Narrative:

After departing and contacting denver departure; we were immediately commanded to contact denver departure on 126.1 MHZ before leveling at 8000 ft MSL. There were numerous VFR targets north of bjc -- most leveling at 7500 ft MSL beneath the class B airspace. WX was essentially clear; a beautiful summer day in denver. Den departure on 126.1 was very busy with traffic congestion; but after his calls to several other VFR and IFR aircraft he called us saying; 'aircraft X radar contact; maintain 8000.' at that time I mentioned to my co-captain my surprise that he hadn't cleared us to a higher altitude because of the indicated congestion on our TCAS display and no aircraft immediately above. I maintained 200 KTS in level flight at 8000 ft and began slowing further to what I planned to be 180 KTS due to the obvious closure of the several VFR traffic targets ahead. About the same moment I began reducing power; we received our first TCAS traffic alert and shortly thereafter den departure gave us an immediate left turn to 320 degrees from the assigned 360 degrees. Within several seconds our TCASII issued a resolution alert to 'descend.' following the ivsi 'green arc' smoothly to a 1500 FPM descent rate. The resolution was resolved when we leveled at 7500 ft MSL. Passing directly underneath we never saw the traffic which produced the RA; undoubtedly due to the workload of dealing with the RA and numerous other VFR traffic to the north of the airport. Supplemental information from acn 742828: in my view; this incident was a textbook example of the hazards inherent in mixing high performance IFR traffic with low performance VFR aircraft in busy terminal airspace. I do not blame the controller for what happened. His workload was obviously far beyond a uration level at the time. Our high level of situational awareness and alertness; notwithstanding; we still allowed for an RA. Thank god the TCAS system worked the way it is supposed to. In my view; we would all have been better off if our release from bjc had been delayed until the traffic volume along our projected flight path had decreased. Much better still would be a redesign of local airspace and/or ATC procedures that would allow high performance departures from bjc to climb rapidly to 10000 ft or higher; especially in the case of wbound traffic headed for the high terrain along the front range.

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Original NASA ASRS Text

Title: C560 FLT CREW; OPERATING IN AREA OF HIGH TRAFFIC VOLUME; RECEIVED TCAS RA AND RESPONDED ACCORDINGLY.

Narrative: AFTER DEPARTING AND CONTACTING DENVER DEP; WE WERE IMMEDIATELY COMMANDED TO CONTACT DENVER DEP ON 126.1 MHZ BEFORE LEVELING AT 8000 FT MSL. THERE WERE NUMEROUS VFR TARGETS N OF BJC -- MOST LEVELING AT 7500 FT MSL BENEATH THE CLASS B AIRSPACE. WX WAS ESSENTIALLY CLR; A BEAUTIFUL SUMMER DAY IN DENVER. DEN DEP ON 126.1 WAS VERY BUSY WITH TFC CONGESTION; BUT AFTER HIS CALLS TO SEVERAL OTHER VFR AND IFR ACFT HE CALLED US SAYING; 'ACFT X RADAR CONTACT; MAINTAIN 8000.' AT THAT TIME I MENTIONED TO MY CO-CAPT MY SURPRISE THAT HE HADN'T CLRED US TO A HIGHER ALT BECAUSE OF THE INDICATED CONGESTION ON OUR TCAS DISPLAY AND NO ACFT IMMEDIATELY ABOVE. I MAINTAINED 200 KTS IN LEVEL FLT AT 8000 FT AND BEGAN SLOWING FURTHER TO WHAT I PLANNED TO BE 180 KTS DUE TO THE OBVIOUS CLOSURE OF THE SEVERAL VFR TFC TARGETS AHEAD. ABOUT THE SAME MOMENT I BEGAN REDUCING PWR; WE RECEIVED OUR FIRST TCAS TFC ALERT AND SHORTLY THEREAFTER DEN DEP GAVE US AN IMMEDIATE L TURN TO 320 DEGS FROM THE ASSIGNED 360 DEGS. WITHIN SEVERAL SECONDS OUR TCASII ISSUED A RESOLUTION ALERT TO 'DSND.' FOLLOWING THE IVSI 'GREEN ARC' SMOOTHLY TO A 1500 FPM DSCNT RATE. THE RESOLUTION WAS RESOLVED WHEN WE LEVELED AT 7500 FT MSL. PASSING DIRECTLY UNDERNEATH WE NEVER SAW THE TFC WHICH PRODUCED THE RA; UNDOUBTEDLY DUE TO THE WORKLOAD OF DEALING WITH THE RA AND NUMEROUS OTHER VFR TFC TO THE N OF THE ARPT. SUPPLEMENTAL INFO FROM ACN 742828: IN MY VIEW; THIS INCIDENT WAS A TEXTBOOK EXAMPLE OF THE HAZARDS INHERENT IN MIXING HIGH PERFORMANCE IFR TFC WITH LOW PERFORMANCE VFR ACFT IN BUSY TERMINAL AIRSPACE. I DO NOT BLAME THE CTLR FOR WHAT HAPPENED. HIS WORKLOAD WAS OBVIOUSLY FAR BEYOND A URATION LEVEL AT THE TIME. OUR HIGH LEVEL OF SITUATIONAL AWARENESS AND ALERTNESS; NOTWITHSTANDING; WE STILL ALLOWED FOR AN RA. THANK GOD THE TCAS SYS WORKED THE WAY IT IS SUPPOSED TO. IN MY VIEW; WE WOULD ALL HAVE BEEN BETTER OFF IF OUR RELEASE FROM BJC HAD BEEN DELAYED UNTIL THE TFC VOLUME ALONG OUR PROJECTED FLT PATH HAD DECREASED. MUCH BETTER STILL WOULD BE A REDESIGN OF LCL AIRSPACE AND/OR ATC PROCS THAT WOULD ALLOW HIGH PERFORMANCE DEPS FROM BJC TO CLB RAPIDLY TO 10000 FT OR HIGHER; ESPECIALLY IN THE CASE OF WBOUND TFC HEADED FOR THE HIGH TERRAIN ALONG THE FRONT RANGE.

Data retrieved from NASA's ASRS site as of January 2009 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.