Narrative:

The 2 aircraft involved in this incident were both on ZDV frequency and radar idented. Aircraft #1, the parachute jump aircraft, was on a routine jump flight. Aircraft #2 was a private cga light transport, IFR flight plan from fort collins to las. The jump aircraft was VFR. By letter of agreement, center is required to issue advisories to the jump aircraft and also to any IFR aircraft transiting the jump area. The problem arose when aircraft #2 was excessively vectored away from den approach control airspace. Due to traffic, and the near proximity of higher terrain, light transport 2 had to be put on a heading that would take the aircraft just west of the jump area. The main reason for close proximity of these 2 aircraft was the inability of the radar controller to identify conflicting targets. The cause of this was the mode C intruder alert program, brought on line by the FAA, some 6-8 months ago. At the time of closest proximity of these 2 aircraft, the radar controller had no less than 8 different conflicts generated by this model program. Supplemental information from acn 121472: I was quickly approaching the drop zone and hadn't yet given center my 1 min warning. I banked the plane slightly to the left so I could see directly below, and make sure I was flying right toward the target. Just at that instant, light transport 2 passed directly underneath me, heading north, at an altitude that I guessed to be 300-400' below mine.

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Original NASA ASRS Text

Title: CGA LTT CAME IN CLOSE PROX TO AN SMA OPERATING IN AN AUTH JUMP ZONE.

Narrative: THE 2 ACFT INVOLVED IN THIS INCIDENT WERE BOTH ON ZDV FREQ AND RADAR IDENTED. ACFT #1, THE PARACHUTE JUMP ACFT, WAS ON A ROUTINE JUMP FLT. ACFT #2 WAS A PVT CGA LTT, IFR FLT PLAN FROM FORT COLLINS TO LAS. THE JUMP ACFT WAS VFR. BY LETTER OF AGREEMENT, CENTER IS REQUIRED TO ISSUE ADVISORIES TO THE JUMP ACFT AND ALSO TO ANY IFR ACFT TRANSITING THE JUMP AREA. THE PROB AROSE WHEN ACFT #2 WAS EXCESSIVELY VECTORED AWAY FROM DEN APCH CTL AIRSPACE. DUE TO TFC, AND THE NEAR PROX OF HIGHER TERRAIN, LTT 2 HAD TO BE PUT ON A HDG THAT WOULD TAKE THE ACFT JUST W OF THE JUMP AREA. THE MAIN REASON FOR CLOSE PROX OF THESE 2 ACFT WAS THE INABILITY OF THE RADAR CTLR TO IDENT CONFLICTING TARGETS. THE CAUSE OF THIS WAS THE MODE C INTRUDER ALERT PROGRAM, BROUGHT ON LINE BY THE FAA, SOME 6-8 MONTHS AGO. AT THE TIME OF CLOSEST PROX OF THESE 2 ACFT, THE RADAR CTLR HAD NO LESS THAN 8 DIFFERENT CONFLICTS GENERATED BY THIS MODEL PROGRAM. SUPPLEMENTAL INFO FROM ACN 121472: I WAS QUICKLY APCHING THE DROP ZONE AND HADN'T YET GIVEN CENTER MY 1 MIN WARNING. I BANKED THE PLANE SLIGHTLY TO THE LEFT SO I COULD SEE DIRECTLY BELOW, AND MAKE SURE I WAS FLYING RIGHT TOWARD THE TARGET. JUST AT THAT INSTANT, LTT 2 PASSED DIRECTLY UNDERNEATH ME, HDG N, AT AN ALT THAT I GUESSED TO BE 300-400' BELOW MINE.

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.