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How does VMCG change with increasing field elevation and temperature?
  • A
    decreases, because VMCG is expressed in IAS, which decreases with constant TAS and decreasing density.
  • B
    increases, because VMCG is related to V1 and VR and those speeds increase if the density decreases.
  • C
    increases, because at a lower density a larger IAS is necessary to generate the required rudder force.
  • D
    decreases, because the engine thrust decreases.

In simple words, VMCG is established as being the lowest speed at which rudder effect alone is sufficient to regain and maintain directional control after a sudden engine failure.

The major factor that affects VMCG is the difference in engine thrust. VMCG will therefore be lower at higher airport elevations and at a higher OAT, due to the associated lower thrust. Conversely, VMCG will be higher at lower airport elevations and at a lower OAT.

If conditions are hot, high and humid the air is less dense. This reduces thrust and, consequently, when you lose the critical engine on take-off, there is less yawing effect from asymmetric thrust than there would be in denser air.

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