Airworthiness Directives; Learjet Inc. Airplanes

We are superseding Airworthiness Directive (AD) 2003-19-11 for certain Learjet Inc. Model 60 airplanes. AD 2003-19-11 required determining if a certain fuel crossflow tube is installed; and follow- on/corrective actions, as applicable. This new AD requires retaining all actions in AD 2003-19-11, and it also requires determining if a certain fuel crossflow tube is installed, performing repetitive measurements of the fuel crossflow tube and surrounding valves and cables, and doing corrective actions if necessary. In addition, this new AD expands the applicability of AD 2003-19-11. This AD was prompted by a report that airplanes produced since 2003 might also be subject to the unsafe condition; and that the minimum allowable clearance is not established in the airplane maintenance information. We are issuing this AD to prevent chafing and consequent failure of the fuel crossflow tube due to inadequate clearance between the tube and the flight control cables, which could result in loss of fuel from one fuel tank during normal operating conditions or loss of fuel from both main fuel tanks during fuel cross-feeding operations.