AD 99-20-11 64 FR 52424

This amendment adopts a new airworthiness directive (AD) that applies to certain Burkhart Grob Luft-Und Raumfahrt GmbH & CO KG (Grob) Models G103 TWIN II and G103A TWIN II ACRO sailplanes. This AD requires accomplishing preflight checks of the fastening (knurled) nut at the rear control stick for cracks, and replacing the nut with one made of stainless steel either immediately or at a certain time period depending on whether a crack(s) is found. The checks are no longer required after the knurled nut is replaced. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Germany. The actions specified by this AD are intended to prevent the inability to use the rear control stick because of a cracked knurled nut, which could result in loss of control of the sailplane during flight instruction operations.