Rotor Balancing (coaxial scheme)

Data acquisition systems, recorders, spectrum analyzers RL-C21M

Vibration control systems RL-C21

Vibration control systems RL-C25

Data acquisition systems, recorders, spectrum analyzers RL-R19

Data acquisition systems, recorders, spectrum analyzers RL-R17

Software Sensor Calibration

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Risinājums.

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

In spite of the fact that the vertical vibration was insignificant, the vibration on longitudinal and lateral axes was too great, hence the complaints of the crew.

Preparation

All the corrective weights previously placed on the blades of the main rotor were removed, in order to run the dynamic balancing procedures with all three axes taken into account.

The initial level of vibration without corrective weights was the following:

Balancing algorithm

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, since the influence of the upper rotor unbalance is greater due to longer arm of force

Lower rotor balancing

As the helicopter is small, we used sets of spacers as corrective weights. Based on the results of measurements and calculations, the weight of 8 g was mounted on the lower rotor.

The vibration level after the balancing lowered

Upper rotor balancing

The upper rotor balancing was performed in the hover mode.

Aftre the calculations a corrective weight of 3 g was placed on the upper rotor.

Balancing results after control hover were the following

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

Based on the results of trial balancing using a 3-axial accelerometer and RL-R19, the helicopter manufacturer modified their balancing method.

Secinājums

Based on the results of trial balancing using a 3-axial accelerometer and RL-R19, the helicopter manufacturer modified their balancing method. Now all the helicopters they produce are balanced regarding the level of vibration on three axes.