TKOF WITH DOOR WARNING LIGHT INDICATION.

Narrative

AFTER SUPERVISING THE LOADING OF THE PLANE (AN SMT) AT BEECH W; ONT; I GOT IN TO START THE ENGS AND GOT A DOOR WARNING LIGHT. I HAD ABOUT 12-13 MINS UNTIL MY RELEASE TIME FOR FLOW CTL TO LAX. I GOT OUT AND CHKED THAT THE CARGO DOOR WAS SHUT PROPERLY. ALSO CHKING AGAIN THE PAD AND CABIN DOORS. THE WARNING LIGHT WAS STILL ON; SO I GOT OUT AGAIN. I RECHKED THE DOOR INCLUDING THE ACTION OF THE LOCKING PINS AND THEIR RESPECTIVE HOLES. THEY ALL SEEMED FINE. WITH EVERYTHING SECURELY CHKED AND BOTTOMED UP I GOT IN AND STILL HAD THE WARNING LIGHT. MY PAST EXPERIENCE WITH THE COMPANY ACFT (MOSTLY SMT) WAS SUCH THAT I FIGURED THE WARNING CIRCUIT HAD FAILED AND I WOULD HAVE IT CHKED AFTER ARR AND UNLOADING AT LAX. WHEN I GOT TO THE RWY OF 26R AND TXWY 100 I WAS DELAYED PAST MY RELEASE TIME FOR WAKE AVOIDANCE THEN 'CLRED FOR IMMEDIATE TKOF.' I MADE A HIGHER THAN NORMAL SPD SWEEP ON THE RWY AND A BOX CAME OUT OF THE RIGHT PAX DOOR (?). I HAD NOT CHKED THE PAX DOOR AS THE COMPANY POLICY IS TO NOT USE IT AND HAVE IT LOCKED. (THE PLTS DON'T EVEN HAVE A KEY TO IT.) WHEN LOCKED IT CAN'T BE OPENED FROM INSIDE OR OUT. TO ME IT HAD BECOME A PART OF THE ACFT STRUCTURE. I WAS NOTIFIED AT LAX THAT I HAD DROPPED SOMETHING ON THE RWY AT ONT. IT WAS ONLY WHEN WALKING AROUND THE PLANE THAT I FOUND THE OFFENDING DOOR. SOMEHOW IT HAD BEEN UNLOCKED. ALSO; THE BOTTOM DETENTION DEVICE (A BALL AND SPRING) WAS MISSING LETTING THE HANDLE SLIP OUT OF THE SAFETY POS. SUGGESTION: GIVE PLTS KEYS TO THE DOOR AND CONTROL OF THE SYSTEMS AND MAYBE A WARNING LIGHT DESIGNATING WHICH DOOR IS OPEN.