Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 707 airplanes and Model 720 and 720B series airplanes. This proposed AD would require identifying the material used in the elevator hinge support fittings of the horizontal stabilizer trailing edge, doing repetitive detailed inspections for cracking of the fittings and corrective actions if necessary, and doing an eventual terminating action. This proposed AD results from a report that stress corrosion cracking of the elevator hinge support fittings has been discovered on several Model 707 airplanes. We are proposing this AD to prevent cracking of the elevator hinge support fittings, which could reduce the elevator support stiffness and lead to in-flight airframe vibration, consequent damage to the elevator and horizontal stabilizer, and reduced controllability of the airplane.