Airworthiness Directives; Boeing Model 707 and 720 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 707 and 720 series airplanes, that requires inspection of the bolt forward of the wing front spar upper chord on the overwing support fittings of the inboard and outboard nacelle struts to verify that BACB30US type bolts are installed. If any other type of bolt is found, this amendment requires replacement with a new BACB30US type bolt. This action is necessary to prevent separation of the engine from the airplane due to stress corrosion cracking and consequent fracturing of the bolts. This action is intended to address the identified unsafe condition.