WHILE APCHING LOU FOR LNDG; PA28 INSTRUCTOR FLT IS INVOLVED WITH AN NMAC WITH AN AEST WHILE FLYING BELOW SDF CLASS C AIRSPACE.

Narrative

ACFT I WAS RETURNING FROM A TRAINING FLT AT NVY TO LOU. 2 PEOPLE WERE ON BOARD ACFT; THE L SEAT WAS OCCUPIED BY A STUDENT PLT WHO WAS FLYING THE AIRPLANE AND THE R SEAT WAS OCCUPIED BY A CFI. ACFT #1 WAS PROCEEDING TOWARDS BOWMAN FIELD AT AN ALT OF 1600 FT AND A HDG OF 150 DEGS. THE STUDENT PLT WAS IN THE PROCESS OF OBTAINING THE LCL ATIS AT BOWMAN FIELD; WHILE THE INSTRUCTOR WAS SCANNING THE HORIZON FOR OTHER TFC. AT APPROX 6 NM N OF BOWMAN FIELD THE INSTRUCTOR NOTICED ACFT #2 AT THE 10 O'CLOCK POS AND AN APPROX 50 FT LOWER ALT; MOVING AT A VERY FAST PACE TOWARDS ACFT #1. TIME WAS NOT AVAILABLE FOR EVASIVE ACTION TO BE TAKEN AND ACFT #2 PROCEEDED RIGHT UNDERNEATH ACFT #1 WITH NO HORIZ AND 50 FT VERT MISS DISTANCE BTWN THE 2 ACFT. AS ACFT #2 PROCEEDED AWAY TO THE W; IT WAS IDENTED AS AN AEROSTAR (VERY DARK COLORS ON WHITE). ACFT #2 DID NOT CLB AND SEEMED TO PROCEED EDGING AROUND LOUISVILLE INTL CLASS C'S INNER CIRCLE; JUST N OF SDF. IMMEDIATELY AFTER THE INCIDENT; THE FLT INSTRUCTOR OF ACFT #1 TOOK CTL OF THE AIRPLANE AND STARTED TURNING AWAY FROM LOUISVILLE BOWMAN FIELD'S CLASS D AIRSPACE; WHILE CONTACTING LOUISVILLE APCH TO RPT THE INCIDENT. THE APCH CTLR MENTIONED THAT ACFT #2 WAS NOT IN CONTACT WITH ATC AND THAT HE HAD A VFR ACFT ON THE RADAR RAPIDLY MOVING AWAY FROM THE VICINITY OF ACFT #1 LOCATION AND HAVING AN ALT OF 1500 FT AND 190 KTS ON THE AIRSPD; WITH A W HDG. THE CTLR ASKED THE FLT INSTRUCTOR OF ACFT #1 IF HE WANTED TO FILE THE INCIDENT AND FURTHER ON PROVIDED A TELEPHONE NUMBER IN ORDER TO RPT THE INCIDENT.