Airworthiness Directives; Boeing Model 747-100, 747-200, and 747- SP Series Airplanes and Military Type E-4B Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-100, -200, and 747-SP series airplanes and military type E-4B airplanes, that requires repetitive inspections to detect cracking of the wing front spar web, and repair of cracked structure. This amendment also provides for optional terminating action for the repetitive inspection requirements. This amendment is prompted by reports indicating that fatigue cracks were found on the aft surface of the wing front spar web. The actions specified by this AD are intended to detect and correct such fatigue cracking, which could result in a fuel leak, and consequent increased risk of a fire.