Talking Stealth: USAF Pushes for 5th to 4th 'Gateway'


USAF officials are preparing by year’s end to begin flight testing of a communications gateway technology designed to solve the vexing problem of allowing stealthy aircraft to communicate with legacy fighters, though they operate using different protocols.

Credit: USAF

The goal is to “network” combat air forces so that pilots of the F-22 — and in the future the F-35  — can share data with those flying legacy aircraft such as the F-15 and F-16 aircraft, says Lt. Col. Scott Hamilton, chief of the tactical datalinks program branch at the service’s Air Combat Command (ACC).

The F-22 was designed to communicate covertly, only with other F-22s , using the intra-flight datalink (IFDL). Today, the thought of developing a stovepiped system seems unfathomable. But in the 1980s, designers envisioned a massive force of hundreds of F-22s that would maintain stealth in hostile airspace in part by not emitting communications that could be detected. These aircraft would handle the frontline mission of destroying enemy air defenses and establishing air superiority behind hostile lines in an air campaign by communicating only with one another over the IFDL. The original F-22 designers never envisioned the need for the fighter to communicate with legacy fighters, because what was thought to be hundreds of F-22s would be combined with the F-35 to constitute the combat Air Force of the future after older models retired.

That goal, however, proved to be optimistic. The service now has a silver bullet force of 183 F-22s , and is being forced to keep A-10s, F-16s and F-15s operating for far longer than planned owing to delays in fielding the Lockheed Martin F-35 . “We have found that for various reasons … these two categories of aircraft are unable to in some cases communicate effectively,” Hamilton says. The F-35 will use the Multifunction Advanced Datalink. Legacy aircraft, however, generally operate with Link 16.

So the technical challenge is allowing for each fighter, which essentially speaks a different language, to seamlessly link to the other, including data and voice. The hope is that the added information available to each pilot will make each fighter more effective. Though this does not make up for the fighters lost in recent force structure reductions, officers hope that each individual platform can be more effective.

The Air Force is among a group of Defense Department sponsors of the Joint Strike Fighter Enterprise Terminal (JETpack) Joint Capability Technology Demonstration (JCTD) program, a research project designed to demonstrate reasonably mature and producible technologies to solve this problem. Northrop Grumman is the lead contractor on the JETpack program. The company declined to comment on the project, citing sensitivities with customers.

Hamilton says that if funding is available, officials hope to begin flight tests of the basic JETpack equipment by the end of this year on surrogate aircraft. The JCTD is nearly finished, with about 18 of 24 months executed. The basic equipment includes various antennas, the terminal and what officials call “remote electronics” on the gateway itself.

The goal once flight testing proves successful is to transition the project into a “program of record,” meaning get official buy-in from Air Force leaders for funding and fielding of a program. Service officials are referring to this eventual program as the “5th to 4th” project – referring to the transfer of data from “fifth-generation,” or stealthy fighters with highly integrated sensors and avionics, to those less stealthy, legacy aircraft in the fleet.

The 5th to 4th operational concept calls for the gateway to be hosted on a separate platform that can maintain line-of-sight with needed receivers. This means the host aircraft must be able to fly high enough — such as the Global Hawk unmanned aircraft — to connect with forces behind enemy lines. Or, the host could possess enough stealth to operate behind enemy lines. One ACC slide depicting the concept shows a Global Hawk as a host, but the Air Force is pushing hard to terminate the program and mothball the aircraft it has purchased. Hamilton says the Air Force has not yet made a final decision on what the host aircraft will be.

Because the gateway aircraft will host all of the 5th to 4th components, engineers do not envision having to add equipment onto fighter aircraft. This was a primary goal , as adding any antennas onto the F-22 or F-35 without compromising their radar evading qualities could prove troublesome and costly.

Hamilton says that developing the antenna system for the gateway and avoiding electromagnetic inference within the system could prove to be the most challenging piece of the JETpack project.

Northrop, however, has experience with such gateways . The company was behind the Battlefield Airborne Communications Node (BACN) program, which was quickly crafted to field links on the Bombardier Global Express and the Global Hawk Block 20 to facilitate quick shuttling among tactical aircraft and intelligence collectors in Afghanistan. This program , however, did not address the issue of bringing stealthy aircraft into the network.

Though ACC is starting the 5th to 4th project with combat air forces in mind, Hamilton concedes that the system would likely be suitable for adding to intelligence collectors or, potentially, mobility air forces that could be operating in dicey locations.

Though not linked with the Air Force’s renewed interest in a more cohesive Anti-Access Area Denial strategy — after years of a focus on operating in permissive airspace over Iraq and Afghanistan — the project is picking up steam as a result of it. Hamilton says that several combatant commanders are expressing a need to network stealthy aircraft as they form their battle plans.

It is also possible that aircraft , such as the stealthy RQ-170 UAS acknowledged by the Air Force as operating in Afghanistan, could be brought into the network. And, it would be suitable for communications with other platforms that could be capable of operating behind enemy defenses.

At the end of the JCTD, Northrop Grumman is required to deliver multiple prototypes, Hamilton says.

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