Encountered heavy rime icing unable to maintain altitude. Descended without clearance.

Attributes
ACN	171136
Time
Date	199102
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : syr
State Reference	NY
Altitude	msl bound lower : 9000 msl bound upper : 14000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Route In Use	enroute airway : zbw
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 9000 flight time type : 900
ASRS Report	171136
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 140 flight time total : 5000
ASRS Report	170957
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : declared emergency flight crew : exited adverse environment
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Weather

Narrative:

Flight was given cruise descent clearance to 16000' from 20000'. Upon level off in IMC with all anti-ice equipment systems in use we started picking up mostly severe occasional moderate rime ice. We immediately informed bos center of ice and asked for lower. We were given 14000' and continued to pick up moderate rime. Upon level off at 14000' ice accumulation continued and aircraft became incapable of maintaining altitude with almost maximum power. We requested lower due to ice however center did not respond quickly enough and we then advised center we were descending to lower altitude and please clear other aircraft from our area. At 9000' ice accumulation stopped and we were able to maintain altitude. Center told us during descent, if we had told him of icing he would have responded sooner. Both first officer and myself were astonished, we had in fact told this center controller several times. Also there were no reports of or sigmets regarding icing. We did contact syr approach bos center and dispatch with a PIREP. 1 hour later we checked local reports still no published PIREPS? Suggest less controller workload and more timely dissemination of met condition on air carrier frequencys.

Original NASA ASRS Text

Title: ENCOUNTERED HEAVY RIME ICING UNABLE TO MAINTAIN ALT. DESCENDED WITHOUT CLRNC.

Narrative: FLT WAS GIVEN CRUISE DSNT CLRNC TO 16000' FROM 20000'. UPON LEVEL OFF IN IMC WITH ALL ANTI-ICE EQUIP SYSTEMS IN USE WE STARTED PICKING UP MOSTLY SEVERE OCCASIONAL MODERATE RIME ICE. WE IMMEDIATELY INFORMED BOS CTR OF ICE AND ASKED FOR LOWER. WE WERE GIVEN 14000' AND CONTINUED TO PICK UP MODERATE RIME. UPON LEVEL OFF AT 14000' ICE ACCUMULATION CONTINUED AND ACFT BECAME INCAPABLE OF MAINTAINING ALT WITH ALMOST MAX PWR. WE REQUESTED LOWER DUE TO ICE HOWEVER CTR DID NOT RESPOND QUICKLY ENOUGH AND WE THEN ADVISED CTR WE WERE DSNDING TO LOWER ALT AND PLEASE CLR OTHER ACFT FROM OUR AREA. AT 9000' ICE ACCUMULATION STOPPED AND WE WERE ABLE TO MAINTAIN ALT. CTR TOLD US DURING DSNT, IF WE HAD TOLD HIM OF ICING HE WOULD HAVE RESPONDED SOONER. BOTH F/O AND MYSELF WERE ASTONISHED, WE HAD IN FACT TOLD THIS CTR CTLR SEVERAL TIMES. ALSO THERE WERE NO RPTS OF OR SIGMETS REGARDING ICING. WE DID CONTACT SYR APCH BOS CTR AND DISPATCH WITH A PIREP. 1 HR LATER WE CHKED LCL RPTS STILL NO PUBLISHED PIREPS? SUGGEST LESS CTLR WORKLOAD AND MORE TIMELY DISSEMINATION OF MET CONDITION ON AIR CARRIER FREQS.

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.