6-2
Chadwick-Helmuth Company, Inc.
Chapter 6
- Blade Track Observation
NOTE: If the 8500C/C+ is currently performing other time-critical functions, it may be
necessary to press
STOP
to terminate the function before Track mode can be entered.
6.2 Vertical Balancing
A vertical balance attempts to analyze the vertical (that is, perpendicular to the plane of rotation)
vibration amplitude caused by an out-of-track rotor blade. Essentially, the only difference between
these vibration signals and those generated by a lateral mass imbalance are their orientation to the
plane of rotation. Analysis of the problem otherwise involves very similar principles. The technique
used to solve a vertical imbalance is therefore nearly identical to the technique of solving a lateral mass
imbalance (see Secti on5.4 Balance Measurement” on page 5 -9). The only differences to note are
• Orientation of the Mo del7310 Velocimeter. Its cylindrical axis must be aligned in the direction of
the out-of-track vibration
• Type of balance chart selected
Chadwick-Helmuth supplies charts for vertical or track balancing of many helicopter rotor systems.
Otherwise, you must closely adhere to the procedure for deriving balance solutions, as explained in
Chapter 5 “Balance Measurement and Solutions” in this manual.
In general, the refined electronic measurements taken during a vertical balance provide a mor
sophisticated balance solution than visual tracking. However, in those situations where a vertical
balance has been performed, visual tracking can be used to independently verify the balance solution.
Moreover, performing a visual track
before
a vertical balance provides important information about the
track characteristics of each blade. This information can then be used during vertical balance to help
select the best alternate balance solution.
6.3 Visual Track Parameter Setup
The 8500C/C+ supports the modification of several important parameters used to control data
acquisition and display during a visual track. One of these parameters, the number of blades to track, is
automatically set when a balance chart is selected from balance mode.
All pertinent Track mode parameters can be modified by using the soft keys at the bottom of the Track
Start-up screen (see Fig ure6-1 on page6-1).
MORE
and
FEWER
increase and decrease the number of
blades to track, respectively (see Secti on6.3.1 “Number of Blades” on pag e6-3).
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