NMAC. ACFT ORBITING ARPT UNDER TWR CTL ALMOST HAD MIDAIR BECAUSE TFC NOT RPTED BY TWR.

Narrative

ON MAR/FRI/95 AT APPROX XA00 LCL; THE FOLLOWING SIT TOOK PLACE: I HAD BEEN ORBITING THE FIELD AT DUPAGE COUNTY ARPT; W CHICAGO; IL FOR 40 MINS AT 2500 FT MSL HAVING RECEIVED APPROVAL TO DO SO FROM THE TWR AND HAVING RECEIVED A SQUAWK CODE. DURING THAT 40 MINS PERIOD I WAS GIVEN SEVERAL TA'S AND HEARD THE TWR ADVISE SEVERAL OTHER PLANES OF MY POS. AT ABOUT XB00 PM LCL AS I WAS MOVING FROM E TO W; APPROX 1 MI N OF THE TWR (I WAS CIRCLING WITH L TURNS) I DROPPED THE R WING SLIGHTLY AND SAW A WINDOW FULL OF BLUE AND WHITE HIGHWING SINGLE ENG ACFT. I IMMEDIATELY PUSHED THE YOKE FORWARD FEELING THERE WAS NO WAY WE WOULD NOT COLLIDE. I LEVELED AT 2000 FT MSL AND TURNED ENOUGH TO SEE THE AFOREMENTIONED PLANE PROCEEDING SE. THE PLT OF THAT PLANE CALLED THE TWR AND RPTED NEARLY HITTING 'A LOW WING PLANE.' THE TWR RESPONDED THEY HAD BEEN TRYING TO CONTACT HIM WITH A TA AND THAT HE HAD NOT REPLIED. HE MADE NO FURTHER COMMENT. I MADE NO COMMENT TO THE TWR AT THIS TIME. HOWEVER; I DO NOT RECALL HEARING THEM ATTEMPTING TO CONTACT ANYONE WHO DID NOT RESPOND IMMEDIATELY PRECEDING THIS OCCURRENCE; AND I KNOW THEY DID NOT ATTEMPT TO ADVISE ME OF THE APCHING TFC. I CONTINUED TO CIRCLE FOR ANOTHER 20 MINS BEFORE LNDG. MY PURPOSE FOR THIS FLT WAS TO BREAK IN CYLINDERS AFTER A TOP OVERHAUL -- WHICH IS THE REASON I REMAINED IN THE VICINITY OF THE ARPT FOR AN EXTENDED PERIOD OF TIME.