AD 2020-11-01 Updates The Software Of Each PFCAS Remote Electronics Unit (REU), Which Includes An Improvement To The LVDT

The FAA is adopting a new airworthiness directive (AD) for certain Gulfstream Aerospace Corporation (Gulfstream) Model GVI airplanes.

This AD was prompted by a report that the primary flight control actuation system (PFCAS) linear variable displacement transducer (LVDT) mechanical disconnect monitor may not trigger the disconnect of the affected control surfaces as required in the event of a control surface failure. This AD requires updating the software of each PFCAS remote electronics unit (REU), which includes an improvement to the LVDT. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective July 27, 2020.

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 certain Gulfstream Aerospace Corporation (Gulfstream) Model GVI airplanes. The NPRM published in the Federal Register on December 16, 2019 (84 FR 68363). The NPRM was prompted by a report from Gulfstream that the PFCAS LVDT mechanical disconnect monitor may not trigger the disconnect of the affected control surfaces as required in the event of a control surface failure.

The Model GVI flight control computer actuator LVDT disconnect monitor should disable the control surface for ailerons, elevators, and rudder in the event that one of those control surfaces fails. Gulfstream developed an REU software update that provides improvements to the LVDT of the PFCAS, which addresses the LVDT disconnect monitor problem.

This condition, if not addressed, could lead to spoiler hard-over or loss of structural integrity due to excessive surface deflection and result in loss of control of the airplane. The NPRM proposed to require updating the software of each PFCAS REU, which includes an improvement to the LVDT. The FAA is issuing this AD to address the unsafe condition on these products.

 FMI: www.regulations.gov