In the worked examples in this chapter, the thrust available is assumed to be constant wit...

In the worked examples in this chapter, the thrust available is assumed to be constant with velocity for the reasons explained at the end of Section 5.1. However, in reality, the thrust from a typical turbofan engine decreases with an increase in velocity. The purpose of this and the following problems is to revisit some of the worked examples, this time including a velocity variation for the thrust available. In this fashion we will be able to examine the effect of such a velocity variation on the performance of the airplane. The airplane is the same Gulfstream IV examined in the worked examples, with the same wing loading, drag polar, etc. However, now we consider the variation of thrust available given by

At sea level:

At 30,000 ft:

Recall that that (T_A)_V=0 is the thrust at sea level at zero velocity.

(a) At sea level, plot the thrust available curve using Eq. (1) above, and the thrust

required curve, both on the same graph. From this, obtain V_max at sea level.

(b) At an altitude of 30,000 ft, plot the thrust available curve, using Eq. (2) above, and the thrust required curve, both on the same graph. From this obtain V_max at 30,000 ft.

(c) Compare the results obtained from (a) and (b) with the analytical results from Example 5.6.