Narrative:

While approaching the enw airport from the west, I called the control tower 11 mi out with 'inbound with ATIS, request runway 24L for the south ramp.' the controller responded 'report entering left downwind runway 24L.' I had been monitoring the tower since 20 NM out, and heard a VFR departure off runway 32, as well as at least 2 IFR approachs -- one to runway 24R, and one shortly thereafter to runway 14. I also heard the controller issue instructions for the missed approach procedure to both. A VFR arrival then called from the northwest, and the controller issued traffic information for the departure from runway 32 as well as the inbound aircraft. Immediately following this, I heard an additional practice IFR approach call what I thought was for runway 24L. This led me to mistakenly believe the only traffic in my vicinity was the runway 32 departure that was told to turn to heading 270 degrees, and a cessna I saw high above and in front of me as I was about 7 mi out. I continued to scan for other traffic and saw none. At the 6 mi mark, the controller called me to ask my position and altitude. I responded with 'about 6 mi right off the departure end runway 24R at 2400 ft.' he then asked my intentions. I replied, 'enter left downwind runway 24L, south ramp.' he replied, 'turn south and enter left downwind runway 24L.' I responded, 'turn south, left downwind runway 24L.' as I turned to 180 degrees, I saw a white piper cross right to left, about 150 ft in front of and 50 ft below. I informed the tower my turn south 'almost put me into another aircraft.' he replied, 'I have 5 aircraft in that area and cannot tell the altitude of any of them.' he also stated he thought I'd be at 5 mi 'about 3 mins ago.' I believe my initial call of 11 mi was understood as 7 mi and that I failed to understand where the other aircraft was in relation to me. I should have said 'one-one mi' on my initial call-up, instead of 'eleven mi.' in addition, since the airport was busy, I should not have asked for runway 24L, but instead allowed the controller to direct me. I don't believe I could have seen the piper as it was behind me, to the right. In my understanding of the situation, I pictured that aircraft on the other side of the airport. I should have clarified this with the tower. I also believe that 3 simultaneous practice approachs from 3 different directions is unacceptable from a safety standpoint. As a VFR pilot, I did not understand the position report of the aircraft I nearly collided with due to the reporting procedure used on the instrument approach. Since the entire incident took place just outside the class D airspace, it was my responsibility, as well as the responsibility of the aircraft on the practice approach, to see and avoid one another in cavu conditions.

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Original NASA ASRS Text

Title: NMAC BTWN A C150 AND AN UNKNOWN PIPER ACFT IN THE DOWNWIND AREA TO RWY 24L, 6 NM SW OF ENW.

Narrative: WHILE APCHING THE ENW ARPT FROM THE W, I CALLED THE CTL TWR 11 MI OUT WITH 'INBOUND WITH ATIS, REQUEST RWY 24L FOR THE S RAMP.' THE CTLR RESPONDED 'RPT ENTERING L DOWNWIND RWY 24L.' I HAD BEEN MONITORING THE TWR SINCE 20 NM OUT, AND HEARD A VFR DEP OFF RWY 32, AS WELL AS AT LEAST 2 IFR APCHS -- ONE TO RWY 24R, AND ONE SHORTLY THEREAFTER TO RWY 14. I ALSO HEARD THE CTLR ISSUE INSTRUCTIONS FOR THE MISSED APCH PROC TO BOTH. A VFR ARR THEN CALLED FROM THE NW, AND THE CTLR ISSUED TFC INFO FOR THE DEP FROM RWY 32 AS WELL AS THE INBOUND ACFT. IMMEDIATELY FOLLOWING THIS, I HEARD AN ADDITIONAL PRACTICE IFR APCH CALL WHAT I THOUGHT WAS FOR RWY 24L. THIS LED ME TO MISTAKENLY BELIEVE THE ONLY TFC IN MY VICINITY WAS THE RWY 32 DEP THAT WAS TOLD TO TURN TO HDG 270 DEGS, AND A CESSNA I SAW HIGH ABOVE AND IN FRONT OF ME AS I WAS ABOUT 7 MI OUT. I CONTINUED TO SCAN FOR OTHER TFC AND SAW NONE. AT THE 6 MI MARK, THE CTLR CALLED ME TO ASK MY POS AND ALT. I RESPONDED WITH 'ABOUT 6 MI RIGHT OFF THE DEP END RWY 24R AT 2400 FT.' HE THEN ASKED MY INTENTIONS. I REPLIED, 'ENTER L DOWNWIND RWY 24L, S RAMP.' HE REPLIED, 'TURN S AND ENTER L DOWNWIND RWY 24L.' I RESPONDED, 'TURN S, L DOWNWIND RWY 24L.' AS I TURNED TO 180 DEGS, I SAW A WHITE PIPER CROSS R TO L, ABOUT 150 FT IN FRONT OF AND 50 FT BELOW. I INFORMED THE TWR MY TURN S 'ALMOST PUT ME INTO ANOTHER ACFT.' HE REPLIED, 'I HAVE 5 ACFT IN THAT AREA AND CANNOT TELL THE ALT OF ANY OF THEM.' HE ALSO STATED HE THOUGHT I'D BE AT 5 MI 'ABOUT 3 MINS AGO.' I BELIEVE MY INITIAL CALL OF 11 MI WAS UNDERSTOOD AS 7 MI AND THAT I FAILED TO UNDERSTAND WHERE THE OTHER ACFT WAS IN RELATION TO ME. I SHOULD HAVE SAID 'ONE-ONE MI' ON MY INITIAL CALL-UP, INSTEAD OF 'ELEVEN MI.' IN ADDITION, SINCE THE ARPT WAS BUSY, I SHOULD NOT HAVE ASKED FOR RWY 24L, BUT INSTEAD ALLOWED THE CTLR TO DIRECT ME. I DON'T BELIEVE I COULD HAVE SEEN THE PIPER AS IT WAS BEHIND ME, TO THE R. IN MY UNDERSTANDING OF THE SIT, I PICTURED THAT ACFT ON THE OTHER SIDE OF THE ARPT. I SHOULD HAVE CLARIFIED THIS WITH THE TWR. I ALSO BELIEVE THAT 3 SIMULTANEOUS PRACTICE APCHS FROM 3 DIFFERENT DIRECTIONS IS UNACCEPTABLE FROM A SAFETY STANDPOINT. AS A VFR PLT, I DID NOT UNDERSTAND THE POS RPT OF THE ACFT I NEARLY COLLIDED WITH DUE TO THE RPTING PROC USED ON THE INST APCH. SINCE THE ENTIRE INCIDENT TOOK PLACE JUST OUTSIDE THE CLASS D AIRSPACE, IT WAS MY RESPONSIBILITY, AS WELL AS THE RESPONSIBILITY OF THE ACFT ON THE PRACTICE APCH, TO SEE AND AVOID ONE ANOTHER IN CAVU CONDITIONS.

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.