Chapter 6
Mode l8500C/8500C+ Operators Manual
6-1
6.
Blade Track Observation
You can use the Model 8500C/C+ Balancer/Analyzer to correct both lateral mass and vertical track
imbalances, as described in earlier chapters. Chap ter6 explains vertical imbalances in more detail and
describes how the 8500C/C+ can be used to correct them using an alternative method,
visual tracking
,
under the following topics:
Section 6.1 Blade Track: Introduction .................................................................................6-1
Section 6.2 Vertical Balancing.............................................................................................6-2
Section 6.3 Visual Track Parameter Setup ...........................................................................6-2
Section 6.4 Performing a Visual Track.................................................................................6-4
6.1 Blade Track: Introduction
A rotor system's
track
describes the geometry of the circular path made by the blades as they rotate. A
blade that is out of track may follow a slightly different path because its alignment in the plane of
rotation is skewed. The result is a one-per-revolution vibration whose direction is perpendicular to the
plane of rotation. We can analyze this condition either by measuring the amplitude and frequency of
vibration or by visually characterizing the track to determine the extent of the imbalance. The former
technique is called
vertical balance
and employs principals and procedures nearly identical to those
used to correct a lateral mass imbalance. The latter technique is called a visual or optical track and uses
the Mode l135M-12 Strobex Tracker to illuminate the relative position of the blades as they rotate. In
essence, the goal in both cases is to match the aerodynamic qualities of each blade in the system.
WARNING: Due to the complex interaction between vertical and lateral vibrations, it is
essential that an aircraft's track be adjusted and verified before a lateral balance is
attempted (see Chapt er5 “Balance Measurement and Solutions”).
Selecting the Track Mode
A visual track may be started by putting the 8500C/C+ into its Track mode of operation. This is done
by pressing the
TRACK
key (see Figur e 6 -1).
Figure 6-1. Track Startup Screen
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