HARD LNDG IN AN A300 DURING APCH AND LNDG PROC. AUTO LAND IN USE.

Narrative

THE FLT WAS DELAYED IN MIA FOR WX IN ORD. LEAVING MIA WE RECEIVED SEVERAL WX REROUTES. AFTER SEVERAL HOLDS AND RECEIVING ANOTHER REROUTE; WE WERE FORCED TO LAND IN STL FOR FUEL. SPENDING SEVERAL HRS IN STL WE DEPARTED FOR ORD. THE WX IN THE AREA WAS BAD; BUT ACCEPTABLE AT THE ARPT. ORD WAS UTILIZING A CAT 3 RWY AND; EVEN THOUGH IT WAS NOT REQUIRED; I ELECTED TO UTILIZE THE ACFT AUTO LAND FEATURE. I BRIEFED THE FO. I SET UP THE ACFT FOR THIS TYPE APCH; WITH ALL SYS APPARENTLY OPERATING NORMALLY. THE APCH WAS NORMAL DOWN TO BELOW 100 FT WHERE WE EXPERIENCED AN ABRUPT NOSE DOWN. I MANUALLY TOOK CTL; BUT A HARD LNDG RESULTED. I ASSUMED THE AUTOPLT WAS TO BLAME. UPON REFLECTION; I CONSIDERED WE WERE CAUGHT IN A DOWN DRAFT FROM ONE OF THE MANY TSTMS IN THE AREA. WHEN SOMETHING LIKE THIS HAPPENS; YOU HAVE VERY LITTLE TIME TO REACT. I WAS USING THE AUTO LAND FEATURE BECAUSE I THOUGHT IT WOULD BE EASIER AFTER A VERY LONG DAY. IN THE FUTURE; I WILL NOT USE THIS BECAUSE I KNOW MY CAPABILITIES AND DO NOT HAVE TO SECOND GUESS. AT THE END OF A VERY LONG DAY; I RECOMMEND USING WHAT YOU ARE SURE OF; YOUR OWN KNOWLEDGE AND SKILLS.