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63-600: Recognizing the limitations of the earlier Su-9 and Su-11 in intercepting the new Boeing B-52 Stratofortress , particularly in terms of radar and aircraft performance, the Sukhoi OKB quickly began the development of a heavily revised and more capable aircraft. A variety of development aircraft evolved, including the Sukhoi T-49 , which shared the fuselage of the Su-9 (including its single engine), but used cheek-mounted intakes to leave

126-508: A disturbance causes an aircraft to roll away from its normal wings-level position as in Figure 1, the aircraft will begin to move somewhat sideways toward the lower wing. In Figure 2, the airplane's flight path has started to move toward its left while the nose of the airplane is still pointing in the original direction. This means that the oncoming air is arriving somewhat from the left of the nose. The airplane now has sideslip angle in addition to

189-492: A greater or lesser degree. Wing sweepback also increases the dihedral effect, for roughly 1° of effective dihedral with every 10° of sweepback. This is one reason for anhedral configuration on aircraft with high sweep angle, as well as on some airliners, even on low-wing aircraft such as the Tu-134 and Tu-154 . In any case, wing sweepback can also occur with a dihedral configuration. For instance, two small biplanes produced from

252-469: A modest fuel capacity increase compared to the Su-7. The Su-9 was capable of Mach 1.8 at altitude or about Mach 1.14 with missiles. However, its fuel fraction remained minimal, and its operational radius was limited. Furthermore, rotation speeds were even higher than the Su-7, which was already high at 360  km/h (225  mph). Unlike the Su-7, which had cumbersome controls but docile handling characteristics,

315-412: A new world record for absolute height, at 28,852 m (94,658 ft). In November of the same year, Ilyushin set several new sustained speed/altitude records in the same aircraft. This record was later broken on December 6, 1959, by Commander Lawrence E. Flint Jr., who performed a zoom climb to a world record of 98,557 feet (30,040 meters) while piloting an F4H-1 Phantom . Bobrovka became

378-680: A new wing design with extended wingtips (increasing wing area) and boundary layer control . Su-15s with the new wing went into production in 1969. They were dubbed "Flagon-D" by NATO, although the Soviet designation was unchanged. Also in 1969 testing began of the upgraded Su-15T with the Volkov Taifun (" Typhoon ") radar, which was based on the MiG-25's powerful RP-25 Smerch-A ("Tornado") radar (NATO "Foxfire"). The Taifun proved troublesome, however, and ceased production after only 10 aircraft had been built. It

441-650: A significant part of the V-PVO's interceptor force, and was designed to intercept easier targets such as the American B-52 and U-2 and the British V bombers , leaving the more difficult targets such as the XB-70 and B-58 to the faster MiG-25P. The Taifun radar of the Su-15TM was optimised for counter-countermeasure operation, as opposed to range. As an interceptor, the task of the Su-15TM

504-419: A strong influence on the dihedral effect. Dihedral effect of an aircraft is a rolling moment resulting from the vehicle having a non-zero angle of sideslip . Increasing the dihedral angle of an aircraft increases the dihedral effect on it. However, many other aircraft parameters also have a strong influence on dihedral effect. Some of these important factors are: wing sweep , vertical center of gravity , and

567-514: A take-off speed of 395 km/h (245 mph) for early delta-winged 'Flagon-A's and 370 km/h (230 mph) for the larger-winged 'Flagon-F'. While the controls were responsive and precise, the aircraft was unforgiving of pilot error. Despite its powerful radar, the Su-15, like most Soviet interceptors before the late 1980s, was heavily dependent on ground control interception (GCI), with aircraft vectored onto targets by ground radar stations. It

630-618: Is a single- engine , all-weather, missile -armed interceptor aircraft developed by the Soviet Union . The Su-9 emerged from aerodynamic studies by TsAGI , the Soviet aerodynamic center, during the Korean War , which devised several optimum aerodynamic configurations for jet fighters. The design first flew in 1956 as the T-405 prototype. The Su-9 was developed at the same time as the Su-7 "Fitter" , and

693-475: Is caused by the center of lift and drag being further above the CG and having a longer moment arm. So, the same forces that change as sideslip changes (primarily sideforce, but also lift and drag) produce a larger moment about the CG of the aircraft. This is sometimes referred to as the pendulum effect . An extreme example of the effect of vertical CG on dihedral effect is a paraglider . The dihedral effect created by

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756-437: Is less-ambiguously termed "spiral mode stability" and dihedral effect is a contributing factor to it. The dihedral angle contributes to the total dihedral effect of the aircraft. In turn, the dihedral effect contributes to stability of the spiral mode . A stable spiral mode will cause the aircraft to eventually return to a nominally "wings level" bank angle when the angle of the wings is disturbed to become off-level. If

819-451: Is needed to get the amount of dihedral effect needed. Dihedral effect is defined simply to be the rolling moment caused by sideslip and nothing else. Rolling moments caused by other things that may be related to sideslip have different names. Dihedral effect is not caused by yaw rate , nor by the rate of sideslip change . Since dihedral effect is noticed by pilots when "rudder is applied", many pilots and other near-experts explain that

882-427: Is the balance point of an aircraft. If suspended at this point and allowed to rotate, a body (aircraft) will be balanced. The front-to-back location of the CG is of primary importance for the general stability of the aircraft, but the vertical location has important effects as well. The vertical location of the CG changes the amount of dihedral effect. As the "vertical CG" moves lower, dihedral effect increases. This

945-433: Is the upward angle from horizontal of the wings of a fixed-wing aircraft , or of any paired nominally-horizontal surfaces on any aircraft . The term can also apply to the wings of a bird . Dihedral angle is also used in some types of kites such as box kites. Wings with more than one angle change along the full span are said to be polyhedral . Dihedral angle has important stabilizing effects on flying bodies because it has

1008-424: Is the upward angle from horizontal of the wings or tailplane of a fixed-wing aircraft . "Anhedral angle" is the name given to negative dihedral angle, that is, when there is a downward angle from horizontal of the wings or tailplane of a fixed-wing aircraft. Dihedral angle has a strong influence on dihedral effect , which is named after it. Dihedral effect is the amount of roll moment produced in proportion to

1071-562: The Beriev Be-12 were designed with gull wings bent near the root. Others, such as the Vought F4U Corsair , used an inverted gull wing design, which allowed for shorter landing struts and extra ground clearance for large propellers and external payloads, such as external fuel tanks or bombs. Modern polyhedral wing designs generally bend upwards near the wingtips (also known as tip dihedral ), increasing dihedral effect without increasing

1134-521: The R-8/K-8 (AA-3 "Anab"; later R-98) air-to-air missile . Early models carried two missiles, but 'Flagon-D' and later versions could carry four. Like most Soviet missiles, the R-98 was made in both infrared and semi-active radar homing versions, and standard practice was to fire the weapons in pairs (one semi-active radar homing, one IR homing) to give the greatest chance of a successful hit. The IR homing missile

1197-422: The keel effect ) and so additional dihedral angle is often not required. Such designs can have excessive dihedral effect and so be excessively stable in the spiral mode, so anhedral angle on the wing is added to cancel out some of the dihedral effect so that the aircraft can be more easily maneuvered. Most aircraft have been designed with planar wings with simple dihedral (or anhedral). Some older aircraft such as

1260-510: The "Fishpot" had light and responsive controls but was unforgiving of pilot error. The Su-9 had primitive R1L ( NATO reporting name "High Fix") radar in the shock cone and was armed with four K-5 (AA-1 "Alkali") beam-riding air-to-air missiles . Like all beam-riders, the K-5 was so limited as to be nearly useless for air-to-air combat. Unlike the Su-7 and later Su-15 , Su-9 carried no cannon armament, although two fuselage pylons were reserved for

1323-411: The "leveling" direction more strongly, and less dihedral effect tries to roll the wings in the "leveling" direction less strongly. Dihedral effect helps stabilize the spiral mode by tending to roll the wings toward level in proportion to the amount of sideslip that builds up. It is not the whole picture however. At the same time that angle of sideslip is building up, the vertical fin is trying to turn

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1386-501: The 11th production series onward by a new double-delta wing of increased span and area, with a small wing fence above each outer pylon and blown flaps to improve landing characteristics. This was accompanied by a new tail of greater anhedral and a vertical fin of reduced height. The Su-15 had maximum speed of Mach 2.5 and a rate of climb of 228m/s (750 ft/s, 45,000 ft/min), a very important parameter for an interceptor aircraft . Take-off and landing speeds were comparatively high, with

1449-574: The 1930s to 1945 by Bücker Flugzeugbau in Germany, the Bücker Jungmann two-seat trainer and the Bücker Jungmeister aerobatic competition biplane, were designed with sweepbacks of approximately 11 degrees, which provided significant dihedral effect – in addition to their small dihedral angles having a similar but lesser effect. The center of mass , usually called the center of gravity or "CG",

1512-466: The 1970s. Some were retained as test vehicles or converted to remote-piloted vehicles for use as unmanned aerial vehicles . It was replaced by the upgraded Su-11 and the much-superior Su-15 "Flagon" and MiG-25 "Foxbat" . The combat record of the "Fishpot" is poorly documented. It is possible that it was involved in the interception (or even shoot-down) of reconnaissance missions, but no information has been publicly declassified. Being an interceptor,

1575-470: The Soviet Union's primary storage facility for the Su-9 as it was phased out, and by 1981 at least 243 Su-9 aircraft were observed parked at Bobrovka. The Su-9's fuselage and tail surfaces resembled those of the Su-7, but unlike the swept wing of that aircraft, the "Fishpot" used a 53° delta wing with conventional slab tailplanes . It shared Sukhoi features like the rear-fuselage air brakes as well as

1638-565: The Su-15, and the prototype first flew on 30 May 1962. It entered service testing 5 August 1963, but its service entry was delayed by political infighting with the Yakovlev OKB over production line capacity in Novosibirsk , which was also building the Yak-28P . The Su-15 proved to be superior in most respects other than range, and it was officially commissioned on 3 April 1965. Series production began

1701-519: The Su-15TM was also designated Su-21 and the Su-15UM Su-21U . These reports are apparently incorrect. Designation Su-21 was reserved for Su-17M4 but never used. Data from Wilson airwar.ru, Gordon General characteristics Performance Armament Avionics Related development Aircraft of comparable role, configuration, and era Related lists Sukhoi Su-9 The Sukhoi Su-9 ( ASCC reporting name : Fishpot )

1764-505: The Su-15UM (NATO "Flagon-G"), followed from 1976 . The final Su-15UMs, the last Su-15s produced, came off the line in 1979 . Various OKB proposals for upgraded Su-15s with better engines and aerodynamics to satisfy a VVS requirement for a long-range tactical fighter were rejected in favour of the Mikoyan MiG-23 fighter. Although many components of the Su-15 were similar or identical to

1827-478: The Su-7's Lyulka AL-7 turbojet engine and nose intake. The translating shock cone contains the radar set. The Su-9 was developed from earlier work on a developmental aircraft designated T-3, to which the Su-9 was nearly identical. Internally at Sukhoi, the Su-9 was known as the T-43. The delta wing of the Su-9 was adopted because of its lower drag in the supersonic flight regime. Its greater volume also allowed

1890-515: The Su-9 was used in routine patrols and interdictions over the Soviet Frontiers. The most widely known involved in the interception of Francis Gary Powers ' U-2 on Soviet territory on May 1, 1960. The Su-9 was unarmed and was directed to ram the U-2. One ramming attempt was made, but the Su-9 missed the U-2 due to the significant difference in the speed of the two planes. Due to the Su-9's lack of fuel,

1953-462: The V-PVO, especially once NATO switched to low-level penetration tactics. Even so, the Su-15 remained an important part of the V-PVO until the fall of the Soviet Union. As one of the V-PVO's principal interceptors, the Su-15 was involved in several attacks on foreign aircraft that inadvertently crossed into Soviet airspace: The Su-15 was also credited with shooting down five reconnaissance balloons sent to spy on Soviet territory in 1975. Although it

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2016-640: The West first saw both at the Tushino Aviation Day on June 24, 1956, where the Su-9 was dubbed Fitter-B . It entered service in 1959 . The total production of the Su-9 was about 1,100 aircraft. It is believed that at least some Su-9s were upgraded to Su-11 "Fishpot-C" form. None were exported to any of the USSR 's client states nor to the Warsaw Pact nations. The remaining Su-9s and later Su-11s were retired during

2079-412: The amount of sideslip . Dihedral effect is a critical factor in the stability of an aircraft about the roll axis (the spiral mode ). It is also pertinent to the nature of an aircraft's Dutch roll oscillation and to maneuverability about the roll axis. Longitudinal dihedral is a comparatively obscure term related to the pitch axis of an airplane. It is the angle between the zero-lift axis of

2142-412: The angle the wings meet at the root, which may be restricted to meet other design criteria. Polyhedral is seen on gliders and some other aircraft. The McDonnell Douglas F-4 Phantom II is one such example, unique among jet fighters for having dihedral wingtips. This was added after flight testing of the flat winged prototype showed the need to correct some unanticipated spiral mode instability – angling

2205-416: The bank angle. Figure 2 shows the airplane as it presents itself to the oncoming air. In Figure 2, the sideslip conditions produce greater angle of attack on the forward-yawed wing and smaller angle of attack on the rearward-yawed wing. This alteration of angle of attack by sideslip is visible in Figure 2. As greater angle of attack produces more lift (in the usual case, when the wing is not near stalling),

2268-457: The carriage of drop tanks . A two-seat trainer version designated Su-9U was also produced in limited numbers (about 50 aircraft). It received the NATO reporting name " Maiden ." It had a full armament and radar system with displays in both cockpits, allowing trainees to practice all aspects of the interception mission. Still, because the second seat further reduced the already meager fuel fraction, it

2331-424: The change in rolling moment coefficient (the " C l ") per degree (or radian) of change in sideslip angle (the " β {\displaystyle \beta } "). The purpose of dihedral effect is to contribute to stability in the roll axis. It is an important factor in the stability of the spiral mode which is sometimes called "roll stability". The dihedral effect does not contribute directly to

2394-432: The dihedral angle on the horizontal tail. During design of a fixed-wing aircraft (or any aircraft with horizontal surfaces), changing dihedral angle is usually a relatively simple way to adjust the overall dihedral effect. This is to compensate for other design elements' influence on the dihedral effect. These other elements (such as wing sweep, vertical mount point of the wing, etc.) may be more difficult to change than

2457-438: The dihedral angle. As a result, differing amounts of dihedral angle can be found on different types of fixed-wing aircraft. For example, the dihedral angle is usually greater on low-wing aircraft than on otherwise-similar high-wing aircraft. This is because "highness" of a wing (or "lowness" of vertical center of gravity compared to the wing) naturally creates more dihedral effect itself. This makes it so less dihedral angle

2520-872: The fall of the Soviet Union, the Su-15 was abruptly retired from the new Russian Air Force in 1993 to comply with the Treaty on Conventional Armed Forces in Europe . Most were hastily scrapped in favour of more advanced interceptors, including the Su-27 and MiG-31 , but some are in reserve storage for emergency use. In Ukraine, the last Su-15s (at Kramatorsk and Belbek ) were withdrawn from use in 1996. Proposed advanced version with Tumansky R-67-300 three spool turbofan engines, each producing 78.44 KN of afterburning thrust. Sukhoi Su-19 would have ogival wing, improved avionics suite with new Look down - shoot down radar and additional pylons for missiles. Not built. Some Western reports indicate that

2583-553: The following year, and it entered service with the PVO in 1967 , replacing Su-9s, Su-11s, and Yakovlev Yak-25s . The initial Su-15 received the NATO reporting name "Flagon-A". A simplified trainer version, the Su-15UT (NATO "Flagon-C"), with no radar or combat capability, entered service in 1970 . Initial delta-winged Su-15s had poor take-off and landing characteristics, and so Sukhoi investigated

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2646-403: The forward wing will have more lift and the rearward wing will have less lift. This difference in lift between the wings is a rolling moment, and it is caused by the sideslip. It is a contribution to the total dihedral effect of the aircraft. The rolling moment created by the sideslip (labeled as "P") tends to roll the aircraft back to wings level. More dihedral effect tries to roll the wings in

2709-410: The height and size of anything on an aircraft that changes its sidewards force as sideslip changes. Dihedral angle on an aircraft almost always implies the angle between two paired surfaces, one on each side of the aircraft . Even then, it is almost always between the left and right wings . However, mathematically dihedral means the angle between any two planes. So, in aeronautics, in one case,

2772-458: The intruder, along with any gun pods the Su-15 might be carrying. The Su-15 was optimised for the high-altitude interception role with its fast climb-rate and high speed at high altitude but lacked look-down/shoot-down capability, even with the Su-15TM's more sophisticated Taifun radar. This eventually led to the MiG-23 P, which did have look-down/shoot-down capability, becoming the preferred asset of

2835-437: The nose back into the wind, much like a weathervane, minimizing the amount of sideslip that can be present. If there is no sideslip, there can be no restoring rolling moment. If there is less sideslip, there is less restoring rolling moment. Yaw stability created by the vertical fin opposes the tendency for dihedral effect to roll the wings back level by limiting sideslip. The spiral mode is the tendency to slowly diverge from, or

2898-620: The nose clear for a large radome for the RP-22 Oryol-D ("Eagle") radar (NATO "Skip Spin"), and the T-5, essentially a heavily modified Su-11 with a widened rear fuselage containing two Tumansky R-11 engines. These led to the T-58, which combined the twin engines with a modified version of the T-49's nose, but with side inlets further back, behind the cockpit. It was approved for production on 5 February 1962, as

2961-509: The pilot elected to break away from the U-2 and continue with the original flight plan. Its pilot, Captain Igor Mentyukov, later claimed that his slipstream caused the U-2 to break apart. He discounts the official version that the U-2 was shot down by an SA-2 missile, explaining that Powers could not have survived such a hit. On September 4, 1959 a modified Su-9 (designated T-431 by the bureau) piloted by Vladimir Sergeievitch Ilyushin set

3024-478: The positive, up angle between the left and right wings, while usage with the prefix "an-" (as in " an hedral") evolved to mean the negative, down angle between the wings. The aerodynamic stabilizing qualities of a dihedral angle were described in an influential 1810 article by Sir George Cayley . In analysis of aircraft stability, the dihedral effect is also a stability derivative called C l β {\displaystyle \beta } meaning

3087-554: The previous Su-9 and Su-11, including Sukhoi's characteristic rear-fuselage air brake , the Su-15 abandoned the shock- inlet cone nose intake for side-mounted intake ramps with splitter plates feeding two powerful turbojet engines, initially the Tumansky R-11F2S-300. The change allowed room in the nose for a powerful search radar, initially the RP-22 Oryol-D (NATO 'Skip Spin'). The early Su-15 ("Flagon-A") had pure delta wings like its predecessors, but these were replaced from

3150-643: The restoring of "wings level", but it indirectly helps restore "wings level" through its effect on the spiral mode of motion described below. Aircraft designers may increase dihedral angle to provide greater clearance between the wing tips and the runway. This is of particular concern with swept-wing aircraft, whose wingtips could hit the runway on rotation/touchdown. In military aircraft dihedral angle space may be used for mounting materiel and drop-tanks on wing hard points, especially in aircraft with low wings. The increased dihedral effect caused by this design choice may need to be compensated for, perhaps by decreasing

3213-443: The rolling moment is caused by one wing moving more quickly through the air and one wing less quickly. Indeed, these are actual effects, but they are not the dihedral effect, which is caused by being at a sideslip angle, not by getting to one. These other effects are called "rolling moment due to yaw rate" and "rolling moment due to sideslip rate" respectively. Dihedral effect is not roll stability in and of itself. Roll stability

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3276-422: The root chords of the two surfaces. This is the more meaningful usage because the directions of zero-lift are pertinent to trim and stability while the directions of the root chords are not. This measurement is also often referred to as decalage . In geometry, dihedral angle is the angle between two planes. Aviation usage differs slightly from usage in geometry. In aviation, the usage " di hedral" evolved to mean

3339-422: The stability of the spiral mode. This increases maneuverability which is desirable in fighter-type aircraft. Anhedral angles are also seen on aircraft with a high mounted wing, such as the very large Antonov An-124 and Lockheed C-5 Galaxy cargo aircraft. In such designs, the high mounted wing is above the aircraft's center of gravity which confers extra dihedral effect due to the pendulum effect (also called

3402-508: The tendency to slowly return to wings level. If the spiral mode is stable, the aircraft will slowly return to wings-level, if it is unstable, the aircraft will slowly diverge from wings-level. Dihedral effect and yaw stability are the two primary factors that affect the stability of the spiral mode, although there are other factors that affect it less strongly. Factors of design other than dihedral angle also contribute to dihedral effect. Each increases or decreases total aircraft dihedral effect to

3465-413: The term "dihedral" is applied to mean the difference in angles between two front-to-back surfaces: Longitudinal dihedral is the difference between the angle of incidence of the wing root chord and angle of incidence of the horizontal tail root chord. Longitudinal dihedral can also mean the angle between the zero-lift axis of the wing and the zero-lift axis of the horizontal tail instead of between

3528-762: The very low vertical CG more than compensates for the negative dihedral effect created by the strong anhedral of the necessarily strongly downward curving wing. The wing location on a fixed-wing aircraft will also influence its dihedral effect. A high-wing configuration provides about 5° of effective dihedral over a low-wing configuration. A side effect of too much dihedral effect, caused by excessive dihedral angle among other things, can be yaw-roll coupling (a tendency for an aircraft to Dutch roll ). This can be unpleasant to experience, or in extreme conditions it can lead to loss of control or can overstress an aircraft. Military fighter aircraft often have near zero or even anhedral angle reducing dihedral effect and hence reducing

3591-424: The wing and the zero-lift axis of the horizontal tail. Longitudinal dihedral can influence the nature of controllability about the pitch axis and the nature of an aircraft's phugoid -mode oscillation. When the term "dihedral" (of an aircraft) is used by itself it is usually intended to mean "dihedral angle ". However, context may otherwise indicate that "dihedral effect " is the intended meaning. Dihedral angle

3654-449: Was fitted with the Lazur-S datalink system, which transmitted instructions to the pilot to accomplish the interception. The later Su-15TM had a Vozdukh-1M datalink and SAU-58 ( sistema automaticheskogo upravleniya , automatic control system ) capable of carrying out completely automatic, 'hands-off' interceptions until the last moments of the interception. Primary armament of the Su-15 was

3717-526: Was followed in December 1971 by the Su-15TM (NATO "Flagon-E"), with the improved Taifun-M radar (NATO "Twin Scan") and provision for UPK-23-250 gun pod or R-60 (AA-8 "Aphid") short-range air-to-air missiles. Aerodynamic demands forced a redesign of the radome with an ogival shape, earning a new NATO reporting name, "Flagon-F", although again the Soviet designation did not change. A comparable combat-capable trainer,

3780-452: Was normally fired first in order to prevent the possibility of the IR missile locking on to the radar homing missile. Later 'Flagon-F' models often carried two R-98s and one or two pairs of short-range R-60 (AA-8 'Aphid') missiles. Late-model 'Flagons' also sometimes carried a pair of UPK-23-250 23 mm gun pods on the fuselage pylons, each containing a two-barrel GSh-23L cannon. The Su-15 formed

3843-563: Was not genuinely combat-capable. The Su-9 has been frequently mistaken for the MiG-21 due to the many similarities in design. The primary distinguishing features are the Su-9's size and its bubble canopy. Data from OKB Sukhoi : a history of the design bureau and its aircraft General characteristics Performance Armament Related development Aircraft of comparable role, configuration, and era Related lists Dihedral (aircraft)#Anhedral Dihedral angle

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3906-492: Was produced in large numbers (1,290 of all types), the Su-15, like other highly sensitive Soviet aircraft, was never exported to the Warsaw Pact or any other country due to its sophisticated systems. Some Su-15 were reported to be deployed in Egypt in 1972 but were used with Soviet crews. At one point, the Su-15 was considered for use as a strike fighter, but proved to be too specialised as an interceptor to be used in that role. After

3969-453: Was to fly under autopilot, using GCI commands sent through the datalink. The radar would only be turned on as the interceptor approached the target in order to provide targeting parameters for the radar homing K-8/R-8/R-98 missiles, the high power of the radar allowing it to 'burn through' enemy ECM signals. If all else failed, IR homing versions of the K-8 would provide a last opportunity to shoot down

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