Common errors

S-turn errors split into two families: failures of the bank-modulation physics (which produce unequal semicircles), and failures of the road-crossing timing (which produce non-perpendicular or banked crossings). The seven below cover the common faults.

1. Fixed bank through each semicircle → unequal radii

What it looks like: the downwind semicircle bulges outward, the upwind one tightens inward. From above, the figure looks asymmetric rather than a clean balanced S.

Why: treating bank as constant within each semicircle rather than modulating it as heading rotates.

Fix: as heading rotates through the downwind semicircle, continuously shallow the bank from steepest at entry to shallowest at the road. Reverse for the upwind side. Think of bank as a continuous knob, not a switch.

2. Not wings-level at the road crossing

What it looks like: the airplane crosses the road with 5–10° of residual bank, or worse, mid-roll.

Why: mistimed the rate of roll-out — usually the pilot is fighting to reduce bank but doesn't reach wings-level until past the road.

Fix: lead with the road as the target. Plan the roll-out so wings-level coincides with the airplane being directly over the road. If you're rolling out at the road, you started too late.

3. Not perpendicular at the road crossing

What it looks like: the airplane crosses the road wings-level but the heading is 10–20° off perpendicular.

Why: the semicircle wasn't a full 180° — the bank reduction finished too soon (under-banked semicircle) or too late (over-banked semicircle).

Fix: check the road's relationship to the airplane as you approach. The road should appear to slide under perpendicular to the nose at the crossing. If it's sliding under at an angle, you have time to add or release bank before the crossing.

4. Drift along the road

What it looks like: successive crossings of the road are not at the same point — the figure walks down the road.

Why: the two semicircles aren't equal radii, so each completes at a slightly different point.

Fix: this is downstream of #1. Fix the bank modulation and the drift goes away.

5. Altitude bust during steepest portion

What it looks like: altitude unwinds 50–100 ft during the downwind semicircle's steepest portion.

Why: not adding back pressure as bank steepens — same physics as the steep turn altitude bust (A).

Fix: anticipate the back pressure. As bank steepens past 30°, call it out aloud.

6. Airspeed bleed during the steep semicircle

What it looks like: airspeed drops 10–15 kt during the downwind semicircle.

Why: over-pulling on the elevator to hold altitude in a steep bank.

Fix: reduce bank to bring the nose up if altitude is sinking; don't pull harder at the same bank.

7. Entering on the wrong heading

What it looks like: entering upwind instead of downwind, or entering at an angle to the road.

Why: didn't identify wind direction before commit, or chose the wrong road orientation.

Fix: verbalize the wind direction and your planned entry heading to the DPE before turning toward the road. Pick a road perpendicular to the wind; enter heading downwind.

How errors compound. Bank-modulation errors (#1) produce unequal radii, which produce drift along the road (#4) and force timing errors at the next crossing (#2, #3). One root cause, three downstream busts. The fix to almost every S-turn issue is continuous bank awareness: name the bank to yourself out loud at the quarter-point of each semicircle.