A B757 PLT NOTES THAT AT DFW AN FMC WILL REVERT TO FLT PLANNED RWY DURING TAXI OUT CAUSING AN INCORRECT DEP RWY FOR THE DESIRED SID.

Narrative

RNAV DEPS. WE/US PLTS KEEP RECEIVING EMAILS ABOUT DEVS ON RNAV DEP BECAUSE OF THE WRONG RWY IN THE FMC. USUALLY OUR TPS WILL LIST 5 DIFFERENT RWYS; WITH THE FIRST RWY ON THE LIST BEING PRIMARY. MY EXPERIENCE IS THAT ON MANY DEPS THIS PRIMARY RWY IS NOT THE PREFERRED BY ATC. THE LIST OF RWYS IS DECIDED BY SOMEONE IN A ROOM IN DFW; WHO ISN'T AWARE OF LCL RWY CONFIGNS. ORD IS A GOOD EXAMPLE. ONE PROB I'VE NOTICED IS AS FOLLOWS: FMC IS SELECTED FOR THE APPROPRIATE RWY AT GATE; NOT THE PRIMARY RWY ON TPS. ON TAXI OUT ONCE THE LOAD IS RECEIVED THE FMC WILL DEFAULT BACK TO THE PRIMARY RWY ON THE TPS. RUNNING CHKLIST; MONITORING ATC ON THE TAXI OUT; I'VE NOTICED MANY CREW MEMBERS DON'T CATCH THE FMC DEFAULTING BACK TO THE PRIMARY RWY; NOT THE RWY SELECTED AT THE GATE TO MATCH ARPT OPS. I AM ONLY FAMILIAR WITH THE B767/B757; BUT WITH THE FMC DEFAULTING BACK TO THE TPS PRIMARY RWY MIGHT BE CREATING SOME OF THE RNAV VIOLATIONS. THE CORRECT RWY; SID AND TRANSITION BEING SELECTED BEFORE TAXI BUT THE FMC DEFAULTS BACK TO THE PRIMARY RWY ON THE TPS AFTER LOAD CLOSEOUT; LEAVING THE WRONG RWY IN THE FMC?