A B737-300 FLC HAS TO ABORT THEIR TKOF WHEN THE PIC NOTES A B727 TAXIING ACROSS THEIR RWY MIDFIELD ON FREQ WITH GND CTL AT PHL; PA.

Narrative

AFTER AN ATC DELAY; A RWY CHANGE AND A RERTE; WE WERE FINALLY CLRED FOR TKOF ON RWY 9L. THE FO WENT BACK TO MAKE THE PA AS I PULLED ONTO THE RWY. WHEN HE RETURNED; HE TOOK OVER THE ACFT AS IT WAS HIS LEG. I CONFIRMED WITH HIM THAT WE WERE CLRED TO GO AND HE BROUGHT THE THROTTLES UP TO 45% N2; THEN TO UPRIGHT (ABOUT 75%) AND WE STARTED TO ROLL. AT THAT TIME I LOOKED DOWN THE RWY AND SAW A B727 APCH THE RWY FROM THE L ABOUT 2000 FT DOWN. SINCE HE SEEMED TO BE GOING A BIT FAST; I SAID TO THE FO 'HOLD IT.' IN OTHER WORDS; DON'T MOVE THE THROTTLES TO TOGA THRUST. AT THIS POINT; THE B727 CONTINUED ACROSS OUR RWY AND I ABORTED THE TKOF AFTER ABOUT 1000 FT ROLL TOTAL. I ASKED TWR IF WE HAD BEEN CLRED FOR TKOF; TO WHICH HE REPLIED 'YES; CLRED FOR TKOF.' I TOLD HIM ABOUT THE OTHER ACFT AND THAT WE NOW HAD TO RETURN TO THE BEGINNING OF THE RWY FOR TKOF. I THINK THERE WAS A LACK OF COORD BTWN LCL AND GND RATHER THAN AN INCURSION BY THE B727; DUE TO THE FACT THAT THEY HAD JUST CHANGED FROM A W OP TO AN E. 'CLRED FOR TKOF' DOESN'T MEAN THE TKOF IS CLR! TAKE A LOOK. SUPPLEMENTAL INFO FROM ACN 475828: GOOD JOB TO MY CAPT SCANNING ENTIRE RWY. I WILL BE MORE VIGILANT IN THAT RESPECT.