GB2621610A

GB2621610A - Air freight system

Info

Publication number: GB2621610A
Application number: GB2211998.6A
Authority: GB
Inventors: A Reddicliffe Edward
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-08-17
Filing date: 2022-08-17
Publication date: 2024-02-21
Also published as: GB202211998D0

Abstract

An air freight system comprises an unmanned aerial vehicle (UAV); and a bag for holding a cargo. The bag is removably attached to an exterior, e.g. the fuselage, of the UAV. The mouth of the bag can extend around a portion of the fuselage and can be closed by a fastener, e.g. a zip, to secure it to the fuselage. A sling system can be used to attach the bag to the fuselage, the sling including a sleeve part that receives a portion of the fuselage and a sling part that receives a portion of the bag. The sling system can further comprise an adjuster for moving the bag in a longitudinal direction relative to the fuselage, to adjust the centre of gravity of the air freight system. A rail can be attached to the fuselage, on its under surface for example with one or more mounting points, and the bag then attached to that rail. The bag can have parts with greater flexibility that other parts, with the parts with lesser flexibility facing a forward direction with respect to the direction of flight to provide structural stiffness to the bag to resist distortion of the bag in flight.

Description

AIR FREIGHT SYSTEM

FIELD OF THE INVENTION

The present invention relates to air transportation of cargo, in particular an air freight system.

BACKGROUND

The transportation of cargo by air has been established for many decades. A typical transport aircraft comprises a large cargo hold provided within the interior of the fuselage of the aircraft. Cargo is loaded into the cargo hold before flight and is unloaded upon landing.

Large transport aircraft are invariably manned, i.e. piloted by an onboard crew.

Quite recently, however, there has been a growing interest in the use of small, unmanned aerial vehicles for transportation of cargo, for example for delivery of small packages to domestic homes. For various technical, certification, and cost reasons, small aircraft are far better suited to unmanned operations than are large aircraft.

On the other hand, small aircraft suffer from a problem of limited storage space for cargo. They are therefore relatively costly to operate per unit weight of cargo delivered. Also, like their large counterparts, small cargo aircraft produce no useful revenue when they are flown without any cargo onboard, for example when returning to a base after making a delivery.

The present invention aims to alleviate these problems to at least some extent. SUMMARY OF INVENTION According to an aspect of the invention, there is provided an air freight system comprising: an unmanned aerial vehicle; and a bag for holding a cargo, wherein the bag is removably attached to an exterior of the unmanned aerial vehicle.

As used herein, "bag" or "cargo bag" means a generally flexible container or receptacle, being of sufficient size and strength to hold and transport a cargo in flight. Preferably the bag includes a closable opening or mouth An example is a tote-type bag.

The externally supported bag allows for a greater volume of cargo to be carried, than could be accommodated within the fuselage of the unmanned aerial vehicle (UAV). Moreover, the cargo bag can be easily and rapidly attached to and removed from the UAV, in less time and with less operator skill than would be needed to load and unload cargo from an interior cargo hold. The flexibility of the bag also allows for irregularly shaped cargo, which could be difficult to accommodate inside the fuselage Furthermore, the external location of the bag enables the fuselage of the UAV to be made relatively narrow and with a smaller frontal area, since there is no need for the fuselage to accommodate the cargo in its interior Thus, drag is reduced, leading to a reduction in the cost of propulsive energy, when the UAV is flying without any cargo load.

Further benefits and advantages of the invention will be described later herein below.

The bag may be removably externally attached to a fuselage of the unmanned aerial vehicle.

A mouth of the bag may extend around a portion of the fuselage and be closed by a fastener of the bag, thereby to secure the bag to the fuselage.

The fastener may comprise a zip. The fastener may comprise one or more ratchet straps.

The air freight system may comprise a sling system that removably externally attaches the bag to the fuselage, the sling system including a sleeve part that receives a portion of the fuselage and a sling part that receives at least a portion of the bag The sleeve part and the sling part may be integral such that the sling system is of unitary construction.

The sleeve part and the sling part may be constructed as distinct elements and the sling part may be removably attachable to the sleeve part.

The sling part may be removably attachable to the sleeve part by a zip fastener The sleeve part may be removably attachable to the fuselage by a zip fastener The sling system may comprise an adjuster for moving the bag in a longitudinal direction relative to the fuselage, thereby to adjust a location of a centre of gravity of the air freight system.

The adjuster may comprise a sensor system configured to determine and indicate a position of the bag relative to the fuselage.

The adjuster may comprise an actuator configured, based on the position of the bag received from the sensor system, to move the bag in the longitudinal direction relative to the fuselage to adjust the location of the centre of gravity of the air freight system.

The air freight system may comprise at least one rail attached to the fuselage, the bag being attached to the at least one rail so as to removably externally attach the bag to the fuselage.

The at least one rail may be attached to the fuselage at an under-surface thereof.

The at least one rail may be attached to the under-surface of the fuselage at one or more mounting points of an undercarriage of the unmanned aerial vehicle.

The air freight system may comprise an actuator configured to selectively raise and lower the cargo bag to and from the at least one rail.

The air freight system may comprise a plurality of said rails.

The bag may comprise parts having greater flexibility and parts having lesser flexibility.

The parts having lesser flexibility may be located at a forward position with respect to a direction of flight of the unmanned aerial vehicle, thereby to provide structural stiffness to the bag so as to resist distortion of the bag in flight.

According to another aspect of the invention, there is provided an unmanned aerial vehicle for an air freight system as described herein above, the unmanned aerial vehicle comprising said sling system, said portion of the fuselage being received by said sleeve part.

According to another aspect of the invention, there is provided an unmanned aerial vehicle for an air freight system as described herein above, the unmanned aerial vehicle comprising said at least one rail attached to the fuselage.

BRIEF DESCRIPTION OF DRAWINGS

Examples will now be described with reference to the accompanying figures, in which: Figure 1 shows side and frontal views of an air freight system, comprising an unmanned aerial vehicle supporting an externally-mounted cargo bag, in accordance with the invention; Figures 2a-2c show a sling of the air freight system according to another example, the sling being configured to receive each of a fuselage of the unmanned aerial vehicle and the cargo bag; and Figures 3e-3f show rails configured to support the cargo bag, according to another example.

DETAILED DESCRIPTION

Referring to Figure 1, an unmanned aerial vehicle (UAV) or drone comprises an elongate fuselage, wings, a propulsion system including propellers, and undercarriage (or landing gear) including wheels. A cargo bag, optionally a tote bag, is externally supported by the fuselage and depends downwardly therefrom.

That is, the cargo bag is slung underneath the fuselage and is supported thereby. Together the UAV and the externally mounted cargo bag comprise an air freight system. In this example, the width of the cargo bag (i.e. in a direction transverse to the longitudinal axis of the fuselage) is greater than the width of the fuselage.

A mouth of the cargo bag comprises flap parts, which are wrapped around a portion of the fuselage in the manner of a sleeve and which are fastened together at the upper surface of the fuselage, thereby to secure the cargo bag to the fuselage. In this example, the fastener comprises a high-strength zip. The zip is highly durable and weather-proof. The zip may include a lock for enhanced security. The zip may be rapidly opened and closed, thereby to provide rapid attachment and detachment of the cargo bag to and from the UAV.

Referring next to Figures 2a-2c, in another example a cargo bag is removably externally attached to the fuselage of the UAV by a sling system. The sling system comprises an upper sleeve part which receives a portion of the fuselage, and a lower sling part which receives (at least a portion of) the cargo bag. In this example, the upper sleeve part is wrapped over the fuselage and is secured to the top of the fuselage by a zip fastener. The sleeve part passes through sleeve guides that are provided on the sides of the cargo bag, to secure the cargo bag to the sling system (see Figures 2b and 2c).

In this example, the upper sleeve part and the lower sling part of the sling system are provided as separate parts and are removably connected by a zip fastener (see Figure 2b). Thus, the lower sling part may be easily separated from the upper sleeve part in order to remove the cargo bag, without any need to remove the upper sleeve part from the fuselage.

In this example, the sling system comprises an adjuster for moving the cargo bag fore and aft in a longitudinal direction relative to the fuselage, thereby to adjust a location of a centre of gravity (CofG) of the air freight system. In this example, the sling part is fixed in position relative to the sleeve part, and the cargo bag is slidably movable fore and aft relative to the sling part and the sleeve part.

Locking fasteners are provided for securing the cargo bag to the sling part at the desired location. The fasteners may comprise suitably placed hooks or buckles, or similar devices. One convenient locking means comprises one or more twist-lock fasteners on the sling part, which can pass through holes in the guides on the cargo bag and then be locked. Or, simple pegs or studs can be used to achieve simple and quick, longitudinal positioning of the cargo bag. A plurality of holes in the guides allow options for selection of the hole which coincides with the CofG. Thus, the cargo bag will be safely secured as the UAV manoeuvres during flight.

Correct location of CofG is essential for aircraft safety. If the CofG is too far back then the UAV may stall. If the CofG is too far forward then the UAV may nosedive. Badly out of position CofG may overpower control surfaces, resulting in loss of control of the UAV and possibly a crash. The heavier the cargo load the greater the danger of a crash. It is important for safety that CofG can be easily and rapidly aligned to the necessary position.

Electronic load sensors may be fitted to the front and rear undercarriage legs to provide an instant, automatic indication that the CofG alignment is correct, or incorrect. The sensor system may also indicate the amount of any divergence and state corrective adjustment needed to reach optimum CofG. Monitoring load shift during flight may be carried out and correction triggered. Fore and aft adjustment may be accomplished in flight by a servo-driven line and pulley, driving the cargo bag and/or the sleeve part forwards and backwards to shift CofG position. The sleeve part may be provided with additional clearance around fuselage projections to enable fore and aft adjusting movement.

The ability to have a fixed sleeve position enables sleeves to be tailored around fuselage appendages such as undercarriage legs, aerials, handles filler caps, or similar obstructions, to achieve a close, snug fit. The sling system enables a fixed sleeve to fit complex fuselage appendages and enables a sliding cargo bag with necessary CofG positional locking.

For air drops of the cargo bag, a remote controlled pull ring fastener system, along the length of the cargo bag, enables the load distribution along the length of the fuselage to be maintained, ensuring small-section and light fuselage structures are adequate. Air drops can be free fall or controlled by a speed restricting device such as a winch or friction drum. Parachute drops can similarly be utilised.

For heavy cargo that is not manually handleable, an upgraded system may be provided. Single or multiple attachment zips are replaced by multiple cargo retention ratchet strap mechanisms which similarly uniformly distribute weight along the fuselage, maintaining UDL advantages. The cargo ratchet straps can also lift the cargo bag from ground level up to the under-surface of the fuselage, for locking in place. This enables rapid, relatively non-manual loading. The cargo bag can be lowered to the ground or onto a dolly by the same ratchets. This is a simple, lightweight, high-strength system, which offers quick and easy operation.

A more mechanised version comprises a longitudinal shaft along the top surface or under-surface of the fuselage, inside or outside, linking all ratchet points, enabling co-ordinated lift of all straps to lift the cargo bag, from the ground to the stowed and locked position. The shaft can be manually rotated with a crank, or be powered electrically. Equalising torque drums at each strap position on the shaft can be added to ensure even tension on each strap. The cargo bag can be lowered to the ground or a dolly in a similar fashion As an alternative method of lifting the cargo bag, the aircraft undercarriage legs can be simply swivelled up and down to lower the fuselage onto the cargo bag, enabling its snug attachment to the fuselage. The undercarriage legs are reverse swivelled to the normal position and locked, lifting the attached cargo bag and UAV to take-off status. The swivel of undercarriage legs may be likened to motorcycle stands, by which heavy motorcycles are easily pulled onto attached stands and raised. For extreme loads the swivelling of the undercarriage legs can be driven by a geared mechanism, manually wound or electrically driven A simple, very lightweight pulley block will provide an effective swivelling drive system for bush piloting territories where simplicity is desirable. The leg swivel angle of rotation required is small as the cargo bag lift distance is relatively small.

This reduces required swivel forces. Weights from tens-to-thousands of kilograms can be handled with these techniques.

With this design, loads with a bigger volume than the fuselage volume can be carried. This is a significant advantage over conventional fuselage cargo storage.

The cargo bag may be of any preferred shape, e.g. rectangular, round, ovoid, or customised to carry specific cargo. The front face which is facing the direction of travel can be tapered to a point or knife edge in order to reduce the drag during flight. Similarly the rear face can be tapered for lower drag and aerodynamic performance.

In all examples, the cargo bag is preferably generally flexible, to be able to accommodate a variety of size and shapes of cargo, including irregular shapes. In some versions a mix of rigid, semi-rigid, and flexible components, may be used, to provide the desired performance without interfering with the design and manufacture of aircraft structure. This capability provides unique design options and operational flexibility at low cost, and enables rapid response, quickly catering for unusual loads, which may demand unusual shape or other challenges such as unwieldy cargo projections. The fact that the airframe is totally unaffected by special accommodation of differing cargo bags, to cope with load change, is a huge advantage, reducing planning, simplifying cargo logistical challenges, and reducing capital cost and operational cost.

The sleeve part of the sling preferably follows the contours of the fuselage. The sleeve can therefore be rectangular, round or any necessary shape, to closely match the fuselage in all respects. To ensure that the sleeve remains in place, without creeping rearwards in the airflow during flight, the fit and cut-outs, around projections on the fuselage, act as positional retainers. Alternatively, a simple peg or suitable fastener may be fitted to the fuselage to engage the sleeve and retain its required position. This retainer can be simple, low cost and unobtrusive.

More than one cargo bag may be carried on one sleeve part. Multiple sleeve parts may be provided, each carrying at least one cargo bag.

The sling system may be interconnected to the fuselage by electrical wires, enabling it to act as an energy storage system. Batteries, hydrocarbon fuel or hydrogen tanks may be carried by the system, enabling rapidly-replaceable long-duration flight.

The stability of the cargo bag connection enables it to carry sensors, such as cameras or instruments for multi-differing missions. Rapid cargo bag change enables multiple mission capacity in a short period with reduced manual effort. Pre-fitting of any cargo bag maximises utilisation of the platform. A crop spraying rig and tank can be rapidly fitted and a cargo bag carried.

Referring now to Figures 3a-3f, in another example a UAV (generally similar to the UAV described herein above) comprises an externally-mounted cargo carrying bar or rail system for supporting a cargo bag (also generally as described herein above). This provides a UAV with a strong external cargo carrying system, while avoiding potentially complex and expensive provision of additional attachment hard points or glands on the fuselage. The fuselage can remain standard. The rail system avoids the use and interference of internal space within the fuselage, freeing internal fuselage space for essential items such as fuel, batteries, avionics, instrumentation, and more.

The system preferably utilises the pre-existing, essential undercarriage-to-fuselage connection brackets or plates and hard points, to also be used as mounting positions for a cargo carrying bar or bars, of the required shape, length and width. Using and sharing the existing fuselage-to-undercarriage hard-points avoids the significant additional work and weight that extra hard points would add. Importantly, the system does not interfere with VTOL (vertical take-off and landing), where this is a feature of the UAV. The system is therefore highly versatile and creates no negative impact on aircraft configuration. The system can be used on aircraft configured for runway take-off, launch catapult, or VTOL missions.

The high accelerations ("3-forces") of a launch catapult are easily accommodated by the strong attachment points of the fuselage-to-undercarriage structure, which are already of high strength as needed to cope with landing impact. The cargo weight landing impact is uniquely carried on the undercarriage mounting plates alone, preventing any cargo-imposed higher impact G-forces from passing into the fuselage. This beneficially avoids re-design and additional strengthening of the fuselage, which may be a significantly challenging and costly exercise with sometimes unforeseen complications.

Freeing the fuselage from imposed landing cargo impact forces, enables virtually any UAV to be fitted with this cargo carrying system. Therefore, proven aircraft can be repurposed as cargo-carrying aircraft, provided power and wing performance is adequate. A single aircraft can quickly be reconfigured, enabling multi-mission types to be achieved with minimal capital cost and avoiding multiple aircraft purchases.

The carrying bar or bars, may extend beyond the centre distance of the undercarriage fixing points, and may extend sideways in a "T" form, to provide more than one carrying bar, enabling two or more rows of packages to be carried. If the undercarriage (or skid or ski) is in the form of a single pair of legs with a "T-foot" stabilising bar at the bottom, the carrying bar can still be mounted to the single mounting plate or plates of the leg, provided adequate strength is provided.

The cargo carrying bar can be fitted with various single or multiple cargo attachment devices. Alternatively, quick release, remotely controlled release mechanisms can be used. to release or drop packages.

Lightweight winch systems may be incorporated to lower packages or cargo bags to the ground, with low impact benefits. This is particularly beneficial with VTOL hovering aircraft.

Pre-existing cable glands in the fuselage and undercarriage mounting plates, feeding conducting wires to undercarriage steering or other undercarriage-carried electrically-powered devices, may be used also as cable feed routes to electrical devices on the carrying bar. This significantly reduces the necessary work to incorporate such cargo relevant devices onto the fuselage and provides high value added.

Load rail attachment to undercarriage brackets and typical rail cross-section options are shown in Figures 3c-3t The cargo carrying rail may be a simple uniform rail, or may be designed with compound features, to include the housing of multiple active and passive electromechanical components, which can attach to single or multiple cargo packages in various ways.

These mechanisms can perform various package logistics actions including:-Holding and retaining, lowering on drum or winch cords at controlled speed to avoid package damage; and Lifting packages at a collection point and fixing them in position on the rail for onward flight.

Multiple electromechanical devices can be fitted along the rail to enable multiple individual packages to be handled, independent of the handling of each other, allowing multiple drop-and-collect in any sequence for any package or group of 20 packages.

The lifting and lowering can be achieved during controlled hover of the UAV at height, or for an aircraft on the ground, simplifying initial cargo loading. This is especially helpful for heavy cargo or packages where manual lift or mechanical lifters are non-achievable for any reason.

The multiple lifting, lowering mechanisms can also be controlled to be used as one, i.e. combined together to lift very heavy loads, enabling several light weight mechanisms to achieve extremely heavy lift.

Compound rails may comprise a single complex shaped rail, or may comprise bundled rails with two or more rails forming a compound rail assembly. Each concept enables cut-outs and other features to provide an incremental feature along the rail to manage many individual packages. The compound design enables the provision of adequate rail strength at cut-out positions, and tailored housing and protection of mechanisms The compound rail design benefits include:-Light weight because of reduced unnecessary material, i.e. purpose designed; Minimum weight being beneficial to flight; The ability to accept differing mechanisms at each station along the rail, allowing variable characteristics and differing load weights at each station, without modification to the airframe; Easy swap-out of electromechanical mechanisms without interfering with the aircraft; Cutting maintenance time and avoiding additional aircraft check necessities, after a maintenance process. A benefit not available for maintenance within the airframe due to possible damage to avionics and other items potentially caused during cargo mechanism maintenance within the fuselage; The ability to rapidly remove the rail, swap it or work on it away from the aircraft using specialised tools in a controlled environment of smaller space than the aircraft would need if the system was contained within the airframe; The ability to rapidly swap rails with widely differing characteristics and abilities, to achieve widely differing missions without altering the aircraft; The ability to rapidly attach energy modules such as additional batteries or fuel; 25 and Enabling extreme flight range upgrades; The simple or compound rail can be adjusted for position, fore and aft or sideways, by the provision of rapid lock/unlock fasteners such as cam locking devices. This capability enables relatively unrestricted load distribution along the rail, and subsequent rail position adjustment to be quickly achieved.

In an example, the rail can be driven to a new desired position by controlled electrical servos, automating the adjustment of CofG of the rail-carried load, to achieve desired aircraft and load balance. This achieves maximum safety and the benefit of substantially reduced fuel needs, as flight control surfaces remain relatively neutral, reducing drag, which they do not achieve if the CofG is out of the balance position.

The rail attachments to the undercarriage brackets carry the rail in sliding bearings, which enable low-friction re-positioning of the rail and accommodate servo actuators and sensors. This enables compact, lightweight, efficient rail management, free of fuselage constraints or interference.

In view of the above description, it will be understood that examples of the inventive air freight system provide a light weight, quick attach/detach, externally-positioned, cargo bag system for unmanned aerial vehicles (UAVs), which are speedy to operate and which distribute load, enabling a lighter, narrower fuselage to be utilised, thereby reducing fuel consumption and extending delivery range.

The system also reduces skill requirements at dispatch and delivery points.

The system allows the rapid attachment of a cargo bag to a fixed wing cargo UAV or drone, and the rapid detachment of the cargo bag at the point of delivery, optionally followed by rapid attachment of an onward or return journey cargo bag. Thus, the system provides highly efficient use of UAV assets for an airfreight operation. The system also enables pre-packed cargo bags to be utilised as a standard form of air cargo logistics. The invention provides an integrated and highly efficient, fixed-wing drone-carried, cargo logistics system.

The system may operate in a similar way that existing, modular airfreight cargo containers operate in full size freight aircraft, by providing standardisation and enabling the benefits of pre-packed cargo containers, to provide careful preparation of air cargo and controlled rapid freight turnaround.

A particular advantage is that the cargo bags are (preferably) precisely slung outside of the drone fuselage, beneath the fuselage and close to the under-surface. This enables a much smaller fuselage cross-section to be used, as the fuselage is not required to stow cargo but only to accommodate fuel and flight instrumentation and necessities. Such a small fuselage cross-section substantially reduces frontal area and substantially reduces drag. The narrow fuselage also reduces weight and fuel consumption, and improves flight efficiency and enhances handling.

The drone-carried cargo bag is preferably constructed from lightweight, strong, water-proof fabric (e.g. nylon), in the manner of bags that are conventionally used to carry cement,sand, ballast, and the like, in the building trade.

The cargo bags are rapidly attached/detached to/from the UAV, preferably to/from the fuselage thereof. The system requires no complex mechanisms on either the cargo bag or the aircraft. The system is very lightweight, easy to operate, rapid, and safe, as well as self-locating. The cargo bags may be of various standard sizes, enabling various weights or bulks to be carried. Single or multiple cargo bags can be carried at the same time. Cargo bags of cloth/fabric material construction allow irregular shaped items to be stowed within the bags, bulges of a certain amount being acceptable. This ability provides a significant advantage over rigid pod systems. This flexibility cannot be achieved in usual aircraft cargo holds, as the rigid hull of the aircraft interferes with such irregular items. The system also enables high loads to be managed, loaded, air freighted, and unloaded, without additional mechanical aids.

The system requires no internal fuselage "cargo hold" and removes the need for cargo doors in the fuselage Hence fuselage construction is greatly simplified, and is lighter but stronger.

Any return flights, after a one-way cargo delivery, benefit from operating with a narrower frontal-area fuselage, devoid of the large frontal area that an empty cargo hold of a conventional aircraft cannot avoid. Significant fuel saving is gained by this benefit.

In all aspects the system is simpler, lighter, quicker to operate, and more flexible.

The system is also less expensive to build and operate.

While the cargo bag is preferably attached to the fuselage of the UAV, the cargo bag may be attached differently. For example, the cargo bag may be suspended from mounting points provided on the wings of the UAV.

VVhile the UAV is preferably a fixed-wing UAV, the air freight system may instead comprise a rotary wing UAV.

High-tech sail cloth is a particularly beneficial material for the cargo bag, being very light with high strength.

Optionally, a totally free-form version of the cargo bag provides a controlled form technique. Lightweight battens, such as sail battens, may be provided at desired positions to control the shape of any element of the system, in any direction. Battens may be pre-curved or pre-bent in multiple directions to achieve desired form. The batten system may stiffen longitudinal shape, which is beneficial for very long bag/sling assemblies. Batten-formed, pre-provided bulges may also benefit some cargo needs. Battens can control form, but still preserve the benefits of flexibility.

Single or multiple zips can be used at any connection point to increase strength. Multiple fasteners of other types can be used with zips, or instead of zips.

The cargo bag may comprise an internal restraining system, e.g. straps and buckles or similar, to hold the cargo in the required position. This avoids the use of packing dunnage to restrain cargo.

It should be understood that the invention has been described in relation to its preferred embodiments and may be modified in many different ways without departing from the scope of the invention as defined by the accompanying claims.

Claims

CLAIMS1. An air freight system comprising: an unmanned aerial vehicle; and a bag for holding a cargo, wherein the bag is removably attached to an exterior of the unmanned aerial vehicle.
2. An air freight system according to claim 1, wherein the bag is removably externally attached to a fuselage of the unmanned aerial vehicle.
3. An air freight system according to claim 2, wherein a mouth of the bag extends around a portion of the fuselage and is closed by a fastener of the bag, thereby to secure the bag to the fuselage.
4. An air freight system according to claim 3, wherein the fastener comprises a zip.
5. An air freight system according to claim 2, comprising a sling system that externally attaches the bag to the fuselage, the sling system including a sleeve part that receives a portion of the fuselage and a sling part that receives at least a portion of the bag
6. An air freight system according to claim 5, wherein the sleeve part and the sling part are integral such that the sling system is of unitary construction.
7. An air freight system according to claim 5, wherein the sleeve part and the sling part are constructed as distinct elements and the sling part is removably attachable to the sleeve part.
8. An air freight system according to claim 7, wherein the sling part is removably attachable to the sleeve part by a zip fastener.
9. An air freight system according to any one of claims 5 to 8, wherein the sleeve part is removably attachable to the fuselage by a zip fastener.
10. An air freight system according to any one of claims 5 to 9, wherein the sling system comprises an adjuster for moving the bag in a longitudinal direction relative to the fuselage, thereby to adjust a location of a centre of gravity of the air freight system.
11. An air freight system according to claim 10, wherein the adjuster comprises a sensor system configured to determine and indicate a position of the bag relative to the fuselage.
12. An air freight system according to claim 11, wherein the adjuster comprises an actuator configured, based on the position of the bag received from the sensor system, to move the bag in the longitudinal direction relative to the fuselage to adjust the location of the centre of gravity of the air freight system.
13. An air freight system according to claim 2, comprising at least one rail attached to the fuselage, the bag being attached to the at least one rail so as to externally attach the bag to the fuselage.
14. An air freight system according to claim 13, wherein the at least one rail is attached to the fuselage at an under-surface thereof
15. An air freight system according to claim 14, wherein the at least one rail is attached to the under-surface of the fuselage at one or more mounting points of an undercarriage of the unmanned aerial vehicle.
16. An air freight system according to claim 14 or 15, comprising an actuator configured to selectively raise and lower the cargo bag to and from the at least one rail.
17. An air freight system according to any one of claims 13-16, comprising a plurality of said rails.
18. An air freight system according to any preceding claim, wherein the bag comprises parts having greater flexibility and parts having lesser flexibility.
19. An air freight system according to claim 18, wherein the parts having lesser flexibility are located at a forward position with respect to a direction of flight of the unmanned aerial vehicle, thereby to provide structural stiffness to the bag so as to resist distortion of the bag in flight.
20. An unmanned aerial vehicle for an air freight system according to any one of claims 5 to 12, the unmanned aerial vehicle comprising said sling system, said portion of the fuselage being received by said sleeve part.
21. An unmanned aerial vehicle for an air freight system according to any one of claims 13 to 17, the unmanned aerial vehicle comprising said at least one rail attached to the fuselage.