The object of S-turns is to fly a pattern of two half circles of equal size on opposite sides of the reference line. [Figure 20-11] The maneuver should be performed at a constant altitude of 600 to 1,000 feet above the terrain. S-turns may be started at any point; however, during early training it may be beneficial to start on a downwind heading. Entering downwind permits the immediate selection of the steepest bank that is desired throughout the maneuver. The discussion that follows is based on choosing a reference line that is perpendicular to the wind and starting the maneuver on a downwind heading.

As the gyroplane crosses the reference line, immediately establish a bank. This initial bank is the steepest used throughout the maneuver since the gyroplane is headed directly downwind and the groundspeed is at its highest. Gradually reduce the bank, as necessary, to describe a ground track of a half circle. Time the turn so that as the rollout is completed, the gyroplane is crossing the reference line perpendicular to it and heading directly upwind. Immediately enter a bank in the opposite direction to begin the second half of the “S.”

Since the gyroplane is now on an upwind heading, this bank (and the one just completed before crossing the reference line) is the shallowest in the maneuver.

Gradually increase the bank, as necessary, to describe a ground track that is a half circle identical in size to the one previously completed on the other side of the reference line. The steepest bank in this turn should be attained just prior to rollout when the gyroplane is approaching the reference line nearest the downwind heading. Time the turn so that as the rollout is complete, the gyroplane is perpendicular to the reference line and is again heading directly downwind.

In summary, the angle of bank required at any given point in the maneuver is dependent on the groundspeed. The faster the groundspeed, the steeper the bank; the slower the groundspeed, the shallower the bank. To express it another way, the more nearly the gyroplane is to a downwind heading, the steeper the bank; the more nearly it is to an upwind heading, the shallower the bank. In addition to varying the angle of bank to correct for drift in order to maintain the proper radius of turn, the gyroplane must also be flown with a drift correction angle (crab) in relation to its ground track; except of course, when it is on direct upwind or downwind headings or there is no wind. One would normally think of the fore and aft axis of the gyroplane as being tangent to the ground track pattern at each point. However, this is not the case. During the turn on the upwind side of the reference line (side from which the wind is blowing), crab the nose of the gyroplane toward the outside of the circle. During the turn on the downwind side of the reference line (side of the reference line opposite to the direction from which the wind is blowing), crab the nose of the gyroplane toward the inside of the circle. In either case, it is obvious that the gyroplane is being crabbed into the wind just as it is when trying to maintain a straight ground track. The amount of crab depends upon the wind velocity and how nearly the gyroplane is to a crosswind position.

The stronger the wind, the greater the crab angle at any given position for a turn of a given radius. The more nearly the gyroplane is to a crosswind position, the greater the crab angle. The maximum crab angle should be at the point of each half circle farthest from the reference line.

A standard radius for S-turns cannot be specified, since the radius depends on the airspeed of the gyroplane, the velocity of the wind, and the initial bank chosen for entry.

This training maneuver requires you to fly constant radius turns around a preselected point on the ground using a maximum bank of approximately 40°, while maintaining a constant altitude. [Figure 20-12] Your objective, as in other ground reference maneuvers, is to develop the ability to subconsciously control the gyroplane while dividing attention between the flight path and ground references, while still watching for other air traffic in the vicinity.

The factors and principles of drift correction that are involved in S-turns are also applicable in this maneuver. As in other ground track maneuvers, a constant radius around a point will, if any wind exists, require a constantly changing angle of bank and angles of wind correction. The closer the gyroplane is to a direct downwind heading where the groundspeed is greatest, the steeper the bank, and the faster the rate of turn required to establish the proper wind correction angle.

The more nearly it is to a direct upwind heading where the groundspeed is least, the shallower the bank, and the slower the rate of turn required to establish the proper wind correction angle. It follows then, that throughout the maneuver, the bank and rate of turn must be gradually varied in proportion to the groundspeed.

The point selected for turns around a point should be prominent and easily distinguishable, yet small enough to present a precise reference. Isolated trees, crossroads, or other similar small landmarks are usually suitable. The point should be in an area away from communities, livestock, or groups of people on the ground to prevent possible annoyance or hazard to others. Since the maneuver is performed between 600 and 1,000 feet AGL, the area selected should also afford an opportunity for a safe emergency landing in the event it becomes necessary.

To enter turns around a point, fly the gyroplane on a downwind heading to one side of the selected point at a distance equal to the desired radius of turn. When any significant wind exists, it is necessary to roll into the initial bank at a rapid rate so that the steepest bank is attained abeam the point when the gyroplane is headed directly downwind. By entering the maneuver while heading directly downwind, the steepest bank can be attained immediately. Thus, if a bank of 40° is desired, the initial bank is 40° if the gyroplane is at the correct distance from the point. Thereafter, the bank is gradually shallowed until the point is reached where the gyroplane is headed directly upwind. At this point, the bank is gradually steepened until the steepest bank is again attained when heading downwind at the initial point of entry.

Just as S-turns require that the gyroplane be turned into the wind, in addition to varying the bank, so do turns around a point. During the downwind half of the circle, the gyroplane’s nose must be progressively turned toward the inside of the circle; during the upwind half, the nose must be progressively turned toward the outside. The downwind half of the turn around the point may be compared to the downwind side of the S-turn, while the upwind half of the turn around a point may be compared to the upwind side of the S-turn.

As you become experienced in performing turns around a point and have a good understanding of the effects of wind drift and varying of the bank angle and wind correction angle, as required, entry into the maneuver may be from any point. When entering this maneuver at any point, the radius of the turn must be carefully selected, taking into account the wind velocity and groundspeed, so that an excessive bank is not required later on to maintain the proper ground track.