The U.S. Air Force is planning to request proposals from industry to finally provide needed communications connectivity between fifth- and fourth-generation fighters.

The service has long projected a need for so-called "5th to 4th" capability. This need is made even more urgent as the timeline for fielding the stealthy, fifth-generation F-35 has stretched out due to technical challenges in development and funding limitations at Air Force headquarters. And the service acquired far fewer stealthy F-22s from Lockheed Martin than originally planned, making the ability to connect each one to larger networks critical for campaign planning in future operations.

Though called "5th to 4th," a major long-term issue is how to allow for the F-22 and F-35 to communicate without using Link 16 alone, which would compromise their stealthy operations. Though both are manufactured by Lockheed Martin to meet Air Force needs, they were designed in different eras. F-22s can essentially only "talk" to other F-22s through a dedicated, low-probability-of-detection/low-probability-of-intercept system. The F-35, by contrast, uses the Multi-function Advanced Datalink (MADL) system, which employs a different waveform; the F-35 is slated for its Air Force operational debut as early as August 2016.

Air Force Chief of Staff Gen. Mark Welsh highlighted the need for a 5th to 4th system in his speech at the annual Air Force Association conference in Orlando, Florida, in February. But Air Combat Command has not articulated what, specifically, is required. The command declined a request for an interview on the subject.

Underscoring the need for a quick program is the fact that communications are a limiting factor to using F-22s operationally. They were considered for use in the Libya campaign in 2011, but planners were stymied by an inability to deliver data collected by the F-22s back to other forces, according to one industry source.

The service has proposed a program, the Multi-Domain Adaptable Processing System (MAPS), to address this need with what will likely be a pod to act as a gateway between the two stealthy fighters. It is likely this will be placed on fourth-generation fighters such as the F-16 and F-15 families, thus putting a reliance on the involvement in these older systems to support communications requirements.

The operational concept would be for the stealthy fighters to penetrate behind the "bubble," or threat zone, of air defenses, and communicate with one another by transmitting data through the MAPS system.

Though it enhances the communications among combat air forces, this operational concept is dependent upon the availability not only of the stealthy platforms to penetrate forward in a fight, but also on the presence of a fourth-generation fighter orbiting within range to support communications; this will likely add cost to execute certain campaign plans.

The service plans to issue a draft request for proposals for MAPS by the end of the second quarter of fiscal 2015, or March 2015, says Col. Anthony Genatempo, the director for the aerial, space and nuclear networks division at the Air Force’s Electronic Systems Center, which will head up the MAPS procurement. He hopes to announce competitive awards by the end of fiscal 2015.

Requirements for MAPS, however, are still being finalized.

In addition to the communications gateway, the service is planning to potentially include an infrared search and track sensor (IRST) in the final MAPS hardware, he says. Air Force planners are hoping to spend less than $100 million developing MAPS, though a final cost has yet to be refined.

MAPS will build off experience that the Air Force gained through the Talon Hate program, which aims to field four pods in the middle of fiscal 2015 to provide inflight datalink (IFDL) connectivity from the F-22 to fourth-generation fighters. This will allow for fourth-generation pilots in the rear of an air campaign to benefit from the tactical picture collected by the F-22 as it operates forward in a battle. Boeing is building these pods for use on the F-15C, which it manufactures.

At an estimated weight of 1,800 lb., the Talon Hate pods are expected to be about 17 ft. long. They will include the IRST, a Multifunctional Information Distribution System (similar to Link 16) capability, a satellite communications capability and an air-to-ground link.

Talon Hate is being spearheaded by the Air Force’s Tactical Exploitation of National Capabilities office, a congressionally mandated program designed to foster fielding capabilities across various service offices. Air Combat Command declined an interview request on Talon Hate but provided a data sheet on the subject. Boeing deferred all questions on the system to the Air Force.

Ultimately, the Air Force wants to have the ability for stealthy fighters to communicate among themselves, potentially independent of an external gateway, a capability notionally referred to as an advanced data link. For MAPS, though, "We are talking about a similar capability to Talon Hate in a different fashion – trying to reduce the size, weight and power of the components," Genatempo said. "It may be a pod, it may be partially in a pod. It may not be in a pod at all."

Both the F-22 and F-35 can receive Link 16 signals, but doing so might compromise their location if operations require stealth. So one question being addressed by Air Force officials is how to provide connectivity that is LPI/LPD while fifth-generation fighters are in the most dangerous airspace, where they were designed to operate.

Genatempo says the service is open to taking incremental steps toward the ultimate goal of fielding a direct link between the F-22 and F-35. He says cost is a key concern. "The biggest part I am trying to keep a cost control on is the development piece," he says. Production numbers would ultimately be dictated by the available budget.

The service hopes to eventually network the stealthy fighters and fourth-generation combat forces with other Pentagon assets, such as intelligence, surveillance and reconnaissance aircraft and satellites, Genatempo says, although this is not a firm requirement.

Boeing, Northrop Grumman and Lockheed Martin are all expected to submit concepts for MAPS. Northrop Grumman has demonstrated a similar gateway capability through the Jetpack joint capability technology program. Jetpack is designed to translate F-22 and F-35 messages into Link 16 messages to distribute the data to fourth-generation fighters (or forces operating on Link 16).

Lockheed Martin, by contrast, has demonstrated the ability to use a new waveform developed by L-3 Communications called Chameleon for direct communications among F-22s and F-35s without the use of a gateway. Lockheed Martin demonstrated Chameleon during flight trials in December; officials say signal strength remained under the detection threshold for an anti-access environment and the waveform can be transmitted via L-band antennas already on both platforms and only used for operations now at test ranges.

Lockheed Martin has spent its own internal research and development funding to develop the system, dubbed Project Missouri. What is unique about Project Missouri is its ability to allow for data to go back and forth using the Chameleon waveform without revealing the location of the stealthy aircraft, a plus for operations in highly defended airspace.

Lockheed officials are hoping the Air Force will provide funding for further demonstrations of Project Missouri.