W ) ▁V - tw elve ▁water - co o led ▁ ▁Curt iss ▁D - 1 2 . ▁Both ▁were ▁en closed ▁by ▁a ▁metal ▁cow lings , ▁though ▁of ▁slightly ▁different ▁shapes , ▁and ▁drove ▁a ▁two ▁bla de ▁prop eller . ▁ ▁The ▁single , ▁open ▁co ck pit ▁was ▁well ▁to ▁the ▁rear , ▁about ▁mid way ▁down ▁the ▁fus el age . ▁ ▁Its ▁horizontal ▁tail ▁was ▁b rac ed ▁and ▁the ▁fin ▁was ▁small , ▁carrying ▁a ▁bal anced ▁rud der ▁that ▁extended ▁down ▁to ▁the ▁ke el . ▁ ▁The ▁D . X II ▁had ▁a ▁fixed ▁conventional ▁under car riage ▁of ▁the ▁single ▁ax le ▁type , ▁supported ▁by ▁V ▁str uts . ▁ ▁There ▁was ▁a ▁small ▁tail ▁sk id . ▁ ▁The ▁first ▁flight ▁under ▁Curt iss ▁power ▁was ▁made ▁on ▁ 2 1 ▁August ▁ 1 9 2 4 . ▁Fl ight ▁testing ▁followed , ▁resulting ▁in ▁major ▁modifications . ▁ ▁The ▁upper ▁wing ▁was ▁given ▁an ▁uns we pt ▁leading ▁edge ▁and ▁hence ▁had ▁constant ▁ch ord ▁and ▁the ▁small ▁lower ▁wing ▁was ▁replaced ▁by ▁one ▁with ▁the ▁same ▁ch ord ▁as ▁the ▁upper ▁plane ▁and ▁a ▁span ▁almost ▁its ▁equal , ▁mounted ▁with ▁marked ▁st agger . ▁No ▁longer ▁a ▁ses qui plane , ▁the ▁s play ed ▁V ▁inter plane ▁str uts ▁were ▁replaced ▁with ▁more ▁rig id ▁N - form ▁ones . ▁Another ▁b rac ing ▁str ut ▁ran ▁from ▁the ▁forward ▁foot ▁of ▁the ▁inter plane ▁str