US2352062A - Upper surface flap - Google Patents

Description

June 20, 1944. E. F. ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 15, 1940 '7 Shets-Sheet 1 BY wk A TTORNEY June 20, 1 944. E, F, ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 13, 1940 7 Sheets-Sheet 2 IN VEN TOR.

ATTORNEY June 20, 1944. ZAP

UPPER SURFACE FLAP Filed Jan. 13 I 1940 '7 Sheets-Sheet 3 o 6 T m w 1m E m F. 5

BY fl ATTORNEY June 20, E F ZAP UPPER SURFACE FLAP Filed Jan. 15, 1940 7 Sheets-Sheet 4 EE ZAP,

IN VEN TOR.

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ATTORNEY June 20, 1944. E. F. ZAP

UPPER SURFACE FLAP Filed Jan. 13, 1940 7 Sheets-Sheet 5 E1 ZAP) INVENTOR. BY

ATTORNEY June 20, 1944. E. F. ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 13, 1940 7 Sheets-Sheet 6 o .n- 1 k III-III VII-III III...

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III, n- I" m I ATTORNEY June 20, 1944. ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 13, 1940 '7 Sheets-Sheet '7 wullllll V INVENTOR. I Z: 7728 I A TTORNEY Patented June 20, 1944 UNITED STATES PATENT OFFICE UPPER SURFACE FLAP Edward F. Zap, Los Angeles, Calif.

Application January 13, 1940, Serial No. 313,770

7 Claims.

This invention relates to an airfoil the lift or lift capacity of which as well as its drag can be changed, either throughout the entire airfoil or through the center portion or tip portions thereof.

It is the object of the invention to provide such changeable airfoil having the following advantages: The production of a small lift is associated with a. small drag; the production of a large lift is associated with the production of either a large drag or a comparatively small drag, as desired at any time by the pilot. The airfoil requires small control forces only. The control effects or aerodynamic changes are large. When used for lateral control, the lateral control moment produced by the airfoil is associated with a favorable yawing moment or at least hardly any adverse yawing moment. The improved airfoil is relatively free of icing danger. Th control effect has no appreciable time lag. The airfoil is structurally simple, sturdy, and light, it is mechanically reliable, it affords good access for the inspection of the moving parts, and the latter are well protected against accidental damage.

These objects are accomplished by bifurcating the trailing end of the airfoil, that means giving it two trailing edges one above the other, an upper airfoil lip and a lower airfoil lip, which may be integral with the airfoil or movable relative thereto. A thin movable fiap'is placed into the pocket formed by and between the two lips. This flap extends forwardly and upwardly into the pocket, being spaced from the lower lip, particularly for the high lift condition, affording thereby a good size entrance to the pocket. The fiap is normally in contact with the upper lip, and for the high lift condition is brought into spaced relation thereto, be it by the displacement of the flap, by the displacement of the lip, or both. An air passage between the flap and the airfoil is thus formed. The flap cooperates aerodynamically with the upper airfoil surface, its airflow-exposed portion being in continuation thereof.

The simpler embodiments of my invention, with fixed lips and simple fiap motion, confer appreciable benefits on the air-place, and elucidate the broad principles involved. It is contemplated to employ movable lips together with composite fiap motion, in order to obtain the highest efiiciency. It will also be explained and illustrated how the invention may be combined with a. two way exit slot as described per se in my pending applications Ser. Nos. 195,381 and 292,726.

This will now be illustrated and described in the accompanying drawings and the following specification.

Since the underlying principles '5 may be incorporated in still other specific devices, it is not intended to be limited to the ones here shown, except as such limitations are clearly imposed by the appended claims.

In the drawings, like numerals refer to similar parts throughout the several embodiments and views, of which Figs. 1 and 2 represent cross sectional views taken vertically and in the direction of flight, of an airfoil incorporating the invention, Fig. 1 represents the flap retracted and Fig. 2 represents the flap extended into its high lift position.

Figs. 3 and 4 are like views of a second embodiment, in which the upper lip is elastic.

Figs. 5 and 6 are like views of a third embodiment, in which the flap is shaped different from that in Figs. 1 and 2.

Fig. 7 is a like view of a fourth embodiment with the flap being mounted in a different manner,

the full lines indicating the low lift position of the flap, and the dashed lines its high lift position.

Figs. 8 and 9 are like views of a fifth embodiment, the fiap being differently constructed.

Fig. 10 represents a plan view of the airfoil as seen from top, showing the application of the invention for lateral or aileron control.

Figs. 11 to 13 represent in cross sectional View taken vertically and in direction of flight a sixth embodiment of the invention, in which for the low lift condition a trailing edge van-e closes the gap between the flap and the lower lip. Fig. 11 corresponds to the landing condition, Fig. 12 to the take-off condition, and Fig. 13 to the low lift and high speed condition.

Figs. 14 to 16 represent in like view a seventh embodiment, in which a forwardly or rearwardly opening slot is provided in association with the upper lip. The flap vane is movable independent-1 1y of the flap motion. Fig. 14 shows the flap retracted, Fig. 15 is equivalent to aileron up," and Fig. 16 to aileron down."

Figs. 17 to 20 represent in like view an eighth embodiment in which the flap is mounted for composite motion and the two lips are movable. Figs. 17 and 18 show the flap retracted, with the upper lip in different position. Fig. 19 shows the flap extended, and Fig. 20 shows the flap extended and deflected.

Figs. 21 and 22 represent in like view a ninth embodiment in which the flap is mounted for single motion, and the two lips are independently movable. Fig. 21 shows the flap retracted, and Fig. 22 shows the flap extended.

Referring now to these drawings and particularly to Figs. 1 and 2, numeral ll denotes broadly a major fixed airfoil, to which is hinged a. flap 20 at the hinge 2|. The airfoil contour or profile shows a convex leading edge l4, a convex evenly rounded upper camber line I2 and a similar,

convex, evenly rounded lower camber line l3.

upper and of the lower airfoil walls or coverings respectively suitably braced and stiffened as by ribs 28, or elastically or movably mounted or fastened, as will be illustrated with reference to the different embodiments. In the first embodiment, Figs.1 and 2, both lips are rigid and fixedly mounted.

The upper lip and the lower lip form and enclose a rearwardly open spanwise extending pocket 22. Front portion 24 of flap 20 is positioned within pocket 22, its rear portion ex-' tending out into the open space behind the pocket. For the low lift condition, the rear, airflow-exposed flap portion 23 is in line and flush with the upper camber line [2. At the trailing edge 25 of the upper lip IS, the fiap 20 makes tight contact with the air-foil. Front flap portion 24 is positioned within the pocket between the upper and lower lip. The flap is held and stiffened by flap ribs 33 which extend to a hinge point 2| about which the flap is rotatable. By means ofthat hinge, the fiap is mounted on the lower lip l'l. Reciprocating control push-pull rod 30 hinged to the flap at 3| is subject to the pilots manipulation in any conventional manner not shown, and constitutes control means for turning the flap into different positions relative to the airfoil ll. Thus, a rearward motion of push-pull rod 30 turns flap 20 rearwardly as well as down, from the low lift position Fig. 1, where the trailing flap edge 26 is in line with the upper and lower camber lines l2 and I3, 26 being on the geometric line 29 forming a geometric projection or extension of lower camber line l3, into the high lift position Fig. 2, trailing edge 26 then being positioned below the extension line 29 of the lower camber line. It will also be noted that rear flap portion 23 is then downwardly and rearwardly inclined relative to the upper camber line l2, as shown in Fig. 2, whereas in Fig. 1 it is in line therewith.

The arrangement of Figs. 3 and 4 differs from that in Figs. 1 and 2 by that the rigid upper lip I9 is replaced by an elastic upper lip I8, made of thin metal or other sheet, and fastened to the rear spar I6. The forward flap portion 24 is provided with projections or teeth 21 near its leading edge, which in the low lift position Fig. 3 are spaced from lip l8 and positioned within pocket 22. If the rear portion of the flap is turned down, its front portion together with teeth 21 is lifted up, and said teeth make contact with the upper lip l8, whereby the teeth deflect the upper lip upwardly from its low lift position. Thereby. a narrow rearwardly opening slot 40 is formed between the upper lip and the rear flap portion, which slot connects the space above the airfoil with the pocket 22. Air will then enter into the pocket from below, through the gap between the trailing edge of the lower lip I! and the flap, and will leave the pocket in rearward fiow through the slot 40. I have found that this has a distinctly beneficial effect on the aerodynamic force created.

In the airfoil variation shown in Figs-5 and 6, the same opening and closing of the slot is obtained with a stiff or rigid upper elastic lip, the lip being in that respect like the one shown in Figs. 1 and 2. The front flap portion 24 joins the rear flap portion 23 with a sufficiently curved bent slot to effect the opening of slot 40 by virtue of its shape as the fiap is moved backwardly from lip edge 25, and to effect a closing of slot 40 as the flap 20 is moved forwardly towards and into contact with the upper lip 19.

In the arrangement of Fig. 7, the opening and closing of the slot is effected in exactly the same manner as in the variation just described. This arrangement differs from the one of Fig. 5 merely by the position of the axis of rotation of the flap. This axis is now positioned below the airfoil, at a point designated by 2|. The flap is held by rollers 5| and 52 guided in a bent slot 53 spared out of a rigid wing rib. Of course, any other supporting and moving arrangement adapted to make the flap movable in the manner described would equally well serve for taking the invention into use.

Thus, in Figs. 8 and 9, a stationary, spanwise extending, fixed flap support is shown. This support 50 is fastened to the airfoil structure, and serves as a stationary flap portion. Flap 20 is held by rollers 5i and adapted to slide on top of and along flap support 60. Support 60 is separated from the upper lip l9 by the slot 40. In the low lift position, flap 20 is moved rearwardly as shown in Fig. 9, and slot 40 is open. Air enters then from below through the gap between fiap 20 and/or support 50 and lower lip I1 into pocket 22 and is discharged rearwardly through slot 40.

The following figures illustrate more elaborate embodiments of my invention for utmost aerodynamic efficiency at the cost of some structural complications. In the embodiment of the invention, Figs. 11 to 13, upper lip 50 is not rigidly fastened to the airfoil but it is hinged thereto about a spanwise axis or hinge 49. The rotatable upper lip 5i!v is provided with a horn 54 to which is hinged the push-pull rod 55, which in turn is under the control of the pilot in any conventional manner not shown in the drawings. This brings about that theslot 40 is separately under the control of the pilot which makes the airplane more maneuverable. If upperJip 50 is displaced from its neutral position represented by the solid line in Fig. 12 through a large angle of displacement say into the position represented by the dotted line of Fig. 12, the lip vane 50 acts as a spoiler, diminishing the lift rapidly and thoroughly; this provides a welcome means for assisting the landing. If the same lip vane is displaced through a small angle of displacement, in combination with the high lift position of the flap, as shown in Fig. 11, the lift is increased in that so-called stalling or burbling of the airflow is delayed to a larger angle of attack. In the arrangement Figs. 11 to 13, a separate control for the lip vane and for the flap, in all two separate controls for the mechanisms shown, are contemplated.

In the same Figs. 11 to 13 there is furthermore illustrated use of a flap vane 4|, hinged to the flap along the trailing edge 26. A guide rod 43 rigidly fastened to flap vane 4|, extending therefrom forwardly, is provided for securing the de-- sired angular position of the flap vane. This rod 43 has at its forward end a guide pin 44, which 'in its turn is in operative sliding engagement with guide slot 42, spared out of an airfoil rib. Slot 42 is shaped to turn vane 4| into close contact with flap 2!! flush thereto for the high lift position illustrated in Fig. 11; flap and vane forming then in effect together one unitary sheet. At the low lift position Fig. 13, vane 4| declines relative to the flap, contacting the lower lip flush therewith, and closing the gap between the flap and the lower lip. This improves the streamlining for the low lift (high speed) condition and diminishes the drag or air resistance. In the arrangement Figs. 11 to 13, no separate control for the flap vane is contemplated, but the flap and vane move together in linked relation, so that every flap position is associated with a predetermined flap vane position.

In Figs. 14 to 16, showing the low lift position of the flap only, an even higher degree of refinement is illustrated. The upper lip vane is constructed to either close the upper gap, or to open a rearwardly open slot (Fig. 16), or to open a forwardly open slot (Fig. 15). This is achieved by employing a doubly opening vane 35 having an inwardly extending born 38 and a pushrod 39 hinged to the horn. The detail of the mechanism including means for mounting and fastening the vane 36 is not shown, as the same is already disclosed in my copending application Ser. No. 195,381 and Ser. No. 292,726.

Flap vane 4| is'likewise separately controlled. The guide slot 45 is now spared out of a separate guide piece 56 hinged at its rear end 51 to the airfoil structure. Guide piece 56 can be turned by means of bell crank 46 mounted on the airfoil structure at 41; the one bell crank arm engaging the guide piece and the other bell crank arm being hinged to push rod 48, said rod being under the control of the pilot in any conventional manner not shown in the drawings. As the guide piece 56 is deflected, flap Vane M is likewise turned, even while flap 20 may remain stationary. It must be clearly understood that the embodiment Figs. 14 to 16 requires three different and separate controls for the movable surfaces shown, one for moving flap 20, through pushrod 30, one for moving flap vane 4|, through pushrod 48 and a third for moving the upper vane 36 through pushrod 39. It is however feasible to reduce the number of controls needed by interlinkage. Pushrods 48 and 39 can for instance be linked together, and employed together for aileron or lateral control. The flaps are then arranged as schematically shown in Fig. 10, and the control action on the right wing and on the left wing is counterwise as with ordinary ailerons.

Fig. 1'7 to 22 illustrate a flap with composite motion, both lips being tiltable, and the lower lip being linked to the flap motion mechanism. Flap 20 is provided with a plurality of roller guide channels 65 in engagement with and held by rollers 63 and 64. These rollers are mounted on flap support Bl, which support in turn is hinged to the stationary airfoil structure at 62. Flap support horn 66 connects to the control gear by a push-pull rod hinged thereto and not shown in the drawings. Lower lip I1 is hinged at 61 to the lower airfoil surface. It is linked to the flap support 6| by means of link members 68 hinged at one end to the flap support and at the other end to the lower lip ii.

The flap can thus be moved into three principal positions, (a) flap retracted, Figs. 17 and 18, (-b) flap extended but not deflected, Fig. 19, the

flap support being still in its neutral position as in Fig. l! and accordingly the lower lip too, and (c) the flap extended and deflected, the flap support being turned down and the lower lip likewise by virtue of the linkage through member 68.

Figs. 21 and 22 illustrate a flap mounted slidably on a stationary flap support for single motion. Both lips can be tilted independently of each other and of the flap motion. The rollers 63 and 64 are now mounted on the stationary flap support 69 and are in engagement with the roller channels 65 fastened to the flap 20. Lower lip l1 consists of a vane hinged to the stationary airfoil structure at 10, and a push-pull rod (not shown) is hinged to the lower lip horn l l.

The last described two arrangements are very suitable for use as high lift device in combination with aileron use by means of counterwise control at the wing tips as schematically illustrated in Fig. 10. The different positions of the upper lip and of the flap in combination with the lower lip are as follows:

I. Normal flight: Flap retracted.

Ia. Aileron neutral: Upper lip closed, as in Fig. 17, upper lip in dotted line.

Ib. Aileron up; Upper lip all way tilted, as Fig. 17, upper lip in solid line.

10. Aileron "down: Upper as Fig. 18.

II. Take off and climb: Flap extended but not deflected.

IIa. Aileron neutral: Upper lip closed.

IIb. Aileron up: Upper lip all way up, as Fig. 19, upper lip in solid line.

He. Aileron down: Upper lip partially opened, as Fig. 19 upper lip in dotted line.

III. Landing condition: Flap extended and deflected.

IIIa. Aileron open, as Fig. 20.

I111). Aileron up": Upper lip all way up.

IIIc. Aileron down: Upper lip partially open, as Fig. 20.

lip partially tilted,

neutral: Upper lip partially I have obtained best results by making the v flap chord from 20% to 25% of the airfoil chord. In the high lift position, the upper lip should overhand the flap by not less than 2% of the chord, and the slot 40 should not be narrower than 2% of the chord.

I claim:

1. In an aircraft, an airfoil with continuously curved upper and lower surfaces terminating in a trailing substantially spanwise extending rearwardly projecting upper airfoil lip and in a trail,- ing substantially spanwise extending rearwardly projecting lower airfoil lip, a substantially spanwise disposed than the distance between the upper airfoil lip and the lower airfoil lip, movably mounted behind the airfoil and in all positions partly within the pocket formed by and between said upper airfoil lip and said lower airfoil lip so that the leading edge of the flap is forward of the two flap much thinner throughout I foil lip and in contact curved upper and lower surfaces terminating in a trailing substantially spanwise extending rearwardly projecting upper airfoil lip and in a trailing substantially spanwise extending rearwardly projecting lower airfoil lip, a substantially spanwise disposed flap much thinner throughout than the distance between the upper airfoil lip and the lower airfoillip,rotatablymounted behind the airfoil and in all positions partly within the pocket formed by and between said upper airfoil lip and said lower airfoil lip so that the leading edge of the flap is forward of the two trailing edges of the two lips, the flap being in all positions in spaced relation to the lower airfoil lip and in contact with the upper airfoil lip, the airflowexposed rear portion of the upper flap surface and the upper airfoil surface joining substantially flush with each other so as to form together a substantially continuously curved upper surface, and means for rotating said flap.

3. In an aircraft, an airfoil with continuously curved upper and lower surfaces terminating in a trailing substantially spanwise extending rearwardly projecting upper airfoil lip and in a trailing substantially spanwise extending rearwardly projecting -lower airfoil lip, and a substantially spanwise disposed flap much thinner throughout than the distance between the upper airfoil lip and the lower airfoil lip, movably mounted behind the airfoil and in all positions partly within the pocket formed by and between said upper airfoil lip and said lower airfoil lip so that the leading edge of the flap is forward of the two trailing edges of the two lips, the flap being in all positions in spaced relation to the lower airfoil lip and in contact with the upper airfoil lip, the airflow-exposed rear portion of the upper flap surface and the upper airfoil surface joining substantially flush with each other so as to form together a substantially continuously curved upper surface.

4. In an aircraft, an airfoil with continuously curved upper and lower surfaces terminating in a trailing substantially spanwise extending rearwardly projecting upper airfoil lip and in a trailing substantially spanwise extending rearwardly projecting lower airfoil lip, and a substantially spanwise disposed flap much thinner throughout than the distance between the upper airfoil lip and the lower airfoil lip, movably mounted behind the airfoil and in all positions partly within the pocket formed by and between said upper airfoil lip and said lower airfoil lip so that the leading edge of the flap is forward of the two trailing edges of the two lips, the flap being in all positions in spaced relation to the lower airwith the upper airfoil lip, the airflow-exposed rear portion of the upper flap surface and the upper airfoil surface joining substantially flush with each other so as to form together a substantially continuously curved upper surface.

5. In an aircraft, an airfoil with continuously curved upper and lower surfaces terminating in a trailing substantially spanwise extending rearwardly projecting upper airfoil lip and in a trailing substantially spanwise extending rearwardly projecting lower airfoil lip, a substantially spanwise disposed flap much thinner throughout than the distance between the and the lower airfoil forward of the two trailing edges of the two lips, the flap being in all positions in spaced relation to the lower airfoil lip and in contact with the upper airfoil lip, the airflow-exposed rear portion of the upper flap surface and the upper airfoil and positioned behind all positions partly within the pocket formed by and between said upper airfoil lip and said lower airfoil lip so that the leading edge of the flap is forward of the two trailing edges of the two lips, the flap being in all positions in spaced relation to the lower'airfoil lip and in contact with the upper airfoil lip, the airflow-exposed rear portion of the upper flap surface and the upper airfoil surface joining substantially flush with each other so as to form together a substantially continuously curved upper surface.

EDWARD F. ZAP.

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