Traditional design techniques and trends within the aircraft industry have led designers to produce aircraft with profiles which use double curvature panels to describe their external lines. The use of such complicated external shapes in the design of both military and civil aircraft has resulted in the need for elaborate and therefore expensive tooling used in both the manufacture of detailed parts and final assembly.

Within the military aircraft industry, traditional design drivers have been for operational performance improvements, however, more recently a switch in emphasis has been towards providing an effective balance between performance improvement and life cycle cost reductions.

This new direction in aircraft design has enabled engineers to study the possibilities of eliminating the familiar double curvature airframes and additionally has provided for research into possible new methods of manufacture and assembly for faceted structures.

Patent application no. WO 97/22516 describes a method of assembling an aircraft from a plurality of modular structural components. This document discloses an aircraft having a common wing component and common propulsion support frame component, such that several variants of the aircraft, each variant having the different structural qualities necessary to perform different roles, could be assembled from a basic number of common components. Other modular structural components, such as flaps, may be specific to a particular variant of aircraft, and may be fixed to the common basic structure during assembly of that variant. This commonality of airframe parts allows a substantial reduction in the cost of designing and manufacturing aircraft variants requiring different structural qualities in order to fulfil their different roles.

It is highly desirable that one aircraft variant is able to perform a variety of different missions. Unlike the previous patent application WO 97/22516, which teaches a commonality of structural parts and concentrates on the airframe structure, US Patent 3,640,492 teaches one aircraft structure which is adapted to house a variety of various mission systems in mission-specific modules.

These modules are interchangeable between the same type of aircraft and can be quickly replaced in the event of damage or rapidly changed if the aircraft needs to be reconfigured for a different mission. Each module contains a different avionics mission system which is electrically connected to the main control system of the aircraft when the module is mechanically installed. By simply removing one set of avionics modules and installing a new set, the aircraft can be configured for different roles to fulfil different missions.

US Patent 4,736,910 utilises the same concept as in US Patent 3,640,492, in that avionics mission-specific modules are provided for one type of aircraft structure.

However, in this patent, to save time in reconfiguring the aircraft for different missions, the different avionics systems required for the different missions are housed in the nose or the fin of the aircraft. For example, one nose may contain all the avionics systems necessary to enable the aircraft to carry out an attack mission, and another nose may contain all the avionics systems necessary for a reconnaissance mission. After completing one mission, the nose is simply removed and replaced by another nose containing avionics systems specific to the new role of the aircraft.

Providing modular mission systems for rapid role changing for different missions is useful, however, one of the prime cost driving elements associated with the final assembly of modern combat aircraft is that relating to the installation of aircraft systems. Whilst mission systems consist primarily of avionics systems, such as laser rangers for weapon delivery, which are designed to carry out specific missions, the aircraft systems are integral to the aircraft and are usually necessary for the general functioning of the aircraft, whatever the mission. The integration and final assembly of aircraft systems such as environmental control systems (ECS), engine systems, fuel systems, life support systems and avionics is arguably the most time consuming and expensive area of final assembly, as well as proving time consuming and expensive in subsequent repair and maintenance, therefore much research has been conducted into the possible reduction in complexity of such systems in combination with the introduction of faceted fuselage outer profiles.

The required reduction in complexity related to systems which are required to be integrated into structures such as airframes can be achieved by the use of computer aided design techniques which allow the visualisation of elements such as pipe runs and routing and the placement of electrical wiring looms. Whilst usually reducing the length of such piping and wiring, this common approach does not address the complexity inherent in vehicles where essential elements of such systems are distributed around its internal envelope. If real complexity is to be reduced then a method of localising constituent elements of a system needs to be developed along with the integration of both structures and systems where possible.

Our invention provides a method of manufacture for aircraft which substantially reduces the need for high manpower requirements on aircraft final assembly and subsequent maintenanace and repair, by the simplification of the process by the integration of systems equipments with structural elements to produce dual function structures.

Accordingly there is provided a method of manufacture and assembly for aircraft comprising the manufacture of a range of dual function structural modules, said dual function structural modules each comprising specific systems equipments integrated with structural elements, thereby providing a range of systems specific structural modules which can be integrated with an aircraft structure.

This method of manufacture and assembly preferably permits the substantial localisation of constituent elements of a system.

Advantageously each of said dual function structural modules comprise substantially all the essential elements of a specific system.

The specific system is preferably an aircraft system, which system may be substantially necessary for the general functioning of the aircraft.

The aircraft system may be an environmental control system. Alternatively the aircraft system may be an engine system or alternatively a power system. The aircraft system may comprise an avionics system, or alternatively may be a fuel system. Alternatively the aircraft system may be a life support system, or may alternatively be a hydraulics system.

Preferably each of said dual function structural modules has a common modular function such that said modules may be advantageously adapted to be used on a range of different types and variants of said aircraft.

Preferably galleries are machined into the structural elements of said module for routing fluids for use within said system, instead of using conventional pipework.

In another aspect of the invention, each of said dual function structural modules could be made load bearing, thereby further reducing the complexity associated with the assembly of such modules into an aircraft structure.

Preferably such dual function structural modules may be realisably connectable with an aircraft structure.

Advantageously said dual function structural modules are adapted to be electrically connected to the main control system of the aircraft when said modules are physically connected to said aircraft structure.

The dual function structural modules advantageously are adapted to be disconnected from an aircraft and replaced in situ.

The dual function structural modules preferably comprise a faceted fuselage outer profile, said modules being capable of being integrated with the aircraft structure to comprise part of an outer surface of the aircraft.

A specific embodiment of the invention will now be described by way of example only with reference to the following drawings:- Fig 1 shows an exploded modular breakdown view of an aircraft in accordance with the invention.

Fig 2 shows an example of dual function structural module comprising an environmental control system in accordance with the invention.

In Fig 1, an aircraft 2 is shown broken down into its constituent modular elements. The modular wing 4, which forms the main structure element of the aircraft, is shown having modular control surfaces 6 and structural interface locations 8 for the mounting of the podded modular engine units 10. Additionally, the weapons modules 12 are designed to be assembled to the underside of the wing module 4 thereby forming the centre section structure of said wing 4. The nose undercarriage unit 14 is designed to be located between the nose cone module 18, and cockpit surround structure 20, the environmental control system module 22 and ultimately the cockpit canopy 24. The avionics systems modules are contained within unit 26 shown forming the interface between the forward end of the structural centre section of the wing 4 and the rear of the cockpit area structure 20.

Aft of the wing module 4 the rear undercarriage module 28 is shown bounded by the hydraulics module 16 and two rear fuselage structural members 30. Aft of the hydraulics module 16 is shown a rear weapons module 32 bounded by two tail section structural members 34 and the tail fin unit 38. Additionally, the starboard tail structural member 34 is shown containing the auxiliary power unit module 36.

Fig 2 shows a dual function structural module 22 comprising the essential elements of an environmental control system (ECS). The ECS system has been integrated with the surrounding structure such that where possible the optimised structural design allows for the pipework from elements such as the low pressure avionics feed and return to be removed and replaced by use of galleries 40 machined within the end frame of the structure 42. Hence the module performs a dual structural and systems function and can further be made loads bearing such that its assembly into an aircraft structure would require minimum additional structural strengthening.

Using the modular aircraft design approach engineers are able to select common modular functions, such as for example hydraulics module 16 and the environmental control system module 22 such that they can be used on a wide range of aircraft without being limited to the specific detailed design required for the installation of such modules in conventional double curvature fuselages.

Additionally engine modules 10 can be designed to accommodate a wide range of engine types, but the interface connections to the wing module 4 will be maintained thereby allowing the rapid assembly and/or disassembly of the engine. The use of fully load bearing dual use modules will further reduce the complexity of assembly.

Applying the principle of interchangeability to modular aircraft design not only reduces the time required for assembly of aircraft but also provides for the repair and maintenance of such aircraft built in accordance with the invention to be greatly simplified. For example should there by an environmental control system failure or problem, by housing all of the essential features of the environmental control in module 16 should it be required, then that individual module can be disconnected from the aircraft and replaced in situ thereby avoiding the problems associated with conventional combat aircraft whereby the removal of major environmental control components would require the disassembly of areas of structure and the removal of individual components.