TM 1-1520-238-T-4
6–7
6–2
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont)
6–2
e. Drive Shaft Assembly.
The drive shaft assembly (fig. 6–6) links the helicopter drive system gearboxes
to the main transmission. The system consists of input drive shafts 1 and 2, drive shafts 3, 4, 5 and 6, forward and
aft bearing hanger assemblies, damper assemblies, anti–flail assemblies, and APU drive shaft 7.
(1) Input drive shafts 1 and 2 are interchangeable and connect the engine NGBs to the main transmission
assembly. The input drive shafts have a flange at each end with five equally–spaced floating anchor nuts. Flexible
couplings, attached to each end of the shaft, incorporate an anti–flail bearing which supports the drive shaft
sections in position if the flexible couplings fail.
(2) Tail rotor drive shaft assemblies 3, 4, 5 and 6 connect the main transmission to the TGB assembly.
Flexible coupling assemblies on each end of the drive shafts mate with the main transmission assembly, two
hanger bearing assemblies, two gearbox assemblies, and the main rotor drive shaft. Drive shaft 3 is a short
section which connects to the main transmission and the forward hanger bearing assembly. Drive shafts 4 and 5
are joined by the aft hanger bearing assembly.
(3) Hanger bearing assemblies connect, support, and align drive shafts 3, 4, and 5. The forward hanger
bearing assembly is a rigid A–frame which supports the sealed bearing. The aft hanger bearing assembly is
semi–rigid consisting of a single support and a sealed bearing assembly. The support incorporates three spherical
bearings in the mount holes which mount the support to the bracket.
(4) Damper assemblies detune the natural frequencies of drive shaft 5 to allow them to rotate through
critical speeds. Spring–loaded dampers are installed on the drive shafts between the main transmission and the
IGB.
(5) Anti–flail assemblies hold drive shafts 4 and 5 in position if partial or full separation of the drive shaft
occurs. Anti–flail sleeves are installed on the drive shafts. They are between the main transmission and the IGB.
(6) APU drive shaft 7 transmits power from the APU to drive the accessory drive train. The APU drive shaft
7 has flexible couplings at each end.
(7) The main rotor drive shaft assembly, installed in the main rotor static mast, connects the main
transmission to the main rotor head. The main rotor drive shaft is a semi–floating drive shaft which accepts
torsional loads. The main rotor drive shaft is a tubular shaft with external splined steel forged couplings at each
end. The tube shears in the event of a gear train seizure. The drive shaft is splined to a steel drive plate that bolts
to the main rotor hub.
