Shanwick Oceanic Control
Prior to 1966, the United Kingdom and Ireland both provided ATC and Communications services in the same area of the North Atlantic. The air/ground communication station at Ballygirreen, near Shannon, worked to the ATC centre at Shannon and the communication station at Birdlip, Gloucestershire worked to the ATC centre at Prestwick, Ayrshire, Scotland. This caused duplication of work and an agreement was reached between the UK and Irish governments where Prestwick and Ballygirreen would work as one unit. Prestwick assumed the ATC (Air Traffic Control) function and Ballygirreen assumed responsibility for communications. Hence the name Shanwick originated, SHANnon and PrestWICK being the original ATC providers.
Responsibility for the provision of air traffic services within International Airspace is delegated to UN Member States by the International Civil Aviation Organisation (ICAO). ICAO divides such airspace into Flight Information Regions, parts of which may be deemed Controlled airspace and, where appropriate, classified as an Oceanic Control Area (OCA).
The flight control (Procedural ATC) aspect within the Shanwick OCA is the responsibility of the United Kingdom and is provided by NATS from the Prestwick Centre and the voice communication aspect is shared between the CDO's (Clearance Delivery Officers) based at Prestwick Centre and the Irish Aviation Authority (IAA) from Shannon Aeradio, based in Ballygirreen Radio Station.
Shannon Aeradio maintains radio contact with flights within the Shanwick OCA by means of HF radio. HF can provide global coverage due to its ability to reflect (see refraction) off the ionosphere and can span the globe in a series of skips. VHF coverage however is normally limited to line-of-sight range. Shannon Aeradio, callsign "Shanwick Radio", utilises over 20 HF channels and 2 VHF channels. At peak times it can communicate with in excess of 1400 aircraft during a 24-hour period. (Using the callsign "Shanwick Oceanic", the Prestwick Centre has 2 dedicated VHF frequencies specifically for the issue of Oceanic Clearances to westbound flights about to enter the Shanwick OCA, and also provides an ACARS based system called ORCA – Oceanic Route Clearance Authorisation – for suitably equipped aircraft to obtain such clearances without the need for voice communications).
During October 2009, NATS transferred its Oceanic ATC operations from the former Prestwick Oceanic Area Control Center (OACC) into the £300m Prestwick Centre. The Prestwick OACC had been located within the Scottish & Oceanic Area Control Centre, (ScOACC), at NATS' Atlantic House facility, adjacent to the Prestwick Centre. The Prestwick Centre is also home to the Scottish Area Control Centre, (including, since January 2010, the former Manchester Area Control Centre), and the Scottish Air Traffic Control Centre (Military).
Oceanic ATC operations at the Prestwick Centre are undertaken using the joint NATS/NAV CANADA designed ATC computer system known as SAATS – Shanwick Automated Air Traffic System. SAATS, developed from NAV CANADA's GAATS – Gander Automated Air Traffic System – has been in service with NATS since November 2006. (Located close to Gander International Airport, Newfoundland, Canada, is the NAV CANADA Gander ATC center which is responsible for flights in the northwest part of the North Atlantic.)
During 2005/06, upgrades to Shannon Aeradio equipment at Ballygirreen took place and the IAA entered into an agreement with the Flugstoðir (ISAVIA) subsidiary Gannet ATS Communications to provide additional HF communication services within the Shanwick OCA via the Gufunes Telecommunications Centre, (in Reykjavík, Iceland).
Transatlantic traffic has been steadily growing over the years, and prior to the global economic downturn of 2008/09 this growth was expected to continue. In 2006, 391,273 aircraft crossing the North Atlantic, on both random routes and North Atlantic Tracks, communicated with air traffic controllers at Prestwick via Shannon Aeradio; an increase of 5.4% from 2005. (On 21 July 2010 a daily record of 1432 movements was set, breaking the previous daily record of 1415 movements recorded on 26 July 2008). However, despite increasing numbers of aircraft operators utilising technological developments including Datalink communications, Future Air Navigation Systems and forwarding waypoint position reports via Automatic Dependent Surveillance (ADS-C & ADS-B), or Flight Management Computer, aircraft continue to be required to carry HF radio as a primary means of communication within oceanic airspace.