The US Federal Aviation Administration (FAA) has announced a new airworthiness directive (AD) affecting certain Gulfstream Aerospace Corporation Model GVII-G500 and GVII-G600 airplanes. This action follows a concerning report of a failed rear engine mount, discovered during a routine preflight walk-around, which revealed visible engine misalignment.
The new directive mandates the inspection of engine mount points within the pylons and engine nacelles for non-conforming hardware installation. It also requires necessary repairs and updates to the aircraft maintenance manual (AMM) to include revised procedures for engine removal and installation. The objective is to address and mitigate potential unsafe conditions in these aircraft.
On January 31, 2024, a partially disengaged rear engine mount was detected on an in-service Model GVII-G600 airplane. The flight crew observed misalignment in the pylon area near the thrust reverser. Further inspection revealed that the upper, aft engine mount fastener had nearly migrated out of position. This issue was traced to the absence of a secondary locking device (cotter pin), leading to the separation of the retaining nut from the strut attachment bolt.
The investigation found that during a post-production engine removal and installation, the required cotter pin was not installed, and the bolt and nut were not secured properly. This resulted from maintenance personnel not fully complying with AMM procedures and seeking assistance from production engine installation staff.
Subsequent evaluations by Gulfstream revealed additional non-conforming engine mount installations. Although these were not critical, they highlighted quality control issues in both production and in-service installations.
The FAA’s investigation uncovered discrepancies in production and AMM procedures, including missing hardware details and inconsistent graphics, which could lead to misinterpretation during maintenance. The directive affects 247 aircraft registered in the US.