AD NUMBER: 2018-23-09

PRODUCT: All Boeing Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes.

ACTION: Final Rule.

SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2016-13-16, which applied to the aircraft listed above.

AD 2016-13-16 required an inspection or records check to determine if affected horizontal stabilizers are installed, related investigative actions, and, for affected horizontal stabilizers, repetitive inspections for any crack of the horizontal stabilizer rear spar upper chord, and corrective action if necessary.

This AD requires retaining the requirements of AD 2016-13-16, with revised service information that clarifies the inspection areas and serial number information of the horizontal stabilizer.

This AD was prompted by reports of a manufacturing oversight, in which a supplier omitted the required protective finish on certain bushings installed in the rear spar upper chord on horizontal stabilizers, which could lead to galvanic corrosion and consequent cracking of the rear spar upper chord.

DATES: This AD is effective December 19, 2018.

COST: The FAA estimates that this AD affects 1,748 airplanes of U.S. registry. Operators may incur the following costs in order to comply with this AD:

• Inspection or records check to determine the serial number of the horizontal stabilizer - 1 work-hour × $85 per hour = $85 per aircraft.
• HFEC inspection (horizontal stabilizer with affected serial number) 6 work-hour × $85 = $510 per aircraft.

FMI: AD