Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for certain Short Brothers Model SD3-60, SD3-SHERPA, and SD3-60 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 proposed AD would add airplanes to the applicability; add repetitive inspections and corrective actions; and provide an optional action that would end the repetitive inspections. This proposed AD is prompted by reports of cracked aluminum alloy gland nuts that had been inspected previously using the existing AD. We are proposing this AD to prevent failure of the aluminum alloy gland nut on the MLG shock absorber, which could cause the MLG to collapse.