Differences from the F-15E
Conformal Weapons Bays ( CWB): A/A and A/G ordnance carried "outside" the jet increase the RCS of the aircraft. For this reason F-15SE features 4 internal weapon bays capable of carrying missiles and bombs. These bays are built into the conformal fuel tanks hence their name. This is a unique feature of the Silent Eagle, greatly increasing its stealth capabilities at the cost of reducing CFT fuel capacity considerably, which reduces aircraft's combat radius by 180-200 nm (to about 800 nm for A/G missions and 720 nm for CAP missions - using F110- GE-129 engines). Please note that these are factory data obviously calculated for ideal conditions. Real life combat radius will be somewhat smaller than these.
Note that the Silent Eagle maintains a modular approach: the CWBs are built into a standard CFT, which attaches to the aircraft just like an ordinary CFT. This means that if there are no requirements for reduced RCS (no A/A opponents are expected), the aircraft can quickly be equipped with normal CFTs, thus increasing range and loiter time. The change of CFTs requires around 2 hours and can be performed easily under field conditions. For another 1 hour work the underwing pylons can be put back on the jet for another hardpoint and two more external fuel tanks. This way the Silent Eagle can fly counter-air missions at the starting stages of an air campaign and once air dominance is achieved, it can convert back to the "traditional" mud mover role and fly A/G missions afterwards.
Weapons: As for A/A ordnance, the Silent Eagle can internally carry the AIM-9 Sidewinder and the AIM-120 AMRAAM, one missile per CWB. From the AMRAAM family only the an AIM-120C or later model can be carried internally, since this has smaller wingspan designed specially for internal carriage.
For A/G ordnance the jet is able to internally carry 500 lbs and 1,000 lbs JDAM bombs (one weapon per CWB) and the 250 lbs GBU-39 SDB (two weapons per CWB).
For a multirole mission, internally carried weapon loadouts can be split between the above mentioned A/A and A/G weapons. If no stealth capabilities are needed, the aircraft can be changed back to a normal strike profile, using normal CFT's - in this configuration the aircaft performs just like an F-15E Strike Eagle in terms of weapon payload and employment capabilities.
Vertical Stabilators: The twin tails of the F-15SE are canted outwards by 15 degrees (see image above), this helps to decrease the aircraft's RCS in air-to-air engagements. This is probably the most visible difference between the Strike Eagle and the Silent Eagle. As an added bonus, canted tails (the same design is used on the F/A-18 Hornet) improve aerodynamic efficiency, generate lift and reduce airframe weight (by allowing to remove some 400-500 lbs of ballast weight from the front section of the aircraft) too.
RCS Reduction: Although the aircraft's fuselage is very similar to the Strike Eagle by the look, it's quite different in reality. Boeing engineers incorporate stealth technology by using coatings and treatments which reduce radar reflections and thermal loads of the fuselage. Note that the US government limits the use of specific materials in aircrafts to be sold outside the US - this may vary from customer to customer according to actual political considerations.
According to Boeing, the special radar absorbing coatings offer an equivalent amount of front-aspect stealth that modern 5th generation fighters. This sounds nice, but not too specific. Boeing remains a bit unclear in this topic to say the least: in 2009 they claimed to have the same amount of stealth that Lockheed Martin's F-35 JSF offers, but in 2010 they softened their statement somewhat by saying that the Silent Eagle offers the same level of front-aspect stealth than the "international release version" of the JSF, but Lockheed Martin officials denied even the very existence of such international release standards.
Anyhow it seems to be clear, that the Silent Eagle's RCS reduction package is effective against X-band radars, that is airborne radar systems - emphasizing the fact that it's an " A/A only" stealth, which is not optimized against ground based radars.
Of course for true stealth only coatings and external treatments are not enough, "real" stealth aircraft designs use special internal structures developed for absorbing and dissipating incoming radar energy. To what extent Boeing changed the Strike Eagle's internal structure is not known, however due to the relative shortness of development time and because of the fact that a reotrofit kit (containing CWB equipped fuel tanks, DEWS and coating) is offered by Boeing for existing Strike Eagle aircraft, we conclude that no major internal structure changes (if any) have been made to the Silent Eagle.
Engines: Boeing can equip the F-15SE both with General Electric made F-110- GE-129 engines and the 'traditional' Pratt&Whitney F100-PW-220 series engines. Besides technical and performance differences, the GE engine can immediately be recognized by its different jet exhaust nacelles.
A radar blocker for engine inlets is available, depending on how much RCS reduction a potential international customer requires (and how much is allowed by the US government for export). An engine inlet radar blocker is a special air ducting which prevents direct LOS of the engine turbine blades, one of the most radar reflective surfaces of the aircraft from frontal aspects. Note that radar blockers interfere with engine inlet airflow hence decrease engine performance to some extent.
Speaking about engines, one key feature for true stealth is to significantly lower the engines' heat signature, something which the F-22 Raptor has done already. So far Boeing has no plans for reducing engine heat signature for the Silent Eagle.
Digital Flight Control System: The Silent Eagle features a digital flight control system ( DFCS), which reduces aircraft weight and improves reliability and maneuverability. By the use of DFCS the Silent Eagle becomes a true fly-by-wire jet, instead of being "semi" fly-by-wire as currently the Strike Eagle is.
Cockpit: Not much is known about the planned cockpit arrangement of the Silent Eagle other than a graphical image provided by Boeing. According to this graphics, the cockpit retains the well-proven Strike Eagle approach, that is 3 multi-purpose LCD displays for the pilot and 4 similar displays for the WSO. The UFC changes to a flat touch panel type digital display, while the HUD seems to be even bigger than the one found in the Strike Eagle.
Not strictly a cockpit issue, but JHMCS will of course be available for future Silent Eagle pilots.
Countermeasure Dispensers: The Silent Eagle will feature extra CMD's on the underside of the two tailbooms, containing 2 CMD's each. Adding this to the 8 CMD's mounted on the underside of the fuselage, gives a total of 12 CMD's, increasing onboard expendable countermeasure capacity by 50% compared to the Strike Eagle. Note that these assemblies are called DSA's, which stands for Dispenser/Sequencer Assembly.
Radar: It is one of the most important differences between the F-15E and F-15SE models. The F-15SE is equipped with Raytheon's APG-82 radar, the newest of their ultramodern AESA line. Raytheon's AESA radar versions got a bit confusing in the last years. APG-63(V)4 is yet another improved version of the APG(V)3 (the same radar that can be found in the F-15K Slam Eagle or in the F-15SG), but got a new designation: it's officially called APG-82, mainly because USAF has selected this radar for its F-15E Strike Eagle radar modernisation programme. This new radar combines the F/A-18E/F Super Hornet's APG-79 forward antenna with a newly developed backend processor unit derived from the APG-63(V)3. Its designation number is 1 greater than APG-81, the JSF's intended AESA radar unit developed by Northrop Grumman, which might come handy for Raytheon for marketing purposes.
Boeing plans to utilize the radar's capabilities fully, even slightly at the expense of stealth. For this reason, the radar would remain canted slightly forward rather than tilted back (see graphics above), preserving coverage and range at the expense of head-on RCS.
Electronic Warfare: Instead of the TEWS used in the Strike Eagle, the F-15SE features a digital electronic warfare system (developed by BAE Systems), dubbed as DEWS. DEWS was developed by leveraging F-22 and F-35 EW program results and replaces 4 legacy systems of the Strike Eagle. It is fully digital (hence its name) and works in close integration with wideband RF systems, including the APG-82 AESA radar, giving the jet a very sharp edge in the electronic warfare arena.
DEWS offers full quadrant detection and response control, containing aft receiving antennas on top of the tails, aft RF transmitters and antennas built in the tailbooms, forward RF transmitters and antennas built in the leading edge of the wing roots, forward receiving antennas built in the wingtips and a low band Rx knife antenna placed on the underbelly of the jet below the cockpit.
DEWS includes a digital RWR, digital jamming transmitter, ICS and an interference cancellation system. According to Boeing, the system enables the Silent Eagle to jam enemy radars while its own radar and RWR continues to operate.
Sensor Pack: The aircraft will be fitted with a network-enabled integrated sensor system, where individual sensor elements work closely connected to each other, presenting situational information in a unified way to the aircrew on the SIT display. This "sensor fusion" approach greatly increases aircrew SA and reduces aircrew workload - they simply don't need to know what sensor a specific information comes from, their job is to process the information and act accordingly.
Elements of the sensor pack are the APG-82 AESA radar (note that the above graphics made by Boeing in 2009 mentions APG-63(V)3, but things have changed since then), a navigation pod, a targeting pod, a recce/radar pod, an IRST system and a threat warning ECM system. Link-16 FDL capability will also be included, thus the aircraft can rely on information gathered by sources other than its own sensors - even when the aircraft's own sensors are put in "silent" (i.e. not emitting detectable energy) mode of operation.
Support: There are numerous maintainability improvements which cannot be seen from the outside, yet they are very important for any air force that is planning to operate the Silent Eagle. The F-15SE features 60% less LRU's and over 200% throughput and memory growth reserve.
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