COMMUTER ACFT FAILS TO HOLD SHORT OF HOLD LINE; RWY INCURSION.

Narrative

MY CAPT AND I WERE OPERATING FLT FROM GON TO PHL. THE ARPT RWY AND TXWY CONDITIONS WERE NOTAMED AS POOR; SNOW COVERED HARD PACKED SNOW AND ICE. AFTER BOARDING PAX AND COMPLETING ALL APPROPRIATE CHKLISTS; WE WERE GIVEN A CLRNC TO TAXI FROM THE RAMP TO RWY 33 VIA TXWY 'D.' I WAS THE PF AND BEGAN A SLOW AND CAUTIOUS TAXI. AS I APCHED THE HOLD LINE FOR RWY 33; A PIPER SENECA WAS ON FINAL FOR SAME. I APPLIED THE BRAKES TO STOP SHORT OF THE HOLD LINE AND THE ACFT BEGAN TO SKID. I RELEASED THE BRAKES AND REAPPLIED THEM WITH LITTLE EFFECT. THE CAPT IMMEDIATELY ADVISED ATC THAT WE COULDN'T HOLD SHORT OF RWY 33. THE ACFT THEN BEGAN TO YAW TO THE R. I THEN MOVED THE L PROP CTL TO THE BETA POS TO STOP THE YAW. THERE WAS AGAIN LITTLE EFFECT. THE CAPT THEN CALLED FOR THE CTLS AS THE ACFT CROSSED OVER THE HOLD SHORT LINE. HE APPLIED REVERSE THRUST TO BOTH ENGS AND THE ACFT CAME TO A STOP 40 DEGS OFF CTR AND 5 FT SHORT OF RWY 33. THE SENECA PERFORMED A BALKED LNDG AS INSTRUCTED BY ATC. AFTER DISCUSSING THE EVENT WITH ATC; WE DECIDED TO CONTINUE THE FLT. I BRIEFED THE PAX ON THE EVENT AND THE CAPT AND I REVIEWED OUR TKOF PLANS AGAIN. ENRTE WE ADVISED OUR COMPANY OF BRAKING ACTION ON TXWY 'D' AS NIL. I HAVE NEW RESPECT FOR 'POOR BRAKING ACTION' RPTS. IN THE FUTURE I WILL TAXI SLOWER AND BE MORE AWARE OF HOLD LINE LOCATIONS. ALSO; I HAVE LEARNED THAT IMMEDIATE APPLICATION OF REVERSE PWR IN ACFT SKIDDING SCENARIOS MAY BE HELPFUL AND/OR NECESSARY.