Allied P-8 Poseidon crew shares what it was like hunting down and torpedoing a US Navy nuclear submarine in big Pacific drills

• An Australian P-8A anti-submarine warfare aircraft targeted and dropped training torpedoes on a US nuclear submarine.
• The exercise occurred off the coast of Hawaii during RIMPAC 2024.

The crew of a Royal Australian Air Force P-8A Poseidon maritime patrol and anti-submarine warfare aircraft shared their experiences tracking a US Navy nuclear submarine and dropping training torpedoes on it off the coast of Hawaii last Wednesday.

The drill, part of the large multinational Exercise Rim of the Pacific (RIMPAC), was a rare opportunity to test the plane's patrol and reconnaissance capabilities against a live target, the aircraft's crew said, per a release on the training.

The P-8A Poseidon, which succeeded the older P-3 Orion, usually serves in a surveillance and deterrence role. Since it first entered service in 2013, it's become widely considered one of the most sophisticated maritime patrol aircraft available, featuring various technical capabilities for detecting and tracking subs and ships. The anti-submarine warfare plane also possesses the ability to engage hostile vessels

The Australian P-8A was joined by a US Navy P-8A and an MQ-9A unmanned aerial vehicle, which recorded the exercise, according to a news release from US Third Fleet.

The submarine targeted was the US Navy Los Angeles-class attack submarine USS Topeka (SSN 754). The nuclear submarine is the fourth improved Los Angeles-class vessel, featuring a more durable hull that allows the warship to dive deeper than other unmodified vessels of its class.

To find the sub, the Poseidon began with range surveillance, "essentially flying a grid search pattern at low altitude to hunt down the exact location of the submarine," the release said. In the exercise, the P-8s were given the broad coordinates for the submarine's location, but the crew had to independently "establish organic tracking and attack criteria," 3rd Fleet said.

The P-8 turned to its sonobuoys to map the sub's movements. These are acoustic sensors used to find submarines. A float with a radio transmitter remains on the surface while a hydrophone is submerged for detection.

"We dropped sonobuoys to determine the track of the submarine," No. 11 Squadron Commander and Tactical Coordinator, Squadron Leader Tristan Hull, explained.

Hull added that "once we were able to establish position, course, and speed of the submarine we were able to derive a solution that met our attack criteria and appropriate weapon placement to ensure maximum success."

After locating the Topeka, the Australian sub-hunter dropped four Mark 54 exercise torpedoes. Hull described it as a detailed process involving the sonobuoys being placed correctly in the area, the acoustics operator accurately interpreting the information to locate the sub, and then the P-8A pilot flying over the target in time.

It was the first time an Australian P-8A dropped this variant of the Mark 54 Lightweight Exercise Torpedo, the news release noted.

The larger RIMPAC exercise, during which this training occurred, is the world's largest international maritime exercise focused on the Indo-Pacific region. This year's exercise, the 29th iteration, included participants from across the region and beyond.

Tracking, detecting, and engaging submarines in exercises such as this one helps train aircraft crewa to better understand how to identify the various acoustic elements of a sub and how they differ from the feedback and noise of the surrounding ocean.

Maritime patrol aircraft crews routinely track submarines outside of structured exercises. Doing so can provide valuable intelligence about the undersea capabilities of potential foes. Recently, an anti-submarine warfare plane belonging to a NATO ally followed a Russian submarine in the Baltic Sea, and before that, a US plane kept tabs on another Russian sub before it docked off the coast of Cuba.