TM 1-1520-264-23
The main rotor head assembly is attached to the main drive shaft and static mast and provides mounting points for the
scissors and pitch change links. The main rotor head assembly transfers flight loads from the main rotor assembly to the
static mast, into the airframe. The main rotor head assembly requires no periodic lubrication.
The main rotor blade assemblies are rotating airfoils with swept tips that are constructed of stainless steel and fiberglass.
Each blade attaches to the main rotor head assembly by a lead-lag link and blade attachment pin.
The four lead-lag links are titanium mounts that provide a mounting point for each of the main rotor blade assemblies.
The four blade attachment pins are steel pins that attach to each of the lead-lag links to secure each main rotor blade
assembly to the main rotor head assembly.
The tail rotor assembly is installed on the tail rotor gearbox output shaft. The tail rotor assembly is a two-armed,
teetering assembly that provides attachment points for the four tail rotor blade assemblies. The tail rotor head assembly
provides a means to drive the tail rotor blade assemblies in a clockwise rotation providing feathering anti-torque control
for the helicopter. The tail rotor head assembly attaches to the tail gearbox output shaft and static support, providing
mounting points for the four pitch change links. The tail rotor head assembly transfers flight loads from the tail rotor
assembly to the static support, into the airframe.
The four tail rotor blade assemblies are rotating airfoils that are constructed of aluminum. Each tail rotor blade assembly
is attached to the tail rotor head assembly by a preload indicating washer, bolt, and nut combination.
1.2.2 Drive System. The main transmission assembly combines and reduces rpm from both engine nose gearboxes and
inputs usable engine power through the input clutch assemblies to the main rotor drive shaft and the main rotor head. It
is mounted on the main rotor static mast support directly below the main rotor static mast. Primary and accessory gear
trains are in the transmission housing and accessory drive housing assembly. They provide separate outputs for the
main rotor, tail rotor, transmission oil pumps, accessories, and rotor brake.
The main transmission assembly directs power from the auxiliary power unit to drive the accessories when the engines
are not operating. It also provides accessory drives for two AC generators, two hydraulic pumps, an accessory drive oil
pump, and a shaft-driven compressor. It provides mounting for accessory drive oil filters, two oil pressure switches, chip
detector/temperature switches, and an oil level sight indicator. During normal operation, the main transmission drives the
shaft-driven compressor, the accessory drive lubrication pump, two AC generators, two hydraulic pumps, tail rotor output
shaft, and the main rotor drive shaft.
The drive system consists of engine nose gearbox assemblies 1 and 2, the main transmission assembly, the intermediate
gearbox assembly, the tail rotor gearbox assembly, and the drive shaft assembly (7 drive shafts). The drive system
changes the angle of drive and converts the output rpm of the engines into usable power to drive the main rotor system,
tail rotor system, and the gear driven accessories.
1.2.3 Airframe and Landing Gear System. The airframe provides mounting points for the helicopter systems/subsystems
and components. The design features incorporated into the airframe increase both aircraft and aircrew survivability. The
airframe is a one-piece integral design that has the strength to withstand compression, tension, torsion, and shearing
force loads that exceed the required design limits throughout the entire flight envelope.
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