Helicopter Structural Parts-Namely, Airframe; Landing Gear; Main and Tail Rotors; Rotor Drive Systems Comprising a Transmission, an Engine-to-Transmission Coupling Drive Train, and a Transmission-to-Rotor Coupling Drive Train; Rotor Blade Pitch Controls Comprising a Swashplate, Swashplate Positioners, and Swashplate-to-Blade Pitch Change Rods, and Parts of Each