Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 78

Up to this point, you may have considered the wing to be the only aerodynamically important structure of an aircraft. But in fact the entire structure of the airplane plays a role in the efficiency of an aircraft in flight, and identifying how, and to what extent, each part of an airplane structure plays a role is an important first step. We will begin with a review of the more prominent structures discussed in aerodynamics, because their direct role on lift and drag provides the foundation for more complicated discussions in the future.

Flight control systems are of two types: primary and secondary. Primary control systems on fixed‐wing aircraft include the ailerons, elevator (stabilator), and rudder and, depending on the aircraft type and aircraft speed, give the pilot a “feel” of how the aircraft is performing. Secondary systems such as trim systems, flaps, spoilers, and leading edge devices are used in relieving control pressures for the pilots, assisting primary control surfaces in high‐speed flight, or improving the performance characteristics of the aircraft in general.

Figure 3.1 Modern transport category control surfaces.

Source: U.S. Department of Transportation Federal Aviation Administration (2008a).

Airplanes are flown in various configurations of gear and flaps, but for this textbook we will commonly refer to clean and dirty as the two reference configurations. In a clean configuration, the gear is retracted (when applicable), and the flaps and other high‐lift devices are retracted. In the dirty configuration, the gear is considered down and locked, and the high‐lift devices are fully deployed.

Figure 3.1 shows example of airfoils found on many air transport aircraft category still in use today. Figure 3.2 details the flight control system of a helicopter, incorporating anti‐torque pedals, a cyclic, and a collective. An expanded discussion of these primary flight controls can be found in Chapter 15.