Narrative:

On mar/mon/01, I was in cruise flight southeast of sdf. The ATC controller instructed me to remain east of the runway 35L centerline at sdf. The controller announced incoming traffic to sdf for runway 35L and asked if I had the traffic in sight. I stated I did not have traffic and that I was searching. The controller instructed me to remain east of the runway 35L arrival path until I had the inbound traffic in sight. I also thought her instructions were that once I had the traffic in sight to pass behind the traffic and continue across the runway 35L extended centerline as I continued swbound out of class C airspace. I established contact with the arriving B737. I turned right to pass behind the B737 and began to cross the runway 35L extended centerline at sdf. ATC announced for me to turn immediately to the east, to get back on the east side of the runway 35L extended centerline. I then stated to ATC that I had visual contact with the B737, and I thought I was instructed to pass behind the traffic as I continued swbound out of the class C airspace. ATC said my instructions were to remain east of the runway 35L extended centerline and that I was not given instructions to pass behind the B737 or cross the extended centerline of runway 35L. I apologized to ATC and stated that I must have misunderstood her instructions. She stated that was ok and I cleared the class C airspace to the southwest. The distance from the B737 as it turned from base to final was about 1 1/2 mi from my position. Contributing factors: 1) miscoms. 2) complacency/repetition, the instruction to maintain separation and pass behind traffic is a radio call I hear on a daily basis. ATC may not have given me these instructions but after hearing it over and over, I may have thought I heard these instructions. Corrective actions: 1) ATC made the corrective action. I thought I was in the right, ATC thought there was a chance of a midair collision and instructed me to turn away from the incoming traffic.

Related reports:

Google
 

Original NASA ASRS Text

Title: A POSSIBLE UNCLR XMISSION TO A HELI PLT BY SDF LCL CTLR WAS CONSTRUED AS AN INSTRUCTION.

Narrative: ON MAR/MON/01, I WAS IN CRUISE FLT SE OF SDF. THE ATC CTLR INSTRUCTED ME TO REMAIN E OF THE RWY 35L CTRLINE AT SDF. THE CTLR ANNOUNCED INCOMING TFC TO SDF FOR RWY 35L AND ASKED IF I HAD THE TFC IN SIGHT. I STATED I DID NOT HAVE TFC AND THAT I WAS SEARCHING. THE CTLR INSTRUCTED ME TO REMAIN E OF THE RWY 35L ARR PATH UNTIL I HAD THE INBOUND TFC IN SIGHT. I ALSO THOUGHT HER INSTRUCTIONS WERE THAT ONCE I HAD THE TFC IN SIGHT TO PASS BEHIND THE TFC AND CONTINUE ACROSS THE RWY 35L EXTENDED CTRLINE AS I CONTINUED SWBOUND OUT OF CLASS C AIRSPACE. I ESTABLISHED CONTACT WITH THE ARRIVING B737. I TURNED R TO PASS BEHIND THE B737 AND BEGAN TO CROSS THE RWY 35L EXTENDED CTRLINE AT SDF. ATC ANNOUNCED FOR ME TO TURN IMMEDIATELY TO THE E, TO GET BACK ON THE E SIDE OF THE RWY 35L EXTENDED CTRLINE. I THEN STATED TO ATC THAT I HAD VISUAL CONTACT WITH THE B737, AND I THOUGHT I WAS INSTRUCTED TO PASS BEHIND THE TFC AS I CONTINUED SWBOUND OUT OF THE CLASS C AIRSPACE. ATC SAID MY INSTRUCTIONS WERE TO REMAIN E OF THE RWY 35L EXTENDED CTRLINE AND THAT I WAS NOT GIVEN INSTRUCTIONS TO PASS BEHIND THE B737 OR CROSS THE EXTENDED CTRLINE OF RWY 35L. I APOLOGIZED TO ATC AND STATED THAT I MUST HAVE MISUNDERSTOOD HER INSTRUCTIONS. SHE STATED THAT WAS OK AND I CLRED THE CLASS C AIRSPACE TO THE SW. THE DISTANCE FROM THE B737 AS IT TURNED FROM BASE TO FINAL WAS ABOUT 1 1/2 MI FROM MY POS. CONTRIBUTING FACTORS: 1) MISCOMS. 2) COMPLACENCY/REPETITION, THE INSTRUCTION TO MAINTAIN SEPARATION AND PASS BEHIND TFC IS A RADIO CALL I HEAR ON A DAILY BASIS. ATC MAY NOT HAVE GIVEN ME THESE INSTRUCTIONS BUT AFTER HEARING IT OVER AND OVER, I MAY HAVE THOUGHT I HEARD THESE INSTRUCTIONS. CORRECTIVE ACTIONS: 1) ATC MADE THE CORRECTIVE ACTION. I THOUGHT I WAS IN THE RIGHT, ATC THOUGHT THERE WAS A CHANCE OF A MIDAIR COLLISION AND INSTRUCTED ME TO TURN AWAY FROM THE INCOMING TFC.

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.