A software error in Honeywell flight management systems with NZ-2000 nav computers could cause sudden, un-annunciated shifts in computed position, according to an FAA airworthiness directive. Honeywell has identified 234 business jets (Challenger 601/604, Falcon 900, GIII/IV/V and Hawker 800/800XP/1000) that are affected by the AD (effective April 18), which requires adding corrective procedures to the aircraft flight manual. “We expect a TSO solution by mid- to late summer,” a spokesman told AIN. “We think from there we’ll be able to retrofit the fleet by the end of the year.”