NMAC BTWN A BEECH JET 400A AND AN MU2 AT 1800 FT AGL 5 NM E OF PTK; MI.

Narrative

DEPARTED 7D2 ON A SALES DEMO FLT. ENRTE TO FLINT; MI (FNT). REALIZED THAT WE MAY BE GETTING TOO CLOSE TO PONTIAC'S AIRSPACE (PTK) SO CALLED UP THE AIRSPACE INFO ON THE GARMIN GNS 530 MAP TO SEE IF WE HAD VIOLATED THE CLASS D. GARMIN SHOWED THAT WE WERE RIGHT ON THE EDGE OF THE CLASS D RING; SO I TURNED ABOUT 90 DEGS TO THE R TO DIRECT OUR PLANE AWAY FROM THE AIRSPACE. I FAILED TO SEE THE TFC OFF OUR R; UNTIL HE WAS UNDER US ABOUT 500 FT. I THINK HE MAY HAVE DESCENDED TO AVOID US BUT AM NOT SURE. EVENTS CONTRIBUTING TO POSSIBLE AIRSPACE VIOLATION AND CLOSE PROX TO AIRBORNE TFC INCLUDE -- 1) GPS MAP NOT SET UP TO SHOW AIRSPACE RINGS AT SCALE SELECTED. I AM VERY FAMILIAR WITH THE GARMIN GNS 530 BUT DID NOT REALIZE THIS FEATURE HAD BEEN DE-SELECTED. 2) ABRUPT CHANGE OF DIRECTION TO DEPART THE CLASS D AIRSPACE; OR PREVENT THE ACTUAL INCURSION PUT US IN THE PATH OF OTHER AIRBORNE TFC. I MAY HAVE SCANNED THE AREA MORE THOROUGHLY IF NOT CONCERNED WITH A POTENTIAL AIRSPACE VIOLATION. 3) MU2 CLOSE BY.