COMMUTER DSNDS BELOW ASSIGNED ALT DURING DSCNT.

Narrative

WE WERE GIVEN A CLRNC TO 5000 FT AND TO EXPECT A VISUAL APCH TO HAGERSTOWN ARPT. COMPANY TFC HAD JUST DEPARTED AND WE WERE TOLD TO EXPECT A VISUAL AFTER COMPANY TFC WAS NO FACTOR. TFC WAS RPTED AT 12 O'CLOCK. THE CAPT AND MYSELF WERE BOTH LOOKING AND SPOTTED THE TFC PASSING BELOW US OFF OUR R SIDE APPROX 2000 FT BELOW AND A MI AWAY. THE ARPT WAS OFF OUR L SIDE AND APPROX 5 MI. TO VERIFY OUR VISUAL APCH; THE CAPT CALLED ZDC. THE CTLR TOLD US 'NEGATIVE.' OUR PRESENT ALT WAS 4500 FT. I PWRED UP AND RETURNED TO 5000 FT. TOTAL TIME BELOW 5000 FT WAS 25 SECONDS. ONCE WE REACHED 5000 FT WE WERE THEN GIVEN A CLRNC FOR A VISUAL APCH INTO HAGERSTOWN. I BELIEVE THE LACK OF COM THAT LED TO THE EVENT WAS CAUSED BY FATIGUE. WE WERE ON THE THIRD DAY OF A TRIP. WE WERE ON COMPENSATED REST. IT WAS OUR 6TH LEG; OVER 7TH HR OF FLT AND 12TH HR OF DUTY WITH 2 MORE LEGS TO FLY. TOTAL FLT THAT DAY WAS 8 HR 40 MINS; AND DUTY TIME WAS 14 HRS; WITHOUT ANY MORE OCCURRENCES. THE PART 135 REST REQUIREMENTS NEED TO BE ADDRESSED. SUPPLEMENTAL INFO FROM ACN 271762: WE WERE APCHING HGR ARPT FROM THE W; AND CLRED TO MAINTAIN 5000 FT MSL FOR TFC AT 4000 DEPARTING HGR TO THE W. WE WERE ANTICIPATING A VISUAL APCH TO RWY 27. I WAS THE PNF AND L CTR FREQ TO CONTACT OPS IN RANGE TO COMPLETE OUR APCH CHKLIST. WHEN I RETURNED TO THE FREQ; THE PF HAD DSNDED THROUGH 4600 MSL AND I ASKED IF WE HAD THEREFORE BEEN CLRED FOR THE VISUAL APCH: HE REPLIED THAT HE WAS UNSURE. I THEN; IMMEDIATELY QUERIED ATC AS TO WHETHER WE HAD INDEED BEEN CLRED FOR A VISUAL AND WAS TOLD 'NEGATIVE' DUE TO OUTBOUND TFC. THE IMPORTANT POINT; I BELIEVE; IS THIS. BOTH THE FO AND MYSELF ARE VERY SAFETY MINDED AND CONSCIENTIOUS ABOUT OUR JOBS; BUT THIS WAS AN 8 LEG DAY; WHICH WAS UNREALISTICALLY BLOCKED TO 7:05. THIS WAS OUR 6TH LEG AND WE HAD BEEN ON DUTY FOR 11 HRS; AND WERE QUICKLY BECOMING QUITE FATIGUED. WE WENT ON TO FINISH THE DAY WITH 14:20 DUTY AND OVER BLOCKED TO 8:40 MINS.