Vmc Demonstration

Definition of V_MC

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?

V_MC demonstrations closely resemble how manufacturers determine V_MC during the airplane’s certification process:

1. Power on the critical engine is reduced to idle.
2. The airplane is configured according to the V_MC certification criteria.
3. The pitch attitude is increased to reduce airspeed gradually until a loss of control occurs.
4. Proper recovery procedures are performed to reestablish controllable, single-engine flight.

How to Perform a V_MC Demonstration

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
• 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 appropriate

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 the manufacturer’s recommended speed.
3. Apply full power on the operative engine while maintaining the entry heading.
4. Bank the aircraft up to 5° towards the side of the operative engine and sustain 1/2 ball deflection toward the operative engine.

5. Increase the pitch attitude slowly to decrease airspeed by one knot per second. A fast airspeed reduction can be hazardous and does not provide an adequate demonstration.
6. Aileron control deflection should be increased as necessary to keep the bank angle constant as the ailerons become less effective 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. Reduce the operating engine’s power sufficiently promptly and simultaneously and decrease the AOA as necessary to regain airspeed and directional control. Rudder pressure needs to be reduced to maintain directional control as the throttle is reduced.

2. 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.
3. Accelerate to V_XSE or V_YSE as appropriate. Do not use the failed engine (simulated).
4. 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 under conditions of sideslip. V_MC is not determined under conditions of zero-sideslip during aircraft certification; therefore, it is not part of a V_MC demonstration.

A zero-sideslip may be established after the initial V_MC recovery procedure is completed. Pilot certification standards require the pilot to accelerate to V_XSE or V_YSE as appropriate during the recovery, which is normally maintained in a zero-sideslip condition for best climb performance.

Safety Considerations for V_MC Demonstrations

• Airplanes with normally aspirated engines will lose power as altitude increases because of the reduced density of the air entering the engine’s induction system. This loss of power will result in a V_MC lower than the stall speed at higher altitudes. Therefore, recovery should be made at the first indication of loss of directional control, stall warning, or buffet.

• The rudder limiting technique avoids the hazards of spinning as a result of stalling with high asymmetrical power, yet is effective in demonstrating 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 be focused on the maneuver’s directional control aspect to the extent that impending stall indications go unnoticed.
• Follow the airplane manufacturer’s guidance regarding the CG location during slow flight maneuvers. Generally, a forward CG aids in stall recovery, spin avoidance, and spin recovery.

Common Errors for V_MC Demonstrations

• Inadequate knowledge of the causes of loss of directional control at airspeeds less than V_MC, factors affecting V_MC, and safe recovery procedures
• 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