Aerodynamic tests of an NACA 66(215)-116, a=0.6 airfoil with a 0.25c slotted flap for the Fleetwings XA-39 airplane

Tests were cor ducted in tr.!.e Langley fwo -dime nsional low-turoulence tu..'Y1l1els on a r21j.-inch-ch o::>d mode l of the N4CA 66 (2 1 5 ) -11 6 , a = 0. 6 air f oil wi t h a 0 .25 -chord slo t ted flap .It wa s c e s ired to 0'0 tain opt imum f lap pi vot posi ti O;l S fo :::, the f'cllowing c on di tions : ( a) a hi gh• maximum lift coeffi.c ient [i.t a l-'J.gl flap d eflection; (b) high lift eoe f / 1 ciants vi th re a ' onabl,T lo,v drags at a i'lap de flect :!on of 30 0 ; and (c) a -r ositive lift coeff ici en t 'Nith l ow d rags at a :;'le s ative [;.ngle of attack for a flap defl ecti.on of 15 0 • The~e COl1(Uti ons were de t ermin ed from a consi de r a t ion of the l andinu , take-off , and strafi ng l'eqlJire ent s of t )_:.e a irplane .Two slot entr ~ l ip s were tested to find the effect of a door which cl osed the s lot on t he 10\'.'ersurface when the f lap was retracted .Flap l oad s were ob tained a t cert ai n configura tions a nd the eff e cts of e xte ~nal fl ap h inge s and of t h e r emoval of t he i n tern al slot fairing skin were inve sti gated .The results showed t ha t no single pi vot po si tion was the optimwn for a ll of the spec i fied conjitions .Covering the sl o t "'0y a door on tr!e J. n•ver surface was foun d to cause 10 er d r ags at sn: ..all flap d eflections than le aving the sl ot open.One f l ar hino e wa s found to c ontrib ute a n a del i t ional drag c oe ff ici ent o:f 0 .0 0 02 with t he f lap re trac t ed , based on an a r ea eq .1al to the chord squa red .The r em.o va l of the interior slot fairing s kin was s hown to ha ve little or no ad ver~e effect .