FAA has issued airworthiness directive 2021-03-02 for certain GE CF6-80C2A1s, -80C2A2s, -80C2A3s, -80C2A5s, -80C2A5F, -80C2A8s, -80C2B1s, -80C2B1Fs, -80C2B2s, -80C2B2Fs, -80C2B4s, -80C2B4Fs, -80C2B5Fs, -80C2B6s, -80C2B6Fs, -80C2B6FAs, -80C2B7F, -80C2B8Fs and -80C2D1Fs, requiring initial and repetitive shim checks of the hydro-mechanical unit, main engine control idler adapter on the accessory gearbox assembly and, depending on results, possible replacement of the inserts on the idler adapter or, as a terminating action, a protrusion check and a pull-out test, and the replacement of inserts on the idler adapter that fail either test, effective March 31, 2021.