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F-15s Looking for the AESA Edge

18-Mar-2008 16:05 EDT

Related Stories: Americas - USA, Boeing, Contracts - Awards, Fighters & Attack, New Systems Tech, Radars, Raytheon, Spotlight articles, Testing & Evaluation

ELEC AN-APG-63
Before: APG-63 MSA
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F-15C Eagle air superiority fighters have traditionally used APG-63 radars with mechanically steered arrays. While upgrades over the years have improved them, the mechanical steering components are a point of potential failure given the stresses put on them, and better radar technologies have appeared. With cruise missile defense rising in importance, and longer-range detection of threats desired, upgrades are necessary. They may also correct a known air-air weakness that can reputedly be exploited by aircraft like Russia’s SU-30 family, though other reports claim that the mechanically-scanned APG-63v1s have also worked to close that hole. Thus far, 18 USAF F-15Cs have been modified to carry APG-63v2 radars – a misnomer, since the upgrade uses a revolutionary new AESA technology that bears little resemblance to its predecessor.

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 them 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. There’s also a maintenance advantage. A partial failure in previous radars renders them unfit for use, but AESA radars only suffer a slight performance drop if some of their TR modules fail. The fighter can still fly as it awaits a fix, enjoying all of the radar’s simul-mode, range, focusing, low “leakage,” and communications benefits. 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.

The USAF is discussing a retrofit set that would turn the F-15Cs into multi-role fighters; an AESA radar would be part of that, and the program to equip select F-15C units with AESA radars as an air-air improvement continues. They will now be joined by the USAF’s entire 2-seat, multi-role F-15E Strike Eagle fleet, and the F-15C program is underway despite ongoing concerns about that fleet’s durability…

The F-15’s Radars

ELEC AN-APG-63v2
APG-63v2
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The USAF’s F-15C air superiority fighters have traditionally used APG-63 pulse-Doppler radars with mechanically steered arrays. 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 U.S. Air Force and the air forces of Israel, Japan, and Saudi Arabia.

The multi-mode AN/APG-70 mechanically-scanned array radar is a 1980s derivative of the APG-63 that adds air-ground modes and maintainability improvements. Gate array technology adds air-ground modes, and improve air-air effectiveness as well. 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. 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. It is used on the USA’s AC-130U Specter gunship aircraft.

The AN/APG-63v1 is a 1990s reliability/ maintainability upgrade that adds modern hardware with opportunities for capability growth, and enhances air-air and air-ground capabilities. It is NOT an AESA radar. Raytheon has received 5 production orders to deliver 161 APG-63(V)1 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 40+ radar systems and spares will be delivered to Korea for their F-15K. Some Japanese F-15Js have also been fitted with a license-produced Mitsubishi Electric (Melco) APG-63v1 as a first step toward a general fleet upgrade.

ELEC AN-APG-63v3 Labeled
AN/APG-63v3
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Raytheon’s AN/APG-63v2 was 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-63v3/4 for testing purposes. Current plans call for up to 48 more APG-63v3-equipped F-15Cs, but some options under discussion could grow that number.

The Raytheon APG-63v3 AESA radar 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 had a square profile, the APG-63(V)3 radar can be recognized by the rounder shape of its array, and 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 has now been picked to equip the USAF’s F-15Es, beating Nortrop Grumman’s offer of the AN/APG-77v1 radar that equips the F-22A Block 20. Singapore’s new F-15SG Strike Eagles will also use the APG-63v3 radar, and Japan has reportedly expressed interest in it as a fleet upgrade possibility for its F-15J (F-15 C/D equivalents).

Contracts & Key Events

ELEC AN-APG-63v3
AN/APG-63v3 AESA
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March 17/08: Boeing announces awarded a $130 million U.S. Air Force contract to upgrade 16 Air Force and Air National Guard F-15C Eagles with the APG-63(v)3 AESA radar. 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 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.

Nov 2/07: The competition between Raytheon (APG-63v3) and Northrop Grumman (the Raptor’s APG-77) to supply next-generation radars for the USAF’s F-15E Strike Eagles has a winner! Raytheon’s AN/APGv3 has been selected by Boeing to refit all 224 F-15Es in the USAF fleet, in anticipation of an Air Force F-15E RMP System Design and Development (SDD) contract in 2008. Boeing is the F-15 family’s developer and prime contractor; their deep knowledge of the platform means that they are unlikely to lose the resulting contract, even if it’s competed.

The F-15E development program will run parallel with the United States Air Force and Air National Guard F-15C AESA program, which is already in progress. During the SDD phase, Raytheon will produce AESA radar test units and support Boeing’s efforts to integrate the AESA radar into the F-15E weapon system. The integration activity will take place at Boeing facilities in St. Louis prior to entering the developmental and initial operational test and evaluation flight programs. The contract includes production options for retrofit of the fleet, once testing is complete.

Dr. Tom Kennedy, vice president for the Tactical Airborne Systems group of Raytheon SAS, adds that “Additionally, we have built in capabilities for future enhancements such as radar common data link.” RCDL is the name for the high-bandwidth AESA radar communications link DID has covered elsewhere. Boeing release | Raytheon release | Aviation Week’s Ares.

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 and a 7th spare to the Air National Guard as part of its F-15C upgrade program. Raytheon will deliver 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-83v3 radars 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-15C, which have included a fighter-to-fighter data link, GPS navigation, and the Joint Helmet Mounted Cueing System (JHMCS) helmet sight.

ORD_AIM-120_AMRAAM_Launch_F-15C.jpg
F-15C fires AMRAAM
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Sept 27/06: 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: 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: 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 those upgrade project. See “USAF wants competition for F-15E Strike Eagle radar upgrade.”

Additional Readings

  • GlobalSecurity – F-15 Eagle. Includes information re: US and foreign variants.
  • Aviation Week (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 (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. “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…”