LEAR31 CAPT REPORTS HARD LANDING WITH DAMAGE TO TAIL FINS CAUSED BY UNDETECTED ICE ON WINGS AND SUBSEQUENT STALL AT 100 FEET AGL.

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THE FLT ENTERED THE CLOUDS AT APPROX 4500 FT DURING THE CLB TO 7000 FT. INFLT TEMP WAS RECALLED TO BE -4 DEGS C. NACELLE; PLUS WING/STABILIZER HEAT WAS TURNED ON PRIOR TO ENTERING THE CLOUDS. CLOUD TOPS WERE RAGGED AT 7000 FT. RIME ICE ACCUMULATION WAS OBSERVED ON THE WINDSHIELD AT THE CRUISING ALT OF 7000 FT. THE WINDSHIELD HEAT WAS THEN TURNED ON. NO ICE WAS VISIBLE ON THE WING'S LEADING EDGE. ATC DSNDED THE ACFT TO 5000 FT WHERE THE ACFT WAS THEN SKIMMING THE CLOUD BASES AND NO ICE WAS OBSERVED. AFTER DSNDING TO 3000 FT AND WELL CLR OF CLOUDS THE NACELLE HEAT; WING/STABILIZER HEAT AND WINDSHIELD HEAT WERE TURNED OFF. AT APPROX 20 MI FROM THE FIELD THE ACFT WAS DSNDED BY ATC TO 2000 FT. AT APPROX 15 MI FROM THE FIELD THE ACFT RE-ENTERED THE CLOUDS. ATC REQUESTED A SPD OF 210 KTS OR LESS AND VECTORED THE ACFT FOR AN ILS APCH. UPON RE-ENTERING THE CLOUDS THE WING/STABILIZER AND NACELLE HEAT WERE TURNED ON AGAIN. THE CAPT WAS UNABLE TO VERIFY THE WING/STABILIZER HEAT SWITCH POS FROM THE R SEAT BUT NOTED THE WING'S TEMP IN THE NORMAL (GREEN) AREA USING THE WING TEMP INDICATOR. THE INDICATOR WAS SHOWING THE WING'S TEMP BARELY IN THE NORMAL (GREEN) AREA WITH THE PWR SETTING REQUIRED TO MAINTAIN ALT AT 210 KTS (APPROX 70% N1). NO 'FAULT' ANNUNCIATORS WERE PRESENT. A VISUAL CHK OF THE WING'S LEADING EDGE USING THE ICE INSPECTION LIGHT SHOWED NO ICE ON THE WING'S LEADING EDGE. NOTE: WITH THE ACFT'S WING HEAT OFF DURING FLT IN TEMPS THAT WERE INDICATED ON THIS DAY; THE WING TEMP WILL READ IN THE COLD/BLUE AREA. THE NACELLE HEAT WAS VERIFIED ON BY PRESENCE OF THE GREEN NAC ANNUNCIATOR. THE ACFT WAS VECTORED AND CLRED FOR THE APCH BY ATC AND WAS BEING FLOWN BY THE AUTOPLT. THE CREW CONFIGURED THE ACFT AND SLOWED TO THE CALCULATE VREF SPD RECOMMENDED BY THE CHKLIST AND OBSERVED CONDITIONS. THE AUTOPLT COUPLED TO THE ILS COURSE AND FLEW IT INBOUND. THE ACFT STARTED ITS DSCNT NORMALLY AT GS INTERCEPT; AND DSNDED OUT OF THE CLOUDS AT APPROX 1700 FT MSL (1250 FT AGL). THE ARPT RWY WAS CLEARLY IN SIGHT. A FINAL VISUAL INSPECTION OF THE WING'S LEADING EDGE BY THE CAPT DID NOT SHOW ANY TRACES OF ICE ON THE ACFT'S LEADING EDGE. AT THE SAME TIME THE COPLT DISCONNECTED THE AUTOPLT TO HAND FLY THE ACFT. WHEN THE AUTOPLT WAS DISCONNECTED BY THE COPLT THE ACFT SANK BELOW THE GS WHICH WAS NOTED BY THE CAPT AND A CORRECTION WAS MADE BY THE PF. THE FLT CONTINUED ON THE APCH AT THE RECOMMENDED VREF SPD. THE PITCH ATTITUDE; PWR SETTING; AIRSPD AND ANGLE OF ATTACK INDICATIONS WERE ALL READING NORMALLY FOR THE ACFT'S CURRENT CONFIGN. ON SHORT FINAL THE CAPT NOTED TO THE COPLT A SLIGHT DECREASE IN THE ACFT'S IAS. AT ALMOST THE EXACT TIME AND WITHOUT WARNING AND JUST SHY OF THE RWY AT APPROX 100 FT; THE ACFT EXPERIENCED AN EXTREMELY HIGH SINK RATE. THE CAPT IMMEDIATELY AND RAPIDLY APPLIED FULL THRUST TO BOTH ENGS. THE ACFT TOUCHED THE GND ON THE RWY AT A HIGH PITCH ATTITUDE. DIRECTIONAL CTL WAS MAINTAINED AND THE ACFT WAS BROUGHT TO A STOP AND TAXIED TO THE RAMP. AS A RESULT OF THE HIGH PITCH ATTITUDE DURING THE ACFT'S TOUCHDOWN THE ACFT'S DELTA FINS STRUCK THE GND. WHEN THE FLT CREW EXITED THE ACFT; ICE WAS SEEN ADHERING TO THE WING AND TAIL SURFACES. THERE WAS ICE ON THE LEADING EDGE TRIANGLES THAT ARE LOCATED BTWN THE STALL FENCES AND THERE WAS ICE LOCATED OUTBOARD OF THAT AREA TOWARDS THE TIP OF THE WING. THE ICE WAS NOT ON THE CTR PORTION OF THE LEADING EDGE; BUT AFT THE TIP OF THE LEADING EDGE BY AT LEAST 2 INCHES. THE ICE WAS 3/4 OF AN INCH WIDE BY 1/2 AN INCH WIDE IN THICKNESS AND LOCATED ON THE TOP AND BOTTOM OF THE WING. THERE WAS NO ICE PRESENT ON THE INBOARD SECTION OF THE WING FROM THE ROOT TO THE FIRST SET OF WING TRIANGLES. THE HORIZ STABILIZER HAD A SIMILAR ICE FORMATION IN WHICH ICE WAS PRESENT ON THE TOP AND BOTTOM PORTION OF THE HEATED BOOT BUT NOT ON THE TIP OF THE LEADING EDGE. CAPT'S NOTES: THERE ARE VARIOUS WAYS TO VERIFY THE WING/STABILIZER HEAT IS ON BESIDES NOTING SWITCH POS. 1) A RISE IN WING TEMP BY USE OF THE COCKPIT WING TEMP INDICATOR. 2) A SLIGHT BUMP FELT AND SEEN IN CABIN PRESSURE. 3) TAIL HEAT SHOULD BE WORKING NORMALLY IF THE STABILIZER HEAT ANNUNCIATOR IS NOT ILLUMINATED IN FLT WITH THE SWITCH IN THE ON POS. ALL ABOVE INDICATIONS WERE OBSERVED. THE ACFT'S ANTI-ICE WAS TURNED ON AND USED AS PER TRAINING AND LEARJET'S RECOMMENDATION WHICH STATES THAT THE ANTI-ICE EQUIP SHOULD BE ON ANY TIME THE TEMP IS +10 DEGS C OR BELOW AND FLYING IN VISIBLE MOISTURE. THE USE OF THE ACFT'S ICE CHK LIGHT CAN BE USEFUL TO SEE IF THERE IS ICE ACCUMULATION ON THE WING'S LEADING EDGE IF THE ICE IS FORMING ON THE TIP (CTR) OF THE WING'S LEADING EDGE. THE 3 INCH BLACK DOT THAT LEARJET USES TO HELP A PLT SEE THE FORMATION OF ICE AT NIGHT ON THE R WING'S LEADING EDGE WAS USELESS FOR THE CAPT (WHO WAS SITTING IN THE R SEAT) TO SEE THE ICE THAT FORMED ON TOP OF THE LEADING EDGE OUTSIDE THE BLACK DOT AREA. AS A RECOMMENDATION; A LARGER BLACK AREA PERHAPS 6 INCHES WIDE THAT COVERS THE ENTIRE ALUMINUM EDGE FROM TOP TO BOTTOM MIGHT HAVE BEEN HELPFUL TO THE CAPT FOR SEEING THAT ICE WAS PRESENT. SINCE THERE WAS AN INDICATION OF A WARM WING (NORMAL/GREEN INDICATION) AND THE FACT THAT NO ICE WAS VISUALLY SEEN ON THE ACFT'S WINDOW OR WING. THERE WAS NO REASON TO BELIEVE ICE WAS PRESENT ON ANY CRITICAL PART OF THE ACFT. IF THE PRESENCE OF ICE WAS SEEN; OR REMOTELY BELIEVED TO EXIST; WITHOUT QUESTION; THE APCH AND LNDG WOULD HAVE BEEN MADE WITH A MAX OF FLAPS 20 DEGS AND A VREF SPD OF VREF +15 KTS AS PER THE CHKLIST. THIS PROC IS A MEMORY ITEM TO MOST LEARJET CAPTS WHO FLY IN THE NORTHERN PARTS OF THE COUNTRY AS I DO. THERE WAS NEVER ANY INDICATION TO THE CAPT THAT THE ACFT'S WINGS WERE STALLED OR ABOUT TO STALL. PITCH; PWR; AIRSPD AND ANGLE OF ATTACK WERE ALL INDICATING NORMALLY FOR THE ACFT'S WT AND CONFIGN. ONCE ON THE GND THE COPLT DESCRIBED FEELING THE AILERONS 'SHAKING' ONCE HE DISCONNECTED THE AUTOPLT. THE COPLT DID NOT SHARE THIS INFO TO THE CAPT DURING THE APCH WHICH WOULD HAVE BEEN USEFUL INFO FOR THE CAPT TO DETERMINE THAT SOMETHING MIGHT BE WRONG. IN CONCLUSION; A THOROUGH CHK OF THE ACFT'S ANTI-ICE SYS IS CURRENTLY BEING ACCOMPLISHED TO DETERMINE THE POSSIBILITY OF A MALFUNCTION. I WOULD SUGGEST THE POSSIBILITY OF BOMBARDIER RESEARCHING THE IDEA OF MAKING THE 3 INCH BLACK SPOT LOCATED ON THE R WING'S LEADING EDGE LARGER TO POSSIBLY ALLOW FLT CREW THE ABILITY TO SEE ICE THAT MIGHT BE ACCUMULATING OUTSIDE THE CURRENT WING OBSERVATION AREA; IE; ON TOP OF THE LEADING EDGE.