As the standard procedure at the factory only took into account the vertical vibration, we suggested that after the balancing procedure the vibration level on the other axes increased.
The results turned out to be as predicted:
Axis |
Vertical |
Longitudinal |
Lateral |
Vibration level, mm/s |
0.1 |
14.6 |
12.7 |
All the corrective weights were removed from the main rotors in order to run the dynamic balancing procedures with all three axes taken into account.
The initial level of vibration:
Axis |
Vertical |
Longitudinal |
Lateral |
Vibration level |
3.1 |
1.6 |
1.6 |
We decided to perform the balancing of the lower rotor first, and then make adjustments to minimize the corrective weights to be placed on the upper rotor.
As the helicopter is small, sets of spacers were used as corrective weights. The weight of 8 g was mounted on the lower rotor.
The vibration level after balancing lowered:
Then calculations were made and a corrective weight of 3 g was placed on the upper rotor.
Balancing results after control hover:
Axis |
Vertical |
Longitudinal |
Lateral |
Vibration level, mm/s |
2.3 |
0.6 |
0.8 |