TM 1-1520-253-23
NOTE
The following paragraphs describe the type of construction and materials used in the
manufacture of the major CH/MH-47 helicopter components.
1.2.1 Rotor Group. The rotary-wing heads transmit torque from the forward and aft transmission rotor shafts to the
rotary-wing blades. Each rotary-wing head and controls consist of a rotor hub, three pitch-varying housings, three pitch-
varying shafts with droop stops, three shock absorbers, two swashplates, three pitch links, a drive collar and drive arms,
and a weather protective cover. The rotary-wing controls transmit cockpit control movements to the blades.
Three rotary-wing blades are attached to the forward and aft rotary-wing heads. The aft blades turn clockwise and the
forward blades turn counterclockwise, when viewed from above. The rotary-wing blades are composite structures. The
spar is constructed from torsion straps consisting of continuous fiberglass elements that begin at the blade tip, wrap
around the vertical pin bore, and return to the tip. The straps are formed in a D-shape and wrapped with several layers of
cross-ply fiberglass. The leading edge of the spar is formed around a permanent balance weight with tubes at the tip of
the spar for tracking weights. The titanium leading edge nose cap is bonded to the spar with a nickel erosion cap bonded
over the outboard 54 inches. The blade body is Nomex honeycomb core covered by laminated cross-ply fiberglass
skins. The skins and core are bonded to the trailing edge of the spar and a wedge of fiberglass closes out the entire
trailing edge. Wire mesh is installed on the surface of the skin for lightning protection, reaching to the trailing edge of the
blade at the trim tab and at the tip. Kevlar filament windings secure the shock absorber bracket to the spar. Replaceable
composite sleeves line the vertical pin bores of the blade.
1.2.2 Transmission/Drivetrain Group. Five transmissions make up the transmission group. An engine transmission is
mounted on the front of each of the two engines. A splined quill shaft transmits torque from the engines to the engine
transmissions. Output torque from each engine transmission is delivered through an engine driveshaft to the combining
transmission which, in turn, transmits it through driveshafts to the forward and aft transmissions. The forward and aft
transmissions drive vertical rotor shafts that are splined to the rotary-wing heads to drive the rotor blades.
a. The cockpit section contains the pilot and copilot seats and controls. Three dynamic absorbers are mounted in
the cockpit; one in the nose and two below the floor under the seats. The absorbers automatically adjust to lower
vibrations in the helicopter. A jettisonable door is next to each pilot's seat with a main personnel door at the aft right side
of the cockpit section.
b. The cabin fuselage section can be fitted to carry troops, litters, cargo, or any combination of the three. The cabin
floor consists of 12 removable panels made of riveted sections of magnesium alloy. These panels are set between five
tie-down beams and tie-down rings installed on each tie-down beam. A rescue hatch door of sandwich honeycomb
construction is in the center of the floor. A tunnel along the top of the cabin houses the driveshafting and flight controls.
The tunnel consists of six honeycomb covers that hinge open for access to the housed components. A walkway at the
right of the tunnel runs the length of the cabin. External pods on either side of the fuselage section contain fuel tanks.
The forward end of each pod houses components of both the electronic and electrical systems. A hinged panel in each
pod provides access to the forward landing gear.
