the correct rotary-wing and rotary-rudder blade angles.
blade is PLUS and the pitch control rod decal shows
You must be sure that the flight controls are operating
the setting is zero, loosen the locknut. Lengthen the
under normal friction loads.
rod by rotating the tang counterclockwise. Keep
rotating the tang until it aligns (closest notch) with the
The use of rigging pins and other rigging aids
appropriate blade pretrack number on the upper scale
provide proper rigging and proper system operation.
of the lower decal. After adjusting the remainder of the
Each step outlined in the MIM should be carefully
pitch control rods, tighten the locknuts to the torque
performed.
specified in the MIMs. Safety wire the locknuts to the
Several quick rigging, cable adjustment, and
tang.
operational checks with related maintenance
You should perform a ground operational check.
precautions are found in the MIM. No attempt to
With the rotary-wing head engaged, operate the
duplicate this information is provided in this chapter.
engines at 100 percent. Check for vibrations in the
The MIM should be consulted before any maintenance
rotary-wing head. If vibrations occur and the
begins.
adjustable pitch control rods were properly adjusted,
At the completion of rigging, a flight test must be
use an alternate method of blade tracking. In this case,
performed by a qualified pilot. A flight check chart is
use a strobe blade tracker to check the blades under
provided by the MIM. The MIM lists the conditions of
actual operating conditions. You must be sure that all
the check, the required performance, and information
blades are rotating in the same horizontal plane. See
to aid in the correction of malfunctions.
figure 17-10. Pitch adjustment of each blade may be
made to compensate for blade differences.
ROTOR BLADE TRACKING
The Strobex blade tracker permits tracking from
inside the helicopter in flight or on the ground. The
You must perform blade tracking when rerigging
system uses a highly concentrated stroboscopic light
the helicopter. Tracking is necessary when the blades,
beam flashing in sequence with rotation of the
the main gearbox, or the main rotor head assembly
rotary-wing blades, so that a fixed target at the blade
have been replaced. Unless the blades are in proper
tips will appear to be stopped. A soft iron sweep
track, vibrations will occur in the helicopter with every
attached to the rotating swashplate passes close to a
revolution of the main rotor. At high rpm settings,
magnetic pickup attached to the stationary swashplate,
these vibrations could cause serious structural damage.
c a u s i n g a o n c e - p e r- r evo l u t i o n p u l s e , w h i c h
Tracking the blades is necessary to be sure that the
synchronizes the lamp flash rate with the rotation of
blades rotate in the same horizontal plane (track). This
the blades. Each blade has a retroreflective target
is accomplished by pretrack rigging of the rotary-wing
number attached to the underside of the blade in a
head and by the use of pretracked blades.
uniform location. Tracking of each blade is then
Pretrack rigging involves adjusting the pitch
determined by the relative vertical position of the fixed
control rods until an exact sleeve angle (within 1
target numbers. See figure 17-10. Consult the
minute) is found on all sleeve spindles. A micrometer
applicable aircraft MIMs for the proper operating
type of decal is affixed to the adjustable pitch control
procedures for the Strobex blade tracker. For
rods as a permanent reference at the overhaul activity.
maintenance information on the Strobex tracker, refer
A pretrack number is stenciled on each blade at the
to NAVAIR 17-15BBA-4.
time of manufacture or overhaul. This number is based
NOTE: Do not adjust blades by the Strobex
on the effective angle of the blade. Install pretracked
method of blade tracking unless problems result from
blades on the helicopter by setting the adjustable pitch
normal tracking procedures.
control rod to the pretrack number stenciled on the
blade.
ROTOR BRAKE SYSTEM
If the pretrack number is MINUS and the pitch
As a part of the blade folding operation, the rotor
control rod decal shows the setting is zero, loosen the
brake applies manually or automatically. The system
locknut. Shorten the rod by rotating the tang
is shown in figure 17-11. It consists of a rotor brake
clockwise. Keep rotating until it aligns (closest notch)
a s s e m b l y, p a n e l p a c k a g e , a c c u m u l a t o r, m a s t e r
with the appropriate blade pretrack number on the
cylinder, pressure gauge, check valves, and pressure
lower scale of the lower decal. Engage the tang by
switches.
tightening the locknut. If the pretrack number of the
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