0073 00
TM 1-6625-724-13&P
0073 00-14
NOTE
When the vertical vibration is close to being within limits
and recommended tab moves are too small to be made,
use Edit Adjustables to turn off tabs and turn on pitch
links for the final 1–2 flat end moves. The only criteria
for successfully completing the in-flight smoothing of the
rotor is the vibration levels, the final track is not
important. Once the vertical vibration is acceptable and
if fore/aft ground vibration is still above limits use the Edit
Adjustables to turn off tabs and pitch links. Hub weight
only moves do not affect the 1/REV vertical in forward
flight significantly.
m. If alterations are desired to the fault solution, use Edit Defaults and/or Edit Adjustables to make desired
changes. Always select View Predictions to check that the predicted vibration levels, with the altered set of
adjustments, will be reduced.
n. After each set of adjustments and verification flight it is recommended to use the Trend Flights display to view
the in-flight vertical vibration. Vibration levels should be decreasing and moving towards the center of the polar
plot. If not (see Chapter 2, Displays WP 0010) for troubleshooting.
o. Repeat procedure 2 until acceptable vibration levels are met.
p.
Remove test equipment and make appropriate log entries.
PROCEDURE 3: TROUBLESHOOTING
Experience on new aircraft and high time retrofit aircraft have shown the following sources of track and balance
problems:
Changing Ride:
Loss of torque on upper and/or lower hub to mast cone joints. 1/REV can be corrected with trim tab only.
Vertical Ground Bounce at 100% RPM:
When pulling collective if a vertical 1/REV vibration is felt on the ground then the most likely source is a loose
swashplate sleeve.
Vertical 1/REV in Hover:
High levels of vertical 1/REV in a hover have been scarce. Check for a loose main rotor grip/pitch horn joint.
Vertical 1/REV Torque Sensitive “HOP”:
Worn drive links, rotor not rpm tracked.
Vertical 1/REV During Entry and Recovery from Maneuvers:
Low swashplate friction.
Vertical 1/REV in a Steady Turn Which Builds as a Function of Load Factor:
Out of product balanced blade. Confirm by looking at track change from ground to hover and take data in a turn.
If the blade is seen to change track from ground to hover and do the same thing in a turn, then the blade is out of
product balance. Replace blade and return to manufacturer for re-whirling if 1/REV is unacceptable.
