NACA TM 353 Recent Experiments With Large Sea Planes

7/27/2019 NACA TM 353 Recent Experiments With Large Sea Planes

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' ' . IJANONAL_ ADTISOIIY COMMITTEZ FOR AERONAUT ICS

TECWI CAL MEMORANDUM NO. 353.-:RECENT EXPERIDNTS WITH L4RGE SEI1PLANES.

*

By Adolf Rohrbach.

Two y e a r s ag o I had t h e p r i v i l e g e of a d d r e s s i n g you i r ,

Bremen on t h e ad va nt ag es of l a r g e a i r p l a n e s w i t h a heavy wing-

load . I a m g r a t e f u l t o t h e "'Vissenscha f t l i c h e Ges e l l s c h a f t

f & r L u f t f a h r t t l f o r g i v i n g me t h e o p p o r t u n i t y t o t e l l you t od aywhat has been accompl ished s i nc e t h e Eremen mee t ing , i n bo tk my

companies , w i th t h e cooper a t ion o f my. apab l e coworkers, i n

o r d e r t o d em on st ra te p r a c t i c a l l y t h e c o r r e c t n e s s of my v ie ws,

on i n c r e a s i n g t h e s i z e of a i r p l a n e s , by t h e c o n s t r u c t i o n of

o t h e r l a r g e a i r p l a n es , a f t e r t h e 1000 EP. monoplane of the

"Zeppel inwerke Staakenl1 ( t h e only exponent a t t h a t time of the

p r i n c i p l e of heavy wing loa d in g) had no t been a l lowed by th e

I n t e r a l l i e d Contro l Corxmission" t o comple te i t s t e s t s .

1. Ad v a n t a ~ e s f he av y win s l oa d. - Re f e r r i n g t o t h e

Bzemen lecture, I would l i k e t o remind you, th rough t h i s dia -

gram ( F i g . l ) of t h e p r i n c i p a l a d va nt ag es of l a r g e a i r p l a n e s

wi th heavy wing load i ng . Th i s d iagram shows, f o r l a r g e a i r -

p la nes of th e 018 tl-pe ( i n which t h e wi ng l o a d p e r u n i t area

i s the same a s . f o r s:mll a i r p l a n e s ) how t h e pay l o a d i n c r e a s e s

w i t h t h e s i z e of t h e a i r p l a n e o nl y up t o a t o t a l w ei gh t of-*

From "gericht e und A'ohandlurlgen d e r W i ssensc 'ha f t l i chen Gese l l -

s c h a f t f u r Luf f a n r t , t J u l y, 1925.


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N 4 d i C . A . . Technical Memoxndum No. 353 2

about 9000 kg (19,842 lb..)* and how i t f a l l s o f f beyond t h i st

p o i n t w i th c o n s t a n t ly i n c r e a s i n g r a p i d i t y. The c a s e i s d i f f e r -

e n t f o r l a r g e a i r p l a n e s i n which t h e s p e c i f i c wing l oa d in-

c r e a s e s wi th t h e s i z e of t h e a i r p l a n e a c co r di ng t o t h e l a w of

s i m i l i t u d e of n a v a l a r c h i t e c t u r e . A s a r e s u l t of t h e g r e a t ro-

duc t i on thus p roduced in t h e ex t e rn a l d imens ions of t h e a i r -

p lan e , t he r e l a t i v e weigh t of t h e wings i nc r eas es much s lower,

w i t h t h e i n c r e a s i n g s i z e of t h e a i r p l a n e , and t h e pay l o ad

consequent ly reaches i t s maximum v a l u e c t a f u l l l o ad of a b ou t

16 ,000 k g ( 3 5 , 2 7 4 l b . ) . The s pe ed of l a r g e a i r p l a n e s w i t h

l i g h t e r wing ioad ing i s n o t g r e a t e r t h a n t h e 'spee d of co r re -

spond ing s r' ra ll er a i rp l a ne s bu t , on th e con t ra r y, a s shown by

t h e d ia gr am , t h e sp ee d of t h e l a r g e a i r p l a n e s , h a v i n g a heavy

s p e c i f i c wing l oa d , i n c r e a s es c o n s i d e r a b l y w i t h t h e s i z e of

t h e a i r p l a n e .

I n o-icr f l i g h t t e s t s w it h % h e f i ~ s t i r p l a n e , w e a , t t a i n e d s

rnin,g lo ad of 88 kg/m2 (18.02 l b . / s q . f t . ) . I n t h e s e t e s t s t h e .

D . V . L. ( ~ e u t s c h e e r s u ch sa n st a l t f c r ~ u f t f a h r t ) ound. our '

mean f l i g h t s pe ed w i th f u l l l o a d t o b e ab ou t 1 7 4 km ( 10 8 m il e s )

per hou r. T h e p r o p e l l e r e f f i c i e n c yt v 8 s

only about 56$.' D r .

Koppe w i l l e x p l a i n i n h i s l e c t u r e * * how t h e p r o p e l l e r e f f i c i e n c y

w a s detercqineC! from ob se rv +t io ns made du r i n g f l i g h t .

I w i l l jmprove t h i s o p p o r t un i t y t o s p e a k ' b r i e f l y of t h e

* On th e assumpt ions p ubl i s hed i n I18eihcf t 1011 of t h e I fZei t -s c h r i f t ffir F l u g te ch n ik und . M o t o r l u f t s c h i f f a h r t , 1923.* * Hein rich Koppe, f l llessungen a n Luf tfa hrf eug en, " . Jah rbuch derW;G - L . ( Wi s s e n s ch a f t l i c he n G e s e l l s c h a f t f u r L u f t f ah r t ; " ) 1 92 4,pp. 38-47. Al so N . k . C . 11. Technical Memorandum No. 3 5 5 .


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N - i ' . C - A - T.echnica1 Km3rzndum 'No. 353 4

-American experiments, could be expec ted to g ive a lmos t i de n t i c a l

r e s u l t s , a c t u a l l y gave e x t r e m e l y d i f f e r e n t r e s u l t s . We l o s t

much time mith th cs c pr op el lt or problems. Nowwe

a r e a g ai n mak-ing o ur p r o p e l l e r s a c c or d in g t o s u c c e s s f u l l y a 3 p l i e d p r a c t i c a l

formulas . hop ed , however, t h a t t h e In-

s t i t u t e w i l l soon be equipped so that t h e r e s u l t s . of p r o p e l l e r

expe r imen ts , inc lud ing th e re ac t ion be tween t h e p r op e l l e r and

a i rp lane on the mode l , w i l l a g re e v i t h t h e r e a l i t y , even i n

f l i g h t , a s we ll as t h e s t a t i o n a r y t e s t s made a t o ur r e q u es t ,

w i t h f u l l - s i z e d p r o p e l l e r s , b:$>+ t h e D . V . L . a t A d le rs ho f..

1

The heavy wing loading, $ s. . shown by Fig. 2 , a f f o r d s t h e

fu r the r advan tage o f a c o n s i d e $ q b l y b e t t e r t u r n i n g a b i l i t y.I

The t ime requ i red f o r f l y in g *hhsough a complete c i r c l e wi th a

l i g h t wing l o a d i n g i n c r e a s e s r a p id l y w i t h t h e s i z e of t h e a i r -

p lane , whi le i t o nl y i n c r ea s e s ve r y s l ow ly f o r l a rg e a i r p l a n e s

wi th a heavy wing loading. The time re quir ed t o f l y through

given curve o f t en dec i s ive , e s p e c i a l l y i n a e r i a l f i g h t i n g .

Thc t u r ni n g a b i l i t y of a n a i r p l a n e is sa t i s fac to ry, however,

only when i t can quickly assume, any curve an d ' can then f l y

q u i c k l y through that curve . t h e a b i l i t y f l y qu ick ly

through the curve had been a s s u re d b y the heavy wing loading,d

I f i r s t employed th e excep t ion a l ly l a r ge d ihe dra l ang le of 6O,

a s shovm i n Fig . 3 . Th i s l a r g e d i h c d ra l seemed a t f i r s t some-

what hazardous s i nc e a l l th e more recen t a i r p l an es had e i t he r

v e ry s m l l d i h e d r a l s o r none a t a l l . The d i h e d r a l i s v e ry


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N . A . C . A . Technical Uerr,o'r~nd-dm No- '353

.. . . ..F . 1 L . 1 X ' C & 2 , i l ~ 'Lab S ~ , - i . i - i. -o s i r a b i c oil s ~ ~ ~ p l s n ~ s ,o;~evc;r, I ' ~ I S - b ' '

? s - s , bcccuse i . t m . i s e s t h e wing t i p s h i g h e r a bo ve t h e v f a te r

an d a l so . f o r an t i c i pa t e d improvement i n maneuverab i l i t y . I t i s

iino.;~n t ? x b t an e i r p i a n c s t e e r s ~ c l l n t h e l o n g i t u d i n a l d ir e c -

t i o n , on ly when i t s l on g i tu d i n a l s t a b i l i t y o r i n s t a b i l i t y i s

s l i g h t The narr,c p r i n c i p l e a p p l i c s t o banking a b i l i t y , i. e . ,

b h c 1 a t er a . l s t a b i l i t y o r i n s t a b i l i t y must b e nade c s small a s

p o s s i b l e c.nd t h e s im p l e s t n ay t o a c c om p li sh t h i s r e s u l t i s t o

s i v e t h e v ~i ng s a l a r g e d i h e d m l a ng le . I n o r d e r t o r e d u c e

t h c r i s k a s m c h n s p o s s ib l e , a very compre3nnsivc mathemtic-

a 1 i n v e s t i g a t i o n m s undertaken b y h f r. Brandt under t h e super-

v i s i o n of p r o f e s s o r F uc hs. The p u rp o se of t h i s i n v e s t i g a t i o n

was t o de te r mi n e hor: t!e m otio n of t h e a i r p l a n e i s a f f e c t ed 'oy

i n c r e a s i n g t h e d .i he br al a n g l e .

\

A ? ;enera1 s o lu t i o n of t h e p roblem i s v ery d i f f i c u l t , s i n c e

t h e f u n c t i o n s u n de r c o n s i d e r a t i o n m e ve ry compl i ca t cd and not

e ~ ~ l i c i t 7 . ~iv en , some of them neve r having been thoroughly

i n v e s t i e t c d . T h c s o l u t i o n i s given h erc i n a s i m p l i f i e d f o r m ,

a s 3 s t a b i l i t y i n v e s t ig a t i on b y t h e met306 of sma l l o sc i l l a -

t i o n s , t h e t r a i n of th ou gh t b e i n g a s f ol lo w s:F i r s t , t h e g e n e r a l . motion e q ua ti o ns of t h e a i r p l a n e a r e

s e t down. These a r c s i m p l i f i e d i n s o f a r as o n l y small dcvia-

t i o n s from s t a t i o n a r y f l i g h t and a l s o frorn r e c t i l i n e a r f l i g h t

a r e i n v e s t i p p t d . The mot io n ' eq ua t ion s a r e develo pcd a cco rd in g

t o t h c small de v ia t io ns and o n17 se in ?~ c r s f t he f i r s t o rd er a r e


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N . A. C ,A . Technical 3.demorsndum No. 353. 6

c o n si d e r& . Then t h e d i f f e r e n t i z l e q u at i on s a r e i n t c g r a t c d on

t h e assuvnpticn of def i r i i t e rudder d e ~ l ' e c i on s a n d d e f i n i t e iili-

t i a l c c n d i t i o n s . Thus t 3 e cour se of t h e a i r p ln n e m t i o n i s ob-

t a i n e d wid er t h e i n f l u e n c e o f t h e r u d de r d e f l e c t i o n s and i nd e ed

of t h c l a t e r a l angle, l a t e r a l i n c l i n a t i o n. . e cd a n g u l a r v e l o c i t y. .

z b o ~ t i& v e r t i c a l a x i s , a s a f u n c t i o n of t h e t i me. Th i s sns

accomplished w i t h t h e Fuchs-Hopf fo;&lao .. ( ~ u c h s - ~ o ~ fAerody-. .

. . .

. .-na.mik,I1 p. 403 f f ) , a s f ~ l l o m s . . .

The mo t i o l i c q u s t i o n s y i e l d t h e .. power equa t ions ( F i g . 4) ;. .

x = a x i s : G d ' i~F d t - - G s i n ~ + S O P T c o s a - c W q F (1)3 , . . . .. .

(ay s i n p -, = a x i s : 0 = - v " dt; C O S p -g /

- G coscp c o s p + S C O G T s i n s + c a q F

Z, = a x i s : 0 = G v ( a y c o s p + 9- i n p \ +Q a t 1

+ G c o s B s i n p - S s i n s - C Q q F4

Further f o r t h e moncnt equa t ions :

I n t h e s e eq-clat io ns :

G = f u l l load i n kg ,

. g = g r a vi t y . a c c e l e ra t i o n i n n / s 2 ,


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.. .. .. --. ., -. _ .

' - - .

. N.,A-C&-+ T.ecwica1 ~ ~ s m ~ r s n d w pJ.0. 3 5 3 .. 8

.

system of coordinztes

F or t h e a i r p l a n e - f ixed System o f coo rd ina te s , r e o b t a i n

d(3d t 1x = [(uCosq co6p + - i n p

. s i n a +1

+ j w s i n 9 + $$) oos 4 os r - [o cos cp s i n p +\ \..

. ~.

dad:!+ @ Cos p + 4 i n rd t . di$ (10)

u y = ( W C O S q~ cos jl + s i n p \ c o s a -,- d t 1

= (iW 0 s C O G p + s i n P \ s i n CL +d t 1dlJ' cos a] s i n 7 +i n cp + -t l

dVI o c o s q s i n p + - - c o s p + 3 ) O S TL d t

With respec t t o o nl y s t c a d y x o t i o n an d on ly s l i g h t d ev ia -

t i o n s from r e c t i l i n e a r f l i g h t ? e qm t i o ns . ( 1 0 ) t o ( 1 2 ) become

uX = w s i n (vo + uo) + c06 .ao (13)


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N . A . C.A. Te c h n i c a l Z e ~ o r a n ~ u m i o. 353

i n w hich vo , a. and qo a r e s t e a d y - f l i g h t v a l ue s .

A f t c r e q ua ti on s ( 1 ) t o ( 6) have been , t r e a t ed . in th e scme

way, i . e . , i f only stozdy mot.ion. . and small d e v i a t i o n s - from r e c t i -. .

l i n e a r f l i g h t ar e c on si de re d, . t h e f i r s t s y st em of e q u a t i o n s ( 1 )

t o ( 6 ) b r e a k s up i n t o two groups of t h r e e equ at i on s each, one

group represent ing t h e l o n g i ~ u d i m l nd t h e o t h e r t h e l a t e r a l

motion. The t h r e e l a t t e r e qu at io ns r ea d , a f t e r t h e a i r f o r c e s

have 2 l s o b ee n d e ve lo pe d a c c' or d in g t o t h e v a r i a b l e s


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Ii. A . C.2. Technical Ifernorandurn 140. ., 353

+ '5 co s ( q - + a) & + c i 5 S" c o s o +y .. dt F b 2

in which

S = p r o p e l l e r 5 h r u s t i n kg,

q = dynamic p r e s s u r e in kg/m2,

F = .wing a r e a in m2,


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c; = d e d uc t i on of n or ma l p o s e r c o e f f i c i e n t on t h e v e r t i c a lt a i l p l an e s a c c o r di n g t o t h e a n g l e of a t t a c k (non-

d imens i o n a ~ )Fs = a r e a of v e r t i c a l t a i l p l a n e s i n m 2 ,

@'= ded uct ion of harmful area o f a i r p l a n e ( w i t h o u t - i v i n g sand t a i l , i n a l a t e r a l wind a cc o rd i ng t o t h ea n g l e of a t t a c k ) i n I$,

s = l e n g t h ' of t a i l i n m,

b = span of wing i n m,

a = a n g l e of a t t a c k of wing i n d e g r e e s ,

h = h e i g h t of v e r t i c n l t a i l p l a n e s ab ov e c e n t e r o f g r a v i t yi n , m,

Gv2G =-

weight , as non-.dimensional factor,gqFb

q~ = a n g l e of f l i g h t p a t h i n d eg re es ,

v = d i h e d r a l a n g l e i n d e gr ee s ,-t = = time, as a non-dimensional var iable ,

b t

-o = = t u r n i n g s p ee d , as a non-dimensional (var iable ,v

p = l a t e r a l i n c l i n a t i on i n deg rees ,

T =. d i r e c t i o n of l a t e r a l wind i n d eg re es ,

2, = rud de r moment (non -di men sio nal ) ,

k, = banking moment ( non-dimensional) .-, = Gn u x]

b2 7 non-dimens io n al i n e r t i a moments, i n- x h i c h k = r a d i u s of i n e r t i a .J y =. Gn

The g e n er a l s o l u t i o n o f t h e e q a t i o n s r ea ds :


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R A . 2 - A . Techn ica l Yenoranc lu~ No. 353

The exponexts h a r e d e te r mi n ed f ro m ' a n e q u a t i o n o f . t h e

f o u r t h de g r ee , which i s d e r i v e d fr om e q u a t i o n s ( 1 6 ) t o ( 1 8 ) . .

Th e d e t e r m i n a t i on of t h e v a l u e s of 7 , U and p y i e l d s t h e fo l -. .

lowing c u m e f o r t h e h o r i zo n t a l f l i g h t 0 % t h e a i r p l a n e t yp e

Ro I1 a t a n a l t i t u d e. of 2000 m


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N . A . 2 . A . 'Technical Xemorandum No. 353

These. r e l a t i v e l y s i q l e e q ua ti on s c an b e recommended f o r a l l

a i r p l a n e s of s i m i l a r d e s i g n .

The fo l lowing i s a. d i s c u s s i o n of e q u a t i o n s ( 2 2 ) an d ( 2 3 )

w i t h o u t t a k i n g t h e i n i t i a l c o n di t i o ns i n t o c o n si d e ra t o n.

,I

2 gc4 'i +p = ,- 6 * b \ l - veil I

f? b cn

Eerey = l a t e r a l i n c l i n a t i o n i n d eg re e s ,

v = v e l o c i t y i n , m / s ,

g = gr av i t y acce1erht ;io.n i n rn/s2,

b =. wing span in m y. ..L, = a il 'eron moment, ilondime~isional th rough d i v i s i o n b y

wing area and wing chord,


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. '.

N . A . g , A . Te ' i i n i c a l Merorandum No- 353 .I5

t u r n i n g a b i l i t y . w i t h r ef e r e ~ c e t o i t s l o n g i t u d i n a l a x i s .

w i s t h e t u r n i n g speed, i n de gr ee s, a bo ut t h e - ~ e r t i c a l x i s of

t h e a i r p l a n e .

Tne same p r i n c i p l e which ho lds good f o r o i n comparing

t h e two members, a l s o ap p l i es he re f o r a , 'out wi t h the d i f f e r -

e n c e t h a t , on account of t h e system of coo rd i nat es chosen , o

i s negat ive . But even here , w i th increas i -ng t , t h e t u r ni n g

spced becomes co ns ta nt l y more negat ' iv c znd s t i l l more s o f o r a

grea tc r 2 i ' n ed ra l a .ng le . The b r a ck e t ed q u a n t i t i e s a r e t h e same

i n e q u a t i o n s ( 2 2 ) and ( 2 3 ) , o ~ l y h e ? re ce d in g f a c t o r s d i f f e r -

ing. . These f a c t o r s show whether t h e d i he d r a l has a more favor-

a b l e e f f e c t on t & e r a p i d i n c r e a s e of t h e l a t e r a l i n c l i n a t i o n o r

o n t h e t u r n i n g s p e e d , about t h e v s r t i c a l a x i s . I n o r d e r t o s e t -

t l e t h i s p o i n t , a n e v a l u a t i o n of t h e o r d e r of m a gn it ud e of t h e

v a l u e s in equat ions ( 2 2 ) and ( 2 3 ) i s necessary..

l i e s somevili$.r,e w i t h i n t h e l i m i t s 0 and O..5, when i t i s consid-

e red tb2t on ly smal l va lues o f t a r e concerned. Hence


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l i e s somewhere wi t h i n t he l i r ~ i t a and 1 . 6 and

i s chosen a t abou t 10 .

Then t h e f i r s t e xp r es si o n i n c r e as e s from z er o t o a bo ut 0.76

and t il e second expres s ion in c r ea se s abou t t h e same, even f o r a

l a r g e d i h e d r a l . 1 n e q c a t i o n ( 2 3 ) t h e f i r s t menibcr i n c r e a s e s

a p p r o s i m t e l y f rom 0 t o 0.07 and th e second member i nc r eas es

a p p r o x i r mt e l y f rorn 0 t o 0 .1 f o r a l a r g e d ih e d r a l a n g le .

Thus i t . i s demonstra ted tha t a l a r g e r d i h e d r a l a ng le i s

esp eci2 11y f a v o r a b l e f o r t h e t u r n i n g a 5 i l i t y a bo u t t h e v e r t i c -

a l a x i s of t h e a i r p l a n e , b e c a us e i n e q u a t i o n ( 2 3 ) , t h e manbcr

w i t h v i n c r e a s e s more r a p i d l y wi t h a g r e a t e r v t k n t h e

f i r s t v;ithout v , w h i l e i n e q u a t i o n ( 2 2 ) , t h e menbers have

the same val-ue. o

The w n o l e i n v c s t i s t i o n h o l ds good o n l y f o r s ~ i a l l v , t h e

r e l a t i o n s be in g d i f f e r e n t f o r l a r g e V. An a i r p l a n e , of t n e

t ~ y p e o r which t h e i n v e s t i g a t i o n was made, i s s t a b l e l a t e r a l l y

f o r a d i h e d r a l of ab o ut 10". The c f f e c t of t h e a i l e r o n s i s

t h u s c o n s i d e r a b l y

d r a l shou.ld be avo ided .

exc ess i v 5 dine-

I n f a c t t h e z i r p l a n e 'has e x c el l en t t ur n i ng a b i l i t y , i n

agreement n i t h t h e computed r c s u l t s . 1'; i s brotlg ht v e r y e a s i l y


18/39

N . * A A C I A * Technic21 Memorandum No. 353 17

i n t o th e curve , s'irnp ly b y means of th e rudder, and- can l i k e w i s e

b e e a s i l y brought back a g a in i n t o r e c t i l i n e a r f l i g h t by t h e

s a m e means.

The Dower plant.- A compromise was ad op ted i n i n s t a l l i n g

t h e engines , wi th regar d t o good r.mneuvera.b il ity on t h e water,

on t h e one hand, and good f l y i n g wi th on ly one eng ine , on t h e

o t h e r h ~ d . he two 3011s-Royce B g l e I X e ng in es a r e t h e r e f o r e

mounted on s u p p o r t i n g f r am e s of s t r a m l i n e d s t r u t s ab ove t h e

win gs , i n o r d e r t o h av e t h e p r o p e l l e r s h i g h enough e b ov e t h e

wat er. This ar rangcxerr t has been f ou nd s a t i s f a c t o r y i n e ve ry

r e s p e c t . The l a r g e r a d i a t o r s t a n d e betw ccn t h e en g i ne a nd

p r o p e l l e r o n a p r o l . o n p t i o n of t h e e n g i c e s u p p o r t s . The radia-

t o r s c a n b e e n t i r e l y c l o s e d b y mec,ns of v e r t i c a l a d j u s t a b l e

s h u t t e r s o p e ra t e d fr om t h e p i l - o t ' s s c a t . Behind t h e e ng in e 2nd

s e p a r a t e d f r o m i t by a f i r e w al l , t h e r e i s a g r a v i t y t an k ( f o r

2 0 minutes) a ~ d n o i l t a nk s up po rt ed b y a backward extension

of t h c e n gi n e s u p p o r t s . I t vias o r i g i n a l l y p la nn ed t o p l a c e

t h e wnin f u e l t a n k s ( c s p a b 1 e of h o l di n g enough f u e l f o r 6 . 5

h ou rs v i t h t h r o t t l e w ide open) i n t h e h u l l . S i n c e t h i s a r r a n g e -

ment i s , however, p r oh ib i t ed i n Eng land , on accoun t of th e f i r e

d a n ge r, we hung t h e t a n k s f o r t h e f i r s t t e s t f l i g h t s pr ov is ion -

a l l y under t i le wings , fo l low ing the example of many Engl ish

a i r p l z f i e s . They a r e now p lace d i n th e wings , be in g g iven th e

e x ac t s b p e of t h e l a t t e r . Tkle f u e l i s forced f rom the ! ;%in


19/39

N * A * C . A . Technical Idenorandum No. 353

t a nk i n t o th e g ra v i ty t ank by means of a pump g eare d t o t h e pro-

Thc side- by-s ide errangcme nt of t h e engi nes has, f o r viat e r

maneuvers, th e adv anta ge th a t chcrt onl y one en,gine i s run, i t

i s a l ~ : a y s s u f f i c i e n t l y c oo le d 2nd t-hat, morcovor, by op er at in g

on ly one eng ine , a ver y g r ea t tu rn in g moment can b e deve lop&,

w it ho ut g i v i n g t h e a i r p l a n e so g r e a t a speed a s would bc neces-

s a r y f o r t h e o b t en t io n of a l i k e t u r ni n g a b i l i t y , i f t h e en-

ginos mere in tandem. Wi t h t h e e n g i n e s a b r, e a s t , t h e s e a p l a n e

t h e r e f o r e r e q u i r e s c o n s id e r ab l y less room f o r t u rn in g on t h e

. mater, thzn i f t h e e n gi n es n e r e i n t ar de m. Due t o t h e lower

speed, i t s h i p s much i c s s r ia ,t cr i n ~ mn cuv e r in g n n heavy sea.

bLneuvering on t h e w at er i s g r e a t l y f a c i l i t a t e d b y t h e

a d j u s t a 6 l c t a i l u n i t ( ~ i g . ) , which can b e r o t a t e d ( on tyro

b e a r i n g s ; , , i n f i v e s e co n ds , up t o o deflection of 1 2 " , by means

o f a c r an k w i t h i n r e ac h of t h e o i l o t s s e a t ) a b o u t o d u r a l u n i n

t o n e r f i r m l y s oc ur ed t o t h e r e a r end of t h e h u l l ( F i g . 7 ) .

T h i s a d j u s t a b i l i t y o f t h e t a i l u n i t was o r i g i n a l l y d o s i p e d s ix -

p l y t o o f f s e t t h e on e-side d p r ope l l e r t h r u s t , nhcn f l y i n g n i t h

on ly one cngine running, which purpose i t v e r y s u c c e s s f u l l y

se rved . A d e f l e c t i o n of o n l y a f ow d eg re es s u f f i c e s f o r rec-

t i l i n e a r f l i g h t , even n i t h th e rudder i n i t s c e n t r a l p o s i t i o n,

s o t h a t t h e seap lane , w i th on ly one onginc running , can be

b r o u g l ~ t , by a e a n s of t h e ru d d e r c l o n e , i n t o e i t h e r a r i g h t o r

l c f t c u r v e a s e a s i l y a s i n n o r m 1 f l i g h t , w it h b o th eng ines


20/39

ru nn ing , o r i n g l i d i n g f l i ~ h t .

n b i s f c c . i l i t a t i ng of t h e o pe ra t i on of t h ~ u d d e r a l s o ccm-

s i d e r a b l y i mproves t h e a c t u a l f l y i n g 2 b i l i t y n i t h one e ng in e,

s i n c e t h e r u e d e r i s so e f f e c t i v e on t k i s a i r p l a n e , . even a low.

speed, t h a t a l l g u s t s c c n S c d i r e c t l y cou nt c r a c t cd. lVl~cn, hon-

ov er, t c e r ud de r ( a s i s t h e c a se n i t h a i r p l a n e s n o t h a vi ng a n

a d j u s t a b l e t a i l u n i t ) mist b e d e f l ec t e d v er y f a r , i n or d er t o

o f f s e t t h e o ne -s id cd p u l l of t h e s i n g l e e n g i n e , i t i s g e n e r a l l y

no longer e ffec t ive enough , a t t h e l o w e s t p o s s i b l e f l i g h t s p e e d ,

t o p re ve nt e a s i l y a d e v i a t i o n of t h e a i r p l a n e from t h e d e s i r e d

c o u r s e i n g u s t y we e t h e r. The p i l o t s ho uld , th e re f or e , i n p s t y

weather, r m i n t a i n a , a t h e r h i g h sp ee d, i n o r d e r . t o makc t h e

rudder more effect ive. Th e r e s u l t i s t h a t s uc h a n a i r p l a n e

l o s e s ~ J t i t u d e ore r a p i d l y t h a n 1:fould b e n e c e ss a r y w i t h r e f e r -

ence t o t h e a c t u a l f ' l y i n g . a b i l i t y of t h e ai r pl a ne - .

The a d j u s t a b i l i t y of t h e t a i l u n i t i s , howcver, as a l r e a d y

men ti on ed , a l s o v e r y u s e f u l on t h e ma t e r. l? / i th t h e normal po s i -

t i o n of t h e r ud de r and a i l e r o n s and w it h co'm pletely t n r o t t l d

e n g in e s , t h e s e a ol a n e r un s a b o u t t vo p o i n t s (22.s0) ou t of thowind. By t h e o p e r a t i o n o f t h e r udder a n d a i l e r o n s , t h e sea-

p l a n e c a n b e t u r nc d a bo ut f o u r p o i n t s ( 4 5 O ) o u t . of t h e wind.

I f , f u r t ~ e r m o r e , h e vfnole t a i l u n i t i s s h i f t c d , t h e se a pl an e

t h m t u rn as rh-~ch as s i x p o i n t s (67.5' ) ou t of th e wind. Thus

t h e p i l o t s t i l l has a t h i s d i s p o s a l t h e t o t a l t u r n i n g moment

g en er at ed on a n e n g i ~ e y o pe ni ng 0u.t , t h e t h r o t t l e a nd c an t h e r e -


21/39

. . - . N.. A.. CS Tec.hnica1 Memorandum No. 3 53 20

' evenf o r e turn t h c s e a pl an e s e f e l y , / i n a v e r y s t r o n g w ind. Wi th a

r ~ i n d e l o c i t y o f 1 4 m ( 4 6 f t . ) p e r sscond and a t i d e o f 3 rn

-. .(n ea r l y 10 f t . ) p e r s econd , w i th ve ry sh o r t choppy waves, a l lp o s s i b l e e v o l ut i on s were w d c on t h e w at er m it ho ut t h e l a s t

d i f f i c u l t y . The s e a p l a n e t u r n e d v e r y q u i c k l y 2n d e a s i l y o u t of

t h e ' ~ i n d . The t a i l u n i t mas s h i f t e d i n a l v i ~ d f 1 5 5 ( 4 9 f t . )

p e r s econd and then , w i th on ly th e eng ine on t he w ea the r s id e

m n n i n g a t 700-800 R.?.l!., a d i s t c n c e of s e v e r a l m il es n ast a x i e d o b l i q u e l y t o t h e w i n d .

F loa ts . - The u s e of r e l - a t iv e l y l n r g e l a te r ? - 1 f l o a t s , c t .

a s h o r t d i s t a n c e f r o m t h e h u l l , c o n tr i b ut e d g r e a t l y t o t h e suc-

c e s s o f t h i s s e a p l a n e , s i n c e o ne of t h e g r e a t e s t d i s a dv a n ta g e s

of many boat seaplanes i s t h e l a c k of s u f f i c i e n t l a. t' er al sta-b i l i t y. i i e n c c , f l o s t s viero i n s t a l l e d u n d e r t h e rring t i p s o r .wing s t u b s a nd x e r c a t t s c h c d t o t h e s i d e s of t h e h u l l . A two-

f l o a t s e ap l an e o f f e r s more r e s i s t a n c e t o t .h c s i r than a c o r r e -

sponding boa t seap lane , b u t the fo rmer has good l a t e r a l s t a b i l i - .

t y, a l t h o u g h i t o f t en has b a r e l y e n o u g h l o n g i t u d i n a l s t a b i l i t y.

A f l o a t s e a p l o n c i s d r i v e n o f f i t s courao by s c u s s t r i k i n g i t

o n one s ide , 'more eas i ly than a boa t seap lane . I n a roug5 s e a ,

t h e wing f l o a t s t hrow 'a s e a p la n e v e r y e a s i l y o ff i t s c ou rs e.

Due t o t h e l a r g e lat oral f l o a t s , t h e a d va n tn g es of bo at

sea.plenen, a s t h e y h av e h i t h o r t o b e en k ~ o w n , o r e t o a c e r t a i n ,\

\

extent combined with t h e a dv an ta ge s of o r d i m r y f l o a t s e ap l an e s.


22/39

.. . N-X.. C A., Technical Uemo ran&um No.. 3 53 21

A b o a t seap lane, x i t h l a r g e f l ~ a t s e a r t h e h u l l , has g r a t lon-

g i t u 6 i r a l and l a t e m . 1 s t ~ ~ b i l i t y , n s p i t e of t h e s m l l a i r re-

s i s t a n c e , a nd , clue t o t h e c e n t r a l p o s i t i o n of a l l t h r e e f l o a t i ~

b o d i e s , i s not so r ea d i ly thrown off i t s c o u r s e i n a rough s a ,

a s an ordinary two-f loat s eaplane,

S in ce t h e 1 a t' bx a. l f l o a t s . c o n t r i b u t e 'cut l i t t l e t o t h e 103-

g i t u d i n a l s t a b i l i t y of a boa t seap lane , t h e i r r e a r and Torward

ends can be ex tended in long sharp p o i n t s , i n o r d e r t o l e s s ent h e a i r r e s i s t an ce and t o cu t smoothly th rough t h e waves.

Each f l o a t has s i x wa te r- t i gh t co rqar tmen ts . Th i s exten -

s i v e d i v i s i o n , a s compared with the volume of a water-tight $om-

par tmen t of t h e hu l l , i s prov ided , no twi th s t and ing t he add i-

t i o n a l weigh t and cos t i nvolved, because l eakage i s no t so

e a s i l y d i sc o v er e d i n t h e c om pl et el y i n c l o se d f l o a t s , a s i n t h e

hull. Thus a l i t t l e l a k a g e i n t o one of t h e f l o a t s would n o t

i n t e r f c r e w i th t h e take-off .T h e f l o a t s ar e each secu red by tv:o l ~ o r i z o n t a l t e e l t ubes

t o the h u l l and by f o u r v e r t i c a l s t e e l s t m t s t o t h e wing above

( F i g . 1 2 ) . The bottoms o f t h e f o s t s a r e sornewhzt higher t b n

t h e bot tom of the h u l l . Hence t h e dynarni-c l i f t of t h e f l o s t s

he lp s t o su2por-L th e sea p la ne on ly du r in g th e lorn speed a t t h e

s t a r t . S ~ o v e b out 60 lun (37 m il es ) p e r hour, t h e f l o a t s a r e

e n t i r c l y c l e a r , s o t3at t h e s e a p l a ne g l i d e s o n l y on t h e bo tt om

of th e hu l l .


23/39

N.A.S.2.. Technicai hIenoran&urn No. 353

u - h e o r e t i c a l l y t h e h u l l sh ou ld b e v e r y s l e n d e r i n

o r d e r t o d i mi n is h , t h e a i r r e s i s t a r c e ( d r a g ) sfld th e weigh t of

t h e b ot to m b r a c e s , By means of a ver y l a r g e number of towing

exper iments , w e s uc ce ed ed i n g i v i n g t h e t wo - s t m h u l l a shape

w i t h , w h i ch t h e s m l l r e s i s t an c e , r e q u i s i t e f o r a s h o r t s t a r t ,

mas o b t a i n e d w i t h t h e o r i g i n a l w id th of 1 .2 5 m (49 .3 i n . ) .0

Thi's wid th co r responds , as fo l lows f rom Tab le I , t o a v e r y

l a rg c : s t w l o a d i n g i n compar ison wi th what has h i t h e r t o been

c on si d er ed a l l o n a b l e .


24/39


25/39

N . A . Z . A . T e c h n ic a l ldemorandum No. 353

The narrowness of t h e h u l l d e n o t e e : c o n s i d e r a b l e s a v i n g- -

i n t n e vlrei,ght of t h e ~ o t t o m r a c e s , e s p e c i a l l y f o r a s e a p l a n e

Ta b l e I . Comparison of S t e p Loadings ( ~ o n t )

w it h heavy wing load ing , in which t i l e bo t tom s t r e s s e s from t i l e

w a t e r p r e s s x r e a r e u n u s u a l l y h i gh , d ue t o t h e hi.gh t a k e -o f f

' i

speed. With a road h u l l , t h e w eig ht of a l l t h e ?ar t s , c?.imen-

A i r p l a n e

tYYe

E n ~ l i s h 5

E n g l i s h P5 /3

E n g l i s h N 4

(Atalanta{T i t a n i a

En l i s h PS3b u r p )

L o a d i n k g

S t e p l e n g t hP e r m s t e p P c r ( s t e p l en g t h )

.m l e n g t h , Me t r i c 2P z r f t ; . s t e p ? e r ( s t e p le n z t h)

s io n e d ~ i i t h e f e r e n c e to t h e w a te r s t r e e s e s , w o u ld b e s o g r e a ta s t o l o s e n:gain most of t h e weight saved by t h e heavy ~ ~ i n g

l o a d i n g . I f i n d h e re a s o r t of r i ~ e t i J ~ i o n f what was i l l u s -

t r a t e d b y t h e S t a a k e n a ~ o n o p la ~ n e i t h i t s h s av y w in g l o a d in g .

F or t h e l a t t e r , a n e x c e p t i on a l l y f l e x i S l e land-ing g e a r had t o

S e dcvel-oped, i n ord.er t o av o id a n i n c r e a s e i n we ig h t w i t h r c-

I

F u l l

l o a d

kgl b .

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1450031967

f t . Is \ngth

~ u l l ~ i t h j ~ ~ l l ~ i t ha lone1 f l o a t s a l o n e f l o a t s

E n g l i s h

EU U r;l o n e floats646 645132

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12.471 1 25641 25641 1


26/39


27/39

N . A. C. A . T e c h n l c a l . Memorandum No. 3 53 2 6 '

c o v e r i n g impz-rt t h e c o r re c t c r os s- se ct io na l ~ 1 x 3 ~ ~ o t h c n h o le

g i r d e r . The l o ng i t ud in a l ri~sn?2ers . re so cu t ou t o r bu i l t up

t 'n at t h e y c o n t a i n s n l y t h e n ec e s s a r y d i a g o n a l s an d u p r i z h t s .

The s he c t c ie tal , cover ing i s p r o t e c t cd from l o c a l b u c u i n g bjr be-

i n g r iv e t e d t o t h e r i b s . I 1:rould l i k e t o des ig na te th e o u t e r

cove r ing of t h e box g i rd e r , w h ich. i s sub je c t ed t o e v e r y kind of

s t r e s s c on t r i bu t es i n a l a r g e d eg re e t o b ot h t h e t o r s i o m l

and bend ing s t r en g t h of th.e wing, a s t l f u l . l suppo r ting , I1 in o rde rt o d i s t i n g u i s h i t from t h e v e r y t h i n m e t a l c o ve r in g of t h o

. Junke r s and D o r n i e r ' ~ ings , which i s o f t e n r e f e r r e d t o a s "sup-

p o r t i n g , l l , r l t h o u g h i t . e a l l y adds b u t l i t t l e t o t h e t o r s i o m l

s t r e ng th of t h e w ings .

@>ny experiments have shown u s how t h e s t r e s s e s c a u s e d b y

t h e S end ing an d twis t inp; of such box s p ar s can b e computed i n

advance. I hope tint 21 .1 pe ten t ques t ions n i l 1 Soon be so f a r

se t t l ed , t b , t n e can pu b l i s h tk e se e rpe r i ln en ta l r e s u l t s and. t h e

computntion :::ethod. The r c s u l t s of. such s t r e n g t h , c a l c u l a t i o n s

. now zagrcz v e r y w e l l c i t h t h e e x pe r in e ct a l r e s u l t s . Sence each

small p a r t can be made of j u s t t he r ig h t s t r e ng th . A ccord ing ly,

t h e tkiclcness of t h e s h c e t - p e t a l c o ~ ~ e r i n g nd t h e c r o s s - s e c t i o n

of t h e corne r fla ,nge, as 1ike~:dise t3c: diagonal brace6 and bulk-

he ad s , g rz6-ua l ly dec rea se towarc? t h e ou ts id e . A t the same time,

t h e a d a p t a ti o n of t h e th i ck n es s of t h e m t e r i a l t o t h e s t r e s s

c2n b e 2uck more pe r f ec t t han i s t h e ca se i n other methods of

wing cons",ctlor? si nc e, i n them, t n c s t r c n g t n of a f l a n g e o r


28/39

L

N . X . C . A . Tec hn ic a l XerLorandum No. 353

o t h e r member r u n n i n g i n t k e d i r e c t i o n o f' the. span cannot be

changed el-ery one o r two met er s, as i n our method. S ince , in or e

o ve r, t h i s box g i r d e r i z g o r e r i g i d t ' r _ ~ , n ::y oxher f o r m of ning

s p a r , ' i t i s o b v i ou s , w it h o ut an y f u r t h e r f'omir!-as o r ~ a t h e r a t c -

a 1 d e mo n s t r a t i o n s , that the wings can b e v e r y l i g h t , s o l i g h t

i n f a c t t!nt t h e y c ar, b e m d e c n t i r e l y o l ~ er h a n gi n g w i t h a n 2 s -

p e c t r a t i o of 1 0 and e s s t r o n g a s r e q ui r e d f o r l oo p i n g azcl t a x -

y i n g . The wing has no t shown t h e l e a s t tendency t o whip o r even

t o t r e 2i b l e i n e ny of i t s p a r t s , al th ou gh we 'have give n i t v e r y

s e v er e t e s t s i n g l i d i n g and c ur vi ng f l i g h t .

S i n ce t h e q u e s t i o n of weight i s ex t remely i mp o r t a n t ,

would g la dl y have had, f o r my own purposes and f o r yo ur i n f o r -

mat ion , an a c c u r a t e weight cornpa.rison between o ur rnetal wing

and o t h e r a n d of c o r r e s p o n d i n g l y f a v o r a b l e

a i r - r e s i s t i n g p r o p e r t i e s . U nf or tu na te ly, I have not succeeded

i n ob ta i n in g any such compara t ive f i ; y . r e s f o r woodelz wings and

c a n , t h e r e f o r e , o n l y ma,2ce t h e f o l l o ~ ~ ~ i n g t a t e m e n t s . The ~ r e i g h t

of o ur a i q l a i i e i s e x a c t l y t h e s a me a s t h ? ~ ~ ; f t h e En g l i s h S o a t -

s e a p l a n e F 5. The s a f e ty f a c t o r of t h e l a t t e r ( 3 . 7 5 i n c a s e A )

i s s o s m l l t h a t , f o r t h i s r e as on a lo n e, n e i t h e r l o o p in g n or t a xt

y i n g i s p o s s i b l e . I n o ur se ap la ne , t h e s a f e t y f a c t o r i s s u f f i -

c i e n t f o r b o th l o o p i n g and t a xy i ng , s i n c e i t i s s t i l l 2 . 5 t i x e s

t h e mmxirmm s t r e s s i n ti l e s h a r p e s t c u r v i n g f l i g h t ( S e e "8 a u s i c h -

e r h e i t und Kurvcnf lug , I t "Ze i t sch r i f t ff i r F lug techn ik und >do to r-

l u f t s c h i f f a h r t , " 1922, p o l ) . Of c o u m e t h e s e f i g u r e s a f f o r d no


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X . A . C . A . Technical llemoran2um No. 353

d i r e c t c ompa ri so n of t h e win g we i g h t s . I t i s qa n i f c s t , howcvcr,

t h a t , on the o t n e r s t r u c t u r a l p a r t s , such a s t h e b ~ l l nd t a i l

u n i t , whic h a r e thro11.ghout o f l i g h t e r c o n s t r u c t i o n t h a n t h c

wings , on ly such s m l l weigh t s a v i n s can b e m d e, t'hat t h e s m a l l -

e r v c i g h t , i n c o ~ ~ p n r i s o n i t h t h e F s e a p l z n e , m s t be accoun ted

f o r b y t h e w ings.

S a f e t y i n t h e ev en t of i n j u r y of i m p o r t a n t p a r t s . - A wing

s h o u l d n o t . b r e a k from b e in g h i t g u n f i r e n or from

defects , when any one of i t s struc turE i1 xembers i s i n j u r e d . No

l o c a l i n j ur y , e i t h e r t o a l e ad i ng - o r t o a t Ta i l i n g - e d g e s e c t i o n

can cnda,nger t h e sa f e t y of t h e wing.

I t i s a l s o o b vi o us t h a t t h e u p p e r an d lo wer s h e e t -me t a l

c o v e r i n g of t h e b ox g i r d e r must b e v e r y s e r i o u s l y a nd e x t c n s i v c -

l y i 'n ju re d b e f o r e t h e wing b r e a k s . 8 f - t ~ ~t h e c om pl et e r u p t u r e

of one of t h e di a go n al o r v e r t i c a l S r a c i n g s t r i p s , t h e t r an s -

v e r s e s t r e s s mould b e t r a n s m i t t e d b y t h e n' ei g hb o ri n g t r a n s v e r s e

mall t o th e o t h e r members, though wi th a d i m i ni s h ed s a f e t y f ac -

t o r . When t h e f l an ge o f rz longi tudinal member i s i n j u r e d , t h e

s t r e s s , . p r ev i o u sl y S or no b y i t , i s t r a n s mi t t e d ' t h r o u g h t h e .up-p e r an d l ower c o v e r i ng , t o t h e o t h e r l o n g i t u d i n a l member.. The

wing i s , t h er e fa r e , s t a t i c a l l y i ~ d e t e r m i n a t e n each , s e c t i o n

a nd c a nn ot b e b ro ug ht t o t h e b r e ak i n g p o i n t by i n j u r y t o o n l y

o n e of i t s s t r u c t u r a l . c or ip on en ts .

Saf e t v a g a i n s tnets

e r i n g an d c o r r o s i o n . -A

me t a l c o v e r i n g


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M - ~ L . .A. Te c h n i c a l F e m g ~ n d u m No. 35 3

i s i n d i sp e n sa b l e f o r m k i n g a n a i r p l a n e i nd ep end ent of t h e

we ath er. Something more i s r e q u i r e d , h owever, t o p r o t e c t i t

f u l l y a g a i n s t c o r r o s io n . U n pr o te c te d d ur al um in i s g e n e r a l l y b ut

l i t t l e a f f e c t e d by t h e a tm o sp he re . Whenover i t i s j o i n e d t o

o t h e r me ta l s , however, a g a l v a n i c c e l l i s formed which corrodes

e i t h e r t h e duralurnin o r t h e o t h e r m e ta l , a c c or d i n g t o t h e s i g n

of t h e e l e c t r i c a l t e n s i o n . F or i n s t a n c e , d ur al um in i s very rap-

i d l y c o r r od e d when j o i n e d t o b r o n ze o r c o p pe r a n d, l i k e wi s e ,z i n c i s ra p i d l y ea t en away when i n con tac t wi t h dura lumin and

s ea-wat er. Whelnever d i fferent copper-conta in ing dura lumin a l -

l o y s a r e j o in ed , a s , e .g . , , r i v e t s c o n t a i n i n g more c o pp er w i t h

s h e e t s c o n t ai n i n g l e s s c op pe r, t h e a l l o y c o n t a i n i n g l e s s c opper

w i l l cor rode .

F o r t u n a t e l y, o r d i n a r y s t e e l and d ur al ur ni n g e n e r a l l y g i v e

r i s e t o v er y s l i g h t e l e c t r i c a c t i o n . On t h e c o n t r a r y , s t e e l

co n t a i n i ng much chromium o r n i ck e l can b e used on ly wi th g r ea t

cau t ion . Dura lumin i s v e r y r a p i d l y d e s t r o y ed b y r ~a n y good

s t e z l s , i n c l u d i n g , among o t h e r s , Kr up p' s n o n - r u s t i n g r i c h

n i c k e l - s t e e l , . In o r d e r t o a v o i d f a i l u r e s , e ve ry k in d of s t e e l

must t h e r e f o r e b e t e s t e d w i t h r e f e r e n c e t o t h e e l e c t r i c t e n s i o n

i t d e v el o p s i n c o n t a c t w i t h d u r al u mi n . Moreover, t h e u s e of

o t h e r me ta l s, ev en s t e e l , i n c o n j u n c t i o n wi t h d u ra lu min , s h ou l d

b e avo ided as much as p o s s i b l e . An all -d ura .lu rni n wing, i n which

o n l y t h e main f i t t i n g s , f o r a t t a c h i n g i t t o t h e a i r p la n e , a r e

s t e e l , i s l e s s e nd an ge re d 5 y c o r r o s i o n t h a n a ny o t h e r k i n d of

wing.


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F or p e r f e c t p r o t e c t i o n a g a i n s t c o r r o s i o n , a l l p a r t s r m s t

b e w e l l p a i n t e d , b o t h i w s i d e alid a r t s i d e . Every i n e i v i d v a l p a r t

o f t h e f i c i s h e d wing of o u r s e a p l a n e c an b e i n c p e c t e d a n d p a i n t -

ed on a l l s i d e s , dve t o t h e r e n o v a 5 i l i t y of t h e l ea di ng - and

t r a i l i n s - e d g e s e c t i on s.

EZSV a .cces- .s i i ) i l i ty of zvery s t x c t i l r e l p a r t . - The l a d i i . 1 ~ -

a nd t r a i l i n g - e d g e s e c t i o n s of t h e wing ca n b e v e r y a s i l y re-

moved by simply loosening a few e x t e r n a l n u t s . In o r d e r t o 'iz-

c r e n s e t h e a d v a n t a g e s c on n ec te d w i t h t h e re inova lo i li ty o f th e

l e a d i n g - and t r a i l i n g -e d g e s e c t on s, t i le l a t t e r a r e d i vi d ed i n-

t o equal , independe 'l -t 3o r t ions . .

The wing g i r d e r s can b e renoved by l o o s e n i ~ g h e b o l t s .

which fas ten them to the s tu 'os o n '90th s i d e s of t h e h u l l , o r t o

t h e n e s t j ~ i n g e c t i o n , vrllen t h e m i - r , g ~e r e e ac h d i v i d e d i 3 t o

s e v e r a l s e c t i o n s . The c o- cn ec ti on s c o c s i s t e n t i r e l y of s t a c l .

Each p a i r of f i t t i i ~ g s , e c ur e d b y two ' o ol t s, s e r v c s t o t r a n s -

m i t t h e s t r e s s e s i n t h e u F p e r and lo mer f l a n g e s , a s l i k e w i s e

t h e s h m r i n g s t r e s s e s . Th i s inethod o f a t t a ch i n g has p rovcd

v e r y s a t i s f a c t o r y . A f te r a s e r i c s of t e s t s d xt cn di ng o ve re ig h t z ionths , 6u r i ng u~hic 'n more .than 7 0 f l i g h t s were rcadc, t h e

s e a p l s n e , when t ak en a ga r % f o r t r a n s p o r t a t i o n ; s t i l l l ooked

Inexocnsivc manufacture .- This as s3 mc s t l l a t o n ly s i 5 ~ l . e

s t r uc t u ra . 1 p a r t s , s uc h as s r ~o o t h hc ; t - r r i e t~ l and s tamped opc- 1


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2 . l . A . C . A . Technica l Memorandum No. 353 31

work p a r t s , b u t no tu bes and no hol low members a r e used . For

c h ea p p r o d u c t i o n , t h c win g p r o f i l e a nd c ho r d r e i mi n t h e same

throughout t h e whole span.. A l l r o u nd i n gs of t h e win g t i p s ,

c t c . , a r e a vo id ed s i n c e , as founc? by exp eri men t, they do not

a p p r e c i a b l y d i m i n i s h the d r a g . - The c o n s t r u c t i o n c o s t i s most

reduced by d im in i sh i ng t h e work of a s s e m b l i n g as much a s po ss i-

b l e , because by t h e f a c t o r y perforr ran ,ce of most of t he work,

s o l o n g ' a s t h e i n d i vi d ua l p a r t s a r e s t i l l separa te , much spacei s saved., a much g r e a t e r d i v i s i o n o f l a b o r i s p o s s i b l e , a m c h

b e t t e r c o n t r o l of t h e workmen and t h e q u a l i t y of t h e i r work i s

p o s s i b l e a ,n d a lmch g r e a t e r u s e of s p e c i a l t o o l s ca n b e made.

Ribs and some o t h e r p a r t s can b e made, even i n small num-

b e r s , a f t e r a k i nd o f- q u a n t i t y p r o d u c t i o n b y t h e u s e o f s pe -

c i z l t o o l s . Xos t o f th e work done i n m k i n g a box girder con-

s i s t s i n r i v e t i n g t o g e t he r t h e p a r t s of t h e l o n g i t u d i n a l mem-

b e r s a nd i n r i v e t i n g t h e f l a n g e s t o t h e t o p and bottom m et al

s h e e t s , w her eve r t h e s e p a r t s a r c g e p a ra t e . They a r e t h e n f z s -

t e n e d i n a s imple rranner t o th e box g i r d e r , wi thou t th e workf s

b e i n ? d e l a y e d b y d i f f i c u l t l y a z cc s s i b l e r i v e t i n g . A s a r e s u l t

o f t h i r s imple m2nufac tu -r ing method, th e d iv i s i o n o f l a bo r

i s a l r e a d y f a r advanced. f o r t h e few s e a p l a n e s we h av e a l r e z d y

b u i l t . I n f u t u r e , a l l t h e r i v e t i n g w i l l b e d o n e 5 y s p e c i a l

r i v e t e r s vrho w i l l d o n o t h i n g e l s e . The q u a l i t y of t h e work

h a s a l s o b e en g r e a t l y improved '0:~ t h i s d i v i s i o n of l a b o r.


33/39

N,B.C.LZ. Technical l&rnora~?d-am No. 353.

Launching gars . - One of t h e most d i s a g r e e a b l e o b s t a c l e s

mas t h e sk j l l owne ss of t h e Oresund, which l:ras l e s s than 1 n c t c r

( 3 . 2 8 f t . ) d e e p f o r a d i s t a n c e of more tkt tn 300 n (984 f t . )

f ro m t h e s h o r e , t h e b ot to m b e i n 3 p e r t l y s t o n y a n d p a r t l x . muddy.0

Due t o t h e g r e z t d i s t a n c e betw een t h e 1 znd and s u f f , i c i c n t l y

d e ep w a t er , t h e c o n s t r u c t i o n of a c o n c r e t o runway o r t h e d r a g --

i n g o f c s u f f i c i e n t l y v i d e c h a n n el would l x we c o s t more t h a n

t h e compxiy co ul d a f f o r d . , Ne t h e r e f o r e b u i l t . t n o l a u nc h i ng

g e a r s , olie f o r e ac h s i d e o f t h e s e a p l a n e ( F i g s . 1 2 and 1 3 ) .

They suppo rt t h e sea.plane by ae ans of s p e c i a l l y p r ov id ed p o i n t s ,

of at tac hmen t on each wing. These la un ch in g gears keep the

h u l l a n d f l o a t s from s t r i k i n g t h e v e r y uneven bo tt om of t k e

Oresund and thu s pr o te c t them from in j u r i e s which might c ause

l e a k s . The s i z e of t h e wh ee ls w a s determined 'oy experiments

on t h e spo t n i t h v n r i o u ~ l y oa& ed r o l l i n g d i sk s .

F or c t t a c h i ~ g nd deta chi ng t3.e l aun chi ng gez rs , a U-

sbap .ed f loa t w a s e q l o y e d , fro m which o n e c ou l d r a d i l y n o rk .

Thc l aunch ing gea r s can b e de tached i n f ou r minu tes by two ux-

s k i l l e d v!orkmen, b y loo sen ing th e tu rn 'ouc lc le s on t h e b ra c in g

c a b l e s and r eno vin g t h e b o l t s f r o n t h e wing f i t t i n g s of t h e ,

s e a p l a ne . The l a u s c h i n g g e a r s t h e 3 f l o a t c/ f t!lmselves. I t

l i k c n i s e t a k e s f o u r m i n u t e s t o a t t a c h t h c r . In o r d e r t o p re-

v e n t t h e s u p p o r t i n g t ower of t h e hav y l n u n c h i n g g m r, i n r ou gh

wa te r, from damaging th o ni.ng b e f o r e i t c a n b e a t t a c h e d , t h e

wel l-padded l av inching g s r i s f i r s t sus?ei?&cd f r o g t h e n i n g b y


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3 . A . C A . Technical l$emor~ndun O . 353 33

a ca b l e which c a n S e s h o r t e n e d b y rnesns of a Pand winch secured

ti3 t h e lau nc hin g ge ar , u n t i l t h e l a t t e r i s l i f t e d a b o u t 50 c m .

( 2 0 iil.) out of t h e w at e r a nd i t s a tt ac hm en t f i t t i n g en G ge s

i n t h e co r respol ld ing f i ? ; t i n g on t,\e x ing , so t h a t t h e n o i n t e d

f a s t e n in g -b o lt s can b e i n s e r t e d - A s soon a s ( b y t h e g a d u a l

em ergence o f . t h e l a u n c h i ~ g w r from t h e water ) a p o r t i o n of

i t s vfeight i s b o r n e . b y t h e wing, i t fol lows every motion of

t h e seap lane, s i nc e t h e motion of t h e water can then no Longer

gi-re i t a n y i-notion of i t s o m .

Tiiese l aunch ing gears have proved v e r y s a t i s f a c t o r y an6

m i l l t h e r e f o r e f i n d u s e i n many s imi l a r cases where , a s wi th

u s , i t i s nec ess ary t o edonomize.

T r ~ . n s l a t on b y Dwight- 1. E i n e r,N a t i c m ~ l d vi so sy Committeef o r A e ro n au t ic s .


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N . A . C . A . Technisal Uemorandlm No.353

a , Pay l o a db , Cost pL:r . p s r s o nc , Flight tiae

d , Pay l o a d , unit 800 kge, Flight time, unit 4 hrs.

0 10000 23000 0 10000 20090Total weight, kg

m

, lurnir,g.time, nit 4 secondsTo t a l 3eight, 1'0. -

0 10000 BOO00 0 10000 201300Total weight, kg


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NACA TM 353 Recent Experiments With Large Sea Planes