The effect of staggering a biplane

The effect of staggering a biplane

(Parte 1 de 2)

No. 70.

F. H. Norton. “

Langley Memcrial Aeronauticel La?aoratory, Natiqnal Advisory Committee for Aeronautics,

Langley Field} Va.

TECHNICAL NOTE No. 70.

THE EFFECT OF STAGCXRING A BIPLANE. By

F. E. Norton.

Summary. - This investigationwas carried out by request Of .

the United States Air Service at the Massachusetts Institute ofTechnology wind tunnel in 1918. As the data collected may be of general interest, they are published here b$ the Nations3 Advisory committee for Aeronmtics. The lift, drag, and center of pressure travel are determined for a biplsne with a stagger varying frcm +’100$$to -100$. It is found that the lift incre~e with Eositive stagger. ttiecenter of pressure is far forward with changes in lift coefficient.

efficiency and the maximum With large positive staggers and has a very slight travel

Introduction. - As staggered biplanes have certain advantages from the .

cGmplete had been care was nations, The point of.view of visibility, it was thought that a more investigation of the aeraiynamic effects of stagger than done ‘oeforewould be of considerable value. Particular taken to examine the pitching moments of the various com3i- as they showed very interesting characteristics. references to work already done on stsgger are given below:

Some Stable Biplane Combinations, J. C. Hunsaker; British Advisory Committee R. & M. No. 186;

Nouvelles Recherches sur la Resistance de llAir et lfAviatioq Eiffel.

Methods. - The wings used in this investigationwere an &luminum U.S.A.15 section a6 an upper wing, and an R.A.F.15 section as the lower. Identical seotions were not employed, as none were available, but the two sections used had very similaz properties, snd previgus tests have shown that the individualproperties of the wings have little influence on the biplane characters tics. When comparing the biplane with the monoplane the aversge of the two wings was taken as the monoplane value. The characteristics of . these wings axe shown in Fig. 1.

The wings (311x 18U) were suppozted at the lower end by a streamlined‘crossbar which was attached to.the N.P.L. balance I spindle. The upper ends of the wing were connected by a very light strut whose resistance was carefully determined for each case. The gap chord ratio was one in all cases. The speed of test was

13.4 K.p.s. (30m.p.h.). Preoision. - The wings were lined up in each case to 0.05°.

In every case three separate runs were made, resetting the wings each time. In nearly every case the reading checked within 1$, soI that the average nay be considered correct to better than this .

amount, It was necessary to obtain this rather hfgh precision as the differences between different cases were generally small.

Results. - It was thought most convenient to plot CL, CD,*

L/l)and C.P. . against stagger for each angle of attack (Figs. 2, 3,“

4, 5)* The effect of stagger is clearly shown by these curves and needs no discussion. For the use of the designer, correction fac-* CL= Lift, L; absolute coefficient~~ ~=+pf; s qs = area

I D v= True air speed

iors to c’hangemonoplane values to those of a st~”gere~ biplane, are given in Table 1. Table 1.

Corrections for Stsggex.

(Monoplanevsltiesto be multiplied by these factors) Gap/ohord ratio is ~s.

Lift Corrections.

WQ.fl i.75

+i2%

i.25 1.0 i.o .95 i-25$ Q

L/D Corrections.

o-m 0.80:.

o-w 0.72

O*72 1*5O

Conclusions. - This test shows that it is advisable from the pcint of view of aerodynamic efficiency to use the highest possible degree of stagger. Moreover, a positive stagger greatly restriots the center of pressure travel> thus simplifying the problem ofstability.

+J~2 x jool d

Fig. 1 .- ~gle Wing Chord to Wind.

:+E)l .

c!? i I

\ Ib t

Percent stagger

Fig. 2- s~~ger ted CL VS. S~Sg~er.

i I I Il;l\l ‘“L—

q== =-~

I 10G I I

A l! GO I 1.n,IJ ‘-—7P-T0‘.._-.——-+.—-l1“f
“::‘J _.fi_l-;

+lWU +5(J (1 50 -100 Percent Stagger

Fig. 3 Stagger Test CD Vs* St~ger.

1 iO

“—~–––-l 6/

$ t’

I I I Iu -i+ i i i 1 ‘tL I I I I

(Parte 1 de 2)

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