAKE PRECAUTIONARY LNDG AT TLH. AUTOPRESSURIZATION SYS HAD BEEN WRITTEN UP IN MAINT ACFT LOGBOOK MANY TIMES DURING A 3 WK PERIOD. IN ADDITION AUTOPRESSURIZATION IRREGULARITY OCCURRED AFTER TKOF ON THIS FLT, BUT AFTER COMPLETING ABNORMALITY CHKLIST, SYS RESET AND FLT CONTINUED UNTIL EMER. NORMALLY, ON THE COMPANY DC9 ACFT, WITH OXYGEN MASKS ON, DIRECT COMS ARE ONLY POSSIBLE BTWN PLTS (INTERCOM SWITCH) AND ATC (VHF 1 OR 2 SWITCH). THE MD82 SERIES ACFT WHICH THE COMPANY ALSO HAS, HAVE A DIRECT OXYGEN MASK PA AND FLT ATTENDANT 'INT' SWITCH. DURING THE RAPID DSCNT, I WAS UNABLE TO TALK TO THE FLT ATTENDANTS OR PAX. IN PART, I WAS TOO BUSY WITH ACFT, MY COPLT AND THE CHKLIST/EMER. I ELECTED TO DSND TO 10000 FT AND THEN REMOVE MY OXYGEN MASK AND THEN SPEAK TO FLT ATTENDANT AND PAX. COMS UNDER THIS PROC ARE VERY POOR VIA HAND SET INTERPHONE AND REQUIRE OXYGEN MASK REMOVAL. A REAL PROB IS SMOKE/FIRE IS PRESENT. POSTFLT INSPECTION AND TRIALS INDICATED DC9-30 LACK OF DIRECT COM SWITCH. EVERYONE THOUGHT COM WAS FEASIBLE AND STRAIGHT FORWARD BUT AFTER MY EMER IT WAS OBVIOUSLY NOT THE CASE. MIXED ACFT TYPES, LACK OF SPECIFIC TRAINING, LAX PLANNING AND SAFETY PROCS AND POOR CONSIDERATION ON THE COMPANY'S BEHALF LED TO A CHAIN OF EVENTS THAT LED TO INABILITY OF FLT CREW TO COM WITH FLT ATTENDANTS VIA INTERPHONE ON THESE ACFT. THE COMPANY IS NOW GOING TO WIRE A SWITCH TO ENABLE 2-WAY COM IN SUCH CIRCUMSTANCES, AND HAS IMPLEMENTED AN INTERIM MEASURE TO FACILITATE 2-WAY COM, ALBEIT CLUMSY AND INVASIVE, INVOLVING XMITTING INTO PA HEADSET VIA 'INT' SPEAKER IN THE FLT DECK. THE UNSCHEDULED LNDG WAS UNEVENTFUL. WE ALL LEARNED A VALUABLE LESSON, THE HARD WAY.

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.

Emergency descent performed by a DC9-30 PIC with a failure of the pressurization system. PIC noted that the oxygen masks did not enable the crew to communication with flight attendant or use PA system.