2 PLTS IN A C172 FLY THROUGH HFD'S CLASS D AIRSPACE WITHOUT AUTH. THEY DO NOT REALIZE THE PROB UNTIL THEY HEAR HFD TWR ADVISING TFC OF THEIR PRESENCE.

Narrative

WHILE RETURNING TO PLAINVILLE; CT; FROM THE E VIA THE HARTFORD VOR; 15 NM FROM PLAINVILLE; WE POSSIBLY ENTERED HARTFORD'S CLASS D AIRSPACE. AFTER PASSING OVER THE VOR AT 2000 FT WE MADE A ROUGH ESTIMATE OF A HDG BACK TO PLAINVILLE AND CONTINUED. MONITORING HARTFORD TWR; WE HEARD OURSELVES CALLED AS TFC TO 2 ACFT DEPARTING TO THE S. WE THOUGHT WE WERE S OF THE CLASS D; BUT UPON RECOGNITION OF SOME DISTINCTIVE GND FEATURES WE REALIZED WE WERE FARTHER N THAN PREVIOUSLY THOUGHT. BY THIS TIME; HOWEVER; WE WOULD HAVE BEEN CLR OF THE AIRSPACE ANYWAY SO WE MADE NO CORRECTIVE ACTION AND PROCEEDED TO OUR DEST. WITH BOTH A PVT AND A COMMERCIAL PLT IN THE ACFT; SITUATIONAL AWARENESS SHOULD NOT HAVE BEEN LOST. THROUGHOUT THE TRIP; ONE OF US WOULD FLY WHILE THE OTHER NAVED; BUT THIS STOPPED UPON XING THE VOR AS WE RETURNED TO FAMILIAR SURROUNDINGS. WE WERE AWARE OF THE CLASS D AIRSPACE AND DISCUSSED HOW TO AVOID IT; BUT BECAME LAZY WHEN WE APCHED OUR DEST. HAD WE BEEN THE LEAST BIT VIGILANT IN TRACKING OUTBOUND FROM THE VOR; THIS PROB WOULD NOT HAVE OCCURRED. THERE WERE NO TFC CONFLICTS DUE TO OUR MONITORING TWR FREQ AS WELL AS TWR'S SEPARATION SVCS TO THE DEPARTING ACFT.