Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Learjet Model 23, 24, 25, 35, and 36 airplanes. The existing 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 proposed AD would require 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 would end the existing repetitive inspections. This proposed AD is prompted by the results of numerous continual inspections, and the approval of a new, improved flapper and flapper assembly. We are proposing 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.