Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C-21A), 36, and 36A Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Learjet Model 31, 31A, 35, 35A (C-21A), 36, and 36A airplanes, that requires modification of the drag angles of the fuselage and engine pylons to gain access to the shear webs of the forward engine beams; repetitive inspections of the shear webs of the forward engine beams for cracks; follow-on actions; and modification/ repair of the shear webs of the forward engine beams, as necessary, which terminates the repetitive inspections. This action is necessary to prevent significant structural damage to the engine pylons, possible separation of the engines from the fuselage, and consequent reduced controllability of the airplane. This action is intended to address the identified unsafe condition.