Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 35, 36, and 55 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to all Learjet Model 23, 24, 25, 28, 29, 31, 35, 36, and 55 series airplanes. This action requires an inspection to determine if tires on the main landing gear have a certain part number and certain serial numbers, and replacement with a tire having a part number that does not contain those certain serial numbers, if necessary. This action is necessary to prevent separation of the tread of main landing gear tires, which could cause damage to the structure and major systems of the airplane, and consequent reduced controllability of the airplane on the ground during takeoff and landing. This action is intended to address the identified unsafe condition.