The F-15 Eagle is a proven air superiority fighter. The F-15’s air-to-air record is sterling; with over 100 confirmed kills and no losses, making the F-15 undefeated. Given the F-15’s track record, the jet is still relevant today, despite being introduced half a century ago.
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The plan was to phase out the F-15 and replace the massive, fourth-generation fighter with the fifth-generation F-22. Yet, the F-15 remains a foundation of the USAF’s force structure, despite the successful introduction of the F-22. Consistently upgraded with new avionics, the F-15 has remained relevant. And despite being designed strictly as an air superiority fighter, “without a pound for ground,” the airframe has successfully been adapted into a ground-strike variant, the F-15E Strike Eagle, which was introduced in 1986. In all, the F-15 program has been fantastically successful.
Although, one F-15 variant, the F-15SE Silent Eagle, failed to take flight.
The Silent Eagle was introduced in 2009. As the name suggests, the Silent Eagle was intended to incorporate stealth technology into the venerable, proven F-15 airframe. “The F-15SE Silent Eagle aimed to bridge the gap between fourth and fifth-generation fighters, incorporating elements of the stealth and situational awareness offered by the world’s most advanced tactical jets into an already legendary fighter airframe,” Alex Hollings wrote for SandBoxx.
The F-15 – while successful in combat, and technology advanced by the standard of the Cold War – lacks the stealth technology for penetration against modern air defense systems. Accordingly, the F-15 would be limited in early days of a conflict against a sophisticated adversary like Russia or China. The Silent Eagle offered to bring the F-15 platform up to date, capable of evading detection in modern combat environments.
Boeing had additional motives in developing the Silent Eagle; they hoped to target the export market and siphon business away from their competitor, Lockheed Martin, who had cornered the stealth export market with their F-35 Lightning II.
In many respects, the Silent Eagle was quite similar to the Strike Eagle, albeit with some notable distinctions. For example, whereas the Strike Eagle bristled with external missiles and fuel tanks, the Silent Eagle was fitted with a conformal weapons bay and fuel tanks, which limited the airframe’s radar cross-section. An additional benefit of the conformal weapons bay: the Silent Eagle could carry four additional air-to-air missiles.
In all, the Silent Eagle was able to carry plenty of weapons, including AIM-120 AMRAAM and AIM-9 Sidewinder air-to-air missiles, JDAM satellite-guided bombs, and Small Diameter Bombs. The Silent Eagle could even carry the Raytheon AGM-88 high-speed anti-radiation missile (HARM) “commonly leveraged by Wild Weasel aircraft hunting for enemy radar systems, making the Silent Eagle a viable and even potent option for SEAD (Suppression of Enemy Air Defenses) operations,” Hollings wrote.
The Silent Eagle’s vertical stabilizers were modified, too. While F-15 variants A through E all featured vertical stabilizers that stood straight upright, parallel to each other, the Silent Eagle’s stabilizers each canted outwards, away from each other, at 15 degrees. The modification was engineered to further reduce the Silent Eagle’s radar cross-section. The 15-degree canting also improved the Silent Eagle’s lift – and the increased lift improved the Silent Eagle’s range by 75-100 miles.
To further reduce the Silent Eagle’s radar cross-section, the jet was coated in radar-absorbent materials. “RAM is used on modern stealth fighters to minimize the radar return created by the facets of their designs that couldn’t be adjusted to deflect radar waves – things like ramjet inlets, the fighter’s nose, and the leading edges of its wings,” Hollings wrote. The end result, the F-15 SE “was a mechanical powerhouse that could tiptoe through the sky and speak in hued tones. But beneath the thin veneer of stealth, the F-15SE was still every bit the bruiser it started out as.”
The Strike Eagle never caught on with international buyers, who wanted the F-35. “Boeing offered up the Silent Eagle at around $100 million per aircraft, but South Korea ultimately chose to shell out as much as $176.5 million per F-35 to procure 40 truly stealth jets.” The decision, to side with the F-35 over the F-15SE, was universal: South Korea, Israel, Canada, Japan, and Saudi Arabia – all went with the true stealth fighter, the fifth-generation F-35. The Silent Eagle has since faded into obscurity, becoming a footnote in the storied history of the F-15 fighter.
The F-15 story isn’t over, however. A new iteration, the F-15EX, which incorporates many of the upgrades found in the Silent Eagle, is under development. Actually, in July 2020, the Air Force signed a $1.2 billion contract with Boeing to produce the F-15EX – suggesting that the EX may endure in a way the SE did not.
Harrison Kass is the Senior Defense Editor at 19FortyFive. An attorney, pilot, guitarist, and minor pro hockey player, he joined the US Air Force as a Pilot Trainee but was medically discharged. Harrison holds a BA from Lake Forest College, a JD from the University of Oregon, and an MA from New York University. He lives in Oregon and listens to Dokken. Follow him on Twitter @harrison_kass.