Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Learjet Inc. Model 45 airplanes. The existing 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. The existing 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 proposed AD would require replacing the left engine fuel and hydraulic tubing and installing a tubing support channel, which would terminate the repetitive inspections required in the existing AD. This proposed AD also removes airplanes from the applicability. This proposed AD results from reports of chafed hydraulic tubes in the left-hand engine. We are proposing this AD to detect and correct 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.