Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 707 airplanes, and Model 720 and 720B series airplanes. The existing AD currently requires repetitive detailed inspections to detect cracks and corrosion on any existing repairs and at certain body stations (STA) of the visible surfaces of the wing to body terminal fittings including the web, flanges, and ribs; and applicable related investigative and corrective actions. This proposed AD would retain the requirements of the existing AD and would require repetitive ultrasonic inspections to detect any stress corrosion cracks within the outboard flange of the left and right body terminal fittings at STA 820, and related investigative and corrective actions if necessary. This proposed AD would also provide for an optional terminating action for the repetitive inspections. This proposed AD also adds two airplanes to the applicability. This proposed AD results from reports ofcracks found in the wing to body terminal fittings during routine inspections. We are proposing this AD to detect and correct cracks and corrosion in the body terminal fittings above and below the floor, which could cause loss of support for the wing and could adversely affect the structural integrity of the airplane.