Ever wondered how pilots communicate with air traffic controllers on the ground when flying over the oceans? Air traffic controllers typically pick up aircraft using radar technology which is only about 200 miles off the coast. But, what after that, how communication over oceanic routes is accomplished?

After flying further than 200 miles over the ocean, aircraft typically go off the radar. As a result, pilots must use alternative methods to stay in touch with ground control. Let’s take a look at some of the few techniques:

Satellites

When flying over the ocean – when they are out of radar range – pilots typically rely on satellites to communicate with controllers on the ground. Now there are different categories of satellites, one of them being geosynchronous, meaning they fly along a fixed orbit along the earth’s surface. Therefore these satellites can be used to send and receive data via aircraft overflying oceanic routes.

The pilot will essentially upload the plane’s location to the satellite after which the satellite will relay this data to the controllers on the ground. Although being the most common method of relaying information, this is not the only technique though.

High-Frequency Radio

Some airplanes rely on high-frequency radio technology to communicate with air traffic controllers on the ground. It’s an older and less-reliable communications technology, but it’s still used by countless airliners. High-frequency radio technology involves relaying the airplane’s location to a network of receivers, which eventually pass the data to controllers on the ground.

Traffic Collision Avoidance System

While airplanes typically use either satellites or high-frequency radio systems to communicate with air traffic controllers on the ground, most of them also feature a traffic collision avoidance system. Traffic collision avoidance systems aren’t used to communicate with air traffic controllers on the ground, though. They are used to communicate with other nearby airplanes for the purpose of avoiding a mid-air collision.

Whether an airplane is flying over land or sea, its traffic collision avoidance system will constantly emit a signal. If another airplane encroaches upon the plane’s airspace, both pilots will receive an alert. The pilots can then take the necessary actions to avoid a collision.

The system, also known as ACAS (Aircraft Collision Avoidance System), monitors the airspace around an aircraft for other transponder-equipped aircraft that may present a collision threat. TCAS operates independently of ground-based equipment to provide pilots with guidance on how to avoid a potential collision.

Oceanic surveillance technology

New oceanic surveillance technology, designed to enable increased traffic to be managed safely, began live trials on 29th March 2019. The trial involves Nav Canada in the Gander Oceanic Flight Information Region (FIR) and the UK’s NATS in the Shanwick FIR, the contiguous sectors carrying nearly all the traffic that flies both ways between North America/Central America and Europe/Middle East.

Under this, instead of using radar to conduct traffic surveillance and separation, or continuing with traditional oceanic procedural air traffic control, the air navigation service providers (ANSP) use satellite-relayed automatic dependent surveillance-broadcast (ADS-B) position reports, which are transmitted by each aircraft every 4-8 sec. The early results – still under analysis – are looking positive, conferring safety validation for smaller separation distances, and a hugely increased probability that aircraft will be able to be cleared to fly at their chosen speed and best height.

Traffic crossing the North Atlantic is predicted to increase by 50% over the next decade, and the region already has the busiest oceanic airspace in the world by far.

Until now, aircraft flying between North America and Europe have always been invisible to air traffic control once they are more than about 350km off the coast on either side because at that distance from radar antennae they disappear over the radar horizon. Air traffic control officers (ATCO), however, still know approximately where each aircraft is because they report their position, height, and a time estimate for the next reporting point every 14 minutes or so. This is done via ADS-C (ADS – contract) via FANS (future air navigation systems) datalink. It works safely because aircraft are painstakingly released into their pre-cleared, one-way oceanic tracks at specific heights, time intervals, and speeds, so they maintain separation vertically and horizontally.

The possession of radar-like surveillance capability improves safety as well as efficiency and allows for much more precise monitoring, recording, and analysis of traffic behavior. Previously, if an aircraft began to deviate from its cleared track just after a position report because clearance details were misunderstood or entered incorrectly, it could take up to 15 minutes before ATC got a position update that revealed the error.

How long are transatlantic flights?

• London to New York: 8 hours.
• Los Angeles to London: 10 hours 30 minutes.
• Chicago to Frankfurt: 8 hours 20 minutes
• San Francisco to London: 10 Hours 25 minutes.
• Miami to London: 8 hours 40 minutes.
• Washington to Addis Ababa: 13 hours 15 minutes.

Sources

• Monroe Aerospace
• FlightGlobal
• NBAA
• thepointsguy (Cover photo)