Airliner at FL350 experiences compressor stall due icing.

Attributes
ACN	113765
Time
Date	198906
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : lrd
State Reference	TX
Altitude	msl bound lower : 34700 msl bound upper : 35000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 4000
ASRS Report	113765
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 190 flight time total : 9000 flight time type : 1000
ASRS Report	113766
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At FL350, moderate, sometimes light, turbulence in icing conditions, 20 NM from a line of thunderstorms. We had just finished our climb to FL350. We were a little slow due to all the anti-icing bleeds being open. Since it was minus 19 degree C, ram air temperature, we felt it was too cold to ice up and we felt we needed more speed to ensure safe buffet margin. Therefore, we turned off the engine and air foil anti-ice in order to get more thrust for acceleration. Moments after the engine anti-ice was turned off, #2 EPR became erratic. We put back on all anti-icing and ignition to override. I pulled back the #2 throttle about halfway immediately on noticing the EPR fluctuations. The engine compressor stalled for about 15-20 seconds. The captain took the aircraft controls after I pulled the throttle back and during the compressor stalls. He initiated a 500 FPM rate of descent in order to maintain airspeed. He simultaneously asked me to get a descent clearance. We were cleared to FL240 on the second call. We were passing 34,700'. After the 15-20 seconds of compressor stalls, the engine ran very well. We leveled at FL310 and stayed there.

Original NASA ASRS Text

Title: AIRLINER AT FL350 EXPERIENCES COMPRESSOR STALL DUE ICING.

Narrative: AT FL350, MODERATE, SOMETIMES LIGHT, TURBULENCE IN ICING CONDITIONS, 20 NM FROM A LINE OF TSTMS. WE HAD JUST FINISHED OUR CLIMB TO FL350. WE WERE A LITTLE SLOW DUE TO ALL THE ANTI-ICING BLEEDS BEING OPEN. SINCE IT WAS MINUS 19 DEG C, RAM AIR TEMPERATURE, WE FELT IT WAS TOO COLD TO ICE UP AND WE FELT WE NEEDED MORE SPEED TO ENSURE SAFE BUFFET MARGIN. THEREFORE, WE TURNED OFF THE ENGINE AND AIR FOIL ANTI-ICE IN ORDER TO GET MORE THRUST FOR ACCELERATION. MOMENTS AFTER THE ENGINE ANTI-ICE WAS TURNED OFF, #2 EPR BECAME ERRATIC. WE PUT BACK ON ALL ANTI-ICING AND IGNITION TO OVERRIDE. I PULLED BACK THE #2 THROTTLE ABOUT HALFWAY IMMEDIATELY ON NOTICING THE EPR FLUCTUATIONS. THE ENGINE COMPRESSOR STALLED FOR ABOUT 15-20 SECONDS. THE CAPT TOOK THE ACFT CONTROLS AFTER I PULLED THE THROTTLE BACK AND DURING THE COMPRESSOR STALLS. HE INITIATED A 500 FPM RATE OF DSCNT IN ORDER TO MAINTAIN AIRSPEED. HE SIMULTANEOUSLY ASKED ME TO GET A DSCNT CLRNC. WE WERE CLRED TO FL240 ON THE SECOND CALL. WE WERE PASSING 34,700'. AFTER THE 15-20 SECONDS OF COMPRESSOR STALLS, THE ENGINE RAN VERY WELL. WE LEVELED AT FL310 AND STAYED THERE.

Data retrieved from NASA's ASRS site as of August 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.