Narrative:

We departed on a repositioning flight back to buffalo; ny. Our altitude was 5000 ft MSL and we were just on top of a cloud layer. As we proceeded toward our destination the tops rose and we found ourselves IFR with all anti-icing equipment on and indicating as such. ATC cleared our flight to descend to 4000 ft; at which time we were picking up moderate rime ice. I advised ATC of this and they cleared our flight to descend to 2300 ft. The first officer was flying the aircraft and I began to prepare for the approach phase of the flight. Without warning; the aircraft went into a stall and started to descend unctlably. The first officer responded immediately with full thrust which could not negate the stall situation. With the aircraft shaking and stalling it took both of us and CRM to identify airspeed; climb or descent and keep the aircraft flying in a stall condition. After much erratic operation we were able to climb the aircraft to VFR conditions on top (approximately 8000 ft MSL) where it was still shaking and very low airspeed although we were still at full thrust. During the whole procedure I believe I notified buffalo approach we had problems and we were attempting to climb. When we got on top; I then advised buffalo approach of our situation and the need to divert to an airport with VFR conditions. As we began to stabilize the aircraft the angle of attack and airspeed began to slowly return to normal indications. We diverted and briefed for a landing with ice on the aircraft. We could see a large ice accumulation on the nose of the tip tanks and the windscreen was still trying to clear. The aircraft was landed at rochester international without further occurrences. After parking; a large amount of rime ice was present on the aircraft. It was determined by maintenance that the stabilizer heat had failed and the aircraft encountered a tail plane icing stall. Further investigation revealed that seals located in the elbow section of the bleed air had been improperly installed and had failed. Prior to the stall we had no indication of reduced airspeed; aircraft shudder or angle of attack movement; the first indication we received was the significant buffeting and descent.

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Original NASA ASRS Text

Title: LEAR 35 FLT CREW ENCOUNTERS ICING CONDITIONS; ACFT STALLS; FLT CREW REGAINS ACFT CTL AND DIVERTS TO ANOTHER ARPT; LANDS SAFELY.

Narrative: WE DEPARTED ON A REPOSITIONING FLT BACK TO BUFFALO; NY. OUR ALT WAS 5000 FT MSL AND WE WERE JUST ON TOP OF A CLOUD LAYER. AS WE PROCEEDED TOWARD OUR DEST THE TOPS ROSE AND WE FOUND OURSELVES IFR WITH ALL ANTI-ICING EQUIP ON AND INDICATING AS SUCH. ATC CLRED OUR FLT TO DSND TO 4000 FT; AT WHICH TIME WE WERE PICKING UP MODERATE RIME ICE. I ADVISED ATC OF THIS AND THEY CLRED OUR FLT TO DSND TO 2300 FT. THE FO WAS FLYING THE ACFT AND I BEGAN TO PREPARE FOR THE APCH PHASE OF THE FLT. WITHOUT WARNING; THE ACFT WENT INTO A STALL AND STARTED TO DSND UNCTLABLY. THE FO RESPONDED IMMEDIATELY WITH FULL THRUST WHICH COULD NOT NEGATE THE STALL SITUATION. WITH THE ACFT SHAKING AND STALLING IT TOOK BOTH OF US AND CRM TO IDENT AIRSPD; CLB OR DSCNT AND KEEP THE ACFT FLYING IN A STALL CONDITION. AFTER MUCH ERRATIC OP WE WERE ABLE TO CLB THE ACFT TO VFR CONDITIONS ON TOP (APPROX 8000 FT MSL) WHERE IT WAS STILL SHAKING AND VERY LOW AIRSPD ALTHOUGH WE WERE STILL AT FULL THRUST. DURING THE WHOLE PROC I BELIEVE I NOTIFIED BUFFALO APCH WE HAD PROBS AND WE WERE ATTEMPTING TO CLB. WHEN WE GOT ON TOP; I THEN ADVISED BUFFALO APCH OF OUR SITUATION AND THE NEED TO DIVERT TO AN ARPT WITH VFR CONDITIONS. AS WE BEGAN TO STABILIZE THE ACFT THE ANGLE OF ATTACK AND AIRSPD BEGAN TO SLOWLY RETURN TO NORMAL INDICATIONS. WE DIVERTED AND BRIEFED FOR A LNDG WITH ICE ON THE ACFT. WE COULD SEE A LARGE ICE ACCUMULATION ON THE NOSE OF THE TIP TANKS AND THE WINDSCREEN WAS STILL TRYING TO CLR. THE ACFT WAS LANDED AT ROCHESTER INTL WITHOUT FURTHER OCCURRENCES. AFTER PARKING; A LARGE AMOUNT OF RIME ICE WAS PRESENT ON THE ACFT. IT WAS DETERMINED BY MAINT THAT THE STABILIZER HEAT HAD FAILED AND THE ACFT ENCOUNTERED A TAIL PLANE ICING STALL. FURTHER INVESTIGATION REVEALED THAT SEALS LOCATED IN THE ELBOW SECTION OF THE BLEED AIR HAD BEEN IMPROPERLY INSTALLED AND HAD FAILED. PRIOR TO THE STALL WE HAD NO INDICATION OF REDUCED AIRSPD; ACFT SHUDDER OR ANGLE OF ATTACK MOVEMENT; THE FIRST INDICATION WE RECEIVED WAS THE SIGNIFICANT BUFFETING AND DSCNT.

Data retrieved from NASA's ASRS site as of January 2009 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.