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False etymology

A false etymology (fake etymology or pseudo-etymology) is a false theory about the origin or derivation of a specific word or phrase. When a false etymology becomes a popular belief in a cultural/linguistic community, it is a folk etymology (or popular etymology). Nevertheless, folk/popular etymology may also refer to the process by which a word or phrase is changed because of a popular false etymology. To disambiguate the usage of the term "folk/popular etymology", Ghil'ad Zuckermann proposes a clear-cut distinction between the derivational-only popular etymology (DOPE) and the generative popular etymology (GPE): the DOPE refers to a popular false etymology involving no neologization, and the GPE refers to neologization generated by a popular false etymology.

Such etymologies often have the feel of urban legends and can be more colorful and fanciful than the typical etymologies found in dictionaries, often involving stories of unusual practices in particular subcultures (e.g. Oxford students from non-noble families being supposedly forced to write sine nobilitate by their name, soon abbreviated to s.nob., hence the word snob).

Source and influence
Erroneous etymologies can exist for many reasons. Some are reasonable interpretations of the evidence that happen to be false. For a given word there may often have been many serious attempts by scholars to propose etymologies based on the best information available at the time, and these can be later modified or rejected as linguistic scholarship advances. The results of medieval etymology, for example, were plausible given the insights available at the time, but have often been rejected by modern linguists. The etymologies of humanist scholars in the early modern period began to produce more reliable results, but many of their hypotheses have also been superseded.

Other false etymologies are the result of specious and untrustworthy claims made by individuals, such as the unfounded claims made by Daniel Cassidy that hundreds of common English words such as baloney, grumble, and bunkum derive from the Irish language.

In the United States, some of these scandalous legends have had to do with racism and slavery; common words such as picnic, buck, and crowbar have been alleged to stem from derogatory terms or racist practices.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: False etymology


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Finch

The true finches are small to medium-sized passerine birds in the family Fringillidae. Finches generally have stout conical bills adapted for eating seeds and nuts and often have colourful plumage. They occupy a great range of habitats where they are usually resident and do not migrate. They have a worldwide native distribution except for Australia and the polar regions. The family Fringillidae contains more than two hundred species divided into fifty genera. It includes the canaries, siskins, redpolls, serins, grosbeaks and euphonias, as well as the morphologically divergent Hawaiian honeycreepers.

Many birds in other families are also commonly called "finches". These groups include the estrildid finches (Estrildidae) of the Old World tropics and Australia; some members of the Old World bunting family (Emberizidae) and the New World sparrow family (Passerellidae); and the Darwin's finches of the Galapagos islands, now considered members of the tanager family (Thraupidae).

Finches and canaries were used in the UK, US and Canada in the coal mining industry to detect carbon monoxide from the eighteenth to twentieth century. This practice ceased in the UK in 1986.

Systematics and taxonomy
The name Fringillidae for the finch family was introduced in 1819 by the English zoologist William Elford Leach in a guide to the contents of the British Museum. The taxonomy of the family, in particular the cardueline finches, has a long and complicated history. The study of the relationship between the taxa has been confounded by the recurrence of similar morphologies due to the convergence of species occupying similar niches. In 1968 the American ornithologist Raymond Andrew Paynter, Jr. wrote: Limits of the genera and relationships among the species are less understood – and subject to more controversy – in the carduelines than in any other species of passerines, with the possible exception of the estrildines [waxbills]. Beginning around 1990 a series of phylogenetic studies based on mitochondrial and nuclear DNA sequences resulted in substantial revisions in the taxonomy. Several groups of birds that had previously been assigned to other families were found to be related to the finches. The Neotropical Euphonia and the Chlorophonia were formerly placed in the tanager family Thraupidae due to their similar appearance but analysis of mitochondrial DNA sequences revealed that both genera were more closely related to the finches. They are now placed in a separate subfamily Euphoniinae within the Fringillidae. The Hawaiian honeycreepers were at one time placed in their own family, Drepanididae but were found to be closely related to the Carpodacus rosefinches and are now placed within the Carduelinae subfamily. The three largest genera, Carpodacus, Carduelis and Serinus were found to be polyphyletic. Each was split into monophyletic genera. The American rosefinches were moved from Carpodacus to Haemorhous. Carduelis was split by moving the greenfinches to Chloris and a large clade into Spinus leaving just three species in the original genus. Thirty seven species were moved from Serinus to Crithagra leaving eight species in the original genus. Today the family Fringillidae is divided into three subfamilies, the Fringillinae containing a single genus with the chaffinches, the Carduelinae containing 183 species divided into 49 genera, and the Euphoniinae containing the Euphonia and the Chlorophonia.

Although Przewalski's "rosefinch" (Urocynchramus pylzowi) has ten primary flight feathers rather than the nine primaries of other finches, it was sometimes classified in the Carduelinae. It is now assigned to a distinct family, Urocynchramidae, monotypic as to genus and species, and with no particularly close relatives among the Passeroidea.

Fossil record
Fossil remains of true finches are rare, and those that are known can mostly be assigned to extant genera at least. Like the other Passeroidea families, the true finches seem to be of roughly Middle Miocene origin, around 20 to 10 million years ago (Ma). An unidentifable finch fossil from the Messinian age, around 12 to 7.3 million years ago (Ma) during the Late Miocene subepoch, has been found at Polgárdi in Hungary.

Description
The smallest "classical" true finches are the Andean siskin (Spinus spinescens) at as little as 9.5 cm (3.8 in) and the lesser goldfinch (Spinus psaltria) at as little as 8 g. The largest species is probably the collared grosbeak (Mycerobas affinis) at up to 24 cm and 83 g, although larger lengths, to 25.5 cm in the pine grosbeak (Pinicola enucleator), and weights, to 86.1 g in the evening grosbeak (Hesperiphona vespertina), have been recorded in species which are slightly smaller on average. They typically have strong, stubby beaks, which in some species can be quite large; however, Hawaiian honeycreepers are famous for the wide range of bill shapes and sizes brought about by adaptive radiation. All true finches have 9 primary remiges and 12 rectrices. The basic plumage colour is brownish, sometimes greenish; many have considerable amounts of black, while white plumage is generally absent except as wing-bars or other signalling marks. Bright yellow and red carotenoid pigments are commonplace in this family, and thus blue structural colours are rather rare, as the yellow pigments turn the blue color into green. Many, but by no means all true finches have strong sexual dichromatism, the females typically lacking the bright carotenoid markings of males.

Distribution and habitat
The finches have a near-global distribution, being found across the Americas, Eurasia and Africa, as well as some island groups such as the Hawaiian islands. They are absent from Australasia, Antarctica, the Southern Pacific and the islands of the Indian Ocean, although some European species have been widely introduced in Australia and New Zealand.

Finches are typically inhabitants of well-wooded areas, but some can be found on mountains or even in deserts.

Behaviour
The finches are primarily granivorous, but euphoniines include considerable amounts of arthropods and berries in their diet, and Hawaiian honeycreepers evolved to utilize a wide range of food sources, including nectar. The diet of Fringillidae nestlings includes a varying amount of small arthropods. True finches have a bouncing flight like most small passerines, alternating bouts of flapping with gliding on closed wings. Most sing well and several are commonly seen cagebirds; foremost among these is the domesticated canary (Serinus canaria domestica). The nests are basket-shaped and usually built in trees, more rarely in bushes, between rocks or on similar substrate.

List of genera
The family Fringillidae contains 235 species divided into 50 genera and three subfamilies. The subfamily Carduelinae includes 18 extinct Hawaiian honeycreepers and the extinct Bonin grosbeak. See List of Fringillidae species for further details.

Subfamily Fringillinae Subfamily Carduelinae Subfamily Euphoniinae
 * Fringilla – 5 species of chaffinch, 2 species of blue chaffinch, and the brambling
 * Mycerobas – 4 Palearctic grosbeaks
 * Coccothraustes – 3 species
 * Eophona – 2 oriental grosbeaks, the Chinese and the Japanese grosbeak
 * Pinicola – pine grosbeak
 * Pyrrhula – 8 bullfinch species
 * Rhodopechys – 2 species, the Asian crimson-winged finch and the African crimson-winged finch
 * Bucanetes – trumpeter and the Mongolian finch
 * Agraphospiza – Blanford's rosefinch
 * Callacanthis – spectacled finch
 * Pyrrhoplectes – golden-naped finch
 * Procarduelis – dark-breasted rosefinch
 * Leucosticte – 6 species of mountain and rosy finches
 * Carpodacus – 28 Palearctic rosefinch species
 * Hawaiian honeycreeper group (tribe Drepanidini)
 * Melamprosops – contains a single extinct species, the po'ouli
 * Paroreomyza – 3 species, the Oahu alauahio, the Maui alauahio and the extinct kakawahie
 * Oreomystis – akikiki
 * Telespiza – 4 species, the Laysan finch, the Nihoa finch, and 2 prehistoric species
 * Loxioides – 2 species, the palila and a prehistoric species
 * Rhodacanthis – 2 recently extinct species, the lesser and the greater koa finch, and 2 prehistoric species
 * Chloridops – extinct species, the Kona grosbeak
 * Psittirostra – ou
 * Dysmorodrepanis – extinct species, the Lanai hookbill
 * Drepanis – 2 extinct species, the Hawaii mamo and the black mamo, and the extant iiwi
 * Ciridops – single recently extinct species, the Ula-ai-hawane, and 3 prehistoric species
 * Palmeria – contains a single species, the akohekohe
 * Himatione – 2 species, the apapane and the extinct Laysan honeycreeper
 * Viridonia – single extinct species, the greater amakihi
 * Akialoa – 4 recently extinct species, and 2 prehistoric species
 * Hemignathus – 4 species, only one of which is extant
 * Pseudonestor – Maui parrotbill
 * Magumma – anianiau
 * Loxops – 5 species, of which one is extinct
 * Chlorodrepanis – 3 species, the Hawaii, Oahu and Kauai amakihi
 * Haemorhous – 3 North America rosefinches
 * Chloris – 6 greenfinches
 * Rhodospiza – desert finch
 * Rhynchostruthus – 3 golden-winged grosbeaks
 * Linurgus – oriole finch
 * Crithagra – 37 species of canaries, serins and siskins from Africa and the Arabian Peninsula
 * Linaria – 4 species including the twite and three linnets
 * Acanthis – 3 redpolls
 * Loxia – 6 crossbills
 * Chrysocorythus – 2 species
 * Carduelis – 3 species including the European goldfinch
 * Serinus – 8 species including the European serin
 * Spinus – 20 species including the North American goldfinches and the Eurasian siskin
 * Euphonia – 27 species all with euphonia in their English name
 * Chlorophonia – 5 species all with chlorophonia in their English name

title: Finch


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Facilitated diffusion

Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins. Being passive, facilitated transport does not directly require chemical energy from ATP hydrolysis in the transport step itself; rather, molecules and ions move down their concentration gradient according to the principles of diffusion.

Facilitated diffusion differs from simple diffusion in several ways:

 * 1) The transport relies on molecular binding between the cargo and the membrane-embedded channel or carrier protein.
 * 2) The rate of facilitated diffusion is saturable with respect to the concentration difference between the two phases; unlike free diffusion which is linear in the concentration difference.
 * 3) The temperature dependence of facilitated transport is substantially different due to the presence of an activated binding event, as compared to free diffusion where the dependence on temperature is mild.

Polar molecules and large ions dissolved in water cannot diffuse freely across the plasma membrane due to the hydrophobic nature of the fatty acid tails of the phospholipids that comprise the lipid bilayer. Only small, non-polar molecules, such as oxygen and carbon dioxide, can diffuse easily across the membrane. Hence, small polar molecules are transported by proteins in the form of transmembrane channels. These channels are gated, meaning that they open and close, and thus deregulate the flow of ions or small polar molecules across membranes, sometimes against the osmotic gradient. Larger molecules are transported by transmembrane carrier proteins, such as permeases, that change their conformation as the molecules are carried across (e.g. glucose or amino acids). Non-polar molecules, such as retinol or lipids, are poorly soluble in water. They are transported through aqueous compartments of cells or through extracellular space by water-soluble carriers (e.g. retinol binding protein). The metabolites are not altered because no energy is required for facilitated diffusion. Only permease changes its shape in order to transport metabolites. The form of transport through a cell membrane in which a metabolite is modified is called group translocation transportation.

Glucose, sodium ions, and chloride ions are just a few examples of molecules and ions that must efficiently cross the plasma membrane but to which the lipid bilayer of the membrane is virtually impermeable. Their transport must therefore be "facilitated" by proteins that span the membrane and provide an alternative route or bypass mechanism. Some examples of proteins that mediate this process are glucose transporters, organic cation transport proteins, urea transporter, monocarboxylate transporter 8 and monocarboxylate transporter 10.

In vivo model of facilitated diffusion
Many physical and biochemical processes are regulated by diffusion. Facilitated diffusion is one form of diffusion and it is important in several metabolic processes. Facilitated diffusion is the main mechanism behind the binding of Transcription Factors (TFs) to designated target sites on the DNA molecule. The in vitro model, which is a very well known method of facilitated diffusion, that takes place outside of a living cell, explains the 3-dimensional pattern of diffusion in the cytosol and the 1-dimensional diffusion along the DNA contour. After carrying out extensive research on processes occurring out of the cell, this mechanism was generally accepted but there was a need to verify that this mechanism could take place in vivo or inside of living cells. Bauer & Metzler (2013) therefore carried out an experiment using a bacterial genome in which they investigated the average time for TF – DNA binding to occur. After analyzing the process for the time it takes for TF's to diffuse across the contour and cytoplasm of the bacteria's DNA, it was concluded that in vitro and in vivo are similar in that the association and dissociation rates of TF's to and from the DNA are similar in both. Also, on the DNA contour, the motion is slower and target sites are easy to localize while in the cytoplasm, the motion is faster but the TF's are not sensitive to their targets and so binding is restricted.

Intracellular facilitated diffusion
Single-molecule imaging is an imaging technique which provides an ideal resolution necessary for the study of the Transcription factor binding mechanism in living cells. In prokaryotic bacteria cells such as E. coli, facilitated diffusion is required in order for regulatory proteins to locate and bind to target sites on DNA base pairs. There are 2 main steps involved: the protein binds to a non-specific site on the DNA and then it diffuses along the DNA chain until it locates a target site, a process referred to as sliding. According to Brackley et al. (2013), during the process of protein sliding, the protein searches the entire length of the DNA chain using 3-D and 1-D diffusion patterns. During 3-D diffusion, the high incidence of Crowder proteins creates an osmotic pressure which brings searcher proteins (e.g. Lac Repressor) closer to the DNA to increase their attraction and enable them to bind, as well as steric effect which exclude the Crowder proteins from this region (Lac operator region). Blocker proteins participate in 1-D diffusion only i.e. bind to and diffuse along the DNA contour and not in the cytosol.

Facilitated diffusion of proteins on Chromatin
The in vivo model mentioned above clearly explains 3-D and 1-D diffusion along the DNA strand and the binding of proteins to target sites on the chain. Just like prokaryotic cells, in eukaryotes, facilitated diffusion occurs in the nucleoplasm on chromatin filaments, accounted for by the switching dynamics of a protein when it is either bound to a chromatin thread or when freely diffusing in the nucleoplasm. In addition, given that the chromatin molecule is fragmented, its fractal properties need to be considered. After calculating the search time for a target protein, alternating between the 3-D and 1-D diffusion phases on the chromatin fractal structure, it was deduced that facilitated diffusion in eukaryotes precipitates the searching process and minimizes the searching time by increasing the DNA-protein affinity.

For oxygen
The oxygen affinity with hemoglobin on red blood cell surfaces enhances this bonding ability. In a system of facilitated diffusion of oxygen, there is a tight relationship between the ligand which is oxygen and the carrier which is either hemoglobin or myoglobin. This mechanism of facilitated diffusion of oxygen by hemoglobin or myoglobin was discovered and initiated by Wittenberg and Scholander. They carried out experiments to test for the steady-state of diffusion of oxygen at various pressures. Oxygen-facilitated diffusion occurs in a homogeneous environment where oxygen pressure can be relatively controlled. For oxygen diffusion to occur, there must be a full saturation pressure (more) on one side of the membrane and full reduced pressure (less) on the other side of the membrane i.e. one side of the membrane must be of higher concentration. During facilitated diffusion, hemoglobin increases the rate of constant diffusion of oxygen and facilitated diffusion occurs when oxyhemoglobin molecule is randomly displaced.

For carbon monoxide
Facilitated diffusion of carbon monoxide is similar to that of oxygen. Carbon monoxide also combines with hemoglobin and myoglobin, but carbon monoxide has a dissociation velocity that 100 times less than that of oxygen. Its affinity for myoglobin is 40 times higher and 250 times higher for hemoglobin, compared to oxygen.

For glucose
Since glucose is a large molecule, its diffusion across a membrane is difficult. Hence, it diffuses across membranes through facilitated diffusion, down the concentration gradient. The carrier protein at the membrane binds to the glucose and alters its shape such that it can easily to be transported. Movement of glucose into the cell could be rapid or slow depending on the number of membrane-spanning protein. It is transported against the concentration gradient by a dependent glucose symporter which provides a driving force to other glucose molecules in the cells. Facilitated diffusion helps in the release of accumulated glucose into the extracellular space adjacent to the blood capillary.

title: Facilitated diffusion


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McDonnell Douglas F-15 Eagle

The McDonnell Douglas F-15 Eagle is an American twin-engine, all-weather fighter aircraft designed by McDonnell Douglas (now part of Boeing). Following reviews of proposals, the United States Air Force (USAF) selected McDonnell Douglas's design in 1969 to meet the service's need for a dedicated air superiority fighter. The Eagle first flew in July 1972, and entered service in 1976. It is among the most successful modern fighters, with over 100 victories and no losses in aerial combat, with the majority of the kills by the Israeli Air Force.

The Eagle has been exported to many countries, including Israel, Japan, and Saudi Arabia. Although the F-15 was originally envisioned as a pure air superiority fighter, its design included a secondary ground-attack capability that was largely unused. It proved flexible enough that an improved all-weather strike derivative, the F-15E Strike Eagle, was later developed, entered service in 1989 and has been exported to several nations. Several additional F-15 variants have been produced.

The USAF had planned to replace all of its air superiority F-15s with the F-22 Raptor by the 2010s, but the severely reduced F-22 procurement forced the service to operate some F-15C/Ds until 2026 and replace them with newly built F-15EX Eagle II in order to retain an adequate number of air superiority fighters. The F-15E Strike Eagle is expected to continue operating in the USAF into the 2030s. The F-15 is in service with numerous countries, with production of enhanced variants ongoing.

Early studies
The F-15 can trace its origins to the early Vietnam War, when the U.S. Air Force and U.S. Navy fought each other over future tactical aircraft. Defense Secretary Robert McNamara was pressing for both services to use as many common aircraft as possible, even if performance compromises were involved. As part of this policy, the USAF and Navy had embarked on the TFX (F-111) program, aiming to deliver a medium-range interdiction aircraft for the Air Force that would also serve as a long-range interceptor aircraft for the Navy.

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. Several existing designs could fill this role; the Navy favored the Douglas A-4 Skyhawk and LTV A-7 Corsair II, which were pure attack aircraft, while the Air Force was more interested in the Northrop F-5 fighter with a secondary attack capability. The A-4 and A-7 were more capable in the attack role, while the F-5 less so, but could defend itself. If the Air Force chose a pure attack design, maintaining air superiority would be a priority for a new airframe. 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 reinforced after the loss of two Republic F-105 Thunderchief aircraft to obsolete MiG-17s attacking the Thanh Hóa Bridge on 4 April 1965.

In April 1965, Harold Brown, at that time director of the Department of Defense Research and Engineering, stated the favored position was to consider the F-5 and begin studies of an "F-X". 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. On 1 August, General Gabriel Disosway took command of Tactical Air Command and reiterated calls for the F-X, but lowered the required performance from Mach 3.0 to 2.5 to lower costs.

An official requirements document for an air superiority fighter was finalized in October 1965, and sent out as a request for proposals to 13 companies on 8 December. Meanwhile, the Air Force chose the A-7 over the F-5 for the support role on 5 November 1965, giving further impetus for an air superiority design as the A-7 lacked any credible air-to-air capability.

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, weight over 60000 lb, included a top speed of Mach 2.7 and a thrust-to-weight ratio of 0.75. When the proposals were studied in July 1966, the aircraft were roughly the size and weight of the TFX F-111, and like that aircraft, were designs that could not be considered an air-superiority fighter.

Smaller, lighter

Through this period, studies of combat over Vietnam were producing worrying results. Theory had stressed long-range combat using missiles and optimized aircraft for this role. The result was highly loaded aircraft with large radar 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, USN, 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.

In practice, due to policy and practical reasons, aircraft were closing to visual range and maneuvering, placing the larger US aircraft at a disadvantage to the much less expensive day fighters such as the MiG-21. Missiles proved to be much less reliable than predicted, especially at close range. Although improved training and the introduction of the M61 Vulcan cannon on the F-4 did much to address the disparity, these early outcomes led to considerable re-evaluation of the 1963 Project Forecast doctrine. This led to John Boyd's energy–maneuverability 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 to ensure air superiority. In early 1967, they proposed that the ideal design had a thrust-to-weight ratio near 1:1, a maximum speed further reduced to Mach 2.3, a weight of 40000 lb, and a wing loading of 80 lb/sqft.

By this time, the Navy had decided the F-111 would not meet their requirements and began the development of a new dedicated fighter design, the VFAX program. In May 1966, McNamara again asked the forces to study the designs and see whether the VFAX would meet the Air Force's F-X needs. The resulting studies took 18 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.

Focus on air superiority
In 1967, the Soviet Union revealed the Mikoyan-Gurevich MiG-25 at the Domodedovo airfield near Moscow. The MiG-25 was designed as a high-speed, high-altitude interceptor aircraft, and made many performance tradeoffs to excel in this role. Among these was the requirement for very high speed, over Mach 2.8, which demanded the use of stainless steel instead of aluminum for many parts of 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 the MiG-25 appeared to be superior in speed, ceiling, and endurance to all existing US fighters, even the F-X. Thus, an effort to improve the F-X followed.

Both Headquarters USAF and 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 for a smaller and more maneuverable design known as VFX, later becoming the Grumman F-14 Tomcat. VFX was considerably closer to the evolving F-X requirements. The Air Force in-fighting was 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".

In September 1968, a request for proposals was released to major aerospace companies. These requirements called for single-seat fighter having a maximum take-off weight of 40000 lb 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. It also called for a twin-engined arrangement, as this was believed to 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 whether to build a larger aircraft with a powerful radar that could detect the enemy at longer ranges was not clear, or alternatively a smaller aircraft that would make detecting it more difficult for the enemy.

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; like the Navy's VFX, the F-X skipped much of the prototype phase and jumped straight into full-scale development to save time and avoid potential program cancellation. 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.

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 airframe was designed with a 4,000 hour service life, although this was later increased through testing and extension modifications to 8,000 hours and some would fly beyond that. 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.

The F-15 has a "look-down/shoot-down" radar that can distinguish low-flying moving targets from ground clutter. It 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".

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.

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. These models were fitted with the Production Eagle Package (PEP 2000), which included 2000 lb of additional internal fuel, provisions for exterior conformal fuel tanks (CFT), and an increased maximum takeoff weight up to 68000 lb. 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, and an overload warning system, which allows the pilot to fly up to 9 g at all weights.

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 (see below); 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. Also 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. In 2000, the APG-63(V)2 active electronically scanned array (AESA) radar was retrofitted to 18 U.S. Air Force F-15C aircraft. The ZAP (Zone Acquisition Program) missile launch envelope has been integrated into the operational flight program system of all U.S. F-15 aircraft, providing dynamic launch zone and launch acceptability region information for missiles to the pilot by display cues in real-time.

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 F-15E strike variant was selected for production over General Dynamics' competing F-16XL in 1984; it 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 multipurpose 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. 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. The F-15E would be developed into the F-15 Advanced Eagle family, which features fly-by-wire controls; the Advanced Eagle is currently the basis of all current F-15 production.

Beginning in 2006, with the threat of curtailed procurement of the F-22 that was to replace all air superiority F-15s, USAF planned to modernize 179 F-15Cs in the best material condition in order to maintain fighter fleet size by retrofitting the AN/APG-63(V)3 AESA radar and updated cockpit displays; the first upgraded aircraft was delivered in October 2010. A significant number of F-15s were equipped with the Joint Helmet Mounted Cueing System. Lockheed Martin developed an infrared search and track (IRST) sensor system for tactical fighters such the F-15C, eventually resulting in the AN/ASG-34(V)1 IRST21 sensor mounted in the Legion Pod; the AN/AAQ-33 Sniper XR pod was also integrated as a makeshift interim IRST solution. A follow-on upgrade called the Eagle Passive/Active Warning Survivability System (EPAWSS) was planned. Boeing was selected in October 2015 to serve as prime contractor for the EPAWSS, with BAE Systems selected as a 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 were planned to have the system installed.

In September 2015, Boeing unveiled its 2040C Eagle upgrade (also called "Golden Eagle"), 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 fifth-generation fighters, the APG-63(V)3 AESA radar, long-range Legion IRST pod, and EPAWSS electronic warfare suite. The 2040C upgrade for the F-15C/D was not pursued, owing to the airframes' age that made it not economically sustainable, but many of the components such as EPAWSS and AESA radar were continued for F-15E upgrades as well as new-build F-15EX Eagle II ordered by USAF in 2020; the F-15EX took advantage of existing Advanced Eagle production line for export customers to minimize lead times and start-up costs to replace the remaining F-15C/Ds, whereas F-22 production restart was considered cost-prohibitive.

Overview

The F-15 has an all-metal semi-monocoque fuselage with a large-cantilever, shoulder-mounted wing. The wing planform of the F-15 suggests a modified cropped delta shape with a leading-edge sweepback angle of 45°. Ailerons and a simple high-lift flap are located on the trailing edge. No leading-edge maneuvering flaps are used. This complication was avoided by the combination of low wing loading and fixed leading-edge conical camber that varies with spanwise position along the wing. Airfoil thickness ratios vary from 6% at the root to 3% at the tip.

The empennage is of metal and composite construction, with twin aluminum/composite material honeycomb structure vertical stabilizers with boron-composite skin, resulting in an exceptionally thin tailplane and rudders. Composite horizontal all-moving tails outboard of the vertical stabilizers move independently to provide roll control in some flight maneuvers. 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 and fed by rectangular inlets with variable intake ramps. The cockpit is mounted high in the forward fuselage with a one-piece windscreen and large canopy for increased visibility and a 360° field of view for the pilot. 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 30000 ft in around 60 seconds. At certain speeds, the dynamic thrust output of the dual engines is greater than the aircraft's combat weight and drag, so it has the ability to accelerate vertically. The weapons and flight-control systems are designed so that one person can safely and effectively perform air-to-air combat. 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, although they are also fully combat capable. 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. Following problems during development of its exhaust petal design, including dislodgment during flight, the decision was made to remove them, resulting in a 3% aerodynamic drag increase.

The F-15 was shown to be capable of controlled flight with only one wing after an Israeli F-15D suffered a mid-air collision with an A-4 Skyhawk that removed most of the right-wing, in the 1983 Negev mid-air collision. While the A-4 was instantly disintegrated with the pilot being automatically ejected, the F-15 was sent into an uncontrollable roll. Through the application of full afterburner as well as a landing at twice the normal speed, pilot Zivi Nedivi managed to land successfully at Ramon Airbase. Subsequent wind-tunnel tests on a one-wing model confirmed that controllable flight was only possible within a very limited speed range of +/- 20 knots and angle of attack variation of +/- 20 degrees. The event resulted in research into damage adaptive technology and a system called "Intelligent Flight Control System".

Avionics

A multimission avionics system includes a head-up display (HUD), advanced radar, AN/ASN-109 inertial guidance system, flight instruments, ultra high frequency communications, and tactical air navigation system and instrument landing system receivers. It also has an internally mounted, tactical electronic warfare system, Identification friend or foe system, an electronic countermeasures suite, and a central digital computer.

The HUD projects 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.

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 mi. 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.

The improved APG-63(V)2 and (V)3 active electronically scanned array (AESA) radar upgrade included most of the hardware from the APG-63(V)1, but added an AESA to provide increased pilot situation awareness. The AESA radar has an exceptionally agile beam, providing nearly instantaneous track updates and enhanced multitarget tracking capability. The APG-63(V)2 and (V)3 are compatible with current F-15C weapon loads and enable pilots to take full advantage of AIM-120 AMRAAM capabilities, simultaneously guiding multiple missiles to several targets widely spaced in azimuth, elevation, or range.

Weaponry and external stores

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 selected weapon automatically appears on the head-up display.

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 mm M61 Vulcan Gatling gun in the right wing root.

Low-drag conformal fuel tanks (CFTs), initially called Fuel And Sensor Tactical (FAST) packs, 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. These tanks slightly degrade performance by increasing aerodynamic drag and cannot be jettisoned in-flight. However, they cause less drag than conventional external tanks. Each conformal tank can hold 750 U.S. gallons (2,840 L) of fuel. These CFTs 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 CFTs. The USAF 57th Fighter-Interceptor Squadron based at NAS Keflavik, 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.

Introduction and early service
The largest operator of the F-15 is the United States Air Force. The first Eagle, an F-15B, was delivered on 13 November 1974. In January 1976, the first Eagle destined for a combat squadron, the 555th TFS, was delivered. 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. During IAF raids against Palestinian factions in Lebanon in 1979–1981, F-15As reportedly downed 13 Syrian MiG-21s and two Syrian MiG-25s. 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-21s and 17 MiG-23s, and one Aérospatiale SA.342L Gazelle helicopter). During Operation Mole Cricket 19, Israeli F-15s and F-16s together shot down 82 Syrian fighters (MiG-21s, MiG-23s, and MiG-23Ms) without losses.

Israel was the only operator to use and develop the air-to-ground abilities of the air-superiority F-15 variants, doing so because the fighter's range was well beyond other combat aircraft in the 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 one GBU-15 guided bomb per aircraft and two F-15Cs restriking the ruins with six Mk-82 unguided bombs each. This was one of the few times air-superiority F-15s (A/B/C/D models) were used in tactical strike missions. 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.

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.

Anti-satellite trials

The ASM-135 missile was designed to be a standoff antisatellite (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. The launch aircraft executed a Mach 1.22, 3.8 g climb at 65° to release the ASAT missile at an altitude of 38100 ft. 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 mi orbit, which was destroyed by kinetic energy. The pilot, USAF Major Wilbert D. "Doug" Pearson, became the only pilot to destroy a satellite. The ASAT program involved five test launches. The program was officially terminated in 1988.

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 the Gulf War, the F-15 accounted for 36 of the 39 air-to-air victories by the U.S. Air Force against Iraqi forces. Iraq has confirmed the loss of 23 of its aircraft in air-to-air combat. 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. 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 Mikoyan MiG-29s, two MiG-25s, eight MiG-23s, two MiG-21s, two Sukhoi Su-25s, four Sukhoi Su-22s, one Sukhoi Su-7, six Dassault Mirage F1s, one Ilyushin Il-76 cargo aircraft, one Pilatus PC-9 trainer, and two Mil Mi-8 helicopters. According to NHHC, F-15s may have also shot down a friendly F-14 Tomcat. In addition, the F-15E achieved its first-ever air-to-air kill on 14 February 1991, destroying an Iraqi Mi-24 "Hind" helicopter with a GBU-10 laser-guided bomb. 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 American aircraft. Two F-15Es were lost to ground fire, and another was damaged on the ground by a Scud strike on King Abdulaziz Air Base.

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$40 million (~$ in ) for return of the aircraft three months later. RSAF F-15s shot down two Iraqi Mirage F1s during the Operation Desert storm. One Saudi Arabian F-15C was lost to a crash during the Persian Gulf War in 1991. The IQAF claimed this fighter was part of two USAF F-15Cs that engaged two Iraqi MiG-25PDs, and was hit by an R-40 missile before crashing.

They have since been deployed to support Operation Southern Watch, the patrolling of the Iraqi no-fly zones 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. USAF F-15Cs shot down four Yugoslav MiG-29s using AIM-120 and AIM-7 Radar guided missiles during NATO's 1999 intervention in Kosovo, Operation Allied Force.

Structural defects
All F-15s were grounded by the USAF 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 USAF reported on 28 November 2007 that a critical location in the upper longerons on the F-15C was the failure's suspected cause, causing the fuselage forward of the air intakes, including the cockpit and radome, to separate from the airframe.

F-15A through D-model aircraft were grounded until the location received detailed inspections and repairs as needed. The grounding of F-15s received media attention as it began to place strains on the nation's air-defense efforts. 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.

On 8 January 2008, the USAF Air Combat Command (ACC) cleared a portion of its older F-15 fleet for return to flying status. It also recommended a limited return to flight for units worldwide using the affected models. The accident review board report, which was released on 10 January 2008, 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. In a report released on 10 January 2008, nine other F-15s were identified to have similar problems in the longeron. As a result, General John D. W. Corley stated, "the long-term future of the F-15 is in question". 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/Ds.

Later service

The F-15 had a combined air-to-air combat record of 104 kills to no losses. The F-15's air superiority versions, the A/B/C/D models, have not suffered any losses to enemy action. 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. With the retirement of those early models, the F-15C and D models continued operational service to supplement the new F-22 Raptor in frontline US service. Because the DOD was primarily focused on asymmetric counterinsurgency warfare in the Middle East in the 2000s, the F-22 procurement was curtailed to just 187 operational aircraft and the USAF had to extend F-15C/D operations well beyond its planned retirement date in order to maintain adequate numbers of air superiority fighters; in 2007, the USAF planned to keep 179 F-15C/Ds along with 224 F-15Es in service beyond 2025. During the 2010s, USAF F-15C/Ds were regularly based overseas with the Pacific Air Forces at Kadena AB in Japan and with the U.S. Air Forces in Europe at RAF Lakenheath in the United Kingdom. Other regular USAF F-15s are operated by ACC as adversary/aggressor platforms at Nellis AFB, Nevada, and by Air Force Materiel Command in test and evaluation roles at Edwards AFB, California, and Eglin AFB, Florida. All remaining combat-coded F-15C/Ds are operated by the Air National Guard.

To keep the F-15C/D viable, the fleet saw a series of upgrades, with 179 aircraft receiving the AN/APG-63(V)3 AESA radar starting in 2010 along with eventual addition of IRST pods and cockpit enhancements. However, problems with the aging fleet meant the F-15C faced cuts or retirement in the USAF's FY 2015 budget in response to sequestration. By the mid 2010s, the aging F-15C/D fleet was no longer economically sustainable to the 2030s as hoped, and the USAF chose to forgo the more comprehensive F-15 2040C upgrade proposed by Boeing; in April 2017, USAF officials announced plans to retire the F-15C/D in the mid-2020s and press other aircraft such as F-16s into roles occupied by the F-15 while exploring options to recapitalize its fighter fleet.

In late 2018 and early 2019, following a series of DoD Cost Analysis and Program Evaluation (CAPE) Office studies on affordably recapitalizing the fighter fleet, the Pentagon in its FY 2020 budget requested new-build F-15EXs — an advanced variant based on the export F-15QA then in production — to replace the F-15Cs and supplement the F-22s to maintain fighter fleet size, with planned total procurement of 144 aircraft. This allowed USAF to use the existing export production line to quickly and affordably bring fighters into operational service, as restarting the F-22 line was considered cost-prohibitive. In 2022, it was announced the USAF plan to retire their fleet of F-15C/Ds by 2026, while the F-15Es would retire in the 2030s.

Yemen Civil War
During the Yemeni Civil War (2015–present), Houthis have used R-27T missiles modified to serve as surface-to-air missiles. A video released on 7 January 2018 also shows a modified R-27T hitting a Saudi F-15 on a forward-looking infrared camera. Houthi sources claim to have downed the F-15, although this has been disputed, as the missile apparently proximity detonated, though the F-15 continued to fly in its trajectory seemingly unaffected. Rebels later released footage showing an aircraft wreck, but serial numbers on the wreckage suggested the aircraft was a Panavia Tornado, also operated by Saudi forces. On 8 January, the Saudi admitted the loss of an aircraft but due to technical reasons.

On 21 March 2018, Houthi rebels released a video where they hit and possibly shot down a Saudi F-15 in Saada province. In the video a R-27T air-to-air missile adapted for surface-to-air use was launched and appeared to hit a jet. As in the video of the previous similar hit recorded on 8 January, the target, while clearly hit, did not appear to be downed. Saudi forces confirmed the hit, while saying the jet landed at a Saudi base. Saudi official sources confirmed the incident, reporting that it happened at 3:48 pm local time after a surface-to-air defense missile was launched at the fighter jet from inside Saada airport.

After the Houthi attack on Saudi oil infrastructure on 14 September 2019, Saudi Arabia tasked F-15 fighters armed with missiles to intercept low flying drones, difficult to intercept with ground-based high altitude missile systems like the MIM-104 Patriot with several drones being downed since then. On 2 July 2020, a Saudi F-15 shot down two Houthi Shahed 129 drones above Yemen. On 7 March 2021, during a Houthi attack at several Saudi oil installations, Saudi F-15s shot down several attacking drones using heatseeking AIM-9 Sidewinder missiles, with video evidence showing at least two Samad-3 UAVs and one Qasef-2K downed. On 30 March 2021, a video made by Saudi border guards showed a Saudi F-15 shooting down a Houthi Quasef-2K drone with an AIM-120 AMRAAM fired at short range.

Basic models

 * F-15A
 * Single-seat all-weather air-superiority fighter version, 384 built in 1972–1979

 * F-15B
 * Two-seat training version, formerly designated TF-15A, 61 built in 1972–1979

 * F-15C
 * Improved single-seat all-weather air-superiority fighter version, 483 built in 1979–1985. 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 in 1979–1985.

 * 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 in 1981–1997, two built in St. Louis.

 * 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 in the period 1981–1997.

 * 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 to be "riskier" technology program, the Grumman F-14 Tomcat. It did not have a long-range radar or the long-range missiles used by the F-14. The F-15N-PHX was another proposed naval version capable of carrying the AIM-54 Phoenix missile, but with an enhanced version of the AN/APG-63 radar on the F-15A. These featured folding wingtips, reinforced landing gear and a stronger tailhook for shipboard operation.

 * F-15 2040C
 * 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 and Israel, 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, Eagle Passive/Active Warning Survivability System (EPAWSS), conformal fuel tanks, upgraded APG-63(V)3 AESA radar and a "Talon HATE" communications pod allowing data transfer with the F-22. This upgrade program was not pursued due to the age of the existing airframes, but some of the upgrades were applied to the new-build F-15EX.

Strike Eagle derivatives

 * F-15E Strike Eagle
 * Two-seat all-weather multirole strike version, fitted with conformal fuel tanks. It was developed into the F-15I, F-15S, F-15K, F-15SG, and is the basis of the F-15 Advanced Eagle family. Over 400 F-15E and derivative variants produced since 1985.

 * F-15 Advanced Eagle
 * Further development of the F-15E with revised wing structure and digital fly-by-wire and is the basis for the F-15SA, F-15QA, F-15EX, and other variants. Current production baseline.

 * F-15SE Silent Eagle
 * A proposed F-15E variant from March 2009 with a reduced radar cross-section via changes such as replacing conformal fuel tanks with conformal weapons bays and canting the twin vertical tails 15 degrees outward, which would reduce their radar signature while providing a slight boost to lift to help offset the loss of conformal fuel tanks.

 * F-15EX Eagle II
 * Two-seat Advanced Eagle version for the USAF, can be fitted with conformal fuel tanks.

Prototypes

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 Serial 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-63 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

 * 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. Undergoing restoration in 2023 to be put on display in 2024.

 * 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. 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).

 * 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.

 * 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.

 * 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. Notable experiments include 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). 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.

Operators

This article only covers the F-15A, B, C, D, and related variants. For the operators of other F-15E-based variants, like the F-15E, F-15I, F-15S, F-15K, F-15SG, or F-15EX, see McDonnell Douglas F-15E Strike Eagle.

 * Israeli Air Force has operated F-15s since 1977. The IAF operates 38 F-15A, 6 F-15B, 16 F-15C and 11 F-15D in service as of 2022.
 * Israeli Air Force has operated F-15s since 1977. The IAF operates 38 F-15A, 6 F-15B, 16 F-15C and 11 F-15D in service as of 2022.
 * Japan Air Self-Defense Force operates 155 Mitsubishi F-15J and 44 F-15DJ fighters produced under license by Mitsubishi Heavy Industries.
 * Royal Saudi Air Force has 46 F-15C and 16 F-15D fighters in operation as of 2024.
 * United States Air Force operates 168 F-15C and 18 F-15D total aircraft as of mid-2022.
 * NASA currently operates one F-15B #836 as a test bed for a variety of flight research experiments and two F-15D, #884 and #897, for research support and pilot proficiency. NASA in the past used an F-15B #835 to test Highly Integrated Digital Engine Control system (HIDEC) at Edwards AFB in 1988.
 * United States Air Force operates 168 F-15C and 18 F-15D total aircraft as of mid-2022.
 * NASA currently operates one F-15B #836 as a test bed for a variety of flight research experiments and two F-15D, #884 and #897, for research support and pilot proficiency. NASA in the past used an F-15B #835 to test Highly Integrated Digital Engine Control system (HIDEC) at Edwards AFB in 1988.
 * NASA currently operates one F-15B #836 as a test bed for a variety of flight research experiments and two F-15D, #884 and #897, for research support and pilot proficiency. NASA in the past used an F-15B #835 to test Highly Integrated Digital Engine Control system (HIDEC) at Edwards AFB in 1988.

Notable accidents

A total of 175 F-15s have been lost to non-combat causes as of June 2016. However, the F-15 aircraft is very reliable with only 1 loss per 50,000 flight hours.
 * On 1 May 1983, an Israeli Air Force F-15D collided mid-air with an A-4 Skyhawk during a training flight, causing the F-15's right wing to shear off almost completely. Despite the damage, the pilot was able to reach a nearby airbase and land safely – albeit at twice the normal landing speed. The aircraft was subsequently repaired and saw further combat action.
 * On 26 March 2001, two US Air Force F-15Cs crashed near the summit of Ben Macdui in the Cairngorms during a low flying training exercise over the Scottish Highlands. Both Lieutenant Colonel Kenneth John Hyvonen and Captain Kirk Jones died in the accident, which resulted in a court martial for an RAF air traffic controller, who was later found not guilty.
 * On 2 November 2007, a 27-year-old F-15C (AF Ser. No. 80-0034) of the 131st Fighter Wing, Missouri Air National Guard, crashed following an in-flight breakup due to structural failure during combat training near St. Louis, Missouri. The pilot, Major Stephen W. Stilwell, ejected but suffered serious injuries. On 3 November 2007, all non-mission critical F-15s were grounded pending the crash investigation's outcome. By 13 November 2007, over 1,100 F-15s were grounded worldwide after Israel, Japan and Saudi Arabia grounded their aircraft as well. F-15Es were cleared on 15 November 2007 pending individual inspections. On 8 January 2008, the USAF cleared 60 percent of the F-15A/B/C/D fleet to fly. On 10 January 2008, the accident review board released its report, which attributed the crash to the longeron not meeting specifications. On 15 February 2008, the Air Force cleared all F-15s for flight, pending inspections and any needed repairs. In March 2008, Stilwell filed a lawsuit against Boeing which was later dismissed in April 2009.

Aircraft on display
Although the F-15 continues to be in use, a number of older USAF and IAF models have been retired, with several placed on outdoor display or in museums.

Germany
F-15A
 * 74-0085 – Spangdahlem AB
 * 74-0109 – Auto Technik Museum, Speyer

Netherlands
F-15A
 * 74-0083 (marked as 77–0132) – Nationaal Militair Museum, Kamp Zeist, former Camp New Amsterdam AB. Aircraft was based at Camp New Amsterdam and left as a gift when the base was closed in 1995.

Japan
F-15A
 * 74-0088 – Kadena AB

Israel
F-15A
 * 73-0098 – Israeli Air Museum, Hatzerim
 * 73-0107 – gate guard at Tel Nof AB

Saudi Arabia
F-15B
 * 71-0291 - painted in false Saudi markings as '1315' at Royal Saudi Air Force Museum

United Kingdom
F-15A
 * 74-0131 – Wings of Liberty Memorial Park, RAF Lakenheath
 * 76-0020 – American Air Museum, Duxford

F-15A

 * 71-0280 – 37th Training Wing HQ Parade Ground, Kelly Field (formerly Kelly AFB), San Antonio, Texas
 * 71-0281 – Tactical Air Command Memorial Park, Joint Base Langley-Eustis, Hampton, Virginia
 * 71-0283 – Defense Supply Center Richmond, Richmond, Virginia
 * 71-0285 – Boeing Avionic Antenna Laboratory, St. Charles, Missouri
 * 71-0286 – A GF-15A; Saint Louis Science Center, St. Louis, Missouri, in storage. Previously on display at Octave Chanute Aerospace Museum, Rantoul, Illinois
 * 72-0119 "Streak Eagle" – at the National Museum of the United States Air Force, Wright-Patterson AFB, Dayton, Ohio
 * 73-0085 – Museum of Aviation, Robins AFB, Warner Robins, Georgia
 * 73-0086 – Louisiana Military Museum, Jackson Barracks, New Orleans, Louisiana
 * 73-0099 – Robins AFB, Warner Robins, Georgia
 * 74-0081 – Elmendorf AFB, Alaska
 * 74-0084 – Alaska Aviation Heritage Museum, Anchorage, Alaska
 * 74-0095 – Tyndall AFB, Panama City, Florida This aircraft was flipped and severely damaged by Hurricane Michael in October 2018.
 * 74-0114 – Mountain Home AFB, Idaho
 * 74-0117 – Langley AFB, Virginia
 * 74-0118 – Pima Air & Space Museum, Tucson, Arizona
 * 74-0119 – Castle Air Museum, Atwater, California
 * 74-0124 – Air Force Armament Museum, Eglin AFB, Florida
 * 75-0026 – National Warplane Museum, Elmira Corning Regional Airport, New York
 * 75-0033 – Eglin Parkway entrance to 33d Fighter Wing complex, Eglin AFB, Florida
 * 75-0045 – USS Alabama Battleship Memorial Park, Mobile, Alabama
 * 76-0008 – March Field Air Museum at March ARB, Riverside, California
 * 76-0009 – Kingsley Field Air National Guard Base, Klamath Falls, Oregon
 * 76-0012 – Air Heritage Aviation Museum, Beaver County Airport, Beaver Falls, Pennsylvania
 * 76-0014 – Evergreen Aviation Museum, McMinnville, Oregon
 * 76-0018 – Hickam Field, Joint Base Pearl Harbor–Hickam, Oahu, Hawaii
 * 76-0024 – Peterson Air and Space Museum, Peterson AFB, Colorado
 * 76-0027 – National Museum of the United States Air Force, Wright-Patterson AFB, Dayton, Ohio
 * 76-0037 – Holloman AFB, New Mexico
 * 76-0040 – Otis ANGB, Cape Cod, Massachusetts
 * 76-0042 - United States Air Force Academy, Colorado Springs, Colorado
 * 76-0048 – McChord Air Museum, McChord AFB, Washington
 * 76-0057 - Nellis Air Force Base, Las Vegas, Nevada. Aircraft previously bore "Vegas Strong" paint scheme to honor victims of Oct 1, 2017 shooting.
 * 76-0063 – Pacific Aviation Museum, Ford Island, Joint Base Pearl Harbor–Hickam, Hawaii
 * 76-0066 – Portland Air National Guard Base, Oregon
 * 76-0067 – Dyess Air Force Base, Linear Air Park display area on base
 * 76-0076 (marked as 33rd Fighter Wing F-15C 85–0125) – roadside park, DeBary, Florida
 * 76-0080 – Jacksonville Air National Guard Base, Florida
 * 76-0088 – 131st Bomb Wing Heritage Park, Whiteman AFB, Missouri
 * 76-0108 – Lackland AFB/Kelly Field Annex, Texas
 * 76-0110 – gate guard, Mountain Home AFB, Idaho
 * 77-0068 – Arnold AFB, Manchester, Tennessee
 * 77-0084 – 412th Test Wing at Edwards Air Force Base, California and Nellis Air Force Base, Nevada
 * 77-0090 – Hill Aerospace Museum, Hill AFB, Utah
 * 77-0102 – Pacific Coast Air Museum, Charles M. Schulz-Sonoma County Airport, Santa Rosa, California. One of two Massachusetts Air National Guard 102d Fighter Wing aircraft scrambled in first response to terrorist air attacks on 11 September 2001
 * 77-0146 – Veterans Park, Callaway, Florida
 * 77-0150 – Yanks Air Museum, Chino, California

F-15B

 * 73-0108 – Luke AFB, Arizona
 * 73-0114 – Air Force Flight Test Center Museum, Edwards AFB, California
 * 75-0084 – Russell Military Museum, Russell, Illinois
 * 77-0154 - Sheppard Air Force Base, Witchita Falls, Texas
 * 77-0159 - Volk Field Air National Guard Base, Camp Douglas, Wisconsin
 * 77-0161 – Seymour Johnson AFB, Goldsboro, North Carolina

F-15C

 * 79-0022 – Pueblo Weisbrod Aircraft Museum, Pueblo, Colorado Credited with a MiG-23 kill during Operation Desert Storm while flown by Donald Watros. It is painted in the colors of the 22nd Fighter Squadron deployed from Bitburg AB, Germany, to Incirlik AB, Turkey.
 * 79-0078 – Museum of Aviation, Robins AFB, Warner Robins, Georgia Currently stored at the museum, it is awaiting restoration and display. Credited with two MiG-21 kills during Operation Desert Storm while flown by Thomas Dietz, while on deployment with 53rd Fighter Squadron to Al Kharj AB, Saudi Arabia from Bitburg AB, Germany
 * 80-0014 – Chico Air Museum, Chico, California; transported from Langley AFB, Virginia
 * 86-0156 - National Museum of the United States Air Force - On display in the Cold War Gallery. This aircraft scored two MiG-29 kills of the Yugoslavia Air Force during Operation Allied Force flown by Captain Jeff "Claw" Hwang of the 493rd Fighter Squadron, 48th Fighter Wing based at RAF Lakenheath, UK.

Notable appearances in media
The F-15 was the subject of the IMAX movie Fighter Pilot: Operation Red Flag, about the RED FLAG exercises. In Tom Clancy's nonfiction book, Fighter Wing: A Guided Tour of an Air Force Combat Wing (1995), a detailed analysis of the Air Force's premier fighter aircraft, the F-15 Eagle and its capabilities are showcased.

The F-15 has also been a popular subject as a toy, and a fictional likeness of an aircraft similar to the F-15 has been used in cartoons, books, video games, animated television series, and animated films.

title: McDonnell Douglas F-15 Eagle


text:
Talk:McDonnell Douglas F-15 Eagle

A Commons file used on this page or its Wikidata item has been nominated for deletion
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion: Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 21:09, 7 May 2023 (UTC)
 * Royal Saudi Air Forces F-15C.jpg

Is there nothing published about the F-15 avionics
Is there nothing published about the F-15 avionics, or is it classified ? Compare with F-14 CADC with recently unclassified description of MP944 chips involved. - Rod57 (talk) 22:07, 27 January 2024 (UTC)

F15I
The f15I is missing from the variants list. 176.230.98.161 (talk) 20:33, 1 February 2024 (UTC)

 * F-15I is based on the F-15E, see McDonnell Douglas F-15E Strike Eagle. -Fnlayson (talk) 20:45, 1 February 2024 (UTC)

Sea Eagle Stuff
The "Sea Eagle" should be called the "Seagle" or the "Seagull" (this is not a serious topic.) Taffy boeing b 17 (talk) 16:28, 9 February 2024 (UTC)

title: Talk:McDonnell Douglas F-15 Eagle