Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 79

The ailerons are usually located on the trailing edge of each wing closer to the outboard area by the tip. Ailerons control roll about the longitudinal axis as they move opposite of each other when the pilot banks left or right with the yoke or stick, with the “up” aileron on the downward moving wing. Most ailerons are connected by a mechanical means to the aircraft yoke through cables, bell cranks, pulleys, and/or push‐pull tubes. Some jet aircraft have additional ailerons located in the midwing area for high‐speed maneuvering, to reduce roll rate.

Figure 3.2 Helicopter flight controls.

Source: U.S. Department of Transportation Federal Aviation Administration (2016b).

Figure 3.3 Differential ailerons.

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

When the yoke/stick is moved to the left, the ailerons deflect in opposite directions, the aileron on the left wing rises and the aileron on the right wing deflects downward. This action results in more lift on the right wing and a resultant roll to the left around the longitudinal axis. Later in Section 3.3 of Chapter 4 we will explain why this happens.

There are many styles of ailerons used throughout the fixed‐wing aircraft industry today, including differential ailerons, frise‐type ailerons, and flaperons. Differential ailerons work by deflecting the up aileron more than the down aileron, increasing drag on the downward wing counteracting adverse yaw (Figure 3.3). Frise‐type ailerons project the leading edge of the raised aileron into the wind, increasing drag on the lowered wing to once again minimize the effects of adverse yaw (Figure 3.4). Flaperons combine the control surfaces of the ailerons with the function of the trailing edge flaps, as they can be lowered like flaps but still control bank angle like traditional ailerons. Chapters 12 and 13 in this textbook will discuss these items, as well as adverse yaw, in more depth regarding aircraft stability.

Figure 3.4 Frise‐type ailerons.

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