AD 2021-05-11 Required Deactivating The Spoiler Control Module (SCM) Relays

The FAA is superseding Airworthiness Directive (AD) 2017-26-10, which applied to certain The Boeing Company Model 757 airplanes. AD 2017-26-10 required deactivating the spoiler control module (SCM) relays and capping and stowing the associated wiring on certain airplanes.

This AD requires repetitive operational tests of the spoiler inhibit function. For certain airplanes, this AD requires installing a new relay bracket assembly, making changes to the wire bundles for certain SCMs, installing new SCMs, measuring the clearance between a wire bundle and the top of the new relay bracket assembly, and applicable on-condition actions. For a certain other airplane, this AD requires changing certain wire bundles. This AD was prompted by reports of unwanted lateral oscillations during landing operations, and the development of wiring changes for certain SCMs, which will improve the lateral handling qualities of the airplane during approach and landing. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective April 19, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2017-26-10, Amendment 39-19141 (82 FR 61675, December 29, 2017) (AD 2017-26-10). AD 2017-26-10 applied to certain The Boeing Company Model 757 airplanes. The NPRM published in the Federal Register on October 13, 2020 (85 FR 64419). The NPRM was prompted by reports of unwanted lateral oscillations during landing operations, and the development of wiring changes for certain SCMs, which will improve the lateral handling qualities of the airplane during approach and landing. The NPRM proposed to require repetitive operational tests of the spoiler inhibit function. For certain airplanes, the NPRM proposed to require installing a new relay bracket assembly, making changes to the wire bundles for certain SCMs, installing new SCMs, measuring the clearance between a wire bundle and the top of the new relay bracket assembly, and applicable oncondition actions. For a certain other airplane, the NPRM proposed to require changing certain wire bundles. The FAA is issuing this AD to address unwanted lateral oscillations during landing operations, which could cause over-control of the airplane and subsequent lateral pilot induced oscillation, which could affect continued safe flight and landing.

FMI: www.regulations.gov