AUTOPLT ON COUPLED APCH FLARES 10 FT ABOVE THE RWY AND DRAGS TAIL AFTER FLOATING 4000 FT.

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AUTOLAND TO RWY 36 AT DCA. AT THROTTLE RETARD ACFT LEVELED OFF AT ABOUT 10 FT AGL AND WOULD NOT LAND. WENT AROUND AND GOT TAIL STRIKE ON GAR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: CAPT RPTS THAT THIS EVENT WAS NOT A PLT INDUCED TAIL STRIKE. THE READ OUT OF THE TAPES INDICATE THAT THE TAIL STRIKE OCCURRED WITH THE AUTOPLT ON. THE ACFT FLARED AND MAINTAINED 10 FT; ACFT SLOWED TO 108 KTS; FLOATED FOR ABOUT 4000 FT AND PITCHED TO 13.7 DEGS. THERE WAS A 40 KT TAILWIND AT ABOUT 2500 FT MSL AND A 20 KT TAILWIND AT 1000 FT MSL AND A VERY LIGHT TAILWIND ON LNDG. THIS WAS THE FIRST AUTOLAND IN THIS ACFT FOR THIS CAPT. THE RWY WAS WET WITH MODERATE RAIN; AT NIGHT; A 300-400 FT CEILING AND 2-3 MI VISIBILITY. SINCE THIS EXPERIENCE; THE CAPT HAS LEARNED OF 2 OTHER EXTENDED FLOAT INCIDENTS. THE CAPT ELECTED TO GAR WHEN HE FELT THERE WAS NO LONGER ENOUGH RWY TO STOP. THE ACFT HAS TO LOG AT LEAST 1 AUTOLAND EVERY 30 DAYS. AS THE ACFT LEVELED OFF; THE FLC WERE LOOKING OUTSIDE AND WOULD CONFIRM THE FLT RECORDER TAPE THAT THE ACFT HAD LEVELED OFF AT ABOUT 10 FT HIGH. CAT II CONDITIONS DID NOT ACTUALLY EXIST SO ACFT MAY HAVE BEEN LOCATED ON THE ARPT TO CREATE AN INTERFERENCE WITH THE ILS RECEPTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THE FO STATES THAT FINAL WAS INTERCEPTED ABOVE THE GS ABOUT 3 MI OUTSIDE OXON AND THERE WAS A 23 KT TAILWIND. THE WINDS WERE RPTED CALM BY THE TWR. IF THE TWR HAD EXCESSIVE TAILWIND THE CEILING AND VISIBILITY WOULD HAVE CLOSED THE ARPT. THE OLEO STRUTS ARE HARD AND AUTOLNDGS ARE EXCESSIVELY FIRM. TO COUNTERACT THIS A LOGIC OF A KIND OF 2 STAGE LNDG FLARE IS BUILT IN TO THE AUTOPLT. ALSO; THE NORMAL FLARE IS 43 FT; BUT IF THE LOGIC SENSES AN UPSLOPE THE FLARE MAY COMMENCE AT 50 FT. ON A WET RWY WITH MODERATE RAIN AND PERHAPS A TAILWIND; AND A RWY THAT IS ONLY A MARGINAL 5;869 FT BEYOND THE GS; A PLT WOULD WANT THE AIRPLANE TO SQUAT WITHOUT TOO MANY SECONDS DELAY. CONSIDERING AT 120 KTS; THE DISTANCE FROM THE WATER AHEAD IS REDUCING AT 200 FT PER SECOND THE FLT RECORDER TAPES INDICATE THE CREW WAS PATIENT. THE COPLT HAD NOTIFIED THE APCH CTL AND THE TWR THEY WERE DOING THE AUTOLAND AND BELIEVES THEIR CAT II AREA OF INTERFERENCE WAS NOT INTRUDED ON BY OTHER ACFT. THE COPLT HAS 500 HRS IN THE AIRPLANE; AND THOUGH THE CAPT WAS NEW TO THIS AIRPLANE THOUGHT HE DID GOOD. THE COPLT CALLED GAR WHEN HE DID NOT THINK THE ACFT WOULD STOP ON THE REMAINING RWY. AS THE CAPT PUSHED THE THRUST LEVER TO THE TOGA DETENT THE ACFT SEEMED TO RUN OUT OF 'OOMPH' AND SETTLED TO THE GND AND STRUCK THE TAIL AS IT ROTATED FOR THE BALKED LNDG. AT ABOUT 100 FT THE CAPT DISCONNECTED THE AUTOPLT AND HAND FLEW THE ACFT IN ACCORDANCE WITH ATC INSTRUCTIONS. ATTEMPTS BY COMPANY WERE MADE TO DUPLICATE THIS IN THE SIMULATOR. NOTHING THE COMPANY COULD PROGRAM IN THE SIMULATOR WOULD REPLICATE THIS EVENT.