Light aircraft.

The invention relates to a light aircraft employing a parachute-wing. A parachute-wing has a fabric parachute canopy which assumes an aerofoil section shape in flight. The shape of the canopy is maintained by air flow, the canopy having no rigid struts, and lift is generated by forward motion of the aerofoil shaped canopy. The pilot sits in a carriage suspended in flight from the parachute-wing and motive power is provided by an engine-driven propeller mounted on the carriage.

Objects of the invention are to provide a light aircraft of the kind described which is inexpensive, easy to fly, and safe. A particular advantage of the parachute-wing aircraft is that the wing may be packed into a particularly compact bag since there are no rigid struts. A feature of the invention is the design of a fold-up carriage which is simple to erect and which may be stowed in a compact form.

Powered parachute-wing aircraft have been suggested hitherto, but no machine has been disclosed which provides satisfactory solutions to certain practical problems. Two closely associated problems are those of control of the wing and the effect of propeller torque reaction. The effect of propeller torque reaction is to tend to twist the engine, and thus the carriage, in a direction opposite to that of the propeller rotation. While this effect is negligible in a rigid-wing aircraft of significant weight, it is significant in a light parachute-wing aircraft and has the effect of exerting a differential left-right tension on the support lines, so unbalancing the aircraft and affecting control, particularly if control is by means of control lines extending from the canopy to the carriage.

Earlier discussion of powered parachute-wing aircraft have not addressed this problem. For example, United States patent specification Nos: 3343779 and 4375280 have shown schematic arrangements for supporting a propeller-driven load from a parachute wing. The earlier specification has no discussion of directional control and shows suspension of the load from a single suspension point. If there were to be any directional control with such an arrangement, since the disposition of the load with respect to the wing is uncontrollable, this would have to be effected by a rudder on the load. Such an arrangement is indeed suggested in specification No: 4375280, where again in the majority of embodiments the load or carriage is supported at a single point from a free wing which may be rigid or partly flexible. There is discussion in this specification of a two-point suspension system to allow the altitude of the carriage to be controlled with respect to the wing, but no discussion of the effect of torque reaction.

Compensation for the effect of torque reaction is possible by the use of contra-rotating propellers, for example and a two-propeller machine is disclosed in United States specification No: 4424945. However, here there is also a rigid wing in addition to a parachute wing and the purpose of the second propeller and engine is said to be for additional power. There is no discussion of torque reaction.

Contra-rotating propeller arrangements are heavy and expensive. Also, the provision of flaps and rudders on the carriage is unduly complex, adds to the weight and is expensive.

In developing the present invention we have found it possible to use a single propeller and to control the direction and speed of the machine by means of simple control lines to the canopy. This is made possible in accordance with the invention by arranging that the carriage is supported from the canopy by at least two support lines which have attachment points spaced apart laterally with respect to the fore and aft direction of the machine, and by ensuring that the support lines are of different lengths so as to provide a side-to-side suspension bias which compensates for the propeller torque reaction.

While it is possible to use two attachment or suspension points on the carriage a preferable arrangement is to use four points arranged in a square aligned with the fore-and-aft and lateral directions.

With the biased support-line arrangement described it is possible to balance the aircraft for normal cruising flight. This simplifies control, which is effected by pulling on the control lines. It is a particularly important feature of the invention that the aircraft should be easy to fly. To this end a handle-bar control unit has been devised which has two hand-grips, an engine twist throttle control in one hand-grip and an attachment point at each end for a respective one of the said two control lines. The handle-bar unit is free, not being mounted on a column, and this gives easy and intuitive control by pushing the unit away as a whole to give balanced braking on both sides of the canopy, or by turning the handle-bar unit to draw the lines in differentially so as to turn.

For safety it is preferable to limit the extent to which the control lines may be drawn in, so obviating the risk of stalling by the inexperienced. To this end the control lines are drawn through apertures and carry stop blocks which will not pass through.

The structure of the carriage is important in minimising weight and facilitating handling and stowage. Preferable construction uses a longitudinal base strut on which is mounted a foldable tricycle undercarriage and an upright strut pivoted to the base strut. The frame of the pilot's seat is used as an integral structural member which rigidly links the base strut to the upright strut in the running condition, the two struts and the seat frame forming a triangle. A forward tie cable is preferably used to tie the top of the upright strut to the front of the base strut so as to put the seat frame in compression and add rigidity to the structure.

Preferably the top of the upright strut carries a fore-and-aft support bar which has at its forward end a support bracket for the parachute-wing support lines and at its rear end a 'U'-shaped guide for the parachute lines. Such a guide can be used to support the lines of the parachute-wing clear of the propeller prior to take-off. This is a lighter and more satisfactory arrangement than a complete propeller guard.

The invention will further be described with reference to the accompanying drawings, of which:- <ul id="ul0001" list-style="none"><li>Figure 1 is a perspective view of a light aircraft in accordance with the invention in flight;</li><li>Figure 2 is a view of the support bracket of the aircraft of Figure 1;</li><li>Figure 3 is a view of an alternative support bracket of the aircraft;</li><li>Figure 4 is a diagram showing the handle-bar control unit of the aircraft;</li><li>Figure 5 is a view of the carriage of the aircraft in the running condition;</li><li>Figure 6 is a view of the attachment point of the seat frame to the base strut;</li><li>Figure 7 is a view of the carriage part-­folded; and</li><li>Figure 8 is a view of the carriage fully folded to the stowing condition.</li></ul>

Referring to Figure 1 there is shown an aircraft comprising a carriage 1 which has a seat for the pilot 2, an engine 3 and a propeller 4. There is a tricycle undercarriage 5.

In flight the carriage is supported by a parachute-wing 6 which is entirely made of parachute fabric. When in flight the wing is substantially rectangular in plan and has an aerofoil section so that lift is generated by forward motion. The shape of the wing is maintained by the air flow.

Spaced points of the parachute-wing canopy are connected to rigging lines 7. Four sets of these lines are brought together to four support lines 8 which are attached to discrete suspension points 9 on the carriage. Further rigging lines 10 are connected to points along the trailing edge of the parachute-­wing. These are brought together to respective right-hand and left-hand control lines 11 which pass to the pilot. By drawing on a control line the pilot is able to increase lift of the canopy either at one side or the other for turning or simultaneously for braking.

In the drawing, the single propeller 4 rotates in a clockwise direction as seen from the rear. This gives a counter-clockwise torque reaction. To compensate for this, the rear support line 8 on the starboard side is shortenedd with respect to the others. This is a permanent modification which is set empirically. The length of the lines are not adjustable in flight.

Figure 2 shows the support bracket 13 which has suspension rings 14 for the support lines. It will be seen that the suspension points are arranged in a square aligned with the fore-and-aft and lateral directions of the carriage. The figure also shows the control lines 11 passing through holes 15 in the support bracket. In order to prevent the control lines being drawn in too far with the risk of stalling, blocks 16 are attached to the lines to form stops which will not pass through holes 15.

Figure 3 shows an alternative support bracket where there are only two suspension rings 14 spaced laterally.

Figure 4 shows the control unit 17 which is used by the pilot. This comprises a handle-bar with a hand-grip at each end. The right-hand grip has a twist throttle control 18 linked by cable to the engine throttle. Rings 19 at each end of the unit form attachment points for the ends of the respective control lines 11.

Figure 5 is a view of the carriage 1 in the running condition. A fore-and-aft base strut 20 has a front wheel 21 pivotally fixed in castor fashion at the front end. Foot-bars 22 allow the pilot to steer. Rear wheels 23 are attached by rear wheel struts 24 universally jointed to the rear end of the base strut at 25. Tie bars 26 are pivoted to the base strut at 27 and detachably fixed to the wheel struts at 28. A double tie cable 29 couples the ends of the wheel struts 24 so as to form an 'A' shape therewith.

An upright strut 30 is pivoted at 31 to the base strut. Pivoted to the upright strut is a seat frame 32 which, at its other end 33, is detachably mounted to the base strut. The two struts and the seat frame make a structural triangle. The seat frame is maintained in compression by tension in a front tie cable 34 which couples the front of the base strut to the forward end 35 of a support bar 36 at the top of the upright strut.

To fold the carriage the engine 3 is removed and the top of the front tie cable 34 is detached from the support bar and a pin 37 is removed to allow the support bar to fold along the upright, it being then pivoted thereto. Pins at 38 are removed to allow the seat frame to be detached from the base strut.

Figure 6 shows pins 38 holding the base of the seat frame in a bracket 39. Figure 7 shows the top part of the carriage folded down. It is to be noted that there are provided two lateral tie cables 40 (Figure 5) which give lateral support to the upright. The length of these cables and their relation to the hinge at 31 allows folding of the upright strut along the base strut. Figure 8 shows the carriage in the fully folded positon, tie bars 26 having been detached from the wheel struts and folded along the base strut.

At the rear end 40 of the support bar 36 is mounted a 'U'-shaped guide 41. This has the function of supporting the parachute-wing lines clear of the propeller on start-up. With the parachute-wing set on the ground behind the carriage the lines are laid on guide 41 and the engine started. The back-draught from the propeller inflates the canopy and this is assisted by forward movement. The canopy rises and the lines are maintained clear of the propeller.

The effect of the support line bias on the balance of the aircraft is very sensitive. For balance of propeller torque at cruising speed, a length difference in the lines of only a few inches - for example between 2 inches and 8 inches in a total length of 15 to 20 feet is found to be effective.