Flight Controls and the Lateral Axis

in Physics

The lateral axis of an airplane is a line that runs below the wing, from wingtip to wingtip, passing through the airplane’s center of gravity. Movement around this axis is called pitch, and control around this axis is called longitudinal control. The flight control that handles this job is the elevator attached to the horizontal stabilizer, a fully moving horizontal stabilizer, or on a v-tail configured airplane, it is called ruddervators. An elevator on a Cessna 182 can be seen in Figure 3-65. In Figure 3-66, a fully moving horizontal stabilizer, known as a stabilator, can be seen on a Piper Cherokee Arrow, and Figure 3-67 shows a ruddervator on a Beechcraft Bonanza.

Figure 3-65. Elevator on a Cessna 182 provides pitch control.

Figure 3-65. Elevator on a Cessna 182 provides pitch control.

 


Figure 3-66. Moving horizontal stabilizer, known as a stabilator, on a Piper Cherokee Arrow provides pitch control.

Figure 3-66. Moving horizontal stabilizer, known as a stabilator, on a Piper Cherokee Arrow provides pitch control.

 

Figure 3-67. Ruddervators on a Beechcraft Bonanza provide pitch control.

Figure 3-67. Ruddervators on a Beechcraft Bonanza provide pitch control.

Depending on the airplane being discussed, movement around the lateral axis happens as a result of the pilot moving the control wheel or yoke, the control stick, or on some airplanes, a side stick. On the airplanes shown in Figures 3-65, 3-66, and 3-67, a control wheel or yoke is used.

On the Cessna 182 shown in Figure 3-65, pulling back on the control wheel causes the trailing edge of the elevator to deflect upward, causing an increased downward force that raises the nose of the airplane. Movement of the elevator causes the nose of the airplane to pitch up or pitch down by rotating around the lateral axis. The Cessna 182 control wheel can be seen in Figure 3-68.

Figure 3-68. Cessna 182 control wheel and rudder pedals.

Figure 3-68. Cessna 182 control wheel and rudder pedals.

On the Piper Cherokee Arrow shown in Figure 3-66, pulling back on the control wheel causes the entire horizontal surface (stabilator) to move, with the trailing edge deflecting upward. The anti-servo tab seen on the Cherokee provides a control feel similar to what would be experienced by moving an elevator. Without this tab, the stabilator might be too easy to move and a pilot could overcontrol the airplane.

The ruddervators shown on the Beechcraft Bonanza in Figure 3-67 are also moved by the control wheel, with their trailing edges deflecting upward when the control wheel is pulled back. As the name implies, these surfaces also act as the rudder for this airplane.