Download - NASA
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Solution Procedures 41<br />
Table 5-4. Trim solution.<br />
trim variable perturbation<br />
aircraft orientation θ (pitch), φ (roll) 100AΔ<br />
aircraft velocity Vh (horizontal velocity) V Δ<br />
aircraft velocity Vz (vertical velocity) V Δ<br />
aircraft velocity β (sideslip) 100AΔ<br />
aircraft angular rate ˙ θ (pullup), ˙ ψ (turn) ΩΔ<br />
aircraft control angle 100AΔ<br />
5-1.7 Rotor-Flap Equations<br />
Evaluating the rotor hub forces may require solution of the flap equations E(v) =0. For tippath<br />
plane command, the thrust and flapping are known, so v =(θ0.75 θc θs) T . For no-feathering plane<br />
command, the thrust and cyclic pitch are known, so v =(θ0.75 βc βs) T . A Newton–Raphson solution<br />
method is used: from E(vn+1) ∼ = E(vn)+(dE/dv)(vn+1 − vn) =0, the iterative solution is<br />
vn+1 = vn − CE(vn)<br />
where C = f(dE/dv) −1 , including the relaxation factor f. The derivative matrix for axial flow can be<br />
used. Alternatively, the derivative matrix dE/dv can be obtained by numerical perturbation. Convergence<br />
of the Newton–Raphson iteration is tested in terms of |E|