POSSIBLE INADVERTENT ENTRY INTO CLASS 'D' AIRSPACE.

Narrative

I WAS DIVERTED BY MY DISPATCHER TO XXX. MY HOME BASE IS ZZZ AND I WAS UNFAMILIAR WITH THE RTE TO XXX. THEN I WAS DIVERTED TO AN EMER SCENE. MY GPS HAD ME OVER YYY ARPT. I MADE A CALL ON UNICOM. THEN 'KAAA' APPEARED WITHIN THE 10 NM RING ON MY RADAR. I TURNED AWAY FROM KAAA; CHANGED THE RADIO; AND CONTACTED KAAA TWR FOR PERMISSION THROUGH THE CLASS 'D' AIRSPACE. HE GRANTED ME PERMISSION AND SAID HE; 'HAD ME IN SIGHT.' I CHANGED THE DISTANCE OF THE RINGS ON THE RADAR AND I WAS ON THE EDGE OF 5 NM BUT FLYING AWAY. I MAY HAVE ENTERED THE AIRSPACE BEFORE RECEIVING PERMISSION. I HAVE ABOUT 10 HRS EXPERIENCE WITH THIS GPS AND RADAR. I DO NOT KNOW WHY KAAA DID NOT INITIALLY APPEAR WHEN I REQUESTED THE 10 CLOSEST ARPTS. THE 'KAAA' MIGHT HAVE BEEN OBSCURED BY GND CLUTTER OR WX ON THE RADAR. ORIENTATION CAN BE DIFFICULT ON EMS FLTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE BK-117 IN MEDEVAC OPS. HE HAS NOT HEARD FORM THE FAA ON THIS INCIDENT. AIR TFC IN HIS AREA OF OPS IS 'VERY GOOD TO HIM.' HIS OP USES A DISCREET SQUAWK SO THAT EMS HELIS ARE READILY IDENTIFIABLE. THE RPTR ADMITS THAT THE GPS NAV PROB WAS 'OPERATOR ERROR' ONLY.