ACS tolerances

The Private Pilot Airplane ACS (FAA-S-ACS-6C, effective May 31, 2024) anchors normal-landing tolerances around two ideas: a stabilized approach in the recommended configuration at the recommended airspeed, and a touchdown at the proper pitch attitude within the first third of the runway. There's no single numerical airspeed tolerance on final — instead, the standard is "the manufacturer's recommended airspeed; if not recommended, no more than 1.3 V_SO."

The tolerances at a glance

Parameter	Target	Tolerance	Reference
Approach airspeed	Manufacturer-recommended (or 1.3 V_SO)	±5 KIAS	V.B.S2
Touchdown location	First third of the runway	Within first third	V.B.S3
Touchdown pitch	Proper landing attitude (nose up, mains first)	No flat / no nose-first	V.B.S3

Plus structural requirements:

• Stabilized approach in the recommended configuration — V.B.S1, S2
• Touchdown on the centerline — V.B.S3
• Crosswind correction throughout the landing roll — V.B.S4
• Directional control during after-landing roll — V.B.S5

Approach airspeed ±5 KIAS

Anchored to the manufacturer's recommended final approach speed (V_REF). If the POH gives a value (typical 60–70 KIAS for a trainer at landing weight), use that. If not, use 1.3 × V_SO (1.3 × power-off stall speed in landing config).

Tolerance is ±5 KIAS — tighter than the climb tolerance (V.A: +10/−5). On approach, both ends matter:

• Too slow risks a stall in the round-out / flare.
• Too fast uses more runway (floats) and risks porpoising.

Touchdown in the first third

V.B.S3 requires touchdown within the first third of the runway (not the first 200 feet — that's the short-field standard, F). Touching down past the first third is a bust even if the touchdown itself is otherwise normal.

Touchdown pitch

The airplane must touch down on the main gear first, with the nose still off the runway. A flat touchdown (all three wheels at once) is a bust. A nose-wheel-first touchdown is a worse bust (porpoise risk; nose gear damage).

Stabilized approach

V.B.S1 and S2 together require the airplane to be stabilized on final — speed, descent path, configuration, and power should all be set and steady before short final. A stabilized approach by 500 ft AGL is the industry standard; the ACS doesn't publish a numerical altitude but DPEs use the same yardstick.

Crosswind correction throughout

V.B.S4 requires active crosswind correction through the landing roll, not just during the approach. After touchdown:

• Aileron into the wind progressively increases as airspeed decreases.
• Rudder for directional control as nose-wheel steering takes over.

Directional control on rollout

V.B.S5 specifically calls out the after-landing roll — the airplane must track the centerline through the rollout without skipping, drifting, or weathervaning into the crosswind.