A CANADAIR CL65 AT FL280 HAD EICAS WARNING AND INDICATION OF R ENG OVERSPD. EFIS FAILURE AND DEFERRED AUTOTHROTTLE CONTRIBUTED TO HIGH COCKPIT WORKLOAD.

Narrative

RIGHT AFTER TKOF FROM ZZZ; WE GOT AN EFIS 'COMP/MON/CAUTION' MESSAGE ON EICAS AND NOTED CAPT'S HDG OFF AND SIGNIFICANT FMS NAV INACCURACY. I WAS PF AND TOOK OVER RADIOS. CAPT RAN THE QRH AND TALKED TO DISPATCH AND MAINT CTL. THE PROBS WOULD NOT WORK THEMSELVES OUT AND QRH PROCS DID NOT CLR UP FMS/HDG ANOMALIES. I GOT THE HIGH ALT CHART OUT AND STARTED LOOKING FOR NAVAID FREQS TO NAV BY. CTR HELPED WITH AN INITIAL HDG TO ZZZ1. NEEDLESS TO SAY; COCKPIT WORKLOAD WAS HIGH. THE AUTOMATIC PERFORM RESERVE (APR) SYS HAD BEEN DEFERRED SO THE ENGS WERE ON HYDRO MECHANICAL CTL. AS WE CLBED N1; RPM EDGED UP AND I PULLED THRUST LEVERS BACK TO REMAIN WITHIN LIMITS. I SET THE N1 RPM BELOW CLB PWR SETTING AND UNFOLDED THE HI ALT IFR CHART TO LOOK FOR A NAVAID. UNFORTUNATELY; THE CHART OBSCURED MY VIEW OF THE N1 DISPLAY AND THE NEXT THING I KNEW; WE GOT AN EICAS OVERSPD WARNING ON THE R ENG. I IMMEDIATELY PULLED PWR BACK. INTERESTINGLY; NEITHER THE CAPT NOR I NOTED N1 RPM HIGHER THAN 97% RANGE. THE WARNING OCCURS AT 98.6. WE CONTINUED ON THE ZZZ1 SINCE ENGS WERE RUNNING FINE. LATER; FUEL BECAME AN ISSUE SINCE WE HAD BEEN DELAYED GETTING OUT OF ZZZ. SINCE WE WERE MANUALLY NAVING; THIS REQUIRED CONTINUOUS MONITORING TO ENSURE WE ARRIVED AT ZZZ1 WITH SUFFICIENT/LEGAL FUEL.