Here's What You Need to Know: The F-15EX is, at least in terms of its external configuration, modeled upon 1980s engineering.

The most advanced and rapidly emerging Russian and Chinese-built air defenses are now much more likely to operate with an ability to detect even stealth aircraft to some degree, an emerging reality that continues to present something of a predicament for U.S. weapons developers seeking to preserve air supremacy against major power rivals.

Russian media claims that its upgraded S-400 and S-500 air defense systems can detect and destroy stealth aircraft, may have yet to be verified in some measurable way, and there is of course a massive margin of difference between merely “detecting” something in some capacity and actually being able to shoot it down.

Nevertheless, the prospect that this threat scenario presents may be valid, to even a small extent, is quite likely informing the tactical equation for U.S. war planners.

While many are possible of the view that, despite the growing threat, 5th-Gen stealth fighters such as an F-22 or F-35 are well equipped to address this kind of threat. What does it mean for 4th Generation aircraft? If the threats to 5th Gen stealth fighters are becoming much more substantial, how could a new fighter such as an F-15EX survive in this kind of threat environment?

Essentially, what would be the rationale for acquiring large numbers of new F-15EXs in a global threat environment such as this? Wouldn’t they be, quite possibly, rendered ineffective against the most pressing and substantial threats to U.S. air supremacy?

Some are likely to pose this question with new urgency in light of a recent revelation that the Pentagon has “skipped over” or simply avoided full-up system level survivability testing for the F-15EX, passing by the one true measure of whether the aircraft could still be relevant in a high threat environment. Without an established ability to operate amid the highest threat scenarios expected, could the now arriving F-15EX be obsolete upon arrival?

The scenario was taken up in a recent essay from Inside Defense which cites Pentagon documents confirming that Full Up System Level survivability testing for the F-15 has been waived.

“The Office of the Secretary of Defense has waived key survivability testing requirements for the F-15EX, approving a test plan the Air Force expects will save $108 million and reduce the testing schedule by at least one year. According to memos obtained by Inside Defense, former Pentagon acquisition chief Ellen Lord approved the waiver Jan. 10 and notified Congress Jan. 13, just days before she left her post and President Biden took office,” the Inside Defense story states.

Could the new administration add back the testing?

Many of the technical specifics may not be known for obvious security reasons, yet there are some broad parameters regarding newer air defenses which are of great relevance to consider.

New generations of advanced Russian-built air defenses are now engineered with previously unprecedented levels of digital networking among nodes to quickly exchange target information, high-speed computer processing increasingly enabled by AI, much longer-range and more precise radar technologies and a growing sphere of detection frequency. These are all factors inspiring the Pentagon’s rationale for engineering stealth upgrades into the F-35, B-2 and, perhaps most of all, building an entirely new generation of stealth with the B-21.

Chinese HQ-9 air defenses, reported to have appeared in areas around the South China Sea, are a fast-growing and serious threat as well.

“The HQ-9 is capable of engaging multiple aircraft, including combat aircraft. It resembles the Russian S-300 system but China is assessed to have developed variants of the system with a longer range, potentially up to 230 kilometers,” a DW report writes.

The changing threat scenario is part of why, for many years now, senior Air Force weapons developers have said that stealth configuration itself is but one element of a larger integrated approach necessary to elude modern air defenses. Speed, thermal signature management, radar absorbent coating materials, EW technologies to jam enemy radar and advanced sensing able to locate air defenses are all signature elements of the Pentagon’s cutting edge approach to stealth.

While the thinking with the waiver may be to simply use a new 4th-Gen-like aircraft for lower threat warfare scenarios, there are many less expensive platforms which can succeed in a non-contested or much less contested airwar environment. So why spend the money on the F-15EX if its ability to operate against the most likely and most significant threats is not known or established? Does the aircraft linger in a certain kind of liminal uncertainty, meaning that it might be overqualified for most uncontested environments yet insufficient to counter the highest threat or most contested environments such as those containing Russian or Chinese air defenses?

The F-15EX is, at least in terms of its external configuration, modeled upon 1980s engineering, yet it does contain quantum-like improvements in computing, radar range and sensitivity, avionics, sensing and weaponry. However, it simply is not stealthy. its construction, configuration, coating and external shape do not resemble the stealthy exterior of an F-22 or F-35, and it does not appear to have an internal weapons bay,

As a 4th-Gen 1980s airframe, the F-15EX is not as flat, sloped or rounded as a fifth-generation plane, and most likely not built with a mind to seams, bolts and other attachments specific to procedures needed to construct a stealth aircraft. The F-15EX also has a protruding cockpit, much like the original variants, as well as some sharp edges, likely to generate a stronger radar return signal.

Kris Osborn is the Defense Editor for the National Interest. Osborn previously served at the Pentagon as a Highly Qualified Expert with the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Masters Degree in Comparative Literature from Columbia University.

This article first appeared in March 2021. 

Image: U.S. Air Force photo/Chad Bellay