▁by ▁the ▁I LS ▁components ▁or ▁n ava ids ▁and ▁the ▁pres cribed ▁minimum ▁visibility ▁requirements . ▁ ▁Radio - navigation ▁a ids ▁must ▁provide ▁a ▁certain ▁accuracy ▁( set ▁by ▁international ▁standards ▁of ▁CA ST / IC A O ); ▁to ▁ensure ▁this ▁is ▁the ▁case , ▁flight ▁ins pection ▁organizations ▁period ically ▁check ▁critical ▁parameters ▁with ▁properly ▁equ ipped ▁aircraft ▁to ▁cal ibr ate ▁and ▁cert ify ▁I LS ▁precision . ▁ ▁An ▁aircraft ▁approaching ▁a ▁run way ▁is ▁gu ided ▁by ▁the ▁I LS ▁rece ivers ▁in ▁the ▁aircraft ▁by ▁performing ▁mod ulation ▁depth ▁compar isons . ▁Many ▁aircraft ▁can ▁route ▁signals ▁into ▁the ▁aut op il ot ▁to ▁fly ▁the ▁approach ▁automatically . ▁An ▁I LS ▁consists ▁of ▁two ▁independent ▁sub - system s . ▁The ▁local izer ▁provides ▁later al ▁guidance ; ▁the ▁gli de ▁slope ▁provides ▁vertical ▁guidance . ▁ ▁Local izer ▁▁ ▁A ▁local izer ▁( LOC , ▁or ▁LL Z ▁until ▁I CA O ▁standard isation ) ▁is ▁an ▁anten na ▁array ▁normally ▁located ▁beyond ▁the ▁departure ▁end ▁of ▁the ▁run way ▁and ▁generally ▁consists ▁of ▁several ▁pairs ▁of ▁direction al ▁anten nas . ▁▁ ▁The ▁local izer ▁will ▁allow ▁the ▁aircraft ▁to ▁turn ▁and ▁match ▁the ▁aircraft ▁with ▁the ▁run way . ▁After ▁that , ▁the ▁pil ots ▁will ▁activ ate ▁approach ▁phase ▁( APP ). ▁ ▁G lide ▁slope ▁( G / S ) ▁ ▁The ▁pilot ▁controls ▁the ▁aircraft ▁so ▁that ▁the ▁gli de ▁slope ▁indicator ▁remains ▁centered ▁on ▁the ▁display ▁to