Tracking the Main Rotor Blades
Blade tracking is the process of determining the positions of the tips of the rotor blade relative to each other while the rotor head is turning, and of determining the corrections necessary to hold these positions within certain tolerances. The blades should all track one another as closely as possible.
Pitch links and tip tabs can be adjusted to compensate for blade differences to keep the blades in line at all forward speeds.
Low speed tracking was at 4700 RPM, then the pilot would "beep" up the engine to where the blades were swinging at 6600 RPM. The ends of the blades were marked with different color grease pencils that would leave a colored mark on the strip of tape placed between the pole arms. You had to rotate this pole very carefully and slowly so that you barely made contact with the blade tips.
Sometimes the blade tips would run right with each other, and sometimes the marks would be several inches apart. The mechanic would then adjust the pitch change link to adjust for "mark on mark" results.
Then, when we flew the aircraft on test flight, if we didn't have the right RPM occur on engine power off for correct wing speed for Auto-Rotation, we would have to bring it back in and adjust the pitch change links equally to either put more pitch into the blades, or to take out pitch in the preset of the blades.