AD 2022-15-06 Prompted By High Electrical Resistance Within The Gust Suppression Sensor (GSS) Transorb Modules

The FAA is adopting a new airworthiness directive (AD) for all The Boeing Company Model 777 airplanes.

This AD was prompted by high electrical resistance within the gust suppression sensor (GSS) transorb modules due to corrosion on the transorb module threads. This AD requires disconnecting the connectors and capping and stowing the wires that had been attached to the affected transorb modules. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective August 18, 2022.

Supplementary Information: During scheduled maintenance inspection, high electrical resistance was found across the GSS transorb modules. The most likely cause of the high resistance is corrosion over time of the transorb threads. High electrical resistance in both transorb modules, if not addressed, can result in two actuator control electronics (ACEs), which are part of the flight control system, being exposed to damaging lightning transient voltages in excess of the qualification levels, potentially inducing erroneous or oscillatory outputs to flight control surfaces, which could result in loss of control of the airplane. The FAA is issuing this AD to address the unsafe condition on these products.  The gust suppression function on the Boeing Model 777 airplanes is a non-essential feature of the essential flight control system. The gust suppression function provides a minor improvement to ride quality during lateral wind gusts at low airspeeds. The actions required by this AD disable the non-essential gust suppression function, which does not affect the safety of flight.

FMI: www.regulations.gov