F-35 vs F-15SE: South Korea's F-X III Competition - Part III The Silent Eagle

F-35 vs F-15SE: South Korea's F-X III Competition - Part II The Silent Eagle

Author's Note: Sorry for the delay in publishing but as mentioned in the update, unexpected problems came up during research. Lockheed Martin has an IRST system they simply call "IRST". Seriously Lockheed? This made it difficult to discern at times whether or not certain systems contained the Lockeed Martin IRST or some other IRST system in general.  To make matters worse, the DSCA lists 60 AN/AAS-42 Infrared Search and Track systems as part of the requested F-15SE package (if chosen). The AN/AAS-42 Infrared Search and Track system was an IRST featured on the F-14D more than 20 years ago and it took me some time to figure out the DSCA was actually referring to Lockheed Martin's IRST which was developed from the original AN/AAS-42 Infrared Search and Track system. On an unrelated note, the F-X III was suspended according to Defense Industry Daily (see July 8th entry on DID) as none of the bids managed to lower their offer to the $7.3 billion limit. The series will still continue as eventually South Korea will reevaluate the competition by either cutting the number of aircraft down from 60 or increasing the budget limit up from $7.3 billion. 

1. Maneuverability 
2. Radar
3. IRST
4. DEWS
5. JHMCS II

Maneuverability 

Despite the fact that the original F-15 airframe was designed 40 years ago, the eagle airframe continues to provide solid maneuverability performance. However, the new Flankers variants such as the Su-35BM and Su-30MK2 are starting to surpass the original eagle in some maneuverability metrics such as sustained radius turn. The silent eagle's aerodynamic performance is superior to the original eagle due to its much higher thrust engines. The F-15SE will be assessed in the following maneuverability criteria: thrust to weight ratio, wing-loading, sustained turn ability, and instantaneous turn ability.

In a clean configuration, the strike eagle's maneuverability is very impressive. The silent eagle is equipped with two General Electric F110-GE-129 engines capable of 29,400 lbf of thrust (F100 PW-229 with 29,100 lb thrust each in US strike eagle) vs. the two 23,450 lbf Pratt & Whitney F-100-PW-220 engines in the standard F-15C.

"Incidentally, a clean--with no conformal tanks mounted-- F-15E powered by twin Pratt and Whitney F100 PW-229 engines is a stellar performer according to USAF and Boeing pilots who have flown in that configuration. One Boeing pilot says that with the 29, 100lbs 229 motors, the clean jet climbs like a rocket--potentially giving even the F-22 Raptor a run for its money. It will also easily cruise supersonically. 'It's a monster,' another pilot says."  -Dave Majumdar, 2012

In a stealth air to air configuration, the silent eagle has an impressive thrust to weight ratio of  1.27 (its slightly higher as the conformal fuel tanks are partially drained to allow for weapons storage by an unknown amount).

31,700 lb airframe
13,123 lb of internal fuel
1,340 lb weight of four AIM-120C-7 missiles
281 lbs for 500 PGU-28 20mm cannon rounds
46,444 Total Weight
29,400 lbf Thrust X 2 = 58,800lbf -> 58,800/46,444 = 1.2660408
1.2660408 -> 1.27

Graphic 1: Thrust to weight ratios of high performance fighter aircraft with 100% internal fuel and standard combat air to air payload configuration (including weight of cannon ammunition). 

When compared to other high end fighter aircraft, the F-15SE's thrust to weight ratio is second only to the Raptor (Although, the Raptor can carry twice as many missiles internally). A high thrust to weight ratio generally indicates greater climb rate, faster acceleration, and higher maximum speed capability (Shaw, pg. 141). The original strike eagle is one of the fastest aircraft in the USAF and can reach a maximum top speed of mach 2.5.

Low wing loading generally indicates "good instantaneous turn performance, slow minimum speed, and a tight sustained turn radius." (Shaw, pg. 141). The conventional eagle has a sustained turn radius of about 15° and an instantaneous turn rate of 21°. The new generation of Russian Flankers, such as the Su-30MK2 are capable of 21-23° sustained turns while the Raptor can sustain a 28° per second turn rate (Source 2). Although the wing-loading figures of the strike eagle (and conventional eagle) are excellent, other factors such as wing efficiency (in regards to lift) affect turn sustained ability and can explain the disparity between maximum sustained turn rate and low-wing loading.

Overall, the silent eagle preforms exceptionally well in the vertical aspects of maneuverability while providing an average performance in horizontal metrics.

+exceptional T/W ratio
+excellent maximum speed
+ high rate of climb
+/- average sustained & instantaneous turn rate
+ solid acceleration performance

Avionics 

F-15E upgrade road map provided by Boeing. 

The base Strike Eagle's core avionics package underwent numerous upgrades as a result of foreign  contracts. For example, international customers have become increasingly interested in acquiring the new generation of active electronically scanned array (AESA) radars for their fighter aircraft. The first strike eagle to receive an AESA was the F-15SG in 2005 with the AN/APG-63(V)3. Boeing has not indicated which radar system will be utilized in the silent eagle but the most likely candidates are the APG-63(V)3 and APG-82(V)1. The APG-63(V)3 represents a major improvement over the original APG-70 electronically scanned array (ESA) in terms of both performance and reliability.

APG-63(V)3:

"This is the most capable radar in a fighter aircraft in the world. The system is as advanced as that of the Air Force's most advanced fighter -- the F-22 Raptor. The AESA is all-electronic based with no moving parts on the radar system itself, allowing everything to be electronically steered. The system allows the F-15 to engage targets better and with greater reliability. The AN/APG-63(V)3 AESA radar provides powerful, adaptable radar technology, proven performance, and tactical flexibility that F-15 pilots can rely on. The (V)3 is essentially an updated APG-79 front-end (antenna and power supply) and APG-63(V)1 hardware back-end. For the F-15E, the antenna size was increased to 0.9 m (36 in.) diam, and improved tile T/R modules with a greater mean time between overhaul are used." - Global Security, 2011

APG-81(V)1 Radar

The number of transmit receiver modules (TR) featured within an AESA is generally indicative of its maximum detection range; the highest performance AESA radars feature 1,500 TR modules. The strike eagle's spacious nose cone allows it to accommodate large 1,5000 element arrays such as the APG-63(V)3 and APG-82(V)1. Either system will greatly enhance the F-15SE's ability to detect low observable targets at a distance. The APG-82(V)1 is the more modern of the two systems and delivers comparable performance at a lower cost.

"The APG-82(V)1 optimizes the F-15E’s multirole mission capability. In addition to its extended range and improved multi-target track and precision engagement capabilities, the APG-82(V)1 offers a more than twentyfold improvement in system reliability over the legacy F-15E APG-70 radar. The new radar works as a plug-in-play system with newer, easily replaceable parts...By leveraging combat-proven technologies—the APG-79 and APG-63(V)3 AESA radars flying on the F/A-18E/F, the EA-18G and the F-15C platforms—Raytheon delivers a low-risk, cost-effective and superior situational awareness and attack radar to modernize the Strike Eagle." - Global Security, 2011 

Tiger Eyes system far left. The Tiger Eyes system is comprised of two pods: the Lockheed Martin IRST (top pod) and a standard LANTIRN pod (bottom pod). 

IRST

Infrared search and track (IRST) systems are becoming increasingly standard on modern fighter aircraft. Modern IRST systems can warn the pilot of incoming enemy aircraft and missiles in addition to providing targeting information to heat seeking missiles. Although the strike eagle does not feature an IRST within the airframe itself, specialized IRST pods have been developed for the strike eagle. Lockheed Martin first supplied the Tiger Eyes system for South Korea's F-15K purchase and subsequently provided pods for Singapore's  F-15SG order in 2005. The proposed direct commercial sale agreement for silent eagle requests 60 AN/AAS-42 Infrared Search and Track systems. Its important to note that the Super Tomcat was fitted with an IRST system with the same designation name more than 20 years ago. The DSCA is likely referring to the IRST system which Lockheed Martin simply refers to as "IRST" in its marketing materials not the original Super Tomcat mounted system.

"The IRST system enhances the capabilities of the F-14D AN/AAS-42 IRST that had been operational aboard U.S. aircraft carriers and accumulated over 200,000 flight hours." - Lockheed Martin, 2013

Lockheed Martin's IRST system

"The advanced electro-optical suite, an evolution of combat-proven LANTIRN and U.S. Navy IRST technology, will enable pilots to fly and fight day or night, and in adverse weather...IRST, a pylon-mounted version similar to the U.S. Navy F-14 IRST system, allows pilots to detect and assess long-range airborne threats. A passive long-wave infrared sensor system searches for and detects heat sources within its field of view. The system gives the aircrew unprecedented on-board situational awareness while significantly enhancing the engagement range of modern high-performance weapons."  - Lockheed Martin, 2012

Although IRST pods are a convenient and relatively low cost solution to give legacy aircraft IRST capabilities, IRST pods are not preferred to internally mounted IRST or EOTS systems. Depending upon the type of IRST pod, a significant amount of drag can result from its use. For example, the US Navy plans to modify 200 cumbersome 480 gallon centerline fuel tanks into 330 gallon fuel tanks with a Lockheed Martin IRST system attached to the front. Furthermore, IRST pods would make an otherwise stealthy aircraft detectable. If the silent eagle needs to operate in an high threat environment, it must forego IRST capabilities.

Digital Electronic Warfare Suite (DEWS) 

Some of the most significant improvements made to the silent eagle were upgrading its obsolete electronic warfare suite. Strike eagles operated by the USAF still use the Tactical Electronic Warfare System (TEWS) which is comprised three systems designed in the 1980s: ALR-56C radar warning receiver,  ALE-45 countermeasures dispenser, and ALQ-135 jammer. 

"BAE confirms that the DEWS package is derived from the EW suite designed for the Lockheed Martin F-22 Raptor and F-35 Joint Strike Fighter, using a modular software architecture system called Barracuda. A key feature of the system is an interleaving mode that allows the pilot to continue jamming while simultaneously operating the radar and RWR."

DEWS will greatly enhance the survivability of the silent eagle against both ground and air threats. The APG-63(V)3 also compliments DEWS by providing further electronic warfare assistance such as jamming of enemy radars. In general, a competent electronic warfare suite is vital to providing adequate missile warning, passive detection via RWR,jamming, and CM deployment to defeat enemy missiles. 

JHCMS II 

The original joint helmet mounted cueing system (JHMCS) is among the successful HMD systems on the market with over 6,000 units delivered to 26 customers for the F-16, F-15, and F/A-18. The United States was behind the Soviet Union in terms of deploying operational HMD's to fighter pilots; the Soviets equipped their Mig-29's and Su-27 pilots with Shchel-3UM HMD systems by the end of the Cold War. The Shchel-3UM  enabled 45° off bore sight archer missile shots at visual range. JHMCS was the very delayed response to the Shchel-3UM HMD and was first fielded in 2003.

"Digital JHMCS and JHMCS II are highly accurate pilot information systems that provides pilots with "first look, first shot" high off-boresight weapons engagement capability and situational awareness. Both systems enable the pilot to accurately direct (cue) onboard weapons and sensors against enemy targets while performing high-G aircraft maneuvers. The pilot simply points his/her head at the target and weapons will be directed to where the pilot is looking for both airborne and ground targets. As a cueing system, JHMCS II is a two way interface where sensors aboard the aircraft can cue the pilot to potential targets, or the pilot can cue the weapons and sensor systems to areas of interest. Critical information and symbology including targeting cues and aircraft performance parameters are graphically displayed directly on the pilot's visor." - Elbit Systems USA, 2013

JHMCS II builds upon the already impressive capabilities of JHMCS I and adds the following (as listed by Elbit USA): 

• Digital image source replaces JHMCS Cathode Ray Tube (CRT)
• No high voltage requirements 
• Reduced routine maintenance
• Improved center of gravity provides greater pilot comfort, especially with NVGs
• No visor trimming
• Helmet borne electronics
• Virtual HUD option
• Embedded virtual training compatible
• Pilot Health Monitoring including hypoxia and G-LOC detection and warning
• Early pilot warning and aircraft recovery option

PART IV The Silent Eagle - The F-15SE's lethality against 4.5 generation and 5th generation threats in addition to IADS penetration capabilities 

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