Airworthiness Directives; Learjet Inc. Model 45 Airplanes

We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires, for certain airplanes, repetitive inspections for chafing and other damage of the case drain tube from the hydraulic pump case installed on the left-hand engine, and corrective action if necessary. That AD also requires, for all airplanes, repetitive inspections for discrepancies of the left engine's nacelle tubing, repetitive inspections for evidence of fluid leakage within the left engine accessory compartment, and corrective actions if necessary. This new AD also requires replacing the left engine fuel and hydraulic tubing and installing a tubing support channel, which terminates the repetitive inspections required in the existing AD. This new AD also removes airplanes from the applicability. This AD was prompted by reports of chafed hydraulic tubes in the left- hand engine. We are issuing this AD to prevent chafed hydraulic tubes in the left-hand engine and consequent hydraulic tube failure and uncontrolled loss of flammable fluid within the engine cowling, which could result in a fire in the engine nacelle and loss of control of the airplane.