What is VMC?

BTeter

Monday, June 12, 2023 at 06:54 PM ET

Verified

Key Takeaways:

Published V_MC in the POH is an aggressively determined minimum value from specific test conditions (e.g., up to 5° bank into the operating engine) and does not reflect the higher, variable actual V_MC encountered in real-world asymmetric flight.
Factors like banking into the dead engine (or maintaining level wings), higher aircraft weight combined with incorrect banking, and allowing excessive sideslip significantly increase the actual V_MC, making loss of control much more likely.
Exceeding actual V_MC or allowing a large sideslip can lead to a vertical fin stall, resulting in a rapid, uncontrolled roll and spin; pilots must understand these dynamics and be prepared to use all flight controls, including reducing thrust on the good engine, to maintain control.

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While the Pilot’s Operating Handbook shows V_MC for the aircraft, the V_MC in flight varies depending on many conditions. It’s similar to the published stall speed vs. the stall speed for your current load factor. Remember, you can stall the aircraft at any airspeed but only at one angle of attack. The same is true of loss of control during asymmetric flight, which can occur at any airspeed. When you lose an engine in a twin, the difference between the published V_MC and the actual V_MC for your conditions is critically important.

Published VMC