FALCON 50 ON A TRIP FROM 40N TO ORD HAS TO DIVERT TO PIT WHEN THEIR LASER REF NAV SYS PROVES UNUSABLE.

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FALCON 50 (DA50) FLT IFR FILED FROM 40N TO ORD. COMPANY PLT (TYPE RATED) YET LIMITED TIME IN TYPE -- LESS THAN 500 HRS FLYING WITH A SUPPLEMENTAL PLT (MYSELF) WHO WAS LISTED AS CAPT ON FLT PLAN. I HAVE 1400 HRS IN FALCON-50; 6200+ HRS TOTAL TIME. WX ACROSS EASTERN UNITED STATES -- BEAUTIFUL VFR; CLR; UNTIL CHICAGO WHERE WX BASES WERE 1000 FT MSL OVCST WITH TOPS TO 11000 FT MSL IN RAIN. FLT POSITIONED FROM BDR; CT; TO 40N; PA; EMPTY FOR PAX PICKUP. UPON ARRIVING 40N; PF ADVISED ME TO TURN OFF THE LASER REF NAV SYS. AS I QUESTIONED THIS PRACTICE -- SHOULD LEAVE SYS RUNNING AND SHOULD ONLY REALIGN BOTH NAVS -- PLT AGAIN ADVISED TO PWR DOWN SYS WHILE WAITING FOR PAX. PAX SHOWED UP EARLY AND SYS WERE NOT TURNED ON. UPON STARTING ENGS; I NOTICED THAT BOTH LASER NAVS WERE STILL OFF. WE TURNED THEM ON; HOWEVER; THE ALIGNING PROCESS WAS NOT CORRECTLY COMPLETED. A HDG FLAG SHOWED A DIFFERENCE OF 20 DEGS BTWN THE ACTUAL ACFT HDG AND THE DISPLAYED HDG ON THE EFIS TUBES. SOME CONFUSION ENSUED ABOUT GETTING THE PROPER ALIGNMENT COMPLETED. IT WAS DETERMINED TO DEPART IN 'ATTITUDE REF' AND CONTACT CHIEF PLT ON FLT PHONE TO CORRECT PROB IN CLBOUT. PF HANDLED FLYING AND COM DUTIES; I (PNF) CONTACTED COMPANY OPS FOR INFO. THIS IS NOT THE NORMAL ACFT THAT I FLY AND ITS EFIS INTERFACE IS DIFFERENT FROM THE ACFT I ROUTINELY FLY. BY THE TIME I CONTACTED OPS; THE ACFT WAS IN LEVEL FLT AT FL350. WE WERE CLRED BY ATC TO JOIN AN AIRWAY ON THE PRESENT HDG. I SUGGESTED THAT WE GO DIRECT TO EWC VOR TO REALIGN THE NAVS OVERHEAD THE VOR. IT BECAME APPARENT THAT THE NAVS WOULD NOT CORRECTLY SHOW THE ACTUAL VOR POS. ATC ASKED WHERE WE WERE GOING AS EWC VOR WAS ABOUT 20 DEGS OFF OUR COURSE. I ADVISED PF TO ASK ATC TO DSND BELOW FL180 WHEREBY WE WOULD CANCEL THE IFR FLT PLAN; AND PROCEED VFR TO PIT; PA. ONCE AT PIT AND ON THE GND; I KNEW WE COULD PROPERLY CORRECT THE HDG ERROR FROM A KNOWN POS. IN HINDSIGHT; BOTH PLTS WERE NOT TOTALLY KNOWLEDGEABLE ON THE NAV SYS INSTALLED. THE FLT WAS CLRED OUT OF CLASS A AIRSPACE AND CANCELED IFR OUT OF FL180. FLT VFR TO PIT WAS ROUTINE AND ONCE AT THE GA RAMP; PROB WAS CORRECTED IN 3 MINS -- ALL SYS NORMAL. FLT CONTINUED TO ORD WITHOUT FURTHER INCIDENT. FLT PROBABLY SHOULD NOT HAVE DEPARTED WITH HDG ERROR. HOWEVER; THE QUICK FIX WHICH COULD HAVE TAKEN PLACE AIRBORNE COULD NOT BE COMPLETED DUE TO CREW WORKLOAD AND ATC HDG CHANGES; ETC.