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The objectives of S-turns across a road are to develop the ability to compensate for drift during turns, orient the flightpath with ground references, follow an assigned ground track, arrive at specified points on assigned headings, and divide the pilot’s attention. The maneuver consists of crossing the road at a 90° angle and immediately beginning a series of 180° turns of uniform radius in opposite directions, re-crossing the road at a 90° angle just as each 180° turn is completed. The maneuver can be started with either a left hand turn or a right hand turn to go in either direction. Figure 9-6  starts the turn in a left hand turn as an example. 

Accomplishing a constant radius ground track requires a changing roll rate and angle of bank to establish the wind correction angle. Both increase or decrease as the groundspeed increases or decreases. 

The bank must be steepest when beginning the turn on the downwind side of the road and must be shallowed gradually as the turn progresses from a downwind heading to an upwind heading. On the upwind side, the turn should be started with a relatively shallow bank and then gradually steepened as the aircraft turns from an upwind heading to a downwind heading. In this maneuver, the aircraft should be rolled from one bank directly into the opposite just as the 90° reference line on the ground is crossed. 

Before starting the maneuver, a straight ground reference line or road that lies 90° to the direction of the wind should be selected, then the area checked to ensure that no obstructions or other aircraft are in the immediate vicinity. 

The road should be approached from the upwind side at the selected altitude on a downwind heading. When directly over the road, the first turn should be started immediately. [Figure 9-6, position 1 and  Figure 9-7]  With the aircraft headed downwind, the groundspeed is greatest and the rate of departure from the road is rapid; the roll into the steep bank must be fairly rapid to attain the proper wind correction angle. [Figure 9-6, position 2]  This prevents the aircraft from flying too far from the road and from establishing a ground track of excessive radius. 

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During the latter portion of the first 90° turn, when the aircraft’s heading is changing from a downwind heading to a crosswind heading, the groundspeed becomes less and the rate of departure from the road decreases. 

