Summary
We are revising an earlier proposed airworthiness directive (AD) for all Airbus Model A300 B4-603, B4-620, B4-622, B4-605R, B4- 622R, F4-605R, F4-622R, and C4-605R variant F airplanes. The NPRM proposed to require repetitive detailed inspections of the lower frame fittings, related investigative actions, and corrective actions if necessary. The NPRM was prompted by reports of cracks in the frame base fittings connecting the frame lower positions to the center wing box. This action revises the NPRM by replacing the proposed requirements with new repetitive detailed inspections for cracking of the lower frame fittings of the frame foot, and replacement with a new frame foot if cracking is found. This action also provides optional terminating action for the repetitive inspections. We are proposing this supplemental NPRM (SNPRM) to detect and correct cracking of the lower frame fittings, which could result in reduced structural integrity of the airplane. Since these actions imposean additional burden over those proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.