Page 213 - Understanding Flight

CH07_Anderson 7/25/01 9:01 AM Page 200

200 CHAPTER SEVEN

The Boeing 777 (Figure 3.35) has a high wing loading and,
moderate L/D and thrust-to-weight ratio. It also has a low specific fuel
consumption. Because of the high wing loading, the Boeing 777 needs
long runways found only at the larger commercial airports. Although
it has a maximum L/D similar to the Cessna it has a higher thrust-to-
weight ratio. Therefore, the Boeing 777 has a service ceiling about
2 1/2 times that of the Cessna 172. One design goal of the Boeing 777
was to have a long enough range to service trans-Pacific routes.
Therefore, efficient engines are used and it carries up to 40 percent of
its weight in fuel. Neither tight nor fast turns are necessary or possible
with this airplane.
The F-22 (Figure 3.36) has a high wing loading, low L/D
(highdrag), high thrust-to-weight ratio, and moderate specific fuel
consumption. The high thrust-to-weight ratio allows for extremely
steep climbs and high maneuverability. It also gives a high service
ceiling, despite the low L/D. Its service ceiling is just a little higher
than that of the Boeing 777. The range of the F-22 is low because of
the high drag and the desire to trade fuel weight for payload weight.
The F-22, like all fighters, will require frequent refueling for long trips.
The next chapter introduces you to the uses of flight testing and
wind-tunnel testing. These types of tests are used to determine some
of the parameters discussed in this chapter.