Example – Sea King

Подпись: All-up weight, AUW Main rotor tip speed, VTM Main rotor radius, R Main rotor figure of merit, FOM Tail rotor tip speed, VTT Tail rotor radius, RT Tail rotor solidity, s Air density, p Blade stall angle, aSTALL Lift curve slope, a Pitch-flap coupling angle, d3 Tail boom length, lBooM Подпись: 82000 N 206 m/s 9.39 m 0.85 207 m/s 1.57 m 0.188 1.2256 kg/m3 12 degrees 5.8 /rad 45 degrees 11.2 m

The following data are used:

This produces the graph in Figure 6.28.

The figure shows the yaw acceleration attainable with the rotor on the point of stall. The yaw acceleration is normalized with the value in steady hover – that is, no yaw rate. Notice that, as the yaw rate increases, the thrust potential reduces as the precessional effects emerge by limiting the collective pitch which can be achieved before part of the tail rotor enters stall – in this case a yaw rate of 2.2rad/s.

Figure 6.28 Yaw acceleration limit due to precession caused by yaw rate

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