CHAPTER 63
MAIN ROTOR DRIVE SYSTEM
63-00 Description
The engine is mounted in a 37º nose-up attitude. A sprag-type overrunning clutch mates
directly to the splined engine power take-off (PTO) shaft. The clutch is connected to a shaft
with exible couplings at both ends to transmit power to the main gearbox. A ring and pinion
spiral bevel gearset at the main gearbox input reduces speed to tail rotor driveline RPM. A
second ring and pinion stage reduces speed from tail rotor driveline RPM to main rotor RPM.
The main gearbox is pressure lubricated. The oil is pumped through an airframe-mounted lter
and cooled by an oil cooler which receives its airow from the cooling fan. The main gearbox
also drives the ight control hydraulic pump.
63-10 Engine Shaft Weldment
Refer to R66 Illustrated Parts Catalog (IPC) Figures 63-1 and 63-3.
A. Removal
1. Remove tailcone cowling assembly per Section 53-23. Remove engine cowling assembly
per Section 53-21.
2. Remove filter and cage assemblies per Section 71-22.
3. Refer to Figure 63-1. Remove hardware securing F453-1 box assembly to F234-1
firewall.
4. Remove hardware securing forward A947-2 flex plate assembly to F910-1 (main gearbox)
yoke and F642-1 (engine) shaft weldment forward flange, noting hardware removed.
Remove flex plate, and temporarily suppport forward portion of shaft weldment.
5. Remove hardware securing shaft weldment to aft A947-2 flex plate assembly. Remove
support, then remove shaft weldment through main gearbox compartment.
B. Installation
1. Refer to Figure 63-1. Position F642-1 engine shaft weldment in helicopter, and install
hardware securing shaft weldment to aft A947-2 plate assembly. Standard torque nuts
and palnuts per Section 20-32, and torque stripe per Figure 5-1.
2. Shim engine driveline per Section 63-11.
3. Install hardware securing F453-1 box assembly to F234-1 firewall.
4. Verify 0.2 inch minimum clearance between shaft weldment and firewall grommet;
verify equal gap concentrically between shaft and box assembly hole edges. Adjust
F174-1 support weldment rod ends per Section 53-31 as required.
5. Install filter and cage assemblies per Section 71-22.
6. Install tailcone cowling assembly per Section 53-23. Install engine cowling assembly
per Section 53-21.
SEP 2012 R66 Maintenance Manual Chapter 63 Main Rotor Drive System Page 63.1
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