A PVT PLT FLYING A MOONEY M20C FAILED TO SET HIS ALTIMETER CORRECTLY RESULTING IN INADVERTENT CLB INTO N90 CLASS B AIRSPACE.

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I TOOK OF FROM CDW RWY 27 AND DEPARTED TO THE N. THIS WAS MY FIRST SOLO FLT IN MY NEW AIRPLANE. I HAD RECEIVED 10 HRS DUAL IN THE AIRPLANE OVER THE PREVIOUS 2 WKS. I LEVELED OFF AT 2800 FT MSL; AND WENT THROUGH MY POST TKOF/CRUISE CHKS. DURING THE CHK; I FOUND THAT PRIOR TO TKOF I HAD WRONGLY SET MY ALTIMETER (ALTHOUGH I HAD RECORDED IT CORRECTLY ON MY KNEE PAD). I IMMEDIATELY MADE A RAPID DSCNT; WHILE RECHKING CALDWELL'S ATIS AND SETTING THE ALTIMETER TO THE CORRECT VALUE. I WAS; HOWEVER; AT LEAST 2 MI WITHIN THE EDGE OF THE NEW YORK CLASS B AIRSPACE; AND THE ALTIMETER ERROR WOULD HAVE PUT MY REAL ALT AT ABOVE THE 3000 FT MSL FLOOR OF THE CLASS B AT THIS POINT. I WAS RATHER NERVOUS TO BE FLYING MY NEW AIRPLANE FOR THE FIRST TIME. I MADE THE SETTING ERROR AFTER LISTENING TO THE ATIS; BEFORE TAXIING; AND DIDN'T CATCH THE ERROR WITH MY PRE TKOF CHKLIST. THE ATMOSPHERIC PRESSURE WAS PARTICULARLY HIGH THAT MORNING; AND I TOOK OFF WITH MY ALTIMETER SET TO 29.XX RATHER THAN 30.XX. WHILE CLBING; I HAD WONDERED THAT IT TOOK A LITTLE LONGER THAN I EXPECTED TO CLB TO MY 2800 FT CRUISE ALT; BUT AS I WAS RELATIVELY UNFAMILIAR WITH THE AIRPLANE; I DID NOT PICK THIS UP AS AN ERROR UNTIL I WENT THROUGH MY CRUISE CHKS.