Airworthiness Directives; Hughes Helicopters, Inc., and McDonnell Douglas Helicopter Systems (Type Certificate Is Currently Held by MD Helicopters, Inc.) Helicopters

We are adopting a new airworthiness directive (AD) for MD Helicopters, Inc. (MDHI) Model 369D, 369E, 369F, and 369FF helicopters with certain serial-numbered tailboom assemblies. This AD requires measuring the distance between aft longeron rivets and the outboard edge of frame rings. If the distance is too short to ensure a safe flight, the AD requires installing a doubler. This AD was prompted by the discovery of short-edge margin conditions on two tailboom assemblies. The actions are intended to detect a short-edge margin condition, prevent failure of the tailboom and loss of control of the helicopter.