TM 1-1520-238-T-4
6–3
6–2
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont)
6–2
a. Engine NGB Assemblies.
The engine NGB assemblies (fig. 6–2) are connected to the main
transmission through input drive shafts 1 and 2. The engine NGBs change the drive angle and reduce the engine
rpm output to the main transmission. One engine NGB is mounted on the forward end of each engine nacelle. The
input shaft of each NGB is splined to the output shaft of the engine. The engine NGB assembly consists of an
engine NGB housing, NGB cooling fan, and lubrication system.
(1) The engine NGB housing is completely finned for cooling. The housing supports the major components
of the engine NGB assembly. Each engine NGB has a self–contained oil system. A sight indicator, for checking
the oil level in the engine NGB, is provided in the engine NGB housing.
(2) The engine NGB cooling fan mounts to the engine NGB fan mounting adapter. The mounting adapter is
a round steel ring with five access holes to aid in removing and installing input drive shaft coupling retaining bolts.
(3) The lubrication system is self–contained with the lower housing forming the oil sump. Each engine
NGB input and output shaft has an oil–soaked felt disc for emergency lubrication.
ENGINE NGB
(TYPICAL)
INPUT DRIVE
SHAFT (TYPICAL)
TRANSMISSION
ASSEMBLY
SIGHT INDICATOR
OIL LEVEL
M58–128
MAIN
NGB
COOLING FAN
ENGINE NGB
HOUSING
Figure 6–2.
Engine NGB Assembly
b. Main Transmission Assembly.
The main transmission assembly (fig. 6–3) combines and reduces rpm
from both engine NGBs 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.
(1) The main transmission assembly directs power from the APU 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.
