When designing system solutions for entire aircraft materiel systems, an understanding of the operational requirements for the product that is, the characteristics, capabilities and performance the product must deliver, is of great importance. This text concerns the work to develop and define maintenance solutions for customers.
When designing system solutions it is also essential to understand how the design solutions affect the maintenance and support costs incurred by the customer. These system solutions greatly affect maintenance needs and complexity and therefore the life-cycle costs of the entire materiel system throughout the product life cycle.
In order to create a cost-effective complete solution for the entire aircraft materiel system, the following approach is appropriate to consider:
The author recommends the following texts that relate to this story: In chapter Creating value for customers under the heading Concept Methodology , in chapter Having a low life cycle cost under the headings Efficient working procedures are effective and Systems Engineering.
This section concerns the highlighted areas of A Journey of Change in the Aircraft Industry
The customer's operational capability is to conduct operational missions in different situations and for the entire fleet of aircraft to offer optimal availability over time. Accordingly, the customer must have an operationally reliable system with acceptable maintenance measures at a low cost.
This chapter expands on the approach required to realise this capability for the customer in a cost-effective manner.
When designing system solutions for entire aircraft materiel systems, an understanding of the operational requirements for the product that is, the characteristics, capabilities and performance the product must deliver, is of great importance. It is also essential to understand how the design solutions affect the maintenance and support costs incurred by the customer, since they greatly affect maintenance needs and complexity and therefore the life-cycle costs of the entire materiel system throughout the product life cycle. In order to create a cost-effective complete solution for the entire aircraft materiel system, the following approach is appropriate to consider:
This means that during the design phase one must first gain an understanding of how and under what circumstances a fighter aircraft is operated and, based on this, which operational reliability requirements apply. The financial perspective also restricts the choice of technical solution.
It is essential to consider aircraft and maintenance products as an integrated whole, so that this is reflected in the system design. This ensures that the product has the expected operational reliability characteristics, that is, general availability at a realistic cost level.
During development work, the design must be continually evaluated in relation to the operational reliability characteristics, which are to reflect the customer's desired capability. Evaluations are conducted to assess how much the design's maintenance needs limit availability, operational reliability and operating cost. Alternatively, one can express this as the optimal availability solution in relation to life-cycle cost.
3. Requirements for operating the product in the customer's circumstances and organisation.
When a customer orders and wants to commission a new fleet of aircraft, a maintenance solution is defined based on the desired operational performance and the number of aircraft the customer will have available. Other factors to consider include, for example, which maintenance products have already been designed previously and how the customer's organisation is judged to handle and conduct maintenance in peacetime, conflict and war.
In order to fulfil the customer's need to operate the aircraft, the maintenance solution is designed accordingly that is, a recommendation for a maintenance system is drawn up. This recommendation encompasses the maintenance resources that the customer will need for operation and maintenance, including tools and reserve materiel, as well as any training and changes to its infrastructure and organisation. This design work also includes the production of a maintenance and logistics solution for maintenance of a kind that is not favourably conducted at the customer/user.
The main task in the design work is to understand and produce a solution for a defence materiel system at operational level, for an organisation in both peacetime and wartime, in accordance with the specified conditions.
This means that in practice the principles for ILS (Integrated Logistics Support) are followed in order to build a technical system that is flexible and thereby useful and marketable to all customers.
Historically, the military aircraft industry has separated the development of the technical system, with the reliability and maintainability of the aircraft on one side and the maintenance precision of the maintenance system on the other. Once the design of the aircraft is complete, this has often resulted in discovering after the fact that the maintenance products and maintenance solutions are complicated and expensive for the customer. The customer has required a more complex organisation with more expensive maintenance and thereby higher life-cycle costs.
Consequently, this working procedure is not best practice for creating systems with low life-cycle costs. On the other hand, it may well be the case that development of the actual aircraft is more cost effective when there is no need to incorporate and consider all aspects of the customer's operational activities. All manufacturers of military aircraft have traditionally focused mainly on the development of the aircraft's tactical performance, functions and characteristics. Operation and maintenance design and the maintenance system the customer is to use in its operational environment have not received as high a priority.
At Saab Aeronautics, however, high operational reliability and low life-cycle costs have been a major focus for many years, much due to great emphasis being placed on these characteristics already during the pilot study phase and development of the Gripen. This has been implemented together with the customer by establishing an operational reliability programme to heighten awareness. This cooperation has resulted in dependability, maintainability and maintenance precision being strong contributory factors to the Gripen's outstanding system efficiency and low operation and maintenance costs.
By actively evaluating design alternatives early on, one creates the opportunity to choose solutions that lay the foundation for future cost efficiency and an overall low life-cycle cost. This can be illustrated in the figure below, which was included in the reasoning for the joint operational reliability programme for Saab and its customers.
The customer's operational capability is to produce operational missions in different situations and for the entire fleet of aircraft to offer optimal availability over time. Accordingly, the customer must have an operationally reliable system for being able to produce missions with acceptable maintenance measures at a low cost.
Offering the flexibility for numerous different user scenarios demands that the aircraft materiel system can handle different operational requirements. One must choose the right level of flexibility for the weapon system and design system solutions that provide high dependability, that is, low failure incidence, which is usually expressed as a high MTBF (Mean Time Between Failures).
Other conditions that affect flexibility are the customer's organisation and structure. Understanding which skills, maintenance resources and facilities the customer has available is central as the use of these resources can differ dramatically between operations in peacetime and operations in a crisis situation or war.
This means that maintenance solutions must be balanced between on the one hand having the ability to conduct different missions in the most effective manner and on the other having low life-cycle costs for the entire aircraft materiel system. Implementing resource optimisation and evaluating different system solutions are necessary to be able to compare the outcomes of these efforts and the resultant life-cycle costs.
Each design solution affects maintenance costs to a greater or lesser extent over a life cycle of 30-40 years. Accordingly, as early as the concept studies it is important to produce several alternative solutions and test them from a maintenance perspective, which is done to secure the customer's operational capability while achieving low life-cycle costs at the same time.
During development work there must be an understanding of the approach required to produce a well-functioning system solution that fulfils the customer's operational requirements from a broad life-cycle perspective. One must understand the intended use of the system and then develop system solutions that work for the customer. It is seldom possible to realise all of the customer's individual requirements. Instead, it is often a case of finding the best compromises.
Consequently, maintenance solutions require engineering capability combined with free thinking and the aim is to develop effective solutions in manageable parts, which is especially important in aircraft design. Defining likely chains of events in multiple scenarios and then finding different variations of them is a suitable approach to identifying different links for solving a crisis situation.
Different logistics solutions and supply chains for maintenance resources must be defined relative to the need for preventative and corrective maintenance. Based on these conditions, one can define the likely extent of the need for reserve materiel and maintenance and support systems for the bases out of which the customer will operate. The result is an optimisation plan for how the customer should allocate its resources.
The development of good maintenance solutions requires time to think, time to understand and time to formulate the actual problem and describe it in a solution. As a foundation for this, the development organisation must find out how a user thinks and operates, using generalisations based on several users to produce a design.
This most often results in an innovative working procedure where the development organisation is forced to consider the whole from the customer's operational perspective. If this knowledge and experience are thoroughly processed, they often contribute substantially to the design of a technical solution that delivers good maintainability and the necessary availability.
Below are a few examples of different approaches to conducting operational missions and which have completely different consequences for how the maintenance solution can be designed.
Conducting a particular mission requires four aircraft.
The first alternative is the best choice for limiting the costs. The second alternative better secures mission execution.
When designing and choosing a system solution, it is important to consider which parts of the system's component subsystems or equipment must be recyclable as regards the environment, maintainable as regards efficiency and reusable following modification or upgrading. It is also important that the operational reliability and availability requirements are thoroughly considered in order to determine which maintenance solutions are suitable.
One can approach the design perspective in two essentially different ways:
When designing a system solution one must consider what it will cost to:
These four aspects have a major impact on the life-cycle cost.
This requires an awareness of the design consequences for the entire aircraft materiel system, as well as clarity as to which restrictions a particular design choice entails.
A customer agreement often includes assurances of a certain life-cycle cost for the customer's aircraft materiel system. Here we are sometimes faced with different kinds of dilemmas and must balance different types of conflicting requirements, such as when high operational performance and functionality are set against a low life-cycle cost.
Example: A piece of equipment can be switched for another piece of equipment that better fulfils the customer's operational requirements. The customer gains enhanced capabilities and high operational performance with the new system solution.
However, if the new equipment has a design and technical solution with a short service life, and which also requires more maintenance, naturally this entails a higher life-cycle cost. If the new equipment must be chosen, with greater demands on maintenance that requires another more complicated maintenance solution, what happens then?
If there is a contractual requirement for a specific (or relative) level of life-cycle cost regarding the aircraft materiel system, the consequence is often that measures must be taken on other systems or equipment to keep life-cycle costs at the correct level. This means that it is important to early on in the design phase assess how different types of system solutions may affect maintenance and life-cycle costs.
When developing the aircraft architecture and design, maintenance product design is an integrated part of the work. During these efforts, an assessment is made of which operational capabilities the aircraft is to have. After this, the optimal maintenance solution for each customer is assembled from the developed products. Wherever possible, unique maintenance products for a specific customer are avoided. The customer is to receive a product that includes a maintenance solution that delivers a low life-cycle cost (LCC).
Naturally, the customer has a strong interest in being able to influence all parameters that generate life-cycle costs. The LCC includes the following:
In the development of the Gripen A/B – and later the Gripen C/D – an effective maintenance concept was defined based on a Swedish military perspective. A product focus on the operational reliability of the entire materiel system was employed, highlighting the reliability and maintainability of the technical system and the maintenance precision of the maintenance system. The maintenance solution was essentially developed and fully adapted to the needs of the Swedish military. Over the years, more customers have been served with different needs, requirements and philosophies regarding maintainability. This has meant that the maintenance solution has been adapted to unique customer circumstance but is still based on the Gripen's underlying maintenance concept.
In order to offer cost-effective maintenance solutions, maintainability must be considered and incorporated already during product development. Consideration must then be given to, for instance, which type of equipment the maintenance applies to and how complicated maintenance can be in different situations as regards resource requirements and time frames. For example, some actions cannot or should not be taken in an unprotected environment, so instead an assessment is made of whether the action can be simplified, such as by modularising the design or developing suitable resources for creating the right environment for taking the action.
The picture shows an engine replacement in field conditions
If access to a maintenance workshop is required to conduct maintenance measures, designs and equipment for this end are produced already during the product design work.
Even if access to a maintenance workshop is available, the product design must be well-considered so that maintenance can be conducted efficiently and with short lead times.
ILS includes all actions for effective maintenance and is a management process used primarily in the defence industry, such as by the Swedish Defence Materiel Administration. It is used to ensure that a system or product can be used, maintained and kept at a low cost while fulfilling strict requirements for dependability, operational reliability and maintainability.
Important prerequisites to be aware of include the customer's requirements for tactical performance as regards the types of missions for which the product will be used and the frequency at which these missions will take place.
Customer-specific conditions and circumstances as regards organisation, capabilities, restrictions and expertise must be carefully considered in the design process.
From a design perspective, it is also necessary to know how operation and maintenance will be conducted within the bounds of the customer's plans for operational capability.
The aforementioned knowledge of the customer's requirements must be used initially in the design work to produce a conceptual design and for any requisite analyses and simulations. General system requirements and performance requirements must be considered in a life-cycle perspective in this work.
These analyses and simulations will result in detailed requirements for system performance and the system's dependability and maintainability.
One must also understand the consequences of technical decisions, as maintenance costs must be kept at a reasonably low level.
A simple example of this is ensuring that the chosen system solution cannot cause false alarms and thereby cause the customer to cancel operational missions and incur unnecessary costs for replacement parts and service measures.
Producing an effective maintenance solution for the Gripen E required development of both the approach to maintenance concepts and the way in which maintenance products are delivered.
Moreover, major technological developments have enabled model-based working procedures, which in turn have enabled the analysis of customers' maintenance needs based on their tactical loops early in the design work. This has enabled the creation of models already during the design stage of product development, providing a relatively easy way to test and evaluate different types of systems and technical solutions.
The components required for effective maintenance solutions, together with their interdependencies, can be divided up as follows:
Essential as regards performance in the execution of operational missions is:
The capabilities required to conduct maintenance include:
Maintaining good performance over time requires that the following components be taken into consideration:
Actual product capabilities include:
The components which affect the capability to manufacture are:
Essentially, the maintainability and manufacturability of maintenance solutions face the same requirements as the entire aircraft.
To a large extent, the design of both a maintenance product and a production item must fulfil the same basic requirements.
This analysis is used as a basis for defining the design philosophies for the product and the maintenance concept.
In the design work for the Gripen E the maintenance products were designed as an integrated part of both the aircraft and the entire materiel and maintenance system. The design decisions were based on the operational capability the product was to provide the customer in its tactical loop. Accordingly, when creating a maintenance system it was necessary to analyse and simulate different customer requirements to see how they could possibly affect the design work.
Product responsibility for the Gripen E encompasses not only the aircraft, but also the aspects of the materiel system regulated by the contract. Product responsibility also includes responsibility for realising the customer's maintenance system.
The work on ILS for the Gripen E was conducted as an integrated and iterative process, so as to influence the design process and to develop systems and products.
The assignment was to design a technical system to enable the execution of a customer's operational missions with minimal maintenance at a low cost. Consequently, the concerned design parameters are system performance, system dependability, maintainability and the design of effective maintenance products.
In order to realise the customer's maintenance system, resources were developed to deliver and install the maintenance system upon commissioning. Moreover, resources were developed to train personnel and secure the ongoing operation of the maintenance system.
Accordingly, the working procedure for the design of the Gripen E entailed an overall assessment of operation and maintenance requirements already during the design work. The purely customer-specific optimisation of operation and maintenance measures was handled in consultation with the customer, so as to take into account its organisation and capabilities.
To summarise, this provides an overarching design perspective based on operational capability requirements, resulting in a complete solution comprised of two main components. One component comprises the system design based on operational reliability aspects of the technical system design while the other comprises the maintenance solution to be realised at the customer, taking into consideration the specific requirements and circumstances of the customer.
The entire ILS concept is a part of the product responsibility. The ILS for the Gripen E encompasses the whole, from design to mission execution, and includes two main components.
Designing the technical system comprises equipment integration in the aircraft and for the entire weapon system. All component subsystems have been developed within the various technology areas and materiel groups. Responsibility for securing the entire maintenance solution is assigned to a specific materiel group.
The technical system includes system design and operational reliability, which encompass the following components:
Realising the customer's maintenance system, which constitutes the maintenance solution, includes the following steps:
An understanding of a few different design perspectives is essential to good product and system design.
Function-oriented design focused on availability and performance incorporates characteristics that enable:
One must achieve a balanced design solution and maintain a holistic perspective, so as to assess maintainability in terms of the need for and frequency of servicing or fault resolution.
An installation perspective is used to review design and construction solutions by considering the practicalities of accessing equipment/devices (replacement units) without major interventions in servicing, fault resolution and repair work.
Another perspective to be considered in design work is how the functional integration is to be realised in order to achieve a useful maintenance solution. Here it is important that the construction is designed in a way that ensures compatibility between the aircraft's systems and the systems used for service and maintenance, not least so as to be able to handle fault indicators from the aircraft.
From an equipment perspective, it is important to consider how testing, troubleshooting and fault finding of the aircraft's different systems should be managed, in particular when actions must be taken in a workshop.
So as to achieve cost efficiency, analyses are made of different alternatives for conducting work to repair or replace equipment and systems in the aircraft in maintenance workshops.
Maintenance-related design – technical and logistics systems
Maintenance-related design can be split into two parts, the technical system and the logistics system.
The technical system includes maintenance products that are designed to be an integrated part of the aircraft design. The basis for this being that design decisions shall be devised so as to provide effective operational use of the product.
The logistics system is designed for an efficient supply of reserve materiel and rational service and repair activities in a workshop environment. The prerequisites for the design of the logistics system are based on customer-specific requirements.
The maintenance system is realised by assessing the extent of operations (number of aircraft), the customer's organisation (size and competence), the working procedures in place and the available resources, based on the customer's specific requirements that are not associated with operational activities.
Working with maintenance-related design requires that the concerned development teams have an integrated working procedure and understand how to achieve an effective supply chain. Since the technical system encompasses the entire maintenance system, one must design effective flows for the entire logistics system, including all maintenance products.
This working procedure has been an important part of the work on the Gripen E for creating the right availability and performance for all the various systems and maintenance products that the customer needs for its operational capability in peacetime, crisis situations and wartime.
Most important in all design work is to assess how service, maintenance and repairs are to be conducted and which environment is suitable depending on the situation. Particularly important is to determine when service measures can be performed in an outdoor environment and when workshop resources are required.
The development work for the aircraft features an integrated development team with members from different technical disciplines who together make these assessments throughout the design work. This working procedure has evolved considerably within the bounds of the Gripen E project.
Examples of issues where responsibility for finding a solution falls to the integrated function team include:
The same type of issues exist for the many different operational situations the customer faces. Examples include use in peacetime, use in crisis situations or wars, and participation in international interventions.
The main components affecting the design work are the types of operational missions and the types of external loads that are required (such as weaponry, extra fuel, surveillance equipment and so on).
One also needs to specify which resources are needed in the shape of equipment for conducting maintenance and service, as well as which competencies are required for maintenance measures, which personnel are required and where and when they are to be available. It is important to keep track of when different planned maintenance measures are due for each individual aircraft, so as to avoid disruptions to mission execution. The logistical flow of spare parts to maintenance workshops and depots must also be included in the planning.
Design decisions take into account customer-specific requirements for the logistics system. A well-functioning logistics system is a prerequisite for practically achieving the desired operational capability.
Consequently, it is necessary to consider how the maintenance products can be used at the customer's facilities. The design of the customer's logistics system is central to the provision of maintenance and reserve materiel, for both the aircraft and the entire materiel system (including the weapon system).
This requires assessments of how flexible and comprehensive the maintenance system needs to be, with consideration for the user's specific requirements and how existing maintenance operations are organised.
Moreover, one must also define which maintenance measures offer no alternative other than to be conducted at Saab or an OEM (Original Equipment Manufacturer).
The maintenance solution (see the outline diagram below) includes both the activities conducted by the customer and those which must be conducted by the manufacturer or an OEM. All necessary logistics can often be provided by a third party and are also an important part of the maintenance system.
The development work for the Gripen E included a large number of analyses and simulations to understand how different system security requirements should be managed. Many in-depth analyses of the entire materiel system were conducted in order to balance system security requirements with availability and functional requirements.
Test and function monitoring development were very central to the work on the aircraft. Specific tests were conducted to assess fulfilment of the actual requirements, which were based on performance analysis, availability and system security.
This work balanced requirements for conducting secure peacetime operations with the requirements for effective operational activities in wartime conditions, with assessments of how the materiel system would function throughout the entire operating phase.
The diagram shows two loops for the operating phase. The first concerns feedback from customers and experience from operations monitoring. The second comprises technical development and the introduction of new technology during the operating phase. Design improvements are generated in both loops. These can affect the aircraft, the maintenance solution or both.
In order to ensure the practical usability of the Gripen E, simulations were conducted to assess dimensioning factors for the constituent main components of the entire materiel system.
Examples of main components in a simulation include the following parameters:
The images below present a general scenario in which a mission is conducted using two aircraft at a time, with each sortie lasting 1½ hours. This example takes into account the main components in the shape of primary resources.
Comment: One can also add planning activities for how many hours a day the mission is to comprise and how many days the campaign is to last.
When assessing how to handle availability and performance requirements for the technical system of the Gripen E, the entire value stream was reviewed.
In the development work for the Gripen E, the analyses of the availability and performance requirements for the technical system were central to achieving a maintenance-friendly product design. To this end, many descriptions and models of the entire maintenance system were produced.
Analyses were also conducted to gain an efficient maintenance flow from when a maintenance need arises to the verified restoration of the function in the aircraft.
In order to identify any faults in the aircraft, a testing and monitoring system needed to be designed in such a way as to secure the opportunity to verify indicated faults in the workshop.
One must also ensure the maintenance functionality of all support equipment, whether used in the field or a workshop.
In addition, the division of instructions and product data between aircraft, support equipment, publications and structured data (LSAR, Logistics Support Analysis Record) was defined.
The result of this work was that maintenance products and system and product design could be integrated, thereby ensuring both shorter lead times for design work and effective maintenance measures.
Several teams were created to optimise the work on maintenance solutions for the Gripen E.
One team worked on assessing how to incorporate maintenance aspects in product design and system solutions so as to integrate maintainability with all system solutions.
Another team worked with the integration of maintenance solutions with a focus on optimising different types of resources. This included developing supplier capability in understanding how to conduct maintenance measures and maintenance level analyses (Level Of Repair Analysis, LORA). Consequently, it is important to be able to assess when an item needs to be replaced, repaired or discarded based on cost considerations and operational requirements.
The different materiel groups within the development organisation focused on maintenance based on the following aspects:
To keep everything in order, a coordinating team was used to assess the entire design from an availability and maintenance perspective. This encompassed integration responsibility to secure the characteristics and functions of both the aircraft and the entire weapon system from an operational reliability design perspective. The teams also worked on the design of each individual customer's maintenance solution for the entire weapon system.
One of the most important results from working in teams is a manual for working with preventive maintenance. The manual describes the application of different standards, such as ATA, MSG3 and S4000M, in the Gripen E project.
The work to analyse and define the content and scope of the preventative maintenance programme was conducted by system specialists and members from each of the materiel groups. All analyses and proposals were presented at different review meetings where decisions were made.
Examples of areas covered by the manual include the following:
It is especially important that everyone with design responsibilities has insight into the customer's practical and routine operations. Otherwise it is difficult to know how to choose system solutions that are suited to operation in actual operational missions. This requires specialist training and instruction in the operations of different customers' air forces.
This training and instruction ought to include knowledge about design for operation and developing system solutions suited to operation, as well as reviewing the costs of manufacturing and the reserve materiel supply of equipment and other parts assessed from a life-cycle perspective.
When producing maintenance solutions it is important that the criteria for the different alternatives are clearly documented. This documentation ought to include the basis on which decisions were made in order to assess the effect, performance and consequences of a particular solution and to later be able to review system and maintenance solutions.
The model-based working procedure enables a 3D model to act as the carrier of all information for a system; how it is used, maintained and so on.
The model-based working procedure with 3D modelling has been used for many years for designing complex structures in aircraft and for developing complex systems for controlling functions and equipment in aircraft. Both now and in the future this working procedure will to a large extent also be used for developing maintenance solutions. 3D modelling is used in design and maintenance preparation to verify access during maintenance measures in the same way that 3D models are used to ensure access for fitting parts in the aircraft. This enables a design to be evaluated at very early stages without any major consequences – in terms of costs or time – if any alterations are deemed necessary.
In maintenance design 3D models are also used to identify and visualise maintenance measures, which with consideration for access and handling ought to be coordinated. Such visualisation improves reserve materiel scoping as an early assessment can be made of the extent of required measures.
With the continual use of simulations, a system's availability and durability can be analysed as regards operational reliability characteristics, maintenance strategies and resource allocation. This is then used to show how availability is affected over time by resource limitations with varying amounts of flying time.
In simple terms, one could say that open methods apply. Customers can explicitly request analyses conducted using specific optimisation and simulation tools rather than request spare part optimisation. In this way, the customer wants to gain full insight into how the optimisation has been conducted and what baseline data was used. Moreover, the customer can then use this data in its own analyses.
The trend towards larger service commitments corresponding to PBL (Performance-Based Logistics) is driving the need for the capability to conduct logistics analyses. That which was previously the responsibility of the customer/user is now being transferred to the supplier.
PBL entails increased delivery responsibility for the supplier. On a scale of one to six, the following delivery commitment comparison illustrates the increased responsibility.
Level 1 – Delivery of spare parts.
Level 2 – Delivery of maintenance, repairs and overhauls.
Level 3 – Delivery of the entire supply chain.
Level 4 – Delivery of the entire logistics flow.
Level 5 – Delivery of complete system support (turnkey solution).
Level 6 – Delivery of full system support until the handover of the prepared aircraft for an operational mission.
PBL also provides increased opportunities to both optimise the logistics system and analyse and alter the product from a holistic perspective. In this case, the organisation's ability to conduct an effective logistics analysis using correct data is completely decisive to creating a useful product and commercial success.
In this context, we can talk about minimal environmental impact, which is as equally an important design parameter to consider as, for example, operational reliability in achieving the best possible system efficiency at the lowest possible life-cycle cost. Accordingly, strict demands are placed on an integrated system design and the design of maintenance solutions so as to minimise environmental impact throughout the product's entire service life.