, ▁assist ed ▁by ▁flying ▁w ires ▁and ▁carry ▁full - span ▁a iler ons ▁only ▁on ▁the ▁lower ▁wing . ▁There ▁is ▁a ▁small ▁trailing ▁edge ▁cut - out ▁over ▁the ▁co ck pit ▁to ▁improve ▁the ▁up ward ▁view . ▁Its ▁fus el age ▁has ▁a ▁square ▁section , ▁with ▁raised ▁deck ing ▁behind ▁the ▁co ck pit . ▁The ▁Th ul in ▁A ▁rot ary ▁engine ▁has ▁the ▁usual ▁incomplete ▁cow ling ▁associated ▁with ▁this ▁engine ▁type , ▁intended ▁to ▁restrict ▁oil - sp ray . ▁The ▁T um mel isa ▁has ▁main w he els ▁on ▁a ▁fixed , ▁single ▁ax le ▁under car riage , ▁mounted ▁via ▁fa ired ▁V - str uts ▁to ▁the ▁lower ▁fus el age ▁longer ons , ▁assist ed ▁by ▁a ▁tail sk id ▁and ▁under wing ▁wire ▁loops . ▁The ▁broad ▁ch ord ▁tail ▁surfaces ▁have ▁cur ved ▁leading ▁edges , ▁with ▁the ▁tail plane ▁mounted ▁on ▁top ▁of ▁the ▁fus el age . ▁ ▁The ▁T um mel isa ▁fle w ▁for ▁the ▁first ▁time ▁in ▁June ▁ 1 9 2 0 , ▁with ▁von ▁Por at ▁at ▁the ▁controls . ▁There ▁were ▁few ▁problems . ▁ ▁Oper ational ▁history ▁▁ 2 8 ▁T um mel is as ▁were ▁built ▁as ▁advanced ▁train ers . ▁Once ▁the ▁gy ro scop ic ▁effects ▁of ▁the ▁rot ary ▁engine ▁were ▁master ed , ▁it ▁was ▁a ▁" del ight ful ▁aircraft ▁to ▁fly ". ▁They ▁remained ▁in ▁service ▁with ▁the ▁Swedish ▁Air ▁Force