Narrative:

We were climbing wbound on J60 from den to aspen. Approximately 20 mi west of den, climbing through approximately 15500' on our way to FL200, IFR under departure control for stapleton airport, we came within 100', and probably much less, of colliding with a VFR small aircraft. The aircraft came at us from out left side at a 90 degree angle to our flight path. We were in VFR conditions, but in spite of careful observation, never saw the aircraft until he was within 100' and converging. The small aircraft was in level flight and not in contact with any controling body. He evidently saw us at the last moment and swerved behind us passing very close, possibly less than 100'. I called departure control and they advised me they, in fact, did have a VFR target at our location. No advisory was issued. We should have collided except for pure luck. Both aircraft were legal to be in that airspace. We were IFR, he was in uncontrolled VFR. It would seem 15500' and uncontrolled within 20 mi of the fifth busiest airport is asking for a midair. The airspace is much too unrestricted.

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Original NASA ASRS Text

Title: ACR-MDT AND AN SMA HAVE NMAC.

Narrative: WE WERE CLBING WBOUND ON J60 FROM DEN TO ASPEN. APPROX 20 MI W OF DEN, CLBING THROUGH APPROX 15500' ON OUR WAY TO FL200, IFR UNDER DEP CTL FOR STAPLETON ARPT, WE CAME WITHIN 100', AND PROBABLY MUCH LESS, OF COLLIDING WITH A VFR SMA. THE ACFT CAME AT US FROM OUT LEFT SIDE AT A 90 DEG ANGLE TO OUR FLT PATH. WE WERE IN VFR CONDITIONS, BUT IN SPITE OF CAREFUL OBSERVATION, NEVER SAW THE ACFT UNTIL HE WAS WITHIN 100' AND CONVERGING. THE SMA WAS IN LEVEL FLT AND NOT IN CONTACT WITH ANY CTLING BODY. HE EVIDENTLY SAW US AT THE LAST MOMENT AND SWERVED BEHIND US PASSING VERY CLOSE, POSSIBLY LESS THAN 100'. I CALLED DEP CTL AND THEY ADVISED ME THEY, IN FACT, DID HAVE A VFR TARGET AT OUR LOCATION. NO ADVISORY WAS ISSUED. WE SHOULD HAVE COLLIDED EXCEPT FOR PURE LUCK. BOTH ACFT WERE LEGAL TO BE IN THAT AIRSPACE. WE WERE IFR, HE WAS IN UNCTLED VFR. IT WOULD SEEM 15500' AND UNCTLED WITHIN 20 MI OF THE FIFTH BUSIEST ARPT IS ASKING FOR A MIDAIR. THE AIRSPACE IS MUCH TOO UNRESTRICTED.

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.