RESPONSE TO THE THROTTLE

For the same jet airplane and flight condition as in previous numerical examples, we calculate the response to a step input in the throttle of A8p = |, which corresponds to a thrust increment of 0.05W. The matrix В is given by (7.6,5) and Де is

Дс = [0 l/6f (7.7,13)

The numerical results are shown in Fig. 7.21. Because the model has not included any engine dynamics, the results are not valid for the first few seconds. However, this region is not of much interest in this case. The motion is clearly seen to be dominated by the lightly damped phugoid. The speed begins to increase immediately, before the other variables have time to change. It then undergoes a slow damped oscillation, ul­timately returning to its initial value. The angle of attack varies only slightly, and у makes an oscillatory approach to its final positive value yss. The new steady state is a climb with Ди = Да = 0. When the thrust line does not pass through the CG, the re­sponse is different in several details. Principally, the moment of the thrust causes a

rapid change in a, followed by an oscillatory decay to a new Aass Ф 0, and the speed converges to a new value Дм„ Ф 0.

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