Airworthiness Directives; Learjet, Inc. Airplanes

We propose to adopt a new airworthiness directive (AD) for certain Learjet, Inc. Models 28, 29, 31, 31A, 35, 35A, 36, 36A, 55, 55B, 55C, and 60 airplanes. This proposed AD was prompted by fatigue cracks initiating in the flap support structure due to repetitive flap loads, which has caused flap nose roller support bracket failure. This proposed AD would require replacement of the flap nose roller fitting, nose roller support bracket, and adjacent rib support structure with more robust components. We are proposing this AD to address the unsafe condition on these products.