ACS tolerances

The Private Pilot Airplane ACS (FAA-S-ACS-6C, effective May 31, 2024) anchors emergency descent tolerances around POH-recommended configuration, structural limit respect, positive load factor, and level-off at the assigned altitude. The airspeed tolerance is anchored to the POH-published emergency descent airspeed rather than a fixed value because the limit varies by airplane and configuration.

The tolerances at a glance

Parameter	Target	Tolerance	Reference
Airspeed	POH-recommended emergency descent	Within published limits (do not exceed V_NE, V_NO, V_LE, V_FE as applicable)	IX.A.S1, S2
Load factor	Positive (no negative-g pushovers)	Positive throughout	IX.A.S2
Structural limits	V_NE / V_NO / V_LE / V_FE	No exceedance	IX.A.S2
Level-off altitude	Assigned altitude	±100 ft	IX.A.S3
Final configuration	Cruise configuration at level-off	Reconfigured	IX.A.S3

Plus structural requirements:

• Clear the area before beginning — IX.A.S1
• Establish the recommended emergency descent configuration (per POH) — IX.A.S1
• Maintain positive load factor and stay within structural limits — IX.A.S2
• Level off at the assigned altitude in cruise configuration — IX.A.S3

Airspeed — within POH limits

The maneuver requires the airspeed to stay within the published structural limits — not at them, not beyond them. The relevant limits:

• V_NE (never exceed) — the airplane's red-line airspeed. Crossing this risks structural failure even in calm air.
• V_NO (max structural cruising) — the airplane's yellow-arc top. Above this, the airplane is in the "caution range" — only smooth air is acceptable. Most emergency descents target a value below V_NO to retain turbulence margin.
• V_LE (max gear extended) — if gear is down. Crossing this risks gear-door damage or gear strut overload.
• V_FE (max flap extended) — if flaps are down. Crossing this risks flap damage or loss.

The lowest applicable limit governs. If the descent is flown with gear down, V_LE caps the airspeed; with flaps down, V_FE caps it. Often, clean configuration is chosen for the descent precisely because V_NE (or V_NO) is highest in clean — giving the maximum descent rate envelope.

Positive load factor

IX.A.S2 prohibits negative-g maneuvers (pushovers). A pilot who pushes the nose down aggressively to start the descent can put the airplane in negative-g momentarily; many trainer airplanes are not certified for sustained negative g and may have fuel system or oil system issues during it.

The technique is a banked turn, which produces positive load factor (n > 1.0) throughout. The bank does the descending work without requiring nose-down pitch input through neutral g.

Structural limits — absolute

The descent's structural-limit respect is the defining tolerance of the maneuver. The DPE evaluates:

• Did the airspeed stay below the relevant red line?
• Did the configuration match the airspeed (no flap extension above V_FE)?
• Was the recovery smooth (no over-G on pull-out)?

A pilot who exceeds V_NE during the descent, even briefly, has busted the maneuver — and demonstrated that under stress they don't respect the airframe's limits. The standard exists because the descent's value is rapid altitude loss within survivable airplane limits; exceeding the limits doesn't make the emergency descent better, it makes it the cause of a different emergency.

Level-off ±100 ft

The level-off precision matches the basic instrument climb / descent tolerance (VIII.B.S2, VIII.C.S2). Lead by 10% of the descent rate (cross-ref to VIII.B PRI for the math). At 3,000 fpm, lead by 300 ft.

Cruise configuration at level-off

IX.A.S3 requires the airplane to be in cruise configuration at the level-off altitude — gear up, flaps up, cruise power, trimmed for level flight. The maneuver isn't complete until the airplane is back in normal cruise. A pilot who levels off at the right altitude but still has gear and flaps extended hasn't completed the maneuver to standard.

The "emergency" doesn't relax the structural limits — it makes respecting them more important. A pilot who treats V_NE as a guideline during an emergency has lost the maneuver's framework. The maneuver is precisely a disciplined descent — aggressive but controlled.