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27-678: Alpha ( Α or α ) is the first letter of the Greek alphabet. Alpha or ALPHA may also refer to: Alpha Alpha / ˈ æ l f ə / (uppercase Α , lowercase α ) is the first letter of the Greek alphabet . In the system of Greek numerals , it has a value of one. Alpha is derived from the Phoenician letter aleph [REDACTED] , which is the West Semitic word for " ox ". Letters that arose from alpha include

54-406: A compound in physical chemistry . It is also commonly used in mathematics in algebraic solutions representing quantities such as angles. Furthermore, in mathematics, the letter alpha is used to denote the area underneath a normal curve in statistics to denote significance level when proving null and alternative hypotheses . In ethology , it is used to name the dominant individual in

81-400: A is the Greek prefix ἁ- or ἀ- ha-, a- . It comes from Proto-Indo-European * sm̥ . The letter alpha represents various concepts in physics and chemistry , including alpha radiation , angular acceleration , alpha particles , alpha carbon and strength of electromagnetic interaction (as fine-structure constant ). Alpha also stands for thermal expansion coefficient of

108-455: A group of animals. In aerodynamics, the letter is used as a symbol for the angle of attack of an aircraft and the word "alpha" is used as a synonym for this property. In mathematical logic , α is sometimes used as a placeholder for ordinal numbers . The proportionality operator " ∝ " (in Unicode : U+221D) is sometimes mistaken for alpha. The uppercase letter alpha is not generally used as

135-441: A horizontal line on the fuselage as the reference line (and also as the longitudinal axis). Some authors do not use an arbitrary chord line but use the zero lift axis where, by definition, zero angle of attack corresponds to zero coefficient of lift . Some British authors have used the term angle of incidence instead of angle of attack. However, this can lead to confusion with the term riggers' angle of incidence meaning

162-430: A lower, flatter curve with a higher critical angle. The critical angle of attack is the angle of attack which produces the maximum lift coefficient. This is also called the " stall angle of attack". Below the critical angle of attack, as the angle of attack decreases, the lift coefficient decreases. Conversely, above the critical angle of attack, as the angle of attack increases, the air begins to flow less smoothly over

189-470: A maximum angle of attack is reached, regardless of pilot input. This is called the 'angle of attack limiter' or 'alpha limiter'. Modern airliners that have fly-by-wire technology avoid the critical angle of attack by means of software in the computer systems that govern the flight control surfaces. In takeoff and landing operations from short runways ( STOL ), such as Naval Aircraft Carrier operations and STOL backcountry flying, aircraft may be equipped with

216-615: A symbol because it tends to be rendered identically to the uppercase Latin A . In the International Phonetic Alphabet , the letter ɑ, which looks similar to the lower-case alpha, represents the open back unrounded vowel . The Phoenician alphabet was adopted for Greek in the early 8th century BC, perhaps in Euboea . The majority of the letters of the Phoenician alphabet were adopted into Greek with much

243-456: Is only indirectly related to stall behavior. Some military aircraft are able to achieve controlled flight at very high angles of attack, but at the cost of massive induced drag . This provides the aircraft with great agility. A famous example is Pugachev's Cobra . Although the aircraft experiences high angles of attack throughout the maneuver, the aircraft is not capable of either aerodynamic directional control or maintaining level flight until

270-555: The Latin letter A and the Cyrillic letter А . In Ancient Greek , alpha was pronounced [ a ] and could be either phonemically long ([aː]) or short ([a]). Where there is ambiguity, long and short alpha are sometimes written with a macron and breve today: Ᾱᾱ, Ᾰᾰ . In Modern Greek , vowel length has been lost, and all instances of alpha simply represent the open front unrounded vowel IPA: [a] . In

297-454: The polytonic orthography of Greek, alpha, like other vowel letters, can occur with several diacritic marks: any of three accent symbols ( ά, ὰ, ᾶ ), and either of two breathing marks ( ἁ, ἀ ), as well as combinations of these. It can also combine with the iota subscript ( ᾳ ). In the Attic – Ionic dialect of Ancient Greek, long alpha [aː] fronted to [ ɛː ] ( eta ). In Ionic,

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324-403: The aircraft of speed very quickly due to induced drag, and, in extreme cases, increased frontal area and parasitic drag. Not only do such maneuvers slow the aircraft down, but they cause significant structural stress at high speed. Modern flight control systems tend to limit a fighter's angle of attack to well below its maximum aerodynamic limit. In sailing , the physical principles involved are

351-660: The alphabet. Ammonius asks Plutarch what he, being a Boeotian , has to say for Cadmus , the Phoenician who reputedly settled in Thebes and introduced the alphabet to Greece, placing alpha first because it is the Phoenician name for ox —which, unlike Hesiod , the Phoenicians considered not the second or third, but the first of all necessities. "Nothing at all," Plutarch replied. He then added that he would rather be assisted by Lamprias , his own grandfather, than by Dionysus ' grandfather, i.e. Cadmus. For Lamprias had said that

378-399: The angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. Since a wing can have twist, a chord line of the whole wing may not be definable, so an alternate reference line is simply defined. Often, the chord line of the root of the wing is chosen as the reference line. Another choice is to use

405-407: The angle between the chord of an airfoil and some fixed datum in the airplane. The lift coefficient of a fixed-wing aircraft varies with angle of attack. Increasing angle of attack is associated with increasing lift coefficient up to the maximum lift coefficient, after which lift coefficient decreases. As the angle of attack of a fixed-wing aircraft increases, separation of the airflow from

432-579: The angle of attack or Lift Reserve Indicators . These indicators measure the angle of attack (AOA) or the Potential of Wing Lift (POWL, or Lift Reserve) directly and help the pilot fly close to the stalling point with greater precision. STOL operations require the aircraft to be able to operate close to the critical angle of attack during landings and at the best angle of climb during takeoffs. Angle of attack indicators are used by pilots for maximum performance during these maneuvers, since airspeed information

459-412: The center of gravity of the aircraft and other factors. However, the aircraft normally stalls at the same critical angle of attack, unless icing conditions prevail. The critical or stalling angle of attack is typically around 15° - 18° for many airfoils. Some aircraft are equipped with a built-in flight computer that automatically prevents the aircraft from increasing the angle of attack any further when

486-450: The concept of dominant "alpha" members in groups of animals. All code points with ALPHA or ALFA but without WITH (for accented Greek characters, see Greek diacritics: Computer encoding ): These characters are used only as mathematical symbols. Stylized Greek text should be encoded using normal Greek letters, with markup and formatting to indicate text style: Angle of attack In aerodynamics , angle of attack specifies

513-468: The first articulate sound made is "alpha", because it is very plain and simple—the air coming off the mouth does not require any motion of the tongue—and therefore this is the first sound that children make. According to Plutarch's natural order of attribution of the vowels to the planets , alpha was connected with the Moon . As the first letter of the alphabet, Alpha as a Greek numeral came to represent

540-407: The low density of air in the upper atmosphere as well as at low speed at low altitude where the margin between level flight AoA and stall AoA is reduced. The high AoA capability of the aircraft provides a buffer for the pilot that makes stalling the airplane (which occurs when critical AoA is exceeded) more difficult. However, military aircraft usually do not obtain such high alpha in combat, as it robs

567-513: The maneuver ends. The Cobra is an example of supermaneuvering as the aircraft's wings are well beyond the critical angle of attack for most of the maneuver. Additional aerodynamic surfaces known as "high-lift devices" including leading edge wing root extensions allow fighter aircraft much greater flyable 'true' alpha, up to over 45°, compared to about 20° for aircraft without these devices. This can be helpful at high altitudes where even slight maneuvering may require high angles of attack due to

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594-470: The number 1 . Therefore, Alpha, both as a symbol and term, is used to refer to the "first", or "primary", or "principal" (most significant) occurrence or status of a thing. The New Testament has God declaring himself to be the "Alpha and Omega, the beginning and the end, the first and the last." ( Revelation 22:13 , KJV, and see also 1:8 ). Consequently, the term "alpha" has also come to be used to denote "primary" position in social hierarchy, examples being

621-461: The same sounds as they had had in Phoenician, but ʼāleph , the Phoenician letter representing the glottal stop [ʔ] , was adopted as representing the vowel [a] ; similarly, hē [h] and ʽayin [ʕ] are Phoenician consonants that became Greek vowels, epsilon [e] and omicron [o] , respectively. Plutarch , in Moralia , presents a discussion on why the letter alpha stands first in

648-571: The shift took place in all positions. In Attic, the shift did not take place after epsilon , iota , and rho ( ε, ι, ρ ; e, i, r ). In Doric and Aeolic , long alpha is preserved in all positions. Privative a is the Ancient Greek prefix ἀ- or ἀν- a-, an- , added to words to negate them. It originates from the Proto-Indo-European * n̥- ( syllabic nasal) and is cognate with English un- . Copulative

675-411: The upper surface flow becomes more fully separated and the lift coefficient reduces further. Above this critical angle of attack, the aircraft is said to be in a stall. A fixed-wing aircraft by definition is stalled at or above the critical angle of attack rather than at or below a particular airspeed . The airspeed at which the aircraft stalls varies with the weight of the aircraft, the load factor ,

702-422: The upper surface of the airfoil and begins to separate from the upper surface. On most airfoil shapes, as the angle of attack increases, the upper surface separation point of the flow moves from the trailing edge towards the leading edge. At the critical angle of attack, upper surface flow is more separated and the airfoil or wing is producing its maximum lift coefficient. As the angle of attack increases further,

729-480: The upper surface of the wing becomes more pronounced, leading to a reduction in the rate of increase of the lift coefficient. The figure shows a typical curve for a cambered straight wing. Cambered airfoils are curved such that they generate some lift at small negative angles of attack. A symmetrical wing has zero lift at 0 degrees angle of attack. The lift curve is also influenced by the wing shape, including its airfoil section and wing planform . A swept wing has

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