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North Sea helicopters first to be tracked by multilateration

Surveillance of oil support helicopter operations using multilateration has been launched over the North Sea. Multilateration is not new, but this is the first use of such a surveillance system in a wide-area offshore environment.

Deployed by UK air navigation service provider NATS and Oil & Gas UK, the surveillance system is to be operated at the NATS operations room in the tower at Aberdeen airport, from where all oil-support helicopter flights originate.

At present control is purely prodedural beyond the range of Aberdeen's radar, which means there is no surveillance in the area where most rigs are situated.

The multilateration hardware consists of signal transmitter and receiver stations fitted to 16 offshore oil and gas platforms in the central North Sea. These will identify and track helicopters in real time, and the activity will show on radar-like displays at Aberdeen.

Land-based radar cannot detect helicopters further than about 150km (80nm) offshore because they operate at low level, below the radar horizon.

Because the multilateration system's transmitter and receiver stations are on the oil rigs, they can obtain line-of-sight responses from the helicopters' transponders at enough individual stations to fix the aircraft.

An added advantage is that the multilateration system - provided by US specialist Sensis - is less costly and more accurate than radar, with a faster update rate.

Controllers at Aberdeen will be able to monitor the helicopters all the way to the helidecks. This, says NATS general manager at Aberdeen John Mayhew, will improve the controllers' ability to provide accurate traffic information, and will enable a quicker and more accurate response in an emergency.

NATS started work on the project in 2004. Eventually transmitter and receiver stations will be operational on a total of 16 offshore platforms in four geographic clusters.

At present only three clusters of four stations each have been set up, but the system will begin operation for flight trials "later this month", says NATS. The fourth cluster, on the southernmost group of rigs, will be ready by January, and the whole system will become fully operational by June 2010, providing surveillance over more than 50,000km² (19,300 miles2) of the North Sea where, previously, there had only been procedural control.

Source: Flight International