The FAA yesterday issued an Airworthiness Directive for all Bombardier Challenger business jets, as well as the derivative CRJ100 and 440 regional jets, that requires revising the aircraft flight manuals to modify the cold-weather operations limitations and include additional limitations and procedures. “This AD results from reports of uncommanded roll during takeoff,” the FAA said. “We are issuing this AD to prevent possible loss of control on takeoff resulting from even small amounts of frost, ice, snow or slush on the wing leading edges or forward upper wing surfaces.” The directive, which supersedes an AD issued in February 2005 regarding the same issue, becomes effective April 21. According to the FAA, the presence of any frost, ice, snow or slush on the Challenger/CRJ’s wing leading edges or forward upper wing surfaces “can cause an adverse change in the stall speeds, stall characteristics and the protection provided by the stall protection system.” At least three Challenger takeoff accidents–including the November 2004 crash of a Challenger 601 in Montrose, Colo., that killed NBC sports executive Dick Ebersol’s 14-year-old son–have been attributed to wing contamination.