How Do Aircraft Find Submarines In Deep Water?

The main technique used to detect submarines is through the use of SONAR, which stands for SOund NAvigation and Ranging. This involves dropping a sonobuoy into the water, which sends the data to an aircraft. If a match is detected, another active buoy is launched to verify the submarine’s presence.

Submarines have a crucial advantage over ships – they can quickly disappear. The ability of a submarine to dive and travel while remaining underwater makes it one of the most coveted machines operating in the world’s waters.

However, thanks to sonar and other military technology development, submarines can now be located much more precisely. They can be detected by ships in the vicinity and aircraft flying thousands of feet above the water’s surface.

There are several ways to detect the presence of submarines underwater, but in this article, we will discuss the one used by most military aircraft to detect and confirm the presence of a submarine in a given area.

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The primary method of airborne anti-submarine warfare involves using SONAR – SOund NAvigation and Ranging. Simply put, SONAR is a technique that relies on sound waves to detect/locate objects in a particular region. You can read about SONAR in more detail in this article.

There is a specially-designed object – called a sonobuoy – that actually implements the SONAR principle to detect submarines underwater.

What Is A Sonobuoy?

A sonobuoy is a portable sonar system that can be dropped from an aircraft or a ship to detect submarines and conduct underwater research.

Sonobuoys are packed in canisters and installed in aircraft. They are ejected from the aircraft when it passes over a specific region above the water.

There are three main types of sonobuoys: active, passive, and special-purpose sonobuoys, which are used according to the nature of the mission.

How Sonobuoys Work

During an anti-submarine mission, aircraft are assigned a specific ‘target area’ to search for any underwater operating submarines. The size of the target area varies based on the type of submarine being searched for. 

For instance, if a nuclear submarine is a target, the aircraft crew must search a larger target area due to its higher mobility.

Once the aircraft reaches the designated target area, it conducts a radar search, followed by a visual search using sensors and onboard equipment to locate the submarine on the surface. If the submarine cannot be found on the surface, the aircraft crew then releases sonobuoys from the bottom of the aircraft to continue the search.

The moment a sonobuoy splashes on the water’s surface, it deploys. It can be pre-programmed to drop to any depth in the range of 90-1500 ft (27-457 meters). It consists of a radio frequency antenna at the top, which remains above the surface, a sail that remains just below the surface of the water to keep the sonobuoy stable, and a transducer at the end that collects acoustic energy from its surroundings and converts it into electrical energy, which is transmitted to the aircraft through the RF antenna.

The data that the deployed sonobuoy transmits will show up on the onboard computers of the aircraft. The operator then compares this data with their database, and if a match is found, it’s assumed that there is a submarine nearby.

However, in order to actually confirm the submarine’s presence in that region, another buoy, this time an active one, must be deployed. This buoy emits acoustic waves in all directions underwater. When these waves hit a submarine nearby, they bounce back and return to their ‘parent’ buoy.

This not only confirms the presence of a submarine in the vicinity, but also helps ascertain its position underwater, which is the best piece of information the aircraft crew on an anti-submarine mission could hope to obtain.

Drawbacks Of Sonobuoys

One of the significant disadvantages of sonobuoys is that they are designed to be used only once. As of the writing of this article, sonobuoys could not be recovered or reused for another mission. 

Another challenge that sonobuoys present is that they can be activated and potentially used by hostile forces (if their aircraft systems are compatible with the sonobuoy) if they are not scuttled in time.

There are a few other methods, such as Magnetic Anomaly Detection (a system onboard the aircraft), which further corroborate the work done by sonobuoys. However, as far as the detection of enemy submarines is concerned, sonobuoys are the first and most popular choice for navies all over the world!