Some interesting details can be found in the first photos of the F-15EX, which are useful also for a comparison with the F-15C that will be replaced by the new fighter.
The first F-15EX built for the U.S. Air Force took to the skies for its maiden flight on Feb. 2, 2021. The aircraft flew only with its primer paint and a small serial number (20-0001) on its twin tails, a common practice for the first flight of any newly built aircraft that leaves the production line. It will receive its final colors and insignias at a later stage, after completing functional checks and certifying the airworthiness.
Today we will give a closer look to some of the details of the new aircraft, thanks to the photos kindly sent to us by Jerry McGrath of Cryonic_Photography and one that we didn’t publish last time, sent to us by Alex Farwell of vikingaeroimages.
During the first flight, test pilots Matt Giese and Mike Quintini took the F-15EX up to 40,000ft and Mach 2, as reported by aviation photographer and journalist Jamie Hunter. In an interview to The Warzone, Giese said that the flight profile closely mirrored the standard Boeing Acceptance Test Procedure (ATP) with few differences for the specific configuration, with engine checks at various altitudes, engine shutdowns and air restarts, in addition to the checks of the various systems aboard the jet.
A detail that many of our readers noticed in the comments is that the F-15EX is a two seats aircraft and it will replace the F-15C which is a single seat aircraft, with only the D model being in a two seats configuration as it is used for training with an instructor in the back seat. When the F-15X program, also known as Advanced F-15, was first launched, both a single and two seat variants were proposed, called F-15CX and F-15EX respectively, and both with the same exact capabilities.
The Air Force ultimately decided to go only with the two seats variant, which will reportedly have the option to fly with a single pilot or with both pilot and Weapons Systems Officer (WSO), with the latter being an important addition in complex missions which could also feature the command and control of “Loyal Wingman” drones in the future. One of the reasons for this decision is also the fact that only the two seats variant of the F-15 is still in production, and the F-15EX program is all about the most affordable and immediate solution that can be fielded to refresh the Eagle fleet.
Initially the F-15C/D was to be entirely replaced by the F-22A Raptor, the first 5th gen. fighter aircraft of the U.S. Air Force. The service planned to buy 750 Raptors to replace both the F-15 Eagle and the F-16 Fighting Falcon, but that number was cut to 187 production aircraft, which is also less than the about 230 F-15C/D still in service. Because of this, the operational life of the Eagle had to be extended as it was initially scheduled to be retired in 2019.
While a first Service Life Extension Program (SLEP) required only a replacement of the longerons to maintain structural integrity, the Eagles now need new wings, as they have long surpassed their expected service-life estimates. To give you a better idea, consider that the youngest F-15C has been in service for 35 years already. In 2019, the decision was made to allocate the funding for the first eight of at least 144 F-15EXs, as this would be a more practical solution than waiting for enough F-35s to be available to replace also the F-15C. The contract was then signed during the last summer.
As for the F-35 replacing some of the F-15C squadrons, this intention has been confirmed again this summer by the Air Force, when it was announced that the 125th Fighter Wing of the Florida ANG, stationed in Jacksonville, will trade its F-15s for new F-35s in 2024; the 173rd Fighter Wing of the Oregon ANG, stationed at Kingsley Field, will become the first F-15EX Formal Training Unit (FTU) in 2022, and the 142nd Fighter Wing of the Oregon ANG, stationed in Portland, will become the first F-15EX operational unit in 2023. The press release then added that the remaining ANG F-15C units in Massachusetts, California and Louisiana will be replaced by either F-35As or F-15EXs.
Now, back to the photos and the other details.
If we look at the cockpit, we can notice that both the pilot and the WSO are wearing the new Joint Helmet Mounted Cueing System II (JHMCS II), similarly to the F/A-18F where both the crew members are equipped with the JHMCS and differently from the F-15E where the WSO wears only the standard HGU-55/P helmet. The new helmet features some improvements over the current JHMCS, with one of the most noticeable being the color symbology replacing the single-color symbology. The color symbology is currently an exclusive of ANG pilots flying with the Scorpion helmet on the F-16C Block 30 and A-10C.
Even if the test pilots flew with the new helmet, there are no official info about USAF intentions to acquire the new helmet. However, last summer the Air Force published a Request For Information (RFI) for a new Helmet Mounted Display (HMD) to equip the F-15EX. The notice mentions that the new helmet should provide the same or better capability than the current JHMCS while significantly reducing the head, neck, and spine burden placed on aircrews.
Giving a closer look at the cockpit, we can spot another detail which is the presence of the Low Profile Head-up Display (HUD) of Elbit Systems of America, the same company that also produces the JHMCS II. The digital HUD, more compact and lighter than traditional systems, has been installed also on the Gripen E/F and the F/A-18E/F Block III Super Hornet. As a matter of fact, Elbit provides advanced cockpit systems like the HUD and the Large Area Displays for all the three fighters.
The F-15EX, to be more specific, has a full glass cockpit equipped with a 10×19-inch touch-screen multifunction color display and JHMCS II both in the front and rear cockpit, Low Profile HUD in the front, stand-by display and dedicated engine, fuel and hydraulics display, in addition to the standard caution/warning lights, switches and Hands On Throttle-And-Stick (HOTAS) controls, as opposed to the F-15C that it is going to replace, which has a mainly analogic cockpit with some new displays added in the recent years.
The systems are powered by the Advanced Display Core Processor II, reportedly the fastest mission computer ever installed on a fighter jet, and the Operational Flight Program Suite 9.1X, a customized variant of the Suite 9 used on the F-15C and F-15E, designed to ensure full interoperability of the new aircraft with the “legacy Eagles”.
The whole development of the F-15EX’s avionics is based on DevSecOps and Open Mission Systems (OMS) architecture. DevSecOps is an open-source approach implemented by the Department of Defense to unify software development (Dev) with “baked-in”cybersecurity(Sec) and software operation (Ops), allowing shorter development cycles and more frequent delivery of upgrades to the operational squadrons. The OMS architecture will allow to add new or improved capabilities on operational aircraft very quickly and at a reduced cost, thanks to the common interfaces and data formats that are shared by all systems and producers.
The first F-15EX was not carrying any sensors, other than the AN/APG-82(V)1 Active Electronically Scanned Array (AESA) radar, the same chosen for the F-15E Radar Modernization Program. The radar, which has been developed from the APG-63(V)3 AESA radar of the F-15C and the APG-79 AESA radar of the F/A-18E/F, allows to simultaneously detect, identify and track multiple air and surface targets at longer ranges compared to mechanical radars, facilitating persistent target observation and information sharing for a better decision-making process.
Two other sensors are planned to be integrated on the F-15EX, the Legion Pod InfraRed Search and Track system (IRST) and the Sniper Advanced Targeting Pod. Both systems are already integrated on the F-15C and will be transferred to the new aircraft, without the need to acquire new ones.
Looking around the cockpit, we can notice a few antennas, which seem to be less than the ones on the F-15C and F-15E. The most noticeable are the three blade radio antennas, one behind the cockpit and the other two below the front fuselage. These antennas seem to be of the same type that was installed on the “legacy Eagles” in the 2000s together with new UHF/VHF radios. Another smaller antenna can be seen below the fuselage, just behind the two radio antennas, similar to the one that was used for the AN/ALR-56C Radar Warning Receiver on the previous versions of the Eagle.
Four white round antennas can be seen on the wingtips and on the vertical tail fins, similar to the ones found on the F-15C and F-15E for the RWR. The F-15EX, however, does not use the ALR-56C RWR. These five antennas may be part of the new AN/ALQ-250 Eagle Passive Active Warning Survivability System (EPAWSS) electronic warfare and electronic surveillance system, which is fully integrated with radar warning, geo-location and increased chaff and flare capability to detects and defeat surface and airborne threats in signal-dense and highly contested environments, according to BAE Systems.
Chaff and flares capacity has been increased by 50%, with four more dispensers added in the EPAWSS fairings behind the tail fins (two for each fairing), for a total of 12 dispenser housing 360 cartridges. This improvement is important as in modern scenarios chaff and flares are often released preemptively to counter MANPADS (Man Portable Air Defense System), meaning that now the Eagle will have more countermeasures available for a better protection.
The number of countermeasures could be increased even more if the USAF decides to transfer to the F-15EX also the ALE-58 Back-of-Launcher (BOL) countermeasure dispensers that are currently available for the F-15C and can be attached to the rear of the LAU-128 missile rails. It is not known if the F-15EX will receive also towed decoys among its countermeasures.
EPAWSS, an US-only system that will be retrofitted also to the F-15E, was recently tested during the Large Force Test Event 20.03 at Nellis Air Force Base (Nevada) in November 2020. This type of events has now been redesigned Black Flag and, differently from the more famous Red Flag, is solely focused on test and tactics development in a realistic, massed force, fully integrated, high threat density environment.
Here is a brief description of EPAWSS provided by the USAF:
The EPAWSS is designed to provide indication, type and position of ground-based RF threats as well as bearing of airborne threats with the situational awareness needed to avoid, engage or negate the threat. The EPAWSS defends against RF and IR threat systems detecting or acquiring accurate targeting information prior to threat engagement thus complicating and/or negating an enemy threat targeting solution. The system counters threats through its suite of components with electro optical and RF techniques.
When we wrote about EPAWSS in some previous articles here at The Aviationist, we mentioned that it complements the AN/AAR-57A(V) Common Missile Warning System (CMWS) designed to detect infrared threats. However, that proved to be inaccurate, as BAE Systems’ officials confirmed to us that EPAWSS is not integrated with CMWS. Upon further review of the available info, it seems that the F-15EX may not receive ultraviolet-basedMissile Approach Warning Sensors (MAWS) to detect InfraRed-guided missiles, even if the aircraft features the same mounting points used for these sensors on the F-15QA and F-15SA.
BAE officials also released the following statement to us: “EPAWSS can integrate with multiple sensor sources to provide warfighters with enhanced survivability via a fully integrated countermeasure response. EPAWSS was designed with the future battlespace in mind, with an architecture and interfaces that can take advantage of emerging new sensing sources.” Having considered this, we may hypothesize that the mounting points for the MAWS sensors have been installed to allow a future integration of other sensors in the EPAWSS suite.
These sensors, that have never been installed on the F-15C and F-15E, were installed for the first time on the F-15QA and F-15SA that are equipped with both theAN/ALQ-239 Digital Electronics Warfare Systems (DEWS) and CMWS. On these fighters we can find five sensors: two just below the canopy rails on each side, one behind the speed brake and the last two on the two fairings for the EW systems on the tail.
Looking above the fuselage, and precisely over the engine air intakes, we can notice that the bleed air louvres behind the bypass air spill doors have been replaced by four rectangular vents. This redesign seems to be an exclusive of the F-15EX, as the SA and QA variants are still using the old louvres. The exhaust for the air conditioning system behind the cockpit has not been modified.
Moving back towards the tail, two small antennas can be seen marked by red paint. While their exact purpose is unknown, they might be used for telemetry, as they were spotted only on the first F-15SA and the first F-15QA.
On previous variants of the F-15, the tails fins sported two different versions of the small fairings that housed RWR and ECM equipment. Actually, this equipment was housed in the bigger fairing on top of the left fin, while on the right the smaller one was just used to match the weight of the other fin. On the SA, QA and EX variants, the RWR and ECM equipment has been relocated and the two fairings on top of the tail fins are now symmetrical.
Looking at the underside of the F-15EX, we can get a better look at the Conformal Fuel Tanks or FAST packs (Fuel And Sensor Tactical). These 750 gallons (2,839.1 l) tanks, which are rarely seen on the F-15C and always used on the F-15E Strike Eagle, remained unchanged, with their six mounting points for weapons and the to for the sensors like the Sniper ATP. Unlike standard external fuel tanks, the FAST packs can’t be jettisoned inflight, however they do not affect excessively the performance of the F-15, as they allow the same maneuverability without g-load limitations, but only a structural restriction to not exceed Mach 2 (the reported max speed of the F-15 is Mach 2.5).
Continuing to look at the underside, we can notice under the wings the attachment points for the weapon pylons. As you may know already, the new F-15EX will be able to use four underwing pylons instead of the two that we usually see on the F-15C and F-15E. Actually, the two outer pylons are not really new, as the F-15E (and possibly the C too) already had provisions for them, however they were never used for unspecified reasons.
With the integration of fly-by-wire on the F-15SA, QA and EX, Boeing said it was now possible to integrate the additional pylons without problems. By using these outer wing hardpoints and possibly new weapon racks, the F-15EX will be able to carry a way higher payload than its predecessor, with up to 22 air-to-air missiles in air-to-air configuration.
Last detail, but not least, the famous “turkey feathers”. The Pratt & Whitney F100-PW-220 and -229 engines used by the Eagle and the Strike Eagle in the USAF are known for having their nozzles exposed and lacking the so-called “turkey feathers” cover plates. These covers were removed in the 1970s to make maintenance easier, reportedly after some were lost in flight due to fatigue or over-stressing and other damaged by the heat. The covers are still used on the older Israeli F-15I and South Korean F-15K and the newer F-15SA, QA and EX.
The F-15EX however will not use the P&W engines, at least for now. The Air Force awarded General Electric a contract for a first lot of engines that includes 19 F110-GE-129A 29400-pound thrust engines, of which 16 will be installed on the aircraft and three will be spares. According to the Air Force Materiel Command, the engine directorate “used a 20 percent factor for spare engines.” Initially the Air Force planned to award sole-source contracts to General Electric for 461 engines that would power the 144 F-15EXs, in an effort to speed up the program.
However, Pratt & Whitney protested and the Air Force responded that will hold an open competition if the company certifies the F100 engine, most probably in the F100-PW-229 29160-pound thrust variant used on late model F-16s and F-15Es, at its own expense on the F-15EX. A new contract solicitation is expected soon, with a pre-solicitation already published for 461 engines to be delivered beginning June 2023. The document mentions that all the design, development, modification, documentation, testing, and airworthiness certification needed to incorporate the engine in the F-15EX must be completed before the beginning of the deliveries.
The first two aircraft, F-15EX-1 and F-15EX-2, are expected to be delivered to Eglin Air Force Base during the second quarter of this year, just in time for the 49th anniversary of the first flight of the first F-15A on July 27, 1972. The new aircraft may look like an Eagle externally, but inside it will a completely different aircraft, compared to its predecessor. At Eglin, the 40th Flight Test Squadron will take possession of EX1 and the 85th Test and Evaluation Squadron will own EX2, with the goal of completing the combined developmental and operational testing simultaneously and as soon as possible.
About Stefano D'Urso
Stefano D'Urso is a freelance journalist and contributor to TheAviationist based in Lecce, Italy. A graduate in Industral Engineering he's also studying to achieve a Master Degree in Aerospace Engineering. Electronic Warfare, Loitering Munitions and OSINT techniques applied to the world of military operations and current conflicts are among his areas of expertise.