18-72 Ground Checks
NOTE
Run-up and shutdown helicopter throughout procedure as
required per R66 Pilot's Operating Handbook (POH) Section 4.
NOTE
Use the following balancing procedures in conjunction with
approved equipment manufacturer’s balancing instructions.
WARNING
Fan shaft and engine shaft balancing equipment must be
removed for flight.
1. Prepare helicopter for fan shaft and engine shaft balance per § 18-71.
2. Configure balance equipment per manufacturer's instructions.
3. Ground run helicopter at 100% RPM (2114 fan shaft RPM and 6016 engine shaft
RPM). Verify cyclic stick and tail rotor pedals are in neutral position.
4. Determine vibration level per balance equipment manufacturer's instructions. Maximum
vibration allowance is 0.2 IPS (inches per second). If reading is over 0.2 IPS:
a. Fan Shaft: Refer to Figure 18-13. Adjust balance by selecting one or more
NAS1149D0463J, NAS1149F0432P, NAS1149F0463P, A214-3, or A141-14
washers as required and install under one nut of intermediate flex plate (tail rotor
driveline) fastener.
b. Engine Shaft: Refer to Figure 18-14. Adjust balance by selecting one or more
NAS1149D0463J, NAS1149F0432P, NAS1149F0463P, A214-3, or A141-14
washers as required and install under one nut of aft flex plate (engine driveline)
fastener. After first adjustment, if engine shaft does not respond correctly to
balance weight, verify TIR of F018 clutch’s housing is less than 0.004 inch
(rotate TR backwards by hand to rotate clutch housing) before making further
weight changes. If TIR exceeds limit, contact RHC Technical Support.
NOTE
If a large diameter washer is installed at a shaft flange, also
install one NAS1149F0432P washer against flange to prevent
flange damage (not required for flat flange). Additionally, an
NAS6604-5, -6, -7, or -8 bolt may be substituted for a bolt at
a flex plate fastener; verify thread engagement meets torque
requirements per § 20-30.
5. Adjust as required until reading is 0.2 IPS or less.
APR 2019 Chapter 18 Track and Balance Page 18.35
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