Robinson Helicopter Company RTR 660, Maintenance Manual

Page: 211 / 542

20-30 Torque Requirements
A. Tool Calibration
Dimensions and tolerances given in this manual are critical. Calibrate measuring tools per
manufacturers recommendation at least once a year, when tool is dropped, misused, or
calibration is suspect. This includes torque wrenches, micrometers, calipers, dial indicators,
and spring scales.
WARNING
Proper torque is critical. Always use calibrated wrenches and
undamaged, properly lubricated (where applicable) hardware.
Ensure clamping surfaces are clean, and clamp only bare metal
or wet-primed surfaces. Improper torque or dirty or painted
clamping surfaces may result in loss of clamp-up, hardware or
part damage, and premature failure.
B. Torque Value
Torque fasteners to standard dry values listed in Section 20-32 unless otherwise specified.
If torque is applied by rotating bolt, increase torque value by 10% to account for higher
friction at bolthead and shank.
For example, the torque wrench setting for an NAS1305 bolt used with a NAS1068 nutplate
is determined as follows:
NAS1305 bolt (5 indicates 5/16 inch size) dry torque per Section 20-32 240 in.-lb
Add 10% because torque must be applied at bolt head + 24 in.-lb
Torque wrench setting 264 in.-lb
C. Secondary Locking Mechanism
A secondary locking mechanism is required on all critical fasteners. B330 stamped nuts
(palnuts) serve as secondary locking mechanisms in most areas on the helicopter, and are
torqued per Section 20-32. The R66 Illustrated Parts Catalog (IPC) lists secondary locking
mechanisms for specific fasteners.
D. Critical Fastener
A critical fastener is one which, if removed or lost, would jeopardize safe operation of the
helicopter. This includes joints in the primary control system, and non-fail-safe structural
joints in the airframe, landing gear, and drive system.
WARNING
Assembly of flight controls is critical and requires inspection
by a qualified person. If a second person is not available,
RHC recommends the installer take a 5-minute break prior to
inspecting flight control connections he has assembled.
25 OCT 2010 R66 Maintenance Manual Chapter 20 Standard Practices
Page 20.3