CLOSE PROX GA SMA STRAIGHT IN ON A TRAINING FLT AND AN UNK IN THE TFC PATTERN.

Narrative

AFTER AN UNEVENTFUL FLT MY STUDENT MADE RADIO CONTACT WITH THE TWR ABOUT 10 MI E OF THE ARPT. WE WERE AT THIS TIME CLRED FOR A STRAIGHT IN APCH. WE WERE ALSO REQUESTED TO RPT A 2 MI FINAL. OUR CRUISING ALT WAS 4500. SOON AFTER MAKING RADIO CONTACT MY STUDENT SPOTTED THE FIELD AND WE STARTED OUR DSCNT. AS WE WERE PASSING THROUGH 3000 FT APPROX 5 MI FROM THE FIELD AN ACFT PASSED UNDERNEATH OUR ACFT IN CLOSE PROX. THERE WAS NO TIME FOR EVASIVE ACTION. THE TIME IN BTWN SIGHTING THE ACFT AND OUR PASSAGE WAS NO MORE THAN 2-3 SECONDS. IT WOULD APPEAR THAT THE ACFT WAS HIDDEN BY OUR WING AS IT APCHED AND BY THE TIME THE ACFT WAS LARGE ENOUGH TO BE SEEN UNDERNEATH THE WING WE WERE ALREADY CLOSE. SINCE BOTH MY STUDENT AND MYSELF WERE BOTH SCANNING THE LCL APCH ALERT FOR OTHER ACFT THE ONLY OTHER METHOD WE COULD HAVE USED TO SPOT HIM SOONER WOULD HAVE BEEN TO HAVE USED S-TURNS TO GIVE US GREATER VISIBILITY BENEATH OUR ACFT. THE FLT WAS INSTRUCTIONAL IN NATURE SO THE STUDENT WAS FLYING UNDER MY SUPERVISION. THERE WAS TO BE GREAT IMPORTANCE PLACED ON NAV AND COMS. THIS EVENT HOWEVER SHOWED HOW ONE MUST ALWAYS WATCH FOR THE UNEXPECTED. WHILE I DO NOT FEEL THAT WE WERE TOO INVOLVED IN THE COCKPIT THIS EVENT IS A GOOD EXAMPLE OF HOW ONE CAN NEVER SPEND TOO MUCH ATTN TO THE OUTSIDE OF THE ACFT.