Narrative:

Flight was scheduled from iad to hvn. Light icing was forecast en route. Cruising altitude was 15000 ft. Flight proceeded normally until approximately 40 mi north of sie on V39 when ATC issued a descent from 15000 ft to 11000 ft. Passing 12000 ft we began to accumulate light icing. We leveled at 11000 ft and activated deice boots (continuous ignition/propeller heat/elevator and engine deice had been on since 15000 ft at start of descent). They functioned normally and the wings appeared to shed the ice (approximately 1/2 inch) when selected. Additionally, a good tail indication was noted. The ice began to accumulate at a moderate rate and we asked for and received a descent to 9000 ft. At that altitude we were mostly in the clear. We continued to descend from 9000 ft to 5000 ft, 5000 ft to 4000 ft, and finally to 2000 ft while being vectored onto the ILS 2 at hvn. Operations at hvn relayed us the WX 1100 ft overcast 18 mi in light snow. We began the approach and intercepted the ILS final approximately 7 mi from GS intercept (FAF). At approximately 3 mi from FAF and at a speed of 185 KTS the stall warning stick shaker and 2 red stall lights activated. We increased power to maximum and began a slow climb out of 1800 ft. I reported to ATC we were executing missed approach and would need to climb to 3000 ft. They cleared us to 3000 ft and instructed us to turn to 240 degree heading. I stated we were unable because the shaker was still operating continuously. We gained as much airspeed as we could and I continued to cycle the boots as necessary. We eventually turned to 180 degree heading based on a PIREP that clear air was reported there. We continued to climb to 10000 ft. PIREPS for moderate to severe icing were issued between 11000 ft and 14000 ft. New york approach handed us off to jfk approach at which time I declared an emergency and requested emergency vehicles at jfk. We opted to go to jfk because the ceiling was 5500 ft overcast (the best in the immediate area) and the runways at jfk were of sufficient length to land no flap which we felt was the only option. During the divert to jfk the tail deice boot indication was intermittent. Ice on the wings was non existent when we leveled at 5000 ft as well as no ice noted on the wipers. However realizing that ice on the tail accumulates at a rate double on the wings, and that with the RPM levers high and the throttles at the maximum egt limits we were only indicating 230 KTS in cruise flight (we should have been well past vmo) we both surmised that the tail or airframe had ice. We could not detect and that was causing the deteriorated airspeed. The airplane also flew with less than normal responsiveness (i.e., mushy controls). We requested jfk vector us to a long final with minimal bank turns. This we felt would give us some time to shed some ice (outside air temperature was plus 7 degrees C). We did not want to hold though as the WX was quickly deteriorating. The approach was flown at 170 KTS clean until approximately 1000 ft AGL when we slowed to 150 KTS, lowered the gear and landed at vref of 130 KTS. These speeds were selected as we had performed a ctlability check at 5000 ft and successfully slowed to 160 KTS with no stall indication. Following maintenance inspection at jfk numerous holes were found in left wing boots and tail. Patches were loose or missing and the right stall vane heat was inoperative. All of the aforementioned had checked good on preflight. Recommendations based on previous problems encountered with the tail plane icing. Stricter maintenance requirement should be imposed to limit the extent to which the boots can be patched (we counted 8 patches on the left stabilizer and 9 on the right, as well as a large tear in a patch on the left wing). Excessive patching causes the boots to not fully inflate but to test good on the ground. After encountering conditions en route the patches which appeared to be securely attached on the ground, detach in-flight! These boots must be replaced, not patched. Callback conversation with reporter revealed the following information: reporter advised that the FAA is fully aware of the problem. The principal maintenance inspector has been involved. On postflt inspection, the left stall warning vane washot while the right one was not. He said his captain was sure they had both stall warning lights which would indicate both stall warnings worked but, although they got the stall warning lights and stick shaker, they did not get the stick pusher. They were never in a position to ascertain their apparent angle of attack visually. He said that postflt inspection also indicated that the deicer boots were working within tolerances.

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Original NASA ASRS Text

Title: LTT GETS CONTINUOUS STALL WARNING AFTER PICKING UP AIRFRAME ICE. EMER DECLARED.

Narrative: FLT WAS SCHEDULED FROM IAD TO HVN. LIGHT ICING WAS FORECAST ENRTE. CRUISING ALT WAS 15000 FT. FLT PROCEEDED NORMALLY UNTIL APPROX 40 MI N OF SIE ON V39 WHEN ATC ISSUED A DSCNT FROM 15000 FT TO 11000 FT. PASSING 12000 FT WE BEGAN TO ACCUMULATE LIGHT ICING. WE LEVELED AT 11000 FT AND ACTIVATED DEICE BOOTS (CONTINUOUS IGNITION/PROP HEAT/ELEVATOR AND ENG DEICE HAD BEEN ON SINCE 15000 FT AT START OF DSCNT). THEY FUNCTIONED NORMALLY AND THE WINGS APPEARED TO SHED THE ICE (APPROX 1/2 INCH) WHEN SELECTED. ADDITIONALLY, A GOOD TAIL INDICATION WAS NOTED. THE ICE BEGAN TO ACCUMULATE AT A MODERATE RATE AND WE ASKED FOR AND RECEIVED A DSCNT TO 9000 FT. AT THAT ALT WE WERE MOSTLY IN THE CLR. WE CONTINUED TO DSND FROM 9000 FT TO 5000 FT, 5000 FT TO 4000 FT, AND FINALLY TO 2000 FT WHILE BEING VECTORED ONTO THE ILS 2 AT HVN. OPS AT HVN RELAYED US THE WX 1100 FT OVCST 18 MI IN LIGHT SNOW. WE BEGAN THE APCH AND INTERCEPTED THE ILS FINAL APPROX 7 MI FROM GS INTERCEPT (FAF). AT APPROX 3 MI FROM FAF AND AT A SPD OF 185 KTS THE STALL WARNING STICK SHAKER AND 2 RED STALL LIGHTS ACTIVATED. WE INCREASED PWR TO MAX AND BEGAN A SLOW CLB OUT OF 1800 FT. I RPTED TO ATC WE WERE EXECUTING MISSED APCH AND WOULD NEED TO CLB TO 3000 FT. THEY CLRED US TO 3000 FT AND INSTRUCTED US TO TURN TO 240 DEG HDG. I STATED WE WERE UNABLE BECAUSE THE SHAKER WAS STILL OPERATING CONTINUOUSLY. WE GAINED AS MUCH AIRSPD AS WE COULD AND I CONTINUED TO CYCLE THE BOOTS AS NECESSARY. WE EVENTUALLY TURNED TO 180 DEG HDG BASED ON A PIREP THAT CLR AIR WAS RPTED THERE. WE CONTINUED TO CLB TO 10000 FT. PIREPS FOR MODERATE TO SEVERE ICING WERE ISSUED BTWN 11000 FT AND 14000 FT. NEW YORK APCH HANDED US OFF TO JFK APCH AT WHICH TIME I DECLARED AN EMER AND REQUESTED EMER VEHICLES AT JFK. WE OPTED TO GO TO JFK BECAUSE THE CEILING WAS 5500 FT OVCST (THE BEST IN THE IMMEDIATE AREA) AND THE RWYS AT JFK WERE OF SUFFICIENT LENGTH TO LAND NO FLAP WHICH WE FELT WAS THE ONLY OPTION. DURING THE DIVERT TO JFK THE TAIL DEICE BOOT INDICATION WAS INTERMITTENT. ICE ON THE WINGS WAS NON EXISTENT WHEN WE LEVELED AT 5000 FT AS WELL AS NO ICE NOTED ON THE WIPERS. HOWEVER REALIZING THAT ICE ON THE TAIL ACCUMULATES AT A RATE DOUBLE ON THE WINGS, AND THAT WITH THE RPM LEVERS HIGH AND THE THROTTLES AT THE MAX EGT LIMITS WE WERE ONLY INDICATING 230 KTS IN CRUISE FLT (WE SHOULD HAVE BEEN WELL PAST VMO) WE BOTH SURMISED THAT THE TAIL OR AIRFRAME HAD ICE. WE COULD NOT DETECT AND THAT WAS CAUSING THE DETERIORATED AIRSPD. THE AIRPLANE ALSO FLEW WITH LESS THAN NORMAL RESPONSIVENESS (I.E., MUSHY CTLS). WE REQUESTED JFK VECTOR US TO A LONG FINAL WITH MINIMAL BANK TURNS. THIS WE FELT WOULD GIVE US SOME TIME TO SHED SOME ICE (OUTSIDE AIR TEMP WAS PLUS 7 DEGS C). WE DID NOT WANT TO HOLD THOUGH AS THE WX WAS QUICKLY DETERIORATING. THE APCH WAS FLOWN AT 170 KTS CLEAN UNTIL APPROX 1000 FT AGL WHEN WE SLOWED TO 150 KTS, LOWERED THE GEAR AND LANDED AT VREF OF 130 KTS. THESE SPDS WERE SELECTED AS WE HAD PERFORMED A CTLABILITY CHK AT 5000 FT AND SUCCESSFULLY SLOWED TO 160 KTS WITH NO STALL INDICATION. FOLLOWING MAINT INSPECTION AT JFK NUMEROUS HOLES WERE FOUND IN L WING BOOTS AND TAIL. PATCHES WERE LOOSE OR MISSING AND THE R STALL VANE HEAT WAS INOP. ALL OF THE AFOREMENTIONED HAD CHKED GOOD ON PREFLT. RECOMMENDATIONS BASED ON PREVIOUS PROBS ENCOUNTERED WITH THE TAIL PLANE ICING. STRICTER MAINT REQUIREMENT SHOULD BE IMPOSED TO LIMIT THE EXTENT TO WHICH THE BOOTS CAN BE PATCHED (WE COUNTED 8 PATCHES ON THE L STABILIZER AND 9 ON THE R, AS WELL AS A LARGE TEAR IN A PATCH ON THE L WING). EXCESSIVE PATCHING CAUSES THE BOOTS TO NOT FULLY INFLATE BUT TO TEST GOOD ON THE GND. AFTER ENCOUNTERING CONDITIONS ENRTE THE PATCHES WHICH APPEARED TO BE SECURELY ATTACHED ON THE GND, DETACH INFLT! THESE BOOTS MUST BE REPLACED, NOT PATCHED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT THE FAA IS FULLY AWARE OF THE PROB. THE PRINCIPAL MAINT INSPECTOR HAS BEEN INVOLVED. ON POSTFLT INSPECTION, THE L STALL WARNING VANE WASHOT WHILE THE R ONE WAS NOT. HE SAID HIS CAPT WAS SURE THEY HAD BOTH STALL WARNING LIGHTS WHICH WOULD INDICATE BOTH STALL WARNINGS WORKED BUT, ALTHOUGH THEY GOT THE STALL WARNING LIGHTS AND STICK SHAKER, THEY DID NOT GET THE STICK PUSHER. THEY WERE NEVER IN A POS TO ASCERTAIN THEIR APPARENT ANGLE OF ATTACK VISUALLY. HE SAID THAT POSTFLT INSPECTION ALSO INDICATED THAT THE DEICER BOOTS WERE WORKING WITHIN TOLERANCES.

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.