TM 55-4920-390-13&P
NOTE
It is best to "stay loose" when holding and aiming the light. Generally, the light should be held at
arm's length, with arm slightly bent. Keep both eyes open and watch the blade tip path while
slowly sweeping light beam in azimuth and vertically until reflection is caught. Don't tense up,
don't squint an eye, don't "aim" the light, don't brace against the airframe. Especially, in flight, the
blades swing up and down due to gusting and maneuvering. It is easy to pick up the targets
quickly, and keep them in sight, if you STAY LOOSE!
4-8. CORRECTIVE ACTION. With the track thus determined, corrective action follows. This typically involves shutting
down the helicopter and adjusting the appropriate pitch links the right number of "clicks" in the right direction. For
example, Blade 3, up (or CW) 2 "clicks", and 6 goes down (CCW) 4 "clicks".
NOTE
The number of "clicks" to correct a 1" error will be different depending on whether the 1" is
observed on the ground or in flight. The required ratios are quickly learned for each helicopter
type and in the different conditions of service.
4-9. CONFIRM TRACK . The Strobex Tracker is so quick and simple to use, it is quick and advisable to check the result
and confirm proper track.
4-10. LEAD-LAG ACTION . If lead-lag errors are observed, the dampers are suspect. Adjustment or replacement may
be indicated. Other parts may be at fault, however, and the decision must be left to qualified personnel.
NOTE
It is often helpful to perform certain maneuvers while looking for lead-lag. A climbing left turn may
expose a problem that otherwise would go undetected. This is a suggestion only and the
appropriate maneuver will depend on helicopter type and circumstances. The choice must be left
to qualified personnel.
4-11. USE WITH OSCILLATOR DE-ACTIVATED .
When the Strobex Blade Tracker, Model 135M-9 is
used on
helicopters previously equipped to use the earlier models M, M-2 or M-5, the vernier on the back of the hand-held lamp
(Fig. 1-4) must be
turned full CCW to
de-activate the oscillator. The light will then be
caused to
flash once per blade ("n"
per rev) by the "n" wipers fixed to the rotating swash plate.
4-8