Airworthiness Directives; Learjet Model 45 Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Learjet Model 45 airplanes, that currently requires repetitive application of grease to the rotating disk assembly of the nose landing gear (NLG) squat switch mechanism. This amendment requires replacement of the squat switch camrod of the NLG, which terminates the repetitive application; and also reduces the applicability of the existing AD. The actions specified by this AD are intended to prevent moisture contamination and subsequent formation of ice which could cause bending and damage of the squat switch assembly, driving the nose wheel to an uncommanded angle against the force of the steering system. This condition, if not corrected, could result in the airplane departing the runway at high speeds during landing. This action is intended to address the identified unsafe condition.