content_image/602504.jpg
<img src='content_image/602504.jpg'>

within this moving body of air (wind), it moves or drifts with the air in the same direction and speed, just like the boat moved with the river current. 

When flying straight and level and following a selected ground track, the preferred method of correcting for wind drift is to head the aircraft (wind correction angle) sufficiently into the wind to cause the aircraft to move forward into the wind at the same rate the wind is moving it sideways. Depending on the wind velocity, this may require a large wind correction angle or one of only a few degrees. This wind correction angle is also commonly known as the crab angle. When the drift has been neutralized, the aircraft follows the desired ground track. 

To understand the need for drift correction during fl ight, consider a flight with a wind velocity of 20 knots from the left and 90° to the direction the aircraft is headed. After 1 hour, the body of air in which the aircraft is fl ying has moved 20 nautical miles (NM) to the right. Since the aircraft is moving with this body of air, it too has drifted 20 NM to the right. In relation to the air, the aircraft moved forward; but in relation to the ground, it moved forward as well as 20 NM to the right. 

There are times when the pilot needs to correct for drift while in a turn. [Figure 9-2] Throughout the turn, the wind is acting on the aircraft from constantly changing angles. The relative wind angle and speed govern the time it takes for the aircraft to progress through any part of a turn. This is due to the constantly changing groundspeed. When the aircraft is headed into the wind, the groundspeed is decreased; when 

headed downwind, the groundspeed is increased. Through the crosswind portion of a turn, the aircraft must be turned sufficiently into the wind to counteract drift. 

To follow a desired circular ground track, the wind correction angle must be varied in a timely manner because of the varying groundspeed as the turn progresses. The faster the groundspeed, the faster the wind correction angle must be established; the slower the groundspeed, the slower the wind correction angle may be established. It can be seen then that the steepest bank and fastest rate of turn should be made on the downwind portion of the turn and the shallowest bank and slowest rate of turn on the upwind portion. 

The principles and techniques of varying the angle of bank to change the rate of turn and wind correction angle for controlling wind drift during a turn are the same for all ground track maneuvers involving changes in direction of fl ight. 

When there is no wind, it should be simple to fly along a ground track with an arc of exactly 180° and a constant radius because the flightpath and ground track would be identical. This can be demonstrated by approaching a road at a 90° angle and, when directly over the road, rolling into a medium-banked turn. Then, maintaining the same angle of bank throughout the 180° of turn.  [Figure 9-2] 

To complete the turn, the rollout should be started at a point where the wings become level as the aircraft again reaches the road at a 90° angle and is directly over the road just as the 

