Landing
All good things must come to an end," and most flights end with a landing. The relative difficulty of this maneuver is often expressed by a student pilot after the first solo flight: "The first thought that came to mind after I took off was `Oh boy, now I've gotta land this thing!'"
After lining the airplane up with the runway and configuring it properly (landing gear, proper flap setting, speedbrake out), the pilot uses the throttle setting to maintain the proper airspeed (100 knots) and uses the elevators and ailerons to keep the airplane headed for the runway. The airplane is set up in a shallow descent (about three degrees) aimed at the near end of the runway. If this part of the landing, the "final approach" is flown correctly, it will look like the jet is headed for a collision with the approach end of the runway.
As the airplane closes in on the approach end, the pilot begins to ease the stick back to level off the airplane several feet above the runway and slows to landing speed by reducing the power to idle. As the airplane levels off just above the ground in idle power, it will lose speed rapidly because there is little or no thrust to counter the drag. The pilot continues to move the stick back to increase the AOA and keep the airplane flying for just a little while longer. In a well-flown landing, the airplane will settle to the ground just before the stall AOA is reached.
Now a land-based vehicle, the airplane is controlled with the brakes and slowed to taxi speed.
The Axis System
A good understanding of the basic axis system used to describe aircraft motion is necessary to appreciate flight data. Aircraft translational motion is described in terms of motion in three different directions, each direction being perpendicular to the other two (orthogonal). Motion in the X direction is forward and aft velocity. The Y direction produces sideways motion to the left and right, and up and down motion is in the Z direction.
Rotational Axes
The rotational motion of an aircraft can be described as rotation about the same three axes; pitch rotation (nose up or nose down) is about the y axes, lateral or roll rotation (one wing up or down) is about the x axis, and yaw rotation (nose right or left) is about the z axis.
There are several slightly different versions of the basic axis system just described. They differ primarily in the exact placement of the zero reference lines, but are generally similar in their directions. (For example, the body-axis system uses the fuselage center line as the x axis, while a wind-axis system uses the direction that the aircraft is moving through the air as the x axis.)