Airworthiness Directives; Boeing Model 747-100, -100B, -100B SUD, -200B, -200C, -300, -400, and -400D Series Airplanes; and Model 747SR Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 747 series airplanes. That AD currently requires a one-time inspection to determine the material type of the stop support fittings of the main entry doors (MEDs). That AD also currently requires repetitive detailed inspections to detect cracks of certain stop support fittings of the MEDs, and replacement of any cracked stop support fitting with a certain new stop support fitting. This new AD adds new inspections, and replacement if necessary, of the stop support fittings of MED 3, and adds airplanes to the applicability. This AD is prompted by reports of MED 3 having certain stop support fittings that are susceptible to stress corrosion cracking. We are issuing this AD to detect and correct stress corrosion cracking of the stop support fittings of the MEDs, which could result in damage to the adjacent forward edge frame of the door and consequent loss of a MED and rapid decompression of the airplane.