Shadin ADC-2000 Computers Subject of AD

An FAA airworthiness directive, effective January 26, mandates replacement of a batch of Shadin ADC-2000 air-data computers installed in about 450 aircraft, including a handful of King Airs, Citation 501s and Conquests. The AD was prompted by the discovery of potential errors in some units that could cause them to display incorrect altitude information on their Chelton FlightLogic EFIS displays. Air-data computers are permitted a maximum of 25 feet of altitude error on the ground, but tests showed the effected Shadin units potentially could show erroneous deviations of 100 to 8,000 feet, according to the FAA. Shadin will reimburse owner/operators for cost of a new ADC, as well as for labor to remove and replace the ADC and for shipping.