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From an original article published in August 2001

"Hey Pierre, see that crazy spotter over there?"Nomadic warriors

Gary Parsons was at RAF Waddington for Exercise NOMAD, held over 12-30 July 2004.

A variety of different nations once again descended on Waddington in July for the annual Exercise 'NOMAD', the largest Dissimilar Air Combat Training (DACT) exercise in Europe, centred on BAE Systems' North Sea ACMI Range.

What is ACMI?

The North Sea ACMI Range (NSAR) is centred some eighty miles off England's east coast in dedicated air combat training airspace. It has been cleared for use by a wide range of NATO and European fighters and uses the latest technology to provide a very high degree of accuracy in the measurement of user aircraft position and flight conditions, together with simulation of missile firings and the outcome of tactical engagements. Known by its 'Showground' callsign or simply as the 'ACMI', the main control centre and debriefing facilities are at RAF Waddington in Lincolnshire.

The North Sea ACMI facility is based upon an American system, BAE Systems (then British Aerospace) having bought it from Cubic Worldwide Technical Services (CWS) under a Foreign Military Sales licence in 1988. Constructed during 1988/89 as a private venture that cost approximately 60million, the original concept of the NOMAD patchrange was to fill a gap in air combat training that had been identified by the company within the European theatre. BAE SYSTEMS' concept was to make the NSAR financially profitable by selling thirty-minute range 'slots' to any airforce that might want to use the facility to conduct air-combat. Previous customers include UK MoD (RAF, RN, QinetiQ), Netherlands, USAFE, France, Belgium, Switzerland, Austria, Spain, Denmark and Norway.

Home on the range
Swiss F-18Cs
Spanish EF-18A
Swiss F-18C
Mirage 2000C
FRA Falcon
Mirage 2000C
Spanish EF-18A
Mirage 2000C
Swiss F-18C

All of the equipment necessary to use the range and the range itself are maintained and managed by BAE SYSTEMS, thus eliminating many of the overheads to the end user. CWS continue to be involved in support as a sub-contractor, in true partnership fashion. The system is cleared for all NATO forces, including one or two non-NATO (such as the Swiss). If a new customer comes along, MoD approval is needed before it can set foot at RAF Waddington, but BAE Systems has had little problem so far and in general has excellent relations with both the MoD and hosting RAF.

BAE Systems operate a 'Turnkey' contracting system, i.e. it provides support and administration, the customer simply brings his aircraft and flies his allotted slots. Success is guaranteed - if a slot can't be flown due to weather, the customer doesn't pay. Charging is by the thirty-minute range slot - as long as the user is satisfied, he pays. If he isn't satisfied that BAE Systems fulfilled all the criteria for a successful mission, again he isn't obliged to pay. It is rare that the Service Provider goes to this length in ensuring customer satisfaction, but its success can be measured by the very frequent return visits of the Belgians, French and Swiss Air Forces.

Only one customer at a time pays for the range slot - he may invite other forces to join in the fun, or simply undertake one-on-one or two-on-two sorties from within his own unit. Spread over the year, the training is shared out fairly evenly over the air forces seen at Waddington and the other Display and Debrief Sub-Systems (DDS) bases.

The Hardware

Much of the range equipment is located in the North Sea range complex located well off shore from the UK mainland in danger areas known as EG D316 and EG D317. The hub of the range is six oil rig-like tower structures anchored to the seabed known as ‘Tracking Instrumentation Sub-system Towers’, (TIS). These are arranged in a circle of thirty nautical miles diameter, with five TIS towers around the circumference and a single TIS master tower in the centre of the circle. Its remote location allows aircrew to practise unhindered by the normal environmental and airspace restrictions found elsewhere. This allows missions to be flown at almost all levels and speeds, including supersonic, plus of course active and passive countermeasures can be employed for more realistic training scenarios.

Each aircraft carries an AIS data pod, usually on the wing. The AIS pods contain sophisticated electronics and when airborne and within range of the TIS towers the pod is electronically 'interrogated' by equipment on each of the towers. Signals and telemetry data from the AIS pod is in turn 'echoed' back to the TIS towers and they then send this data to the central master tower. The master tower then sends the digital information via a cable buried underneath the sea bed to an on-shore master computer system, known as the Control and Computation Sub-system, (CCS), where the information is processed.

The AIS pod (P4A-M) is two-thirds the weight of an AIM-9 Sidewinder, although physically a bit bigger. A single pod is mounted on the aircraft wing tip launch rail or under wing pylon with power and data connections to the host aircraft via a standard NATO Sidewinder umbilical cord. The CofG and flutter characteristics are virtually identical to that of the real missile. As the French Air Force doesn't operate Sidewinder, an agreement with Matra was made whereby BAE Systems converted a NECA tube (basically a Magique missile) with the innards from a standard AIS pod. This enables all Mirage equipped units, and indeed air forces, to utilise the ACMI downlinking facility.

ACMI 'spike'Each pod has a unique digital code number allowing aircraft on the range to be individually identified. The pods have a 'spike' like pitot-static head at the front and internally a radar altimeter and air data sensor. These provide airspeed, altitude, yaw, pitch and roll information via a built in transponder to the TIS Towers every 20 milliseconds. The AIS pod is in turn 'interrogated' by electronics on the TIS towers every 100 milliseconds and through comparison of the data between the towers an accurate fix is achieved on the aircraft to within 4.5m (15ft).

Other data relayed via the AIS includes angle of attack, G, and radar antennae train angle (ATA), or seeker head look angle. It also provides Radar Warning Receiver (RWR) information and data on weapons selection and firing signals which are subsequently interpreted by the CCS computer to enable it to generate a simulated weapons release and performance at the time of firing. All this data can be replayed later via the DDS consoles to provide an accurate and detailed picture of each combatant aircraft's performance.

The AIS pods allow each aircraft to be tracked three-dimensionally as well as providing data on airspeed, altitude and many other factors. If an aircraft elects to simulate firing a weapon this data is also transmitted back from the pod with the CCS computer electronically 'firing' and simulating the weapons parameters and eventual outcome from data programmed in its memory. The CCS can handle up to fifty simultaneous missile trajectories. Data to and from each aircraft's wing-mounted AIS pod is received by the five outer TIS towers encircling the range and forwarded to the central TIS master tower via fibre optic cables. From the master tower there is a further dedicated fibre optic cable buried under the sea bed that relays this data via BT's commercial 'Megastream' network to the CCS located on shore at RAF Coningsby in Lincolnshire, UK.

Hornet HavenAs the fight is in progress the CCS can relay data in 'real time' to debriefing consoles being referred to as Display and Debrief Sub-Systems (DDS). The DDS consoles are the user interface and allow real time observation and later replay of the mission. The DDS units also allow active intervention of the fight for safety reasons or intentionally by GCI controllers by transmitting back through the system via a UHF link on the central TIS master tower. It also allows real time 'kills' to be called on 'splashed' targets thus making the whole fight more realistic and precise. Primary DDS facilities are located in the UK at RAF Waddington, RAF Coningsby, RAF Lakenheath and in the Netherlands at Leeuwarden AB. Leeuwarden's DDS also supplies data to two other Dutch Air Force bases at Volkel and Twenthe who have DDS(R)s - Display and Debrief Sub-system Remotes. These are only capable of providing debriefing information and do not allow for active intervention in missions by controllers. These DDS(R)s can however be transported to other locations unlike the fixed DDS systems.

Upon recovery to one of the DDS locations, aircrew can then replay the whole fight. Data recorded from the AIS pods on each aircraft allows a detailed analysis to be made of each intercept, manoeuvre and 'kill'. Aircraft can be shown on the consoles from various perspectives and with all flight parameters such as altitude, speed, G and so on. Via large flicker free screens, the fight can be watched in all the same detail as noted above and in addition it can be viewed in slow motion, freeze-framed or fast forwarded like any video recorder. Hard copy print cuts are also available for later study as well.

Mirage 2000BThe crucial weapons release and the success or failure of hitting the target are also shown and all of this data combines to provide an ability to learn more effectively from each sortie. The DDS allows for monitoring or controlling of missions taking part in the range in 'real time' by a range officer who is in contact with each aircraft. With the pre-programmed aircraft parameters of each aircraft type the range officer is warned of any impending loss of flight control immediately so that he can intervene should the 'fight' become unsafe. A 3-D interactive display is the main system control element which personnel can use to view the fight.

Various scale magnifications can be used to zoom-out to the 'big-picture' or zoom-in to see aircraft at much closer detail. Console operators are also able to see the range from any angle - 360 degrees in azimuth or 0 degrees (from sea level) to 90 degrees ('God's eye' view). In addition they are also able to select a cockpit view as seen by any of the participating aircraft which shows every detail including HUD display, horizon, sun position and even cockpit framing! In the big picture individual aircraft types are recognisable by their shape and their path of flight is shown by lines which emanate from the wing tips in a trail fashion. Missile shot and 'kills' are also clearly shown.

The debriefing room at Waddington. Picture courtesy of BAE SystemsThe beauty of the system is that the DDS's are all linked via a secure encrypted data link which means a single mission can be debriefed at different locations. For example if a Swiss air force mission is briefed to work with the Netherlands Airforce, the Dutch pilots do not have to land at RAF Waddington to debrief. They can recover to a DDS location such as Leeuwarden, Volkel or Twenthe in Holland and discuss and see the same debriefing picture as the Swiss crews sat at the DDS at RAF Waddington.

Missile simulation within the CCS software is based upon a generic system, built up over time by BAE Systems using information within the public domain, particularly important in overcoming American security regulations. One of BAE Systems' simulations is called BLAST - 'BAE Systems Long-range Active Simulation for Training' - which is an AMRAAM look-alike. Using a generic missile provides a simpler form of debrief, but it is a good baseline as a 'kill' with a generic missile will probably have a lower confidence factor than one with a more sophisticated model, so if a hit is made the pilot can be fairly assured that his tactics are sound for a whole range of similar missile types. The intention of the range is to make the pilot situationally aware, not explore the outer envelope of a particular type of missile. Guns can also be simulated, but is not often utilised.

A future for Nomad?

It was evident that Exercise NOMAD was smaller than in previous years, with many players flying from their home bases, leading to rumours of its impending demise. One hopes that the respective air forces continue to see the benefit of co-located training rather than operate independently, as there is no substitute for 'chewing the fat' with your fellow combatants in both the debriefing room and the bar afterwards.


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