By: Suad Čobo
Today’s radar technologies make it easier and faster for air traffic controllers to manage traffic flow, avoid collisions, and navigate flights in their airspace. However, as I have discussed in one of my last articles on radio propagation, a traditional radar has the same natural barrier, which means it cannot detect flights outside of their range. This is most prominent over the Atlantic and Pacific Oceans. How does air traffic control work over these areas of the world? In this article, we will be reviewing procedures over the Atlantic.
North Atlantic Tracks for the westbound crossing of February 24, 2017 [1]
Imagine road traffic. There is no official institution to track the movement of traffic on the road along a driver’s route. What do they use? They use their critical thinking, follow road signs, and maintain necessary separation with other traffic. They also move along an already defined path, highway, motorway, etc. It is similar to crossing the Atlantic without radar coverage, just with a lot of forward planning and thinking.
The airspace above the North Atlantic is divided between the Irish Aviation Authority (IAA) from the Republic of Ireland and the Nav Canada from Canada. It is divided as Shanwick Oceanic Control Airspace (OCA), from the maritime boundary of Ireland (border between Irish and international waters) to 30 degrees latitude, and Gander OCA from 30 degrees to the maritime boundary of Canada. New York Air Route Traffic Control Center (ARTCC) also provides services south of Gander airspace.
Every day, controllers at Shanwick and Gander issue the so-called North Atlantic Tracks (NATs), according to already defined waypoints in respective airspaces and the Gulf Stream (tailwinds from these streams can cut hours from the total flight time). Pilots must review these NATs, define them in their flight plans, and contact Oceanic Control half an hour before they enter Oceanic Airspace. Their intentions must be approved beforehand, with a defined flight level (altitude) to avoid collisions outside of radar coverage.
After entering Oceanic airspace, pilots must establish a two-way communication via High Frequency (instead of Very High Frequency, the reason is defined in my aforementioned article) radios with Shanwick Oceanic Radio or Gander Center, depending on their position.
Flights must report their exact position every 10 degrees of latitude to the air traffic controllers. New technology has made it easier to send these reports as ‘text messages’ via Controller–pilot data link communications (CPDLC) and Automatic dependent surveillance-broadcast (ADS-B) systems. However, they still need to have already established radio communication.
During their journey above Atlantic, every change in altitude and position must be coordinated with air traffic control and surrounding flights to avoid a collision. These changes should only happen in an emergency (for example, during rapid descent due to cabin depressurization).
Technical Requirements for Aircraft Wishing to Cross Airspaces Above Oceans
In 1936, the Federal Aviation Authority (FAA) restricted operations to within 100 mi (160 km) of an airport, regardless of the engine number, about 60 minutes away from an alternative airport with one engine inoperative. In 1953, the FAA "60-minute rule" restricted twin-engine aircraft to a 60-minute diversion area based on the piston engine reliability of the time. In the 1950s, the International Civil Aviation Organisation (ICAO) recommended a 90-minute diversion time for all aircraft, which was adopted by many regulatory authorities and airlines outside the US.
Airbus A300B4, the first aircraft to be certified with an ETOPS certificate [4].
Later, when jet engines, which were more reliable than piston engines, were introduced, the FAA introduced Extended Twin Operations (ETOPS) certificates. These certificates are usually issued to twin-engined jet aircraft which fulfil the technical requirements of bypassing the aforementioned rules. The first certified aircraft was Airbus A300B4 in 1977 with ETOPS 180, which meant it could fly 180 minutes away from a diversion airport.
FAA also introduced certifications for diversions of more than 180 minutes. In November 2009, the Airbus A330 became the first aircraft to receive ETOPS-240 approval, which has since been offered by Airbus as an option. On December 12, 2011, Boeing received type-design approval from the U.S. FAA for up to 330-minute extended operations for its Boeing 777-200LR, 777-300ER, 777F, and 777-200ER equipped with GE engines, and with Rolls-Royce and Pratt & Whitney engines expected to follow. Before the introduction of the Airbus A350XWB in 2014, regulations in Europe and the US permitted up to 180-minute ETOPS at entry. The A350XWB was the first to receive an ETOPS-370 prior to entry into service by European authorities. This means it can continuously fly around the planet, except over the South Pole.
In conclusion, these rules, however complicated they might appear to be, are effective at breaking physical boundaries of propagation effects on traditional radar coverage.
References
[1] User:Cosiabh/FlightServiceBureau. (2017, February 24). File:NAT-Tracks-24FEB17.png. Retrieved from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:NAT-Tracks-24FEB17.png [Image]
[2] North Atlantic Tracks. (n.d.). Retrieved from Wikipedia: https://en.wikipedia.org/wiki/North_Atlantic_Tracks
[3] ETOPS. (n.d.). Retrieved from Wikipedia: https://en.wikipedia.org/wiki/ETOPS
[4] Khashayar Talebzadeh (2010, May, 21). File:A300 Iran Air EP-IBT THR May 2010.jpg. Retrieved from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:A300_Iran_Air_EP-IBT_THR_May_2010.jpg [Image]