Narrative:

I departed bjc in VMC, and headed south to apa. After receiving the ATIS about 15 min out, I tuned in the tower frequency, and found it to be extremely busy. Finally, at 9 NM west of the airport, I was able to contact the tower and told them where I was, that I had the ATIS, and that I was landing. I was told to cross mid-field at 7300 ft MSL and enter a left downwind for runway 17L. I was aware of an aircraft approaching the field from the northwest, and another told to enter the pattern downwind from the south. After passing midfield I started to let down and turn left to enter the left pattern for runway 17L. As I entered left downwind, the controller scolded me about letting down too soon, although I was only down 7225 ft MSL by the time I had reached the downwind leg. The controller issued to me instructions for landing, and due to the confusion that ensued, I am not absolutely sure what the instructions were. I may have been told that I was #3, although I do not remember it. I was told to follow an aircraft, which I assumed was an aircraft turning base for runway 17L. Consequently, I followed that aircraft. While turning to final I noticed another aircraft approaching me from the west. Because apa has parallel runways, I assumed it was bound for runway 17R. The aircraft continued to close with my course, so I maintained a close watch on it while setting up for final. The aircraft finally turned to the south at about 300 ft away in horizontal distance and less than 100 ft vertical distance above me. At that point the controller asked if I had turned base yet, and I replied that I was on final. The controller told me to go around, which I did. The aircraft which had been closing on me noted to the controller that he had nearly collided with me, although, as I said, I had visual contact with the aircraft at all times and the distances were substantial, although not acceptable. After re-entering the pattern and landing without incident, I finally had time to reflect on what happened. Because of the business of the frequency, I made assumptions which I should not have made. If I were indeed told I was number 3 to land, I should have absolutely ascertained the location of the 2 aircraft ahead of me. Instead, I simply followed the aircraft ahead of me. Secondly, and in part because of the first assumption, I made another assumption, this one about the aircraft approaching from the west. I should have broken into the frequency and confirmed the situation with the controller before we got too close. I now believe that that aircraft was the #2 aircraft cleared to land, and I absolutely should not have been where I was at that time. I have learned that the busier the airport and the busier the frequency, the more important it becomes to confirm any doubts one may have and not to simply make assumptions. Finally, while none of the following ameliorates my actions, there are some other points that may have exacerbated the situation. I do not believe I violated the altitude restrs placed on me by the controller, or if I did, it was by less than 50 ft. I also believe that since the controller asked me if I had turned base yet when I was already well into final, it is possible that the controller had mistaken another aircraft that was entering the pattern from the south as my aircraft that thought that she had substantial separation. The controller was extremely busy, having problems juggling all the requests, and twice seemed to mistake other aircraft in the pattern.

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Original NASA ASRS Text

Title: PA-32 PLT HAD AN NMAC WITH ANOTHER LIGHT ACFT IN APA CLASS D.

Narrative: I DEPARTED BJC IN VMC, AND HEADED S TO APA. AFTER RECEIVING THE ATIS ABOUT 15 MIN OUT, I TUNED IN THE TWR FREQ, AND FOUND IT TO BE EXTREMELY BUSY. FINALLY, AT 9 NM W OF THE ARPT, I WAS ABLE TO CONTACT THE TWR AND TOLD THEM WHERE I WAS, THAT I HAD THE ATIS, AND THAT I WAS LNDG. I WAS TOLD TO CROSS MID-FIELD AT 7300 FT MSL AND ENTER A L DOWNWIND FOR RWY 17L. I WAS AWARE OF AN ACFT APCHING THE FIELD FROM THE NW, AND ANOTHER TOLD TO ENTER THE PATTERN DOWNWIND FROM THE S. AFTER PASSING MIDFIELD I STARTED TO LET DOWN AND TURN L TO ENTER THE L PATTERN FOR RWY 17L. AS I ENTERED L DOWNWIND, THE CTLR SCOLDED ME ABOUT LETTING DOWN TOO SOON, ALTHOUGH I WAS ONLY DOWN 7225 FT MSL BY THE TIME I HAD REACHED THE DOWNWIND LEG. THE CTLR ISSUED TO ME INSTRUCTIONS FOR LNDG, AND DUE TO THE CONFUSION THAT ENSUED, I AM NOT ABSOLUTELY SURE WHAT THE INSTRUCTIONS WERE. I MAY HAVE BEEN TOLD THAT I WAS #3, ALTHOUGH I DO NOT REMEMBER IT. I WAS TOLD TO FOLLOW AN ACFT, WHICH I ASSUMED WAS AN ACFT TURNING BASE FOR RWY 17L. CONSEQUENTLY, I FOLLOWED THAT ACFT. WHILE TURNING TO FINAL I NOTICED ANOTHER ACFT APCHING ME FROM THE W. BECAUSE APA HAS PARALLEL RWYS, I ASSUMED IT WAS BOUND FOR RWY 17R. THE ACFT CONTINUED TO CLOSE WITH MY COURSE, SO I MAINTAINED A CLOSE WATCH ON IT WHILE SETTING UP FOR FINAL. THE ACFT FINALLY TURNED TO THE S AT ABOUT 300 FT AWAY IN HORIZ DISTANCE AND LESS THAN 100 FT VERT DISTANCE ABOVE ME. AT THAT POINT THE CTLR ASKED IF I HAD TURNED BASE YET, AND I REPLIED THAT I WAS ON FINAL. THE CTLR TOLD ME TO GO AROUND, WHICH I DID. THE ACFT WHICH HAD BEEN CLOSING ON ME NOTED TO THE CTLR THAT HE HAD NEARLY COLLIDED WITH ME, ALTHOUGH, AS I SAID, I HAD VISUAL CONTACT WITH THE ACFT AT ALL TIMES AND THE DISTANCES WERE SUBSTANTIAL, ALTHOUGH NOT ACCEPTABLE. AFTER RE-ENTERING THE PATTERN AND LNDG WITHOUT INCIDENT, I FINALLY HAD TIME TO REFLECT ON WHAT HAPPENED. BECAUSE OF THE BUSINESS OF THE FREQ, I MADE ASSUMPTIONS WHICH I SHOULD NOT HAVE MADE. IF I WERE INDEED TOLD I WAS NUMBER 3 TO LAND, I SHOULD HAVE ABSOLUTELY ASCERTAINED THE LOCATION OF THE 2 ACFT AHEAD OF ME. INSTEAD, I SIMPLY FOLLOWED THE ACFT AHEAD OF ME. SECONDLY, AND IN PART BECAUSE OF THE FIRST ASSUMPTION, I MADE ANOTHER ASSUMPTION, THIS ONE ABOUT THE ACFT APCHING FROM THE W. I SHOULD HAVE BROKEN INTO THE FREQ AND CONFIRMED THE SIT WITH THE CTLR BEFORE WE GOT TOO CLOSE. I NOW BELIEVE THAT THAT ACFT WAS THE #2 ACFT CLRED TO LAND, AND I ABSOLUTELY SHOULD NOT HAVE BEEN WHERE I WAS AT THAT TIME. I HAVE LEARNED THAT THE BUSIER THE ARPT AND THE BUSIER THE FREQ, THE MORE IMPORTANT IT BECOMES TO CONFIRM ANY DOUBTS ONE MAY HAVE AND NOT TO SIMPLY MAKE ASSUMPTIONS. FINALLY, WHILE NONE OF THE FOLLOWING AMELIORATES MY ACTIONS, THERE ARE SOME OTHER POINTS THAT MAY HAVE EXACERBATED THE SIT. I DO NOT BELIEVE I VIOLATED THE ALT RESTRS PLACED ON ME BY THE CTLR, OR IF I DID, IT WAS BY LESS THAN 50 FT. I ALSO BELIEVE THAT SINCE THE CTLR ASKED ME IF I HAD TURNED BASE YET WHEN I WAS ALREADY WELL INTO FINAL, IT IS POSSIBLE THAT THE CTLR HAD MISTAKEN ANOTHER ACFT THAT WAS ENTERING THE PATTERN FROM THE S AS MY ACFT THAT THOUGHT THAT SHE HAD SUBSTANTIAL SEPARATION. THE CTLR WAS EXTREMELY BUSY, HAVING PROBS JUGGLING ALL THE REQUESTS, AND TWICE SEEMED TO MISTAKE OTHER ACFT IN THE PATTERN.

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.