For this case, we offered RL-R19 to be used as a DAQ-system.
The positioning of points close together means that the increased level of vibration is due to the main rotor unbalance. The distance of points from the center and the space occupied by the cloud of points tells us that the balancing procedure has good chances of being a success.
Even though the unbalance vector has slightly changed, the cloud of points is still dense and located in about the same segment of the diagram. It shows that the nature of the unbalance is fixed, e.g. it is due to the uneven mass distribution in the rotor and does not depend on the flight mode.
To determine the “heavy point”, the trial weight of 500 g was placed on the first blade of the main rotor.
After that, the unbalance vector shifted very little in phase, which signifies that the corrective weight is to be placed around the angle of the first blade. It was calculated that the mass of the corrective weight is 1980.14 g and the angle of its placement is 12⁰.
The corrective weight was split onto two nearby blades:
First, a initial run was performed.
The following flight modes were selected as the relevant ones:
The analysis of the acquired data in VisAnalyser showed that the main rotor has some imbalance. The imbalance vector retained practically the same phase in different flight modes.
To determine the “heavy point”, the trial weight of 500 g was placed on the first blade of the main rotor. After that, the imbalance vector shifted very little in phase, which signifies that the corrective weight is to be placed around the angle of the first blade. It was calculated that the mass of the corrective weight is 1980.14 g and the angle of its placement is 12⁰.
The corrective weight was split into two nearby blades:
Hover: vibration was decreased from 5.56 mm/s to 2.15 mm/s.
100 km/h: vibration was decreased from 4.11 mm/s to 1.25 mm/s.
200 km/h: vibration was decreased from 6.24 mm/s to 3.49 mm/s.