AD FAA-2007-27525

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 747 airplanes. That AD currently requires repetitive inspections to detect cracks and/or corrosion of the girt bar support fitting at certain main entry doors (MED), and repair or replacement of the support fitting. The existing AD also provides for various terminating actions for the repetitive inspections. This new AD requires the following additional actions: An inspection, for certain airplanes, for correct installation of square and conical washers in the girt bar support fitting; an inspection, for certain other airplanes, to determine if the washers are installed; and related investigative and corrective action if necessary. This AD results from a report that the square and conical washers may be installed incorrectly in the girt bar support fitting on airplanes on which the support fitting was repaired or replaced in accordance with the requirements of the existing AD. We are issuing this AD to detect and correct corrosion of the girt bar support fitting, which could result in separation of the escape slide from the lower door sill during deployment, and subsequently prevent proper operation of the escape slides at the main entry doors during an emergency. We are also issuing this AD to detect and correct incorrect installation of the square and conical washers in the girt bar support fitting, which could result in failure of the escape slide when deployed.