Helicopter rotor tuning (track and balance) is the process of adjusting the rotor blades so as to reduce the

aircraft vibration and the spread of rotors. Rotor tuning as applied to Sikorsky’s Black Hawk (H-60)

helicopters is performed as follows. For initial measurements, the aircraft is flown through six different

regimes, during which measurements of rotor track and vibration (balance) are recorded. Rotor track is

measured by optical sensors, which detect the vertical position of the blades. Vibration is measured at the

frequency of once per blade revolution ( per rev) by two accelerometers, A and B, attached to the sides of

the cockpit (see Figure 6.1, detail B). The vibration data are vectorially combined into two

components: A þ B, representing the vertical vibration of the aircraft, and A 2 B, representing its roll

vibration. A sample of peak vibration levels for the six flight regimes, as well as the peak angular

positions relative to a reference blade, are given in Table 6.1, along with a sample of track data.

knots (145), and maximum horizontal speed (vh). The track data indicate the vertical position of each

blade relative to a mean position.