An airworthiness directive requiring replacement of Shadin ADC-2000 computers affects only aircraft owners with “Quick Start” models of the Chelton FlightLogic cockpit or those who participated in Alaska’s Capstone project. The AD, effective January 23, was prompted by the discovery of potential errors in some units that could cause them to display incorrect altitude information. Following a product recall last summer, Shadin Avionics said it has replaced or repaired the majority of the 350 potentially affected units sold.