Sensor fusion is useful for a conventional fighter and can be phased in via upgrades, but it is essential at IOC if stealth is a primary goal.
A major impediment to flexibility in stealth aircraft is networking. Emcon paradoxically complicates networking while depending on it. One powerful Emcon tool is sharing active RF functions among aircraft in a fighting unit. The F-22 and F-35 were specified to have low-probability-of intercept (LPI) data links to connect a flight of aircraft.
LPI data links, however, use individual pencil beams, low-sidelobe antennas and power management to make detection difficult, which limits users and range. The F-22 can transmit only non-stealth voice radio outside the normal four-ship unit, while the F-35's Multifunction Advanced Data Link (MADL) will not talk to F-22s, and the aircraft will have non-LPI Link 16 for communication with other aircraft.
An effort to retrofit stealth aircraft with MADL has been deferred, but the Air Force funded Northrop Grumman to demonstrate a system known as JetPACK (Joint Strike Fighter Enterprise Terminal) that connects F-22s and F-35s with the rest of the force via an airborne gateway that communicates with their intraflight data links.
Missing from the baseline Block 3F service-entry standard is compatibility with Rover (remote video receiver) systems, which is essential for close air support. (Rover did not exist when the F-35 requirement was written.)
South Korea's approach to the KF-X is another way forward. The Block 1 variant is expected to have a low-observable airframe, with semi-conformal and external weapons and sensors. The Block 2 will be fully stealthy, with a conformal weapons bay. This gives South Korean industry the option to develop sensor fusion and Emcon incrementally and provides options for customers, who could operate a mix of versions, avoiding the total costs of an all-stealth force and diseconomies of a mixed force. But it blurs the line between stealth and conventional aircraft.
Tap the icon in the digital AW&ST Defense Technology edition for an interactive feature on stealth and counterstealth in the 2020s, or go to AviationWeek.com/stealth