CAPT OF AN LTT ACR ACFT EXCEEDED FLT TIME DUTY LIMITATIONS.

Narrative

I HAD FLOWN 5 LEGS AFTER WHICH I WAS ASKED BY CREW SCHEDULING IF I WOULD MIND FLYING ONE MORE LEG INTO AN OVERNIGHT. THEY TOLD ME THE FLT WAS ALREADY LATE AND THAT THE PAX WERE ALREADY ON BOARD; BUT THEY WERE SHORT ONE PLT. I SAID IF IT WORKED; I WOULDN'T MIND TAKING THE FLT. THE SCHEDULER THEN ASKED ME HOW MUCH REST I HAD THE NIGHT BEFORE AND HOW LONG I HAD BEEN ON DUTY. I TOLD HIM BOTH AND HE SAID HE DIDN'T SEE ANY PROB WITH ME FLYING THE TRIP. SINCE THE SCHEDULER WAS USING THE COMPANY'S FOS COMPUTER SYS; WHICH IS SUPPOSED TO GENERATE AN ALERT IF A TRIP IS ILLEGAL. I HAD NO REASON TO DOUBT HIM; SO I ACCEPTED THE TRIP. ABOUT HALFWAY TO THE DEST I STARTED THINKING ABOUT THE AMOUNT OF HRS I HAD FLOWN. ADDING UP MY TIMES FOR THE PREVIOUS 5 LEGS I CAME UP WITH 7.0 HRS. SINCE THE LEG I WAS FLYING WAS SCHEDULED FOR 1.5 HRS AND THE MAX IS 8 HRS; IT WAS OBVIOUS THAT THE TRIP WAS ILLEGAL. I CALLED THE SCHEDULER WHEN I GOT ON THE GND AND ASKED HIM TO ADD MY TIMES; AND HE CONFIRMED THAT THE TRIP WAS ILLEGAL. I ASKED WHY THE FOS DIDN'T GENERATE AN ALERT; AND WAS TOLD THE ALERT CAME UP ON THE WRONG DAY AND THAT THE PROGRAM STILL HAD SOME BUGS IN IT. MY SOLUTION; FROM NOW ON; IS TO CHK THE LEGALITY OF A TRIP MYSELF AND NOT RELY ON A COMPUTER PROGRAM.