F-15 Uses New Infrared Search And Track Pod To Shoot Down Target With AIM-9X Sidewinder

Legion Pod will enable F-15s and F-16s to detect and engage even stealthy aircraft without having to turn on their radars.

USAF

A U.S. Air Force F-15C Eagle has fired an AIM-9X Sidewinder air-to-air missile for the first time using targeting data provided by Lockheed Martin’s Legion infrared search-and-tracking pod. The AIM-9X live-fire mission took place during testing at Eglin AFB, Florida, on July 8, 2020, and involved an Eagle from the resident 85th Test and Evaluation Squadron (TES), the “Skulls,” part of the 53rd Wing. Five days later, an F-16DM from the same unit flew the first-ever operational test flight carrying the pod.

“Both the F-15C and F-16 teams have been doing phenomenal work under difficult conditions to rapidly field this new capability,” said Air Force Lieutenant Colonel Thomas Moser, commander, Operational Flight Program Combined Test Force, a joint 96th Test Wing/53rd Wing unit at Eglin.

USAF/TSgt John McRell

An F-15C from the 85th Test and Evaluation Squadron carrying a Legion Pod and an AIM-9X.

The Legion Pod will provide F-15C and F-16C/D pilots with the ability to identify, track and target aircraft, including stealthy platforms that cannot be “seen” on radar, in complex electronic warfare environments. The Legion Pod pre-developmental test phase began in early 2019. In a statement, Lieutenant Colonel Morser said the unit had completed 80% of required testing before it entered the official developmental test phase, which he says sped up developmental and operational testing considerably. “What would normally take several years has been reduced to 18 months from the start of DT to expected fielding,” he said.

USAF/TSgt John McRell

F-16s carry the Legion Pod on the starboard station under the air intake

Pairing the Legion Pod with the advanced capabilities of the AIM-9X is particularly significant. The AIM-9X Block II, also known as the AIM-9X-2, which entered service in 2015, offers a big leap ahead in capability with its data-link and lock-on-after-launch improvements, meaning it can be fired at an enemy without first locking its seeker on to the target. Today’s AIM-9X is more than just a short-range dogfighting air-to-air missile. Under certain conditions, its imaging infrared seeker can see well beyond the distance it can actually travel and an extended range variant is in development. You can read more about the AIM-9X and its growing capabilities in this past War Zone piece.

While the latest tests are a major development on the path towards formal fielding of the Legion Pod, the Air Force has been testing the system for a while. It was noted that a podded IRST that appears very similar to the Legion Pod was carried by an F-16C of the 64th Aggressor Squadron at Nellis AFB, Nevada, as long ago as 2013. Formal F-16 carriage and integration trials were subsequently undertaken by Lockheed Martin from 2015. In addition, shadowy F-16s based out of Area 51's Groom Lake flight test center were also seen toting the podded IRST in 2017. 

Jamie Hunter

This F-16C from the 64th Aggressor Squadron was photographed carrying a Legion Pod in 2013.

The Legion Pod flew for the first time on an F-15C in 2016 and the following year the Air Force selected the Lockheed Martin system over Northrop Grumman's Open Pod. Boeing was subsequently awarded a contract by the USAF to integrate the pod onto the F-15C, including $154.6 million for engineering, manufacturing, and development work, plus production, integration, test, and deployment. A total of around 130 pods were planned to equip the F-15C fleet.

As of November 2018, the Air Force's plan was to reach initial operational capability with the system on the F-15C in 2020. In May 2019, a picture emerged showing an F-15C from the 57th Wing at Nellis Air Force Base carrying a Legion Pod during the U.S. military's biannual Northern Edge exercise in Alaska, an advanced integration event. 

Lockheed Martin

The Legion Pod is fitted with Lockheed Martin’s AN/ASG-34 infra-red search-and-track (IRST) sensor, which can locate and track targets at long range. It also provides targeting information to enable the pilot to engage threats using the IRST alone, or in combination with other sensors, which provides a robust capability in all situations. This is particularly effective in dense electronic warfare (jamming) combat environments. Unlike a traditional radar, the IRST operates passively putting out no electronic emissions, which means it also reduces the risk of alerting potential opponents that they are being targeted.

Lockheed Martin

Legion Pod is actually a modular pod system that can accommodate additional payloads in the future, as well as the IRST in its front end. As such, it could offer an easy way to bring new capabilities to the aircraft that carry it, such as communications gateways, electronic warfare systems, or even other sensors. 

In recent years, the USAF F-15Cs have started carrying Lockheed Martin's AN/AAQ-33 Sniper Advanced Targeting Pod (ATP) on the aircraft’s centerline station. This is primarily used for long-range visual identification of targets, day or night. The Sniper pod primarily finds its targets by slaving its optics to the F-15C's AN/APG-63V3 radar. The pilot can also manually steer the Sniper pod or cue it to their Joint Helmet Mounted Cueing System (JHMCS), but it is far less capable when it comes to searching for and providing targeting data in the air-to-air regime compared to the Legion Pod's IRST.

Jamie Hunter

A California Air National Guard F-15C carrying a Sniper pod on its centerline station.

Lockheed Martin has also developed the IRST21 sensor, which was based on the earlier AN/AAS-42 IRST system that was fitted to the F-14D Tomcat. Another version of that system, known as Tiger Eyes, is now featured on export versions of the F-15 Strike Eagle and Advanced F-15 Eagle.

IRST21 is being fielded by the U.S. Navy on its Block III F/A-18E/F Super Hornet, as well, and it reflects growing popularity of IRST carriage on 4th generation fighter platforms in U.S. military service. For more detail on how IRSTs are employed and why they have become so important to modern fighter aircraft, click here, but in this case, using the IRST with the AIM-9X signifies a big capability boost. 

A fighter equipped with the IRST carrying Legion Pod and an AIM-9X can hunt and kill targets, even just beyond visual range, in a largely electromagnetically silent state. It can do this while also leveraging the maximum efficiency of the AIM-9X Block II. The targeted aircraft wouldn't be alerted as to the incoming missile presence even during its terminal stage of flight because the AIM-9X uses an imaging infrared sensor (IIR), which is also passive. As such, IRST and AIM-9X together are one heck of a 'hunter-killer' team.

These types of tactical opportunities are just another reason why advanced IRSTs are becoming absolutely critical kit on fighter aircraft. 

Contact the author: Jamie@thedrive.com