Think correct translation in English of aeronautic use of "gauchissement" is "wing warping". Perhaps the FP was an amateur of old times aeroplanes. Do he means by this word he was using rudder and the plane had some glide ?
Not sure others in the cockpit could understand this word, except if they have spoken of old times aviation before.
See:
Dictionnaire Collaboratif Français - Anglais
And:
Wing warping - Wikipedia, the free encyclopedia