AD 2021-18-17 Adds A New Requirement To Update The Version Of The FCC OPS If Necessary

The FAA is superseding Airworthiness Directive (AD) 2012-21-08, which applied to certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes.

AD 2012-21-08 required inspecting for part numbers of the operational program software (OPS) of the flight control computers (FCCs) and installing and testing an updated version of the FCC OPS. This AD was prompted by reports that during autopilot coupled instrument landing system (ILS) approaches, the airplane did not capture or track the glideslope correctly. This AD retains the requirement to inspect for part numbers of the OPS of the FCCs, and adds a new requirement to update the version of the FCC OPS if necessary. This AD also expands the applicability to include The Boeing Company Model 737-900ER series airplanes. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective December 20, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2012-21-08, Amendment 39-17224 (77 FR 64711, October 23, 2012) (AD 2012-21-08). AD 2012-21-08 applied to certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. The NPRM published in the Federal Register on February 27, 2020 (85 FR 11319). The NPRM was prompted by reports that during autopilot coupled ILS approaches, the airplane did not capture or track the glideslope correctly. In the NPRM, the FAA proposed to continue to require inspecting for part numbers of the OPS of the FCCs, and to add a new requirement to update the version of the FCC OPS if necessary. The NPRM also proposed to expand the applicability to include The Boeing Company Model 737-900ER series airplanes. The FAA is issuing this AD to address the glideslope capture problem, which could allow the airplane to descend below the glideslope beam and result in controlled flight into terrain on airplanes that do not have the upgraded FCC OPS installed.

FMI: www.regulations.gov