In flight, the control surfaces of an aircraft produce aerodynamic forces. These forces are applied at the center of pressure of the control surfaces which are some distance from the aircraft's center of gravity and produce torques (or moments) about the principal axes. The torques cause the aircraft to rotate. The elevators produce a pitching moment, the rudder produces a yawing moment, and the ailerons produce a rolling moment. The ability to vary the amount of the force and the moment allows the pilot to maneuver or to trim the aircraft.
These axes move with the aircraft, and change relative to the earth as the aircraft moves. For example, for an aircraft whose left wing is pointing straight down, its "vertical" axis is parallel with the ground, while its "lateral" axis is perpendicular to the ground. Therefore here yaw means an intrinsic motion, as in Yaw rate sensor.
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The three Aircraft principal axes
- Vertical axis, or yaw axis — an axis drawn from top to bottom, and perpendicular to the other two axes. Parallel to the fuselage station.
- Lateral axis, or pitch axis — an axis running from the pilot's left to right in piloted aircraft, and parallel to the wings of a winged aircraft. Parallel to the buttock line.
- Longitudinal axis, or roll axis — an axis drawn through the body of the vehicle from tail to nose in the normal direction of flight, or the direction the pilot faces. Parallel to the waterline.
- Transverse axis — another term for the Lateral axis
Vertical axis (yaw)
The vertical axis passes through the plane from top to bottom. Rotation about this axis is called yaw. Yaw changes the direction the aircraft's nose is pointing, left or right. The primary control of yaw is with the rudder. Ailerons also have a secondary effect on yaw.
Yaw axis is a vertical axis through an aircraft, rocket, or similar body, about which the body yaws; it may be a body, wind, or stability axis. Also known as yawing axis.[1]
The yaw axis is defined to be perpendicular to the body of the wings with its origin at the center of gravity and directed towards the bottom of the aircraft. A yaw motion is a movement of the nose of the aircraft from side to side. The pitch axis is perpendicular to the yaw axis and is parallel to the body of the wings with its origin at the center of gravity and directed towards the right wing tip. A pitch motion is an up or down movement of the nose of the aircraft. The roll axis is perpendicular to the other two axes with its origin at the center of gravity, and is directed towards the nose of the aircraft. A rolling motion is an up and down movement of the wing tips of the aircraft. [2]
Lateral axis (pitch)
The lateral axis passes through the plane from wingtip to wingtip. Rotation about this axis is called pitch. Pitch changes the vertical direction the aircraft's nose is pointing. The elevators are the primary control of pitch. Also called Transverse axis.
Longitudinal axis (roll)
The longitudinal axis passes through the plane from nose to tail. Rotation about this axis is called bank or roll. Bank changes the orientation of the aircraft's wings with respect to the downward force of gravity. The pilot changes bank angle by increasing the lift on one wing and decreasing it on the other. This differential lift causes bank rotation around the longitudinal axis. The ailerons are the primary control of bank. The rudder also has a secondary effect on bank.
Relationship with other rotations
These axes are related to the principal axes of inertia, but are not the same. They are geometrical symmetry axes, regardless of the mass distribution of the aircraft.
In aeronautical and aerospace engineering they are often called Euler angles, but this conflicts with existing usage elsewhere. They are intrinsic rotations and the calculus behind them is similar to the Frenet-Serret formulas.
These rotations are intrinsic. To perform a rotation in an intrinsic reference frame is equivalent to right-multiply its characteristic matrix (the matrix that has the vector of the reference frame as columns) by the matrix of the rotation.
History
The first aircraft to demonstrate active control about all three axes was the Wright brothers' 1902 glider.[3]
See also
References
- ^ "Specialty Definition: YAW AXIS". http://www.websters-online-dictionary.org/ya/yaw+axis.html. Retrieved 2008-07-31.
- ^ "Yaw axis". http://www.answers.com/topic/yaw-axis. Retrieved 2008-07-31.
- ^ "Aircraft rotations". http://www.grc.nasa.gov/WWW/K-12/airplane/rotations.html. Retrieved 2008-08-04.
External links
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