Boeing F-15EX Eagle II
The Boeing F-15EX Eagle II is an American multirole fighter derived from the McDonnell Douglas F-15E Strike Eagle. The aircraft resulted from U.S. Department of Defense studies in 2018 to recapitalize the United States Air Force's tactical aviation fleet that was aging due to curtailed modernization, particularly the truncated F-22 production, from post-Cold War budget cuts. The F-15EX is a variant of the F-15 Advanced Eagle, a further development of the F-15E design initially intended for export and incorporates improved internal structure, flight control system, and avionics. The aircraft is manufactured by Boeing's St. Louis division.
The Advanced Eagle began with the F-15SA which first flew in 2013, followed by the F-15QA in 2020. The F-15EX had its maiden flight in 2021 and took advantage of the active export production line to reduce costs and expedite deliveries for the USAF; it entered operational service in July 2024. The F-15EX is expected to replace the remaining F-15C/D in the U.S. Air Force and Air National Guard for performing homeland and air defense missions and also serves as an affordable platform for employing large stand-off weapons to augment the frontline F-22 and F-35. The Advanced Eagle in this configuration represents the current baseline in F-15 production.
Development
In the 2010s, the United States Air Force was facing an incoming shortfall of its fighter fleet size in the 2020s due to deferred and downscaled modernization plans from budget cuts following the end of the Cold War in 1991, and the focus on asymmetric counterinsurgency warfare after the 11 September 2001 terrorist attacks. The USAF's procurement requirement of 381 production F-22s to replace its fleet of air superiority F-15A to D fighters was curtailed to just 187 in 2009. In order to retain adequate numbers of air superiority fighters, the service planned to extend the service of 179 F-15C/Ds to the 2030s, well beyond its originally planned retirement date. Also referred to as F-15 2040C or "Golden Eagle", these jets would have upgraded avionics, including active electronically scanned array radar, infrared search and track, and a new electronic warfare suite called the Eagle Passive/Active Warning Survivability System. Some of these upgrades would be shared with the F-15E fleet, such as EPAWSS whose development contract was awarded in 2015 to Boeing and BAE Systems. However, by the mid-2010s, the F-15C/D fleet was aging beyond the point of economic sustainability and would not be serviceable by the 2030s due to structural fatigue, while the F-35 was facing delays, resulting in a requirement to recapitalize the fighter shortfall as legacy F-15s retire by 2026. Restarting F-22 production was considered cost prohibitive due to the high non-recurring startup costs of rebuilding the production line and sourcing replacement parts vendors.File:Donald Trump state visit to Saudi Arabia, 2025-05-13 P20250513DT-0045.jpg|thumb|The Saudi F-15SA serves as the basis for the USAF F-15EX development.
Meanwhile, Boeing had been developing upgrades for the F-15E for export customers and a substantial update to the air vehicle design resulted in the F-15 Advanced Eagle; the F-15SA was the initial variant which first flew in 20 February 2013, followed by the F-15QA ordered in 2017. In 2018, following a series of Cost Assessment and Program Evaluation studies indicating that a mix of fourth- and fifth-generation fighters would allow the USAF to more affordably recapitalize its fighter fleet, the USAF and Boeing began discussing the F-15X or Advanced F-15, a proposed single-seat variant based on the F-15QA to replace USAF F-15C/Ds. Eventually, both single- and two-seat variants were proposed, called F-15CX and F-15EX respectively, with identical capabilities; the USAF opted for only the EX to reduce costs since only two-seat F-15 models remained in production, and in 2019, eight aircraft were included in the FY 2020 budget request. This would enable the use of the existing F-15 production line with minimal non-recurring startup costs to quickly bring additional fighters into service and also was a way to support Boeing's St. Louis division in order to maintain diversity in the U.S. fighter industrial base. The F-15EX improvements included the AESA radar, IRST, and EPAWSS from the existing F-15 upgrade programs while combining the benefits of the F-15QA such as the revised structure with a service life of 20,000 hours, new cockpit and flight controls, and the proposed AMBER system to enable the carriage of up to 22 air-to-air missiles.
Although it is not expected to be as survivable against the latest air defenses as the fifth-generation F-22 and F-35, the F-15EX can supplement the former in air superiority missions by performing homeland and airbase defense, enforcing no-fly zones against limited air defenses, and deploying outsized standoff weapons in support of stealth fighters at the frontline. In July 2020, the U.S. Defense Department ordered eight F-15EXs over three years for $1.2 billion. The F-15EX made its maiden flight on 2 February 2021.
On 7 April 2021, its official name Eagle II was announced. The FY2021 defense appropriations bill funded F-15EX procurement at $1.23 billion for 12 aircraft, bringing total orders to 20 aircraft with 144 total planned. By May 2022, the USAF reduced its orders to 80. The first operational F-15EXs are not to receive conformal fuel tanks. The Air Force's proposed budget for fiscal 2024 includes funds to buy 24 more F-15EXs, which would bring the planned fleet up to 104 aircraft. In the proposed budget for FY2026, $3 billion is set aside for the F-15EX, bringing the total to 129 aircraft.
Design
Overview
The F-15EX is a variant of the F-15 Advanced Eagle family of aircraft, a further development of the F-15E Strike Eagle design beginning with the F-15SA for the Royal Saudi Air Force. The Advanced Eagle consolidated several upgrades to the F-15E developed for export customers, including full integration of the General Electric F110-GE-129 and the AN/ALQ-239 Digital Electronic Warfare System that replaced the legacy TEWS, and introduced a revised wing structure for increased service life, an enhanced cockpit originally proposed for the F-15SE Silent Eagle and digital fly-by-wire control system that replaced the original hybrid electronic/mechanical system and enables the activation of two additional wing pylons; the fly-by-wire eliminated flutter modes causing stability issues that resulted in the two outboard wing pylons being deactivated in earlier F-15 variants. Starting from the F-15QA for the Qatari Emiri Air Force, the Advanced Eagle introduced a further revised wing structure that increased service life to 20,000 hours, the new Advanced Display Core Processor II mission computer, and a new cockpit with a large area display each for the pilot and weapon systems officer. Based on the F-15QA, the F-15EX incorporates the Raytheon AN/APG-821 AESA radar, BAE Systems AN/ALQ-250 EPAWSS, and the Lockheed Martin Legion Pod with AN/ASG-341 IRST21 sensor; in contrast to some other Advanced Eagle variants, the USAF F-15EX does not have the BAE Systems AN/AAR-57 Common Missile Warning System, although the blisters for these sensors were retained in order to minimize production changes and maintain the same aerodynamic profile for the fly-by-wire system.The F-15EX's large payload capacity enables a high level of flexibility. In a typical air superiority or escort configuration, the Advanced Eagle can carry twelve air-to-air missiles, either the AIM-120 AMRAAM or AIM-9 Sidewinder short-range missiles; the AGM-88 HARM can also be carried. Using proposed expanded racks and CFT weapons stations, it can potentially carry sixteen AIM-120s, four AIM-9s, and two AGM-88 HARMs, although this has not been tested or funded. For precision strike, it can carry sixteen GBU-39 Small Diameter Bombs, four AMRAAMs, one 2,000 lb Joint Direct Attack Munition, two HARMs, and two fuel drop tanks. The F-15EX can carry multiple large standoff munitions such as the AGM-158 JASSM, or outsized munitions like the AGM-183 ARRW to bring additional firepower behind the frontline F-22 and F-35.
While the Advanced Eagle's strengthened structure makes it heavier than earlier F-15 variants, the digital fly-by-wire control system and the increased dynamic thrust envelope of the F110-129 engines provide it with substantially improved maneuverability and handling characteristics over legacy F-15s and enables the pilot to maneuver aggressively with no angle-of-attack limits. The fly-by-wire also makes the aircraft much more departure-resistant and tolerant of asymmetric loads.
Avionics
While not as survivable as the stealthy F-22 or F-35, the F-15EX nevertheless incorporates advanced integrated avionics and protective countermeasures systems to improve the pilot's situational awareness and increase survivability. The F-15EX's APG-821 radar, initially designated APG-634, combines the AESA antenna of the APG-633 with the processor of the APG-79 found on the F/A-18E/F Super Hornet as well as a new cooling system and Radio Frequency Tunable Filters to enable simultaneous radar and electronic warfare functions while integrated with the AN/ALQ-250 EPAWSS electronic warfare suite. Leveraging the work and experience from AN/ALQ-239 DEWS, the EPAWSS is a digital system that provides all-aspect radar warning receiver function and threat geolocation; it is also integrated with the AN/ALE-47 chaff/flare countermeasures dispenser system. Both the pilot and WSO can use the Digital Joint Helmet Mounted Cueing System to cue weapons at high angles off boresight.In addition to radio frequency sensors, the F-15EX can mount the Legion Pod with the ASG-341 IRST21 sensor, which provides a passive means of threat detection especially against low-observable threats in the radio-frequency spectrum; the F-15SA and F-15QA mounts the AN/AAS-42 "Tiger Eyes", the precursor to the IRST21 sensor, on the targeting pod pylon. While the aircraft can be operated by a single pilot for basic air superiority missions, the back seat is fully missionized to support a WSO for complex missions and can potentially support the manned-unmanned teaming coordination with uncrewed collaborative combat aircraft. Although employed primarily as an air superiority fighter to replace the F-15C/D and complement the F-22, the F-15EX can employ the LANTIRN and Sniper XR pods like its F-15E precursor to perform ground attack. The avionics has an open systems architecture to facilitate potential future upgrades.