GA PLT MISUNDERSTANDS CLRNC AND LANDS ON WRONG RWY AT ACK.

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ON JUL/XX/99 I FLEW MY BONANZA FROM POU TO ACK. IT HAPPENS THAT THOSE 2 ARPTS HAVE RWY PATTERNS IDENTICAL TO EACH OTHER -- A RWY 6 AND A RWY 33 WITH THE IDENTICAL LAYOUTS; XING EACH OTHER. ACK RWYS ARE A LITTLE LONGER THAN THOSE AT POU. TFC WAS EXTREMELY HVY AT ACK; WITH THE TWR OPERATOR HAVING A HARD TIME; TALKING MACHINE-GUN FAST. LIKEWISE THE PLTS WERE INTERFERING WITH EACH OTHER; PANDEMONIUM ON THE RADIO. BOTH OF THE XING RWYS WERE IN USE. IT WAS VERY DIFFICULT TO UNDERSTAND THE TWR OPERATOR; HE HAD TO TALK SO EXTREMELY FAST; WITH PLTS TALKING TOO. LNDGS WERE BEING MADE ON RWY 33 AND I UNDERSTOOD THAT I WAS TO LAND ON RWY 6 WITH A SHORT APCH (OVER THE WATER FROM THE W). AS I APCHED FOR THE LNDG; I NOTICED A TWIN WAITING FOR TKOF; PASSED IT LAND LANDED. JUST AS I WAS TOUCHING DOWN I SAW 2 LIGHT PLANES ABORTING TKOFS; ONE BEHIND THE OTHER OVER ME; IN THE OPPOSITE DIRECTION. I TURNED OFF IN LESS THAN 1/2 OF THE RWY. EVIDENTLY; THE 2 LIGHT PLANES HAD BEEN CLRED TO TAKE OFF ON RWY 24; ONE BEHIND THE OTHER IN RAPID SUCCESSION; DUE TO THE HVY TFC. THEY PASSED; TURNING TO THE SIDE; A FEW HUNDRED FT ABOVE ME. AFTER LNDG; I IMMEDIATELY CALLED THE TWR AND APOLOGIZED FOR MY MISTAKE. I KNEW THAT MANY LNDGS WERE BEING MADE ON RWY 33 BUT FOR SOME REASON I THOUGHT I WAS TO LAND ON RWY 6; WHICH SEEMED REASONABLE WITH THE HVY TFC. WHEN TOLD TO MAKE A SHORT APCH I DID SO; ASSUMING THAT THE SHORT APCH WAS TO AVOID XING RWY 33. I HAD TAKEN OFF AT POU ON RWY 6; ON WHICH I HAD MADE HUNDREDS OF TKOFS AND LNDGS; AND POSSIBLY HAD A MIND SET ON RWY 6 FOR THE LNDG AT ACK. I THOUGHT THAT I HEARD 'LAND ON RWY 6;' BUT IT MAY HAVE BEEN THE LAST OF A SENTENCE; 'DO NOT LAND ON RWY 6;' WITH THE FIRST PART OBSCURED BY INTERFERENCE. THE LIGHT WIND FAVORED RWY 6 AND THE WAITING TWIN WAS NATURAL-LOOKING TO ME. THE 'MAKE SHORT APCH' WAS NATURAL DUE TO TFC ON RWY 33. I EVEN ANNOUNCED 'LNDG ON 6' BUT POSSIBLY; EVEN MOST LIKELY; I WAS WASHED OUT BY INTERFERENCE. MY PROFUSE APOLOGY WAS GRACIOUSLY ACCEPTED BY THE TWR OPERATOR WHO SAID THAT I WAS NOT THE ONLY ONE TO MAKE A MISTAKE. HE SAID THAT HE APPRECIATED MY APOLOGY. THIS INCIDENT IS THE FIRST OF ITS KIND MADE BY ME IN MANY YRS OF FLYING AND I WAS DEEPLY DISTURBED BY IT. IT DOES EMPHASIZE THE IMPORTANCE OF GETTING TWR CLRNCS CLR IN UNUSUAL CONFUSION; EVEN IF IT IS NECESSARY TO GO AROUND THE PATTERN AN EXTRA TIME TO GET THEM STRAIGHT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR DESCRIBED THE TFC IN THE ACK AREA ON THE DAY IN QUESTION AS 'MAYHEM;' BOTH IN THE AIR AND ON THE RADIO FREQS. HE REITERATED THE FACT THAT EVERYTHING HE HEARD AND SAW LED HIM TO BELIEVE THAT HE HAD BEEN CLRED TO LAND ON RWY 6. THE DEPS ON RWY 24 THAT FLEW OVER HIM WERE QUITE A SHOCK. NEEDLESS TO SAY; HE WAS EMBARRASSED AND HUMBLED BY THE EXPERIENCE.