Narrative:

Aircraft was being vectored for lndgs in the pit approach airspace. Mdt X was being vectored southwest so it could be descended below another aircraft at 7000'. It was vacation 11000' descending to 5000'. An medium large transport Y inbound to pit was cleared to 10000' on a northeast heading of 060 degrees. Communications was not established with the medium large transport Y to stop his descent. Target and data block overlap made it difficult to see the altitude of the mdt X descending to 5000'. Where communication was established with the medium large transport Y, he was turned to a heading of 090 degrees and the other aircraft was turned right to a heading of 360 degrees to try and establish sep. The 2 aircraft passed about 4 mi apart horizontal and about 300' vertical. At the time there was training in progress and the traffic was heavy and complex. Callback conversation with reporter revealed the following: incident took place approximately 35 southeast pit just prior to handoff to pit approach control. Traffic advisory was given both aircraft, but no sightings were reported. Trnee has about 2 yrs in FAA and 15 hours on this radar position. Traffic was moderate to heavy and very complex.

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Original NASA ASRS Text

Title: MDT DSNDED THROUGH ALT OF MLG WITH LESS THAN STANDARD SEPARATION. TRAINING IN PROGRESS CTLR AND DATA BLOCK OVERLAP.

Narrative: ACFT WAS BEING VECTORED FOR LNDGS IN THE PIT APCH AIRSPACE. MDT X WAS BEING VECTORED SW SO IT COULD BE DSNDED BELOW ANOTHER ACFT AT 7000'. IT WAS VACATION 11000' DSNDING TO 5000'. AN MLG Y INBND TO PIT WAS CLRED TO 10000' ON A NE HDG OF 060 DEGS. COMS WAS NOT ESTABLISHED WITH THE MLG Y TO STOP HIS DSCNT. TARGET AND DATA BLOCK OVERLAP MADE IT DIFFICULT TO SEE THE ALT OF THE MDT X DSNDING TO 5000'. WHERE COM WAS ESTABLISHED WITH THE MLG Y, HE WAS TURNED TO A HDG OF 090 DEGS AND THE OTHER ACFT WAS TURNED RIGHT TO A HDG OF 360 DEGS TO TRY AND ESTABLISH SEP. THE 2 ACFT PASSED ABOUT 4 MI APART HORIZ AND ABOUT 300' VERT. AT THE TIME THERE WAS TRNING IN PROGRESS AND THE TFC WAS HEAVY AND COMPLEX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: INCIDENT TOOK PLACE APPROX 35 SE PIT JUST PRIOR TO HDOF TO PIT APCH CTL. TFC ADVISORY WAS GIVEN BOTH ACFT, BUT NO SIGHTINGS WERE RPTED. TRNEE HAS ABOUT 2 YRS IN FAA AND 15 HRS ON THIS RADAR POS. TFC WAS MODERATE TO HVY AND VERY COMPLEX.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.