TM 1-1520-238-T-4
Change 9
5–57
5–22.
MAIN ROTOR TRACK AND BALANCE TROUBLESHOOTING USING
5–22
AVA EQUIPMENT
a. TROUBLESHOOTING
1. The following are possible indications of an out of phase condition, which may require main rotor blade
phase to be checked per (TM 1-1520-238-23).
Excessive weight required (1000g).
Difference in thread count between dampers.
Adjustments for lead–lag should never be made utilizing data from AVA. The reason moves
should not be made based on AVA dynamic measurement is that the dynamic phase of blades is
a relative measurement. If blade one is out of phase statically, then dynamic phase date from AVA
will show blade 1 and 3 both out of phase, because this is a relative measurement. If AVA
indicates a possible phase problem, statically phase blades in accordance with
(TM 1-1520-238-23).
2. If AVA recommends an excessive trim tab bend (greater than 4 deg), or there is an excessive hook in a
blade track trend from hover to speed (greater than 3 inches), then the following following procedure may be
utilized to avoid excessive trim tab bending.
NOTE
This is not normal procedure for track and balance and should only be
used on blades that are climbing or diving excessively as described
above.
Utilize pockets #0–3 on this particular blade and put in a 1/2 degree bend
in the appropriate direction. Once this is performed repeat the track and
balance procedure starting at paragraph 5–19 (Ground Track and
Adjustment). This procedure can be repeated twice with a maximum
bend in pockets #0–3 of + or – 1 degree.
3. If a blade does not respond correctly, check trim tabs to ensure that the blade has a uniform bend. If the tab
is not uniform, tab it back to 0 (zero) and start track and balance over from paragraph 5–19 (Ground Track
and Adjustment).
END OF TASK
