Narrative:

First landing with this aircraft: I landed in ZZZ1 using managed speed and autothrust. I noted that the aircraft seemed to suddenly 'pay off early' in the flare to landing. I pulled back a little more on the stick to avert a hard landing; resulting in a slightly higher than normal touchdown attitude and a slightly firmer than normal touchdown. I wouldn't have pulled back any more for fear of a tail strike. I remarked to the first officer that the hot day and the light; but highly variable winds; or perhaps the aircraft loading; must have contributed somehow to the early payoff. Second landing with this aircraft: the first officer's landing in ZZZ2. I recommended to him during the approach briefing to be alert for an 'early payoff;' just in case. He flew a textbook approach; pulled the power off for touchdown and the aircraft just fell out from under us. I don't believe that the touchdown was quite hard enough to require a mechanical inspection; but it was pretty close. I called maintenance control and outlined the situation; stating that I wasn't certain whether it was pilot technique or some unknown problem with the aircraft. I did state that if it appeared to me that the aircraft was misbehaving in any way on our next approach; then I would enter some type of hard write-up in the aircraft logbook using our best observations. Third landing with this aircraft: my landing back in ZZZ1. I noted that the 'box' speeds were: vapp=131 and vls=126; which seemed reasonable. I noted that the pfd speeds on both sides were: vapp=131 and vls (top of 'fishhook')=129. I flew the landing using selected speed about 135 and manual thrust. This landing appeared normal. I entered a hard write-up in the aircraft logbook outlining our observations. Flight crew identify/narrative: the aircraft 'paid off early' twice in a row with 2 different pilots at 2 different airports caused us to devote an extra amount of attention to possible reasons. A possible reason was uncovered; with additional technical work necessary to verify. Consulted with maintenance; overrode automation on next landing; and entered hard write-up in aircraft logbook. There appears to be a technical malfunction of unknown origin. Callback conversation with reporter revealed the following information: reporter stated that several days after this event the aircraft was still in service but maintenance continued searching for possible causes. The best theory about the cause was a computer error generated by an angle of attack vane rigging error. The airbus landing speed calculations are produced in two different computers and in a no wind condition a 5 knot difference is calculated between the approach speed and the landing speed. If the angle of attack vane is mis-rigged; the aircraft is heavier than displayed or a computer error is made the same speed calculation error can occur with the end result being the 'bottom dropping out' during the landing flare.

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Original NASA ASRS Text

Title: AN A319 HARD LANDING OCCURRED AFTER THE ACFT DROPPED DURING AN APPARENTLY NORMAL LNDG FLARE. APCH AND LNDG SPDS WERE OBSERVED.

Narrative: FIRST LNDG WITH THIS ACFT: I LANDED IN ZZZ1 USING MANAGED SPD AND AUTOTHRUST. I NOTED THAT THE ACFT SEEMED TO SUDDENLY 'PAY OFF EARLY' IN THE FLARE TO LNDG. I PULLED BACK A LITTLE MORE ON THE STICK TO AVERT A HARD LNDG; RESULTING IN A SLIGHTLY HIGHER THAN NORMAL TOUCHDOWN ATTITUDE AND A SLIGHTLY FIRMER THAN NORMAL TOUCHDOWN. I WOULDN'T HAVE PULLED BACK ANY MORE FOR FEAR OF A TAIL STRIKE. I REMARKED TO THE FO THAT THE HOT DAY AND THE LIGHT; BUT HIGHLY VARIABLE WINDS; OR PERHAPS THE ACFT LOADING; MUST HAVE CONTRIBUTED SOMEHOW TO THE EARLY PAYOFF. SECOND LNDG WITH THIS ACFT: THE FO'S LNDG IN ZZZ2. I RECOMMENDED TO HIM DURING THE APCH BRIEFING TO BE ALERT FOR AN 'EARLY PAYOFF;' JUST IN CASE. HE FLEW A TEXTBOOK APCH; PULLED THE PWR OFF FOR TOUCHDOWN AND THE ACFT JUST FELL OUT FROM UNDER US. I DON'T BELIEVE THAT THE TOUCHDOWN WAS QUITE HARD ENOUGH TO REQUIRE A MECHANICAL INSPECTION; BUT IT WAS PRETTY CLOSE. I CALLED MAINT CTL AND OUTLINED THE SITUATION; STATING THAT I WASN'T CERTAIN WHETHER IT WAS PLT TECHNIQUE OR SOME UNKNOWN PROB WITH THE ACFT. I DID STATE THAT IF IT APPEARED TO ME THAT THE ACFT WAS MISBEHAVING IN ANY WAY ON OUR NEXT APCH; THEN I WOULD ENTER SOME TYPE OF HARD WRITE-UP IN THE ACFT LOGBOOK USING OUR BEST OBSERVATIONS. THIRD LNDG WITH THIS ACFT: MY LNDG BACK IN ZZZ1. I NOTED THAT THE 'BOX' SPDS WERE: VAPP=131 AND VLS=126; WHICH SEEMED REASONABLE. I NOTED THAT THE PFD SPDS ON BOTH SIDES WERE: VAPP=131 AND VLS (TOP OF 'FISHHOOK')=129. I FLEW THE LNDG USING SELECTED SPD ABOUT 135 AND MANUAL THRUST. THIS LNDG APPEARED NORMAL. I ENTERED A HARD WRITE-UP IN THE ACFT LOGBOOK OUTLINING OUR OBSERVATIONS. FLT CREW IDENT/NARRATIVE: THE ACFT 'PAID OFF EARLY' TWICE IN A ROW WITH 2 DIFFERENT PLTS AT 2 DIFFERENT ARPTS CAUSED US TO DEVOTE AN EXTRA AMOUNT OF ATTN TO POSSIBLE REASONS. A POSSIBLE REASON WAS UNCOVERED; WITH ADDITIONAL TECHNICAL WORK NECESSARY TO VERIFY. CONSULTED WITH MAINT; OVERRODE AUTOMATION ON NEXT LNDG; AND ENTERED HARD WRITE-UP IN ACFT LOGBOOK. THERE APPEARS TO BE A TECHNICAL MALFUNCTION OF UNKNOWN ORIGIN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THAT SEVERAL DAYS AFTER THIS EVENT THE AIRCRAFT WAS STILL IN SERVICE BUT MAINTENANCE CONTINUED SEARCHING FOR POSSIBLE CAUSES. THE BEST THEORY ABOUT THE CAUSE WAS A COMPUTER ERROR GENERATED BY AN ANGLE OF ATTACK VANE RIGGING ERROR. THE AIRBUS LNDG SPD CALCULATIONS ARE PRODUCED IN TWO DIFFERENT COMPUTERS AND IN A NO WIND CONDITION A 5 KNOT DIFFERENCE IS CALCULATED BETWEEN THE APCH SPD AND THE LANDING SPD. IF THE ANGLE OF ATTACK VANE IS MIS-RIGGED; THE ACFT IS HEAVIER THAN DISPLAYED OR A COMPUTER ERROR IS MADE THE SAME SPD CALCULATION ERROR CAN OCCUR WITH THE END RESULT BEING THE 'BOTTOM DROPPING OUT' DURING THE LANDING FLARE.

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.