RWY EXCURSION IN A NIGHT OP.

Narrative

I CONTINUED TRACKING THE LOC AND GS (IT WAS NIGHTTIME AND AN UNFAMILIAR ARPT) UNTIL 1 1/2-2 MI FINAL. DURING THIS PHASE OF FLT WE AGAIN BRIEFED THE POSSIBILITY OF HYDROPLANING. AT THIS TIME I BEGAN MY DSCNT BELOW THE GS ATTEMPTING TO LAND ON THE END OF RWY. I ENDED TOUCHING DOWN AT THE 1000 FT MARKERS. WE TOUCHED DOWN AT REF-5. AFTER TOUCHDOWN I DEPLOYED THE SPOILERS AND STARTED TO APPLY BRAKING I REALIZED THAT WE WEREN'T STOPPING SO I APPLIED HARDER PRESSURE ON THE BRAKES. IT FELT LIKE THE ANTI-SKID WAS OPERATING AT THIS TIME. THEN THE ACFT STARTED TO VEER OFF TO THE L SIDE OF THE RWY SO I RELEASED SOME BRAKE PRESSURE AND WITH RUDDER PRESSURE REGAINED CTL OF THE ACFT. THIS WAS AN INDICATION TO ME THAT WE WERE HYDROPLANING. I CONTINUED WITH BRAKING BUT IT SEEMED LIKE IT WASN'T STOPPING AND I REALIZED THAT WE WERE GOING TO RUN OFF THE END OF THE RWY. AS WE DECELERATED BRAKING BECAME MORE EFFECTIVE. I MAINTAINED CTRLINE AND SLOWED DOWN AS MUCH AS I COULD. WE ROLLED APPROX 50 FT OFF THE END OF THE RWY. THE ACFT CONTINUED ROLLING WITH EASE. SO I MADE A MEDIUM L TURN. 180 DEGS AND TAXIED BACK ONTO RWY 23. NO DAMAGE WAS DONE TO THE ACFT AND NO RWY LIGHTS WERE TAKEN OUT. WE TAXIED TO THE FBO AND AFTER A THOROUGH INSPECTION OF THE ACFT AND CALLING THE CHIEF PLT WE CONTINUED WITH THE NEXT LEG OF THE FLT.