Narrative:

A DC9 had been cleared for departure on runway 10. I had been cleared from the north side of runway 10 to the parallel taxiway. I was then cleared to depart to the south across runway but to pass behind the DC9. It appeared to me that the DC9 was accelerating rapidly enough to allow me to continue sbound and pass behind and above the path of the departing DC9. The aircraft was accelerating much slower than I'd anticipated and it became apparent I would not be able to continue my departure path and pass behind the DC9. Tower called to confirm I was passing behind the DC9. By that time I'd made a turn parallel to the departure path of the DC9 about 200-300 ft from runway 10 until the departing aircraft passed me, then I turned south on course. The clearance from tower was clear and appropriate. I misjudged the relative speed of the DC9 and made my departure timing too soon. Tower confirmed twice (clearance and subsequent) that I had the aircraft in sight. My error was in misjudging the ground speed of the departing aircraft, causing me to select an alternate path parallel to the departing aircraft until I could insure appropriate separation.

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Original NASA ASRS Text

Title: A BELL 206 CLRED TO PASS ACROSS RWY 10 BEHIND A DEPARTING DC9 MISJUDGES THE ACCELERATION OF THE DC9 REQUIRING A TURN TO PARALLEL THE RWY UNTIL THE DC9 PASSED. 200 FT SEPARATION IS ESTIMATED.

Narrative: A DC9 HAD BEEN CLRED FOR DEP ON RWY 10. I HAD BEEN CLRED FROM THE N SIDE OF RWY 10 TO THE PARALLEL TXWY. I WAS THEN CLRED TO DEPART TO THE S ACROSS RWY BUT TO PASS BEHIND THE DC9. IT APPEARED TO ME THAT THE DC9 WAS ACCELERATING RAPIDLY ENOUGH TO ALLOW ME TO CONTINUE SBOUND AND PASS BEHIND AND ABOVE THE PATH OF THE DEPARTING DC9. THE ACFT WAS ACCELERATING MUCH SLOWER THAN I'D ANTICIPATED AND IT BECAME APPARENT I WOULD NOT BE ABLE TO CONTINUE MY DEP PATH AND PASS BEHIND THE DC9. TWR CALLED TO CONFIRM I WAS PASSING BEHIND THE DC9. BY THAT TIME I'D MADE A TURN PARALLEL TO THE DEP PATH OF THE DC9 ABOUT 200-300 FT FROM RWY 10 UNTIL THE DEPARTING ACFT PASSED ME, THEN I TURNED S ON COURSE. THE CLRNC FROM TWR WAS CLR AND APPROPRIATE. I MISJUDGED THE RELATIVE SPD OF THE DC9 AND MADE MY DEP TIMING TOO SOON. TWR CONFIRMED TWICE (CLRNC AND SUBSEQUENT) THAT I HAD THE ACFT IN SIGHT. MY ERROR WAS IN MISJUDGING THE GND SPD OF THE DEPARTING ACFT, CAUSING ME TO SELECT AN ALTERNATE PATH PARALLEL TO THE DEPARTING ACFT UNTIL I COULD INSURE APPROPRIATE SEPARATION.

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.