GB2079688A - Aircraft fitted with wing trailing edge flaps actuated by six-bar mechanisms. - Google Patents

Abstract

Aircraft having wings 4 with flaps 6, attached to the rear underside of the wings and actuated by six-bar mechanisms, each six-bar mechanism 10 being designed such that the respective flap can be moved between a cruise position (not shown), in which the flap is aerodynamically integral with the wing, and a landing position (Figure 4) in which the flap is extended rearwardly such that the flap nose is about at the same longitudinal position as the fixed trailing edge of the wing, the flap is rotated at least 35 DEG downward from the cruise position and a narrow gap is formed between the flap and the wing, whereby the six-bar mechanism is such that the flap, during movement between cruise and landing positions, passes an initial take-off position (Figure 3) in which the flap is moved rearward over about three-quarters of the full extension-distance, rotated downward a small angle of approximately 5 DEG and a considerably wider gap is formed between the flap and the wing than in the landing position. The flap may incorporate a secondary trailing edge flap which is separated from and angled relative to the main flap only in the landing position. <IMAGE>

Description

SPECIFICATION Aircraft fitted with wing trailing edge flaps actuated by six-bar mechanisms.

The invention is related to an aircraft having wings with flaps, attached to the, in the direction of flight, rear underside of the wings and actuated by six-bar mechanisms, each six-bar mechanism being de signed such that the respective flap can be moved between a cruise position, in which the flap is aerodynamically integral with the wing, and a land ing position in which the flap is extended rearwardly over an extension distance such that the flap nose is about at the same longitudinal position as the fixed trailing edge of the wing, in which the flap is rotated at least 35 downward from the cruise position and in which a narrow gap is formed between the flap and the wing.

Such an aircraft is known from the article "Boeing 7x7" published in Flight International of June 19, 1976.

The advantage of using six-bar mechanisms over the traditional flap operating mechanisms compris ing rails, carriages and screwjacks is that the six-bar mechanisms have much more favourable mainte nance and service life characteristics.

The known aircraft will be able to make use of runways of reasonable length for landing because the flap can be moved to a position as described above, suitable for landing.

However, for take-off from high altitude runways during hot weather, where the air has a relatively low density, the relevantaircrafwill need a long runway in order to achieve the high take-off speeds required in these circumstances. As a result, the aircraft will be able to make use of a number of airports only with a lower take-off weight, which unfavourably affects the enconomic use of the aircraft.

The object of the invention is to provide an aircraft of the type described above which has a short take-off distance in a low air density situation.

According to the invention this is achieved in that the six-bar mechanism is designed in such a way that the flap, during its movement between the cruise and landing positions, passes an initial take off position in which the flap is moved rearward over about three-quarters of the extension-distance, ro tated downward over a small angle of approximately 5" and a considerably wider gap is formed between the flap and the wing than in the landing position.

Due to this, the aircraft experiences high lift together with a little drag, so that the take-off speed is reached in a short take-off distance.

Due to the measure according to claim 2 the dimensions of the six-bar mechanism can be small.

By applying the measures contained in the claims, advantages are gained such as minimum aerodyna mic influence on the wing profile and a robust design of the six-bar mechanism.

Further features and advantages of the invention are apparent from the following description of an embodiment according to the accompanying draw ings.

Figure lisa plan view of an aircraft according to the invention, Figure 2 is a larger scale section through ll-ll on Figure 1, showing the wing flap in cruise position; Figure 3 is the same section as Figure 2 but showing the wing flap in the take-off position, Figure 4 is the same section as Figure 2, but showing the wing flap in the landing position, Figures 5, 6 and 7 are similar sections to Figures 2, 3, and 4 respectively but for an aircraft having a wing flap consisting of a forward flap and a rear flap, Figure 8 is a plan view of the six-bar mechanism shown in Figures 5-7 but on a somewhat smaller scale.

Figure 9 is a perspective view of the six-bar mechanism in Figures 5-7, in the same flap position as Figure 7, Figure 10 shows a section through one of the links in the six-bar mechanism.

The aircraft 1 consists of a fuselage 2 with an integral tail section 3. Wings 4 are also connected to the fuselage 2 which in this example carry jet engines 5. Flaps 6 are mounted to the rear underside of the wings 4 which, for low speeds in particular, can be extended to the position shown by the dotted lines in Figure 1 in order to increase the lift. This extension takes place by means of six-bar mechanisms 10 enclosed in fairings 7. As shown in Figure 1 each wing 4 has two such flaps 6 on its trailing edge.

Apart from the flaps 6, ailerons 9 are mounted on the trailing edge of the wing 4 near the wing tip. Each flap 6 is operated by two six-bar mechanisms 10.

Each six-bar mechanism 10 comprises a swivelling arm 13, a flap support beam 14, a boom 15, a coordinating link 16 and a tension rod 17.

The boom 15 is hinge mounted at its front end 20, by means of a bearing 21, to support 22 which is connected to a load-carrying part of the wing 4.

The tension rod 17 is attached via a bearing 24to the rear end 23 of the boom 15.

The coordinating link 16 is also hinge mounted, via a bearing 25, to the boom 15 at a position between the forward end 20 and the rear point 23 of the boom.

The coordinating link 16 is hinge mounted at its other end 28, via a bearing 29, to the swivelling arm 13, which in turn is hinged mounted, via a bearing 27, to a support 30 in the wing 4. The other end of the swivelling arm 13 is connected, via a bearing 31,to the flap support beam 14. The tension rod 17 is also connected to the flap support beam 14 via a bearing 26.

The flap 6 is connected to the flap support beam 14 by means of adjustable rods 32 known as such. With the aid of the adjustable rods 32 the flap 6 can be adjusted such that it mates correctly with the cut-out 33 in the wing 4 when the flap is in the cruise position shown in Figure 2, so that the wing 4 and the flap 6 form an integral unit aerodynamically.

A drive rod 12 is attached to the swivelling arm 13 at one end, its other end being connected to the crank 11 of the rotary actuator 35. By operating the rotary actuator the flap 6 can be moved from the cruise position shown in Figure 2, via the initial take-off position shown in Figure 3, to the landing position shown in Figure 4.

The rotational movement of the crank 11 is transmitted, via the drive rod 12, to the swivelling arm 13. During anti-clockwiseoperation of the rotary actuator 35, when looking at Figure 2, the swivelling rod 13pushestheflapsupportrod 14and the flap 6 to the right. The tilting of the flap support beam 14 with respect to the wing 4 is caused by the tension rod 17 which is connected via a bearing 24, to the boom 15. The movements of the boom 15 are thus programmed by the coordinating link 16 in such a way that the flap 6 achieves the correct positions.

Thanks to the mutual positioning of the bearing points, as shown in the Figures, and the chosen length of the rods, the flap positions described in claim 1 and shown in the Figures are achieved.

The bearings 21, 24-27, 29,31, can be suitable self-lubricating bearings or standard greased bushbearings.

During extension of the flap 6, the fairing 7 is opened by a conventional linkage mechanism, not shown in the Figures. The Figures do show that the fairing 7 hinges around the bearing 21. This is only one possible design. The fairing can hinge around a different point if necessary.

As shown in Figures 2-4 (inclusive) each angle of the triangle which is formed by the centre lines of bearings 24, 26, and 31, is greater than approx. 20" in the cruise position (Figure 2) and greater than approx. 35" in the landing position (Figure 4).

Each angle of the triangle formed by the centre lines of bearings 21, 25 and 29 is greater than approx. 24" in the cruise position and greater than approx. 29" in the landing position. Due to these measures the invention ensures that the maximum load in each rod is at most three times the maximum aerodynamic load on the six-bar mechanism. In case the rods are mounted in pairs, such as rods 16 and 17, this factor is one and a half maximum.

In the design shown in Figure 5 through 9, the flap comprises a forward flap 40 and a rear flap 41. For achieving greater lift, the rear flap 41 can be moved rearwards with respect to the forward flap 40 and simultaneously be rotated (see Figure 7 and 9). This also results in greater drag, so that this position is used for landing.

Forthis reason, the rearflap 41 can move away from the forward flap 40 only after the maximum take-off position has been passed. In this maximum take-off position the flap 6 is rotated approx. 20" with respect to the cruise position.

The mechanism that moves the rear flap 41 away from the forward flap 40, movement beginning when the flap 6 has rotated 20 , consists of an auxiliary boom 44 protruding rearwards from boom 15, and rigidly fixed to it, a guide link 42 and a push rod 45. The guide link 42 is hinge mounted on the tension rod 17 via a bearing 43. The push rod 45 is attached to the guide link by means of a self-aligning bearing 48 and such that the axis of bearing 48 is - co-linear with the axis of bearing 26 in the cruise position. The other end of push rod 45 is attached via a self-aligning bearing to support 49 of the rear flap 41. In cruise and take-off positions, the guide link 42 is fixed relative to tension rod 17 by a, schematically drawn, spring 50.

During movement ofthe six-bar mechanism 10to the maximum take-off position, the forward flap 40, the rear flap 41 and the push-rod 45 move as one unit. This becomes apparent from a comparison of Figures 5 and 6.

The end of the guide link 42, which, with respect to bearing 43, is situated on the opposite side of the attachment point with push rod 45, is provided with a profiled slot 51. This profiled slot 51 is designed in such a way that it is engaged by a cam roller 46, mounted on the auxiliary boom 44, when the flap 6 is tilted past the maximum take-off position, i.e. when the flap angle exceeds 20 . Due to the movement of the cam roller 46 in the slot 51, the guide link 42 is rotated around bearing 43 with respect to tension rod 17, so that the rear flap 41 is moved away from the forward flap 40 by means of the push rod 45.

The rear flap 41 is attached to the forward flap 40 by means of support arms 52. Each support arm 5 is hinge-mounted at one end to the rear flap 41 and, at the other end, hinge mounted to the forward flap. In the cruise and take-off positions, in which the two flaps 40 and 41 form one unit, the support arm lies approximately in the spanwise direction of the flaps 40 and 41. The axes of the hinge connections with flaps 40 and 41 lie at an angle with respect to each othersuch that during the movement of the rear flap 41 away from the forward flap 40, in which the support arms swivel outwards, the rear flap 41 rotates relative to the forward flap 40. For simplicity the support arms 52 are shown schematically in the Figures.

Figure 8 demonstrates that during the relative movement of the rear flap 41 with respect to the forward flap 40, from the cruise position indicated by full lines to the landing position indicated by dotted lines, a spanwise shift of the rear flap 41 takes place.

Bearings 48 and 53 in the push rod 45 are therefore ball points (see Figure 9).

Swivelling arm 13, the coordinating link 16 and the tension rod 17, are each made up of two paired parts for structural reasons. The applicable identification numbers are therefore given the suffixes a, b, in Figures 8 and 9.

In accordance with certain safety requirements, a crack which develops in a structural part of an aircraft must have no unfavourable influence on the operation of the structure. To satisfy these requirements each rod in the mechanism is built up of 2 or 3 elements. An example is given in Figure 10 where rod 54 is shown assembled from parts 55 and 56.

The rod elements 55 and 56 have individually i sufficient strength to withstand the loads which act on rod 54. The rod elements 55 and 56 are connected to each other by, for example, rivets 57. Should crack arise in one of either elements 55 or 56, the remaining element, 56 or 55, remains fully intact and fulfils the function of rod 54.

Claims (11)

1. Aircraft having wings with flaps, attached to the, in the direction of flight, rear underside of the wings and actuated by six-bar mechanisms, each six-bar mechanism being designed such that the respective flap can be moved between a cruise position, in which the flap is aerodynamically integ ral with the wing, and a landing position in which the flap is extended rearwardly over an extension distance such that the flap nose is about at the same longitudinal position as the fixed trailing edge of the wing, in which the flap is rotated at least 35 downward from the cruise position and in which a narrow gap is formed between the flap and the wing, characterized in that the six-bar mechanism is designed in such a way that the flap, during its movement between the cruise and landing positions, passes an initial take-off position in which the flap is moved rearward over about three-quarters of the extension-distance, rotated downward over a small angle of approximately 5O and a considerably wider gap is formed between the flap and the wing than in the landing position.

2. Aircraft according to claim 1, characterized in that the six-bar mechanism is designed in such a way that the flap during movement from cruise position to the initial take-off position, is initially tilted upwards.

3. Aircraft according to claim 1 or 2, character ized in that the six-bar mechanism is arranged underneath and forward of the flap and that the flap has a virtually undisturbed surface over its whole length.

4. Aircraft according to one of the foregoing claims, characterized in that a fairing is arranged round the part of the six-bar mechanism extending under the wing, having a depth less than 10% of the wing chordlength.

5. Aircraft according to one of the foregoing claims characterized in that all links of the six-bar mechanism are free of cut-outs for allowing passage of other parts of the six-bar mechanism, during its movements.

6. Aircraft according to one of the foregoing claims characterized in that each link of the six-bar mechanism is assembled from at least two link parts mounted back-to-back.

7. Aircraft according to one of the foregoing claims, characterized in that the links extend at such angles to one and other, that the maximum load in each link is at most three times the maximum aerodynamic load on the six-bar mechanism.

8. Aircraft according to one of the foregoing claims characterized in that the most forward hinge point of the six-bar mechanism is located at a distance in front of the flap nose which is at most 6% of the wing chord length.

9. Aircraft according to one of the foregoing claims wherein the flap comprises a forward and a 'rear flap, characterized in that the rear flap can be moved relative to the forward flap by means of a guide link, provided with a track and pivotably connected to a link of the six-bar mechanism and that another link of the six-bar mechanism supports a roller engaging in the track of the guide link.

10. Aircraft according to claim 9, characterized in that the track in the guide link and the positioning of the roller are chosen such that the guide link moves the rear flap relative to the forward flap only with rotation of the flap over more than 20 with respect to the cruise position.

11. Aircraft substantially as hereinbefore described with reference to the accompanying drawings.