Using Vmcg-Limited V1, Controllability Issues on Contaminated Runways and in Crosswind

Abstract

Vmcg, or ground minimum control speed, is established by aircraft manufacturers during the aircraft certification process. Vmcg is used as a limiting speed for V1 (decision speed) when performing takeoff performance calculations. Performance calculations on contaminated and slippery runways will result in a V1 speed equal to Vmcg-limited V1 for a wide range of takeoff weights when using aircraft manufacturer procedures in a flight crew operationsmanual or computer calculations based on theV1−min policy. In this paper, itwill be shown thatVmcg will not be a safe speed to continue a takeoff after an engine failure in strong crosswind or reduced runway surface friction conditions. A model is used to determine the effect of these environmental conditions on lateral deviation. Apart from the continued takeoff, the lateral deviation in the rejected takeoff after an engine failure was also calculated under different environmental conditions. This resulted in advice for the use of a differential braking technique to prevent a runway excursion if a runway is not dry. A method to mitigate the risk of runway excursion on contaminated and slippery runways is presented. An evaluation, conclusions, and subjects for further research are also presented.