NACA RM SL9L07a Full-Scale Hydrodynamic Evaluation of a Modified Navy J4F-2 Amphibian With a...

7/27/2019 NACA RM SL9L07a Full-Scale Hydrodynamic Evaluation of a Modified Navy J4F-2 Amphibian With a 0.425-Scale XP5M-1 Hull Bottom. TED No. NACA DE325

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NAcA R.M SLgL07a B 1%NATIONAL ADVISORY COMMITTEF: FOR AERONAUTICS

lSESEARCH W O R A N D U M

f o r t h e

Bureau of Aero nau tic s, Department of t h e Navy

FULL-SCAIX HYDRODYNAMIC EVALUATION OF A

MODIFIED NAVY J 4 ~ - 2 MPHIBIAN WITH A

0 . 425-SCU X P S - 1 .HULL BOTTOM

!ED NO. NACA DE325

By Norman S. Land, John M . E l l i o t t ,and Kenneth W . Chr i s topher

SUMMARY

An in ve st i ga t io n was made t o evalu ate t he hydrodynamic q u al i t ie s ofa 0.4 25-s cale model of t h e Navy XPW-1 h u l l , w hich x a s i n s t a l l e d on amodified Navy J~F-2 am ph ib ian . L o n g i tu d i n al a nd d i r e c t i o n a l s t a b i l i t ydurin g take-off and landing, low-speed maneuverabili ty, spr ay charac-te r i s t i c s , and t ake-off per fo rmance were inves t ig a ted . The behavior ofth e a i rp lan e i n moderately rough water was a l s o observed. The opinionso f t h r e e p i l o t s h ave bee n c o r r e l a t e d w i t h t h e d a t a .

INTRODUCTION

An eva lua t ion , us ing a f ly in g t e s t veh ic le , o f the hydrodynamic

ch ar ac te r i s t ic s of two exper imental types of h u l l bottom was reques tedof the NACA by th e Bureau of Ae ron aut ics , Department of t h e Navy. ANavy J 4 ~ - 2 mphibian was chosen as the veh icle s ince i t was the smallestd t i e n g i n e a i r p l an e r ea d i ly a va il ab le . The a i r p l an e ( ~ u ~ e r o No. 32976)was fu rn is he d by th e Bureau of A eron autic s and modified by th e Edo A i r -cr a f t Corpora t ion under cont ract t o th e Bureau of Aeronaut ics so th atany o f severa l hu l l bo ttoms cou ld be ins ta l l ed . Th is paper desc r ibest h e t e s t s and p r e s e n ts t h e r e s u l t s o b t ai ne d from a f l i g h t i n v e s t i g a t i o nof th e hydrodynamic ch ar ac te ri st ic s of t he J4F-2 with a 0.425-scale

bottom of the Navy XP5M-1 f l yi ng boat . The inv est ig at i on was conducteda t Langley Aeronaut ical Laboratory usi ng th e procedures descr i bed i nre fe rence 1 a s a gu ide. < z ; &

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se e2 CONFIDENTIAL NACA R M SLgL07a

0e e

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Beeo A l l of t he reg ular f l i g h t t e s t s were made by one NACA p i l o t , Two0

bee v i s i t i n g p i l o t s m d e one f l i g h t eac h t o f u r n i s h a d d i t i o n a l op in io n s on0.

D o t h e h y d r o - m i c b e ha vi or of t h e a i r p l a n e . The o v e r - a l l o p i ni o n s of a l l9 t h r e e p i l o t s were o b t ai n ed f o r c o r r e l a t i o n w i th t h e data.

DESCRIPTION OF AIRPLANE

The airpl ali e, a s modified by th e Edo A ir cr af t Corporation,incorpora ted a sp l i ce l in e i n the sk in and f rames above the ch ines soth a t any o f se vera l hu l l s cou ld be in s ta l l ed . Above t h i s s p l i c e l i n ethe a i rp l ane had on ly minor modi f i ca tions which resu l t ed i n a s l ig h t lyreduced rudder are a and a landing gear th a t r e t ra ct ed back and up underth e wing ins tea d of in to the fuse lage . Photographs of th e mod ifieda ir pl an e and th e stan dard ~ 4 ~ - 2 i rp la ne a re shown a s f i gu res 1 an d 2.A three-view drawing i s shown i n fi g ur e 3 and the pe r t in en t d imensionsa r e l i s t e d i n t a b le I. A l ines d rawing o f the hu l l i s shown i n fi gu re 4.

The most important fea tu re of th e hu l l was i t s long afterbody whichhad a length-beam r a t i o of 4.9. This afterbody had a warped bottom withan ang le o f deadr i se of 20' a t the s t ep and s t e rnpos t and a maximumangle of deadrise of 4 4 O a t approximately 54 percent of i t s l eng th . Thest ep had a vee plan form with a 6 included angle, and a depth of 5 per-c e n t o f t h e be an a t t h e k e e l .

The plating of the forebody bottom was n ot f l a t bu t was dished inapproximately 1/16 inch between frames, thu s forming a s e r ie s of shallowwaves. The a i rp lan e was rece ived and t e s te d i n t h i s cond i t ion .

The fo re and a f t loca t io n of th e cen te r o f g rav i ty of t he a i rp lan ewas adj ust abl e by means of a l i q u id b a l l as t system. This systemcon sis ted of two tanks, one locat ed forward and one a f t , and a t ra ns fe rpump to s h i f t the l iq u id . The l ev e l of th e l iq u i d i n the forward tank,which was used t o determine the cen te r-o f -g rav i ty loca t ion , was shownby an ind ica tor on the ob server ' s panel . Ethylene glycol was used fort h e b a l l a s t l i qu i d . With t h e a i r p l a n e l o ad ed f o r a t e s t , t h e a v a i l a b l ecenter-of -g rav i ty range was from 18 t o 3 1 pe rce nt of th e mean aerodynamicchord.

The following cont rol-s urfac e def l ect ion s were ava i la ble : e l e v a t o r s30' up t o 20 down, rudder 28O ri g h t or le f t , and f l ap s 0 t o 40 down.

The engines were Ranger s ix-cyl ind er, in l i ne , a i r-c oole d engineswi th a tak e-of f ra t i n g of 200 horsepower each. The propellers were

1Beech two-blade, con tro lla ble -pi tch , wooden pr op el le rs , 85- inches in

2d i m e e r .

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The gross load a t th e s t a r t of each f l i g h t was 5230 pounds. Decreasein 'g r os s weigh t dur ing the f l ig h t due t o consumption o f gaso l ine and o i lwas never gr ea te r than 200 pounds, o r 4 percen t of the s ta r t in g weigh t.The gross loa d of 5,230 pounds corresponded t o a g ross l oad c oe ff i-

a,c i e n t C of 1.0 7 where Cb =-

nd i s gross load i n pounds;4 3 wb3

w i s sp ec if ic weight of water i n pounds per cubic foot ; and b i smxi- beam i n fe et) and a fu l l -s in e gross load f o r t he XP5M-1of 68,100 pounds. A t t h i s gross load, the scaled-up wing loadingsand power loadings of the J ~ F - 2 ompare with those of the XPP-1 a sfol lows :

Thus, a l though the bot tom of th e hu l l of th e modif ied J ~ F - 2 was a s c a l emodel of the bottom of th e XPW-1, th e wing loading a t the t e s t gros sl o a d was 4 percen t g rea te r than t h a t corresponding to the XP'JM-1 an dthe power loading was 25 t o 32 percen t l e ss .

INSTRUMENTATION

The inst rumentat ion was s u b s t a n t i a l l y t h e same a s t h a t us ed f o rprev ious inv es t ig i t ion s o f the hydrodynamic ch ar ac te r i s t i c s o f f l y in gboats . Airspeed, waterspeed, e le va tor and rudder def le ct ion , r evo lut ion sper minute of each engine, and time were recorded on the NACA eventsrecorder. An NACA three-component li n e a r record ing accelerom eter witha natural frequency of approximately 15 cycles per second was used ona f e w f l i g h t s . I n a d d it i on , trim and time were recorded on a modifiedgyro taken from a C - 1 v e r t i c a l - f l i g h t a u t o p i l o t .

The fo l lowing s pec ia l ind ica t in g ins truments were a l s o used : a nWCA o p t i c a l trim ind ica to r, e leva tor-def lec t ion ind ica to r, wa te rspeedind ica to r, and a b a l l a s t - l o c a t i o n i n d i c a t o r. The a v a i l a b l e f l i g h tins truments were: sen s i t i ve a i r sp eed ind ica to r, sen s i t iv e a l t ime te r,ra te-of -cl imb indic ato r, turn-and-bank ind ica tor , di re ct i on al gyro, anda r t i f i c i a l horizon.

The loc at io ns of t he instruments i n the air pla ne a r e shown i nf i g u r e 5.

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Low-apeed maneuverability.-A s

an indica t ion of th e maneuverabil i tyon the water a t low speeds, th e time t o make 3600 tu rn s wsls measured.These tu rn s were made with the rudder hard over, ai di ng the turn , inn erengine id lin g, and with va riou s amounts of power from th e ai din g engine.

RESULTS AND DISCUSSION

Take-off s t ab i l i t y . - The trim l i m i t s of s ta b i l i t y a re shown i nf i g u r e 6 f o r f l a p - d e f l e c t i o n s of o0 and 20'. Data were not obtainedbeyond 80 f e e t pe r second, alt ho ug h normal getaway spee ds were muchhigher. :It 80 f e e t per second the lower l i m i t o f s t a b i l i t y was below 2Otr im and the p i l o t r epor ted a t endency to yaw i n t h i s reg ion . The deter-minat ion of th e lower l im it of s t a b i l i t y a t higher speeds was there for eno t considered adv isab le . An a r b i t r a r y l im i t of 2 trim a t h ig h s pe ed swas s e t a s a minimum f o r s af e op eration f o r th e remainder of the inves-t i g a t i o n . The upper trim l i m i t of s ta b i l i ty was not determined a thigher speeds because th e l i g h t load on the water made t he determinationv e r y d i f f i c u l t .

W i n g t h e t ak e- o ff r u ns , p o r po i si n g was found t o be only one ofthe l im i ta t io ns on e leva tor de f lec t ion and cen te r-o f -g rav i ty pos i t ionf o r s a t i s f a c t o r y t ak e -o ff c h a r a c t e r i s t i c s . These l im i t a t i o n s a r e b e s ti l l u s t r a t e d by t h e t r i m t ra ck s shown i n f ig ur e 7 f o r t y p i c a l t a ke - of f swi th th ree d i ffe r gn t e leva to r de f le c t ions . With a smal l up-eleva torde fl ec tio n of -30: the take-o ff was s t a b l e u n t i l , a t h i gh sp ee ds , t h etrim penetrated the lower trim l i m i t o f s t a b i l i t y, a nd p o r po i si n gof 3O amplitude occurred. A t t h i s l o w t r i m t h e d i r e c t i o n a l s t a b i l i t ybecame marginal and the run was discontinued. A l l of the low-angleporpois ing encountered on f ixed-e levator take-o ffs occurred a t highspeed. The lower-limit porpoising which i s usual ly observed just abovehump spe ed on most f ly i n g boa ts was not encountered with any elevators e t t i n g u se d. A t an intermediate e levato r def le ct io n of -60, the take-o f f was f r ee of porpoising, a l though ther e was some upward p it c h a f t e rgetaway. With th e gr ea te st up-ele vator de fl ec tio n (-12.5') shown i nf i g u r e 7, high-angle porpo ising of 4 ampl itude occur red and an abrup tand objectionable upward pitch was encountered immediately a f t e r getaway.

The l i m i t a t i o n s on e l e v a t o r d e f l e c t i o n a r e f u r t h e r i l l u s t r a t e d i nf igu re 8 where the range of s t a b le e leva tor de f lec t ion ava i lab le t o thep i l o t i s shown throughout the entire take-off speed range a t a given f l apse t t i ng and cen te r-o f -g rav i ty loca t ion . A t low speeds, any elevators e t t i n g was permissible a s no long i tud inal in s ta b i l i t y was encounteredwithin the complete range of avai lable e levator def lect ion. A t i n t e r -mediate speeds, the usef ul e le vato r d ef le ct ion s were l im ite d by porpois inga t high or low t r i m s . A t speeds near getaway, th e ele va tor s had t o be

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above a+minimum value t o avo id e i th e r low t r ims or lower-l imitpo rp ois ing . The el e v at or s had t o be below some maximum a t getaway t oavoid a sharp upward pi t ch which could ea si ly l ead t o a s t a l l .

The l im i t in g e leva tor de f le c t ion s fo r f ixed-e leva tor t ake-off swere determined from th e d ata shown i n fi g u re 9 (mximum amplitude ofporpo is ing) , ig u r e 10 (minimum tr im beyond hump sp eed), and f i g u r e 11(angula r ve loc i ty a f te r getaway) . E l e v at o r d e f l e c t i o n s l i m i t e d byp o r p o is i n g were de t e m i n e d by a p p ly i ng t h e u s u a l c r i t e r i o n o f 2 a ll o wa b lemaximum ampl itude o f porpo is ing to the fa i r ed da ta o f f igu re 9. Duringt h e t e s t s t h e p i l o t a nd o bs er ve r n ot ed t h a t t h i s m ag nitud e of o s c i l l a -t i o n was not object ionable even fo r such a small a i r pla ne . The per iodof the porpois ing o sc i l la t i on s averaged 1.6 seconds per c ycle and rangedfrom 0.7 t o 2.5 seconds per cyc le. The accompanying ac ce le ra tio nswere very low. The eleva tor def lec t io ns a s l imit ed by low trim a t highspeed were determined from the fa ir e d data of f ig ure 10 by using th epreviously mentioned arbi t rary l i m i t of 2 minimum trim f o r s a f e o p e r a -t io n. The ele va tor def lec t ion s l im ited by upward pi tc h a t getaway weredetermined from a co rre lat i on of th e fai re d data of f ig ur e 11 with thet e s t p i lo t ' s comments, f ig ure 12 . Angula r ve lo c i t i e s g rea te r thanapproximately 60 per second were i n gene ral considered undesir able byt h e p i l o t . The u p -e l ev a to r d e f l e c t i o n r e s u l t i n g i n a n a n g u la r v e l o c i t yof 6O per second was accord ing ly judged to be the h ighes t sa t i s fa c t o r ye l e v a t o r s e t t i n g .

These l i m i t s fo r de f l ec t io n o f the e leva tor a s de te rmined by lower-and upper- l imi t porpo is ing ( f ig . 7 ) , by low trims a t h ig h s pe ed s ( f i g , l o ) ,and by abru pt upward pi tc h a t getaway ( f i g . l l ) , r e p l o t t e d a g a i n s tcen te r-o f - g rav i ty loca t ion i n f ig ure 13. Th is f igure shows th a t por-p o i s i n g d i d n o t l i m i t the e lev ator range, but th e range was l i m i t e dby low trims a t high speeds and by obje ction able jump ta ke- offs . Therange of f ixed-e leva tor de f l ec t ion s su i t a b le fo r t ake-off i s s e en t o b e5 0 o r l e s s .

The e le v a t o r s e t t i n g s s u i t a b l e f o r f l i g h t j u s t a f t e r t ak e- of f a r ea l s o shown i n f i gu re 13 . These contr ol-s urfa ce de f le ct io ns wereconsiderably below those se t t i ng s which a r e usab le on th e water. A

l a rg e p u l l f o r c e was n e c e ss a ry wn il e on t h e m t e r t o h o ld t h e e l e v a t o r si n th e acc epta ble range. One p i l o t commented: "T ran sit ion from watert o a i r was s lugg ish and p i lo t - impress ion i s th a t he, perso nal ly, hadl i f t e d th e s ir pl an e by main st re ng th and had almost been unsuccessf'ul."

Of th e th re e p i l o t s who sub mitte d comments, two were of th e opi nio nth a t sa t i s fa c t o r y ins t rument t ak e-off s cou ld no t be made. Two p i l o t ssummarized t h e l o n g i t u d i n a l s t a b i l i t y a s f a i r ; one r a t e d i t a s p oo r.( s e e t a b l e 11.)

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Take-off performance.- An att emp t was made t o determine th e ef f e c tof e leva tor def lec t ion , cen te r-of -grav i ty loca t ion , and f l ap def lec t ionon th e take-off performance by an an aly sis of reco rds of fix ed- ele vat ortake-offs . The r e su l t i ng dat a s c a t t e r ed r a th e r bad ly i n s p i t e o f anapproximate cor rec t ion for wind ve loc i ty. This sca t t e r i s be l i ev ed t obe due t o the lac k of adequate in fo rm ti on on the wind and i t s e f f e c t s ,and unavoidable va ria t io ns i n pro pel ler th ru st . Take-off t imes rangedfrom 25 t o 45 seconds. The avera ge ac ce le ra ti on between hump speed andgetaway was ap p ro x imte ly 2 f e e t per second per second.

Two p i l o t s ra ted the take-off t ime and d is tance as f a i r ; the th i r dconsidered them poor.

Landing s t ab i l i t y. - The re su l t s of th e landing inves t iga t ion a r esummarized i n f i gu re 1 4 a s a p lo t of the number of skips a ga ins t landingtrim f o r smooth-water landings. The si ng le skip t h a t was of ten observedappeared t o be of no consequence as th e amplitude of motion i n trim wasr e l a t i v e l y s m a l l and, i n gene ra l, t h e la nd ing s t ab i l i t y was considereds a t i s f a c t o r y. No s ign i f i c a n t t r ends w i th l and ing trim o r p os i t i on o fth e cen ter of g rav ity were noted.

The ai rp la ne had a tendency t o trim down ra pi dl y immediately a f t e rcontact and required a ra pi d up-el evato r movement to preve nt th e t r i mfrom becoaing dangero usly low. Occ asi ona lly t h i s trimming down w asaccompanied by yawing. The tendency t o trim down a t con tac t wasconsidered object ionable by a l l thr ee of t he p i l o ts who f lew the airp lane .The time history of a t y p i c a l la nd in g ( s ee f i g . 1 5 ) i l l u s t r a t e s t h i snosing-down tendency.

The thr ee p i l ot s bel ieved t h a t th e hydrodynamic c ha ra ct er is t i cs wouldpermit sa t i s fac tory ins t rument landings .

Low-speed man euv era bil ity .- The time t o complete 3600 tu r n s i s showni n f i g u r e 1 6. A t the higher engine speeds there was no s ign i f ican td i ffe ren ce between tur ns made t o the r ig h t o r l e f t . A t low engine speeds,however, the data would seem t o i ndi cate an inherent tendency t o t ur nr i g h t . Su f f i c i en t da t a were n o t o b t ained t o d e f i n i t e l y e s t ab l i sh t h i stendency a s the heading of th e a i rp lane r e l a t iv e t o the wind a t t h e s t a r tof th e tu rn probably inf luenced the. data . Regardless of th i s uncer tainty,th e t ime t o complete a t u r n was l ong fo r a l l co ndi t ions t ha t were i n ves t i -gated. Such a slow r a t e of tu rn might be expected with th i s long h u l l .

Two p i l o t s considered t h e low-speed ma neuv erabil ity on th e water t obe poor; one re po rte d it t o be good.

D i r ec ti ona l s t a b i l i t y . - The d i r ec t i o na l s t ab i l i t y a t a speed justbeyond the hump and a speed near getaway i s i n di c at e d i n f i g u r e 1'7. Thep i l o t never used l e f t rudder during take-off . A t a speed just beyond the

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hump, it was necessary, i n li g h t winds, t o use a lar ge amount of ri g h trudder and di ff er en t i al power. I n s trong winds, no di ff er en t i a l powerwas req uir ed and le s s rudder de fle ct io n was needed. A t high speeds,a few degrees of rudder were sufficient. On sever a l t ake-offs , thep i l o t no ted a s t rong tendency t o waterloop a t high speeds and a t t r imsbelow 2O.

One p i l o t r a t e d th e d i r e c t i on a l s t ab i l i t y and con t ro l f a i r , oner a t e d them poor, and the t h i r d had no comment.

Spray ch ar ac te ri st ic s, - Two ty pi ca l spray photographs a r e presentedi n f i g u r e 1 8. Such photographs have been analyzed and the results areg iven i n f i gu re 19. The curves shown a r e drawn through th e p oi nt srepresent ing the peaks of bow spray b l i s t e r s a t the various speeds. A tlow speeds, the p i l o t bad no l a t e r a l c on t ro l a nd t h e a i rp l ane hee l ed soth at one or the other of th e wing-t ip f l o a ts was i n the water. On th ewing-high side no spray entered the propeller. On the wing-low s id e,a l though spray en te red the prope l le r and s t ruck the f lap , t h i s spraywas considered moderate. The photographs of figure 18 show the d i f -ference i n the spray on the two s ide s due t o heel .

Rough-water behavior.- Although no extended in ve st ig at io n i nrough water was inten ded , a few take -off s and land ing s were made i n?ves a s a qua li ta ti ve check on th e ai rp la n e' s behavior. The waves,which formed a conf'used pa tte rn , were esti ma ted by ob serve rs t o be 18t o 24 inches high and 20 t o 25 f e e t long with an accompanying ma-wind v el o ci ty of 23 miles per hour. Three lan ain gs were made, a l l onthe verge o f s t a l l . The f i r s t , made into the waves, was quite severewith a maximum recorded normal acceleration of 2.5g which occurred on thef i r s t i m p a c t . A t ime hist or y of some of th e q ua nt i t i es recorded f o r t h i sl and ing i s g iven i n f i gu re 20 . I n add i t ion , t h i s f i gu re i nd i c a t e s t hepeak posi tiv e v alues of normal ac ce ler ati on due to impact. The other twolandings, which were made parallel to the wave crests, were not quite sovi ol en t, th e maximum recorded normal acc el er at io n being 2. lg i n each caseand occurr ing on the f i r s t impact. Two successful upwid take-offs weremade i n the rough water; a time hi st or y of th e ele vat or and rudder defle c-tions and waterspeed and the corresponding peak positive values of normalaccelerat ion due to impact are shown in f ig ur e 21 f o r one of th ese tak e-o ff s . Three oth er take -o ffs had t o be abandoned because of severebouncing. Take-off at tempts nhde i n a dire ct i on pa ra l l el t o the wavecr es t s resu l ted i n espe c ia l ly la rg e motions about a l l th ree axes becauseof th e confused wave p at te rn and th e sh or t, st ee p waves. The ai rp la neta x ie d we ll upwind and downwind, al tho ugh th e nose buried a few times onthe upwind heading. Crosswind taxy ing caused th e downwind t i p f l o a t t obury. As th e s e v e ri ty of th e wind and waves was inc re as in g throughout t h ef l i g h t , t h e a i r p l ane was f i na l l y t ax i e d t o qu i e t e r wa te r f o r t he f i n a ltake-off . Inspec t ion revealed severe damage t o the l e f t t i p f l oa t ,

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moderate damage t o the r i gh t t i p f l oa t , the t a i l -whee l doors broken open,

and moderate damage t o t h e forebody bottom, si de s, and frames ju st forwardo f t h e s t e p . The dec i s ion w a s made to t e rmina te th e t e s t s of th eXP5M-1 hu l l a t t h i s p o in t.

CONCLUDING RENARKS

Hydrodynamic q u a l i t i e s e s t a b l i s h e d i n t h e f l i g h t i n v e s t i g a t i o n o fthe modified Navy ~ 4 ~ - 2i rp lan e wit h the 0.425-scale XPW-1 h u l l bottommay be summarized a s f ol lo ws :

1. The maximum up- elev ator de fl ec ti on usa bl e fo r take- off wasl im i ted by abrup t p i t c h upward a t ge taway r a t he r than by upper- l imi tporpois ing.

2. The minimum up-elev ator de fl ec ti on usa ble f o r take -off wasl i m i t e d n ea r g etaway by d i r e c t i o n a l i n s t a b i l i t y a t low t r i m s r a t h e r t h a nby lower - 1 i m i t porpoi s ng .

3. The take-off times ranged from 25 t o 45 seconds. Between humpspeed and getaway t he av erage ac ce le ra ti on was approximately 2 f e e t p ersecond per second.

4. No severe skipping on landing was encountered a t any landingtrim o r c e n t e r - o f - g r a v it y p o s i t i o n i n t h e o p e r a t i n g r an ge . There was,however, an o bje cti on ab le tendency t o tr im down and y a w immediatelya f t e r c o n t a c t . ,

5 . The r a t e of tu rn a t maneuvering speeds was low.

6. W i n g ta ke -o ff i n l i g h t winds a la rg e amount of r ig h t rudderand d if f e r e n t i a l power were req uire d a t speeds ju st beyond hump speedt o m ai n ta i n a s t r a i g h t c o u rs e.

CONFIDENTIAL


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10 CONFIDENTIAL NACA RM SLgL07a

7. Spray s t ruck t he p rope l l e r and f l a p on the wing-low s id e dur ingtake-off but was c l ea r on th e wing-high s id e.

Langley Aeronaut ical LaboratoryNational Advisory Committee for Aeronautics

Langley A i r Force Base, Va.

Norman S. LandAeronau t i ca l Resea rch Sc ien t i s t

/ ~ o h n . E l l i o t tEng ineer-Tes t P i lo t

Kenneth W . chris topheEAeronau t i ca l Resea rch Sc ien t i s t

Approved :

kJohn B . Parkinson

of Hydrodynamics Division

REFERENCES

1. Parkinson, John B. : Appr eciation and Determination of th e Hydro-dynamic Qualities of Seaplanes. NACA TN 1290, 1947.

CONFIDENTIAL


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CONFIDENTIAL

TABm I

PERTINENT DlEeENSIONS FOR MODIFIED J ~ F - 2 ITH

0. 425-SCALE XPW-1 HULL BOTTOM

General : . . . . . . . . . . . . . . . . . . . . . . . .ross load, l b 5230. . . . . . . . . . . . . . . . . .ot al tak e-o ff horsepower 400. . . . . . . . . . . . . . . . . . . .ing loading, lb/sq f t 21.4. . . . . . . . . . . . . . . .ake-off power loading, lb/hp 13.1

H u l l : . . . . . . . . . . . . . . . . . . . . . . .aximum beam, f t 4.25Length: . . . . . . . . . . . . . . . . . . . . . . . .v e r - al l , f t 36.82. . . . . . . . . . . . .orebody, bow t o s te p cen tro id , f t 16.08

. . . . . . . . .f te rb od y, s t e p c e n t r o i d t o s t e r n p o s t , f t 20.74S t e p : . . . . . . . . . . . . . . . . . . . . . . . . . .e . 6 0 - ~ ee- . . . . . . . . . . . . . . . . . . . . .epth a t k ee l, f t 0 .2 1. . . . . . . . . . . . . .ngle of forebody de ad ris e, deg 20.0

. . . . . . . . . .aximum ang le of af te rbody deadr i se , deg 44.0. . . . . .ngle between forebody and afterb od y ke els, deg 8.0. . . . . . . . . . . . . . . . . . .t e r n p o st a n g l e, d e g . 8 ,5 8Wing :

. . . . . . . . . . . .p an , f tArea, s q f t . . . . . . . . . .. . . . . . . . .oot chord, f tRoot sect ion, NACA . . . . . . .

. . . . . . . . .ip chord , f tTi p s e c t i o n , NACA . . . . . . .Mean aerodynamic chord (M .A .C . ,Tncidence t o forebody kee l, degFlaps :

Semispan, f t . . . . . . . . .Ares, sq ft . . . . . . . . . .Average chord, percent M.A .C .T y p e . . . . . . . . . . . . .Maximum deflection, deg . . .

. . . . . . . . . . . . . . . 11.7. . . . . . . . . . . . . . . 31.2

. . . . . . . . . . . . . . . 25.8S l o t t e d. . . . . . . . . . . . .

. . . . . . . . . . . . . . . +o.H o r iz o n ta l t a i l s u r fa c es :. . . . . . . . . . . . . . . . . . . . . . . . .r e a , s q f t 45-4

. . . . . . . . . . . . . . . . . . . . . . . .p z n , f t . . . 1 3 . 7 5. . . . . . . . . . . . .ean aerodynamic chord (M.A.C . , t 3 -7

CONFIDENTIAL


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CONFIDENTIAL

TABLE I - ConcludedPERTINENT DIMENSIONS FOR MODIFIED ~ 4 ~ - 2 I T H

0 . 4 2 5 - S c m XPW-1 HULL BOTTOM

R a t i o o f e l e v a t o r a r e a 'to t o t a lh o r i z o n t a l t a i l a r e a . . . . . . . . . . . . . . . . . . . 0.43

St ab i l i ze r inc idence to fo rebody kee l , deg . . . . . . . . . . 2Ta i l l e n g t h ( 2 5 p e r c e n t M.A.C. of wing t o 25 per cen t

M.A.C. of hor izon ta l t a i l ) , f t . . . . . . . . . . . . . . 16.0Ve r t i c a l t a i l s u r f a c e s :. . . . . . . . . . . . . . . . . . . . . . . . .rea, s q f t 30.3. . . . . . . . . . . . . . . . . . . . . . . . . . .pan, f t 6.5

Mean aerodynamic chord (M.A.C . , t . . . . . . . . . . . . . 4.9R a ti o of r ud de r a r e a t o t o t a l v e r t i c a l t a i l a r e a . . . . . . . 0.43Ta i l l e n g t h ( 2 5 p e r c e n t M.A.C. of wing to 25 per cen t

. . . . . . . . . . . . . . ..A.C. o f v e r t i c a l t a i l ) , f t 15.3P r o p e l l e r s :

N u m b e r . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Number of blades . . . . . . . . . . . . . . . . . . . . . . . 2. . . . . . . . . . . . . . . . . . . . . . . . .iamete r, f t 7 .12Distance of bottom of p ro pe lle r a r c above forebody. . . . . . . . . . . . . . . . . . .e e l a t main s te p , f t 4.10Distance of bottom of pro pe lle r a r c forward of s te p

cen t ro id measured p a ra l l e l t o fo rebody kee l , f t . . . . . . 6.32. . . . . . . .h r u s t a x i s i n c l i n a t i o n t o f or eb od y k e e l , deg 6.5Wing- t ip f loa t s :

S ~ b m e r g e d d i s p l a c e m e n t ~ l b . . . . . . . . . . . . . . . . . 405. . . . . . . . . . . . . .i s ta n c e from h u l l c e n t e r l i n e , f t 14.4Angle of he el t o submerge, deg . . . . . . . . . . . . . . . . 10.0

v

CONFIDENTIAL


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CON FI DENTlAL

TABLE I1

TABULATION OF PILOTS' COMMENTS ON HYDRODYNAMIC QUALITIES OF

MODIFIED ~ 4 ~ - 2 ITH 0 . SCALE XP5M-1 HULL BOTTOM

Take-off longitudinals t a b i l i t y a nd c o n t r o l

Land ing s t ab i l i t y and con t ro l

L a t e r a l s t a b i x i t y a nd c o n t r o l No comment

Take-off time and dis tan ce

Over-all rating on hydro- F a i r t o p oo r


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;

CON FI DENTIAL

.,

L-57645

Figure 2 . - Three- quar te r front view of J4F-2 with O.425 -scale XP5M-l h u l l bottom an d standard J4F-2.CON FI DENTIAL


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CONFIDENTIAL

JEST CC

T

CON Fl DENTlAL

Figure 3.- Three-view dralring of ~ 4 ~ - 2ith XP5M-1 hull bottom.


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FUSELAGESTA T/ON

INCH3 At- 7OF BOW

CONFIDENTIAL7 /9iT8/

0 17 38 6638 96.01 /2Q.U/ 419.56

I!_--'

'

mr 25 /09339r 44LM

STEP- -- --p ------ -- -1

It/

SPL /CL NE

BAS' LINE ---/I

Figure 4.- Hull l i n e s o f 0.425-scale W 5 M - 1 bottom as f i t t e d t o m od if ie d 34~-2.


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CONFIDENTIAL

Water-speed p i t o t tube

CONFIDENTIAL

Figure 5. - Locat ion of instruments i n fuselage of ~ 4 ~ ~ 2i th XP5M-1 h u l l bottom.


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Speed, f p s A Upper l i m i t ,Q increasing trin%

(a) Flap deflection, 0 0 ower limit>

CONFIDENTIAL Speed, fps

(b) Flap deflection, a',Figure 6.- Trim l i m i t s of s t a b i l i t y ,


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CONFIDENTIAL

take-of f s

l eva tor se t t ing fo rt r i m i n air

o w t r i m ; tendencyt o yaw

0 2D 40 60 80 100hCONFIDENTIAL Speed, fp s

Figure 8.- Limits of usable e lev ato r def lec tio n throughout the speed range. Center of gravi,ty,25 perc ent mean aerodynamic chord; fl a p defl ec tio n, 0.


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8 4 0 -4 -8 -12 -16 -P -2 4Elevator def le e t on, deg(a) Flap deflection, 0 C o g . ,

6

4

2

012 8 4 0 -4 -% -12 =16 =ZI -a

- - u -

Elevator deflection, deg

(b) Flap deflection,.ZIo.

percent M.0 a3

Figure 9. - Maximum amplitude of porpoising during take-off.


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- - CONFIDENTIAL

(b) Flap deflection, 2

Figure 10.- Minimum t r i m encou ntered beyond hump speed duringtake-off runs.


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c *8 ,percent M.A.

0 P0 %

0 '30


(a) Flap deflect ion, 0


(b) Flap deflection, 23.

Figure 11.- Angular ve loc i t i e s occur r ing immedia te ly a f t e r ge taway.


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- - MODERATEfairly quick upward pitch

sharp upward pitch

8

Figure 12.- Pi lo tt 8 omments on pitch upward at take-off.


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NACA RM SL9LO7a

Take-off s t a b i l i t y

A Porpoisin@;limits

0. Center of gravity, percen t M o A o C e 0 LOW trims at@t) o high speedsa,

I=+(a) Flap d e f l e c t i o n , 0 .

QAbrupt pi tch atgetaway

r] Airbornes e t t i n g

(b) Flap d e f l e c t i o n ,

Figure 13. - Summary of take-o ff s ta b il it y ,


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3CONFIDENTIAL

2

1

m

Trim at contact , deg

(a ) Flap def lect ion , 0.

CONFIDENTIAL Trim a t contact , deg(b) Flap def lect ion, 23'.

c.g., percent M.A.C.0 a

Figure 14.- Number of ekipe on landings i n emooth water.


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NACA RM SL9L07a

Figure 15.- Ty p i c a l t i m e h i s t o r y o f a landing i n smooth water.


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NACA RM SLgL07a

CONFIDENTIAL

0 ight t u n aLeft turns

Rpm of aiding engineCON Fl DENTIAL

0Figure 16.- Time t o complete 360 t u r n s a t l o w water speeds.


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GONFl DENTIALO Hunp speed

High speedk(P

Figure 17.- Number of ta ke -of fs a t which various rudder de fl ec tio ns were used a t a speed jus t beyondhump and a speed near getaway.


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I I

. .

I e

NA CA RM SL 9L0 7 aCONFIDENTIAL

(a) Wing-hig h s id e; center o f gravi ty, 25 percent M.A. C .

~


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NACA RM SLgL07a

CONFIDENTIAL

Fig ure 20.- Time h is to ry of a rough-water landing . Center of g r a v i t y,25 per cen t meen aerodynamic chord; f l a p de fl ec ti on , 20'.


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NACA R M SLgL07a

fJ4

.@4 2 2g2

"

g"o8 o

CONFIDENTIAL Time, sec

Figu re 21.- Time hi st o ry of a rough-water take-off. Center of gravi ty,25 pe rc en t mean aerodynamic chord; f l a p de fl ec ti o n , 20'.


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, ..

NACA RM SL9L07a CONFIDENTIAL

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

RESEARCH MEMORANDUM

fo r the

Bureau of Aeronaut ics , Department of the Navy

FULL-SCALE HYDRODYNAMIC EVALUATION OF A

MODIFIED NAVY J4F-2 AMPHIBIAN WITH A

O.425-SCALE XP5M-l HULL BOTTOM

TED NO. NACA DE325

By Norman S. Land, John M. E l l i o t t ,and Kenneth W. Chris topher

SUMMARY

An inves t iga t ion was made to evaluate the hydrodynamic qual i t ies ofa ~ . 4 2 5 - s c a l emodel of the Navy XP5M-l hu l l , which was i n s t a l l ed on amodified Navy J4F-2 amphibian. Longitudinal and d i r ec t i ona l s t a b i l i t yduring t ake-off and l a nding, low-speed maneuver a b i l i t y , spray charact e r i s t i c s , and t ake-off performance were inves t iga ted . The behavior o fthe a i rp lane in moderately rough water was a l so observed. The opinionsof three p i l o t s have been cor re la ted with the data .

INTRODUCTION

An eva lua t ion , us ing a f ly ing t e s t vehic le , of the hydrodynamiccha rac t e r i s t i c s of two experimental types of hu l l bottom was requestedof the NACA by the Bureau of Aeronaut ics , Department of the Navy. ANavy J4F-2 amphibi a n was chosen as the vehicle s ince i t ~ s the smal les t

multiengine a i rp lane r ead i l y ava i l a b le . The a i rp lane (BuAero. No. 32976)~ s furnished ~ > -t h e B ~ e a uof Aeronautics and modified by the Edo Ai rc r a f t Corporation so t ha t an y of severa l hu l l bottoms could be i n s t a l l e d .This paper d e s c r i~ e s the t e s t s and presen ts the r e su l t s obtained from af l i g h t i nve s t i ga t i on o f the hydrodynamic cha rac t e r i s t i c s o f the J4F-2with a O.425-scale bottom of the Navy XP5M-l flying boat. The investiga


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I , .0 .

.I*

ma*ae

me.0 0

m .

CONFIDENTIAL NACA RM SLgL07a

bump, it was necessa ry, i n l i g h t winds, t o use a l a rg e amount o f r ig h t

rudder and d i f fe re n t i a l power. I n s t rong winds, no d i f fe re n t i a l powerwas requ ired and le s s rudder d ef le ct io n was needed. A t high speeds,a few degrees of rudder were suff ic ient . On s e v e r a l t a k e- o f f s, thep i l o t n o te d a s t r o n g t en de nc y t o w a te rl oo p a t h i g h s p ee ds an d a t t r i m sbelow 2O.

One p i l o t r a t e d t h e d i r e c t i o n a l s t a b i l i t y an d c o n t r o l f a i r , oner a t e d them poor, and the t h i rd had no comment.

Spray cha ra c t e r i s t i c s , - Two typ ic a l sp ray photographs a re p resen tedi n f i g u r e 1 8. Such photographs have been aml yz ed and th e r e s u l ts a r egiven i n f ig ur e 19. The curves shown a r e drawn through th e poi nt srepr esen t ing the peaks of bow spray b l i s t e r s s t the va r ious speeds . A tlow sp ee ds , t h e p i l o t h ad no l a t e r a l c o n t r o l a nd t h e a i r p l a n e h e e le d s oth a t one o r the o th e r o f the wing- tip f l o a t s was i n the wa te r. On t h ewing-high s ide no sp ray en te red the p r ope l l e r. On th e wing-low si d e ,a l t h ou g h s p ra y e n t e r e d t h e p r o p e l l e r a n d s t r u c k t h e f l a p , t h i s s p r a ywas consid ered moderate. The photographs of fi gu re 18 show the dif-fe rence i n the sp ray on the two s i de s due t o hee l .

Rough-water behav ior.- Although no extended inv es ti g at io n i nrough water was intended, a few tak e-o ffs and landin gs were made i nyaves a s a q u a l i t a t i v e c h e c k o n t h e a i r p l a n e ' s b e h a v i o r. The waves,which formed a confused pat t ern , were es t imated by observ ers t o be 18t o 24 in ches hig h and 20 t o 25 f e e t long w ith an accompanying maximumwind ve lo ci ty of 23 miles per hour. Three land ing s were made, a l l onthe verge of s t a l l . The f i r s t , made in t o th e waves, was qu it e sever e

w i t h a maximum reco rde d normal ac ce le ra ti o n of 2.5g which occu rred ont h e f i r s t i mp act. A t im e h i s t o r y o f t h i s la n d i n g i s g iv e n i n f i g u r e 2 0.The othe r two landing s, which were made pa ra l l e l t o th e mv e c re s t s ,were not q u it e so vi ol en t, th e maximum record ed normal ac ce le ra ti onb e i n g 2 . l g i n ea ch c a se a nd o c cu r r in g on t h e f i r s t i m pa ct . Two su cc es sf u lupwind tak e-o ffs were made i n the rough water; a t ime h is to ry of one i sshown i n f ig u re 21. Three ~ t h e r ak e-o ffs had t o be abandoned becauseof severe bouncing. Take-off a t tem pts made in a di re ct io n p a r a l le l t ot h e wave c r e s t s r e s u l t e d i n e s p e c i a l l y l a r g e n o t io n s a bo u t a l l t h r e e

axes because of th e confused wave pa t t er n and the sh ort , steep waves.The air pl an e t ax ie d well upwind and downwind, althou gh t he nose b ur ieda few tim es on th e upwind head ing. Crosswind tax yi ng caused th e down-wind t i p f l o a t t o b ury. A s th e se v er it y of th e wind and wsves wasi n c r e a s i n g t h r o u g h o u t t h e f l i g h t , t h e a i r p l a n e was f i n a l l y t a x i e d t oq u i e t e r wa te r f o r t h e f i n a l t a k e - o ff . Inspection revealed severe damaget o t h e l e f t t i p f l o n t , moclerate damage t o t h e r i g h t t i p f l o a t , t h e t a i l -wheel d oors broken open, and moderate darwge t o t he forebody bottom,sid es , and frames ju s t forward of the s tep . The decision was made t o

t e r m i n a t e t h e t e s t s of the XP5M-1 h u l l a t t h i s po i n t .

CONFIDENTIAL


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NACA RM SL9L07a

CONCLUDING REMARKS

Hydrodynamic q u a l i t i e s e s t a b l i s h e d i n t h e f l i g h t i n v e s t i g a t i o n oft he mod if ied Navy ~ 4 ~ - 2 ir pl an e wi th t h e 0 .425-scale XP5M-1 h u l l bat tommay be summarized a s fo ll ow s:

1. The maximum up-e leva tor de f l ec t i on usabl e f o r take -off wasl i m i t e d by a b r u p t p i t c h u pward a t g e ta wa y r a t h e r t h a n by u p p e r- l im 5 tporpo i s ing .

2 . The minimum up-e leva tor de f l ec t i on usa ble f o r take-o ff wasl i m i t e d ne ar getaway by d i r e c t i o n a l i n s t a b i l i t y a t low t r im s r a t h e r t b nby lower- l imi t po rpo i s ing .

3 . The tak e-off t imes range d from 25 t o 45 seconds . Between humpspeed and getaway the ave rage acc e l e r a t io n was approx ima te ly 2 f e e t pe rsecond per second.

4. No s e v e r e s k i p p i n g on l a n d i n g was e n c o u n t e re d a t a n y l a n d i n gt r i m o r c e n t e r - of - g r a v it y p o s i t i o n i n t h e o p e r a t i n g r an ge . There was,however, an objection;3ble t endency t o trim down and yaw immediatelya f t e r c o n ta c t.

5 . The r a t e of tu rn a t maneuvering speeds was low.

6. D uri ng t a k e -o f f i n l i g h t win ds a l a rg e amount of r ig h t rudde rand d i ff e r e n t i a l power were r eq u i r ed a t speeds ju s t beyond hump speedt o m a in t a in a s t r a i g h t c ou rs e.

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