F-15 eagle

The McDonnell Douglas F-15 Eagle is an American twin-engine, all-weather tactical fighter aircraft designed by McDonnell Douglas (now Boeing) to gain and maintain air supremacy in aerial combat. It is among the most successful modern fighters, with over 100 victories and no losses in aerial combat, with the majority of the kills scored by the Israeli Air Force.[3][4] Following reviews of proposals, the United States Air Force selected McDonnell Douglas' design in 1967 to meet the service's need for a dedicated air superiority fighter. The Eagle first flew in July 1972, and entered service in 1976. The Eagle has been exported to Israel, Japan, and Saudi Arabia, among other nations. The F-15 was originally envisioned as a pure air superiority aircraft. Its design included a secondary ground-attack capability[5] that was largely unused. The design proved flexible enough that an all-weather strike derivative, the F-15E Strike Eagle, was later developed, entering service in 1989. The F-15 Eagle is expected to be in service with the U.S. Air Force past 2025.[6] Newer models are still being produced for foreign users. The F-15 production line is set to end in 2019, 47 years after the type's first flight.

Origins
The F-15 can ultimately trace its origins to the Vietnam War, when the U.S. Air Force and the U.S. Navy fought over tactical aircraft being used in the war. At the time, Defense Secretary Robert McNamara was pressing for both services to use as many common aircraft as possible, even if there were performance sacrifices involved. As part of this policy, the USAF and Navy were involved in the TFX (F-111) program, aiming to deliver a medium-range interdiction aircraft in Air Force use that would also serve as a long-range interceptor aircraft for the Navy.[8] In January 1965, Secretary McNamara asked the Air Force to consider a new low-cost tactical fighter design for short-range roles and close air support to replace several types like the F-100 Super Sabre and various light bombers then in service. Two basic designs could fill this role; the Navy favored designs like the Douglas A-4 Skyhawk and LTV A-7 Corsair II, pure attack aircraft, while the Air Force was more interested in fighter-bombers like the Northrop F-5, fighters with a secondary attack capability. The former were more capable in the tactical role, while the latter might be less so but could defend themselves. If the Air Force did choose an attack design, maintaining air superiority would be a top priority. The next month, a report on light tactical aircraft suggested the Air Force purchase the F-5 or A-7, and consider a new higher-performance aircraft to ensure its air superiority. This point was driven home after the loss of two Republic F-105 Thunderchief aircraft to obsolete MiG-15s or MiG-17s on 4 April 1965.[8] In April 1965, Harold Brown, at that time director of the DDR&E, stated the favored position was to consider the F-5, and begin studies of the "F-X".[N 1] These early studies envisioned a production run of 800 to 1,000 aircraft, and stressed maneuverability over speed; it also stated that the aircraft would not be considered without some level of ground attack capability.[9] On 1 August, Gabriel Disosway took command of Tactical Air Command (TAC) and reiterated calls for the F-X, but lowered the required performance from Mach 3 to 2.5 to lower costs.[10] Ultimately, the Air Force chose the A-7 over the F-5 for the support role on 5 November 1965,[11] giving further impetus for an air superiority design as the A-7 lacked any credible air-to-air capability. An official requirements document was finalized in October, and sent out as a request for proposals (RFP) to 13 companies on 8 December 1965. Eight companies responded with proposals. Following a downselect, four companies were asked to provide further developments. In total, they developed some 500 design concepts. Typical designs featured variable-sweep wings, weighed over 60,000 pounds (27,000 kg), included a top speed of Mach 2.7 and a thrust-to-weight ratio of 0.75.[12] When the proposals were studied in July 1966, the aircraft were roughly the size and weight of the TFX, and like that aircraft, a design that could not be considered an air superiority fighter.[13]

Smaller, lighter
Through this period, studies of combat over Vietnam were producing worrying results. Previous doctrine had stressed long-range combat using missiles, and optimized aircraft for this role. The result was highly loaded aircraft with large radars and excellent speed, but limited maneuverability and often lacking a gun. The canonical example was the McDonnell Douglas F-4 Phantom II, used by the USAF, U.S. Navy and U.S. Marine Corps to provide air superiority over Vietnam, the only fighter with enough power, range, and maneuverability to be given the primary task of dealing with the threat of Soviet fighters while flying with visual engagement rules.[14]

In practice, both due to policy and practical reasons,[14] aircraft were closing to visual range and maneuvering, placing the larger US aircraft at a disadvantage to the much less expensive day fighters like the MiG-21. Moreover, missiles proved to be much less reliable than predicted, especially in close range combat. Although improved training and the introduction of the M61 Vulcan cannon did much to address the disparity, these early outcomes led to considerable re-evaluation of the 1963 Project Forecast doctrine.[15] This led to John Boyd's Energy-Maneuverability (E-M) theory, which stressed that extra power and maneuverability were key aspects of a successful fighter design, and these were more important than outright speed. Through tireless championing of the concepts, and good timing with the "failure" of the initial F-X project, the "fighter mafia" pressed for a lightweight day fighter that could be built and operated in large numbers in order to ensure air superiority.[16] In early 1967, they proposed that the ideal design had a thrust-to-weight ratio of near 1:1, a maximum speed further reduced to Mach 2.3, a weight of 40,000 pounds (18,000 kg) and a wing loading of 80 lb/ft².[17] By this time, the Navy had decided the F-111 would not meet their requirements, and began development of a new dedicated fighter design, the VFAX program. In May 1966, McNamara again asked the forces to study the designs and see if the VFAX would meet the Air Force's F-X needs. The resulting studies took eighteen months, and concluded that the desired features were too different; the Navy stressed loiter time and mission flexibility, while the Air Force was now looking primarily for maneuverability.[18]

Focus on air superiority
In 1967 the Soviet Union revealed the MiG-25 'Foxbat' at the Domodedovo airfield near Moscow.[14][19] The MiG-25 was designed as a high-speed, high-altitude interceptor aircraft, and made many performance tradeoffs to excel in this role.[20] Among these was the requirement for very high speed, over Mach 2.8, which demanded the use of stainless steel instead of aluminum in many locations on the aircraft. The added weight demanded a much larger wing to allow the aircraft to operate at the required high altitudes. However, to observers, it appeared outwardly similar to the very large F-X studies: an aircraft with high speed and a large wing offering high maneuverability, leading to serious concerns throughout the Department of Defense and the various arms that the US was being outclassed. The MiG-23 was likewise a subject of concern and it was generally believed to be a better aircraft than the F-4. The F-X would outclass the MiG-23, but now it appeared that that MiG-25 would be superior in speed, ceiling and endurance to all existing US fighters, even the F-X.[21] Thus, an effort to improve the F-X followed.[22]

Both Headquarters USAF and the TAC continued to call for a multipurpose aircraft, while both Disosway and Air Chief of Staff Bruce K. Holloway pressed for a pure air superiority design that would be able to meet the expected performance of the MiG-25. During the same period, the Navy had ended its VFAX program and instead accepted a proposal from Grumman Aircraft for a smaller and more maneuverable design known as VFX. VFX was considerably closer to the evolving F-X requirements. The Air Force in-fighting eventually ended by the worry that the Navy's VFAX would be forced on them; in May 1968 it was stated that "We finally decided - and I hope there is no one who still disagrees - that this aircraft is going to be an air superiority fighter".[18]

F-15A cockpit

In September 1968, a request for proposals (RFP) was released to major aerospace companies. These requirements called for single-seat fighter having a maximum take-off weight of 40,000 pounds (18,000 kg) for the air-to-air role with a maximum speed of Mach 2.5 and a thrust to weight ratio of nearly 1:1 at mission weight.[23] It also called for a twin-engine arrangement as it was believed this would respond to throttle changes more rapidly, and might offer commonality with the Navy's VFX program. However, details of the avionics were left largely undefined, as it was not clear whether to build a larger aircraft with a powerful radar that could detect the enemy at longer ranges, or alternately a smaller aircraft that would make it more difficult for the enemy to detect it.[24] Four companies submitted proposals, with the Air Force eliminating General Dynamics and awarding contracts to Fairchild Republic, North American Rockwell, and McDonnell Douglas for the definition phase in December 1968. The companies submitted technical proposals by June 1969. The Air Force announced the selection of McDonnell Douglas on 23 December 1969.[25] The winning design resembled the twin-tailed F-14, but with fixed wings; both designs were based on configurations studied in wind tunnel testing by NASA.[26] McDonnell Douglas F-15A (S/N 71-0280) during the type's first flight

The Eagle's initial versions were the F-15 single-seat variant and TF-15 twin-seat variant. (After the F-15C was first flown the designations were changed to "F-15A" and "F-15B"). These versions would be powered by new Pratt & Whitney F100 engines to achieve a combat thrust-to-weight ratio in excess of 1:1. A proposed 25 mm Ford-Philco GAU-7 cannon with caseless ammunition suffered development problems. It was dropped in favor of the standard M61 Vulcan gun. The F-15 used conformal carriage of four Sparrow missiles like the Phantom. The fixed wing was put onto a flat, wide fuselage that also provided an effective lifting surface. The first F-15A flight was made on 27 July 1972 with the first flight of the two-seat F-15B following in July 1973.[27]

The F-15 has a "look-down/shoot-down" radar that can distinguish low-flying moving targets from ground clutter. The F-15 would use computer technology with new controls and displays to lower pilot workload and require only one pilot to save weight. Unlike the F-14 or F-4, the F-15 has only a single canopy frame with clear vision forward. The USAF introduced the F-15 as "the first dedicated USAF air superiority fighter since the North American F-86 Sabre."[28]

The F-15 was favored by customers such as the Israel and Japan air arms. Criticism from the fighter mafia that the F-15 was too large to be a dedicated dogfighter, and too expensive to procure in large numbers, led to the Lightweight Fighter (LWF) program, which led to the USAF General Dynamics F-16 Fighting Falcon and the middle-weight Navy McDonnell Douglas F/A-18 Hornet.[29]

Further development
The single-seat F-15C and two-seat F-15D models entered production in 1978 and conducted their first flights in February and June of that year.[30] These models were fitted with the Production Eagle Package (PEP 2000), which included 2,000 lb (900 kg) of additional internal fuel, provisions for exterior conformal fuel tanks, and an increased maximum takeoff weight of up to 68,000 lb (30,700 kg).[31] The increased takeoff weight allows internal fuel, a full weapons load, conformal fuel tanks, and three external fuel tanks to be carried. The APG-63 radar uses a programmable signal processor (PSP), enabling the radar to be reprogrammable for additional purposes such as the addition of new armaments and equipment. The PSP was the first of its kind in the world, and the upgraded APG-63 radar was the first radar to use it. Other improvements included strengthened landing gear, a new digital central computer,[32] and an overload warning system, which allows the pilot to fly up to 9 g at all weights.[30] USAF McDonnell Douglas F-15E arrives for the 2014 Royal International Air Tattoo, England

The F-15 Multistage Improvement Program (MSIP) was initiated in February 1983 with the first production MSIP F-15C produced in 1985. Improvements included an upgraded central computer; a Programmable Armament Control Set, allowing for advanced versions of the AIM-7, AIM-9, and AIM-120A missiles; and an expanded Tactical Electronic Warfare System that provides improvements to the ALR-56C radar warning receiver and ALQ-135 countermeasure set. The final 43 F-15Cs included the Hughes APG-70 radar developed for the F-15E; these are sometimes referred as Enhanced Eagles. Earlier MSIP F-15Cs with the APG-63 were upgraded to the APG-63(V)1 to improve maintainability and to perform similar to the APG-70. Existing F-15s were retrofitted with these improvements.[33] In 1979, McDonnell Douglas and F-15 radar manufacturer, Hughes, teamed to privately develop a strike fighter version of the F-15. This version competed in the Air Force's Dual-Role Fighter competition starting in 1982. The Boeing F-15E strike variant was selected for production over General Dynamics' competing F-16XL in 1984.[34] Beginning in 1985, F-15C and D models were equipped with the improved P&W F100-PW-220 engine and digital engine controls, providing quicker throttle response, reduced wear, and lower fuel consumption. Starting in 1997, original F100-PW-100 engines were upgraded to a similar configuration with the designation F100-PW-220E starting.[35] Beginning in 2007, 178 USAF F-15Cs were retrofitted with the AN/APG-63(V)3 Active Electronically Scanned Array (AESA) radar.[36] A significant number of F-15s are to be equipped with the Joint Helmet Mounted Cueing System (JHMCS).[37] Lockheed Martin is working on an IRST system for the F-15C.[38] A follow-on upgrade called the Eagle passive/active warning survivability system (EPAWSS) was planned but remained unfunded.[39] Boeing was selected in October 2015 to serve as prime contractor for the EPAWSS, with BAE Systems selected as subcontractor. The EPAWSS is an all-digital system with advanced electronic countermeasures, radar warning, and increased chaff and flare capabilities in a smaller footprint than the 1980s-era Tactical Electronic Warfare System. More than 400 F-15Cs and F-15Es will have the system installed.[40] In September 2015, Boeing unveiled its 2040C Eagle upgrade, designed to keep the F-15 relevant through 2040. Seen as a necessity because of the low numbers of F-22s procured, the upgrade builds upon the company's F-15SE Silent Eagle concept with low-observable features. Most improvements focus on lethality including quad-pack munitions racks to double its missile load to 16, conformal fuel tanks for extended range, "Talon HATE" communications pod to communicate with 5th generation fighters, the APG-63(v)3 AESA radar, a long-range infrared search and track (IRST) sensor, and Northrop Grumman's Eagle Passive/Active Warning Survivability System (EPAWSS) systems.[41][42]

Overview
F-15C executing a maximum performance takeoff.

The F-15 has an all-metal semi-monocoque fuselage with a large cantilever shoulder-mounted wing. The empennage is metal and composite construction, with twin aluminium/composite material honeycomb structure fins with boron-composite skin, resulting in an exceptionally thin tailplane and rudders with all-moving composite horizontal tail surfaces outboard of the fins. The F-15 has a spine-mounted air brake and retractable tricycle landing gear. It is powered by two Pratt & Whitney F100 Axial compressor turbofan engines with afterburners mounted side-by-side in the fuselage, fed by intake ramps. The cockpit is mounted high in the forward fuselage with a one-piece windscreen and large canopy to increase visibility. The airframe began to incorporate advanced superplastically formed titanium components in the 1980s. The F-15's maneuverability is derived from low wing loading (weight to wing area ratio) with a high thrust-to-weight ratio enabling the aircraft to turn tightly without losing airspeed. The F-15 can climb to 30,000 ft (10,000 m) in around 60 seconds. The thrust output of the dual engines is greater than the aircraft's weight, thus giving it the ability to accelerate in a vertical climb. The weapons and flight control systems are designed so that one person can safely and effectively perform air-to-air combat.[43] The A and C-models are single-seat variants; these were the main air superiority versions produced. B and D-models add a second seat behind the pilot for training. E-models use the second seat for a weapon systems officer. Visibly, the F-15 has a unique feature vis-à-vis other modern fighter aircraft: it does not have the distinctive turkey feather aerodynamic exhaust petals covering its engine nozzles. This is because the petal design on the F-15 was problematic and could fall off in flight; therefore they were removed, resulting in a 3% aerodynamic drag increase.[44]

Avionics
A wing over maneuver displays the clean lines and high-wing design of an F-15E from Elmendorf AFB, Alaska.

AN/APG-63 radar

A multi-mission avionics system includes a heads-up display (HUD), advanced radar, AN/ASN-109 inertial guidance system (INS), flight instruments, ultra high frequency (UHF) communications, and Tactical air navigation system (TACAN) and Instrument landing system (ILS) receivers. It also has an internally mounted, tactical electronic warfare system, Identification friend or foe (IFF) system, electronic countermeasures suite and a central digital computer.[45]

The head-up display projects, through a combiner, all essential flight information gathered by the integrated avionics system. This display, visible in any light condition, provides the pilot information necessary to track and destroy an enemy aircraft without having to look down at cockpit instruments.[46] The F-15's versatile APG-63 and 70 pulse-Doppler radar systems can look up at high-flying targets and look-down/shoot-down at low-flying targets without being confused by ground clutter. These radars can detect and track aircraft and small high-speed targets at distances beyond visual range down to close range, and at altitudes down to treetop level. The APG-63 has a basic range of 100 miles (87 nmi; 160 km). The radar feeds target information into the central computer for effective weapons delivery. For close-in dogfights, the radar automatically acquires enemy aircraft, and this information is projected on the head-up display. The F-15's electronic warfare system provides both threat warning (radar warning receiver) and automatic countermeasures against selected threats.[47]

Weaponry and external stores
M61 Vulcan mounted on the side of right engine intake

A variety of air-to-air weaponry can be carried by the F-15. An automated weapon system enables the pilot to release weapons effectively and safely, using the head-up display and the avionics and weapons controls located on the engine throttles or control stick. When the pilot changes from one weapon system to another, visual guidance for the required weapon automatically appears on the head-up display.[48]

The Eagle can be armed with combinations of four different air-to-air weapons: AIM-7F/M Sparrow missiles or AIM-120 AMRAAM advanced medium range air-to-air missiles on its lower fuselage corners, AIM-9L/M Sidewinder or AIM-120 AMRAAM missiles on two pylons under the wings, and an internal 20 millimetres (0.79 in) M61 Vulcan Gatling gun in the right wing root.[49]

F-15C external stores stations

Low-drag conformal fuel tanks (CFTs) were developed for the F-15C and D models. They can be attached to the sides of the engine air intakes under each wing and are designed to the same load factors and airspeed limits as the basic aircraft.[49] They degrade performance by increasing drag and cannot be jettisoned in-flight (unlike conventional external tanks). Each conformal fuel tank can hold 750 U.S. gallons (2,840 L) of fuel.[50] These tanks increase range and reduce the need for in-flight refueling. All external stations for munitions remain available with the tanks in use. Moreover, Sparrow or AMRAAM missiles can be attached to the corners of the conformal fuel tanks.[31] The 57 FIS based at Keflavik NAS, Iceland was the only C-model squadron to use CFTs on a regular basis due to its extended operations over the North Atlantic. With the closure of the 57 FIS, the F-15E is the only variant to carry them on a routine basis. CFTs have also been sold to Israel and Saudi Arabia.

Upgrades
F-15E with speed brake deployed and conformal tanks fitted

The McDonnell Douglas F-15E Strike Eagle is a two-seat, dual-role, totally integrated fighter for all-weather, air-to-air and deep interdiction missions. The rear cockpit is upgraded to include four multi-purpose cathode ray tube displays for aircraft systems and weapons management. The digital, triple-redundant Lear Siegler aircraft flight control system permits coupled automatic terrain following, enhanced by a ring-laser gyro inertial navigation system.[51] For low-altitude, high-speed penetration and precision attack on tactical targets at night or in adverse weather, the F-15E carries a high-resolution APG-70 radar and LANTIRN pods to provide thermography.[47]

The APG-63(V)2 active electronically scanned array (AESA) radar has been retrofitted to 18 U.S. Air Force F-15C aircraft.[52] This upgrade includes most of the new hardware from the APG-63(V)1, but adds an AESA to provide increased pilot situation awareness. The AESA radar has an exceptionally agile beam, providing nearly instantaneous track updates and enhanced multi-target tracking capability. The APG-63(V)2 is compatible with current F-15C weapon loads and enables pilots to take full advantage of AIM-120 AMRAAM capabilities, simultaneously guiding multiple missiles to several targets widely spaced in azimuth, elevation, or range.

Introduction and early service
The largest operator of the F-15 is the United States Air Force. The first Eagle (F-15B) was delivered 13 November 1974.[53] In January 1976, the first Eagle destined for a combat squadron, the 555th TFS, was delivered.[53] These initial aircraft carried the Hughes Aircraft (now Raytheon) APG-63 radar.

The first kill by an F-15 was scored by Israeli Air Force (IAF) ace Moshe Melnik in 1979.[54] In 1979–81, during Israeli raids against Palestinian factions in Lebanon, F-15As reportedly downed 13 Syrian MiG-21 "Fishbeds" and two Syrian MiG-25 "Foxbats". Syrian claims 13 aircraft were lost with five F-15s shot down in the raids. Another two F-15s were reportedly downed by SAMs.[55] Israeli F-15As and Bs participated as escorts in Operation Opera, an air strike on an Iraqi nuclear reactor. In the 1982 Lebanon War, Israeli F-15s were credited with 41 Syrian aircraft destroyed (23 MiG-21 "Fishbeds", 17 MiG-23 "Floggers", and one Aérospatiale SA.342L Gazelle helicopter). Syrian accounts state eight F-15s were shot down, five by MiG-21s and three by MiG-23MLs.[56] Israel was the only operator to use and develop the air to ground abilities of the air superiority F-15 variants. The main reason being its range being well beyond any other combat aircraft in Israeli inventory in the 1980s. The first known use of F-15s for a strike mission was during Operation Wooden Leg on 1 October 1985, with six F-15Ds attacking PLO Headquarters in Tunis with two GBU-15 guided bombs per aircraft and two F-15Cs re-striking the ruins with six Mk-82 unguided bombs each.[57] This was one of the few times air superiority F-15s (A/B/C/D models) were used in tactical strike missions.[58] Israeli air superiority F-15 variants have since been extensively upgraded to carry a wider range of air to ground armaments including JDAM GPS guided bombs and Popeye missile.[59] Royal Saudi Air Force F-15C pilots reportedly shot down two Iranian Air Force F-4E Phantom IIs in a skirmish on 5 June 1984.[60][61]

Anti-satellite trials
ASM-135 ASAT test launch from F-15A 76-0084 in 1985

The ASM-135 missile was designed to be a standoff anti-satellite (ASAT) weapon, with the F-15 acting as a first stage. The Soviet Union could correlate a U.S. rocket launch with a spy satellite loss, but an F-15 carrying an ASAT would blend in among hundreds of F-15 flights. From January 1984 to September 1986, two F-15As were used as launch platforms for the ASAT missile. The F-15As were modified to carry one ASM-135 on the centerline station with extra equipment within a special centerline pylon.[62][63] The launch aircraft executed a Mach 1.22, 3.8 g climb at 65° to release the ASAT missile at an altitude of 38,100 ft (11,600 m).[64][65] The flight computer was updated to control the zoom-climb and missile release.

The third test flight involved a retired P78-1 solar observatory satellite in a 345-mile (555 km) orbit, which was destroyed by kinetic energy.[64] The pilot, USAF Major Wilbert D. "Doug" Pearson, became the only pilot to destroy a satellite.[65] The ASAT program involved five test launches. The program was officially terminated in 1988.[62][65]

Gulf War and aftermath
The USAF began deploying F-15C, D and E model aircraft to the Persian Gulf region in August 1990 for Operations Desert Shield and Desert Storm. During Gulf War combat against Iraqi forces, the F-15 accounted for 36 of the 39 air-to-air victories by the U.S Air Force. Iraq has confirmed the loss of 23 of its aircraft in air-to-air combat.[66] The F-15C and D fighters were used in the air superiority role while F-15E Strike Eagles were used in air-to-ground attacks mainly at night, hunting modified Scud missile launchers and artillery sites using the LANTIRN system.[67] According to the USAF, its F-15Cs had 34 confirmed kills of Iraqi aircraft during the 1991 Gulf War, most of them by missile fire: five MiG-29 "Fulcrums", two MiG-25 "Foxbats", eight MiG-23 "Floggers", two MiG-21 "Fishbeds", two Su-25 "Frogfoots", four Su-22 "Fitters", one Su-7, six Mirage F1s, one Il-76 cargo plane, one Pilatus PC-9 trainer, and two Mi-8 helicopters. Air superiority was achieved in the first three days of the conflict; many of the later kills were reportedly of Iraqi aircraft fleeing to Iran, rather than engaging U.S. aircraft. A Strike Eagle achieved an aerial kill of an Iraqi Mi-8 helicopter with a laser-guided bomb. Two F-15Es were lost to ground fire, another was damaged on the ground by a Scud strike on Dhahran air base.[68]

On 11 November 1990, a Royal Saudi Air Force (RSAF) pilot defected to Sudan with an F-15C fighter during Operation Desert Shield. Saudi Arabia paid US$40 million for return of the aircraft three months later.[69] RSAF F-15s shot down two Iraqi Mirage F1s during the Operation Desert storm.[70] According to the Saudis, one F-15C was lost to a crash during the Gulf War in 1991.[71] The IRAF claims this fighter was part of two F-15Cs that engaged two Iraqi MiG-25PDs, and was hit by an R-40 missile before crashing.[72]

A Royal Saudi Air Force F-15 approaches a KC-135 for refueling during Operation Desert Shield.

They have since been deployed to support Operation Southern Watch, the patrolling of the No-Fly Zone in Southern Iraq; Operation Provide Comfort in Turkey; in support of NATO operations in Bosnia, and recent air expeditionary force deployments. In 1994, two U.S. Army Sikorsky UH-60 Black Hawks were mistakenly downed by USAF F-15Cs in northern Iraq in a friendly fire incident.[73] USAF F-15Cs shot down four Yugoslav MiG-29s using AIM-120 missiles during NATO's 1999 intervention in Kosovo, Operation Allied Force.[74]

Structural defects
All F-15 aircraft were grounded by the US Air Force after a Missouri Air National Guard F-15C came apart in flight and crashed on 2 November 2007. The newer F-15E fleet was later cleared for continued operations. The US Air Force reported on 28 November 2007 that a critical location in the upper longerons on the F-15C model was suspected of causing the failure, causing the fuselage forward of the air intakes, including the cockpit and radome, to separate from the airframe.[75]

F-15A through D-model aircraft were grounded until the location received more detailed inspections and repairs as needed.[76] The grounding of F-15s received media attention as it began to place strains on the nation's air defense efforts.[77] The grounding forced some states to rely on their neighboring states' fighters for air defense protection, and Alaska to depend on Canadian Forces' fighter support.[77]

On 8 January 2008, the USAF Air Combat Command (ACC) cleared a portion of its F-15A through D-model fleet for return to flying status. It also recommended a limited return to flight for units worldwide using the affected models.[78] The accident review board report was released on 10 January 2008. The report stated that analysis of the F-15C wreckage determined that the longeron did not meet drawing specifications, which led to fatigue cracks and finally a catastrophic failure of the remaining support structures and breakup of the aircraft in flight.[79] In a report released on 10 January 2008, nine other F-15s were identified to have similar problems in the longeron. As a result of these problems, General John D. W. Corley stated that "the long-term future of the F-15 is in question."[80] On 15 February 2008, ACC cleared all its grounded F-15A/B/C/D fighters for flight pending inspections, engineering reviews and any needed repairs. ACC also recommended release of other U.S. F-15A/B/C/D aircraft.[81]

Recent service
In service with all nations the F-15 has an air-to-air combat record of 104 kills to 0 losses as of February 2008. The F-15's air superiority versions, the A/B/C/D models have not suffered any losses to enemy action.[3][82] Over half of F-15 kills have been achieved by Israeli Air Force pilots.

On 16 September 2009, the last F-15A, an Oregon Air National Guard aircraft, was retired marking the end of service for the F-15A and F-15B models in the United States.[83]

A USAF F-15C flying over Fresno, California, in 2013

With the retirement of the F-15A and B models, the F-15C and D models are being supplemented in U.S. service by the F-22 Raptor. However, since F-22 production has been halted, the F-15 may be in service in current squadrons much longer than originally thought. As of 2013, regular Air Force F-15C and F-15D fighters are based overseas with the Pacific Air Forces (PACAF) at Kadena AB in Japan[84] and with the U.S. Air Forces in Europe (USAFE) at RAF Lakenheath in the United Kingdom.[85] Other Regular Air Force F-15s are operated by Air Combat Command as adversary/aggressor platforms at Nellis AFB, Nevada, and by Air Force Material Command in test and evaluation roles at Edwards AFB, California and Eglin AFB, Florida. All remaining combat coded F-15Cs and F-15Ds are operated by the Air National Guard.

USAF is upgrading 178 F-15C/Ds with the AN/APG-63(V)3 AESA radar,[36] and upgrade other F-15s with the Joint Helmet Mounted Cueing System.[37] The Air Force plans to keep 178 F-15C/Ds along with 224 F-15Es in service beyond 2025. The F-15E will remain in service for years to come because of the model's primary air-to-ground role and the lower number of hours on the F-15E airframes.[6]

As part of the Air Force's FY 2015 budget, the F-15C faces cuts or retirement in response to sequestration. Cuts are principally directed at platforms with single-mission capabilities. The retirement of some of the 250 F-15C fighters would save maintenance and upgrade costs, which could be redirected to speed procurement of the F-35 Lightning II. The air-to-air combat role would be taken up preeminently by the F-22 Raptor, while the F-35 would support it in conjunction with the Raptor. Even if this option is pursued, at least part of the F-15C fleet is likely to be preserved.[86][87] The Air Force's FY 2015 budget proposal would reduce the F-15C fleet by 51 aircraft.[88]

Basic models
USAF F-15C fires an AIM-7 Sparrow in 2005

A view of an F-15E cockpit from an aerial refueling tanker
 * F-15A
 * Single-seat all-weather air-superiority fighter version, 384 built 1972–79.[89]


 * F-15B
 * Two-seat training version, formerly designated TF-15A, 61 built 1972–79.[89]


 * F-15C
 * Improved single-seat all-weather air-superiority fighter version, 483 built 1979–85.[89] The last 43 F-15Cs were upgraded with AN/APG-70 radar and later the AN/APG-63(V)1 radar.


 * F-15D
 * Two-seat training version, 92 built 1979–85.[89]


 * F-15J
 * Single-seat all-weather air-superiority fighter version for the Japan Air Self-Defense Force 139 built under license in Japan by Mitsubishi Heavy Industries 1981–97, two built in St. Louis.[89]


 * F-15DJ
 * Two-seat training version for the Japan Air Self-Defense Force. 12

built in St. Louis, and 25 built under license in Japan by Mitsubishi during 1981–97.[89]
 * F-15N Sea Eagle
 * The F-15N was a carrier-capable variant proposed in the early 1970s

to the U.S. Navy as an alternative to the heavier and, at the time, considered as "riskier" technology program, the Grumman F-14 Tomcat. The F-15N-PHX was another proposed naval version capable of carrying the AIM-54 Phoenix missile. These featured folding wingtips, reinforced landing gear and a stronger tailhook for shipboard operation.[90]
 * F-15E Strike Eagle
 * All-weather multirole strike version, fitted with conformal fuel tanks. It was developed into the F-15I, F-15S, F-15K, F-15SG, F-15SA, and other variants.


 * F-15SE Silent Eagle
 * Proposed F-15E variant with a reduced radar cross-section.

Proposed upgrade to the F-15C, allowing it to supplement the F-22 in the Air-Superiority role. The 2040C concept is an evolution of the Silent Eagle proposed to South Korea, with some low-observable improvements but mostly a focus on the latest air capabilities and lethality. Proposal includes infra-red search and track, doubling the number of weapon stations, with quad racks for a maximum of 16 air-to-air missiles, Passive/Active Warning Survivability System, conformal fuel tanks, upgraded APG-63(v)3 AESA and a "Talon HATE" communications pod allowing data-transfer with the F-22.[91][92]
 * F-15 2040C

Prototypes
F-15A 71-0280, the first prototype

Twelve prototypes were built and used for trials by the F-15 Joint Test Force at Edwards Air Force Base using McDonnell Douglas and United States Air Force personnel. Most prototypes were later used by NASA for trials and experiments.
 * F-15A-1, AF Ser. No. 71-0280
 * Was the first F-15 to fly on 11 July 1972 from Edwards Air Force

Base, it was used as a trial aircraft for exploring the flight envelope, general handling and testing the carriage of external stores.
 * F-15A-1, AF Ser. No. 71-0281
 * The second prototype first flew on 26 September 1972 and was used to test the F100 engine.


 * F-15A-2, AF Ser. No. 71-0282
 * First flew on 4 November 1972 and was used to test the APG-62 radar and avionics.


 * F-15A-2, AF Ser. No. 71-0283
 * First flew on 13 January 1973 and was used as a structural test

aircraft, it was the first aircraft to have the smaller wingtips to clear a severe buffet problem found on earlier aircraft.
 * F-15A-2, AF Ser. No. 71-0284
 * First flew on 7 March 1973 it was used for armament development and was the first aircraft fitted with an internal cannon.


 * F-15A-3, AF Ser. No. 71-0285
 * First flew on 23 May 1973 and was used to test the missile fire control system and other avionics.


 * F-15A-3, AF Ser. No. 71-0286
 * First flew on 14 June 1973 and was used for armament trials and testing external fuel stores.


 * F-15A-4, AF Ser. No. 71-0287
 * First flew on 25 August 1973 and was used for spin recovery, angle

of attack and fuel system testing, it was fitted with an anti-spin recovery parachute. The aircraft was loaned to NASA from 1976 for engine development trials.
 * F-15A-4, AF Ser. No. 71-0288
 * First flew on 20 October 1973 and was used to test integrated

aircraft and engine performance, it was later used by McDonnell Douglas as a test aircraft in the 1990s.
 * F-15A-4, AF Ser. No. 71-0289
 * First flew on 30 January 1974 and was used for trials on the radar, avionics and electronic warfare systems.


 * F-15B-1, AF Ser. No. 71-0290
 * The first two-seat prototype originally designated the TF-15A, it first flew on 7 July 1973.


 * F-15B-2, AF Ser. No. 71-0291
 * First flew on 18 October 1973 as a TF-15A and used as a test and

demonstration aircraft. In 1976 it made an overseas sales tour painted in markings to celebrate the bicentenary of the United States. Also used as the development aircraft for the F-15E as well as the first F-15 to use Conformal Fuel Tanks.

Research and test
NASA F-15B Research Testbed, aircraft No. 836 (AF Ser. No. 74-0141). Note the Quiet Spike adaption to reduce and control sonic booms
 * F-15 Streak Eagle (AF Ser. No.72-0119)
 * An unpainted F-15A stripped of most avionics demonstrated the

fighter's acceleration capabilities. The aircraft broke eight time-to-climb world records between 16 January and 1 February 1975 at Grand Forks AFB, ND. It was delivered to the National Museum of the United States Air Force in December 1980.[93]


 * F-15 STOL/MTD (AF Ser. No. 71-0290)
 * The first F-15B was converted into a short takeoff and landing, maneuver technology demonstrator aircraft.[94] In the late 1980s it received canard flight surfaces in addition to its usual horizontal tail, along with square thrust-vectoring nozzles. It was used as a short-takeoff/maneuver-technology demonstrator (S/MTD).[95]


 * F-15 ACTIVE (AF Ser. No. 71-0290)
 * The F-15 S/MTD was later converted into an advanced flight control technology research aircraft with thrust vectoring nozzles.[94]


 * F-15 IFCS (AF Ser. No. 71-0290)
 * The F-15 ACTIVE was then converted into an intelligent flight

control systems research aircraft. F-15B 71-0290 was the oldest F-15 still flying when retired in January 2009.[95]


 * F-15 MANX
 * Concept name for a tailless variant of the F-15 ACTIVE, but the NASA

ACTIVE experimental aircraft was never modified to be tailless.
 * F-15 Flight Research Facility (AF Ser. No. 71-0281 and AF Ser. No. 71-0287)
 * Two F-15A aircraft were acquired in 1976 for use by NASA's Dryden Flight Research Center

for numerous experiments such as: Highly Integrated Digital Electronic Control (HiDEC), Adaptive Engine Control System (ADECS), Self-Repairing and Self-Diagnostic Flight Control System (SRFCS) and Propulsion Controlled Aircraft System (PCA).[96] 71-0281, the second flight-test F-15A, was returned to the Air Force and became a static display at Langley AFB in 1983.
 * F-15B Research Testbed (AF Ser. No. 74-0141)
 * Acquired in 1993, it was an F-15B modified and used by NASA's Dryden Flight Research Center for flight tests.[97] ☀Role

Air superiority fighter Manufacturer McDonnell Douglas Boeing Defense, Space & Security First flight 27 July 1972 Introduction 9 January 1976 Status In service Primary users United States Air Force Japan Air Self-Defense Force Royal Saudi Air Force Israeli Air Force Number built F-15A/B/C/D/J/DJ: 1,198[1]

Unit cost

F-15A/B: US$27.9 million (1998) F-15C/D: US$29.9 million (1998)[2]

Variants McDonnell Douglas F-15E Strike Eagle McDonnell Douglas F-15 STOL/MTD Boeing F-15SE Silent Eagle Mitsubishi F-15J