AU2020267323A1 - Detachable annular aircraft wing - Google Patents

Abstract

A port or starboard aircraft wing module of continuous annular shape 1 (for a starboard wing) shown in Fig. 1, forming forward 2 and rearward 3 wing-sections that extend horizontally far apart but are connected at both the inboard root and outboard tips, characterized by a root-section 4 connecting the inboard roots of forward and rearward wing-sections, root-section 4 spanning a vertical range greater than the chord thickness and designed to carry the load on both forward and rearward wing-sections, and root section 4 being secured to the aircraft fuselage by rows 5,6 of lightly loaded fastenings that allow each complete wing module to be detached, attached, or folded for transport or replacement, without the risks of involving highly stressed critical joints, and where within the void at the centre of each wing module is located a vertical-lift fan oriented in an approximately horizontal rotation plane, such that the wing modules serve as a safety guard to reduce risk of accidental contact with these fan blades, and where the aircraft can be operated with vertical-lift fans powered off to facilitate efficient sustained level "cruise" flight. 4/5 Fig. 6 21 I V, 14 3 16 151 17 Fig. 7 21 31 14 16 17

Description

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Fig. 6 21

14 3 16 I V, 151

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Fig. 7 21 31

14 16 17

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AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION STANDARD PATENT DETACHABLE ANNULAR AIRCRAFT WING

The following statement is a full description of this invention,

Including the best method of performing it known to me:

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DETACHABLE ANNULAR AIRCRAFT WING BACKGROUND OF THE INVENTION Although there have been many attempts at an aircraft for personal mobility, sport and recreation of the sort that might capable of launch and landing at an unprepared site such as an outback clearing or a back-yard, to date only helicopters are in significant use. But helicopters are very expensive to acquire and operate, and are substantially less efficient for long-range travel than fixed-wing planes. Light planes require an airport. Micro-light planes require an adequate launch and landing strip and have a limited safe operating envelope. Auto-gyros require an adequate launch and landing strip, have a limited safe operating envelope, and are inefficient for long-range travel relative to fixed wing planes. There are however many current projects developing alternative electric aircraft with vertical-takeoff-and-landing (VTOL) capability. The study [7] compares three current examples in development, in three categories of electric aircraft; "Vectored Thrust", "Lift + Cruise", and "Wingless".

The "Vectored Thrust" example in [7] is assessed as having the best range, but needing very high power for take-off, hover, and landing. Presumably the intent is that the aircraft should be operated in these flight modes for short periods only. However, high peak-power will necessitate heavier and more expensive batteries and motors. Consequently the business model of this example appears to imply an expensive vehicle. The design avoids exposing dangerous fan-blades, but the example needs a back-up parachute to land in the event of total power failure.

The "Lift + Cruise" example in [7] has modest performance, and exposes dangerous fan-blades that, being fixed-pitch, have no fail-safe autorotation mode, but its wings may enable safe unpowered landing on an airstrip.

The "Wingless" " example in [7] is a scaled-up drone, and consequently has severely limited range, fixed-pitch rotor fail-safe and control limitations, and dangerously exposed rotor blades.

Range of an electric aircraft can be extended by adding fuel-cells or other generators, but take-off, hover, and landing will likely require batteries to supply peak-power. Batteries and motors will be heavy if the design requires high peak power.

One problem with operation from an unprepared site is that damage to the aircraft is eventually inevitable. But performance requirements dictate that the aircraft be constructed with lightweight, fragile and highly stressed materials, and patching-up damage to a structure of this sort is likely dangerously unwise.

Fixed-wing monoplanes are efficient for long-range travel, but wings are large fragile structures by nature.

Another problem is how to provide safe transport and storage of a fairly large fragile structure.

Easy and safe detachment, re-attachment, or folding of wings would therefore be highly desirable in any winged aircraft intended for VTOL operation from unprepared sites.

But assembling highly stressed components can be risky when carried out by non-

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specialists. For instance, a number of fatal accidents have been caused by incorrect procedure when attaching blades to the rotor hub of an Auto-gyro. Regular inspection of critical components is also costly.

Wing assembly by the user is usually provided via wing-root tangs that connect inside a fuselage tunnel in the case of sail-plane gliders and a few other light monoplanes. Strut and-cable construction facilitates disassembly of micro-light planes. But for most light aircraft, removal of the wings is a substantial task undertaken infrequently for maintenance or shipping.

Another problem with fixed-wing monoplanes is lack of a natural VTOL capability required for launch and landing at an unprepared site.

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BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of the present invention is illustrated by way of example in the accompanying drawings in which like reference numbers indicate the same or similar elements and in which:

Figure 1 is a starboard-side view of the starboard wing module;

Figure 2 is a top plan exploded view of port and starboard wing modules, detached from an aircraft fuselage;

Figure 3 is a view looking forward from the tail of the exploded assembly of Figure 2;

Figure 4 depicts a horizontal cross-section along the lower row of fasteners 6 of figure 1;

Figure 5 depicts a horizontal cross-section along the upper row of fasteners 5 of figure 1;

Figure 6 is a top plan view of the assembled port and starboard wing modules, vertical lift-fans, and aircraft fuselage.

Figure 7 is a view of the assembly of Figure 6 looking forward from the tail.

Figure 8 is a view underneath the starboard wing module of Figure 1, showing a control surface attached to lift-fan support structure.

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DESCRIPTION OF EMBODIMENTS

The invention disclosed herein has been specially devised in order to provide an aircraft with a wing module that may be detached, attached, or folded for transport or replacement without the risks of involving highly stressed critical joints, that provides VTOL capability for the aircraft by accommodating vertical-lift fans while affording some protection from accidental contact with dangerous vertical-lift fan blades, that allows an efficient "cruise" mode of operation for long-range travel, that has compact dimensions and low weight relative to the aerodynamic lift it generates, that allows the aircraft to transition from VTOL to cruise mode with little change in attitude and without needing excessive trim corrections, and that provides a strong ground-effect for lower-power hovering, exploration, and horizontal acceleration to take-off speed should the aircraft be too heavily loaded for entirely vertical take-off. These features have virtue not only in an aircraft for personal transport but also in a small unmanned "drone". The invention provides an aircraft comprising a port or starboard aircraft wing module of continuous annular topology and method of attachment of this wing module to an aircraft fuselage by fasteners within a unique load-bearing "root-section" joining its forward and rearward wing-sections where they approach the aircraft fuselage. Although the wing-root bending moment is not reduced, the invention reduces load on fasteners by allowing upper and lower fasteners to be located far apart. This method does not require the wing-root load to be concentrated in one or two main spars, unlike the wing-root tang solution for the disassembly problem adopted by sail-plane gliders. Modern fibre-composite construction does not dictate a main-spar structure. The invention instead enables a more efficient lightweight structure that distributes load over the entire wing to solve the disassembly problem in a satisfactory way.

Some potential advantages of "nonplanar" wings in general are explored in [1], [2], [3],

[4], [5] and [6]. The author of [1] notes (Page 24: paragraph 2) an opportunity if a novel wing design "so completely changes the trades between span and drag that substantial savings are possible." The author also notes that ([1] Page 24: paragraph 3) "the appeal of nonplanar systems may involve a combination of factors that lead to an improved design". For instance, connection of the wing tips contributes to strength and stiffness of this annular wing module, and also of the diamond-shaped "joined-wings" considered in [3] and [5], since deflection of the tips is resisted by strain modes in which wing shapes are naturally stiff, allowing lighter wing construction to carry any given payload. The authors of [5] conclude that increasing distance between joined-wings leads to increasing aerodynamic efficiency. This suggests merit, but it is doubtful that much can be definitely inferred from that study about the embodiments here, since the geometry is substantially different. Preliminary data from tests at airspeeds up to 35 m/s of a 1 metre wingspan scale model of the preferred embodiment, including a fuselage but no tail, places an estimate of the aerodynamic centre of the model near the transverse centreline of the wing modules. Thus it is expected that the net lift by vertical-lift fans can be positioned at the aerodynamic centre of the aircraft, with fans oriented pitch-up so that contrary forward force by a slightly angled tail fan can generate pitch-up trim moment to raise the nose until fan power is reduced to cruise mode.

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DESCRIPTION OF THE PREFERRED EMBODIMENT

Figures 1 to 8 illustrate the preferred embodiment.

With reference to the drawings of the preferred embodiment, in particular Figure 1 shows a starboard aircraft wing module of continuous annular shape, forming forward 2 and rearward 3 wing-sections that extend horizontally far apart but are connected at both the inboard root and outboard tips, characterized by a root-section 4 connecting the inboard roots of forward and rearward wing-sections. The root-section 4 is designed to carry the load on both forward and rearward wing-sections. Root-section 4 is secured to the aircraft fuselage by rows 5, 6 of fastenings within root-section 4, where the fastenings are lightly loaded as a consequence of vertical separation of rows 5, 6 substantially greater than the chord thickness. This method of securing root-section 4 to the aircraft fuselage allows each complete wing module to be detached, attached, or folded for transport or replacement. A vertical-lift fan is located within the void at the centre of each wing module, where this vertical-lift fan is oriented in an approximately horizontal rotation plane, such that that the wing modules serve as a safety guard to reduce risk of accidental contact with these fan blades, and where the aircraft can be operated with vertical-lift fans powered off to facilitate efficient sustained level "cruise" flight.

With reference to the drawings of the preferred embodiment and, in particular, with reference to Figures 1 and 2, the forward wing-section 2 is higher than the rearward wing-section 3. This positive stagger configuration is favoured by [2], although this is of doubtful relevance since staggering in [2] does not exceed twice the chord length. This configuration does however provide a wide safety guard for vertical-lift fan rotation planes (16 and 17 of Figures 6 and 7) oriented pitch-up (i.e. slightly rearward-angled fans), with several advantages:

• If the vertical-lift fans are positioned on a line through the aerodynamic centre of the aircraft, then rearward force from these fans together with contrary forward force by a smaller tail fan when hovering can generate a pitch-up trim moment, using only small changes of orientation of this tail fan to raise the nose until fan power is reduced to cruise mode. • Variation of power of the tail fan can generate axial position corrections. • In forward level flight the lift can be enhanced when desired, for example when accelerating to cruise speed, or de-accelerating from cruise speed, by allowing rearward-angled vertical-lift fans to rotate without power, in the manner of an auto-gyro, with blades adjusted to negative pitch.

The rotation planes of port 14 and starboard 15 vertical-lift fans depicted by rotation disks 16, 17 in Figures 6 and 7 have a negative dihedral angle, so that lift by these fans generates inboard-directed downwash. One advantage of a dihedral angle of these rotation planes is to enhance lateral position control by creating lateral forces that can be adjusted by varying fan power or blade-pitch. However this advantage could be at the expense of independent control of roll: To provide extra degrees of freedom to achieve control of both lateral position and roll independently, a longitudinally oriented aerodynamic control surface such as the spoiler or vane 19 sketched in Figure 8 is incorporated into a structure 11 that supports the starboard fan 15, and similarly for the port fan. Structure 11 is supported by attachment to the underside of the rearward wing section 3, and has a small aerodynamic frontal area in forward level flight. This

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arrangement has the advantage of minimal extra drag in cruise mode, since such control surfaces are oriented end-on to the airflow in forward level flight, and structures to support the port and starboard fans are necessary anyway. Good control of position and roll when hovering will help avoid obstacles near the ground. Inboard-directed downwash may also enhance ground-effect lift. Another objective of dihedral angle is to arrange the aircraft geometry such that passengers, or other valuable cargo, are clear of the plane of rotation of the fans as far as possible, in order to mitigate consequences of blade failure or debris strike.

Figure 1 shows an annular wing module 1 that is "two-sided"; meaning that an orientable surface, having a globally defined leading edge and a distinct globally defined trailing edge, can be generated by traversing the mean camber line around the wing module. The "two-sided" topology shown has the advantage of a natural height transition at the wing tip between upper and lower wing-sections. This transition zone at the wing tip can reduce the wing-tip vortex loss for given wingspan as in [1], [2], [4], and

[6], similar in effect to the "winglets" common on commercial airliners. But an alternative "single-sided" topology has competing advantages (see below).

Figure 1 shows the location of the root-section 4. At least two rows of fastenings, a top row 5 and a lower row 6, attach root-section 4 to the aircraft fuselage 31 of Figures 2, 3, 6 and 7. The detail of these fastenings and mounting points is not shown, since good options will be apparent to those with ordinary skill in the art.

Figures 4 and 5 depict horizontal cross-sections through lines 5 and 6 of Figure 1. Figure 4 shows the cross-section at the lower line 6 and Figure 5 shows the cross section at the top line 5. The available choices of construction materials will be well known to those skilled in the art. A key point to note is that this root-section 4 of Figure 1 may be required to resist very large internal shear stresses, in addition to resisting large tension and compression stresses expected near the surfaces of the wing of Figure 1. A preferred embodiment of root-section 4 of Figure 1 employs a plurality of closely-spaced ribs, depicted as 61 in the cross-section 6 of Figure 4 and 51 in the cross-section 5 of figure 5, fabricated from a suitably stiff material such as carbon fibre composite with appropriate fibre orientation to resist large internal shear stresses. Alternatively, in a small drone aircraft the entire root-section 4 of Figure 1 could be largely solid, but threaded with ducts large enough to accommodate cabling for power, control, and data.

The preferred embodiment includes a vertical-lift fan located within the void at the centre of each wing module 1 and 21 of Figures 2, 3, 6 and 7. In order to minimize drag in level cruise mode, vertical-lift fans 14 and 15 of Figures 6 and 7 each have just two opposing blades. Both vertical-lift fans may be powered off and locked stationary with vertical-lift fans 14 and 15 oriented with blades parallel to the airstream as shown in Figures 6 and 7, except that Figure 7 shows the blades oriented in a pitch-up plane. Figure 6 also shows a top plan view of the blade rotation disk 16 (dashed line) of vertical-lift fan 14 and the blade rotation disk 17 (dashed line) of vertical-lift fan 15. The rotation disks 16 and 17 are depicted with possibly reduced size for clarity, but may in an actual embodiment be relatively larger than shown in Figures 6 and 7 without colliding with the wing module.

To propel the aircraft forward the preferred embodiment incorporates at the tail of the aircraft an additional smaller ducted fan that is not part of the present invention, and not shown in the diagrams. All fans are active when the aircraft is hovering or slow moving; the additional ducted fan providing force required to control location and trim of the

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aircraft. In "cruise" mode only the additional ducted fan is powered, the lift fans being switched off.

The preferred embodiment can allow adjustments in flight of power, blade-pitch or rotation plane of vertical-lift fans together with adjustments in flight of deployment geometry of the spoiler or vane 19 in Figure 8, in order to provide attitude and position corrections, especially near the ground to avoid obstacles.

The preferred embodiment can allow the rotation plane of vertical-lift fans to be adjusted in flight in order to lock the rotor blades in an optimal orientation for efficient sustained level "cruise" flight.

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ALTERNATIVE EMBODIMENTS

With reference to the drawings and, in particular, with reference to Figure 1, the annular wing module 1 may instead be "single-sided"; meaning that a non-orientable M6bius strip surface, having transitions at the wing-tip from leading edge to trailing edge and vice-versa, can be generated by traversing the mean camber line around the wing module. This "single-sided" topology has the advantage at the wing tip that the upper surface of the forward wing-section meets the upper surface of the rearward wing section, and lower surface of the forward wing-section meets the lower surface of the rearward wing-section. This wing tip geometry can reduce the wing-tip vortex loss for given wingspan, similar in effect to the "raked wingtips" of some commercial airliners. The "single-sided" topology allows a continuous low-pressure zone on the upper surface, interrupted only at the wing root. By contrast, in the alternative "two-sided" topology the low-pressure zone on the upper surface is interrupted twice; at the wing root and also at the wing tip.

With reference to Figure 1, the fastenings of the top row 5 may optionally incorporate a hinge that allows the wing to fold upwards, similar to butterfly behaviour, when only the lower row 6 of fastenings are released. Butterfly folding drastically reduces the span of the aircraft, for example to facilitate stowage of a small aircraft or to facilitate road transport of a larger one.

With reference to Figure 1, the rear fastening of the top row 5 and the rear fastening of the lower row 6 may optionally incorporate a hinge that allows the wing to fold backwards and upwards, when remaining fastenings are released.

With reference to Figures 1 and 2, the forward wing-section 2 may instead be below the rearward wing-section 3 (i.e. the average plane of the annular wing can be angled forward, instead of rearward as shown). This configuration provides a wide safety guard for a vertical-lift fan rotation plane oriented at negative aircraft pitch (i.e. a slightly forward-angled fan). In forward level flight a forward-angled vertical-lift fan can contribute to forward thrust. Vertical takeoff can be facilitated by pitching the entire aircraft backwards enough to level the vertical-lift fans.

The rotation planes of port 14 and starboard 15 vertical-lift fans shown in Figures 6 and 7 may alternatively have a negative dihedral angle. This retains the advantage of enhanced lateral position control by using outboard-directed downwash, and may in some variations be a better way to place passengers, or other that valuable cargo, clear of the plane of rotation of the fans.

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Citation List 1. Kroo, I. (2005). NONPLANAR WING CONCEPTS FOR INCREASED AIRCRAFT EFFICIENCY. VKI lecture series on Innovative Configurations and Advanced Concepts for Future Civil Aircraft June 6-10, 2005

2. Kang, H., Genco, N. and Altman, A. (2009). Gap and Stagger Effects on Biplanes with End Plates. 47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition 5 - 8 January 2009, Orlando, Florida. USA

3. Schiktanz, D., Scholz, D. (2011) The Conflict of Aerodynamic Efficiency and Static Longitudinal Stability of Box Wing Aircraft. 3 rd CEAS Air&Space Conference 2 1 't AIDAA Congress.

4. Andrews, S. (2013) Multidisciplinary Analysis of Closed, Nonplanar Wing Configurations for Transport Aircraft. Ph. D. Thesis.

5. Perez-Alvarez, J., Cuerno-Rejado, C., and Meseguer, J. (2015). Aerodynamic parametric analysis of an unconventional joined-wing aircraft configuration. The Journal of Aerospace Engineering.

6. Yahyaoui, M. (2019). A Comparative Aerodynamic study of Nonplanar Wings. International Journal of Aviation, Aeronautics, and Aerospace, 6(4). https://doi.org/10.15394/ijaaa.2019.1383

7. Bacchini , A., and Cestino, E. (2019). Electric VTOL Configurations Comparison. Aerospace, 6(3), 26; https://doi.org/10.3390/aerospace6030026

Claims (11)

1/2 CLAIMS: What is claimed is:

1. An aircraft comprising port and starboard aircraft wing modules, each said wing module being of continuous annular topology with structural features and method of attachment of said wing module to an aircraft fuselage wherein, with reference to a horizontal plane containing the longitudinal axis of the aircraft in sustained level flight, each said annular wing module comprises forward and rearward wing-sections that [i] extend horizontally far apart such that the planform, being the projection of said annular wing module on said horizontal plane, has a central void large enough to entirely contain a circle of diameter greater than the chord length of the aerofoil of either said forward or rearward wing-section at a longitudinal-vertical plane that passes though the centroid of said central void, [ii] are joined at the outboard tips and [iii] are connected where they approach the aircraft fuselage at each inboard root by a root-section that (a) spans a vertical range greater than twice the chord-thickness of either said aerofoil and (b) is designed to carry the load on both said forward and rearward wing-sections in such manner as to require only fastenings that are located within said root-section to secure said wing module to the aircraft fuselage and to allow said wing module to be detached, attached, or folded for transport or replacement , the locations of said fastenings spanning a vertical range greater than twice the chord-thickness of either said aerofoil, and wherein a vertical-lift fan, being a fan that can generate predominantly upwards lift, is mounted within said void of each said wing module, the rotation plane of each said vertical-lift fan being oriented at a pitch angle of magnitude less than thirty degrees between said rotation plane and said longitudinal axis, and wherein each said wing module serves as a safety guard to reduce risk of accidental contact with blades of said vertical-lift fan, and wherein said aircraft can be operated in sustained level flight with both said port and starboard vertical-lift fans powered off.

2. An aircraft as claimed in claim 1, wherein each annular wing module is "two-sided" meaning that an orientable surface, having a globally defined leading edge and a distinct globally defined trailing edge, can be generated by traversing the mean camber line around said wing module.

3. An aircraft as claimed in claim 1, wherein each annular wing module is "single sided" meaning that a non-orientable M6bius-strip surface, having transitions at the wing-tip from leading edge to trailing edge and vice-versa, can be generated by traversing the mean camber line around said wing module.

4. An aircraft as claimed in claim 1, wherein one or more of the uppermost fastenings securing each wing module to the aircraft fuselage may incorporate a hinge to allow said wing module to be folded upwards when other fastenings are released.

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5. An aircraft as claimed in claim 1, wherein one or more of the rearward fastenings securing each wing module to the aircraft fuselage may incorporate a hinge to allow said wing module to be folded backwards and upwards when other fastenings are released.

6. An aircraft as claimed in claim 1, wherein each vertical-lift fan has just two opposing fan blades and has the capability to be powered off and locked stationary with said fan blades oriented parallel to the airstream.

7. An aircraft as claimed in claim 1, wherein the rotation plane of each vertical-lift fan may be set or rolled to negative dihedral angle, so that lift by said fan generates inboard-directed downwash.

8. An aircraft as claimed in claim 1, wherein the rotation plane of each vertical-lift fan may be set or rolled to positive dihedral angle, so that lift by said fan generates outboard-directed downwash.

9. An aircraft as claimed in claim 1, wherein a longitudinally oriented aerodynamic control surface such as a moveable fin or spoiler within the void of each wing module is incorporated into a structure that supports the vertical-lift fan, said control surface being exposed to the wake of said vertical-lift fan, in order to facilitate control of lateral position and independent control of roll of the aircraft by varying said control surface deployment geometry together with variations of power, blade-pitch, or rotation plane of said vertical-lift fan.

10. An aircraft as claimed in claim 1, wherein the forward wing-section of each wing module is higher than the rearward wing-section of said wing module.

11. An aircraft as claimed in claim 1, wherein the rearward wing-section of each wing module is higher than the forward wing-section of said wing module.