To: Notar fan
Sikorsky developed a system where they would pre track the blades and then they would stencil the pre track information on the blade. When a new blade was installed the mechanic would pre adjust the pitch link, which had a calibrated adjustment nut. The mechanic would adjust the pre track adjustment nut to the setting on the blade. This would bring the blade to within ½ inch of the other blades assuming they were already in track. The ½ inch separation was acceptable regarding any resulting vibration caused by the blade being out of track.
As far as balancing the blades Sikorsky would mass balance the blade to establish the spanwise CG. They would then fly the blade against a master blade that had all of the desirable flight characteristics. They would bend the trailing edge of the blade as necessary to minimize the feedback forces and then they would shift the mass balance weight in the tip to minimize the tendency to climb or dive with pitch input until it matched the master blade. The spanwise balance was to within ¼ inch ounce.
If you are flying a Bell the balancing procedure is extremely complex and involved logic diagram where you would perform a task and the logic diagram asked if this solved the problem. If it didn’t you were sent off in another direction and told to perform another task. This challenge / response logic diagram in some cases had over thirty different things to do to arrive at proper balance. In you exited the logic diagram and the balance had not been achieved you were told to install a new set of blades and start over again.
Chadwick Helmuth and Helitune solved a lot of problems. Now the manufacturer just states in the maintenance manual to use these systems to achieve balance. However under certain conditions you would have to install a new set of blades and start over again. So much for progress.
