[1]portion of a beam @on the line XIV-XIV of Fig. 13, looldng in the direction indicated by the arrow; Fig. 15 is -a vertical sectio'naaken o'n the -line XV-XV of FiLy. 2; Fig..Iq'is a seciioi@ta@ei@on the line XVI of Fig 2 - Fig. 17 is a sectioii taken on the line XVII of Fig. 2; 10 Fig. 18 is a section tak@n on, the line XVIII of Fig. 1; Fig.19isa,seefiontakenontheEneXIX of Fig. 5, looking in tl@e direction indicatow; ed by the arr . 15. Fig. 20 is, a section on the line XX, of Fig. 5 - Fig. 1 21 is a section on the line-XXI of Fig. 1; Fig. 22 is a sectionon the line XXII of 20 of Fig. 1, looking in the direction indicated .by the arrow; Fig. 23 is a section 6n the lin6 XXIIIXXIII of Figs. 1 and 11; first and foremost consideratlbn, an ap@roximation to a stream line wing s6etion at I small aligle of incidence, varying from Oc' to 2' is necessary. . Further, it is essential that the position of the center of pressure 70 for the-@ fastest flying angle shall be quite stable, and witha margiii of safety in case of unforseen eircums@tances causing a further dectease, of angle of incidejace. Foi slow flying, a wing. . section characterized by 75 good upper and lower stirface cambers and compar'atively largf3 :angles of incidence, is necessary. Further, it- is essential that the angle of 'iiicid6nce for sloi@ flvinlr ghall not be too near to the critical a@'n--I@ @t which 80 the lift co-;efficient decreases @nd t@e drift ilierease@s, and that at the maximum angfe of incidence the center of pressure shall have a stable position. @'or,a good speed range, a wiiag sectioii 85 sbould have, the -following qualities: The c6nter of pre8sure for the range of flying angl'es iised should bave, a- stable,;poFig. 24 is ft section on the line XXIV of@- sition and the, minimum range of movement 25 Figs. 2 and 7, looking in the direction indi- al6ng the chord. Iii a aood wing section, 1)0 6ated by the arrows,;, the center of pressui-e @Call angles of inei7 ]Fig. 25 is A section on the line XXV@L dence used in flying, ascending or a,li@hting XXV of Fig. 1; should lie bet-kveen 30@lo' and 457o: of the Fig. 26 -is a section on the'line XXVI of chord -to the rear of the leading edge. 30 F 2; The lilt 'co-efficien't sliould increase con- 95 .i@ig. 27 is a sectionon th6 line XXVIItinuouslv fr(?m it negative or zero an le to 9 XXVIII of Fig. 6 - about 15c. and it srofild theia remain conFig. 28 is a s6etion on the line XXVIII stant and decrease at a -slow rate withoat of Fig. 2; 35 Fig. is a -section on the line, XXIX of Fig. 2, looking in the direction indicated by the arrow; Fig. 30 is a section on t@e line XXX@'. XXX of Fig. 5 @40 -Fig. 31 is a. section on the.line XXXIXXXI of Fig. 6; a-nd Fig. 32 is, a fragmentary elevatio@ of a, portion of the lower irhoid member. it is:well kn6wh tha@t the wing curvature 45 is a determining fa@tor in the efficiency of @n aerofoil. An aerofoil of low camber having a relatively low lift has bee'n found to have hi . gh efficiency at small'an les @of inei-: dence and at high speeds, alid th6 area at 50 Sul3h speeds may be made ver@ small.' I-Iowever it is essential that the spoed at the time, .of landing shall not be so great as to endanger the safety of the pilot or of the airplane. @Th6 most effic.ient Wing section for low 55 speeds lis not the most 6Aicient s eti'n for 0 high speeds. 'Generally speakino,, a high% speed type@ of machine requires a totally. different wing section and incidence to a loW or'moderate 60 s@eed type. The 4etual wilig sections of airp anes have - hith@kto been a kin4 of compromis@'e hetw6en fast and slow speed sections having 'a @harp critical aiagle,, The maximum lift co-efficiejit should not be lower than 0.65, and' the maxi'muni drift co-efficient ought not to,eiceed 0.@o. At the small- angles of incidence used with th6 hig@est speeds, the drift co-efficient should be a' minimum, and fo@.the minidaum expen- 105 @diture of horse 'power at the ' ' ipaximum speed, ihe lift co-efficient at the n@inimum value of the drift -coeffici6nt should be sufflcieiit for the wing area choseii to support the 16ad@@at that speed. 110 Two methods of improving- the performance of an airplane have.beensuggested, but have hitherto iaot been pui into common use because of the, mechanical difficulties involved. One niethod -is to increase. the wing i 15 area just before landing. 'Thib other is to, inctea8e the lift co'-effi@i6n@ when landing. The aerofoil inustrated herewith has a st@ucture -permitting the simultaneous pro-' jectioli of front and r6ar movable portiolis 12() to increase the area, each of the movable portions following a curved path, and each, as. the result of it8 movement, causing the met-al pl'ates constittifing the.low6r stirface of the a6rofoil to bend in such manner that the section of fhe,aerdfoil is changed from one of low camber when these portions are closed in order -to fiisure safe litud.iiag apd " gettiag to one of deep camber when the movable o:ff. portions iir6 fuR@ opened. Furthermore, Where the greatest@maximum spqed is the-- ihe rate of projection 'of the re@r movdble - - 13V
[2]1,540,105 trailing p6rtion is greater than that of the f@ont or nose portion, and the curved path of movement is such that when the mov@ble portions are fully pi@ojected, not only are '5 the. area and e'amber altered, but the a:ngle of incidence is also increased, -whereby the ' fuselage m@y b6 maintained in a position in ivhicl@ it offers a minimum resistance and wherein the propeller has its axis -na-in10 tained substantially p:irallel to the Iii-@e of i'light, this being.iis position of maxii-num efficie@ncy. The position of the maximiim ordinate of a-ii aerofoi'L is ali important factor in deter15 mining the location of the @enter of prbssiipe. The relative inove'ment of the front ancl rear movable portions. for aiiy given relation that n@ay exist bet-,@een the secti6ns ol the aerofoil in its fully@ closed and in its 20 f ully opened positions, will be determiiied in such maniier that during the char@ge in positir,-,l of the movable parts the maximu I m ordinate will mov e slilyhtlv to the rear with respect to the fixea p@rtijn of the aerofoil. 25 Moveniont bf the maxiraum ordinate to the rear will ii'ormally cause rearward @moyement of the center of pre@sure. Conversoly, increase in the angle of incidence will norrhally cause fo-rward movernent of the cen30 ter of pressure. The variation in the -win 9 section diiring opening movenient of the nose a-Lid trailing portions produces rearward movemeiit of the iiiaximum ordidate which tends to move the center of pressure .35 to the rear. The higher rate of niovement of the trailing portion causes an inerease,in the angle of incidence of the a-erofoil which tends to mlove ihe center of pressure forward. These two. factors counterbalance 40 e,,tch ot4er. Either forward movement of the front movable portion or redrward m'ovement of the trailing portioh of the wing would cause a move@-nent of the center of pressure, @ut 45 by causing the relati-@e movement of pro @oth to occuf simritraneously, the effect of one may be mado to balance that of the other and tb-e center of pkessure will thus remain at sub@tantially the same pla6e. r)o @ Slio-ht movement cif the maximum ordinate to the rear increases the lift co-effici6nt at higher angles of iiacide-nee and at. the ounteracts the '@rd movesame time c forw ment of the center of pres ure due to in55 crease in the angle of incidence. The lift may be increased by an increase in:area, by an inere:ise in the an-ale of incidence, and by an alteration of s@ection. As the nose and trailing portions are pro60 jected in the aerofoil of the present invensimul_ I tion, th6 lift is increased by the taneous action of each of these three factors. Lateriil coiatrol'of -an airplan6 may be ob-tailied by varyiiig the relative lift upon the 65 p'anels bn opposite'sicles of the fusel@gqthis varia tion being prodiieed in the preseni aerofoil by varyiiig the relative amount of projecti on of fhe movable portions. In my cc,-pending application, Serial No. 60- i,5"8, file,d De6. 18, 19221 I have described 70 a control n-iechanism for Iccomplishincr thi's va'ri ation in area of th6 aerofoil panels, Th e ,ierofoil illustrated in the accompaiiyiiig (Irawings is constructed entirely of meta l, the beams a-nd ribs being preferably 75 niade of alloy steel members secu,red too,ether by electric spot welding, while the shee t metal plates coverino, the s'urfqces will pref erably be of aluminum or of light metallic alloys. 80 In Fig,. 1, the main beams or-spars are sho wn with the spar 1 located near thc, froni edge of the fixed portion of the aerofoil, the@ spar 2 opposite the center of pressure and the spar 3 near the rear of the 85 fixed portion. These spars consist of aii upper plate 4, a lower plate 5 and side plateF3 6 and 7, the plates 4 and 5 bei@g preferably forme d with flolnges 8 as shown in Fig. 135 secur ed by spot welding td the side plates 90 6 and 7. The side plates 6 and 7 will pi-eferably be' stamped 6iit to form @ diagonal brace members 9, flanges IO.being formed aroun d the stamped c)ut portiom to provide rigidit y. Sheet steel ribs 11 and 12 are se- 1)5 cured to the.upper and lower edges respectively pf the spars 1, 2 aiid 3, these ribs being m the form of channels adapted to re . ceive the edg6s of the sheet metal plates 13 ancl 14 forming the covering 6f the upper 100 and lower surfaces of thb aerofoil. T he ribs 11 and 12 are secured.to the spars as indicated most clearl@ in Fig. 14. Each rib is provided with a central flange 15 forme d by bending the'sheet metal upon 105 itself. to project outwardly, At right angles to the bod-Y o:f the rib. Opposite the plate 5 this flange 15 of the, rib is cut away to permit the body of the rib to he closely in coniact with the face of the plate 5 on opposite, 110 sides of the strengthening corrugation 16. Brate members 17 shown in Fig. 14 are prefe'i.@a bly formed of thin sheet steel folded upo;i itself to provide parallel members 18, 19, separated along one edge io embrace op- 115 posite sides of the, flange 15 and flanged along the other edge. at 20 to abut against the plates 6 and 7 and th6 flanges 8, the folded edge fo I rming the hypothenuse 'of each triangula r biace member. The flanges 20 will 120 be secured by spot w.elding -to the plates 6 and 7 and to the fla-nges 8', and the edge poftions 18 and 19 wili be spot welded to the flange 15. Tubular drawn steel br'aces 21 have the.ir ends flattened and separat,6d to 125 eneag -e upon, opposite faees of, the brace mi'm.- er 17, the ends:' of the members 21 being shaped to fit e'osely Y@ithin the corners formed by the ange@ 20 @nd the. bodv of the rib, 12. The overlapi@i;ng@ flattene@l
[3]ends of the braces'21 will also be spot curve of the rib 11. The rear portions of @,%velded to the brace. m6mber 17. Between the plite'S,6 and'.7 at the point at which the braces 17 eno-,a(-Ye the outer ,5 faces of the Pla.tes. is. located an interior brace member 22 liavin- flanges 23 8velded to the inner face df th@'plates 6 axid 7 ai@d having a flaiio 24 formed along its. tipp@er edge to provide additional -rigidity. This 10 plate may be perforat4ed for the salce of lightness. The braces 21 extend di@gonojly from the lower sides of the"'spats 1, 2 and 3 upward to engage tbe'flange 15 upon the lower I sur15 face of the u per rib 11 b6tween t4 p e spars. As s@own in.Fiol,. -11, between the adj,acent' ends of tile braces ql wbere they lie in contact with tho hange 15 is tfi@ gattened end of the, tubular brace 25 which extends be20 tween the ribs 11 aiad 12, 'at,.substantially right dn es to eac@. the flatoned ends of . 91 the braces 21 and 25 sho-wn in Fig. 11 are secured by spot welding. to. th@6 flange 1 5. At the forward edcre of the aerofoil, 8heet 25 metal members. 26 @nd @7 are secured. -t@ the leading spar 1 as.indicated in Fig. 6. These sheet metal m ' embers are sy' inmetrical 'in construction -and arra-nged parallel with, ea@h other to form it chaniiel. iiadic@@ted in 30 seetion in Figs. 22 and 31. , The she@t metal .is teni as indicawd at 28, 29 to form upper and low'er ciir-yed tracks connected by side walls 30. Abov'e find b@low the tracks, the -bers 26 and 2 wee. sheet metal mem 7 as 35 shown in Figs. 6 and 22 towar'd the rear end of the structure, but ioward the front end, the plates arb'separated above as indi-' -tbe inember 34 and the both rib 11 are iher'i8- fore modified to the confivation shown in Fig. 17 in wliieh it will noted that, the n-ieinber 11 no longer h-as the fl,,tbg@ 15, and 70 the member 34 ha the, portions above and. below tlie- s.ide walls 39 cut awav so that the upper -inner faces of ilie ido walls 39 lie on opposite sides of @ the rib 11 and are spot welded thereto. The- rear portion of the 75 rib 42 which extends along the upper surface of -the tr@iling poirtion of the aerofoil is shown' in cross section in, Fig. 24 at a - poiiit irnm'6diately at -the rear oi the re'ar onsisting Qf -a 80 elid of. a bra@ce niember 49 c steel tube flat-tened at both ends and secured by- spot,weldiiig to ihe und6'rside of the rib 42 ancl to the Lipper side Qf the rib,41 whic ii6s along. the lower-'side o.f the trailing por,@ @ iiaeml r 45 85 tion bf the aerofoil. , A brace, extends from a. point. he'ar tiie front end of the brace 4,3 ftnd t-he'rib 44 to the forward end pf the rib '42 at the @ pgint where the roller 40 is journal@d. A cross brace 46 exterids between the rib 42 and the brace mem-, 90 :ber 45 'the iipper end of the brace 46 connecting with the rib 49, at ' the point where the roller 41 is j6urnaled. Anoth'er brace memb@r'47 extends'between the rib 42. and thp, rib 44 sub@tantially at right angles to 95 the'rib 42 its'lower end being secured by spot welding to. the brace 46. A, brace 48 li6s betwe@en the upper end 6f the brace 47, and the..Io - wer end of the brace 46 the up' per eiid being secured to ihe rib 42 and the. 100 io,@er @end to the brace 45. As shown in Fig. 7,@ the rollers 40 and '41 lie bet-ween the, c'ated in Fig. 31 and b@lo 'w as indicated in tracks 37 and 38., The portion 6f the rib 42 Fi@. 27 to perfnit the passage of the rib lyiiig to the rear of the uppe r elid of the .,40 memli6r 31 secure'd to flie movable nose. por- b@aci 47 is cu'rved on an are 6f a eirele'con105 tion of. the aerofoil.' This rib,@nem@ber is' 6entr'ic wiih the @curvatur'e, of thd tracks 37, compo@ed'of sheet metal plates having their 38, but having @, sligbtly smaller radius and front edges of the contour de@-ired 'for the the portion of the rib 42 between the upper f6rward edie of th6 movable nose @oriio4 ends of the - braces 46' and 47 lies at some45' of the aerofoil and the centr@l p6rtion is -what of an angle to the portion of th@ rib 110 formed as a rearwardly pr6j6cting bearin 42 between the rollers 40 and 41 so that as 9 bracket 32 upon whic,4 are journ'aled rollers the rollers 40 aiid 41 run along the tracks ;/-'33 haviiig, gr - 37 a' 38 in th - a of a circle, the upper poved periphories adapted ' to nd e re enzage the trackg formed by the folds of surface. of the rib 42 wi,li move along a consh@6i metal at 28 and 29. centric' circle and therefore, will not move 115 In Figs. .7 and '21, is illustrated a rear away from the extrem6 rear end of the sheei metal ttack @nember 34 secured to the lower; @urface 6f @ the iib 11. The forward trailing, spar 3 aiid to the u.pper rib ii., end of t'he iib 42 lyiiig between the roller@s This member 34 consis@s of @@ymmetrically 40 and 41 is compressed ii@to the configur,,isbaped parts '35,@:36, loont at @7 and @8'io tion shown in section'in Fig. 17. 120 fon-n upper and low6r. tracks, connected by with,which enlr side walls. 39, age &oov6d rollers 40 and 41 secured to a -rib,4@ constituting part of the - trailing porti6n of the 60 aerofoil. At its. forward eiid, the.meinber 3,t has the upper @edges 6f its par-ts 35 and, 36 spot welded--tck@@ihe flange 15 of the rib 11, but the channel lying between'th@ and lo-w6r tra6ks and the. walls 39 is The e.-Areme -forward end of the side walls 39 are spot welde d on opposite sides of th6 bra6e -member 25 which extends between the ribs 11 and 12 substantially midwE[y between the spats 2 and 3. A@ brac6 49 125 similar to t'b,e brace 21, but sho,rterl, extends between@ th rib 11 an4 the upper ed gb o.f the plates 35 and 36, the upper end of th@ brace bei flattenecl and overlapping" the =d o'n an are of a, circle interse@tin the flange 15.Wr the manner indicated in F' 130 . 1 9 -
[4]1,540,105 11, while the lower end is tl,3o flatte'ned to 6verlap the upper edges of th@ plates 35 and 36. A brace membe'r 50 consisting of two cliannel sbaped plates sliowii in'section in Fig. 28' extends be,,tiveen the lower edge of the side walls 39 and the brace 17 at the lower edge of the forward face of the @trailing spa,r 3, the upper ell(I of the plates 50 being secured on the otit6r faces of the wall-, 10 39 at a point opposite the lower end of the br,tee 49. The brace 51 exteiids , Lipv@ard from the upper edge 'of the plates 35, 36 adjacent to the lower end of the braco, 49 to the brace 117 which in ttirn is s@eiired to tlie. I rib 11 and the ulipei, p(rtion of the forwara face of the t-railing spar 3. Between th@ brace plate'17 at the lower edae of th6 spar 3'and the loweiend of the brace member 25 t6 which tli6 forward end 6f the walls 39 2( arc-@, secured @extends a brace iiiember 52 shown in closs section in Figs. 25 and 26. This brae6 member 52 is made of a slieet of steel.folded centrauy in the shape of -a, tube along its iipper.edge, tlle froe edges 53, 54, 25 being s6parated and the portion betweeii the free separated edges and the tubular portion being s6cured toc,,ether bv welding. At its forward end, the free edges 53 and 54 em30 sur@ace of the rib 12' and ihay be secured ihereto bl@ spot welding adjacent to the lower ei-i(f of the brace 2.,5. To the re,,tr- of this forw,,ird end, howevei@, the flange 15 is not seci ' ired to th@ free ed,-e, portions 53 a-nd 35 54, biit, the rib ii-lay be bent downwar.d so tli,,tt the flai-ige 1,5 will be partly withdrawn froin tl-le channel bet-,ieen thf, free e.d,-eq 5i') and .54 -,is indicated in'Fi(-Y@ 26. The inethod of securina the slieet i-iietal 40 plites 13 to the ribs 11 is indicat@,d iii ]Figs. 17 and 21. As most clearly seen in Fig. 21. the free edges of the sheet steel coiistitui@ing ilie cliannel portioii of the rib 11 extend inw@rd 45 toward each other in t-he same plane and are t'hen bent at substantially right angles to t'hat pla@-ne'iiiward toward the cehter of the channel to form flanges 55.,, The sheet metal Plates forming the coveriiig of the aerofo,.l 50 have their ed-es bent angulaerly into a hooked. sliape adapted to engage- with the flanges 55 as the edge of the. plate is @,slid longitudinally of the channel from one end of the rib 11. After boti-L plates have been 55. plaoed within the channel a formiii- to , ol 1 t@ will be drawn'longitudinally of the channel to pless the free ed-es of the sheet@ 13. into the inner coriier formed by the flanges 55 60 With the outer faces of the, rib 11 as indicated at 56. The tool is withdrawn and a tocking strip 5@ preferably of alumiiium or of a light alloy will be drawii into the 'Mierior of the channel to hold the of "the sheets 13 securely locked 65 flange@ 55 ft,5 -,hown iii Fig, 17, It will be observed that the rib 11 has the flange 15 in certain locations as shown in Figs. 11, 21 and 23, while in other locations the flange 15 is omitted as indicated in Fig. 17, but this does not,-- affect the manner of connecting 70' the plates 13 to the ribs and the loeking strip, 57 is -of the same @configuration in every case. The locking strip 57 will preferably be drawn through a die so that its cross section will be uniform'throughout its length, 75 thus enabling it to be readily drawn into the channel after the tool has pressed the edges of the sheet's into position. The strip 57 engages-,the surface of each sheet 13 within the corners formed ,it 56 80 thus preventing spreading of the ebannel. The outer arms of the T-shaped sti-ip 57 lie on opposite sides of the two inwardly extending flanges 55 with the infolded edges of the plates 13 surrounding the flanges and 85 held firmly and uniformly at all points tliroughout their length. This gi@es much greater rigidity and is a miieh stronger construction than is secured by, the u e of rivets at a series of separat.ed 90 poiiats alcing a'n ed of a plate. For the sake oflelearness, thd locking strip 57 lias been omitted from the illustraThe ribs 12 of the under surface of the 95 fixed se"etion of the aerofoil are provided with a flange 15 froin their forward ends a diacent to the leading spjr 1 rearward to .t point indicated at 58 in- Fig@s. 2 and 32. Flange 15, as has been stated-, is seciired to 100 the br,,Lce 52 by w,,PIding adjaceiit to the lower end of tl-te br:ice 25.- From this pointto the poiiit 58, the ll,,inge gradually tapers iintil it mer(,Yes witb the flat upper siirface of the rib, tlie, rib frorti I that point'to the 105 rear havi-ng a cross section similar to that sho'wn in Fig. 17. At the forward end of ihe ribs 12 upon the lower surface of the fix@d portion of the aeofoil, the channel member is compressed to form a flat verti- 110 cil web- indicated at 59 i.n Fig. 12, this flattened poi-tion terminating at the leading spar 1. A brace member 60 similar in configuiation to the brace member 1'( has its forward @fl,,inges welded to the side plate 6 115 of the spar-1, its lower edges embracing opposite sides of the web 59 and being weided thereto. The brace member 21 has its lower end fl,,ittened to form parallel lugs engaging on opposite sides of the brace member -60 120 - which are welded thereto. The rear ends of the sheet metal members 26 and 9,7 which al* L-ghaped in cros seetion, being a continuation of the parts indi- 125 cated in section in--Fig. 18 but havii,.ig,the vertictl flamges of less heioht as shown in Fig. 6, extend beneath the leading spar 1 upon opposite sides of the lower eO -es of the brace n-iember 60 to which they are spot welded. The sheet !@le@41 pi4tips -14 constituting the 130 brace the flan,-e 15 lying along the upper'tion in Figs. 21, 23, 25 and 26.
[5]1,540,106 covering of the lower surface of tho fixed section of the aerofoil are slid from the rear with their hooked edges in the channel of the rib 12 to @ point a little, to the rear of the leading spar 1. From this point forW:ard, the s@eet metal covering 14 iiiust be free' to bend, down-ward froin the positi6ii . dicated in Fig.,3 (or in dotted lines in in Fig. 4) to the position shown in full linos in Fig. 4. - To secure the ed@es of the sheet, metal pl@tes togeth6r, while i)ermittinly this downward bending, a chaiin@l . n-lembe@'61 is provided of the configuration indicated i@ Figs. 12, and 15. It will be seell that this 15 member consists of a flat strip of iiietal liaving its free @does bent inward to forii:i flanges 62 witliin whicli engag'e the flanged ends 63 of the sheets 14. The flanges 62 aro, slit at a short@, distalice from the rear end 20 alid bent upward as indicated at 64 in Fig. 12,,,these upwardly extending flaiiged por'tions being spoi Wel4ed'@tipon, oppos ite sides of the @haniael'member 12.. To. the !,ear of the flange members 64 the free edges of the 25 sheets 14 extend upward into the channel 'Within the rib 12'wliere they a're held by the stiip 57. The, slits in the; fl:iiiges 62 at the point opposite the rear end of the flanges ro,4 enable the flanges 6@' to' extend beneath 30 the member 61 into enlyagem@nt witli the flanges 62. At the forw@'rd eiid of the channel member 61, the flanges 62 are slit to permit @ the for'mati6n of lugs .65@ (ri ig. 15) which are curved upwardly in the reverse 35 direction from the flanges 62 to el-tibrace @flanges 66.upon the-lower ed(res of t'iie sbeet metal membei-s 32 constitu't7in@ the rib of -the iiose portion of the aerofoil. The lugs 65 slide freely upon the -flanges 66'so tliitt as 40 the sheet metal inembers 32 move forward Fio, l'to tliit member 61 is ,-c poi-tion of tb6 position 4.5 showii in Fi(@,. 2 to tlia,t slio i i 'Fi i,lr. 1, t I i e Ranges 66 enoauing the Iiigs 65 cause the r, 61 to' rdly ut channel meni I iiiove upnvi i o a position iii whicli it lies with its ii-pper stirface substajitially in'conta;ct with the, Icwer 50 surface of the sheet metal member@ 26 and 27 as shown in Fig. 18. The sheet . metal covering 67 of the inov@ able nose portion of the aarofoil is'secured from the rear of the upp6r surface" of the 55 ribs 31 to a @oiht indicated at 68 -in Fi -s. 2 - and 6 on the lower edge of the "ribs i'l, a little to the xear of tbe, forward end of @ the rib@ by me@ns of channelecl. members 60, having a flange 70 to which is w,elded the 60 upl),6r edge of the ibs 31 as @indicated iii r Fi-. 16. The strengthe,ning'plate 71 is seciired to the iniier face of the sbeet met-,il covering 67 and to the flaiiges 72 formed 6 the@ ribs 31. At eaeb of the ribs, the e-overilig i@ bent ii a Pw'rd above, the main surface to a height slightly greater ihaia the 6omb-ined height of the rib 31 and channel 69, the plate 71 secured to the bottoin 'flanges lying -substantially in line -with the main surface of the sheet 67. The UP7 TO wardly bent portions of the sheet metal 67. being joined at their u ' pper edges to the ch,,innel itember 69 by a strip 57,'and the channel being secured to th@ sheets 71 by means of the ribs 31; and the plates 71 beiiig 75 in turn secured to the sheet 67, all as indicated in Fig. 16, there are pi-oduced a series of strengthening ribs upon the @pper surface of the movable nose poriion at the locatioll in which the greatest pressure, is sustained, 80 and these rib are @n line witli the 'ribs 11 upon the fixed portion of the aerofoil. Additional r@ibs n' are formed in the sheet metal 67 betw6en the ribs 31, the cross s . ection of these ribs being indicated in Fig. 20. S-3 From the point 68 to the rear of the movable nose portion, the iiietallic sheets 67 are secured together by the interlocl,-ing flan-e conneotion indicated at 74, 75 in Fig. i5. -Upon the under sqrface of the ii.pper sid@ of 9( the movable nose portioil is secured amember 76, (Fig. 19), consisting of -a V-sliaped sheet of. metal having outwardly - extendino, flaiioes 77 iipon- opposite edtes engaging tl@e' she@t"xiietal'coverin& 67. T@ this me'mber 76 95 are, secured the f,@r'ward ends of rods 78 pivoted at-' their reai@ end - to bell cran@ levers 79 b@ which the rods 78. are operated to mqve the nose portioii- in or otit. The forw'ard ends of the gheet metal plates-13 100, are cuiled into the cylindrical form shown gt 80, the' free edge beinlr formed into a flaiige 81 secured fo the in@'er surface of the plat6 as shown in Fig.' 19. Pldtes 14 are turned backv@ard in a similar fold 82 as 105 shown'in Fio-,s. 2 3 and 4. - The traill"n",@ @ortion of the aerofoil bas sheet-metal covering plates 83 secured to the ribs 42 and 44 from the extr me rear forward ov the top ahd bottom, siirfaces to a' I @O point slightly forw'ard of the rear edges of the sheet motal coveriiigs'13 and 14 wliei@ the trailino, portion,is at its extreme limit o:f projection7outv@ard. These plates may eacli c6nsist bf sija6-le sheet'of metal folaed on, a it elf at the tiailiiig,ed@d. The manner of attaching the plateg 83- to the ribs 42 aiid 44 iselearlysho@inihfi .,2 4and2g,thecon-. .9s struction being ,8ubstantially identical witli thaf shown in Fig. 17, repre;enting the man- 121) ner of joining the @heets 13 'to the rib 11 At their@ forwa@rd 6nds, the. plo@tes. 83 are folde& bgc'kward, as' iii d . icated ut 84 and 85 (Fig. 10) in i@.@manner similar to the folotinr of t4e edge',80 shown in Fig. 19. The 125 pl;tes 13 and i4'ake,@.qlso bent forw,,ird iii the manner- indicated at 86 and 87 ir- Fi(rs. 9 and 10 to provide a smooth flat surface 'Lor' en-agemeni with'the -Lipper and lower . surISO faces of the plates 83 as the tra:iling portion
[6]1,540,104 '7 of the aerofoil is projected and retracted. The retracted position is showli in Fl 9, and the piojected position is shown@ in ig. 10. Upon the inn6r surface of the upper for.ward edge portion of the sheet; 83 is secured a bracket member 88 as seen 'in F@iQ-00, to which i@ pivoted at 89, a rod,@90, the opposite end of the rod being pivoted to the bell crank lever 79. 1( The aerofoil may be made up in a series of paliels of which the movable portions are independently movable. In Fi-', 8 the en'd paiiel may have the bell crank rs 79 coiitro-Iling. its nose and tra-iling portio'ns co'nnected by a rod 91 with a lever 92 controlled by iiieans of a hand wheel 93, and the p4nel 94 may have its bell crank levers 79 connected by a rod 95 cojitrolled by a hand lever 96 operated independently @ of - the.. 20 wheel 93. The operation of these movable iiose qnd trailing portions of the outer paliels to coiitrol'the, latet,-tl stability' of the airplane is explained ia detail in my co-.pending appli25 cationpreviously herein r6ferred to. It will be apparent that, sih6e the length of the arms of the bell crank levers 70 differ,. the rods 78 being pivoted to the short arms, of the levers and the rods 90 to 30 ,ttMS, MoVement@ of the bell crank le result in a more rapid projection of th ing portion than of the ose portioia, exte.-it of r@iovement of the trailing portion will be approximately three times that of, 35 the ziose portion. It will'alsci be seen that in the retracted position of t-he nose p@ortion shown in Fiol,. 3@ the rear edges of the sheet metal coverin- plates 67 lie 616sely adjacent: to the outer s@irfaces of t-lie plates 13 and 14 40 and'thai as the nos@ p,6rtion is thrust foir-' sheets 14 bend downward from a -point, ,t 45 little to the rear of the le,@din , g. spar - 1 "so that a substantiary c'o'ntinuous curve is maintained upon both the top and bottom surfaces during the @ ent,ire range, of moven ment of the iaose portion. 50 It will also be observed that the air pressure tends to force the rear end of the shee,t metal 6'@ cif the nose, portion closely, into contact with the lower surface 6f t-lie sheet 14. 55 The trailing @ortion in the retracted positign lies almost completely enelosed within the fixed ce-.itral portion of the aerofoil, a small portion of the lower surface being exposed at the rear while in the closed lio60 sitio,-,i indicated in Fig. 9. The rib 42 is curved on a-,i are of a dircle concentric with t-he curve of the guide tracks 37 and 38, so that a .the trailing portion is projected to under surfa'ce of the folcted portion 86 of the upper slieet inetal covering 13.@ However sirice the upp6r and lower surfaces of tlic, t'railinc, portioii divoirge at an angle, as the trdilini port-ion is projected from the TO position shown in Fig., 9 to that sliowii in Fig. 10, the low@r surface ol the sheet 83 slidin-o,' in contact with the upp-pr surface of ti-le' folded edge portion 87 of the sheet 14 will cause the sheet 14 tb be bent down- 75 'War d in a curve which beging at the point -at which the flaiige 15 of the rib 12 is left free 'froin attacbment to the brace n)einber 52. The lidwek surf'ace. of the plates 83 6f the trailing. portion will be formed on .1 80 'cur ve which will be substantially a continuati6n of the 6urve formed- by th6 lower surface of the sheets 14, so that the lower. urface of the aerofoil at th@, reai@ has a substanti ally coi4tinuotis curvature, the only 85 break i n'thiscurvature bein(r at the.point. where t@e folded portion 87 of the slieets 14 h6ld s the sheets 14 a slight dii@t-ance away from the plates 83. Since the sheets 14 overlap the lower outer surfaces of the plates -90 83, pressure of the air upon their lower Surface s will tend to hold the sheets 14 closely in - contact with the plates 83. To relieve the fricti on between the lower surface'of the plate 93 and the folded over portion 87 of 95 the plate 14, the rollers 97 will be journaled - at the fear end of th6 ribs 12, these roll6r cont acting .tt their periphery @vith the outer face of the locking strips 57 which hold the shee ts 83 within the channeled ribs 44.' 100 W hile the @pars and ribs an'd the manner o@ atta -Ching.. the sheet met'al plates to the ribs have been shown in detail, illustration of the drift trussing'has been eiatirely omitted, since this forms no part of the pr esen@t 105 @"he rear, the upper surfac@ of , the sheet bet,i@@@n the forward en'd, of the nose:and the 65 metal 83 remuins in close coiatact with the highest 'O;rdinate substantiary coincident. la@O tion of ribs and spars the attachment of drift tru ses may readily be accomplished. 110 The c6ntinuous loingitudinal curvuture of -Llie upper sheet metal m6mbers 13 produce@ a lateral rigidity of the metal sheets between the ribs which substanti@lly prevents saggin- of the she@bts transver@ely b@tween the rib.q-, whereag in wiiigs havin-- a canvas coveving, t-he tension causes the fabric to curve inward betweeii the. confronting edges of the ribs to produce a waved surface. This lateral ric-@idity of the sheet metal covering 190 prodtcecby its longitudinal clirvature materiall assists in -securing rigidiiy of the. y aerofoil, and decreases- thia necessary weight of drift trussing. The initial wiitig section in the present 125 metallic construction will be chosen wiih,a top camber iipon its tipper, surface havina - a curvature at a point subgtantially midwa y ward to the po?sition indicated in Fig.,4, tlie,@@ invention, and may 6bviously be modified to upper rear edges o@ the - sheet-s 67 @remain in suit diffe'rent designs (if aerofoils. @ It willclose contact with the sheets 13 while the. be evident that with the pres6nt construe-
[7].8 1,540,105 wieu the are of a circle, and the movable nose section will move forward- and downward in an are of a circle - concentric, witli the'.are forming. a portii)n of the top surface, the shape of the forward porti6n 'bf the nose being $u6h that wheii ilie movible -nose portion is at its point of e treme for'wa-rd movem6nt the upper gurface of the' aerofoil will be-of substantially continupus 10 - curviliture, 'a@d this curvature @ will be oiae whi6h is @fficieni'for slow speed. Coiisider7 .ing.f6r,,,& moment. only t.he upper surfaceof e seen at -the aerofdil " it will b th it will be possible t6--choose an efficient camber fof Iiiili 4peeds, a portion of 'which will be a subst;@iitiary circular 'are .&'nd t.h@t by 'i@xtending the upper- surfa@e of tho. aerofoil along the circular are, for a limited distOLiace, a new curvature miy-be obtained 20 adapted for the uppei surfacb of an aerofoil elteient for flight -at'slow speed. Considering the upper surface of. the trailiiag portion of the, aerofoil, it will be een that when the -movable trailing portion 25 is projected'alo:pg an are of a circle concentrfe with the: curvature of the -guide tracks @ontroring this movement, there will be a slight discontinuity of curvatu're at the point which forms the trailing edge of the 30 ro aerofoil, suitable for 'co-operation with the curvaturp obtained upon the upper surface by the extension of th& movable nose and trailil@g , portions, @h-is curvature- of 'the 60 lower surface may readily be epro4uced- by ble.camlu . dou L,. r'toward -the rear of the irail@. mg portion -has been found to produce an offici6nt chamber. for slow speed, the - @e:ffect 35 -of -the double camber apparently being to assist iii, p@@venting movemefit of the center of p'r'essure wiih chanking angle of ineidence, Considering the lower surface of the sero40 -foil, it 'will b6 se@ia that a relativelv hi h caifiber able. for @lower speeclgsuit obtained wit-h substaiatially no disco of curvatute,by rovidi-fig a fix6d poi-tion haviiig ieexible coveri 45. thl-front and,rear of the.fixe .flexure- of which-,will be cothe downward and outward,movement of -the nose, andtrailin-a porti6ns, and that the ure 'iible metallic covering curvat of the fl@: .50 may b6 made to co-operate with: the curvature of ihe,lowek surfaceg of t]@e nose and trailing portions by @ oviding agraduation of: the rosiliency 6f the nietallic ribs supporting the cover plates. H-aving'chosen in the desired curvature by a suitable adj'un'- nient 6f the rigidiiy of the suppotting ribs, this adjustmeiit of rigidity being atta' in@ d, by suitably'varyilig the width of the flanges, up6n the upper surtace 6f the ribs. to A curvature for the lower surfaco,. of a6rotoit@-w'ill be@chosexi such that a portiorr somewhitt in advance of the penter 6f,,the chord will be. do-incident with the curve -forining th6 lower -po'rtion of the initial see- -75 tion. @ The curvatilre of the low'er - portioh of the nose wfll be one which -will produce an@efficient section for the nose portion iia either its projected or retriieted position. The lovoe'r surface of the trailing portion 80 can of course be made of any desired configuration,- itnd the spgoes between the iri6v-: able nose and, trailing portions'and the fixed central section will be bridgod by flexible sheets, the cur'vature cif wliieh may be requ-. 85 -Iated by Proper adjustment 6f the rigiclity of the @upporting, ribs at v4rious - points throughout their' iength. By the structure he rein described; an increase in area rhay be obtained amounting to 90 upwards of thirty-thi-ee per cent without undue increase in weight, and furthermore this increase in area, while'giving incieased lift@ is not, ittended by discontinuity of camber which in certain,,oiher types of variable camber aerofoils is attended by great increase in resistance, is in -the present device produced with a minimuin discontinu- 100 ity-of curvature, with an increase in area, a@nd I with an inerea e in the s . @ n g l e o f i n e i dence, all of which produce increased lift'mg power, wbile avoiding an accompanying charige in the angle of the axis of the pro106 peller - vvhich wo'uld re-sult 'in lower @fflcieucy. .@Wliile the chord. increases, - the. @l'hat6miim ordi ' I n a t e i n t h e p o s i t i o n i n w h i c h ' . , t h e - n @ ; s e : a n d t r a i l i i i g p o r t i o n s . a r e f u l l y e x f e n d e d , l i @ , s - a t a b o u t , t h e s a , m e p e r c e n t a g e 1 1 0 o f t h e c h o r d - f r o m t h e f r o n t a s t h e m a x i m u m - o r d i n a t e v l i e s w h e n t h e a e i o f o i l i @ i i i t h e @ o n f i @ u r a t i o i a p r o d u c e d b Y , t h e r e t r a c ' t i o ' n o f t h e m o * a b l e p o r t i o n s . T h e c e n t e r o f , p r e s s u r e w i l l t h i l s n i ) t b e m - o v e d g r e a t l y 1 1 5 t o ' t h e r e a r b e c a r [ s e b f t h e t r e a t e t p r o ] 6 c t i o i i o f . t h e t r a i l i n g ' p o r t i o n , a n d . t h i s t e n d e n c y . b to r6arward moveiiient will o bilanced b y the tendency to forward movement of the -ac loilinitsiiiitialposition,withihemOv-' curvatute and loss of efficiency as in certain 95 abletraifin po,rtionfuHyretracted,butt-his@ devic'es hitherto proposed. The change in 55 a burvature for tl@e lo-tver surfaces of the conterof pressure due to the inere'ase of the 120 angle of incidence. f incidenee b6en s- bee - incioased' n dified.-,-,sb @.th[tt' b' f125. A@e @ng 0 making tho -lower surface of, the trailing the c in addition inerease @ @'m er, portio_u of the curvatuie selected ap-d. then ihe ift- -has vky greatly iiie eased r the ciirvature of the flei@ible co-@erthe ceiite-r of, pressure has'i-ditained re @ini heets connecting the trailing portioii at. subptantially. the sa4Ae posi ion -with, 7. g 't7o the center o - avity. of the mach....... ' w ths the fixed central; n 130 portio to assume sp@et f gr in e .
[8]1,540,105 Complete projection of the trailing -Dor-, tion lowers its rear edge below the l@Nier edge of the nose, portion to inereas(- the angle of incidence by ,tboiit four deoi-ees ii-i r) the configuration shown witliout cliangin,r the angle, of the fiiselage.. This angle of incidence inay of coiirse I)e increased in the tisu.tl way I)v tilting the fiigelage until the desii-ed lift is reaelied, I)iit tl-le amount of lo tilt iiecess.,tr ir will I)e approxin'lately onetliircl less than if the wing h,,id no oiitwardly exteilsil)le po.rti.oiis. For climbiiig, the aviator may -,t,:irt from i-est witli the nose and ti,,iiling poi-tions fiillv 15 i-etracte(l, to decrei,se the resistaiiee@ to t];@ iiiiniijitiiii.- 'tliis will give the higli section witli the iiiiiiiiiiiiii, caii-il)er @Lud the iriiniiiiuiii angle of incidence. Thus tlie.airplane inay quickly attain sucli speed iTi 1-un20 ning along the ground for a sl-ioi-t distance tli,,tt if the nose and tr,,tiling portiolis ai-,., rapidly projected, the increased are,,i, in(@i,easecl cainber, and ifiereased an-le of inei(lence - Will prodilee slibstantially instantane25 OIISly a sufficient. ]if t for take-oit at the speed ali-eady attained, thus shortening the necessai-y travel along the krotind.@ After the airplane has reached a stifficient lieiglit,- tlle inovable' nose. and trailing por3r) tidns of the centra,l panel or panels of the aerofoil will be retracted wiihout chano,@ing the position of-tho movable portions of tl-ie outer wing panels. The central.portioln of the aerofoil will tlius assume a cambpr for 35 higher speed,, and as the speed increases, the operat6r may-move the lever to retract the movable portions of the, outer wing panels to the fully retracted position, so that the entire aerof6il will be gii@en the most 40 effieient camber for high speed. At the same time lateral stability may be obtained.by stich slight - inovelille'nts of the controlling iiieans as are iiecesiary to project the movable portions upoiieitl@erwingiovarythelitt,,. 45 For landing, the nose and trailin@,r portionf@ will be bro-Li(,rllt to the.fully pr-oje(@,te(I posifion@ giving an iiierease in v7jng area of approximately tliirty-tlii-ee Per cent witti the seet'lons herein iliiistr,,tied. At the same ,)O time the fusela(ye will be . giv@en the necee ;sarl, tilt to produce,the angle at,which thb lift is greatest. After th(@ whe@ls have come into contact with the ground, the nose . and trailing pot55 tidns will be retracted to decrease the lift, and thus the weight of the machine will be thrown upon the - whe@ls, whereby briikes tipon the wheels will be rendered more efficient. lfhowelverthelaviaiorwishestoutilize the resistance due to the large wino- area ai a.high angle of incidence to chee@ inovement uiideir fa;vorable wind conditions, theinovable porti6ns may be left.pl-ojected to their oute@.iimit, -,viif, the aerofoil tilted to the i iiaxlrnuiii angle bf incidence. Fro m the foregoing description', it will be ippai.- ent that thtre has beeil provided an aerofo il in whicli the stream line of the cqml)e red stiffice is not main-tained, but iii wllicli the configuration is varied from 70 i foi-iii efficieiit foi- Iiigh speed to a, form effidie iif foi- Iiigli lift at low sl)6eds. The variati on in the chol@d produced by retraction of the niovable portion will of oourse cause .t clianue in the aspect ratio, the hi(rher 75 -,spect ratio at high speod and at low angles giving a better lift/drift ratio, while the (- iivatiii-e of the -Lipper surface of the trailiiig poi-tion is iiot similar to that of the t@gp of the fixed.section, but is an arc of a 80 ciiel(@, alid lvliile the curvature, is not n-taintiiiie@ [ as the trailin-- T)ortioli is projected, actiial. ivind-tunnel tests have also demonsti@,tt ed tha.t the doiible-camber of @the upI)er surface prodticed when the trailing por- 85 tion is projected is highly efficient. These tests liave also dellionstrated that the camI)er of the upper -surf ace of an aerofoil may consist iii part of arcs of circles at the forward and rear ortions in a hi -P _ghly 1)0 (@ffici ent' section. It will be obvious tha-t many changeg niay be ni,,tde in the details of construction of ihe varioiis portions of the airplane with cliang es in design without departing from 05 the I)rinciple of the 'invention herein set forth or sacrificing any o,f its advantages. The invention is ttlerefore claimed broadly witliin the legitimate scope of the apI)eiide d claims., 100 I
