What is V_MC?

Reference: 14 CFR 23.2135

V_MC is the calibrated airspeed at which, following the sudden critical loss of thrust, it is possible to maintain control of the airplane. For multi-engine airplanes, V_MC must be determined, if applicable, for the most critical configurations used in takeoff and landing operations.

Directional control has been lost when full rudder deflection is applied towards the operating engine, and the aircraft begins to yaw toward the inoperative engine.

What is a V_MC Demonstration?

Reference: FAA Fact Sheet – Vmc Scenario Training

A V_MC demonstration teaches recognition of reduced directional control with one engine inoperative and the recovery needed to regain control.

The airplane is slowed gradually in the prescribed training configuration. Recovery begins at the first indication of directional-control loss, stall warning, or buffet, whichever occurs first.

Related: Multi-Engine Airplanes: How Aircraft Manufacturers Determine VMC

How to Perform a V_MC Demonstration

Notes:

• An actual demonstration of V_MC may not be possible under certain conditions of density altitude or with airplanes whose V_MC is equal to or less than V_S. Under those circumstances, a V_MC demonstration may be conducted by artificially limiting rudder travel to simulate maximum available rudder. When limiting rudder travel, a speed well above VS (approximately 20 knots) is recommended.
• The following procedures are generalized. Procedures, including immediate-action items, must be accomplished as detailed in the AFM/POH and the appropriate checklist.

Pre-Maneuver Checks and Configuration

• Clear the area
• Heading established and noted
• Altitude established:
  • No lower than 3,000' AGL or the manufacturer's recommended altitude (whichever is higher)
• Position near a suitable emergency landing area and away from hazards
• Set power and aircraft configuration:
  • Perform the clean (cruise) configuration flow, leaving the landing gear retracted
  • Set the flaps to the normal takeoff setting
  • Set the trim for takeoff and do not readjust it during the maneuver
  • Set the cowl flaps for takeoff
  • Establish a normal cruise speed, or an airspeed below V_FE, if flaps are extended

Related:

• Visual Scanning and Collision Avoidance: Visual Clearing Procedures
• Basic Flight Maneuvers: Pre-Maneuver Configuration Flows

Execution

1. Simulate a failed engine by retarding the throttle lever of the critical engine to idle.
2. Slow the airplane to 10 knots above V_SSE or V_YSE, as appropriate, or to the manufacturer's recommended speed.
3. Apply full power to the operative engine while maintaining the entry heading.
4. Establish a bank angle not to exceed 5° toward the operating engine, as required for best performance and controllability
5. Slowly increase pitch attitude to decrease airspeed by one knot per second. A rapid airspeed reduction can be hazardous and does not demonstrate the maneuver adequately.
6. Adjust aileron input as needed to maintain the desired bank angle as airspeed decreases.
7. Maintain heading as long as possible by increasing rudder input.
8. Recognize, announce, and recover at the first sign of a loss of directional control, stall warning, or buffet, whichever occurs first.

Recovery

1. Simultaneously reduce power on the operative engine and decrease the AOA as necessary to regain airspeed and directional control.
2. Reduce rudder pressure as the throttle is reduced to maintain directional control.
3. Once above V_MC and control is regained, smoothly advance the throttle on the operative engine to full power. Apply rudder pressure as needed to maintain the entry heading.
4. Accelerate to V_SSE or V_YSE, as appropriate. Do not use the failed engine (simulated).
5. Recover to the original heading.

Exit

1. Return to cruise speed with both engines, trimming as necessary.
2. Complete the cruise checklist.

Sideslip During the V_MC Demonstration

During the V_MC demonstration, the pilot applies rudder pressure to maintain directional control. The loss of control occurs in a sideslip. V_MC is not determined under zero-sideslip conditions during aircraft certification; therefore, it is not part of a V_MC demonstration.

A zero-sideslip condition may be established after the initial V_MC recovery. The ACS requires acceleration to V_SSE or V_YSE, as appropriate.

Related: Multi-Engine Airplanes: Zero Sideslip

Safety Considerations for V_MC Demonstrations

• Airplanes with normally aspirated engines lose power as altitude increases because the air density entering the engine's induction system decreases. This lowers V_MC below stall speed at higher altitudes. Therefore, recover at the first indication of loss of directional control, stall warning, or buffet.
• The rudder-limiting technique avoids the hazards of spinning caused by stalling under high asymmetric power, yet effectively demonstrates the loss of directional control.
• Do not perform this maneuver by increasing the pitch attitude to a high angle with both engines operating and then reducing power on the critical engine. This technique is hazardous and may result in loss of airplane control.
• Instructors should be alert for any sign of an impending stall. The learner may focus so much on the maneuver's directional control that they miss impending stall indications.
• Follow the airplane manufacturer's guidance on the CG location during slow-flight maneuvers. Generally, a forward CG aids in stall recovery, spin avoidance, and spin recovery.

Related: Multi-Engine Airplanes: Critical Density Altitude

Common Errors for V_MC Demonstrations

• Improper entry procedures, including pitch attitude, bank attitude, and airspeed
• Failure to recognize an imminent loss of directional control
• Initiating recovery steps too early
• Failure to use proper recovery procedures

Airman Certification Standards for V_MC Demonstrations

References: FAA-S-ACS-6, FAA-S-ACS-7, FAA-S-ACS-25

Airspeed Reduction	Recovery Airspeed	Bank	Heading
Approximately 1 knot per second	Maintain VSSE/VYSE +10/-5 KIAS (PVT) ±5 KIAS (COM, CFI)	Not to exceed 5° toward the operating engine	±20°