ually ▁cu ed ▁to ▁the ▁nature ▁of ▁the ▁error ▁or ▁contact ▁with ▁the ▁terrain ▁occurs . ▁One ▁of ▁the ▁most ▁famous ▁cases ▁of ▁an ▁aircraft ▁m ish ap ▁from ▁this ▁form ▁of ▁spatial ▁dis orientation ▁was ▁the ▁crash ▁that ▁killed ▁John ▁F . ▁Kennedy ▁Jr . ▁over ▁Mar tha ' s ▁V ine yard ▁in ▁ 1 9 9 9 . ▁ ▁Cor i olis ▁ill usion ▁ ▁This ▁involves ▁the ▁simultane ous ▁stim ulation ▁of ▁two ▁sem ic irc ular ▁can als ▁and ▁is ▁associated ▁with ▁a ▁sudden ▁til ting ▁( forward ▁or ▁backwards ) ▁of ▁the ▁pilot ' s ▁head ▁while ▁the ▁aircraft ▁is ▁turning . ▁This ▁can ▁occur ▁when ▁til ting ▁the ▁head ▁down ▁( to ▁look ▁at ▁an ▁approach ▁chart ▁or ▁to ▁write ▁on ▁the ▁kne e ▁pad ), ▁up ▁( to ▁look ▁at ▁an ▁overhead ▁instrument ▁or ▁switch ), ▁or ▁side ways . ▁This ▁can ▁produce ▁an ▁over power ing ▁sens ation ▁that ▁the ▁aircraft ▁is ▁rolling , ▁pitch ing , ▁and ▁y aw ing ▁all ▁at ▁the ▁same ▁time , ▁which ▁can ▁be ▁compared ▁with ▁the ▁sens ation ▁of ▁rolling ▁down ▁a ▁hill side . ▁This ▁ill usion ▁can ▁make ▁the ▁pilot ▁quickly ▁become ▁dis orient ed ▁and ▁lose ▁control ▁of ▁the ▁aircraft . ▁ ▁V est ib ular / som at og rav ic ▁▁ ▁Som at og rav ic ▁ill us ions ▁are ▁caused ▁by ▁linear ▁acceler ations . ▁These ▁ill us ions ▁involving ▁the ▁u tr icle ▁and ▁the ▁s acc ule ▁of ▁the