Radar Refits: F-15s Looking for the AESA Edge

Before: APG-63 MSA
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Most F-15C Eagle air superiority fighters use APG-63 radars, passive arrays mounted on a movable swashplate. While upgrades over the years have improved them, a new generation of radar technologies has appeared. With cruise missile defense rising in importance, and longer-range detection desired, upgrades are necessary. That requires new radars, using AESA technologies that dramatically improve range, while reducing maintenance. The USAF has also discussed a retrofit set that would turn the F-15C Eagles into multi-role fighters, and a next-generation AESA radar would be part of that, too. Meanwhile, they’ve started a program to upgrade select F-15C units with AESA radars, as an air-air improvement.

Those F-15C units will now be joined by the USAF’s entire 2-seat, multi-role F-15E Strike Eagle fleet, whose future AESA radar has received some improvements, and a new designation.

The F-15’s Radars

F-15: Legacy Radars

APG-63v2 AESA
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The USAF’s F-15C air superiority fighters have traditionally used APG-63 pulse-Doppler radars, passive arrays that use a movable mounting to create their coverage area. Almost 1,000 APG-63s had been delivered when production ended in 1986, and about 700 are still operational in F-15As, Bs, and early model Cs and Ds operated by the US military and the air forces of Israel, Japan, and Saudi Arabia.

The multi-mode AN/APG-70 is a 1980s derivative of the APG-63 that adds air-ground modes and maintainability improvements. Gate array technology adds air-ground modes, and improves air-air effectiveness. The APG-70 is employed on late model F-15C/D Eagles, all F-15E Strike Eagle aircraft, and on the Israeli F-15I and Saudi F15S Strike Eagle variants. Beyond the F-15, a variant of the APG-70 radar called the AN/APQ-180 adds a modified planar array, an upgraded signal processor, and several enhanced air-to-ground modes, for use on the USA’s AC-130U Specter gunship aircraft.

The AN/APG-63v1 is a 1990s-era reliability/ maintainability upgrade that adds modern back-end hardware, and enhances air-air and air-ground capabilities. It is NOT an AESA radar, but could be refitted with an AESA front end. Raytheon has received 5 production orders to deliver 161 APG-63v1 radar systems plus spares to the US Air Force, and the first units entered service in March 2001. Up to 170 may be ordered. Another 60+ radar systems and spares will be delivered to Korea for their F-15K. Some Japanese F-15Js have been fitted with a license-produced Mitsubishi Electric (Melco) APG-63v1, as a first step toward their own general fleet upgrade.

Future 15s: AESA Radars

AN/APG-63v3 AESA
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In contrast, Active Electronically-Scanned Array (AESA) radars are made of hundreds or thousands of small transmitter/receiver (TR) elements. Moving parts are eliminated; instead, subsets of their array elements are used to focus on each task very quickly and precisely, without having to move the elements physically, and with little signal “leakage” outside of its focused beams. This makes them more reliable, more powerful, and able to operate in multiple modes at once. New radars may also correct a known air-air weakness in previous radars that can reputedly be exploited by aircraft like Russia’s SU-30 family, though other reports claim that existing radars have closed that hole.

There’s even a maintenance advantage to AESA technology. A partial failure in previous radars renders them unfit for use, but AESA radars only suffer a slight performance drop if some of their thousands of TR modules fail. The fighter can still fly, enjoying all of the radar’s simul-mode, range, focusing, low “leakage,” and communications benefits. In most cases, the fix isn’t even deemed to be worth the time.

AESA radars have taken a while to enter widespread service on fighter aircraft because the cost of each array had to come down to an affordable level, but once that happened, their advantages become compelling. Raytheon has several variants on offer:

AN/APG-63v2. The world’s first AESA radar system to be operationally deployed in a fighter aircraft, entering service with the F-15Cs at Elmendorf Air Force Base, Alaska in December 2000. At present, 18 operational F-15Cs fly with the APG-63v2 radar, and a 19th F-15C has been equipped with the APG-63v3 for testing purposes. Current plans call for up to 48 more APG-63v3-equipped F-15C/Ds to join them, but some options under discussion could grow that number.

Raytheon’s AESAs
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APG-63v3. Combines APG-63v2 AESA software with the hardware advances that went into the F/A-18 E/F Super Hornet Block II’s AN/APG-79 AESA radar. Whereas the AP-63v2 AESA had a square profile, the APG-63v3 can be recognized by the rounder shape of its array. It uses lighter and more advanced AESA technologies that include a tile array arrangement, and a new processor.

The ‘v3’ is being fitted to F-15C aircraft as an extension of earlier air-air upgrades, and a variant was picked to equip the USAF’s F-15E Radar Modernization Program (RMP), beating Northrop Grumman’s offer of the AN/APG-77v1 radar that equips the USAF’s F-22A Block 20 Raptors. On the export front, Singapore’s new F-15SG Strike Eagles and Saudi Arabia’s F-15SAs will use the APG-63v3 radar. Japan has reportedly expressed interest in it as a fleet upgrade possibility for its F-15J (F-15 C/D equivalents), and it has been offered to South Korea as part of Boeing’s F-XIII bid of its stealth-enhanced F-15SE Silent Eagle.

AN/APG-82. The F-15E RMP program’s fit-out would add a few refinements to the ‘v3,’ and receive a new designation: AN/APG-82v1. New Radio Frequency Tunable Filters (RFTF) will enable the aircraft’s radar and Electronic Warfare System to function at the same time, and an improved Environmental Cooling System (ECS) will improve liquid cooling capacity by 250%. Other back-end changes will include a new wideband radome, a new radio frequency tunable filter, updates to the F-15E’s core Operational Flight Program software and Electronic Warfare software, and wiring changes.

Best of all, instead of the APG-63v3’s large LRU “black box” units that must be sent to a maintenance depot for diagnosis and service, the APG-82 radar borrows from the Super Hornet’s APG-79 and uses advanced internal diagnostics, plus smaller LRM “blades” that can be swapped out in the field based on the diagnostic reports.

In future, the APG-82’s commonality with the APG-79 offers another benefit: new radar capabilities can be transferred from one radar to the other via software upgrades. The USAF would still have to conduct full testing of the upgrades, but this level of commonality does save a lot of money and time.

There’s also a flip side to this commonality. The APG-79 has had long-running problems with software instability and poor performance of Built-In-Test (BIT) functions. Those problems have remained unfixed for over 7 years, and have now migrated into the APG-82 as well. If the USAF wants to make full use of the new radars, it may have to pay to fix the Navy’s problem.

The APG-82 is currently in the System Development and Demonstration phase, though low-rate production has begun. Flight tests began in 2010, and Boeing expects to achieve Initial Operational Capability during FY 2014.

Contracts & Key Events

PACAF F-15C
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November 2/15: The Air Force has furthered its F-15 radar upgrade program by awarding a $281.7 million contract to Boeing for the Combined (V)3 and Radar Modernization Program, with this award covering the procurement of 17 (V)3 and 29 Radar Modernization Program radar systems. The Air Force has been looking to modernize its F-15 fleet by adding Active Electronically Scanned Array (AESA) radar systems capable of enhancing the aircraft’s air-to-air capabilities. The Air Force began by upgrading various systems, including radar and other sensors, on older F-15C/D models in March last year.

July 16/14: In use. The first 389th Fighter Squadron F-15E Strike Eagle at Mountain Home AFB, ID, has begun flying with the new APG-82v1 radar, clocking 11 flight hours so far. The article says that the process takes 2-3 months, and says that the tentative plan is to complete RMP “for 47 aircraft from the 389th FS and 391st Fighter Squadron by 2017.” The maintenance angle was put this way:

“The old radar system is hydraulic, has moving parts and requires three maintainers to perform repairs after every 30 flight hours,” said Master Sgt. Jennifer Schildgen, 366th Fighter Wing avionics manager. “The new radar system is a beam scan, doesn’t have any moving parts and is projected to only require one maintainer to perform repairs after more than 2,000 flight hours.”

Sources: USAF, “F-15E takes first flight with new radar system”.

Jan 28/14: DOT&E Testing Report. The Pentagon releases the FY 2013 Annual Report from its Office of the Director, Operational Test & Evaluation (DOT&E). The APG-82 RMP was tested through IOT&E from March – September 2013, and the verdict is mixed. On one hand, it’s deemed operationally effective, with particular gains in air-to-air missions, and better reliability and maintainability than the old APG-70. Air-to-ground performance is only “comparable”, however, with “some improvements in target location accuracy”. More bad news stems from its APG-79 lineage:

“Does not meet the user’s software stability requirement of 30 hours Mean Time Between Software Anomaly (MTBSA). The inability to meet this requirement diminishes the effect of the overall mission capability improvements…. The F-15E RMP system software architecture shares significant commonality with that of the F/A 18 APG-79, and the APG-79 has yet to resolve the software stability deficiencies identified in its 2007 IOT&E. Therefore, it is unlikely that the Air Force will achieve the stability necessary to achieve the full potential operational capability of the F-15E RMP system unless significant effort and resources are directed towards improved software stability.”

The Air Force plans to make their Full-Rate Production decision in March 2014.

Aug 30/13: Support. Raytheon in El Segundo, CA receives an estimated $11.5 million cost-plus fixed-fee requirements contract, as part of the F-15 Aircraft Reliability & Maintainability Engineering Services program. They’ll provide engineering services and supply chain management to support F-15 radars: the AN/APG-63 family; the AN/APG-70 and its and the AN/APG-180 derivative on AC-130U gunships; and the new AN/APG-82v1.

Work will be performed at El Segundo, CA, will run until Sept 1/18, and includes 3% worth of classified and unclassified Foreign Military Sales (FMS) in support of Israel, Saudi Arabia, South Korea, Japan, and Singapore. Funds will be committed as necessary by the USAF Systems Center/PZA Contracting Division at Robins AFB, GA (FA8538-13-D-0014).

Aug 28/13: South Korea. Aviation Week reports that Boeing offered South Korea the APG-82v1 AESA radar as part of its F-15SE bid. That is a step up from the APG-63v3 AESA in Singapore’s F-15SGs and Saudi Arabia’s forthcoming F-15SAs, and in Boeing’s original F-15SE bid as well.

If South Korea signs a contract with Boeing, they would become the APG-82’s first export customer. As it turns out, the F-15SE does win the competition, until the generals throw out the competition and declare the F-35A to be the ROKAF’s sole-source choice. Sources: Aviation Week, “Boeing Mulling F-15 Plans Beyond Silent Eagle”.

F-15E w. APG-82v1
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Sept 26/12: Extra Eagle Extensions? Boeing’s F-15 mission systems director Brad Jones places the F-15 fleets’ AESA radar upgrades in a broader context. With so few F-22As in service, and budget crunches coming, the USAF believes that it has no choice but to continue flying F-15s, which makes their future capabilities very important. First, Boeing is studying structural improvements and certification that could extend the F-15A-D fleet’s lifetime to 18,000 flight hours, and the F-15 Strike Eagles to 32,000 flight hours.

The Advanced Display/Core Processor II (ADCP II) program will replace all the computers in USAF F-15Es with modern mission computers, gigabit ethernet, and fiber channel connections. A Milestone B decision is scheduled for November 2012. ADCP II would help F-15s take more advantage of their AESA radars, especially for advanced modes like jamming.

The Advanced Cockpit System (ACS) option would replace 23 existing instruments with a 22″ display, a low-profile head-up display, a reference standby display and a low-profile engine fuel hydraulics display. Elbit is already a confirmed partner, and ACS has been submitted with the stealth-enhanced F-15SE for the Korean F-X-III fighter competition.

Finally, a proposed new Digital Electronic Warfare System (DEWS) would replace many of the planes ECM gear, providing the advantages of Digital Radio Frequency Memory signal replication and re-transmission, along with more than 200% throughput and memory growth reserve compared to existing options. DEWS has also been submitted with the stealth-enhanced F-15SE for the Korean F-X-III fighter competition. Defense Tech.

Aug 29/12: Support. Boeing announces an $85 million Performance-Based Logistics (PBL) contract for continued support of U.S. Air Force F-15 mechanically scanned and Active Electronically Scanned Array (AESA) radars. As the number of F-15 AESAs grows, a unified support framework becomes more and more important.

The new contract replaces 3 previous support contracts with one overarching agreement, and integrates a Boeing Contractor Logistics Support team into assigned Air Force wings. These people are considered active-duty civilians, and will be deployable worldwide. Boeing.

AN/APG-63v3 AESA
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Sept 13/10: APG-63v3. Raytheon announces that the first APG-63v3 radar is now deemed to be officially installed on a USAF F-15C air superiority fighter, following a series of successful flight tests.

Combat Aircraft’s August 2010 issue says that the 71st Fighter Squadron at Langley, VA has had 8 of its F-15Cs equipped with the new radar. The USAF will send 4 to Kadena AB, Japan and the other 4 to Nellis AFB, NV. The Nellis AFB aircraft will be used for weapons instruction and training, and test support.

June 10/10: APG-82. Boeing receives the first APG-82v1 radar test set from Raytheon. The radar test set, which has successfully completed Acceptance Test Procedures, will undergo further tests at Boeing’s Electronic Systems Integration Lab in St. Louis, MO before being integrated into an F-15E.

Raytheon is producing 5 AESA radar test units as part of the Engineering and Manufacturing Development phase of the program, and will support Boeing’s integration of AESA into the F-15E at Boeing’s St. Louis facilities. Testing and evaluation will follow. Boeing.

April 14/10: F-15C role expands. Aviation Week reports that AESA-equipped USAF F-15Cs will be forced to shoulder about 50% of the “air dominance” burden once allocated to the F-22A:

“Each fighter type will shoulder 50% of the air dominance mission… “Our objective is to fly in front [of any strike force] with the F-22s, and have the persistence [because of larger fuel loads] to stay there while the [stealthy fighters] are conducting their LO attack,” says Maj. Todd Giggy, the wing’s chief of weapons and tactics… The Florida, Louisiana and Oregon ANG will field the first 48 V3 radar-equipped F-15Cs. Massachusetts and Montana ANG units will follow so that the East, West and Gulf coasts have a cruise missile defense capability.”

March 31/10: Sub-contractors. A new radar also needs a new radome nose cone. General Dynamics Armament and Technical Products announces that it has delivered its first F-15 wideband nose radome to The Boeing Company in support of the F-15 Radar Modernization Program (RMP). Delivery of the AN/APG-82v1’s companion nosecone falls under a system development and demonstration (SDD) contract that was formally awarded in October 2008. See also May 2/08 entry, noting GD ATP’s earlier selection as the preferred partner.

Benefits of the new radome include superior electrical performance over a wide frequency range, low weight, low part count, and the ability to perform in high heat and stress environment. The radome also includes the installation and integration of an instrument landing system antenna.

Nov 6/09: Sub-contractors. Giga-tronics Inc.’s Microsource subsidiary announces that its new Radio Frequency Tunable Filters (RFTF) will be part of the AN/APG-82v1. RFTFs allow the radar and electronic warfare system to function at the same time, by minimizing interference. Microsource Inc. in Santa Rosa, CA developed the modified RFTF specifically for the F-15 RMP program during a 9-month collaborative process, leveraging its previous RFTF work with Boeing and Raytheon for the Super Hornet‘s AN/APG-79 AESA radar.

F-15E, Afghanistan
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Oct 30/08: In November 2007, Boeing picked Raytheon’s APG-63v3 AESA radar to modernize its F-15E Strike Eagles. Now Boeing announces a $238 million System Development and Demonstration (SDD) contract from the USAF, which begins to finance that work. During the SDD phase, Raytheon will produce developmental and flight-test radar units, while Boeing ensures that the new radars work with the F-15E’s full array of electronics and systems. A sub-contract to Raytheon can be expected to follow shortly, and work on the SDD phase is expected to finish in September 2012.

Initial operational capability (IOC) for the upgraded F-5Es is expected in FY 2014, with the fielding of 12 operational aircraft. Those radars and aircraft integration work will be part of a separate low-rate initial production (LRIP) contract, not the SDD phase. Boeing release.

F-15E RMP SDD

F-15C over DC
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May 2/08: Sub-contractors. General Dynamics Armament and Technical Products announces a sub-contract from Boeing to develop the next generation of wideband radomes for the F-15 Radar Modernization Program. The System Design & Development contract scope included radome design, material strength and environmental testing, environmental and structural qualification, tool design, fabrication, assembly, and repair-methods development.

Production and program management is being performed at General Dynamics’ advanced materials facility in Marion, VA, with 10 radomes to be built by April 2011, as part of the SDD phase. Boeing has picked a winning radar design for the program, but the formal USAF radar contract wouldn’t be signed until October 2008, with 1st delivery of a radome to Boeing taking place in March 2010.

March 17/08: APG-63v3 order. Boeing announces a $130 million U.S. Air Force contract to upgrade 16 Air Force and Air National Guard F-15C Eagles with the APG-63v3 AESA radar, bringing the total to 24. Raytheon adds that its contracts with Boeing are worth just in excess of $89.5 million, and authorize production of 8 APG-63v3 AESA radar systems for the US Air National Guard plus 8 systems for the Air Force.

See also the Oct 9/07 entry, which describes the delivery of 8 radars under an earlier order. Like the previous September 2007 contract, this order includes initial spares and aircraft support. Boeing release | Raytheon release.

The AESA upgrade program continues, despite concerns that America’s F-15A-D fleet appears to have have more fatigue issues, and possibly less service life, than previously thought. Careful selection of airframes to upgrade may help to mitigate this risk, which the F-15E fleet does not appear to share.

F-15C fires AMRAAM
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Oct 9/07: Boeing announces a $70 million contract to begin upgrading U.S. Air Force and Air National Guard F-15C Eagles with the APG-63(V)3 Active Electronically Scanned Array (AESA) radar. The upgrades will begin in first quarter 2009. Raytheon, meanwhile, describes a $52.2 million Boeing subcontract to deliver 6 APG-63v3 AESA systems to Boeing, a 7th spare to the Air National Guard, and an 8th system to the U.S. Air Force. Boeing release | Raytheon release.

A significant part of this contract also includes production start-up costs, as well as manufacturing equipment and other spares. Raytheon expects to deliver 6 or more AN/APG-63v3 radars per year to the Air National Guard in coming years, for a planned total of at least 48. The new AESA radars are the latest addition to planned upgrades to some of the USA’s F-15Cs, which have included a fighter-to-fighter data link, GPS navigation, and the Joint Helmet Mounted Cueing System (JHMCS) helmet sight.

F-15C upgrade begins

Sept 27/06: APG-63v3. Raytheon announces that its APG-63v3 AESA radar for the F-15 has been delivered to the US Air Force for the final phase of developmental testing. This testing entails multiple flight tests to ensure the AESA radar system meets all performance specifications and requirements. Raytheon feature.

Aug 7/06: APG-63v3/ Raytheon announces that it has delivered the AN/APG-63v3 radar to Boeing in late June 2006, ahead of schedule, following flight tests to verify its air-air capabilities. Completion work on the antenna and final verification of the system in Raytheon’s Radar System Integration Lab, prior to flight test, were achieved in a record 7 weeks when 6-to-12 months as is usually the norm. At least 10 more flights, intended to further demonstrate enhanced air-to-air capability, are expected to begin at Eglin Air Force Base, FL in fall 2006. Raytheon release.

Sept 20/05: Competition. Flight International reports that plans to upgrade up to 150 of the USA’s multi-role F-15E Strike Eagles will feature a competition between Raytheon’s APG-63v3 radar, and the Northrop Grumman AN/APG-77 radar that equips the F-22 Raptor. As of October 2007, however, no decision has been made regarding this upgrade project. See “USAF wants competition for F-15E Strike Eagle radar upgrade.”

Additional Readings

• Raytheon – Raytheon’s Revolutionary AESA Technology

• Raytheon – AN APG-63(V)3 AESA Radar . See also PDF brochure.

• Raytheon – Legacy Radar. Refers to APG-63v1/v2.

• Raytheon – AN/APG-70 Radar

• USAF – F-15 Eagle

• USAF – F-15E Strike Eagle

• Boeing – F-15E Strike Eagle

• GlobalSecurity – F-15 Eagle. Includes information re: US and foreign variants.

• Aviation Week, via WayBack (Aug 5/07) – Japan Chooses An Offense. Covers Japan’s requests for F-22A Raptors, and also goes into Japanese plans to upgrade its F-15Js with improved radars. Some APG-63v1s have been fitted, but Japan may be interested in converting its fleet to APG-63v3 AESAs as an interim gap-filler and a cruise missile defense supplement to the Raptors if/when they arrive.

• DefenseTech, via WayBack (April 20/06) – Eagles Forever. Discusses the possibility of F-15C multi-role upgrades.

• Aviation Week (April 12/06) – Moseley Considers Options For Future Force Reductions [dead link]. “A roadmap of options for the remaining F-15Cs and Strike Eagles is nearly complete. That document is expected to outline needed upgrades, such as active electronically scanned array (AESA) radars, for some F-15Cs that would allow them to detect cruise missiles. Raytheon officials have been pitching upgrades to the existing radars as well as new systems for the F-15…”

• Flight International, via WayBack (Sept 20/05) – USAF wants competition for F-15E Strike Eagle radar upgrade

• DID (Jan 25/06) – Israel Kicks Off Program to Improve Its F-16s and F-15s. No AESA radars scheduled at this point, but they do in tend to make their F-15Cs into multi-role fighters.

• Aviation Week (March 18/04) – Roche: F/A-22’s Readiness For Key Testing Phase Is “Iffy” [dead link]. Includes a section covering the F-15C “Golden Eagle” multi-role idea.