Chair flying / S-Turns Across a Road

S-Turns Across a Road

Fly two equal half-circles of constant radius on opposite sides of a straight road, varying bank against the wind to correct for drift, dividing attention between ground track and aircraft control.

Guided rehearsal is Premium ACS V.B: Ground Reference Maneuvers

Pre-Maneuver Checklist (CRAAC)

Clearing turns: two 90° turns or one 180° turn; look for traffic
Reference point: select a visual reference and set the heading bug
Altitude: the task's entry altitude; ground reference 600–1,000 ft AGL, slow flight and stalls finish at or above 1,500 ft AGL
Ground reference maneuvers enter at 600–1,000 ft AGL and hold altitude ±100 ft. Slow flight and stalls (and the commercial chandelles, lazy eights, and steep spiral) finish no lower than 1,500 ft AGL. Eights on pylons fly at pivotal altitude.
Airspeed: at or below Va (105 @ 2,325 lb / 90 @ 1,900 lb kt)
Configuration: fuel pump ON, lights ON, mixture RICH, flaps as needed

Setup

Select a straight road perpendicular to the wind
Clean configuration, 2,100 RPM (80–85 kt)
Descend to 600–1,000 ft AGL and set up to cross the road on the downwind

Execution

Cross the road wings level, entering downwind, and roll into the steepest bank
Groundspeed is highest downwind, so the steepest bank (up to 45°) is needed at the road crossing to hold the radius; bank is proportional to groundspeed throughout.
Shallow the bank through the half-circle as groundspeed decreases
Arrive wings level at the road again, then reverse into a matching half-circle on the other side

Recovery

Roll wings level at each road crossing; maintain altitude throughout

ACS tolerances

Altitude ±100 ft
Airspeed ±10 kt
Constant radius, wings level at each crossing

Common errors

Wrong bank at the crossing: not steepest when fastest (downwind)
Unequal half-circles from mis-timed drift correction
Gaining or losing altitude while managing the ground track