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S-Turns

Introduction:

  • Develops the ability to compensate for drift during turns by flying semicircles of equal radii on each side of a reference line on the ground [Figure 1]
    • You may need to be creative but the end state is a straight line, approximately 1 mile or longer in length
  • Builds wind drift skills developed with the rectangular course but introduces constant turns
  • The maneuver is flown to arrive at a specified point, at specified headings, while compensating for drift, orienting the flight path with ground references by changing roll rate and angle of bank to establish correction to compensate for ground speed changes

WARNING:
All procedures here are GENERALIZED for learning.
Fly the maneuver in accordance with the Pilot Operating Handbook (POH)
and/or current Standard Operating Procedures (SOPs)


S-Turns Procedure:

  1. Determine wind direction
    • This is important for the entry heading and reference line
  2. Perform clearing turns looking for traffic and ground obstructions
  3. Select a reference line perpendicular to the direction of the wind
    • Select an area where an emergency landing can be made if necessary
    • May be performed on any straight line such as a road, fence, or railroad
    • Select the point on upwind and turn back for a downwind entry
  4. Establish and maintain a cruise airspeed to enter the maneuver between 600-1,000' AGL
  5. Enter on a downwind to one side of the selected point, at a distance equal to the desired radius of the turn
  6. When abeam (perpendicular) or over the reference line (highest ground speed), begin the turn to roll into the upwind
    • Apply adequate wind-drift correction to track a constant radius turn on each side of the selected reference line
      • Start with a steep bank, as ground speed is highest
      • Transition to a moderate angle of bank around 90° as ground speed begins to slow
      • Shallow rolling out around 180° as ground speed is lowest
      • Roll wings level at 180° so as to be straight and level directly over and perpendicular to the reference line
      • Crabbing is also necessary (crab in during the downwind half of the circle, crab out during the upwind half of the circle)
  7. When abeam (perpendicular) or over the reference line (lowest ground speed), begin the turn to roll back into the downwind
    • Start with a shallow bank, as ground speed is lowest
    • Transition to a moderate angle of bank around 90° as ground speed begins to rise
    • Steepen the bank angle to roll out around 180° as ground speed is highest
    • Roll wings level at 180° so as to be straight and level directly over and perpendicular to the reference line
    • Crabbing is also necessary (crab in during the upwind half of the circle, crab out during the downwind half of the circle)
  8. Depart on entry heading and resume normal cruise
    • Trim as necessary
  9. Complete cruise flow/checklist
Airplane Flying Handbook, Figure 6-5. S-Turns
Airplane Flying Handbook, S-Turns

Common Errors:

  • Failure to adequately clear the area
  • Poor coordination
  • Gaining or losing altitude
  • Misjudging the rate of turn
  • Inability to visualize the half circle ground track
  • Poor timing in beginning and recovering from turns
  • Faulty correction for drift
  • Inadequate visual lookout for other aircraft

Airman Certification Standards:

Conclusion:

  • You must divide attention between airplane control and the ground track while maintaining coordinated flight
  • Rolling into an angle of bank too quickly will not result in crossing perpendicular to the reference line
  • Rolling into an angle of bank too slowly will result in a portion of the maneuver being straight and level to return to profile
  • Consider practicing maneuvers on a flight simulator to introduce yourself to maneuvers or knock off rust

References: