TM 1-1520-238-T-4
5–52
Change 9
5–21.
FLIGHT CHECK AND ADJUSTMENT USING AVA EQUIPMENT (cont)
5–21
TAB: AVA turns on pockets of tab based on track split at each airspeed. Even though tabs are
turned on by the amount of track split, AVA will not try to fix the track split, it will utilize pockets
that are turned on to reduce overall vibration. AVA’s goal here is to minimize vibration, which may
not produce a perfect flat track.
PITCH LINK: AVA will utilize pitch links if a blade remains out of track the same amount at all
airspeeds. AVA will also recommend pitch link against a tab move to effect vibration environment.
(2) If the default solution contains small moves or numerous moves it is always recommended to obtain a
custom solution. The reason this is recommended is that if there are small moves or a lot of moves there is plenty
of opportunity for errors to be introduced. Many times with fewer moves or even with one move the vibration
environment can be reduced to acceptable levels. AVA was designed to give optimum solution to drive vibration
levels to zero. The following are examples that can be utilized to obtain a custom solution that users have had
success with in the field. Custom solutions usually will reduce the number of adjustments and still reduce the
vibration to an acceptable level. Every adjustment made to the rotor system is an opportunity for an error to be
introduced.
CUSTOM SOLUTIONS:
Utilizing RESOLVE TO LIMITS from the Edit Defaults screen.
The RESOLVE TO LIMITS option in the Edit Defaults is a very powerful feature of the AVA. For
the AH–64 script file, the default for the Resolve to Limit feature is OFF. To utilize the RESOLVE
TO LIMIT feature, the only change required to the Edit Defaults screen is to toggle the RESOLVE
TO LIMIT to ON (Leave the MAXIMUM # OF ADJUSTMENTS set at ) (zero) and the WEIGHTING
MODE will change to AUTO once the DO key is pressed to obtain a solution (see NOTE below)).
Once the RESOLVE TO LIMIT is toggled to ON, press DO and EDIT ADJUSTABLES screen will
automatically be displayed. It is recommended that you press DO without making changes to the
EDIT ADJUSTABLES screen, then AVA will pick the best solution without being restricted. If
changes or restrictions are desired make them on the EDIT ADJUSTABLES screen (one example
is if you did not want AVA to consider a WEIGHT adjustment you could toggle off weight in the
EDIT ADJUSTABLES and AVA will not use WEIGHT adjustment for the calculation of the best
adjustments). Once changes are made, or if none were made, press DO to obtain a solution. AVA
diagnostics will start at the best one adjustment and check to see if the best one adjustment will
bring the vibration environment into limits. If it will not bring the vibration environment into limits
with the best one adjustment, it will start adding adjustments one at time until it obtains a solution
that is within limits. Once a solution is obtained compare the predictions from the default
adjustments to see if the vibration environment is going to be reduced to satisfactory level with
less moves. Once a solution is compared it is recommended that you perform the Maximum # of
Adjustments option and compare that solution.
