Commercial pilot · ACS CA.X.B

VMC Demonstration

The VMC demonstration shows the onset of lost directional control with one engine at idle, and the prompt, correct recovery.

This lesson is written for multi-engine land or multi-engine sea. You picked single-engine land: speeds, altitudes and procedures differ, so follow your POH/AFM and your instructor.

Why this one matters

Below VMC with asymmetric power, the airplane yaws and rolls toward the dead engine, and at low altitude that is fatal. The demonstration shows, at a safe altitude, what the edge feels like and that the recovery is to reduce power, not to add it, so the reflex is right if it ever happens for real.

Can’t miss

•Published VMC (the red line) is the slowest speed at which you can keep control with the critical engine suddenly inoperative, then hold straight flight with no more than 5° of bank. It is set under fixed conditions: sea-level standard day; maximum takeoff power on the operating engine; the critical engine windmilling with its propeller control in the takeoff position; the most unfavorable weight (the lightest) and the most unfavorable (aft) center of gravity; gear up; wing and cowl flaps and trim in the takeoff position; out of ground effect; no more than 5° of bank toward the operating engine; heading held within 20° with no more than 150 pounds of rudder force.(14 CFR 23.149 (now 23.2135); Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
•VMC is about directional control; VS is about the wing. Where the stall would come first (at altitude, or at light weight), a stall with asymmetric power can roll into a spin.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
•Configure per the manufacturer (or: gear up, flaps and cowl flaps for takeoff, trim for takeoff, propellers high RPM, critical engine idle with the propeller windmilling, the other at maximum power).(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S1)
•Enter in a single-engine climb attitude about 10 knots above VSSE or VYSE, whichever is higher, with up to 5° bank toward the operating engine, then slow about 1 knot per second, adding rudder.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S2-S4)
•Recover at the first sign of lost directional control, a stall warning or buffet: reduce power on the operating engine and lower the nose. Never add power to the "failed" engine.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S5-S6)
•Recover within 20° of the entry heading, then add power on the operating engine only and accelerate to VSSE or VYSE ±5 knots.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S7-S8)
•Complete the recovery no lower than 3,000 feet AGL, or the manufacturer's higher altitude.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Commercial Pilot ACS (FAA-S-ACS-7B), Appendix 2)

What you should know

VMC versus stall K1 · K2 · K3

Published VMC (the red line) is the slowest speed at which you can keep control with the critical engine suddenly inoperative, then hold straight flight with no more than 5° of bank. It is set under fixed conditions: sea-level standard day; maximum takeoff power on the operating engine; the critical engine windmilling with its propeller control in the takeoff position; the most unfavorable weight (the lightest) and the most unfavorable (aft) center of gravity; gear up; wing and cowl flaps and trim in the takeoff position; out of ground effect; no more than 5° of bank toward the operating engine; heading held within 20° with no more than 150 pounds of rudder force.(14 CFR 23.149 (now 23.2135); Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Your real VMC differs whenever the conditions do. It goes up with a windmilling propeller (feathering lowers it), an aft CG, lighter weight, more power on the operating engine, and less bank toward it. It goes down with less power (a normally aspirated engine at altitude; a turbocharged one only above its critical altitude), gear extended (keel effect), and ground effect.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Bank matters most: VMC rises more than 3 knots for each degree of bank less than 5°, and with the wings level control can be lost almost 20 knots above the published red line. Up to 5° toward the operating engine is the certification number, not the way you fly.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
The critical engine is the one whose failure is hardest to control: on twins with both propellers turning clockwise (seen from behind), the left, because of P-factor, accelerated slipstream, spiraling slipstream and torque. Twins with counter-rotating propellers (a Seminole or a Duchess) have no critical engine.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
VMC (red line): minimum control speed. VYSE (blue line): best rate of climb, or least loss, on one engine. VXSE: best angle on one engine. VSSE: safe single-engine speed, the slowest at which an engine may be intentionally failed in training.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Below VMC, the rudder can't make enough force to counter the yaw from the operating engine, so the airplane yaws and then rolls toward the inoperative engine.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
In a normally aspirated twin VMC falls as density altitude rises (less power), while the indicated stall speed stays about the same, so at some altitude they meet. In a turbocharged twin VMC stays roughly constant up to the critical altitude, then falls. Where they meet, a stall can come before loss of control.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)

Entry and recovery K4 · R1

Configure as the manufacturer says, with takeoff trim, at a safe altitude, clear of traffic. Enter in a single-engine climb attitude about 10 knots above VSSE or VYSE, whichever is higher, with up to 5° of bank toward the operating engine.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S1-S3)
Raise the nose slowly (about a knot per second), adding rudder to hold heading, until the first sign: full rudder and the heading still drifting, a stall warning or buffet.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S4-S5)
Recover: reduce power on the operating engine and lower the nose together. Once control returns, add power on the operating engine only and accelerate to VSSE or VYSE, holding the entry heading within 20°, before power comes back on the simulated failed engine.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S6-S8)
Where the stall would come before loss of control, an instructor can block part of the rudder travel to bring the loss of control well above the stall. That is an instructor technique only, and you still recover at the first sign of lost control, a stall warning or buffet.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
The recovery must be complete no lower than 3,000 feet AGL, or the manufacturer's higher recommendation: plan the entry altitude from that.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Commercial Pilot ACS (FAA-S-ACS-7B), Appendix 2)

Flying it safely R2 · R3

Configuring: a wrong configuration changes the VMC you meet; gear down or flaps out lowers it and hides the edge.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Maneuvering on one engine: every maneuver is flown with VMC in mind, at blue line or above, with zero sideslip (about 2-3° bank and the ball one-third to one-half out toward the operating engine).(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Distraction: watch heading, airspeed and the stall warning together; one person, the instructor or evaluator, is ready to restore power.(Risk Management Handbook (FAA-H-8083-2A))
Clear the area, and keep scanning for traffic while you handle the failure.(AC 90-48, Pilots' Role in Collision Avoidance)

On the flight

ACS standards

Configure per the manufacturer; enter about 10 knots above VSSE or VYSE; bank no more than 5° toward the operating engine; slow about 1 knot per second.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S1-S4)
Recover at the first sign, reducing power on the operating engine and lowering the nose, within 20° of entry heading; accelerate to VSSE or VYSE ±5 knots.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.B.S5-S8)

What your instructor is watching for

Your instructor watches for a correct configuration, a slow deceleration with increasing rudder, recognition of the first sign, the recovery by reducing power (never adding it on the idle engine), heading kept within 20°, acceleration to the right speed, and recovery complete above 3,000 feet AGL.

Scenarios

Decide what you would do first, then see the worked answer.

At full rudder the heading keeps drifting toward the idle engine.

What does this mean? See the worked answer

You've reached VMC. Reduce power on the operating engine and lower the nose.

Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes

The demonstration is planned at 10,000 feet density altitude in a normally aspirated twin.

What's the concern? See the worked answer

VMC may be below the stall speed there; the stall comes first, with asymmetric power. Fly it lower (still completing above 3,000 feet AGL), or the instructor limits rudder.

Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes

You lose directional control and instinctively push the idle engine's throttle forward.

What's wrong with that? See the worked answer

The recovery is to reduce power on the operating engine, not add power to the other; in a real failure that engine gives nothing.

Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes

Common mistakes

Slowing too quickly.
You overshoot the first sign.
Instead: About 1 knot per second.
Recovering by adding power to the idle engine.
Builds the wrong reflex.
Instead: Reduce power on the operating engine.
Flying it with the wings level.
Loss of control comes much faster than the red line suggests.
Instead: Up to 5° of bank toward the operating engine.

Now train it

Say it out loud, hear it asked, and take the quick check in this lesson’s practice pack. It tracks your shaky spots.

Train this lesson

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Sources

Airplane Flying Handbook (FAA-H-8083-3C): Transition to Multiengine Airplanes
Instrument Flying Handbook (FAA-H-8083-15B)
Risk Management Handbook (FAA-H-8083-2A)
Commercial Pilot ACS (FAA-S-ACS-7B): Areas IX and X (multiengine)
Your airplane's POH/AFM: Emergency Procedures; Performance
14 CFR 23.149 (now 23.2135): Minimum control speed

Study aid, not FAA guidance. Regulations change; check the current text at eCFR and the ACS. Checked against current sources 2026-11-13.