ERRONEOUS PENETRATION INTO CLASS B AIRSPACE.

Narrative

DURING THE EARLY EVENING OF APR/TUE/95 AT APPROX XA00 PM; I HAD TAKEN OFF FROM COLLEGE PARK ARPT (CGS). IMMEDIATELY AFTER TKOF; I CONTACTED BALTIMORE APCH TO OBTAIN CLRNC THROUGH THE BALTIMORE WASHINGTON ARPT (BWI) CLASS B AIRSPACE. I WAS DENIED. AT THIS POINT I WAS NAVING WITH A PORTABLE GPS OF WHICH I WAS NOT THOROUGHLY FAMILIAR WITH. I THEN REPROGRAMMED THE GPS FROM BWI TO FALLSTON ARPT (W42) AT WHICH POINT MY COURSE WOULD HAVE TAKEN ME W AND UNDER THE BWI CLASS B AIRSPACE. HOWEVER; WITHOUT MY KNOWLEDGE THE GPS RETAINED THE BWI PROGRAM IN MEMORY AND IT WAS THE BWI COURSE THAT I WAS TRACKING AND NOT W42. MINS LATER I OBSERVED A LARGE ARPT APPROX 8 NM N OF MY POS WHILE AT AN ALT OF 1200 FT. AT THIS POINT; I CONTACTED BALTIMORE APCH AND INFORMED THEM THAT I BELIEVED THAT I MAY HAVE INADVERTENTLY ENTERED THEIR AIRSPACE. IN ORDER TO CONFIRM MY POS; I TOLD THE CTLR THAT I WAS OBSERVING A HVY JET IN THE PROCESS OF TAKING OFF. THE CTLR THEN CONFIRMED THAT I WAS IN BWI'S AIRSPACE. HE THEN GAVE ME A HDG THAT WOULD EXIT ME FROM THE AREA AND REQUESTED ME TO CONTACT HIM VIA TELEPHONE WHEN I ARRIVED AT MY DEST ARPT. I COMPLIED. COMMENTS: THIS PROB OBVIOUSLY AROSE BECAUSE OF MY UNFAMILIARITY WITH THE PORTABLE GPS. I WAS UNAWARE THAT IT COULD ACTUALLY RETAIN A PREVIOUSLY PROGRAMMED LOCATION. THE ERROR WAS DISCOVERED WHEN I OBSERVED AN UNFAMILIAR ARPT AND CONFIRMED IT BY VOR. CORRECTIVE ACTION: I IMMEDIATELY CONTACTED APCH WHILE SIMULTANEOUSLY TURNING AWAY FROM THE ARPT AND MAINTAINING A SAFE LOW ALT (1200 FT). THE PURPOSE OF CONTACTING APCH WAS NOT ONLY TO NOTIFY THEM OF MY PRESENCE BUT ALSO TO OBTAIN THE SAFEST RTE OUT OF THE AREA.