<< >> NASA ASRS Report 250552, August 1993

Atx X unauthorized descent below assigned altitude due to aircraft equipment problem pressurization had less than standard separation from small aircraft Y.

Attributes
ACN	250552
Time
Date	199308
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : rqz
State Reference	AL
Altitude	msl bound lower : 11000 msl bound upper : 11300
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Operator	common carrier : air taxi
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : ztl
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 2 controller radar : 7
ASRS Report	250552
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time total : 3100
ASRS Report	250694
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem flight crew : declared emergency
Consequence	faa : investigated
Miss Distance	horizontal : 25200 vertical : 400
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Atx X lost cabin pressure and said he had to descend to 10000 ft. Atx X was only cleared to 12000 ft. Atx X descended to 11300 ft which was less than standard separation from small aircraft Y. Atx X didn't declare an emergency, which I feel he should have or I should have done it for him. He should not have started his descent on his own. Supplemental information from acn 250694: atx X was cruising at 16000 ft en route to bna from mgm via vuz to rqz, vols arrival. In between mgm and rgz a flow duct separated from an engine causing a cabin altitude light to come on due to rapidly rising cabin altitude. We took the action depicted by our quick reference handbook and contacted ZTL to descend to 10000 ft. We were cleared to 12000 ft and began our descent. I contacted ZTL again and told them we needed 10000 ft. He said he was unable due to traffic. I said we need a vector, we need 10000 ft. He said ok, and gave us a turn. At approximately 11500 ft we were able to stabilize our cabin altitude with the remaining flow.

Related reports:

• An atx flight crew loses pressurization in their light trans...

	Enter your search terms Submit search form
	Web www.37000feet.com

Original NASA ASRS Text

Title: ATX X UNAUTH DSCNT BELOW ASSIGNED ALT DUE TO ACFT EQUIP PROB PRESSURIZATION HAD LTSS FROM SMA Y.

Narrative: ATX X LOST CABIN PRESSURE AND SAID HE HAD TO DSND TO 10000 FT. ATX X WAS ONLY CLRED TO 12000 FT. ATX X DSNDED TO 11300 FT WHICH WAS LTSS FROM SMA Y. ATX X DIDN'T DECLARE AN EMER, WHICH I FEEL HE SHOULD HAVE OR I SHOULD HAVE DONE IT FOR HIM. HE SHOULD NOT HAVE STARTED HIS DSCNT ON HIS OWN. SUPPLEMENTAL INFO FROM ACN 250694: ATX X WAS CRUISING AT 16000 FT ENRTE TO BNA FROM MGM VIA VUZ TO RQZ, VOLS ARR. IN BTWN MGM AND RGZ A FLOW DUCT SEPARATED FROM AN ENG CAUSING A CABIN ALT LIGHT TO COME ON DUE TO RAPIDLY RISING CABIN ALT. WE TOOK THE ACTION DEPICTED BY OUR QUICK REF HANDBOOK AND CONTACTED ZTL TO DSND TO 10000 FT. WE WERE CLRED TO 12000 FT AND BEGAN OUR DSCNT. I CONTACTED ZTL AGAIN AND TOLD THEM WE NEEDED 10000 FT. HE SAID HE WAS UNABLE DUE TO TFC. I SAID WE NEED A VECTOR, WE NEED 10000 FT. HE SAID OK, AND GAVE US A TURN. AT APPROX 11500 FT WE WERE ABLE TO STABILIZE OUR CABIN ALT WITH THE REMAINING FLOW.

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.