Narrative:

On climbout from runway 31R at bfi I requested a southeast departure. Tower approved my turn southbound; informed me of two helicopters as traffic and two inbound business jets. I made a turn southbound; and proceeded south at 900 ft MSL; and reported all traffic in sight. Tower did not issue me any restriction to remain east of the extended centerline of 31R; and I continued south at 900 ft with the arriving business jet in sight. While crossing under the extended centerline at 900 feet; I apparently activated the TCAS on a business jet on final for 31L. I had the aircraft in sight at all times; and believed that I maintained adequate visual separation from [him]. Upon landing; tower informed me of a possible pilot deviation; and that the tower had instructed me not to cross the extended centerline of 31L.upon listening to the liveatc audio archives for my flight; it appears that tower only issued this restriction seconds before I passed under the arriving jet. Additionally; the transmission was blocked by another aircraft speaking on frequency at the same time. It also appears that tower informed the [business jet] that I would be staying east of the extended centerline on the 120.6 frequency. While tower had issued me no such restriction; I would have stayed east of the extended centerline of 31R had I heard this transmission; which was not broadcast on my assigned frequency 118.3.I believe that this event was not an actual loss of separation; since I had the arriving business jet in sight; and I passed well underneath this airplane. However; tower could have issued me either a restriction to remain east of the centerline; or an altitude restriction to avoid this occurring in the future. Tower informed me that I should have remained east of the extended centerline at all times. However; I can find no published reference to support their statement that I should have remained east of the extended centerline. If the tower expects that pilots should remain east of the extended centerline; this restriction should be either be issued in a takeoff clearance or published.

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Original NASA ASRS Text

Title: Citabria pilot reported the Tower was unhappy with his track after departure that led to a conflict with a business jet.

Narrative: On climbout from Runway 31R at BFI I requested a southeast departure. Tower approved my turn southbound; informed me of two helicopters as traffic and two inbound business jets. I made a turn southbound; and proceeded south at 900 ft MSL; and reported all traffic in sight. Tower did not issue me any restriction to remain east of the extended centerline of 31R; and I continued south at 900 ft with the arriving business jet in sight. While crossing under the extended centerline at 900 feet; I apparently activated the TCAS on a business jet on final for 31L. I had the aircraft in sight at all times; and believed that I maintained adequate visual separation from [him]. Upon landing; tower informed me of a possible pilot deviation; and that the tower had instructed me not to cross the extended centerline of 31L.Upon listening to the LiveATC audio archives for my flight; it appears that Tower only issued this restriction seconds before I passed under the arriving jet. Additionally; the transmission was blocked by another aircraft speaking on frequency at the same time. It also appears that tower informed the [business jet] that I would be staying east of the extended centerline on the 120.6 frequency. While tower had issued me no such restriction; I would have stayed east of the extended centerline of 31R had I heard this transmission; which was not broadcast on my assigned frequency 118.3.I believe that this event was not an actual loss of separation; since I had the arriving business jet in sight; and I passed well underneath this airplane. However; tower could have issued me either a restriction to remain east of the centerline; or an altitude restriction to avoid this occurring in the future. Tower informed me that I should have remained east of the extended centerline at all times. However; I can find no published reference to support their statement that I should have remained east of the extended centerline. If the tower expects that pilots should remain east of the extended centerline; this restriction should be either be issued in a takeoff clearance or published.

Data retrieved from NASA's ASRS site 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.