Narrative:

Air carrier Y, a BA31 jetstream, had been holding short of runway 19R at intersection K for approximately 30 mins. They were waiting for a departure release from socal approach tmu for arrival at lax. The initial coordination was that they could wait at the runway and hope for a possible hole (departure release) 30 mins in the future -- or be assigned a specific departure window, which would be 1 hour in the future. The crew elected to hold at the runway and hope for a hole to materialize. Socal tmu eventually called back with a release of XX12 void at XY14. At about XX10 I told air carrier Y 'full length is available, runway 19R taxi into position and hold.' I anticipated that air carrier Y would turn north on the runway and taxi from K to the approach end of runway 19R, a distance of 300 ft. This is not unusual for the operation at sna. In the meantime, I instructed a cessna 152, who was straight-in to runway 19R, to change to runway 19L, and cleared to land runway 19L. The pilot, on about 2 mi final at this time, acknowledged and complied. I knew that the C152 parked on the west side of airport, so when he exited runway 19L at intersection J (1600 ft south of approach end), I instructed him to cross runway 19R, knowing air carrier Y was holding in position. I don't recall if I told him traffic was holding in position. I did not advise air carrier Y that traffic was crossing downfield. As the cessna was approaching runway 19R at intersection J, I observed air carrier Y. At first it looked as though they were still taxiing into position, then I realized I saw landing lights on left and right wings on, and it looked like they were moving forward (south in takeoff direction). I told the cessna to 'stop' 2 or 3 times. Then I told air carrier Y to 'stop' (I didn't say cancel takeoff clearance because I never cleared him for takeoff). I also told him he was instructed to 'taxi into position and hold.' the cessna ended up able to stop short of runway 19R edge line as best I could tell. The BA31 reduced power and rolled through the intersection. I had him turn off the runway to the right at H (2500 ft downfield).

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Original NASA ASRS Text

Title: FLC OF A BA31 STARTED TKOF ROLL PRIOR TO BEING CLRED RESULTING IN A GND CONFLICT WITH A C152 PREVIOUSLY CLRED TO CROSS THE RWY.

Narrative: ACR Y, A BA31 JETSTREAM, HAD BEEN HOLDING SHORT OF RWY 19R AT INTXN K FOR APPROX 30 MINS. THEY WERE WAITING FOR A DEP RELEASE FROM SOCAL APCH TMU FOR ARR AT LAX. THE INITIAL COORD WAS THAT THEY COULD WAIT AT THE RWY AND HOPE FOR A POSSIBLE HOLE (DEP RELEASE) 30 MINS IN THE FUTURE -- OR BE ASSIGNED A SPECIFIC DEP WINDOW, WHICH WOULD BE 1 HR IN THE FUTURE. THE CREW ELECTED TO HOLD AT THE RWY AND HOPE FOR A HOLE TO MATERIALIZE. SOCAL TMU EVENTUALLY CALLED BACK WITH A RELEASE OF XX12 VOID AT XY14. AT ABOUT XX10 I TOLD ACR Y 'FULL LENGTH IS AVAILABLE, RWY 19R TAXI INTO POS AND HOLD.' I ANTICIPATED THAT ACR Y WOULD TURN N ON THE RWY AND TAXI FROM K TO THE APCH END OF RWY 19R, A DISTANCE OF 300 FT. THIS IS NOT UNUSUAL FOR THE OP AT SNA. IN THE MEANTIME, I INSTRUCTED A CESSNA 152, WHO WAS STRAIGHT-IN TO RWY 19R, TO CHANGE TO RWY 19L, AND CLRED TO LAND RWY 19L. THE PLT, ON ABOUT 2 MI FINAL AT THIS TIME, ACKNOWLEDGED AND COMPLIED. I KNEW THAT THE C152 PARKED ON THE W SIDE OF ARPT, SO WHEN HE EXITED RWY 19L AT INTXN J (1600 FT S OF APCH END), I INSTRUCTED HIM TO CROSS RWY 19R, KNOWING ACR Y WAS HOLDING IN POS. I DON'T RECALL IF I TOLD HIM TFC WAS HOLDING IN POS. I DID NOT ADVISE ACR Y THAT TFC WAS XING DOWNFIELD. AS THE CESSNA WAS APCHING RWY 19R AT INTXN J, I OBSERVED ACR Y. AT FIRST IT LOOKED AS THOUGH THEY WERE STILL TAXIING INTO POS, THEN I REALIZED I SAW LNDG LIGHTS ON L AND R WINGS ON, AND IT LOOKED LIKE THEY WERE MOVING FORWARD (S IN TKOF DIRECTION). I TOLD THE CESSNA TO 'STOP' 2 OR 3 TIMES. THEN I TOLD ACR Y TO 'STOP' (I DIDN'T SAY CANCEL TKOF CLRNC BECAUSE I NEVER CLRED HIM FOR TKOF). I ALSO TOLD HIM HE WAS INSTRUCTED TO 'TAXI INTO POS AND HOLD.' THE CESSNA ENDED UP ABLE TO STOP SHORT OF RWY 19R EDGE LINE AS BEST I COULD TELL. THE BA31 REDUCED PWR AND ROLLED THROUGH THE INTXN. I HAD HIM TURN OFF THE RWY TO THE R AT H (2500 FT DOWNFIELD).

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.