Патент USA US2113000код для вставки
April 5, 1938. , ~ D. c. ROWE, 2,113,000 ANTIFLUTTER DEVICE Filed May 17, 1933 F162. INVENTOR. DONALD C . ROWE. 2,113,000 Patented Apr. 5, 1938 um'rsn STATES PATENT OFFICE Donald C. Rowe, Kenmore, N. Y., assignor, by mesne assignments‘, to Curtiss-Wright Corpo ration, a corporation of New York Application May 1'7, 1933, Serial No.‘ 671,470 17 Claims. (CL 244—75) the annexed specification and claims, and in This invention relates to aircraft, and particu larly. to means for overcoming inadvertent ?utter considering the drawing, in which, similar num bers designate similar parts, and in which: in control surfaces thereof. In the recent development of high speed air- ' Fig. 1 is a. side elevation of 'the empennage of an airplane embodying the invention, ca 5 craft, a phenomenon commonly known as "?ut Fig. 2 is an enlarged section on the line 2-2 ter” has sometimes appeared in the .control air- A foils, such as ailerons‘, rudder and/or elevators. of Fig. '1, showing, in dotted linespcertain of the elements in different positions of adjustment, The effect of ?utter is to‘impose severe stresses Fig. 3 is a cross section througha brace wire on the aircraft structure with possible failure 13 resulting, and may also have the e?ect of im pairing the controllability of the aircraft. The basic reasons for the phenomenon have not been having‘ an auxiliary airfoil attached thereto, and 10 Fig. 4 is a cross‘ section through a streamline strut having an auxiliary airfoil attached‘ there fully determined,>but certain curative practices have been evolved which, when applied, appear 15' to assist in eliminating flutter. to. ' v ' ‘ Describing the invention in detail, In is an air Some of these" plane fuselage having a vertical ?n H, and a_15 horizontal stabilizer l2. ‘At the trailing edge-of practices include‘ lightening the affected parts, the ?n II, a rudder I3 is pivoted, as at M, for forward of its pivot axis, and eliminating slack‘ swinging movement subject to the action of con ventional rudder controls 15. The line a,--a des and lost motion in the airfoil hinges and actuat locating the center of gravity of a control airfoil ing members. _ 2 " ignates the rudder. pivot axis, which may be rear- ' 0 The subject invention provides. fully automatic " ward of the leading edge l6 of the rudder, or means for damping and eliminating control air foil ?utter, and comprises brie?y an auxiliary air ‘ foil hinged to the control airfoil rearwardly. of 25 the control airfoil pivot. Thejauiliary airfoilis arranged with its center of gravity forward of its may be at any other convenient location with respect ‘to said leading, edge. Suitable brackets ii, attached to'the. ?n I I, carry the rudder pivots. Toward the trailing edge I8 of the rudder l3, 25 a cutout I9 is made,’ and hinges 20 are arranged on an axis b-b to carry'an'anxiliary airfoil 2i. Said airfoil 2| ‘extends rearwardly from the hinge, moments for the control airfoil in a manner to be axis 17-17, and is freely swingable to either side of the plane of symmetry of the rudder l3. It‘will 30 30 more fully described hereinafter. _ . A somewhat similar and related phenomenon be noted-‘that, since the bulk of the surface of the to control surface ?utter is the vibration in ?ight airfoil 2! is rearward ofv the axis b--b, the center of exposed brace wires and long exposed=~struts. of pressure of air acting thereon will likewise be The invention also provides means for damping rearward of said‘ axis,‘ To place the center of gravity of the structure of.‘ the airfoil ~2l forward, Li vibration in such members’. Objects of the invention are to provide means of said hinge axis b--b, an arm_ 22, carrying for eliminating control airfoil ?utter; to provide a weight 23 at its forward wencLextends for; a, freely swingable ‘auxiliary airfoil hinged to a, wardly-of the axis b-b, and is rigidly attached to the airfoil 2|? Alternative means will be ap control airfoil; to provide a hinged airfoil hav 49 ing its center of gravity forward of the hinge ‘parent to those‘skilled in the art for carrying 40 axis; to provide a hinged airfoil having the major the center of gravity of the airfoil 2|‘ forward'of . _, v part of its air contacting surface rearward of the hinge axis b--b. " _ The operationfof the devicemay be more readily its hinge axis; and to provide an airfoil.- which - 'by its inertia, tends to damp ?uttering tendencies. understood by referring to Fig. 2. The position C shows the rudder l3 and the auxiliary airfoil 2| 45 01 Related ,objects are to provide auxiliary airfoil‘s, ' hinge axis, and with its center of pressure rear ward thereof, which, in action, providesdamping 4 ‘vi either fixed to or hinged to other aircraft meni bers which may be‘subject to vibration or ?utter,» , to damp and eliminate such vibration or ?utter. In such auxiliary airfoils, the principles are iden- ' I 50 tical with the airfoils as applied to control sur- faces; namely, the center of ‘gravity of the airfoil is ahead of the member,- or ahead of the point of attachment of‘ the, airfoil, ‘ while ' the center of pressure is rearward thereof; ' ' . 55 vFurther objects will be apparentv in reading in alinement, which would be their normal posi tion. ' Should the'rudder to ?utter, that-is, be moved by forces othenthan those imposed-by the pilot of the'aircraft on‘the controlsrliitj will movequickly to some displaced position such‘ 50 as D. When this occurs,v the‘ surface of the auxiliaryairfoil 2! will tend to be displaced at a greater angle‘than the rudder; due to the weight of saidairfoil acting forward of“ the axis b—-b, which weight, by inertia5 resists displacement.._f55' 2, a,11a,'000 Hence, the airfoil 2|, addressedbythe air stream, exerts a steering effect on the rudderi I, tending from the spirit or scope thereof. , I aim iii the ap pendedolaims to cover all such‘modifications and to move it back to the plane of symmetry or to - position C. -As suchv movement occurs, the rud-l "der It and airfoil 2| will assume a position such -as E, wherein the rudder is moving'toward the 10 plane of symmetry, but the‘airfoil 2| has, by its inertia, moved in oppodte angular sense. to the rudder, since the center of gravity thereof is forward of its hinge axis. Hence, the air stream ‘then acts on the opposite 'side of the airfoil 2|, ‘ counteracting in some degree the restoring tum ing moment initiated in position D, thus damping movement of both the rudder i3 and the airfoil 2|, preventing repetitious oscillation of either, and gradually returning both, “their positions in the 15 aircraft plane of symme . Iclaimss'my invention: _ ~ ‘ ,~ 1“. ,In aircraft ‘having a cont ml airfoil "movable about a pivot,_an auxiliary airfoil freely movable about a hinge carried-on said :control airfoil, said auxiliary airfoil having its center of gravity forward 0: its-hinge and its center'of pressure rearward thereof. - . . ' ‘ 2. In aircraft‘ having a controlr airfoil con trollably movable with respect thereto, an aux; iliary airfoil hinged toward the rearward edge of said control airfoil movable with and with respect thereto, having its center of gravity forward of 15 said hinge and its center of pressure rearward of saidhinge. The proportionate size, weight, center ,0: grav-I g ' 3. In aircraft having a control airfoil subject to controlled movement, means for overcoming _uncon'trolled ?utter of said airfoil comprising a 20 statically unbalanced auxiliary airfoil hinged to ?utter oscillation. The above X ctional descrip tion is predicated upon correct _roportions in the I said control airfoil‘jhaving its center of 'avity device, which proportions may be evolved by cal¢. forward of said hinge and its center of pr ssure rearward thereof. , , .. culation and experiment. It will be readily ap 4. In aircraft,_a control airfoil pivoted thereto 25 preciated that the structure and functions above ity location and center of pressure location of the 20 airfoil 2| will govern its effectiveness in damping described may be applied with identical effect to elevators, ailerons, brace'wires, struts or other movable aircraft members. In Fig. 1 the elevator 25, carried by the stabilizer l2, for instance, may so be ‘equipped with an auxiliary airfoil 2|’; an arm 22' and a weight 23', to act in-the same manner as the similar elements 2|,'22 and 23. and extending rearwardly from the pivot, an aux iliary, airfoil hinged toward its forward edge to said control airfoil, the hinge axis being spaced rearwardly from said pivot, and an arm extend ing from said auxiliary airfoil forward of said 30 hinge, the mass of said arm being of a magnitude to-more thancounterbalance the weight of said . auxiliary airfoil rearward of said hinge. _The airfoil 2| as above described, may be either freely swingable to ful?ll an anti-?utter function only, or may be controllable. Fig. 2 shows, in. dotted lines, one arrangement for controlling the airfoil 2|, wherein ‘a horn 24, ?xed to the airfoil, is connected by the rod 25 to a lever 26, movable on the axis a--a. _\ 5. .In aircraft, a vertical rudder pivoted there to, and an auxiliary airfoil hinged to said rudder 35 rearwardly of said rudder pivot for free swing ing with respect thereto, said airfoil having its center‘ of gravity forward of said hinge and its center of pressure rearward of said hinge. lI'his lever may in turn be 6. In aircraft, an elevator pivoted-thereto and 40 "quarters, whereby the pilot may set the airfoil 2| . .an auxiliary airfoil hinged to said elevator rear-4 40 controlled by a rod 21 leading to the pilot's wardly of said elevator ‘pivot for‘ free swinging‘ I at an angle with respect to the rudder l3 for with respect thereto, said airfoil having its cen ter of gravity forward of said, hinge, and trimming yawing tendencies in the ?ight _of the‘ aircraft. _Whether controllable or freely swing able, the airfoil 2| will have the desired effect center of p'ressure rearward of said hinge.- ‘ ‘ 7. In aircraft having a member subject to both‘ When controllable, the in controlling ?utter. control elements, as 24, 25, 26 and 21 will have ' controlled _and- uncontrolled relative movement su?lcient resilience to allow the airfoil 2| to move ’ in ?ight, an auxiliary airfoil for damping the un controlled movement attachedto said member, said airfoil having its center of pressure rear Figs. 3“ and 4‘ show the anti-?utter or anti vibration devices as they ‘may be applied to , ward of its point of attachment, and having 5-0 streamline brace ‘wires onstruts. In Fig. v3, a _means forward of said point of attachment ‘for su?iciently to damp ?utter. locating the 'center of - gravity of said airfoil for wire 28 has attached theretoa small airfoil-2S having a’ main v,portion 31 of light material ex ward of said point of attachment. 8. In aircraft having a member subjectto both 55 tending principally rearwardly of the wire 28. so that .its center of surface area is rearward of the wire. A' nose ll of heavier material forms controlled and uncontrolled relative movement in ?ight,‘ means for damping the. uncontrolled the forward portion ofthe airfoil 20, whereby the movement comprising an element. attached ~ center of gravity of the unit is thrown forward thereto intermediate the width of said‘ ele'ment, said element having its aerodynamic center of 60 of the center of the wire 28. ‘If the wire starts to so move crosswise ofthe airstream, the nose 2| lags .pressure rearward of said point of attachment, by inertia, tilting the airfoil 28 and twisting the . ‘and having. a mass forward, of said pointof at wire 28 to steer the unit. to a neutral position. tachment greater than ‘the mass rearward In Fig. 4, the element 28' may represent a strut thereofii'i- I \ ' 65 or the like which is relatively rigid and not sub ‘ 9.“In ircraft, aj movable element'in the slip it center of gravity theeof. forwardloi' said point 70 65. "ject to twist. Hera/the airfoil 29' is‘swiv’elled~ stream nd an auxiliary airfoil embracing said on the Istrut as at 32L so thatr as the element 28' element having its aerodynamic center of pres _moves crosswise, the airfoil.29' will turn about sure rearward of'its Point of‘; ' tiMTihmentv to said? the swivel 32,- by the inertia of the nose it’, and element, and having’_means fo?e's‘tablishing the steer the strut 2l'lback ‘to a neutral position. . While I have described my invention in detail in its present preferred embodiment, it will be ob vious to those skilled _in the art, after understand 1 ing my invention, that various changes and mod 76 of attachment. _ , ffi_',_l ;_ ' .. I; f ‘ _ 10. In‘ aircraft, an .vauxiliary airfoil, 'and a movable member in'th'e slipstream embraced by‘. . andv attached tos'aid ‘airfoil,;‘ " di'airi’oil having ifications may be‘made'therein without departing 1th center of pressure rearward'gofthe point of 75 2,113,000" ' attachment and having. its center of gravity for-" ' 7 ward thereof.v 1 . I ' g Q I ' ‘ g 3 trolled movement, meana for preventing flutter thereof, comprising an auxiliary airfoil carried 11. In aircraft having a member subject to . thereby and disposed in the airstream, said airfoil ' uncontrolled relative movement'in ?ight, an aux- - iliary airfoil for damping said movement ‘con being hinged to saidyelement and having its cen ter- of gravity forward of the hinge line, and its trolled in its own movanent only by its response . center of pressure rearward thereof. > to air?ow and inertia, pivoted to swing freely on 15. In means for overcoming ?utter in an air and vwith respect to said member, said airfoil craft element subject to controlled movement, an having its ‘center of pressure rearward of said‘ auxiliary airfoil mounted for oscillation on said pivot, and'having its center of gravity forward of said pivot. ' \ ~ - = ' - 1 12. In an aircraft element exposed to the air stream- and subject to movement aboutv an axis element, said airfoil having its center of mass for ward of the axis of oscillation, and having its center of pressure rearward of said axis of oscilla tion. ’ v of oscillation, ?utter'prev'ention means compris-. ' 16. In aircraft, an airfoil subject to controlled ing an ‘auxiliary control surface carried by said movement, an auxiliary anti-?utter airfoil hinged 15 element, said surface having its center of pres--' to said controlled airfoil, the center of gravity '} sure rearward of the oscillation axis of said ele of said auxiliary airfoil being forward of ' said ment', and having its center of gravity forward-of hinge and the center of pressure thereof bei said oscillation axis. rearward of said hinge.‘ 7 g / ' 20 13. In a ‘relatively long slender aircraft ele ~ ' ment exposed to the airstream, means for pre venting inadvertent ?utter thereof, comprising an auxiliary airfoil carried by said element, said airfoil having its center of gravity forward of 25 the center of gravity of said element. and having . its center of pressurerearward of the center of gravity of said element. ' . - 17. In aircraft, a control airfoil pivoted there to, and an auxiliary airfoil hinged to said control airfoil rearwardly of said control airfoil pivot for free swinging movement with respect to the con- - trol airfoil, said auxiliary airfoil having its cen ter of ‘gravity forward of said hinge and its cen 25 ter of pressure rearward of said hinge. ' ’ - - . ‘is. In an aircraft element whim W 9°11" c.