ACS tolerances

The Private Pilot Airplane ACS (FAA-S-ACS-6C, effective May 31, 2024) anchors short-field tolerances around runway utilization, brakes-held power application, and a V_X-then-V_Y climb sequence. The climb tolerance after V_Y transition is the same as the normal takeoff (A); the new structural items are obstacle-clearance specific.

The tolerances at a glance

Parameter	Target	Tolerance	Reference
Climb airspeed (V_X)	Until obstacle cleared	V_X (no published ±)	V.E.S3
Climb airspeed (V_Y)	After obstacle clearance	V_Y +10/−5 KIAS	V.E.S3
Runway use	Full available runway	At the threshold	V.E.S1
Power application	Takeoff power, brakes held	Then release	V.E.S2

Plus structural requirements:

• Use the maximum available runway — V.E.S1 (apply brakes during the run-up so the airplane stays put)
• Apply takeoff power smoothly before brake release — V.E.S2
• Rotate at the recommended airspeed — V.E.S2
• Climb at V_X until obstacle clearance, then transition to V_Y — V.E.S3
• Wind-drift correction throughout — V.E.S4

V_X until obstacle clearance

V.E.S3 requires the climb at V_X until the obstacle is cleared. The ACS doesn't publish a numerical ± tolerance on V_X — but a wandering airspeed during V_X climb signals weak speed control and the DPE will note it.

V_X is lower than V_Y by typically 5–10 knots in a trainer. The pitch attitude required is higher. Confirm by airspeed; don't fly by pitch alone.

V_Y +10 / −5 KIAS after the obstacle

After the obstacle is cleared (or after reaching a safe altitude with no obstacle), the climb transitions to V_Y with the same tolerance as the normal takeoff (A): +10 / −5 KIAS, asymmetric in favor of flying fast.

Use the maximum runway

V.E.S1 requires the airplane to be at the runway threshold for takeoff. Beginning the roll a few hundred feet down the runway "to taxi onto the centerline more easily" is a bust — you've discarded usable runway you might need to abort, accelerate, or clear the obstacle.

The corollary: apply brakes during the run-up so the airplane doesn't creep forward and waste runway.

Brakes held, power up, then release

V.E.S2 implies the brakes-held power application sequence: full power applied before brake release, with engine and instrument indications confirmed normal first. Every foot of roll is then at takeoff power, not at the transient power level of a normal-takeoff brake-already-released start.

The DPE evaluates by watching the throttle, brakes, and instrument scan during the run-up to brake release.