Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 737 series airplanes. The existing AD currently requires inspection of the elevator tab inboard hinge support structure to detect fatigue cracking and corrective action if necessary. That AD also provides an optional terminating action. This proposed AD would add airplanes to the applicability and would require new repetitive inspections. For airplanes having elevators with laminated rear spars, this proposed AD would require repetitive inspections for interlaminar corrosion, delamination, or disbonding in the rear spar, repetitive inspections for cracking in the spar web, and repair including related investigative/corrective actions if necessary. For airplanes having elevators with solid rear spars, this proposed AD would require repetitive inspections for cracking in the spar web and repair including related investigative/corrective actions if necessary. This proposedAD results from reports of cracks in the elevator rear spar web at the tab hinge bracket locations. We are proposing this AD to detect and correct cracking, corrosion, interlaminar corrosion, delamination, and disbonding in the elevator rear spar, which may reduce elevator stiffness and lead to in-flight vibration. In-flight vibration may lead to elevator and horizontal stabilizer damage and reduced controllability of the airplane.