FLC DIDN'T STAY ON AIRWAY BECAUSE THE 'CO-CAPT' DIDN'T THINK THE COURSE CHANGE WAS GREAT ENOUGH TO BE CONCERNED WITH AND SET DIRECT TO THE NEXT POINT. ATC INTERVENED AND QUESTIONED WHY THE FLC WAS OFF THE AIRWAY; GAVE THEM A HDG TO REINTERCEPT.

Narrative

I WAS FLYING CAPT/PIC WITH A CO-CAPT/SIC WHO WAS HANDLING THE RADIOS (NAVS AND COMS). ENRTE IFR WE WERE GIVEN A CLRNC TO CROSS 25 DME E OF IGN AT 9000 FT. DURING OUR DSCNT ZBW CALLED QUESTIONING IF WE WERE ON V58 AS PREVIOUSLY CLRED. CO-CAPT RESPONDED 'AFFIRMATIVE.' CTR COUNTERED 'TURN TO (ASSIGNED HDG) TO REJOIN V58 AS CLRED.' I DIRECTED MY ATTN TOWARD THE NAV RADIOS AND BEGAN QUESTIONING THE DISCREPANCY. I FOUND THAT V58 HAS A SMALL DOGLEG IN IT IDENTED BY MOONI INTXN. I QUESTIONED THE CO-CAPT ABOUT IT; HE STATED HE DIDN'T FEEL IT WAS ENOUGH OF A DOGLEG TO WORRY ABOUT AND WAS 'GIVING ME DIRECT' TO THE NEXT VOR. I QUICKLY SET THE RADIOS UP TO THE PROPER FREQ AND RADIAL AND TO OUR DISMAY; WE HAD A FULL SCALE DEFLECTION ON OUR CDI! WE SOON INTERCEPTED OUR ASSIGNED COURSE WHILE CONTINUING OUR DSCNT TO 9000 FT ONLY TO REALIZE I HAD NOT MONITORED OUR DSCNT CLOSE ENOUGH TO MEET THE DME REQUIREMENT. WE WERE DSNDING THROUGH 9400 FT UPON REACHING 25 DME. WE LEVELED AT 9000 FT WITH NO FURTHER INCIDENTS. WE DID NOT ADHERE TO TWO CLRNCS AT THE SAME TIME; JEOPARDIZING SAFETY! THIS PROB BEGAN WHEN WE DID NOT ADHERE TO THE STRICT DISCIPLINE NECESSARY FOR IFR NAV. CORRECTIVE ACTION WAS SOON TAKEN TO IDENT AND SOLVE THIS PROB BUT CONTINUATION OF OTHER SYS (IE; FLYING THE AIRPLANE) WAS NOT MONITORED PROPERLY CAUSING US TO NOT MEET OUR ALT/DME REQUIREMENT. WE HAD A BREAKDOWN OF CRM. MY CO-CAPT SHOULD HAVE VOICED HIS DISCONCERN OF THE DOGLEG TO ME FOR MY OPINION. I SHOULD HAVE BEEN CHKING HIS NAV ACTIONS AS A XCHK. I MUST ALSO KEEP FROM DIVERTING ALL MY ATTN TO ONE PROB AND CONTINUE TO MONITOR OTHER SYS.