Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain McDonnell Douglas transport category airplanes. This proposed AD would require an initial ultrasonic inspection for cracks of the studbolts of the inboard and outboard hinge fittings of the left and right outboard flaps of the wings. Based on the inspection results, this proposed AD would also require doing repetitive ultrasonic inspections, replacing upper and/or lower studbolts with new or serviceable studbolts, doing a detailed inspection for corrosion of the upper studbolts, doing a magnetic particle inspection for cracks of studbolts, and changing the protection treatment; as applicable. This proposed AD is prompted by reports of corrosion and failures of the upper and lower studbolts of the outboard flaps inboard and outboard hinge fittings. We are proposing this AD to prevent corrosion and subsequent cracking of studbolts, which could result in failure of the flap hinge fittings and their possibleseparation from the wing rear spar, and consequent reduced controllability of the airplane.