▁such ▁an ▁attitude ▁change ▁in ▁the ▁first ▁place ▁is ▁that ▁human ▁expos ure ▁to ▁a ▁rot ational ▁acceleration ▁of ▁~ 1 ▁degrees ▁per ▁second ² ▁or ▁lower ▁is ▁below ▁the ▁detection ▁threshold ▁of ▁the ▁sem ic irc ular ▁can als . ▁Rol ling ▁wings - level ▁from ▁such ▁an ▁attitude ▁may ▁cause ▁an ▁ill usion ▁that ▁the ▁aircraft ▁is ▁bank ing ▁in ▁the ▁opposite ▁direction . ▁In ▁response ▁to ▁such ▁an ▁ill usion , ▁a ▁pilot ▁will ▁tend ▁to ▁roll ▁back ▁in ▁the ▁direction ▁of ▁the ▁original ▁bank ▁in ▁a ▁correct ive ▁attempt ▁to ▁reg ain ▁the ▁per ception ▁of ▁a ▁level ▁attitude . ▁ ▁Gra vey ard ▁spin ▁ ▁The ▁gra vey ard ▁spin ▁is ▁an ▁ill usion ▁that ▁can ▁occur ▁to ▁a ▁pilot ▁who ▁enters ▁into ▁a ▁spin ▁and ▁is ▁character ized ▁by ▁the ▁pilot ▁becoming ▁less ▁aware ▁of ▁the ▁sense ▁of ▁rotation ▁induced ▁by ▁the ▁spin ▁as ▁the ▁spin ▁continues . ▁As ▁the ▁pilot ▁becomes ▁less ▁aware ▁of ▁the ▁spin , ▁any ▁correction ▁of ▁the ▁spin ▁may ▁cause ▁the ▁pilot ▁to ▁sense ▁that ▁he ▁or ▁she ▁is ▁spin ning ▁in ▁the ▁opposite ▁direction . ▁As ▁an ▁example , ▁if ▁the ▁air plane ▁is ▁spin ning ▁to ▁the ▁right ▁but ▁goes ▁un not iced ▁for ▁a ▁period ▁of ▁time ▁sufficient ▁for ▁the ▁pilot ▁to ▁become ▁des ens it ized ▁to ▁the ▁magnitude ▁of ▁the ▁spin , ▁a ▁small ▁adjust ment ▁to ▁the ▁left ▁rud der ▁may ▁leave ▁the ▁pilot ▁with ▁a ▁sens ation ▁of ▁spin ning ▁to ▁the ▁left . ▁As