Innovative developments in aerospace often lead to spin-offs in other industries. TheÂ NLR presents twelve proposals for the development of new tools for manufacturers of electric cabling systems (also called wiring harnesses), which can also provideÂ Â profits in other sectors. The Electrical Knowledge and Innovation Center (ELKINA) of BAC strives to further develop these ideas with the NLR and interested companies. In BAC (Business Accelarator)Â businesses, governments and research institutions stimulateÂ innovations around the themes Electrical Systems, Corrosion Treatment, Composite and Avionics maintenance.
In the aviation industry, it was always assumed that a cable was as dangerous or harmless as the system it was connected to. If a cable for the passenger in-flight-entertainment system (for movies, music and games) malfunctioned, this was considered as harmless. If a cable for an important aircraft control system malfunctioned, this was considered as hazardous. However, after various investigations into the causes of several aircraft accidents, it was determined that all cables play a role in flight safety. Investigator Edwin van de Sluis of the NLR: ‘If a cable from the entertainment system melted, this could damage an important cable located next to it.Â
Recently new regulations for aircraft wiring have been implemented. These regulations consider the aircraft wiring as a separate subsystem of the aircraft. This subsystem, also called Electrical Wiring Interconnection System (EWIS), must be separately analyzed for safety. Suppliers of aircraft wiring must prove that they comply with the new regulations. How exactly they must achieve this is not yet specified.Martijn Stuip of NLR: ‘You must, for example, prove that the distance between certain cables is large enough so that they cannot influence each other. This can be done with a tool in the design process.’Van de Sluis: ‘It is necessary to comply with the regulation’s safety requirements as efficiently as possible and any potential additional requirement of the aircraft manufacturer. More efficiency is better, because this leads to cost reductions and an advantage over the competition. This is why we search for the ways and means to do this as effective and efficient as possible.Â
The challenge lies in the fact that the regulations do not define how the manufacturer must prove that the aircraft wiring is safe. NLR analyzed the regulations and established a list of requirements and the possible tools with which manufacturers, such as Fokker Elmo, could meet these requirements efficiently. Within the context of BAc, the Electrical Knowledge and Innovation Centre and NLR are searching how these tools can be used in other sectors than aviation. Bert Klarus, project manager of BAc: ‘In other words: in which sectors can we profit from these often innovative and technologically advanced solutions? Or the other way around: which sector or which company can help produce these tools? Because not all the proposed tools exist yet.’The proposed tools vary from determining the distance and placement of the cables (early in the design phase of an aircraft) and mapping the risks of electric arcs (electrical discharge in the air) to 3D and augmented reality applications.
Determining distance and location
Aircraft wiring designers deal with design rules: a so called Knowledge base of design rules. This could, for example, concern the distance between cables and knowing which cables are allowed to be close to one another. The question is whether or not and how we can (further) automate these ‘rules of thumb’. Mathematical models may be necessary to model certain behaviours, and/or experimental configurations needed to determine which distance between certain cables is safe. Aircraft wiring manufacturers constantly search for the optimum between the lowest weight (meaning thin cables and thin insulation) and the prevention of interference and hazards that can result in fire. Today, this is primarily based on practical experience and historic data. Van de Sluis: ‘If you can analyze that a smaller separation between cables is still safe, you can benefit from it. You want the authorities to get convinced that the wiring is safe.’In other sectors the lack of space and the need to reduce weight is not as prominent an issue as in aviation. For machines, ships, trains or trucks, these matters are hardly or not at all important.
Electric arcs and overheating
The EWIS rules state that a supplier must investigate the consequences of an electric arc and overheating of cables. An electric arc is an electrical discharge through the air between two closely located conductors that have a difference in voltage. It can occur in cables where part of the insulation is missing and the core is exposed. Insulation can be damaged by constant chafing due to the cable’s vibration. During arcing a lot of energy is released in the form of heat, which can cause the insulation to melt further. Overheating occurs when the current in a cable is too high. How are these risks determined? With visual inspection? This is usually impossible due to the limited space in aircrafts. The US Federal Aviation Administration (FAA) is investigating electrical arcs and overheating. Desktop analysis and simulation of electric arcs based on models are alternatives to visual inspections. Determining these type of risks properly, will be Â of great added value for safety. Practically every industry can profit from a tool that predicts the danger of electrical arcs or overheating of cables.
Design support tools
During the physical installation of wiring harnesses, it sometimes happens that the cables are simply too short. This is usually because the design of an aircraft is often subject to changes. Van de Sluis and Stuip expect these kinds of problems to be avoided with a 3D installation tool. Stuip: ‘Think of a virtual reality-like program as an support tool for physical installation. You would need a database with all the information, with the shape of the cable and what the area in which it must be installed looks like.’Fokker Elmo is apparently doing well in this area, but other sectors that must install wiring systems in a limited space could benefit from such a system.
Not opting for the standard cable
Aircraft manufacturers must indicate how much voltage a certain cable should be able to handle. A database with this information about certain cable connections and the associated electrical voltage could be a solution to store such information. Such a database may also be interesting for sectors that have comparable needs, such as manufacturers of complex machines or hydraulic systems.
Design with maintenance in mind
When designing, it is important to consider the maintenance necessary during the lifespan. Consequently, an analysis on the accessibility for inspections and repairs must already be conducted during the design phase. This is clearly linked to the previously mentioned virtual reality application in the design phase. It is clear that this is important for all situations in which a wiring harness system must be maintained in a poorly accessible space.
Certain topics in the EWIS rules are so specific that a cross-over to another sector is not immediately apparent. An example of this is the division of aircraft into zones. As an example, there is often a zone for the fuel in the wings. For every zone there are specific requirements. This ‘model’ could be interesting for large chemical production sites that work under the same safety regime, and it could also be split into office, warehouse and production, for example.
Installation support tools
To simplify the installation of wiring harnesses in an aircraft, an enhanced reality tool would be very handy. The person who installs the systems gets additional information, for example on a tablet or projected in his field of view, so that he knows which actions to perform. This would require real-time access to a database providing background information. Every industry that must carry out installation activities in a limited or complex space can benefit from such a system.
How can you monitor the condition of wiring systems while they are in operation? A test is running with, amongst others, Fokker Elmo and NLR, using Fiber Bragg Grating sensors (fibreglass sensors). The sensors are integrated into a bundle of cables. The results of this test are not yet known. The technique is interesting for any situation in which it would be extremely difficult or costly to replace the wiring systems. The fibreglass sensors are also potentially interesting for determining the condition of composites, for example.
Predicting the aging process of cables
The ability to predict the aging process of cables, will be beneficial for maintenance activities. Van de Sluis: ‘Think of the situation that the cable supplier prescribes that a cable must be inspected every four months to guarantee the safety for a certain application, but you can prove that the inspections can be carried out every six months, based on information about actual use, this would make a difference in the maintenance costs.’One solution would be to develop a system that contains the information about the wiring harnesses and that can predict the deterioration of the wiring harnesses through aging models. Every industry that wants to optimize the maintenance of wiring systems and has to deal with safety demands would benefit from this.
Maintenance activities for wiring harness systems can be performed better and faster in future, by the use of enhanced and augmented reality applications. Just as with the previously mentioned tools that support design and installation, a database with EWIS information, and real-time access to this database during maintenance activities, is necessary. And just as with the prediction of the aging process of cables, this technique is interesting for every sector in which maintenance and safety are important.
Especially for older aircrafts, the wiring diagrams are not always available any longer. The AGWD (Automatic Generation of Wiring Diagrams) tool generates automatic technical drawings based on information from the (EWIS) database. This system is already operational at Fokker Elmo. TTA International, based in Dordrecht, also works with (a derivative of) this system, but in the automotive industry. Technical service provider SPIE Netherlands uses a 3D scanning device with which existing wiring systems can be mapped, in case, for example, the information is no longer available or has been compromised. The system is operational and was designed for applications in the processing industry.
A tool for testing the functionality and integrity of onboard wiring systems would be welcome. Currently, the testing is done by checking the electrical connection between two specific pins in the connectors on each side of the cable. But this does not reveal any information about the condition of the insulation. A non-destructive testing tool is interesting for any sector that must frequently test cables but does not want to or cannot undo them.
How do we continue?
The BAc program management of ELKINA wants to start new innovation projects from the propositions stated above. It is searching for companies and knowledge institutions that want to act as project initiators and/or would like to participate in the projects. The contributions can differ and may consist of, for example, supplying brain power, supplying research equipment and/or financial contributions. Development association REWIN West-Brabant will search for the additional financing for these new research paths.
This article is an appeal to all parties involved in the subject – installation and maintenance of wiring systems – that want to increase their innovative and competitive strengths. ELKINA, together with the interested parties, will select the most promising innovation projects before the end of this year.