Airworthiness Directives; Learjet Model 23, 24, 25, 35, and 36 Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Learjet Model 23, 24, 25, 35, and 36 airplanes. That AD currently requires repetitive inspections to detect deterioration of both flappers of the tip tank in each wing of the airplane, and various follow-on actions. The existing AD also requires replacing the flappers with new flappers, and repetitively performing certain other follow-on actions. This new AD requires an inspection of the flappers and flapper assemblies of the tip tank in each wing or a review of the airplane maintenance records to determine the part numbers, and replacement of certain flappers or flapper assemblies if necessary, which ends the existing repetitive inspections. This AD results from numerous continual inspections and the approval of a new, improved flapper and flapper assembly. We are issuing this AD to prevent significant reduction in the lateral control of the airplane due to imbalance of the fuel loads in the wings of the airplane.