▁structure . ▁ ▁Fl ight ▁control ▁The ▁effect iveness ▁of ▁a ▁flight ▁control ▁such ▁as ▁an ▁a iler on ▁depends ▁mainly ▁on ▁its ▁area ▁and ▁its ▁distance ▁from ▁the ▁centre ▁of ▁the ▁aircraft ▁- ▁its ▁lever ▁arm . ▁If ▁the ▁wings pan ▁is ▁double d , ▁the ▁area ▁increases ▁four fold ▁and ▁the ▁lever ▁arm ▁doubles , ▁making ▁the ▁a iler on ▁ 8 ▁times ▁more ▁effective . ▁ ▁With ▁the ▁aircraft ▁being ▁also ▁four ▁times ▁heav ier , ▁and ▁with ▁the ▁weight ▁on ▁average ▁twice ▁as ▁far ▁out , ▁it ▁requires ▁ 8 ▁times ▁the ▁effort ▁to ▁achieve ▁the ▁same ▁acceleration ▁of ▁the ▁wing ▁tip . ▁ ▁These ▁balance ▁out , ▁so ▁on ▁a ▁large ▁aircraft ▁the ▁equivalent ▁a iler on ▁will ▁acceler ate ▁the ▁wing ▁tip ▁up ▁or ▁down ▁at ▁the ▁same ▁speed ▁as ▁a ▁smaller ▁aircraft . ▁But ▁on ▁a ▁wing ▁twice ▁the ▁span , ▁the ▁tip ▁must ▁travel ▁twice ▁as ▁far ▁to ▁achieve ▁the ▁same ▁change ▁in ▁aircraft ▁attitude . ▁This ▁takes ▁longer , ▁so ▁a ▁large ▁aircraft ▁man oe uv res ▁more ▁slowly ▁than ▁the ▁equivalent ▁smaller ▁aircraft . ▁ ▁On ▁very ▁large ▁types ▁such ▁as ▁the ▁Air bus ▁A 3 8 0 , ▁conventional ▁a iler ons ▁alone ▁are ▁not ▁enough , ▁and ▁additional ▁lift ▁spo ilers ▁are ▁used ▁to ▁reduce ▁the ▁lift ▁of ▁the ▁down ward - ti pping ▁wing ▁and ▁increase ▁the ▁roll ▁rate ▁to ▁a ▁practical ▁and ▁safe ▁level . ▁ ▁Similar ▁issues ▁occur ▁with ▁the ▁elev ator ▁and ▁pitch ▁control . ▁ ▁Without