The aim of this study is to identify the effect of the increase of the situation demands, with or without a thread, on military helicopter pilot's cognitive load, depending on their skills acquisition (at the beginning, midway and end of training course). This study is carried out on a simulator, in virtual reality and allows to identify the moments of cognitive load enhancement and the associated indicators such as subjective, physiological and behavioural indicators. Recommendations will be done to go towards an individualization of the lessons during the pilots education, by anticipating an overload which has a deleterious effect on learning.