World’s first WAM celebrates tenth birthday

The Wide Area Multilateration (WAM) system developed by ERA at Ostrava Mosnov Airport has reached its tenth anniversary and is now moving into a second decade of flawless operations.

It has functioned non-stop without any critical errors occurring for 87,600 hours.

The WAM system deployed around Ostrava airport in 2003 was the first WAM in the world to be operationally certified and fully integrated into the Air Traffic Control (ATC) structure.

Along with the WAMs in Prague and Brno (2006 and 2009 respectively) the three systems provide nationwide coverage of Czech Republic’s airspace.

Over the following years ERA has installed over 20 other WAM systems in various countries worldwide including the United Kingdom, Spain, China, New Zealand and South Africa including the world’s largest WAM in Namibia which conducts flight tracking and surveillance for the entire country.

These operational WAM systems have been working 409,552 hours in all. All the systems deployed by ERA meet EUROCAE ED 142 and ICAO ANEX 10 standards.

Ostrava Mosnov, the country’s third-busiest airport, is located in mountainous terrain in the north-east sector of the Prague Flight Information region (FIR). The Air Navigation Services (ANS) of the Czech Republic contracted the ERA Company’s MSS multilateration system as a substitute for the Secondary Surveillance Radar (SSR) in 2001.

The purpose of the system was to cover the Terminal Control Area Ostrava with respect to low altitudes and final approach areas and place a reliable cooperative sensor in this sector of the Prague FIR. The decision was based on a lengthy performance and cost/benefit analysis, which clearly determined that ERA’s wide area multilateration solution could outperform the traditional SSR at a fraction of the cost.

At present the system in Ostrava is not only a substitute for the radar, but has also introduced new features which are appreciated by the controllers. First and foremost, it is absolutely reliable. The MTBF (Mean Time Between Failure) of all the modules included in the Ostrava airport’s system is 574,128 hours

“ERA’s multilateration systems have a long track record of performance and reliability in both surface and en-route applications. The air navigation Services (ANS) of the Czech Republic have made extensive use of ERA’s capabilities since 1999 and we are currently preparing the extension of several stations for WAM Ostrava, so we can provide surveillance of the airspace further to the north. We need to “see deeper” into the neighbouring Poland region heading toward Katowice airport“, officially stated Ivan Uhlir, an expert from Czech ANS.

The ERA system was fully installed and approved by SAT at the end of 2002 and type certified in 2003 against ICAO ANNEX 10 for interrogation and against Eurocontrol radar standards for surveillance performance after one year of trouble-free operations. The system performed so well during that year that it was certified and can even be used for 3 Nautical Mile (NM) separations. It is believed to be the only operational multilateration system in the world with such certification to date.

The system at Ostrava airport also serves as a good example of usage of the Height Monitoring Unit solution for reducing vertical separation in the upper air and improving aircraft capability of maintaining an accurate height position. It has consequently kept up with the global implementation of the Reduced Vertical Separation Minima (RVSM) programme.

The WAM system in Ostrava consists of five receiving stations and two interrogators and provides ASTERIX data to the ATC systems both in Ostrava and in Prague along with the Remote Control and Monitoring Systems (RCMS) established in both centres. The coverage extends 80 NM from the Ostrava airport all the way down to the airport surface.

The system currently contributes to the overall ANS radar network and remains the only equipment to control separation between incoming and outgoing aircraft at Ostrava Mosnov airport. The system tracks aircraft down to the apron with an accuracy corresponding to the airport A-SMGCS sensor.

The Mosnov airport system based on central architecture was extended in 2009 by ground stations based on distributing architecture to provide surface surveillance of the airport and expand WAM coverage of the surrounding area.

“The bottom line is that ERA’s systems truly work and they work more economically than SSR. They also meet current ecological demands as they contain 70% software and only 30% hardware. This means less energy and easier maintenance,” said Uhlir.

Multisite surveillance, known as ‘multilateration’, has made a name for itself in ATC circles, which have appreciated the new features and benefits, in addition to the advantage of cost effectiveness. There was a long distance to travel, but the early scepticism among users has finally been replaced by enthusiasm. Fifteen years ago only a few people were aware of multilateration, but at present MLAT systems have been installed in airports all over the world and amount to a better alternative to traditional radars.

In order to demonstrate the capability of an aircraft to maintain an accurate height position, a height monitoring unit was needed with an accurate surveillance capability, a software process to establish the total vertical errors and an interface to a central database to correlate the information. As early as 1999, ERA was awarded a contract to deliver height measuring equipment to Eurocontrol which would be integrated into the Linz HMU, the first and probably the most utilized HMU in the Eurocontrol region.

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