ACS tolerances

The Private Pilot Airplane ACS (FAA-S-ACS-6C, effective May 31, 2024) anchors instrument turn tolerances around altitude maintenance during the turn, airspeed, and rollout precision on the target heading. The standard rate turn is the implicit configuration — bank is set by airspeed (TAS / 10 + 7).

The tolerances at a glance

Parameter	Target	Tolerance	Reference
Altitude	Entry altitude (held through turn)	±100 ft	VIII.D.S2
Airspeed	Cruise / entry airspeed	±10 KIAS	VIII.D.S2
Rollout heading	Target heading	±10°	VIII.D.S2

Plus structural requirements:

• Standard rate turn by reference to instruments — VIII.D.S1
• Roll in and out coordinated — implicit in S1

Altitude ±100 ft

Anchored to entry altitude — the airplane must hold altitude through the turn. The load factor at bank requires back pressure (V_S × √n; at 17° bank, n = 1.05). A pilot who doesn't anticipate the back pressure busts altitude on the low side.

The standard is "throughout the turn" — not just at the end. Mid-turn sag is a bust even if the rollout altitude matches entry.

Airspeed ±10 KIAS

Anchored to entry airspeed. Some airspeed bleed in the turn is normal because drag increases with load factor; the pilot may need a slight power addition to hold airspeed.

A bust pattern: airspeed bleeds during the turn (because back pressure is increased) and the pilot doesn't add power, busting the airspeed window.

Rollout heading ±10°

The most distinctive tolerance of the maneuver. The airplane must be wings-level on the target heading within ±10°. Two failure modes:

• Overshoot the heading (continue past the target by more than 10°) — usually because the rollout was reactive instead of anticipated.
• Undershoot the heading (settle short of the target by more than 10°) — usually because the rollout lead was too aggressive, or the turn was abandoned early.

The anticipation rule: lead by half the bank angle. At 17° bank, lead by ~8°. This is the difference between a coordinated rollout that arrives on target and one that requires a corrective bank in the wrong direction.

Standard rate turn

VIII.D.S1 implies standard rate (3°/sec). The bank angle to achieve standard rate varies with airspeed:

• TAS ÷ 10 + 7 is the approximation. At 80 kt → 15°; at 100 kt → 17°; at 120 kt → 19°.
• Turn coordinator is the primary instrument for verifying standard rate.

A bank significantly steeper or shallower than the calculated rate is a deviation from S1 — the standard expects the rate, not just the eventual heading change.

The turn coordinator becomes the primary bank instrument. In other phases, the HI is primary for bank (it's holding heading); in the turn, the turn coordinator is primary because it's directly showing the rate of heading change. The HI is consulted at the rollout window for anticipation.