Narrative:

I was assigned to fly a pvtly owned hawker 1000 as the captain. My first officer and I were scheduled to fly a passenger mission from cmh to den. The flight to den was uneventful, as far as we were aware. However, when I arrived at the hotel I was contacted by company management, who informed me that a 'loss of separation report' implicating our aircraft and a B737 air carrier flight had been filed by den approach control. The incident apparently occurred during the arrival phase of the flight. Our flight plan was into den via the dandd 3 arrival, oathe transition. During the flight, we were cleared direct to brickyard VOR, and later direct to kansas city VOR at FL350. Shortly before turning at sells intersection on the dandd 3 arrival, we were cleared to begin our descent to FL220. During the approach phases of flight, there wre several aircraft on the same frequency, with almost continuous radio xmissions between ATC and various aircraft. On several occasions, we heard ATC step on xmissions from aircraft, or aircraft step on xmissions from ATC. Several xmissions had to be made a second time, which further jammed the frequency. This situation persisted on each frequency during the arrival, approach and landing. In the descent to FL220, established inbound toward pragg intersection on the dandd 3 arrival, we received a frequency change to another arrival controller, who immediately cleared us direct to hugo with a descent to 17000 ft MSL to join the quail 3 arrival. My first officer located the quail 3 arrival approach plate but before he could enter it into the FMS, the same controller revised our clearance again to quail intersection, descend to 14000 ft MSL, slow to 280 KIAS, continue via the quail 3 arrival. We noted that this clearance differed from the published crossing restr of 250 KIAS and expect 17000 ft MSL. My first officer immediately entered the quail 3 arrival in the FMS. He then switched his radio to communication #1 to call the FBO and to make sure that the transportation arrangements were in place. I was monitoring approach control on communication #2 as I turned to proceed direct to quail intersection. ATC inquired again immediately after I began the turn whether we were proceeding direct to quail and I responded that we were turning to a heading of 281 degrees, which was the direct heading to quail intersection. I assumed that ATC either did not hear my first officer's response to the clearance to proceed direct to quail, or perhaps that our transmission had been stepped on. At the time of my response, I had approximately 10 degrees remaining to complete my turn to that heading. We were cleared down to 9000 ft. At no time did ATC indicate to us that there was any actual or potential conflict with other traffic. The only other aircraft which was called out to us when we were about 15 mi out from the runway on the localizer at 9000 ft MSL was a B737 at our 1 O'clock position, 5 or 6 mi distance. We responded that we had the traffic in sight, and ATC cleared us for the visual approach, following that traffic to runway 35L. I felt that the ATC controller was sloppy in handing us off to the tower. By the time we were about 4 mi on final approach, neither my first officer nor I had heard a direction to contact tower. The aircraft ahead of us was turning off the runway by this time, so my first officer called to confirm our clearance to land. ATC directed us to contact the tower, and we received our clearance to land from the tower when we were perhaps 2 mi out on final approach. As the first officer and I discussed later, we realized that ATC might have directed us to the tower earlier, and the transmission could have been stepped on. If this did happen, if ATC did not receive a confirmation from us of a frequency change, the controller should have repeated his transmission. Other than this, I detected nothing unusual about the radio communications between ATC and our aircraft. In retrospect, I believe that safety would have been enhanced if ATC controled fewer aircraft on the same frequency during peak traffic density periods. Of course, this would require more controllers during these periods. Safety would also be enhanced if controllers and pilots would exercise more care to ensure that the frequency was clear prior to initiating a transmission. Finally, it behooves both controllers and pilots to repeat xmissions when there is no apparent response from the intended recipient.

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Original NASA ASRS Text

Title: H25C FLC ADVISED AFTER FLT COMPLETION INTO DEN THAT THEY WERE INVOLVED IN A LOSS OF SEPARATION WITH A B737.

Narrative: I WAS ASSIGNED TO FLY A PVTLY OWNED HAWKER 1000 AS THE CAPT. MY FO AND I WERE SCHEDULED TO FLY A PAX MISSION FROM CMH TO DEN. THE FLT TO DEN WAS UNEVENTFUL, AS FAR AS WE WERE AWARE. HOWEVER, WHEN I ARRIVED AT THE HOTEL I WAS CONTACTED BY COMPANY MGMNT, WHO INFORMED ME THAT A 'LOSS OF SEPARATION RPT' IMPLICATING OUR ACFT AND A B737 ACR FLT HAD BEEN FILED BY DEN APCH CTL. THE INCIDENT APPARENTLY OCCURRED DURING THE ARR PHASE OF THE FLT. OUR FLT PLAN WAS INTO DEN VIA THE DANDD 3 ARR, OATHE TRANSITION. DURING THE FLT, WE WERE CLRED DIRECT TO BRICKYARD VOR, AND LATER DIRECT TO KANSAS CITY VOR AT FL350. SHORTLY BEFORE TURNING AT SELLS INTXN ON THE DANDD 3 ARR, WE WERE CLRED TO BEGIN OUR DSCNT TO FL220. DURING THE APCH PHASES OF FLT, THERE WRE SEVERAL ACFT ON THE SAME FREQ, WITH ALMOST CONTINUOUS RADIO XMISSIONS BTWN ATC AND VARIOUS ACFT. ON SEVERAL OCCASIONS, WE HEARD ATC STEP ON XMISSIONS FROM ACFT, OR ACFT STEP ON XMISSIONS FROM ATC. SEVERAL XMISSIONS HAD TO BE MADE A SECOND TIME, WHICH FURTHER JAMMED THE FREQ. THIS SIT PERSISTED ON EACH FREQ DURING THE ARR, APCH AND LNDG. IN THE DSCNT TO FL220, ESTABLISHED INBOUND TOWARD PRAGG INTXN ON THE DANDD 3 ARR, WE RECEIVED A FREQ CHANGE TO ANOTHER ARR CTLR, WHO IMMEDIATELY CLRED US DIRECT TO HUGO WITH A DSCNT TO 17000 FT MSL TO JOIN THE QUAIL 3 ARR. MY FO LOCATED THE QUAIL 3 ARR APCH PLATE BUT BEFORE HE COULD ENTER IT INTO THE FMS, THE SAME CTLR REVISED OUR CLRNC AGAIN TO QUAIL INTXN, DSND TO 14000 FT MSL, SLOW TO 280 KIAS, CONTINUE VIA THE QUAIL 3 ARR. WE NOTED THAT THIS CLRNC DIFFERED FROM THE PUBLISHED XING RESTR OF 250 KIAS AND EXPECT 17000 FT MSL. MY FO IMMEDIATELY ENTERED THE QUAIL 3 ARR IN THE FMS. HE THEN SWITCHED HIS RADIO TO COM #1 TO CALL THE FBO AND TO MAKE SURE THAT THE TRANSPORTATION ARRANGEMENTS WERE IN PLACE. I WAS MONITORING APCH CTL ON COM #2 AS I TURNED TO PROCEED DIRECT TO QUAIL INTXN. ATC INQUIRED AGAIN IMMEDIATELY AFTER I BEGAN THE TURN WHETHER WE WERE PROCEEDING DIRECT TO QUAIL AND I RESPONDED THAT WE WERE TURNING TO A HDG OF 281 DEGS, WHICH WAS THE DIRECT HDG TO QUAIL INTXN. I ASSUMED THAT ATC EITHER DID NOT HEAR MY FO'S RESPONSE TO THE CLRNC TO PROCEED DIRECT TO QUAIL, OR PERHAPS THAT OUR XMISSION HAD BEEN STEPPED ON. AT THE TIME OF MY RESPONSE, I HAD APPROX 10 DEGS REMAINING TO COMPLETE MY TURN TO THAT HDG. WE WERE CLRED DOWN TO 9000 FT. AT NO TIME DID ATC INDICATE TO US THAT THERE WAS ANY ACTUAL OR POTENTIAL CONFLICT WITH OTHER TFC. THE ONLY OTHER ACFT WHICH WAS CALLED OUT TO US WHEN WE WERE ABOUT 15 MI OUT FROM THE RWY ON THE LOC AT 9000 FT MSL WAS A B737 AT OUR 1 O'CLOCK POS, 5 OR 6 MI DISTANCE. WE RESPONDED THAT WE HAD THE TFC IN SIGHT, AND ATC CLRED US FOR THE VISUAL APCH, FOLLOWING THAT TFC TO RWY 35L. I FELT THAT THE ATC CTLR WAS SLOPPY IN HANDING US OFF TO THE TWR. BY THE TIME WE WERE ABOUT 4 MI ON FINAL APCH, NEITHER MY FO NOR I HAD HEARD A DIRECTION TO CONTACT TWR. THE ACFT AHEAD OF US WAS TURNING OFF THE RWY BY THIS TIME, SO MY FO CALLED TO CONFIRM OUR CLRNC TO LAND. ATC DIRECTED US TO CONTACT THE TWR, AND WE RECEIVED OUR CLRNC TO LAND FROM THE TWR WHEN WE WERE PERHAPS 2 MI OUT ON FINAL APCH. AS THE FO AND I DISCUSSED LATER, WE REALIZED THAT ATC MIGHT HAVE DIRECTED US TO THE TWR EARLIER, AND THE XMISSION COULD HAVE BEEN STEPPED ON. IF THIS DID HAPPEN, IF ATC DID NOT RECEIVE A CONFIRMATION FROM US OF A FREQ CHANGE, THE CTLR SHOULD HAVE REPEATED HIS XMISSION. OTHER THAN THIS, I DETECTED NOTHING UNUSUAL ABOUT THE RADIO COMS BTWN ATC AND OUR ACFT. IN RETROSPECT, I BELIEVE THAT SAFETY WOULD HAVE BEEN ENHANCED IF ATC CTLED FEWER ACFT ON THE SAME FREQ DURING PEAK TFC DENSITY PERIODS. OF COURSE, THIS WOULD REQUIRE MORE CTLRS DURING THESE PERIODS. SAFETY WOULD ALSO BE ENHANCED IF CTLRS AND PLTS WOULD EXERCISE MORE CARE TO ENSURE THAT THE FREQ WAS CLR PRIOR TO INITIATING A XMISSION. FINALLY, IT BEHOOVES BOTH CTLRS AND PLTS TO REPEAT XMISSIONS WHEN THERE IS NO APPARENT RESPONSE FROM THE INTENDED RECIPIENT.

Data retrieved from NASA's ASRS site as of July 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.