The latest accord will allow Israel to install its own radio and data link systems, as well as other equipment, on the F-35I models it is buying. Originally, stealth data links were an integral part of the F-35 mission system, restricting data communications within F-35 formations, or between F-35 and specialized communication-gateway platforms. The Multifunction Advanced Data Link (MADL), developed by Harris specifically for the F-35, provides a low-observable link that enables communications within F-35 formations and with MADL-equipped command-and-control elements. MADL uses six antennas providing spherical coverage around the aircraft. It use a Ku narrowband waveform employed in a “daisy chain” scheme—the first aircraft sends the directional signal to a second aircraft, then to a third aircraft, and so on.
The waveform offers lower probability of detection, and thus intercept, by enemy signals intelligence (sigint) and EW systems. Originally, it was exclusive to the F-35, but in coming years it will be integrated into other stealth platforms operated by the U.S. military, including the Lockheed Martin F-22 Raptor and Northrop Grumman B-2 bomber fleet. Since MADL is part of the F-35 communications/navigation/identification (CNI) mission system, Israel is expected to receive MADL, which will offer the IAF a data link commonality with foreign air forces for the first time. However, relying strictly on MADL means the F-35 will not be interoperable with the rest of the IAF combat fleet, so another solution has to be found.
In the past, the stealth community insisted on mission independence to secure maximum flexibility and ensure that their platforms' unique stealth characteristics are not compromised. The need to better coordinate stealth and nonstealth operations and to task the F-35 in future close-support missions, particularly for the U.S. Marine Corps, required the introduction of conventional systems such as Link-16.
In recent months the F-35 has tested the Link-16 and will soon test the Variable Message Format (VMF) protocol, widely used for close-air-support missions carried out by Western coalition forces abroad. This enhancement has also opened the opportunity for the Israelis to equip a stealth fighter with their own data link communication system. The current F-35 Link-16 application is believed to be reserved for nonstealth missions only, thus retaining the fighter's low-observable capabilities when operating in full stealth mode.
Israel has always insisted on adding specific systems into the platforms it procures from foreign sources. On U.S. fighter aircraft, these enhancements were focused on the insertion of indigenous EW systems; command, control and communications; data links; and integration of Israeli-developed weapons. These Israeli changes have garnered significant export orders, and some—such as the Litening advanced targeting pod—were integrated into USAF and Marine fighters including the F-16, F-15, AV-8B, A-10, F/A-18 and B-52.
Still, the Israeli EW deal was hard-fought, for a reason. Enabling JSF customers to include theater-specific threat libraries or a repertoire of jamming/countermeasure techniques, or issue frequent updates to these systems, requires a special approach compared with legacy, conventional EW systems. In the past, specific upgrades were issued to EW systems, which were kept separate from other avionics, thus enabling such changes.
In the F-35, all core avionics are integrated and fused; therefore, accessing part of the system requires integration with all associated systems. Having different air forces using different versions of core avionics would render such integration more complex and costly.
The avionic architecture of the F-35 solved this by introducing two separate integration levels. Customers can access the high level, introducing country-specific services, libraries or updates on their own, outside the aircraft software-upgrade cycles. The lower level is proprietary to the U.S. Joint Program Office and accessible only by Lockheed Martin. This level manages flight and mission-critical services, including flight controls, CNI and display, sensor management and self-protection. It also relates to the sensitive low-observable envelope of the F-35, an issue passionately guarded by the U.S.
Replacing core avionics with new systems at such a profound level of integration is unlikely, as it would require extensive testing by all F-35 operators with no obvious gain for the developer. The IAF is moving toward a different approach—the implementation of so-called integrated modular avionics (IMA). The concept has been in development under an Israeli Defense Research and Development Directorate program for several years and is currently being implemented under several pilot programs.
The architecture employs three layers for the integration of new applications—unified hardware, comprising a powerful general-purpose processor (GPP) and large memory bank, and a library of devices and services made available to developers, similar to a software developer kit. The common hardware would be adapted to each platform, and run common devices and services to enable developers to devise new applications designed for this generic processor, and deploy them on different types of platforms, rather than developing a specific, platform-unique application. Once the application is approved by the IAF, it could be fitted on different platforms, yet be easily maintained and upgraded over the years.