Narrative:

I was cleared for takeoff with an ATC instruction to 'fly straight out until advised.' at approximately 800 ft, traffic was pointed out at my 3 O'clock position and that a right turn on course to the northeast to pass behind the traffic was approved. The traffic appeared to be moving in the opposite direction, as though entering a downwind for runway 25R (I departed runway 25L). I then turned right crosswind on that assumption and lost sight of the traffic. In actuality, the other aircraft had done a touch-and-go on runway 25R (different frequency) and simply was climbing at an airspeed perhaps 40 KTS slower than me, accounting for the false assumption of it being opposite direction and therefore 'no factor.' (dusk didn't help.) I should have maintained visual contact. The local controller should have stated 'turn outside of traffic departing the parallel runway remaining in the pattern!' to increase my situational awareness in lieu of the two frequency tower operations.

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Original NASA ASRS Text

Title: A DEPARTING PA30 PLT OFF RWY 25L INCURS AN NMAC WITH A C172 DEPARTING RWY 25R IN THE DVT TFC PATTERN.

Narrative: I WAS CLRED FOR TKOF WITH AN ATC INSTRUCTION TO 'FLY STRAIGHT OUT UNTIL ADVISED.' AT APPROX 800 FT, TFC WAS POINTED OUT AT MY 3 O'CLOCK POS AND THAT A R TURN ON COURSE TO THE NE TO PASS BEHIND THE TFC WAS APPROVED. THE TFC APPEARED TO BE MOVING IN THE OPPOSITE DIRECTION, AS THOUGH ENTERING A DOWNWIND FOR RWY 25R (I DEPARTED RWY 25L). I THEN TURNED R XWIND ON THAT ASSUMPTION AND LOST SIGHT OF THE TFC. IN ACTUALITY, THE OTHER ACFT HAD DONE A TOUCH-AND-GO ON RWY 25R (DIFFERENT FREQ) AND SIMPLY WAS CLBING AT AN AIRSPD PERHAPS 40 KTS SLOWER THAN ME, ACCOUNTING FOR THE FALSE ASSUMPTION OF IT BEING OPPOSITE DIRECTION AND THEREFORE 'NO FACTOR.' (DUSK DIDN'T HELP.) I SHOULD HAVE MAINTAINED VISUAL CONTACT. THE LCL CTLR SHOULD HAVE STATED 'TURN OUTSIDE OF TFC DEPARTING THE PARALLEL RWY REMAINING IN THE PATTERN!' TO INCREASE MY SITUATIONAL AWARENESS IN LIEU OF THE TWO FREQ TWR OPS.

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.