US1540105A - Airplane - Google Patents

Description

J. F. COOK, JR

AIRPLANE 4 Shets-Sheei: 1

Filed Dec 18, 1922 A an,

J.F.COOK.JR

June

AIRPLANE 1922 4 Sheets-Sheqt 2 Filed Dec. 18

June 1925- 1,540,105

J. FJCOOK, JR

AIRPLANE Filed Dec, 18, 1922 4 Sheets-Sheet 3 J. F. COOK, JR

AIRPLANE 4 Sheets-Sheet 4 Ill/1111111111??? Filed Dec. 18, 1922 siding at Detroit, in the Pamela... 2, 1925.,

PATENT-"OFFICE.

JOHN F. coox, .13., or nn'rnorr, moment.

AIRPLANE.

Application filed December 18, 192 2. Serial in. 607,589.

To all whom it may concern: Be it known that I, JoHriF. CooK, Jr., a citizen of the -United States of America, re-

county of Wayne and State of Michigan, have invented certain new and useful Improvements in Airplanes, of which the following is a Specification, reference being liad therein to the accompanying drawings.

This invention relates" to an internally trussed aerofoil-of metallic construction, and has for its object the provision of means' by which the area,;thecamber, and the angle of incidence may be varied simultaneously without varying the relation of the main portion of the aerofoil with respect to the line of flight.

A further object of-the invention is the provision of an aerofoil having a cross section of low camber for high efiiciency at small angles and high speed which may be varied to a cross section of relatively deep camber and a high lift elficiency at low speeds while maintaining a minimum drift co-eflicient by utilizing the flexibility of the lower sheetmetal' covering to obtain a gradual curvature of the lower surface at all points during thevarious stages of adjustment.-

Another object'is to provide an aerofoil having movable nose and trailin portions to produce variable area and variable camber, in which both the top and bottom surfaces throughout the entire range of adjustment have a minimum discontinuity of] curvature. N

A still further object of the invention is to provide a construction of aerofoil in which the use of riyets and wires is avoided and in which the sheet metal plates forming the covering of the "aerofoil may be i Fig. 2 is a corresponding section of the same aerofoil having its movable nose andface plates of the nose portion in the extended position corresponding to Fig. 2;

Fig. 5 is a fragmentary plan view ona larger scale than that of Fig. 8;

Fig. 6 is an elevation of a rib secured to the movable nose portion shown as separated from a co-operating terminal member forming a part of a'rib of the central fixed section of the aerofoil;

Fig. 7 is a side elevation of a terminal member secured to. eachrib of the central fixed section at its rear end, together with 'a rib of the movable trailing portion, the two members being shown in their opera tive relation when the trailing portion is partly extended; I

Fig. 8 is a plan view of an aerofoil showing a central panel having the movable nose and trailing portions completely closed, and

a left-wing panel with the movable portions mg broken away;

Fig. 9 isa diagrammatic fragmentary section-through the sheet metal covering members between the ribs in the closed position of the trailing portion;

Fig. 10 is a similar diagrammatic frag- Fig. 12 is a perspective View of a frag ment'ofthe interior of the lower front portion of the aerofoil adjacent to'the leading spar;

. Fig. 13. is afragmentary elevation" of one of the beams or spars;

Fig. 14 is avertical transverse section of a partially pro ected, the right wing panel bei.

portion of a beam on the line XIVXIV of Fig. 13, looking in the direction indicated by the arrow;

Fig. is a vertical section/taken on the line XV-XV of Fig. 2;

Fig. .lfiiis a section taken on the line XVI .of Fig. 2;

- Fig. 17 is a section taken on the line XVII v of Fig. 2;

Fig. 18 is a section takeh oni the line XVIII of Fig. 1;

19 is a section taken on the line XIX of Flg. 5, looking in the direction indicatf ed by the arrow;,

Fig. 20 is a section on the line XX of Fig. 5; FFigi 21 is a section on the line'XXI of Fig. 22 is a section on the line'XXII of of Fig. 1, looking in the direction indicated .by the arrow;

' Fig. 23 is a section on the line XXIII XXIII of Figs. 1 and 11; V

Fig. 24 is a section on the line XXIV ofa Figs. 2 and 7, looking in the direction indicated by the arrows I e Fig. 25 is a section on the line XXV-e XXV of Fig. 1; i

26.is a section on the line XXVI of 31- i Fig. 27 is a section on the line XXVII XXVII of Fig. 6;

Fig. 28 is a section on the line XXVIII of Fig. 2;

. the arrow;

Fig. 29 is asection on the line XXIX of Fig. 2, looking in thedirection indicated by Fig. 30'is a section on the line XXX of Fig. 5;

Fig. 31 is asection on the line XXXI XXXI of Fig. 6; and

Fig. 32 is, a fragmentary elevation of a portion of the lower chord member.

It is well known that the Wing curvature is a determining factor in the efficiency of an aerofoil. An aerofoil of lowca'mberhaving a relatively low lift has" been found to have high efliciency-at small angles of'inci-' dence and at high speeds, and the area at such speeds may be made very small. However it is essential that the speed at the time.

of landing shall not be so great as to endanger the safety of the pilot or of the airplane.

' .The most efficient wing section for low dlt,l11e of horse power at the first and foremost consideration, an approximation to a stream line wing'sec'tion at a small angle of incidence, varying from 0 to 2 is necessary." Further, it is essential that the fposition of the center of pressure for theastest flying angle shall be quite stable, and with a margin of safety in case of unforseen circumstances causing. a fur ther decrease, of angle'of lIlCldGDCB. F or I slow flying, a Wing'section characterized by good upper and lower surface cambers, and

comparatively large angles of incidence, is

necessary. Further, it, is essential that the angle of incidence for slow flying shall not be too near to the critical angle at which the lift co efiicient decreases and the "drift increases, and that at the maximum angle of incidence the center of a stable position.

Fora good speed range, a wing section should have the following qualities:

The center of pressure for the range of flying angles used should'have a" stable position and the minimum range of movement along the chord. In agood wing section, thecenter of pressure at all angles of incidence used in flying, ascending or alighting should lie between 30% and 45% of the chord-to the rear of the leading-edge.

The lift 'co-efficient should increase continuously from a negative or zero angle to about 15 and it should then remain constant and decrease at aslow rate without having a sharp critical angle, The maximumlift coefficient should not be lower than 0.65, and the maximum drift co-eificient pressure shall have ought not' to exceed 0.10.

the highest speeds, the drift-co-eflicient should be a minimum, and for the minimum expen- 'aximum speed, the lift co-efficient at the minimum value of the drift co-efiicient should be sufli- 'cient for the wing area chosen to support the loadiat that speed;

' Two methods of improving. the performance of an airplane have been ,suggested, but have hitherto not been put into common use volved. One methodis to increase, the wing because of the mechanical difliculties inarea just before landing The other is to.

increase the lift co-eflicie'nt when landing.

jection of front and rear movable portions to increase the area, each of the movable-portions following a curved path, and each, as,

the result of it'smovement, causing the metal plates constitiiting thelower surface of the to one of deep camber when the movable portions are fully. opened. Furthermore,

the rate of projection of the rear movable- The aerofoil illustrated herewith has a structure permitting the simultaneous pro in such manner that during the change in to the rear.

trailing portion is greater than thatof the front or nose portion, and the curved path of movement is such that when the movable portions are fully projected, not only are flight, this beingits position of maximum etliciency.

The position of the maximum ordinate of an aerofoil is an important factor in determining the location of the center of pressure. The relative movement of the front 'and rear movable portions, for any given relation that may exist between the sections of the aerofoil in its fully closed and in its fully opened positions, will be determined position of the movable parts the maximum ordinate will move slightly to the rear with respect to the fixed portion of the aerofoil.

Movement of the maximum ordinate to the rear will normally cause rearward movement of the center of pressure. Conversely, increase in the angle of incidence will normally cause forward movement of the center of pressure. The variation in the wing section during opening movement of the nose and trailing portions produces rearward movement of the maximum ordinate which tends to move the center of pressure The higher rate of movement of the trailing portioncauses an increase in the angle of incidence of the aerofoil which tends to move the center of pressure forward. These two. factors counterbalance each other.

Either forward movement of the front movable portion or rearward movement of the trailing portion of the wing would cause a movement of the center of pressure, but by causing the proper relative movement of both to occur simultaneously, the effect of one may be made to balance that of the other and the center of pressure will thus remain at substantially the same place.

Slight movement of the maximum ordinate to the rear increases the lift co-eflicient at higher angles of incidence and atthe same time counteracts the forward movement of the center of pressure due to increase in the angle of incidence.

The lift may be increased by an increase in :area, by an increase in the angle of incidence, and by an alteration of section.

As the nose and trailing portions are projected in the aerofoil of the resent invention, the lift is increased taneous action of each of thesethree factors. Lateralcontrolof an airplane may be obt ained byvarying the relative lift upon the pep-gels on opposite .sides of the fuse1age,ithis y the simul variation being produced in the present aerofoil by varying the relative amount of projection of the movable portions.

' In my co-pending application, 607 ,538, filed Dec. 18, 1922, I have described a control mechanism for accomplishing this variation in area of the aerofoil panels The aerofoil illustrated in the accompanying drawings is constructed entirely of metal, the beams and ribs being preferably made of alloy steel members secured together by electric spot welding, while the sheet metal plates covering the surfaces will preferably be of aluminum or of light me- I tallic alloys. I

In Fig: 1, the main beams or spars are shown with the spar 1 located near the front 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 fixed portion. These spars consist of an 'upper plate 4, alower plate 5 and side plates 6 and 7, the plates 4 and 5 being preferably formed with flanges 8 as shown in Fig. 13,

secured by spot welding to the side plates 6 and 7. The side plates 6 and 7 will preferably be stamped out to form diagonal brace members 9, flanges 10 .being formed around the stamped out portions to provide rigidity. Sheet steel ribs -11 and 12 are se- Serial No.

cured to the .upper and lower edges respectively of the spare 1, 2 and 3, these ribs being in the form of channels adapted to receive the edges of the sheet metal plates 13 and 14 forming the covering of the upper and lower surfaces of the aerofoil.

The ribs 11 and 12 are secured ,to the spars as indicated most clearly in Fig. 14. Each rib is provided with a central flange 15 sides of the strengthening corrugation 16.

Brace members 17 shown in Fig. 14 are preferably formed of thin sheet steel folded upon itself to provide parallel members 18, 19, separated along one edge to embrace opposite sides of the flange 15 and flanged along the other edge at 20 to abut against the plates (i and 7 and the flanges 8, the folded edge forming the hypothenuse of each triangular brace member. The flanges 20 will be secured by spot welding 'to the plates 6 and 7 and to the flanges 8, and the edge p tions 18 and '19 will be spot welded to the flange 15. Tubular drawn steel braces 21 have their ends flattened and separated to engage upon opposite faces of the brace member 17, the ends of. the members 21 being shaped to fit closely within the corners formed by the flanges 2G the. body of the rib12. The overlapping flattened welded to the bracelnember 17.

ends of the braces 21 will also be spot curve of the rib 11. The rearpor-tions of Between the plates ,6 andl7 at the point fore modified to the confi uration shown in at whlch the braces 17 engage the outer Fig. 17 in which it willfaces of the plates. is, located an .interior member 11 no longer has the flange 15, and

brace member 22 having flanges 23 welded the member 34 has the, portions above and.

to the inner faces of the plates '6 and 7 and below the side walls 39 cutaway so that the having a flange 24 formed along its. upper upperinner faces oftlie side walls 39 lie I lower sides of the;'spa'rs 1, 2and 3 upward is shown in cross section in Fig. 24 at ato engage the flange upon the lowersurpoint immediately at the rear of the rear r edge to provide additional rigidity. This on opposite sides of the rib 11 and are spot plate may be perforated for the sake of lightness.

The braces 21 extend diagonally from the welded thereto The rear portion of the .r1b 42 which extends along'the upper surface of-the trailing portion of the aerofoil face of the upper rib 11 between the spars; end of. a brace member 43 consisting of'a As shown in Fig. 11, between the adjacent steel tube flattened at both ends and secured ends of the braces 21 where they lie in conby spot-welding to the underside of the rib tact with the flange 15 is the flattened end 42 and to the upper side of the rib'44 whic of the tubular brace 25 which extends be lies alongthe lowerside'of the trailing por tween the ribs -11 and 12, -at-.substantially tion of the aerofoil. ,A;brace,i1i1ember boththe member 34 and the rib 11 are therenoted that the v right angles to ea'ch. The flattened ends of extends from a point near the front end the braces 21 and 25 shown in Eig'. 11 are 'of the brace 43 and the 'rib 44 to the forward secured by spot weldingtothe flange 15. end of the rib '42 at the point where the At the forward edge of the aerofoil, sheet roller 40 is journaled. A cross brace 46 exmetal members, 26 and 27 are secured. to tends between the rib 42 and the brace meme the leading spar 1 as-indicated in Fig. 6. her 45, the upper endof the brace 46 con- These sheet metal members are symmetrical necting with the rib 42 at the point where v in construction and arranged parallel with the roller 41 is 'journaled. Another brace each other to form acha-nnel' indicated in member 47 ex tends'between the rib 42am] section in Figs. 22 and 31. Y The sheet metal the rib 44 substantially at right angles tois *bentas indicated M28, 29 to form upper the rib 42, its lower end being secured by and lower curved tracks connected by side spot welding to, the brace 43. A. brace 48 walls 30. Above and below the tracks, the lies between the upper end of the brace 47 sheet metal members 26 and 27 meet asand thelower end of-th'e brace 46, the up shown in Figs. 6 and 22 toward the rear" per, endbeing secured to the rib 42 andthe.

end of the structure, but toward the front lower end to the brace 45. Asshown in Fig. end, the platesare separated above as indi- 7; the rollers '40 and 41 lie between the,

cated in Fig. 31 and below as indicated in ,tracks 37 and 38. The portionof the rib'42 Fig. 27 to permit the passage of the rib; lying to the rear ofthe upper end of the member 31 secured to the movablenose. por-q brace 47 is curved on an arc of a circle contion ofthe aerofoil. This rib nem-ber centric with the curvature of-the" tracks 37,

composed of sheet metal plates having their 38,'but having a slightly smaller radius and front edges of the contour desired 'for' the the portion of the rib 42 between the upper fforward edge of the. movable nose portion, ends of the-braces 46 and 47 lies at some This member 34 consi of the aerofoil and the central portion is what of an angle to the portion of the rib formed as a rearwardly projecting bearing 42 between the rollers 40 and 41 so that as bracket 32 upon which are journaled rollers the rollers 40 and 41 run along the tracks 33 having grooved peripheries adapted to '37 and 38 in the arc of a circle, the upper engage the tracks formed ,by the folds of surface. ofthe rib 42 will move along a consheet metal at 28 and 29. centric circle and therefore, will not move In Figs. 7 and 21, is illustrated a rear away from the extreme a end of the I sheet metal track member 34 secured to'the lower surface of therib 11. The forward trailing spar 3 and to the upper rib 11. end f file rib 42 lying b tween the rollers of symmetrically- 40 and 41 is compressed into the configurasha-ped parts 35,336; bent at 37 and 38 to tion shown in'section 1n-F1g. 17. form upper and lowe'rtraoks, connected by 1 The extreme forward end of the s1de side walls 39, with \which engage grooved .rollers 40 and 41 secured to a rib -42 constituting part of the trailing portion of the aerofoil. At its forward end, the vmember 34 has the upper edges. of its parts 35 and'36 spot welded to; he flange 15 of the rib 11, but the'channellying between the upper and 'lower tracks and the. walls 39 is formed on an arc of acircle intersecting the walls 39 are spot welded on opposite sides of the brace member 25 which extends between the ribs 11 and '12 substantially midway between the spars 2 and 3. A' brace'49 similar to'the brace 21, but shorter, extends between the rib '11 and the upper edge of the plates 35 and 36,-,the upper end of the 11, while the lower end is also flattened to Overlap the upper edges of the plates 35 and 36. A brace member 50 consisting of two channel shaped plates shown insection in Fig. 28 extends between the lower edge of the side walls 39 and the brace 17 at the lower edge of the forward face of the trailing spar 3, the upper end of the plates 50 being secured on t e outer faces of the walls 39 at a point opposite the lower end of the brace 49. The brace "51 extends upward from the upper edge of the plates 35, 36 adjacent to the lower end of the brace 49 to the brace *17 ,which in turn is secured to the rib 11 and the upper portion of the forward face of the trailing spar 3. Between the brace plate '17 at the lower edge of the spar 3 and the lower end of the brace member 25 to which the forward end of the walls 39 are secured, extends a brace member 52 shown in cross section in Figs. 25 and 26. This brace member 52 is made of a sheet of steel folded centrally in the shape of -a tube along its upper edge, the free edges 53, 54, being separated and the portion-between the free separated edges andthe tubular portion being secured together by welding. At its forward end, the free edges 53 and 54 embrace the flange 15 lying along the upper" surface of the rib 12 and may be secured thereto by spot welding adjacent to the lower end of the brace 25. To the rear of this forward end, however, the flange 15 is not secured to the free edge portions 53 and 54. but the rib may be bent downward so that the flange 15 will be partly withdrawn from the'channel between the free edges 53 and 54 as indicated in- Fig; 26.

-The method of securing the sheet. metal plates 13 to the ribs 11 is indicated in Figs. 17 and 2 1. -1 7 As most clearly seen-in Fig. 21, the free edges of the sheet steel constituting the channel portion of the rib 11 extend inward toward each other in the same plane and are then bent at substantially right angles to that plane inward toward the center of the channel to form flanges 55. The sheet metal plates forming the covering of the aerofoil have their edges bent angulzfrly into a hooked shape adapted to engage with the .flanges 55 as the edge of thev plate is slid longitudinally of the channel from one end of the rib 11. After both plates have been -placed within the channel, a forming tool will be drawn longitudinally of the channel to press the free edges of the sheets 13 into the inner corner formed by the flanges 55 with the outer faces of the'rib 11 as indicated at 56. The tool is withdrawn and a locking strip 57 preferably of aluminum or of a light alloy' will be drawn into the interior of the channel to hold the free edges "ofthe sheets 13 securely locked aroundthe fiange's'55 shown in Fig. 17, It will be strip 57 is of the same configuration in every case.

tion will be uniform throughout its length, thus enabling it to be readily drawn into the channel after the tool has pressed the edges of the sheets into position.

The strip 57 engages the surface of each sheet 13 within the corners formed at 56 thus preventing spreading of the channel. The outer arms of the T-shaped strip 57 lie on opposite sides of the two inwardly extending flanges 55 with the infolded edges of the plates 13 surrounding the flanges and held firmly and uniformly at all points throughout their length. This gives much greater rigidity and is a much stronger construction than is secured by the use of rivets at a series of separated points along an edge of a plate.

For the sake of clearness, the locking strip 57 has been omitted from the illustration: in Figs. 21, 23, 25 and 26.

fixed section of the aerofoil are provided .with a flange 15 from their forward ends adjacent to the leading spar 1 rearward to a point indicated at 58 in Figs. 2 and 32'. Flange 15, as has been stated, is secured to the brace 52 by welding adjacent to the lower end of the brace 25.' From this point to the point 58, the flange gradually tapers until it merges with the flat upper surface of the rib, the rib from that point to the rear having a cross section similar to that shown in Fig. 17. At the forward end of the ribs 12 upon the lower surface of the fixed portion of the aeofoil, the channel member is compressed to form a flat verti-. cal webindicated at 59 in Fig. 12, this flattened portion terminating at the leading spar 1. A brace member 60 similar in configuration to the brace member 17 has its forward gflanges welded to the side plate 6 of the spar-1, its lower edges embracing opposite sides of the web 59 and being welded The locking strip 57 will preferably be drawn through a die so that its cross secthereto. The brace member 21 has its lower I end flattened to form parallel lugs engaging on opposite sides of the brace member 60 g which are welded thereto. The rear ends of the sheet metal members 26 and 27 which are L-shaped in cross sec-- tion, being-a continuation of the parts indicated vin section inFig. 18 but havingthe member 60 to which they are spot welded. The sheet metal plates '14 constituting the covering of the lower surface of the fixed section of the aerofoil are slid from the rear with their hooked edges in the channel of the rib 12 to a point a little to the rear of the leading spar 1. From this point forward, the sheet metal covering '14 must be free to bend, downward from the position indicated in- Fig. .3 (or in dotted lines in.

Fig. 4) to the position shown in full' lines in Fig. 4. To secure the edges of the sheet' metal plates together, while permitting this downward'bending, a channel member 61 is provided of the configuration indicated in Figs. 12 and-15. It will be seen that this member consists of a flat strip of'metal having its free edges bent inward to form flanges 62 within which engage the flanged ends 63 of the sheets 14. The flanges 62 are slit at a short distance from the rear 'end and bent upward as indicated at 64 in Fig. 12, "these upwardly extending flanged portions being spot welded upon opposite sides of the channelmember 12. To the rear of the flange members 64 the free edges of the sheets 14 extend-upward into the channel within the rib 12 where they areheld by the strip 57. The slits in theflanges 62 at the point opposite the rear end of the flanges 64 enable the flanges 63 to extend beneath themember 61 into engagement with the flanges 62. At the forward end of the channel member 61, the flanges 62 are slit to per- 'mit. the formation of lugs 65 (Fig. 15)

which are curved upwardly in the reverse ,dlI'BCtlOIl from the flanges 62 to embrace flanges 66 upon the lower edges ofthe sheet metal members 32 constituting the rib of the nose portion of the aerofoil. The lugs 65 slide freely upon the flanges 66 so that as the sheet metal members 32 move forward from the position shown in Fig. lto that the aero shown in Fig. 2', the channel member 61 is bent dovgnward and as the nose portion of flanges 66 engaging the lugs 65 cause the channel member'61 to move upwardly into a position in which it lies with its upper surface substantially in"conta'ct with the lower .surface of the sheet metal members 26 and 27 as shown in Fig. 18.

Thesheetmetal covering 67 of the movable nose portion of the aerofoil is secured from the rear of the upper surface of the ribs 31 to a point indicated at 68 ;in Figs. 2

' and 6on the lower edge of the ribs 31, .a-

covering 67 V and to the flanges 72 formed upon thefribs 31. At each of the ribs, the

metal covering is bent upward above the 11 is retracted from the position shown in Fig. 2 to that shown in Fig. 1, the

main surface to a height slightly greater than the combined height of the rib 31 and channel 69, the plate 71 secured to the bottom flanges lying substantially in line with the main surface of the sheet 67. The up,- 70 wardly bent portions of the sheet metal 67 being joined at their upper edges to the channel member 69 by a strip 57,and the channel being secured to the sheets 71 by means of the. ribs 31, and the plates 71 being 75 in turn secured to the sheet 67, all as indieated in Fig. 16, there are produced a series Of strengthening ribs upon the upper surface of the movable nose portion at the location in which the greatest pressure is sustained, and these ribs are in line with the ribs 11 upon the fixed portion of the aerofoil. Additional ribs 73' are formed in the sheet metal 67 between the ribs 31, the ,cross section of these ribs being indicated in Fig. 20. From the point 68 to the rear of the movable nose portion, the metallic sheets 67 are secured together by the interlocking flange connection indicated at 74, 75 in Fig. 15. 'Upon the-under surface of the upper side of the movable nose portion is secured a fmem- .ber 76, (Fig. 19), consisting of a V-shaped forward ends of the sheet metal plates 13 are coiled into the cylindrical form shown ,at 80, the free edge being formed into' a flange 81secured to the inner surface of the plate as shown in Fig.' 19. Plates 14 are turned backward in a similar .fold 82 as shown in Figs. 2, 3 and 4. I

The trailing portion of the aerofoil has sheet .metal covering plates 83 secured to the ribs 42 and 44-from the extryeme rear forward on the top and bottom'surfaces to a point slightly forward of the rear edges of the sheet metal coverings13 and 14 when. the trailing portion-is at its extreme limit of I projection outward. These plates may each consist of a single sheet'of metal folded on 3117 i itself at the trailing'edge. The manner of attaching the plates 83- to the ribs 42 and 44 is clearly shown in Figs. 24 and 29, the con struction bein 'substantially identical withi that shown in ig. 1.7, representing the manner of joining the sheets 13 to the rib 11.

At theirforward ends, the. plates 83 are folded ba'ekwardas indicated at 84 and 85 (Fig. 10) in agalnanner similar to the folding of the edge'r8O shown in Fig. 19. The plates 13 and 14 'are also bentforward in the manner indicated at- 86 and 87 in Figs. 9 and 10 to provide a'smooth flat surface for engagement with'the upper and lower 'surices of th plates 3 as t e tr ilin p so, to which 'is pivoted at 89, a rode90, the opposite end of the rod being pivoted to the bell crank lever 79.

The aerofoil may be made up in a series of panels of which the movable portions are independently movable. In Fi u 8, the end panel may have the bell crank l vers 79 controlling. its nose and trailing portio'ns connected by a rod 91 with a lever 92 controlled by means of a hand wheel 93, and the panel 94 may have its bell crank levers 79 connected by a rod 95 controlled by a hand lever 96 operated independently of the wheel 93. i The operation of these movable nose and trailing portions of the outer panels-to control the. lateral stability of the airplane is explained in detail in my. co-pending application previously herein referred to.

It will be apparent that, since the length of the arms of the bell crank levers 7O differ, the rods 78 being pivoted to the short arms. of the levers and the rods 90 "to the long arms, movement. of the bell crank levers will result in a more rapid projection of the trail- 'ing portion than of the nose portion, and the extent of movement of the trailing portion will be approximately three times that of th nose portion. It will also be seen thatin the retracted position of the nose portionshown in Fig. 3, the rear edges of the sheet metal covering plates 67 lie closely adjacent to the outer-surfaces of the plates 13 and 14," and'that as the nose portion is thrust for? gward to the position indicatedin Fig. 4,the 'i the curve of the guide tracks 37 and 38., so

upper rear edges of the-sheets 67 remain in close contact with the sheets 13, while the. sheets 14: bend downward from a point, a little to the rear of the leading spar 1, so that a substantially continuous curve is maintained upon both the top and bottom surfaces during the entire range of move-. ment of the nose portion.

It will also be observed that the air pressure tends to force the rear end of the sheet metal 67 of the nose portion closelyinto contact with the lower surface of the sheet 14.

The trailing portion in the retracted position lies almost completely enclosed within-the fixed central portion of the aerofoil, a small portion of the lower surface being exposed at the rear while in the closed position indicated in Fig. 9. The rib 4:2 is curved on an arc of a circle concentric with that as .the trailing portion is projected to the rear, the upper surface ofvthe sheet metal 83 remains in close contact with the under surface of the folded portion 86 of the upper sheet-metal covering 13. However since the upper and lower surfaces of the trailing portion diverge at an angle, as

the trailing portion is projected from the position shown in Fig.9 to that shown in Fig. 10, the lower surfaceof the sheet 83 sliding in contact with the upper surface of the folded edge portion 87 of the sheet 14 will cause the sheet 14 to be bent downward in a curve which begins at the point at which the flange 15 of the rib 12 is left free from attachment to the brace member 52. The lowef; surface, of the plates 83 of the trailing portion will be formed on a curve which will be substantially a continuation of the curve formed by the lower surface of the sheets 14, so that the lowers'urface of the aerofoil at the rean has a substantially continuous curvature, the only break inithis curvature being at thepointwhere the folded portion 87 of the sheets 14 holds the sheets 14' a slight distance away from the plates 83. Since the sheets l l'over- '90 lap the lower outer surfaces ofthe plates 83,'pr'essure of the air upon their lower surfaces will tend to hold the sheets l lclosely in contact with the plates 83. To relieve the friction between the lower surfaceof the plate 83 and the folded over portion 87 of the plate 14, the rollers 97 Will be journaled 5 at the rear end of'the ribs 12, these rollers contacting at their periphery with the outer face of the locking strips 57 which hold the sheets 83-within the channeled ribs 14.,

While the spars and ribs and the manner of attaching. the sheet metal plates to the ribs have been shown in detail, illustration of-the drift trussing has been entirely omitted, since this forms no part of the present invention, and may obviously be modified to suit different designs of aerofoils. It will be evident that with the present construction of ribs and spars the attachment of drift trusses may readily be accomplished.

The continuous longitudinal curvature of the upper sheet metal members 13 produces a lateral rigidity of the metal sheets between the ribs which substantially prevents sagging of the sheets transversely between the ribs, whereas in wings having a canvas covering, the tension causes the fabric tocurve inward between the confronting-edges of the ribs to produce'a waved surface. This lateral rigidity of the sheet metal covering produced by its longitudinal curvature materially assists in securing rigidity of the. aerofoil, and decreases. of drift trussing.

The initial wing section in the present metallic construction will be chosen with a top camber upon its upper surface having a curvature at a point substantially midway between the forward end of the nose and the highest ordinate substantially coincident the necessary weight c' with the arc of acircle, and the movable nose section will move forward and downward in an arc of a circle concentric with the are forming a portion of the to surthe nose being such that when the movable nose portion is at its point of extreme forward movement the upper surface ofth aerofoil will be of substantially continupus .10 curvature, "and this curvature will be one which is efficient for slow speed. Consider ingfoml. moment oly the upper surface of .the aerofih-it will be seen thatit will be possiblelto choose an ei'licient camber for high speeds, a portion'of'which will be a substantially circular 'arc and that by extending the upper surface of theaerofoil along the circular are, for a limited distance, a new curvature mayfbe obtained adapted for the upper surface of an 'aero foil efiicient for flight atslow speed.- Considering the upper surface of. the trailing portion of the aerofoil, it will be seen that when the movable trailing portion 2 is projectedalong an arc of acircle con-x centric with the; curvature of the guide tracks controlling this m'ovement, there will be a slight discontinuity of curvature at the point which forms the trailing edge of the aerofoil in its initial position, with the mov- 'of the double camber apparently being to able trailin portion fully retracted, but this double cam r'toward the rear of the trail- 111g portionhas been found to produce an eflicient chamber for slow speed, the effect assist impreventing movement of the center of pressure with 'changingangle of incidence.

Considering the, lower surface of the aerofoil, it will be seen that a" relatively high e -.ca.niber suitable for slower speeds may obtained with substantially no'discontinuity of curvature by providing a fixed central portion having flexible covering plates at the frontahd rear of the fixed portion, the vflexure of which will be co-incident with .t the downward and outward movement of A "the nose, and 'trailingportions, and that the curvature of the flexible metallic covering a curvature for the lower surfaces of the aerofoil, suitable for bo-operation with'the making the lower surface ofthe trailing portion of the curvature selected and. then curvature obtained upon the upper surface -by the extension of the movable nose and trailing portions, this curvature of the "lower surface may readilybe producedby causing the curvature of the flexible cover- 2: ing sheets connecting the trailing portion with the fixed centralportion to assume forming the lower'portion of the initial sec-' ment of the rigidity of the supporting ribs,

this adjustment of rigidity being attained by suitablyvarying the width of the flanges; I face, the shape of the forward portlon of; f

upon theupper surface of the ribs.

A curvature for the lower surface of the aerofoilfwill be chosen such that a portion somewhat in advance of the center of the chord will be co-incident ,with the curve tion. The curvature of the lower portion v of the nose will be one which'will produce an eflicient section for the nose ortion in either its projected or retracte position. The lower surface 'of the trailing portion can of course be made of any desired configuration, and the spaces between the m'o'vable nose andtrailing portions and the fixed central section will'be bridged by flexible sheets, the curvature of which maybe re u-, 'lated by proper adjustment of the rigidity of the supporting ribs at various points throughout their length. a

.By the structure herein described, anin crease in area may be obtained amounting toupwards of thirty-three per cent without undue increase in weight,.and furthermore this increase in area, while'giving increased lift, is not, attended by discontinuity of curvature and loss of efficiency as in certain devices hitherto proposed. The change in camber which in certain other types of variable camber aerofoils is attended by great increase in resistance, isin the present device produced with a-minimum'discontinuityof curvature, with an increase in area, and with an increase in the angle of incidence, all of which produce increased lifting power, while avoiding an accompanying change in the angle of the axis of the pro maximum ordinate, in the position in which the nose and trailing portionsare fully extended, lies at about the same percentage of the chord-from the fro t as the maximum-ordinate lies when the aeiofoil is in the configuration produced by theretrac' tion' of the movable portions. The center ofpressure will thus not be moved reatly tothe rear-because-of thegreater pro ection of the trailing portion, and this tendency. to rearward movement will be balanced by the tendency to 'forward .moveme'nt of the center of pressure due to the increase of the angle'ofincidence. f Not on' l has :the angle of incidence been changed, but the chord' has been increased and the camber. 'greatly' .modified so fthat with the increase in area and deep'ing' of.

the camber, in addition to lt he' increase .in angle, the lift has verygreatlyincreased while the center offpressure has remained spect to the'centerof-gravity of the machine,

,- atfsubstantially the same position witlrirei,

Complete projection of the trailing por tion lowers its rear edge below the lower edge of the nose portion to increase the angle of incidence by about four degrees in the configuration shown, without changing the angle of the fuselage- This angle of incidence may of course be increased in the usual way by tilting the fuselage unti1 the desired lift is reached, but the amount of tilt necessary will be approximately onethird less than if the wing had no outwardly extensible portions.

For climbing, the aviator may start from rest with the nose and trailing portions fully retracted to decrease the resistance to the minimum This will give the high speed section with the minimum camber and the minimum angle of incidence. Thus theairplane may quickly attain such speed in running along the ground for a short distance that if the nose and trailing portions are rapidly projected, the increased area, increased camber. and increased angle of incidence will produce substantially instantaneously a sufficientlift for take-off at the speed already attained, thus shortening the necessary travel along the .groundfl After the airplane has reached a sufiicient height,- the movable nose. and trallmg portions of the central panel or panels of the aerpfoil will be retracted without changing the position of. the movable portions of the outer wing panels. The central portion of the aerofoil' will thus assume a camber for higher speed, and as the speed increases,

' the operator maymove the lever to retract the movable portions of the outer wing panels to the fully retractedposition, so that the enti're-aerofoil will be given the most eflicient camber for high speed. At the same time, lateral stability may be obtained by such slight anovements of the controlling means as are necessary to project the mova ble portions upon either wing to vary the lift.-

For landing, the nose and'trailing portions will be brought to the fully projected position, giving an increase in wing area of approximately thirty-three per cent with the sections herein illustrated. At the same time the fuselage will be given the necessary tilt to produce/the angle at which the lift is greatest.

After the'wheels have come into contact with the ground, the nose and trailing portions will be retracted to decrease the lift,

and thus the weight of themachine will be thrown upon the wheels, whereby brakes upon the wheels will be rendered more efficient. if however the aviator wishes to utilize the resistance due to the large wing area at a high angle of incidence to check movement under favorable wind conditions, the

movable portions maybe leftprojected to their outer, limit, with the aerofoil tilted to the maximum angle of incidence.

From the foregoing description, it will be apparent that there has been provided an aerofoil in which the stream line of the cambered surface is not maintained, but in which the configuration is varied from a form efficient for high speed to a form efficient for high lift at low speeds. The variation in the chord produced byretraction of the movable portion will of course cause a change in the aspect ratio,'the higher aspect ratio at high speed and at low angles giving a :better lift/drift ratio, while the cuvature of the upper surface of the trailing portion is not similar to that of the top of the fixed section, but is an arc of a circle, and while the curvature is not main tainml as the trailing portion is projected, actual wind-tunnel test-s have also demonstrated that the double'camber of the upper surface produced when the trailing portion is projected is highly efficient. These tests have also demonstrated that the camber of the upper surface of an aerofoil may consist in part of arcs of circles at the forward and real; portions in a highly efiicientsection.

It will be obvious that many changes may be made in the details of construction of the various portions of the airplane with changes in design without departing from the principle of the invention herein set forth or sacrificing any of its advantages.

The invention is therefore claimed broadtions of said plates in interlocking engagement with the channel walls.

2. An aerofoil having a member of channelform in cross section, a pair of metal covering plates having their adjacent edge portions folded over the side walls of said channel and extended within the interior of 1.15

said. channel, and'a removable locking strip in said channel holding said edge portions with said channel wall within said channel.

3. An aerofoil having a member of channel form in cross section, the free edges of the sidewalls of the channel being bent inwardly of the channel to form inwardly extending flanges, a pair of sheet metal covering plates having their adjacent edge portions inbent into the channel, and around the free edges of said flanges, and alockin strip having portions disposed within the channel to 'hold said'edge portions interlocked with said flanges.

4. An aerofoil having a member of channel form in cross-section, the free edge porwithin the channel engaging the edge por-- tions of the plates engaged around the flanges to prevent withdrawal of the sheet metal plates and spreading of the channel.

5. An aerofoil having a member formed of sheet'metal bent into channel form in cross sectipn,the'free edge portions of the side walls of the channel being inbent to form flanges extending substantiallypar allel with each other within the channel, a pair of covering plates of sheet metal having their adjacent edge portionsbent inwardly between the flanges and around the free edges thereof, and a locking strip within the channel, said strip having portions engaging between said flanges and between said flanges and the side walls of the channel to prevent separation of the flanges.

6.. An aer'ofoil having a rib cap-member of sheet metal formed as a channel, the free edges of the sheet metal being formed as flanges extending toward the interior of said channel and the metal of said capmember upon the side of the channel opposite said flanges being folded to form a flange extending centrally of the back of the channel and longitudinally thereof.

- 7. In anaerofoil, a rib cap-member formed as anbpen channel,the metal at the open side of the channel being provided with flanges extending toward the interior of the channel andthe opposite outer surface of the channel being provided with a central flange in said channel, and a brace member having terminal portions engaging opposite sides of 'the central flange and secured thereto.

8. In an aerofoil, a sheet metal member of V channelform in cross section with the edge portions of the side walls of the channel extended inwardly of the channel and partially closing the open side of the channel, sheet metal covering plates having their adjacent edge portions inbent over the inwardly, extending. edge portions of said channel walls within the channel member, and a locking strip fitting within and filling the channel and held therein by said inbent edge portions of said channel walls, said strip being endwise removable from said channel to release said edge portions of said plates.

9. In an aerofoil, a member of open channel form in cross section, the free edge portions of the side walls of the channel being extended inwardly toform flanges extending toward the interior of the channel, sheet metal covering plates having their free edges bent'upwardly and around.the free edges of said flanges within said channel, a locking'strip fitting within said channel and formed with a-portion extending between said flanges through the open side of metal covering plate having its edge secured within the channel in the said cap-member, said cap member having a longitudinal flange at substantially right angles to the covering plate, said flange varying in width longitudinally of the rib cap member whereby to provide varying resistance to bending 0% the cap member and of the metal covering ate.

1 11. In an aerofoil wherein a metallic covering plate is flexed during change of section of thevaerofoil, a; member secured to said plate having a. flange at substantially right angles to said plate, said flange being of graduated dimensions to provide unequal resistance to flexure whereby the curvature of the plate is graduated.

12. In an aerofo-il, a sparcomprising sheet metal side and edgeportions, a channeled rib cap-member mounted transversely of the edge portion of said spar, with the surface of the rib cap-member opposite the open side of the channel lying in contact with the edge portion of the spar and secured thereto.

13. In a-metallic aerofoil, a spar, a rib cap-member of channel form in cross section having alongitudinal flange extending out wardly from the bottom wall of "sald chan- "nel, said cap-member lying transversely of said spar, said rib being cut away opposite said spar to permit the closed side of said channel to contact and be secured to the spar, and a brace member within the angle between said cap-member and spar consisting of a sheet metal plate folded upon itself to form substantially parallel members embracing said flange and secured thereto, said brace member being also provided with flanges engaging "the spar and secured thereto. I

. 14. In a metallicaerofoil, a spar comprisingsheet metal side plates, an upper plate and a lower plate, said upper and lower plates having flanges engaging the edges of said side plates, channeled metallic rib capmembers mounted transversely of said upper and lower plates with the surface of the .channeled cap-members opposite the open neled cap members having flanges on the side opposite the open channel, said flanges tern'nnating upon opposite sides of the spar,

and brace members secured tothe side plates of the spar and to the flanges of the channeled cap-members.

15. A structure as in claim 14, in which the spar has an interior base member consisting of a sheet of metal secured to the inner faces of the side plates opposite the point of attachment of said first mentioned brace members.

16. A metallic aerofoil comprising a metallic spar, a metallic channeled rib capv member secured thereto and extending rearward, a metallic rib member also secured to said spar and extending forward and a second channeled ,rib cap member secured at its rear end to said rearwardly extending rib cap member and lying beneath said forwardly extending ri b cap member, and sheet metal covering plates engaging withinboth of said channeled members.

1.7. A metallic aerofoil comprising ametallic spar, a metallic channeled rib capmember secured to the spar and extending beyond the same, metallic rib trussing forming together with the cap-member a rib secured to the spar and extending beyond the .same, a movable ribportion beyond the spar, guide rollers carried by-said movable rib portion, a track for said rollers upon said extended portion of said fixed rib, said track having its curvature disposed to cause upward and downward movement of the movable portion of the rib, said movable rib portion having engagement with a free end comprising fixed and movable portions, said portion of said cap-member, whereby the same is flexed by the movement of the movable rib portion. I

V 18. In an aerofoiL'a metallic, rib member fixed portion being formed with a channeled portlon, with the edges of the channeled portion forming a guide track adapo ed for engagement with guide rollers, and

said movable portion of said rib member being provided with a bracket portion carrying grooved guide rollers journaled thereon to engage said guide tracks.

19. In an aerofoil, a rib member comprising a fixed portion and a movable portion, said fixed portion including oppositely arranged sheet metal members secured together and having portions of their confronting surfaces formed into curved channels, the inner edges of the channels constituting curved edge tracks adapted to be engaged by diametrically opposite portions of grooved rollers, and said movable portion of the aerofoil having grooved rollers engaging said curved guide tracks. 1

20. In an aerofoil, a fixed portion and a movable portion, said fixed portion having a channeled part, theedges of the channeled "whereby during movement of the movable portion guided by the engagement of the rollers with the guide tracks, the distance between the metal covering plates upolr'said fixed and movable portions will remain substantially constant. I

21. In a metallic aerofoil, a movable nose.

portion having sheet metal cap members, a

channeled rib member supported upon the upper edges of said'sheet metal cap members, sheet metal covering'plates bent upwar'd adjacent to their meeting edges and having their free edges secured within said channeled cap members, and a strengthen ing plate secured to the sheet metal rib members and to the covering plates, the strengthening.plate together with the upwardly bent portions of the covering plates and the cap members constituting curved strengthening ribs elevated above the general surface of the sheet metal covering plates.

22. A metallic aerofoil provided with a movable nose portion and a movable trailing portion, each portion having means 1 whereby it is guided outward-and downward in a curved path; the rear part of the upper surface of the nose portion and the upper surface of the trailing portion being substantially concentric with said curved paths respectively whereby the rear edge of the movable nose portion and the rear edge of the relatively fixedportion 'are maintained at substantially equal distances from the upper surface of the relatively fixed portion and the upper surface of the movable trailing portion, respectively, during movement of the nose and trailing portlons, the lower surface of said movable 1 nose portion overlapping the flexible metal plates constituting the lower surface of the relatively fixed portion and having sliding connection therewith, and the lower surface of the trailing portion pressing down upon the flexible plates constitutin the lower rear covering of the relatively fixed portion, whereby" forward and downward movement of the nose portion and rearward and downward movement of the trailing portion'will cause flexure of the lower metalhc. covering plates to form a substantially unbroken curve from theitip of the noseto the rear edge of the trailing portion on the top and bottom surfaces of the aerofoil.

23. An aerofoil comprising a fixed or tion and a movable portion forming an edge portion of the aerofoil, metallic covering plates secured to said fixed portion throughout a part of the length of said fixed portion and free therefrom adjacent 'the movable portion of the aerofoil, said plates forming the lower covering of the aerofoil, and plates secured .to the movable. portion to form the lower surface thereof, the adjacent edge portions of said plates on the movable portion and the unsecured edge portion of the plates on the fixed portion being in overlapping relation, said movable portion being movable downwardly to change the camber of the aerofoil and to fiex the unsecured portion of said plates to change the continuous curvature to the lower surface of the aerofoil.

24. An aerofoil having metallic covering plates upon its lower surface connected at their adjacent edges by flexible metallic rib members, said rib members being rigidly secured at their forward end and free for downward movement at their rear end, each depressed.

25. An aerofoil having a fixed win'g portion having a constant top camber and a variable bottom camber, and having a flexit moves outward tocause itto curve doWnwardly, the flexibility being graduated to predetermine the curvature at various points of outward movement of the trailing.

portion.

26. An airplane having an initial contour designed for high lift/drift ratio and having forwardly and rear'wardly slidable portions, the front portion being slidable over a fixed portion, the rear portion being' slidable within the fixed portion having a flexible lower covering, each movable portion engaging the flexible lower covering of the fixed portion to causedownward curvature thereof at front and rear, whereby to cause a change of section from an initial highspeed section to an efiicient low-speed section of greater area, and deeper camber.

In testimony whereof I alfix my signature in presence of two witnesses! JOHN F. COOK, JR. Witnesses:

ARTHUR MINNICK, G. L. TERRA.

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