Airworthiness Directives; Short Brothers Model SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Short Brothers Model SD3-60 and SD3- SHERPA series airplanes. That AD currently requires a one-time inspection to detect cracks and/or corrosion of the gland nut on the shock absorber of the main landing gear (MLG), and follow-on actions. That AD also requires repair or replacement of any cracked/corroded gland nut with a new nut. This new AD adds airplanes to the applicability; adds repetitive inspections and corrective actions; and provides an optional action that ends the repetitive inspections. This AD is prompted by reports of cracked aluminum alloy gland nuts that had been inspected previously using the existing AD. We are issuing this AD to prevent failure of the aluminum alloy gland nut on the MLG shock absorber, which could cause the MLG to collapse.