Altitude deviation altitude excursion in icing conditions.

Attributes
ACN	250881
Time
Date	199309
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ewa
State Reference	MS
Altitude	msl bound lower : 19500 msl bound upper : 20000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 300 flight time total : 9000 flight time type : 2000
ASRS Report	250881
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly
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	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

During cruise flight at FL200 120 NM out of ewa 234 degrees on a flight from atl to gtr, we encountered severe icing. ATC advised us to rerte from vuz to mei for WX. We were in the process when we started picking up ice. We turned on all ice protection and planned a descent and a turn north at mei. Ice started to increase to about an inch when I noticed a decrease in airspeed from 180 KTS to 140 KTS and maximum cruise was already applied. I asked the first officer to call ATC and tell them we needed lower. With no power left and the aircraft at vref, a stall buffet started. I was forced to start descending without an ATC clearance despite our attempts to call. We had descended to 19500 before making contact and receiving 12000 ft from ATC. The ice had grown to 2 inches and it only took 30 seconds for the incident to occur and ATC responded before I could squawk 7700. I was more concerned with the advanced stall situation than with the clearance, and the first officer was occupied with the ice boots and the chatter on center frequency to change squawk codes. With an outside air temperature of only -5 degrees C and the lack of heavy precipitation, I was surprised at how fast the situation deteriorated.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION IN ICING CONDITIONS.

Narrative: DURING CRUISE FLT AT FL200 120 NM OUT OF EWA 234 DEGS ON A FLT FROM ATL TO GTR, WE ENCOUNTERED SEVERE ICING. ATC ADVISED US TO RERTE FROM VUZ TO MEI FOR WX. WE WERE IN THE PROCESS WHEN WE STARTED PICKING UP ICE. WE TURNED ON ALL ICE PROTECTION AND PLANNED A DSCNT AND A TURN N AT MEI. ICE STARTED TO INCREASE TO ABOUT AN INCH WHEN I NOTICED A DECREASE IN AIRSPD FROM 180 KTS TO 140 KTS AND MAX CRUISE WAS ALREADY APPLIED. I ASKED THE FO TO CALL ATC AND TELL THEM WE NEEDED LOWER. WITH NO PWR LEFT AND THE ACFT AT VREF, A STALL BUFFET STARTED. I WAS FORCED TO START DSNDING WITHOUT AN ATC CLRNC DESPITE OUR ATTEMPTS TO CALL. WE HAD DSNDED TO 19500 BEFORE MAKING CONTACT AND RECEIVING 12000 FT FROM ATC. THE ICE HAD GROWN TO 2 INCHES AND IT ONLY TOOK 30 SECONDS FOR THE INCIDENT TO OCCUR AND ATC RESPONDED BEFORE I COULD SQUAWK 7700. I WAS MORE CONCERNED WITH THE ADVANCED STALL SIT THAN WITH THE CLRNC, AND THE FO WAS OCCUPIED WITH THE ICE BOOTS AND THE CHATTER ON CTR FREQ TO CHANGE SQUAWK CODES. WITH AN OUTSIDE AIR TEMP OF ONLY -5 DEGS C AND THE LACK OF HVY PRECIPITATION, I WAS SURPRISED AT HOW FAST THE SIT DETERIORATED.

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.