Airworthiness Directives; Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, 25F, 28, 29, 31, 31A, 35, 35A (C-21A), and 36 Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, 25F, 28, 29, 31, 31A, 35, 35A (C- 21A), and 36 airplanes. This AD requires a one-time inspection of the center ball of the aileron control cable or cables for a defective swage, and corrective actions if necessary. This AD is prompted by a report indicating that an aileron cable failed on one affected airplane when the cable underwent a tension check. We are issuing this AD to prevent severe weakening of the aileron cable, and consequent reduced controllability of the airplane.