FLIGHT CHECK AND ADJUSTMENT USING AVA EQUIPMENT (cont)
(12) If measured values exceed specifications, press DO to execute diagnostics. AVA will make
recommendations to correct excessive vibration. Review WHAT YOU SHOULD KNOW BEFORE ENTERING
DIAGNOSTICS and Step c., INTERPRETING RESULTS AND MAKING CORRECTIONS.
(13) After corrections are made, refly aircraft and repeat step b. to recheck the 1/REV vibrations through
required flight conditions.
If a weight adjustment is required, go to paragraph 520, step e.
If a pitch link adjustment is required, go to paragraph 519, step c.
If a trim tab adjustment is required, go to step d.
(14) Remove Aviation Vibration Analysis equipment (TM 1-1520-238-23).
(15) Inspect (QA).
WHAT YOU SHOULD KNOW BEFORE ENTERING DIAGNOSTICS
Before entering diagnostics it may be beneficial to view the in flight vertical readings on the polar plot and the in
flight track trend. By doing this before entering diagnostics, it will give a good indication of what will be required to
smooth the aircraft.
Figure 518 illustrates a polar plot display of the in flight vertical vibration readings from the AVA:
11:58:00 28 AUG 96
Polar Plot Display
By viewing the display above and the AH-64 coefficient polar chart for vertical vibration at the end of this section,
this clearly shows that blade 1, blade 3, or both will require adjusting to move the vibration points towards the
center. To move the vibrations points towards center for this example would required blade 1 to be tabbed down
(or pitch linked down) or blade 3 to be tabbed up (or pitch linked up).