Definition
A ground reference maneuver in which the airplane is flown in a series of opposite, semicircular paths of equal radius on either side of a straight road or line on the ground, with the wings rolling level momentarily as the airplane crosses the reference line. The pilot must continuously vary the bank angle to compensate for wind drift so that each half-circle traces a true semicircle of equal size over the ground.
Plain English
You fly back and forth across a straight road, drawing equal half-circles on each side. Because the wind keeps trying to push the airplane off course, you have to keep adjusting how steeply you bank so that both loops end up the same size and shape over the ground.
Context Anchor
Seen in ground reference maneuver training and in the Airplane Flying Handbook as a skill related to wind correction, smooth turning, and visual control of the airplane over a ground path.
Derivation
Named for the shape the flight path traces over the ground -- two connected half-circles that together look like the letter S, with the road forming the line that the S crosses.
Why Pilots Care
Develops precise coordination, timing, and wind-correction skills needed for safe low-altitude flight and traffic pattern operations.
Intuition Check
Do not think of this as simply making loose S-shaped turns near a road. In this maneuver, the road is the reference line, the crossings are planned, and the turns are adjusted so the ground path stays even.
Example Sentence 1
The instructor had her practice S-turns across the road into the wind first, so she could feel how the bank angle needed to change throughout each half-circle.
Example Sentence 2
Before starting lazy eights, the instructor had the pilot refine wind awareness by flying S-turns across the road at pattern altitude.