▁that ▁the ▁nose ▁of ▁the ▁aircraft ▁is ▁pitch ing ▁down . ▁The ▁pilot ' s ▁response ▁to ▁this ▁ill usion ▁would ▁be ▁to ▁pitch ▁the ▁nose ▁of ▁the ▁aircraft ▁up . ▁If ▁this ▁ill usion ▁occurs ▁during ▁a ▁low - speed ▁final ▁approach , ▁the ▁pilot ▁could ▁st all ▁the ▁aircraft . ▁ ▁Visual ▁▁ ▁Visual ▁ill us ions ▁are ▁familiar ▁to ▁most ▁of ▁us . ▁Even ▁under ▁conditions ▁of ▁good ▁visibility , ▁one ▁can ▁experience ▁visual ▁ill us ions . ▁ ▁Linear ▁perspective ▁▁ ▁This ▁ill usion ▁may ▁make ▁a ▁pilot ▁change ▁( in cre ase ▁or ▁decrease ) ▁the ▁slope ▁of ▁their ▁final ▁approach . ▁They ▁are ▁caused ▁by ▁run ways ▁with ▁different ▁width s , ▁ups lop ing ▁or ▁down s lop ing ▁run ways , ▁and ▁ups lop ing ▁or ▁down s lop ing ▁final ▁approach ▁terrain . ▁Pil ots ▁learn ▁to ▁recognize ▁a ▁normal ▁final ▁approach ▁by ▁developing ▁and ▁recall ing ▁a ▁mental ▁image ▁of ▁the ▁expected ▁relationship ▁between ▁the ▁length ▁and ▁the ▁width ▁of ▁an ▁average ▁run way . ▁An ▁example ▁would ▁be ▁a ▁pilot ▁used ▁to ▁small ▁general ▁av iation ▁fields ▁visit ing ▁a ▁large ▁international ▁air port . ▁The ▁much ▁wider ▁run way ▁would ▁give ▁the ▁pilot ▁the ▁mental ▁picture ▁of ▁the ▁point ▁where ▁they ▁would ▁usually ▁begin ▁the ▁f lare , ▁when ▁they ▁are ▁much ▁higher ▁than ▁they ▁should ▁be . ▁A ▁pilot ▁flying ▁an ▁aircraft ▁where ▁the ▁co ck pit ▁height ▁relative ▁to ▁the ▁ground ▁is ▁vast ly ▁higher ▁or ▁lower ▁than ▁they