Airworthiness Directives; Gulfstream Model GIV-X, GV, and GV-SP Series Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Gulfstream Model GIV-X, GV, and GV-SP series airplanes. This AD requires revising the airplane flight manuals (AFMs) of those airplanes, and doing repetitive functional checks of the forward water drain/supply valves and applicable corrective actions. This AD also provides for optional terminating action for the repetitive functional checks. This AD results from reports of failed forward water drain/ supply valves on numerous airplanes, and reports of ice striking the wing-to-body fairings and engine nose cowls of several airplanes. We are issuing this AD to prevent leakage from failed water drain/supply valves allowing the build-up of ice on the airplane, which could separate and strike the airplane structure aft of the failed valves; become ingested by a propulsion engine; or become a hazard to persons or property on the ground.