The FAA has issued an Airworthiness Directive for the Gulfstream Aerospace Galaxy and Gulfstream 200, citing cracked nuts found on the aircraft’s production line during routine post-assembly inspection. Investigation revealed that the cracks resulted from hydrogen embrittlement combined with high hardness. Cracked nuts were found in multiple locations, including aileron fittings, rudder tab assembly and mounting structure for power drive units, which could result in failure and consequent reduced controllability or reduced structural capability of the airplane.