AD 2021-06-04 Prompted By Notification Of Corrosion Present In Floor Beam Support Links

The FAA is adopting a new airworthiness directive (AD) for all Gulfstream Aerospace Corporation (Gulfstream) Model GV airplanes. This AD was prompted by notification of corrosion present in floor beam support links. This AD requires inspecting the right butt line 6 floor beam inboard support links and bushings for corrosion. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective May 4, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Gulfstream Model GV airplanes. The NPRM published in the Federal Register on December 10, 2020 (85 FR 79443). The NPRM was prompted by notification of a failed floor beam support link at right butt line (RBL) 6 on a Gulfstream Model GV airplane, resulting from seizure of the retaining sleeve and bushing at the lower attachment point due to undetected corrosion.

The floor beam support links at RBL 6, fuselage stations (FS) 499, 531, and 569.5 have a two-piece installation with straight bushings rather than spherical bearings in the inboard link lower end. Design of the support links allows floor beam movement when the cabin is pressurized. Seizure of the lower bushing will not allow the link assembly to move as designed, resulting in bending stress and potential failure of the link, which may compromise the integrity of the pressure vessel floor. Gulfstream determined that the procedures for the existing Aircraft Maintenance Manual (AMM) inspection do not reliably detect corrosion in the floor beam support link lower bushings. Accordingly, Gulfstream has revised the airworthiness limitation requirements to the AMM by adding a detailed inspection with an initial and repetitive inspections at intervals of 96 months and including references for removal and installation instructions for RBL 6 Floor Beam Support Links.

In the NPRM, the FAA proposed to require inspecting the right butt line 6 floor beam inboard support links and bushings for corrosion. The FAA is issuing this AD to prevent link failure, which can compromise the integrity of the pressure vessel floor and lead to loss of pressurization of the airplane.

FMI: www.regulations.gov