System Thinking

Introduction

The descriptions in the different sections about system thinking present the fundamental areas of expertise required by a company that develops advanced products. Understanding a customer's true needs requires cooperation with the customer and thorough concept work.

To then transform this knowledge into a practical operational solution requires broad expertise and extensive practical experience. Here we also present how technical development has progressed in one of the most difficult areas, namely control systems for fighter aircraft.

Moreover, we describe ways of working with standards, which is essential to running effective operations in aviation development.

Concept Methodology

This section briefly describes why concept work is of central importance to both the customer and Saab.

If you would like to read this entire text, it can be found in Concept Methodology.

The two primary purposes of concept development are to engage the customer and the market and to use increased understanding to reduce the risks associated with the development, production and operation of the product.

Since aircraft systems take a long time to develop and are to be used for several decades, the need to identify requirements is of the utmost importance. A number of stakeholders are associated with the development and further development of aircraft systems. The core stakeholders are those who are going to finance, own and use the system, that is, society, the customer and the user. An important part of concept work is supporting the dialogue between stakeholders by analysing and providing feedback on their queries.

Thorough concept development is a fundamental capability and a prerequisite for developing future military operational capability. Conceptual aircraft system development is an ongoing activity at Saab. Operations identify future market needs and review trends in tactical and technical development. This also further develops the company's expertise and capability in aircraft system analysis.

Aircraft systems are highly complex, which means that the development of new systems places great demands on expertise in and support for describing and analysing tactical and technical solutions. The work is iterative and divided into several stages in order to increase system solution maturity, relative to the need for which it is being developed. But also the need to be developed in sync with the opportunities presented during the concept's evolution, which is why the work is conducted in teams comprised of usage analysts and technology developers.

The maturity process in a concept study is divided into several stages. The initial stages aim to tighten up the solution space to find the optimal solution. The analysis must be conducted by experienced analysts at a high system level to keep costs down. The main aim of the final stages is to offer a robust system solution that reduces the risks associated with the development and use of the future product. This sets demands for an in-depth analysis, as the results are used as a foundation for the agreements entered with the customer.

Tactical Loop

This section describes how an actual operational mission is conducted. Here you can also read about the full capability, from a mission conducted in a geopolitical context in which the Gripen was used. The text encompasses decisions made by the UN to operational decisions made by a pilot.

If you would like to read this entire text, it can be found in Tactical Loop.

From government decision to operational intervention in Libya in 23 hours – How is this possible?

In order to be flexible and fast, with military aircraft systems we must understand the fundamental conditions for advanced and complex systems to operate in the face of dynamic threats. What is it, then, that we need to understand?

We must start by understanding the customer requirements and the global security context in which the customer is to act. We must also understand the political agenda, as well as why the customer wants an advanced defence system. Here we describe the requirements for developing advanced military aircraft systems and how Saab transforms them into development work in practice.

In order to exemplify the requirements and the conditions, below a user describes how an operational mission is conducted.

The Libyan regime's violence against its own people resulted in the UN Security Council deciding on 17 March 2011 to establish a no-fly zone for the Libyan air force. The decision was founded on resolution 1973, which was adopted under Chapter VII of the UN Charter. The Security Council established that the situation in Libya comprised a threat to international peace and security. In order to realise the decision, a NATO-led intervention was to be executed, the aims of which included maintaining the no-fly zone.

On 28 March 2011, NATO formally requested that Sweden participate in an international intervention force. The Swedish government proposed in a bill presented on 29 March 2011 that an intervention force be sent to Libya. The bill was submitted to the Swedish parliament's joint committee on foreign affairs and defence (UFöU) for consideration.

On 31 March 2011, the joint committee on foreign affairs and defence voted to support the bill to participate in the international no-fly zone over Libya initiative and the bill was presented to parliament for approval. On 1 April 2011, the Swedish parliament adopted bill 2010/11:111 on Sweden's participation in the international military intervention in Libya. There were two conditions in the decision, which meant that the force was not permitted to attack ground targets other than in self-defence and that the intervention should last a maximum of three months.

The Swedish operation in Libya was originally designated Flyginsats Libyen 01 (FL 01), or Aerial Intervention Libya in English, later altered to FL02 when the mission was extended.

The force that Sweden deployed comprised eight JAS 39 Gripen fighter aircraft, a TP 84T transport aircraft and an S 102B Korpen reconnaissance aircraft. In addition to the above, the force comprised about 250 people.

On 9 June 2011, the Swedish government presented a bill to extend the intervention by another 90 days, with the bill also reducing the number of JAS 39 Gripen aircraft from eight to five. The Swedish parliament adopted the bill on 17 June 2011.

The Swedish intervention with Gripen aircraft comprised a reconnaissance mission, and such missions require thorough planning within the armed forces.

Feasibility – restrictions and planning conditions

In order to execute a mission, the user must consider a number of factors, and the military threats to which the unit can be exposed is a prime example. Other planning parameters depend on where the operation is to be conducted and the environment in which the unit is to act. In the case of Libya, the unit was stationed at the Sigonella base in Sicily, Italy and the task was to conduct aerial reconnaissance over Libya.

A few examples of important issues to consider include: Distance – how to secure a fuel supply? How to cooperate with other nations in the intervention? How to communicate and issue orders? What weather conditions need to be taken into account? How would a rescue mission be executed if an aircraft was lost? What equipment and weaponry are required for the mission?

The type of maps needed is a central issue, and it can take a great deal of effort to obtain maps suited to the mission to be conducted.

There can also be specific conditions in the area of operations that must be considered. One example of this is that the type of fuel available at Sigonella base is adapted for the US Navy.

Weather conditions in the area are also special, with a great deal of lightning and high volcanic ash content in the air, as well as sand from sandstorms. Naturally, this affects aircraft and equipment.

The mission – what was done?

On 2 April 2011, the first fighter aircraft from Swedish Air Force Wings F 17 and Ronneby Airport took to the air with the Sigonella base in Italy as their destination. From parliament adopting the bill to the aircraft landing at Sigonella air base in Sicily, Italy, took 23 hours.

The mission was a tactical reconnaissance task to photograph potential targets. Example: SA-8 surface-to-air missile battery discovered by the Gripen EW system, photographed by the Gripen and neutralised by other NATO units.

 

Statement from NATO

"The Gripen squadron is of great value and highly prioritised. They have a very fast loop from landing to interpreted image delivery. NATO Command is very pleased with the operation, which was quickly executed with high-quality results. The important message is that the squadron does a very good and much appreciated job, they are in a real war with a passive opponent who has a very real ability to combat aircraft with advanced surface-to-air missiles."

Geographic location

Operation area.

Photo taken during the surveillance mission

Tactical loop for the mission – how it was accomplished

Planning and execution follow a tactical loop that is a carefully defined process for how a mission is conducted. From when the mission starts to when it finishes, data is analysed with the results summarised and sent to command for further interpretation and decisions on new measures. Mission analysis involves both recommending further operational actions and defining maintenance measures to ensure the availability of all weapons systems for the next mission.

The figure, Tactical Loop, illustrates the principle relations between the different types of preparations.

 

Execution of the tactical loop – search for air defences in Brega

Below, one of the Swedish Armed Forces' pilots called Duke Talks about a mission in the FL01 intervention in Libya. (Source: Flygvapenbloggen).

03:00 MSO compiling mission into a MSS-planning

06:00 Initial intelligence brief

MSO mission brief

ATO/ACO and mission study

Mission Data Card (MDC) completed

07:00 Mission brief with wingman. Detailed walk through of complete sortie

08:00 Step Brief, weather and threat situation update just before BÖS

08:20 AC pre-flight

09:00 Take off AAR, Recce mission over Brega, AAR, Defensive Counter Air protecting tanker completed

13:00 AC touchdown Sigonella

13:20 Post mission brief

~15:00 Mission report

First we present the flow described in the story and the tactical loop that Duke conducts together with others involved in the intervention.

With a mentally projected bar I pry myself from bed at 05:10. I'm to lead the first shift of two during the day and planning starts three hours before take-off. The first thing that happens at division is that the two of us who are flying are briefed by the intelligence officer on the situation in Libya in general and where we're going to fly more specifically. Today there have also been reports of hostile air defences being fired, so things take a little longer than usual.

Following the briefing a mission support officer – who has been up working half the night – is waiting to show us how the sortie has been planned. The basic setup is perfect as usual and after a little input from us and some discussion about which altitude we should fly at she disappears to gather all the papers we need. She also loads a memory stick with the mission information we need to upload to the aircraft later.

Now it's time to check out the personnel recovery situation in the area where we are to fly. We go through our EPA – Evasive Plan of Action – to see whether it suits our mission or if we need to make any changes. There we write down in detail how we will act if we have to eject over hostile territory, such as how we should use radio, where we might find friendlies and the current code words.

From the ATO – Air Tasking Order – we can see roughly what we are to do on the mission. Today we are going to recce (Ed. note: abbreviation for reconnaissance) a number of air defences in and around Brega in Libya and then switch to an air defence role for the second half of the shift. We have two aerial refuels at our disposal so it ought to be fine. To be sure, I ask the MSO to carefully check a fuel alternative with another load to see how we can maximise the chance of mission success. My number two – Edge – is tasked with following up on this and, if necessary, compensating the navigation for any unpleasantries, such as the suspected air defences. He also makes a few small changes to the EPA to account for the rising temperature in the area; it's getting close to 40 degrees.

Two hours before start I present the mission brief to my number two. We go through every part of the shift in detail. The altitudes we will use, the planned route, countermeasures against air defences, what to do if certain types of faults arise and so on.

The equipment we carry weighs about 20 kilos. It's still below 30 degrees, but the forecast is for about 35 degrees in the shade today, so we need to hydrate as much as possible so that we can cope in the desert for as long as possible should anything go wrong. Libya is one of the hottest countries in the world, and is mostly desert. Having equipment that is well suited to these conditions directly affects our chances of survival.

At the step brief before we go to the aircraft we get the latest weather update. They also check whether we've received the latest tactical information and done everything that needs to be done to fly. Today, just like almost every day here in southern Italy, the weather is good.

Forty minutes before take-off we sit in the aircraft to conduct pre-flight procedures. This doesn't take long, but you have to check everything from problems with the aircraft to problems with the flight plan. Today everything goes as it should and we spend 20 minutes just sitting in the aircraft waiting to take off.

Once our take-off slot comes round, we set course for our first tanker for aerial refuelling. We do this just before we enter the area to be able to take as many photos as possible before the next refuelling. Today we are refuelling from a French KC-135. Most important is that it goes well. Travelling at 600 km/h and flying a probe – that you can't see – into a 70 cm wide basket, mostly made of metal, half a metre from a plastic casing, demands all your attention.

Once we've refuelled things get serious. The checklist for going feet dry, that is, flying in over land, is reviewed by both of us. The aircraft is now fully configured to face real threats at short notice. The first shift felt unusual flying with live weapons, which we don't normally do on training missions. We increase speed and drop to tactical heights. I photograph with our excellent reconnaissance capsule while Edge watches my back.

I work mostly head down, which means that I'm looking at my displays to manage the sensor while Edge keeps a lookout for other aircraft and hostile air defences. Unlike in safety-conscious Sweden, the tactical air traffic controllers (call sign Magic) are not as good at informing you about our own aircraft, and sometimes you don't even have radio contact, so you have to keep a lookout. Link 16 that we just got for the Gripen helps a lot, however, as you can see the other aircraft on a map display.

The capsule has a good day today and all targets are photographed without incident. Bingo fuel – the fuel level required to fly home – is approaching and we request higher altitudes towards the tanker areas for renewed aerial refuelling. When we reach the second tanker two British Tornado aircraft are already refuelling. My aircraft shows that the limit has been reached, but with a little mental arithmetic and risk management I conclude that a little less fuel will be enough to make it home, so we can wait a few more minutes.

The second part of the mission is DCA – Defensive Counter Air – where we accompany tankers and other aircraft and protect them from any aerial threats. The Gripen is multi-role and by pressing a few buttons my bird is now configured for aerial targets.

From our patrol route I can see with our thermal camera how the war is being fought down below, further inland. Grenades and firing are clearly visible, but at our current distance – feet wet – I can't discern individual people. We also take the opportunity to use the same camera, but with the daylight function, to check one of the known SA-5 sites for activity. Gaddafi has the capability to repair his air defences, but hopefully not without our knowledge.

 

Technical Capability Development Of Control Systems

This section describes the historical development of control systems for military fighter aircraft and how Saab's work has developed in this technology area. We describe how different control systems have developed from the 1940s up until the 2000s with the JAS 39 Gripen.

If you would like to read this entire text, it can be found in Technical Capability Development of Control Systems.

Historical development of control systems

This part describes the historical development of control systems and how Saab’s work has developed in this technology area. We describe how different flight control systems have developed from the J21 in the 1940s up to the Gripen in the 2000s. The flight control system is one of the most advanced systems found in military fighter aircraft. Its functionality and performance set the level of operational capacity of a military fighter aircraft.

In order to see the development of flight control systems for military fighter aircraft in context, we first need to understand the basis of how control systems work. The following text provides a very brief description of control systems and the different system solutions used in Saab’s various military fighter aircraft.

One of the most central issues for the Swedish Air Force was to reduce the vulnerability of the entire air defence system. In the 1950s, the air force had realised the vulnerabilities associated with fixed air bases, so they developed a concept for road bases along normal roads. Such road bases also had adjacent parking areas for aircraft with maintenance capability. As a consequence, the aircraft needs very good take-off and landing characteristics, as runway length on a road is very limited.

Mechanical control system

The Saab J 21 was developed in the 1940s and featured a design with twin tail booms and a rear-mounted propeller. It was the first aircraft in the Swedish Air Force to use nose landing gear. The aircraft design offered the pilot good visibility, but resulted in cooling problems for the engine and the propeller could injure the pilot should he need to leave the aircraft in flight. As a consequence, Saab developed a gunpowder-powered ejector seat that shot the pilot out and over the hazardous propeller area. Following the end of the Second World War in 1945, Sweden gained access to foreign jet engines and a version of the Saab J21 with a jet engine was developed as the Saab J21R.

Saab J21

The earliest control systems from the 1940s such as those on the Saab J21 were mechanically reversible, where the pilot could feel the force of air on the control surfaces via the mechanical control system as the forces were fed back to the control stick. The pilot could feel the force of the air in the control stick. High speeds resulted in greater forces in the control stick, and thereby smaller control surface movements. Low speeds resulted in lower forces in the control stick, and thereby larger control surface movements.

Flight control system for the Saab J21A/R – the mechanical reversible system

Saab J 29

The 1950s saw the development of the Saab J 29, which was given the nickname “The Flying Barrel” and was a single-engine Swedish fighter aircraft. From 1954 onwards, all combat and attack aircraft were rebuilt and fitted with afterburners, enabling the aircraft to set speed records for the time. At that time, the J 29 was considered equal to the best American F-86 aircraft and Soviet MiG-15 aircraft.

Due to the high speeds, the pilot required help with controlling the control surfaces at high speed, so the flight control system in the Saab J 29 was equipped with servo assistance. The pilot could still feel the force of the air from the control surfaces fed back through the control stick.

Flight control system for the Saab J 29 Tunnan – the mechanical reversible system

Saab J 32

The latter part of the 1950s saw the development of the Saab 32 Lansen, which was a two-seater fighter aircraft with all-weather capability which came in three principal variants. The Saab A 32A was an attack version with all-weather capability. The fighter version with all-weather capability was called the Saab J 32B and the reconnaissance version was named the Saab S 32C.

The Saab J 32B Lansen was the first ever Swedish aircraft to break the sound barrier. The aircraft was subject to very high forces, with the pilot requiring help from the servo to control the control surfaces. This meant that the pilot could no longer feel the force of the air through the control stick, so artificial control stick feel was implemented using springs and dampers instead.

Flight control system for the Saab J 32 Lansen – mechanical system with full servo

Saab J 35

The Saab J 35 Draken was developed to fulfil the need for a fighter that could intercept the new bombers with nuclear warheads introduced during the 1950s.

The aircraft design was based on a narrow fuselage with a double-delta wing configuration. This type of wing offered good flight characteristics at high speeds thanks to the inner, more arrow-shaped wing. The outer wing was complementary, displaying good performance at low speeds.

The Saab J 35 Draken was designed to intercept supersonic enemy aircraft which meant it required full servo and, moreover, assistance from an autopilot system to improve the poorly dampened pitch characteristics at supersonic speeds. The flight characteristics were improved with the aid of the autopilot while the pilot’s sense for the control characteristics were determined by the mechanical control system.

Flight control system for the Saab J 35 Draken – mechanical system with full servo + pitch damper function (analogue)

Saab 37

The Saab 37 Viggen was a fighter aircraft that came in four different variants, as well as a trainer (SK 37). The aircraft had a double-delta wing configuration with so-called canard wings (extra wings forward of the main wings) which made it possible to land at lower speeds. A reversing system made it possible to change the direction of the air flow with the help of a thrust reverser when landing on the ground. This resulted in the aircraft being able to land in a very short distance: less than 500 m even on slippery surfaces.

The AJ 37 Viggen went one stage further improving the pilot’s sense for the control characteristics by using a force sensor on the control stick. The flight characteristics were improved by adding stabilising and damping signals from the autopilot to the control surfaces commands. The autopilot on the AJ 37 Viggen was analogue. The components in analogue autopilots have varying tolerances, meaning that each aircraft was unique and could display slightly different flight characteristics.

Flight control system for the Saab AJ 37 – mechanical system with full servo and full authority + limited 5 deg analogue FCS

The Saab JA 37 Viggen was the first aircraft in the world to feature a digital control system added to the basic mechanical control system. The digital control system of the JA 37 could eliminate the variations in tolerances found in analogue control systems.

Flight control system for the Saab JA 37 Viggen – mechanical system with full servo and full authority + limited 5 deg digital FCS (first digital FCS in the world)

All of the aircraft described above were statically stable basic aircraft which could be flown using their mechanical flight control systems alone.

 

Electrical digital control systems

The beginning of the 1980s saw the start of an experimental project, ESS01, to demonstrate that Saab could fly using a three-channel asynchronous electrical digital flight control system for the future Gripen aircraft. This is where Saab’s journey of change towards an electrical digital flight control system with full authority began, paving the way for a statically unstable basic aircraft and the dramatically improved flight characteristics of such modern statically unstable aircraft.

JA 37-21 ESS01

A Saab JA 37 Viggen was rebuilt into an experimental aircraft called the JA 37-21 ESS01, which was used to test a full authority electrical flight control system. The change meant that the aircraft’s flight control system became a three-channel asynchronous full authority (±30 degree trailing edge control surface) electrical digital flight control system with a mechanical backup system.

Flight control system for the Saab JA 37 ESS01 – three-channel digital full authority fly-by-wire FCS with mechanical backup

Other control systems

As a comparison, the Tornado and Concorde used similar control systems. The Tornado is a twin-engine fighter that was developed in three different variants designed by a tri-national consortium made up of companies from the UK, West Germany and Italy. The Concorde was a supersonic passenger airliner and was developed in a collaboration between the French company Aérospatiale and BAC in the UK.

JAS 39 Gripen

The experience gained from the JA37 formed the basis for the design of the flight control system in later aerial vehicles; one aspect in particular is the monitoring of calculations, which was used as a basis in the development of the Gripen autopilot, designated the SA11.

The Gripen is a modern statically unstable aircraft with such good performance that it cuts through the air with little energy loss. This instability must be continuously parried using an active counter-command from the autopilot so as not to diverge.

Flight control system for the Saab JAS 39 Gripen – three-channel digital full authority fly-by-wire FCS with digital backup system

Control system basics

In order to understand the function of a flight control system, below we describe the difference between conventional statically stable and modern statically unstable aircraft.

The figure shows a comparison between stable and unstable Aircraft.

Conventional statically stable aircraft

In a conventional statically stable aircraft the aircraft has an inherent stability which requires a large wing area and causes a lot of drag that slows the aircraft when turning.

Examples of conventional statically stable aircraft include the Saab J 29 Tunnan, Saab J 32 Lansen, Saab J35 Draken and the Saab AJ/JA 37 Viggen.

In a conventional statically stable aircraft the lift of the wing acts behind the centre of gravity, making the aircraft automatically free float into the wind. The aircraft has a naturally restoring aerodynamic pitching moment and therefore natural stability.

In order for the aircraft to turn, the nose must be held up by a downwards counter-force from the control surfaces. This means that the lift of the wing must compensate for the downwards force from the control surfaces, in order to maintain the load factor and lift of the turn. This means that the wing area must be large, resulting in a lot of drag.

The pilot control the control surfaces via the control stick to turn the aircraft. A statically stable basic aircraft can be flown using only a mechanical control system as the aircraft’s stabilising flight characteristics are inherent to its aerodynamic design.

The disadvantage of a statically stable aircraft is that it requires a large wing area to compensate for the downwards force on the control surfaces, which means a lot of drag and large energy loss when turning and therefore a large reduction in turn performance. The landing speed is also higher as the control surfaces force counters the lift of the wing. Moreover, a statically stable aircraft becomes even more stable when flying at supersonic speeds, meaning the control surfaces must be controlled to greater amplitude in the opposite direction. Because dynamic pressure affects the control surfaces control surface forces, so powerful control servos must be installed, increasing the overall weight.

To summarise, conventional statically stable aircraft most often use mechanical basic control systems with a large number of non-linearities such as friction, hysteresis and dead zones, which impair the control characteristics.

A dead zone is an interval in a signal domain in which no action takes place. The output signal of a signal sent via a non-linearity as a “dead zone” depends on the magnitude of the signal. A small signal through a “dead zone” does not issue a signal, whereas a large signal goes through reduced by the size of the dead zone.

Hysteresis is the time-based dependence in a system’s output on recent and earlier input.

Modern statically unstable aircraft

A modern statically unstable aircraft lacks inherent stability and so requires continuous artificial stabilisation. The wing area is smaller, and therefore experiences less drag.

In a modern statically unstable aircraft, the lift of the wing acts forward of the aircraft’s centre of gravity; a statically unstable aircraft has no natural restoring aerodynamic pitching moment, i.e. no inherent stability. The lift of the wing must be continuously parried by the flight control system. The forces on the control surfaces acts in the same direction as the lift of the wing to create a parrying counter-moment. These forces are combined into the total lift acting on the aircraft, which means that the wing of a modern statically unstable aircraft can be made much smaller which provides less drag. This enables the energy to be better preserved.

At supersonic speeds, the lift of the wing moves even further back to 40% of the chord (the chord is the straight line from the leading to trailing edge of the wing). This means that modern statically unstable aircraft become statically stable at supersonic speeds.

A statically unstable basic aircraft needs continuous stabilisation with the help of an active flight control system with full authority.

However, at supersonic speeds there is less control surface movement compared to a conventional statically stable aircraft. This means that modern statically unstable aircraft do not need the same powerful and heavy control servos.

The aircraft cuts through the air. Landing speed is reduced as all forces acting on the aircraft combine to lift the aircraft while also slowing it down and reducing its speed.

Subsonic properties

Additionally, a statically unstable aircraft flying subsonic is less statically stable at supersonic speeds compared to an old conventional statically stable aircraft. This entails lower control servo forces at supersonic speeds and thereby reduced control servo weights, as they do not need to be as powerful. This also means less weight to carry when flying at subsonic speeds.

Modern statically unstable aircraft most often have digital electrical flight control systems with full authority which eliminate the weight and non-linearities of the mechanical control system.

The disadvantage is that the control system must continuously issue its stabilising commands with the shortest possible time delay and at a frequency of at least 60 Hz.

If amplification is too low on the control system’s stabilisation, the stabilisation will be insufficient; if, on the other hand, amplification is too high, it can make the aircraft dynamically unstable at a higher frequency and, moreover, even result in aeroelastic oscillations (flutter).

Comparison between the Gripen and the JA 37 Viggen

The figure below illustrates the difference in wing area and placement between the JAS 39 Gripen, a modern statically unstable basic aircraft (shown in grey) and the JA 37 Viggen, a conventional statically stable aircraft (shown in blue).

Publication Standards

This section describes the very extensive and important work with standardisation for international civil and military aircraft systems. Saab's representatives in this work have had a very active and strategically driving role.

Through Saab's and the FMV’s active participation in the development of international specifications in the field of aviation, the capabilities of the industry and the armed forces have been strengthened for collaboration in multinational development projects and peacekeeping missions.

Streamlining the development of standards produces many and very substantial gains in efficiency for the companies that develop and sell products for civil and military aviation. For the customers and operators that will use these products, it is even more important to have standardised maintenance documentation in the form of handbooks and specifications.

This not only results in more rational maintenance, it also minimises the risk for misinterpretation or taking incorrect actions due to maintenance documentation varying between manufacturers. Standardisation in Integrated Logistics Support affects all development in the production of new products by suppliers, as well as all operative utilisation of the products by customers and operators. The work with standardisation that is described in this document has gained major economic significance, and not the least, major significance for aviation safety.

Saab's role in development of standards for Integrated Logistic Support

Through Saab and the FMV, Sweden has joined primarily with the European defence industry in developing a nearly complete tool for product support information in the form of a series of ILS specifications.

There were several standards for Logistics Support Analysis and associated data when the Gripen project was started. Unfortunately, they were more or less obsolete at this time, primarily with regards to data formats.

With the support of the FMV, Saab has been a driving and unifying force in producing data models. This has given Saab in-depth knowledge of Logistics Support Analysis and associated data, which has resulted in sales of training packages to a number of countries.

Saab also has good reason for participating in and driving development of a cohesive series of international maintenance specifications in the future as well.

The Aerospace and Defence Industries Association of Europe (ASD) took the initiative to develop a complete set of handbooks and specifications. These concern continuous analysis, optimisation and delivery of maintenance information. Through this initiative, the prerequisites are now in place for cost-effective operation and maintenance of complex civil and military products.

Although a certain amount of work remains with the details before the collection is complete, this work is of a relatively limited scope.

A journey of change for product support information

The journey of change began as the Eurofighter, Rafale and the Gripen projects took form on the drawing boards and when documentation on paper was the primary delivery medium.

It started at the beginning of the 1980s with the creation of the first joint military publication standard in Europe. This standard is now designated S1000D. Now at the mid-2010s, there is a complete set of handbooks and specifications for the production, delivery and use of product support information for the first time ever.

While these handbooks and specifications were under development, many stakeholders – both in the civil and military sectors, and from different parts of the world – joined the development and user groups. A few examples of participating nations include the US, Canada, Singapore, Russia and China.

Product support information

Product support information for aircraft is commonly associated with large quantities of handbooks. These contain descriptions and instruction prepared for technicians and pilots. There are pilot handbooks, maintenance regulations and spare parts catalogues, all delivered in printed form. This has been the case since the infancy of aviation with the difference being that the number of pages has exponentially increased. This has resulted in the need for substantial personnel resources for writing, reviewing, printing and distributing this information.

There were many rules governing the content and configuration of these types of handbooks. Each manufacturer of civilian or military aircraft, or combination of manufacturer-customer, had its own rules in one or usually several variants.

For civilian aircraft however, manufacturers and customers had already agreed to a certain standardisation of these handbooks through the organisation Air Transport Association of America (ATA).

Technical Publications

At the beginning of the 1980s, product support information was in principle synonymous with technical publications, and to a certain degree, the same also applied to drawing materials for repair work.

The changes therefore began with technical publications, when requirements were set for digital production and delivery of these publications.

When the FMV ordered the JAS 39 Gripen (henceforth referred to as the Gripen) in 1982, the contract stipulated that the technical publications were to be produced in a digital system.

Delivery to the FMV was thereafter to be in a digital format. In the FMV’s original requirement specifications for the Gripen, an exact supplier-dependent delivery format was stipulated.

Saab instead chose to tender another arrangement. Saab offered the FMV production of technical publications with modern word processing technology. This entailed that the text could be stored and edited on magnetic media. The reason for this was to avoid locking into the existing technology and standards of the time. The decision proved to be advantageous for both the FMV and Saab, as well as other IG JAS parties.

At the beginning of the 1980s, the military publication department at Saab consisted of an editorial staff with a typesetting group and a layout group, as well as writer groups for directives, descriptions and spare parts catalogues. Saab naturally had excellent illustrators as well, who were highly skilled in the use of conventional drafting pens. Nearly all work at this time was conducted manually with a number of transfers between the production groups.

Rationalisation initiatives were first taken in typesetting for the 37 Viggen aircraft. This was both because there was available technology in the field, and because the typesetting group was already familiar with computerised support in photosetting. Because publication production for the Gripen would not begin until 1985–86, efforts were primarily focused on internal, general rationalisation of the publication organisation.

1980s – Industry and FMV look to the future

Saab created a workgroup in 1983 to conduct a needs analysis and provide suggestions for procurement of computerised publication systems, both for the military and civil publication departments.

The FMV created a workgroup in 1985 for technical information systems with participants from the FMV, Telub and Saab. The workgroup was tasked with studying and proposing new methods and techniques for future information provision within the Swedish Armed Forces. Work was initially oriented to defining the FMV’s requirements for the delivery of digital information for the Gripen.

Both workgroups followed international developments and drew up new ideas and models.

A new standard, Standardized Generalized Markup Language (SGML), had begun to take form during the 1980s for sustainable storage of technical documentation. A number of new image standards were also introduced.

In 1985, the US Department of Defense introduced a framework called Computer Aided Logistics Support (CALS) for future information management and standardisation of product support data. The results of this work with CALS presently constitutes the basis of the new work methods and standards in international use.

Steps towards digital publications

At the beginning of 1986, Saab procured the first components of a digitalised production system. A number of graphics workstations were procured, first for typesetting, but there was also a workstation with a colour monitor in the illustration group's office. The Unix-based software Interleaf TPS was used for text and layout, and AutoTrol Tech Illustrator for producing illustrations.

Although elimination of the writers’ pens and paper was in the official plans, it was not included in the first step of renewal for the production apparatus for technical publications. It was first necessary to establish competence in the new way of working, and setting up templates and routines. With the Unix-based software, pages with final layout could be directly produced on the graphics monitors. Originals were printed on a laser printer in A4/A3 formats. Deliveries at this time were still as hard copy publications.

First agreement for digital publications

The FMV updated the publication agreement for the Gripen in 1989. The new delivery agreement would now encompass the following requirements:

  • The production system would utilise digital production technology.
  • Text and images would be digitalised at the source.
  • Layout would be performed in a computerised graphical system.

Delivering the documentation in a digital format (SGML) was yet not requested. It was still paper that applied. Most important was having the information stored in a digital format while awaiting more stable standards both for storage and distribution.

Paradigm shift for writers

The typesetters were initially responsible for entering all text from the writers’ handwritten documents. During the years 1992–94 however, the writers gradually began entering their own texts and the figures digitally produced by the illustrators. The writers who prepared descriptions began first. Just as now, they were fulltime writers, and in most cases, well-motivated to adopt the new technology. Digital workplaces were gradually introduced for the writers who wrote regulations, even if there was a certain amount of resistance.

Air Force's system for technical publications

The Swedish Air Force needed a new system for administration and internal production of technical publications, above all for technical orders. A project was begun in 1990 to develop a system for digital maintenance publications.

There were stringent requirements for the delivery of administrative planning and production data from the documentation providers. More than 80 pieces of administrative data were to be handled digitally, along with each document and its drawings. The documents were to also be coded in SGML and follow a structure that was set in a Document Type Definition (DTD). This is a specification that stipulates the structure in the digital format for a document. With this, independency was obtained between the digitally stored information and how the document would later be presented.

The FMV's new systems entailed that upon delivery of documents, Saab was to send a data file with administrative information along with each document. The document was a text file with the structured information and a data file for each image that was included in the document. The administrative date and the text file were to be SGML coded and the images were to follow one of the specified image standards.

Adaptation of Saab's publication system

In 1993, the FMV ordered an adaption of Saab's publication system for digital production and delivery in SGML. This entailed that Saab’s Interleaf system was complemented with SGML functionality.

With the order of SGML-coded documents for the Gripen, an extensive conversion programme was begun. Thousands of documents were converted in the subsequent years. The Gripen spare parts catalogue was also to be delivered in accordance with the new requirements.

The first catalogue produced with this system was for the 35 Draken aircraft, which was delivered to Austria in a digitally standardised format in 1997.

New publication standard for Swedish needs

With the implementation of the Gripen system, a new system and function categorisation of the materiel system was introduced. The international categorisation in use at the time was based on ATA100, a publication specification for civilian aircraft systems. IG JAS and the FMV did not feel that this standard was appropriate for a modern fighter aircraft.

A new materiel group categorisation was instead produced that not only encompassed the aircraft, but also the support system. The structure for materiel group categorisation came to include both materiel and functions. In the agreement between the FMV and the industrial group IG JAS, a collaborative project was included for producing regulations for Gripen publications.

These regulations were designated PUB94, with 94 standing for materiel group 94. Under the international collaborative initiative, the European Association of Aerospace Industries (AECMA), later ASD, a project was begun with developing a common international publication specification for military aircraft.

This publication specification was designated AECMA Spec 1000D. Because the need for a new publication specification for the Gripen was needed sooner, AECMA Spec 1000D could not be used.

Specification for technical publications

In 1985, a workgroup at AECMA invited the European defence organisations to join in initiating work to harmonise the then-current national publication specifications. The goal was to develop a European specification to reduce costs in multinational programmes. The working name for the specification was AECMA Spec 1000D.

The goal for work with AECMA Spec 1000D was to comply with the following points:

  • Be applicable for all new aircraft and equipment projects
  • Be based on a common database, a Common Source Database (CSDB)
  • Administer information in uniquely identified modules – data modules
  • Have an information structure linked to the function/materiel structure – data module code
  • Enable automatic compilation of publications (information sets) from the CSDB
  • Handle both paper and digital presentations

Participating in the project were industrial and military representatives from, for example, France, Great Britain, Italy, Germany, Spain, the Netherlands and Sweden. Prime supporters of the project were the four nations that were collaborating on the Eurofighter.

The driving force stemmed from work conducted when the Eurofighter and Rafale programmes were being developed during the subsequent years. Spec 1000D consequently became the first truly international, recognised and applied specification for military aircraft publications.

During 2000, an initiative was taken by NATO in the form of a workgroup called Interactive Tech Data Working. This workgroup presented a roadmap for how Europe and the US could further develop Spec 1000D in a new common issue. Work included specific requirements from a number of American MIL specifications and handbooks.

The Aerospace Industries Association of America (AIA) joined the European workgroup in 2003 to further develop the specification. The US Department of Defense consequently also initiated participation through its workgroup US Tri Service. The name AECMA Spec 1000D was changed the same year to S1000D.

A few years later in 2005, the Air Transport Association of America (ATA) joined as a third party, which in principle meant that the entire aircraft industry had embraced S1000D. The first civilian aircraft to use S1000D was the Boeing 787, later followed by the Airbus 350.

During the past ten years, Russia, China, Australia and Singapore, for example, have begun using S1000D. S1000D has now become the absolute dominating standard for maintenance information for aircraft and technical information for in principle, all military materiel projects, when beginning with Issue 2 of the specification, ground and marine systems were also included. Besides English, the S1000D standard is now available in Russian and Chinese.

Publication deliveries for export

When the first export contract was signed for the Gripen, it included the requirements for publication deliveries according to AECMA's publication specification S1000D. Because the first export countries for the Gripen, the Czech Republic and Hungary, had requirements for an English-language publication package, the Swedish Air Force decided to gradually shift to English for publications.

CALS, the framework introduced by the US Department of Defense in the mid-1990s, was developed into a concrete programme for producing a unified series of internationally acceptable standards. The initiative for this programme was taken by a number of industrial leaders, including Lockheed-Martin, BAE Systems, Fujitsu, MITI, Alenia and Dassault, as well as a number of representatives from Sweden (Saab), Korea, Japan, the UK and NATO.

Workgroups were formed to produce proposals for standards and working procedures that would support interoperability, which in turn would lead to higher reliability and lower costs and lead times.

This resulted in eleven recommendations, of which four were strategic. Based on the prioritised recommendations, two areas became the foundation for extensive work with international standardisation in product support information. This encompassed the following:

Part 1 Product Life Cycle Support (PLCS), which included:

  • Integrated Information Model.
  • Integrated product data, including support for logistics.
  • Support for the product lifecycle.

Part 2 International publication standard including database and Interactive Electronic Publications, which included:

  • A single suite of integrated technical documentation standards.
  • Common source database.

PLCS consortium

To further work with product support information a consortium called PLCS Inc was formed in 1999 by a multinational group of industries and government agencies. Saab was a co-owner and had a representative on the board.

The consortium’s mission was to develop an international standard encompassing the entire scale of data for dimensioning, executing and following up operation and maintenance during a product’s life cycle. The resulting standard was consequently named the Product Life Cycle Support Standard (PLCS).

The goal of the PLCS initiative was to fulfil three significant business requirements for product owners and operators of complex products and systems, such as aircraft, ships and power plants. These three requirements were:

  • Reducing the total life cycle cost.
  • Protecting investments in product data throughout the life cycle of the product/system.
  • Increasing use of the product/system for improved profitability.

PLCS was intended to obtain future operational and maintenance systems that were easier to integrate and have a well-defined neutral interface.

The PLCS initiative resulted in an application protocol (AP239), which became a part of the ISO standard for representation and exchange of product information, the Standard for the Exchange of Product Model Data (STEP) (ISO10303). This data exchange concerned exchange within and between manufacturers, and between manufacturers and owners/operators. This would be conducted by streamlining the implementation of integrated and interoperable solutions for Integrated Logistic Support (ILS).

The FMV decided in January 2006 to focus on management of product data for new materiel projects in accordance with the PLCS principles.

 

Specifications for product support information

A workgroup within the ASD organisation was formed in 2002 to among other things, assess the need for common specifications for product support information.

At the beginning if the 2000s, there were three specifications for product support information within ASD:

  • ASD - STE100 – Simplified Technical English, a guide that was well-established and a requirement for maintenance publications for civilian aircraft.
  • S2000M – Materiel Management, as standard for exchange of data packages and used in NATO joint projects (e.g. Eurofighter). S2000M.org
  • S1000D – Technical Publications, a well-established publication standard in European military projects, while the aviation industry and armed forces in the US had just begun using this standard. S1000D.org

A survey was conducted in the European aviation industry to determine the areas in which, current and applicable standards/specifications for product support/maintenance information were lacking. The results showed that a number of components were lacking as set out below:

  • A procedure handbook for the development of scheduled maintenance programmes for military aircraft
  • An application handbook for Logistics Support Analysis

With these components, including the three specifications mentioned above, and PLCS as the technical platform, it was determined that the basic need for standards would be satisfied.

While work was underway, it was discovered that supplements were necessary to obtain a series of ILS specifications that for all practical purposes, would be complete. These supplements were the two additional specifications – International Guide for the Use of the S-Series of Integrated Logistics Support, and International Specification for In-Service Data Feedback”.

Developing and continuously improving preventive maintenance – S4000P

When Airbus was to develop the A400M aircraft, there was a need for a more modern method than what was currently in use, a military standard called MIL-STD-1843 (RCM) – Reliability Centred Maintenance for Military Aviation. Work was therefore begun in 2005 to produce a handbook for this purpose. It was defined as a procedure handbook for the development of scheduled maintenance programmes for military aircraft, called S4000M.

S4000M was based on the civilian counterpart to RCM, designated Maintenance Steering Group 3 (MSG 3), which was supplemented with user experiences from military applications. Processes were optimised and consideration was taken to a number of important factors, such as new materials and ecological and legal aspects.

After diverse legal complications regarding IPR rights, the handbook was published with the designation S4000P, International Specification for Developing and Continuously Improving Preventive Maintenance. An in-service maintenance organisation was now included, which meant that the analysis now encompassed the entire product life cycle.

Issue 1 of S4000P was published in mid-2014 and can be downloaded free of charge from www.S4000P.org

Logistics Support Analysis – LSA - S3000L

Upon implementation of complex technical products, well-adapted support systems must be available. This requires an extensive analysis process to ensure that consideration is taken to maintenance aspects as early as the design stage, and to build up a cost-effective support system. Such processes include several different types of analyses of a large amount of technical and logistic questions. Moreover, meticulous documentation is required of the configuration-steered analysis results. Early consideration to the technical maintenance solutions is becoming increasingly important for minimising future operational and maintenance costs.

On the initiative of Saab and EADS, a workgroup was formed in 2006 to review a large number of standards. It was determined that there was a substantial need for a handbook for Logistics Support Analysis that was adapted to present processes. The handbook (Issue 1.1 of S3000L) was completed and published at the end of 2014 and can be downloaded free of charge at www.S3000L.org

The LSA handbook encompasses among other things:

  • Rules for structuring of a product system categorisation.
  • Rules for selection of the LSA candidates that are to be analysed in detail.
  • Described types and method for conducting the various analyses.
  • The connections with customers during the analysis processes.
  • The connections between the LSA process and the support engineering process (e.g. reliability, ease of maintenance and testability).
  • A complete data model based on PLCS with both LSA as well as LSA data (LSAR).

In-service data feedback - S5000F

To be able to continuously maintain function and operational reliability at an optimal cost, it is necessary with feedback of functional and operational data to the technical processes and the ILS processes.

S5000F, a standard oriented to processes for feedback of information for operations and maintenance, is under development.

The goal is for the specification to be applicable either independently or together with one or more ILS specifications, so that in a structured manner, feedback of operational and maintenance data can be conducted between various stakeholders. These can be users, manufacturers, service companies, etc. There must be the capability for bidirectional feedback, such as from users to manufacturers and vice versa.

Training analysis and design - S6000T

A multitude of analyses are performed with regard to spare parts, LSA, feedback of operational data and so forth, as well as for attaining cost-effective training for use and maintenance of a product. A new standard is under development that will replace the older specifications for training analysis, Training Need Analysis, and it will be adapted for connection to other ILS specifications with regard to data. A first draft is expected to be available at www.S6000T.org in mid-2016.

The author´s reflections