Altitude deviation altitude excursion during emergency descent when aircraft equipment problem is en...

Attributes
ACN	181305
Time
Date	199106
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : vhp
State Reference	IN
Altitude	msl bound lower : 33500 msl bound upper : 34000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other descent other other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 3150 flight time type : 850
ASRS Report	181305
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : declared emergency flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

In cruise at FL350 we felt a 'thump' and watched as our cabin altitude began to climb at a rate of approximately 2000 FPM. We immediately donned our oxygen masks and requested a descent due to 'pressurization problems.' we were given a 20 degree vector to the south of descent clearance. We again informed ATC that we needed to get down because of our situation. Our cabin altitude was already in excess of 8000'. ATC (indy center) now responded by bringing us down to FL340. We began an immediate descent but because our cabin altitude was at 10000' and still climbing I did not stop at FL340 but rather continued the descent. The WX conditions were excellent and no traffic was observed. Upon descending through 33500', ATC cleared us to FL310. Our cabin altitude was still climbing at 2000 FPM. As we descended through FL310 we were cleared to FL240. At this time we informed ATC that we needed to get down to 12000'. They responded by asking us if we wished to declare an emergency. We told them that wouldn't be necessary if they could get us down to 12000'. After that transmission we were cleared to 12000'. Our cabin altitude peaked at 15000' and our passengers were on oxy the entire time. My concern is with ATC's delay in getting us down after we repeatedly informed them of our situation and also my descent below an assigned altitude. I felt my options were running out and I did what I felt was in the best interests of my passengers west/O disregard for other aircraft in the area. I believe ATC has to be better prepared for these types of situations. Callback conversation with reporter revealed the following information. Reporter was acting as first officer at the time and his 'boss' was the PIC. Reporter stated that his boss hates to fill out paperwork and quite possibly that was one reason for not declaring an emergency. Reporter counseled on the applicability of doing so with the associated advantages. No further problems with ATC or pending action.

Original NASA ASRS Text

Title: ALT DEVIATION ALT EXCURSION DURING EMERGENCY DESCENT WHEN ACFT EQUIPMENT PROBLEM IS ENCOUNTERED RESULTING IN LOSS OF CABIN PRESSURE.

Narrative: IN CRUISE AT FL350 WE FELT A 'THUMP' AND WATCHED AS OUR CABIN ALT BEGAN TO CLB AT A RATE OF APPROX 2000 FPM. WE IMMEDIATELY DONNED OUR OXYGEN MASKS AND REQUESTED A DSNT DUE TO 'PRESSURIZATION PROBS.' WE WERE GIVEN A 20 DEG VECTOR TO THE S OF DSNT CLRNC. WE AGAIN INFORMED ATC THAT WE NEEDED TO GET DOWN BECAUSE OF OUR SITUATION. OUR CABIN ALT WAS ALREADY IN EXCESS OF 8000'. ATC (INDY CTR) NOW RESPONDED BY BRINGING US DOWN TO FL340. WE BEGAN AN IMMEDIATE DSNT BUT BECAUSE OUR CABIN ALT WAS AT 10000' AND STILL CLBING I DID NOT STOP AT FL340 BUT RATHER CONTINUED THE DSNT. THE WX CONDITIONS WERE EXCELLENT AND NO TFC WAS OBSERVED. UPON DSNDING THROUGH 33500', ATC CLRED US TO FL310. OUR CABIN ALT WAS STILL CLBING AT 2000 FPM. AS WE DSNDED THROUGH FL310 WE WERE CLRED TO FL240. AT THIS TIME WE INFORMED ATC THAT WE NEEDED TO GET DOWN TO 12000'. THEY RESPONDED BY ASKING US IF WE WISHED TO DECLARE AN EMER. WE TOLD THEM THAT WOULDN'T BE NECESSARY IF THEY COULD GET US DOWN TO 12000'. AFTER THAT XMISSION WE WERE CLRED TO 12000'. OUR CABIN ALT PEAKED AT 15000' AND OUR PAXS WERE ON OXY THE ENTIRE TIME. MY CONCERN IS WITH ATC'S DELAY IN GETTING US DOWN AFTER WE REPEATEDLY INFORMED THEM OF OUR SITUATION AND ALSO MY DSNT BELOW AN ASSIGNED ALT. I FELT MY OPTIONS WERE RUNNING OUT AND I DID WHAT I FELT WAS IN THE BEST INTERESTS OF MY PAXS W/O DISREGARD FOR OTHER ACFT IN THE AREA. I BELIEVE ATC HAS TO BE BETTER PREPARED FOR THESE TYPES OF SITUATIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR WAS ACTING AS F/O AT THE TIME AND HIS 'BOSS' WAS THE PIC. RPTR STATED THAT HIS BOSS HATES TO FILL OUT PAPERWORK AND QUITE POSSIBLY THAT WAS ONE REASON FOR NOT DECLARING AN EMER. RPTR COUNSELED ON THE APPLICABILITY OF DOING SO WITH THE ASSOCIATED ADVANTAGES. NO FURTHER PROBS WITH ATC OR PENDING ACTION.

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.

Altitude deviation altitude excursion during emergency descent when aircraft equipment problem is encountered resulting in loss of cabin pressure.