PROBABLE ELECTRONIC SPIKE WHEN ELECTRICAL PWR WAS TRANSFERRING FROM THE APU TO THE GENERATOR; GAVE MOMENTARY ERRONEOUS HEADING INFO. FLC NOTICED DISCREPANCY AND USED THE OTHER FMS FOR NAV.

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WE WERE RELEASED FOR DEP OFF OF RWY 04 AT BHB AND CLRED DIRECT ALB. CAPT WAS NAVING OFF OF L SIDE FMS WHICH SHOWED AN ERRONEOUS EASTERLY HEADING WHICH WE TURNED TO AND PROCEEDED ON THAT HEADING FOR APPROX 2-3 MI BEFORE REALIZING AND TURNING BACK ONTO COURSE. AFTER TURNING ON COURSE DIRECT TO ALB WE NAVIGATED OFF OF THE R SIDE FMS WHILE THE L FMS FINALLY DEPICTED CORRECT COURSE INFO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: ACFT TYPE WAS CHALLENGER 601-3A. THERE ARE 2 FMS ON THE ACFT AND USUALLY THE HEADING INFO CAN BE TRANSFERRED BTWN THE TWO; IE; THE FO SETTING THE HEADING AND TRANSFERRING TO THE CAPT SIDE. IN THIS CASE; THE HEADING INFO WAS IN ERROR AND THE RPTR CAN ONLY ATTRIBUTE IT TO AN ELECTRONIC GLITCH; POSSIBLY DUE TO THE APU BEING SHUT DOWN JUST PRIOR TO THE ERRONEOUS INFO. WHEN THE APU WAS SHUT DOWN THE PWR SOURCE TRANSFERRED ON THE CAPT FMS; AND IT IS ASSUMED THAT AN ELECTRONIC 'SPIKE' CAUSED THE ANOMALY. THE ERROR WAS NOTICED; AND NAV WAS CONTINUED USING THE R SIDE FMS. SHORTLY THEREAFTER; THE #1 WAS AGAIN ACCURATE.