Torque Reaction

you should realize that a pilot can move a helicopter forward or rearward, or to the right or left, simply by tilting the main rotor in the desired direction. Look at figure 3-10. This points out another major difference between fixed-wing and rotary-wing aircraft. The fixed-wing aircraft can't move up or down or right or left without forward movement. Remember, a fixed-wing aircraft's primary direction is forward. However, a helicopter can move in any direction, with or without forward movement. Hovering Hovering is defined as maintaining a position above a fixed spot on the ground. A helicopter has the ability to remain in one spot in the air with little or no movement in any direction. This is done by equalizing all the forces acting on the helicopters (lift, drag, weight, and thrust). This action also allows a helicopter to take off or land without a runway. This is another advantage the rotary-wing aircraft has over the fixed-wing aircraft. Torque Reaction As the helicopter's main rotor turns in one direction, the body (fuselage) of the helicopter tends to rotate in the opposite direction (Newton's third law). This is known as torque reaction. In a single main rotor helicopter, the usual way of getting rid of torque reaction is by using a tail rotor (anti-torque rotor). This rotor is mounted vertically on the outer portion of the helicopter's tail section. See figure 3-11. The tail rotor produces thrust in the opposite direction of the torque reaction developed by the main rotor. Figure 3-11 shows the manner in which torque reaction is eliminated in a single main rotor helicopter. Q3-9. How does the pilot change the angle of attack on (a) an airplane and (b) a helicopter? Q3-10. What is the main difference between a helicopter and an airplane? Q3-11. What maneuver can a helicopter perform that an airplane cannot? SUMMARY In this chapter, you have been introduced to the principles of flight. You have learned about the principles of flight for fixed-wing and rotary-wing aircraft. 3-7 Figure 3-10.—Directional flight attitudes. Figure 3-11.—Torque reaction.