How are helicopter rotor blades balanced?
Most blades are as close as possible when built at the factory. Yes, it is like a car wheel you use weights to balance. For the Blackhawk helicopter there are inserts on the hub near the blade to add weights. But additionally there are a maximum amount of weight that can be added. If you're unable to balance the main rotor head, sometimes you have to switch blades around to other sides and adjust weights. If it still doesn't balance usually it is due to the installation of the hub to the main transmission then gaps have to be measured.