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Cobra maneuver

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(Redirected from Pugachev's Cobra)

Cobra maneuver / Dynamic deceleration
The cobra maneuver performed by a Swedish Saab 35 Draken. The footage displays the maneuver in profile next to a non-maneuvering aircraft for reference, showing how the maneuver affects the speed of the aircraft and how it can be used to make a pursuing aircraft overshoot.

In aerobatics, the cobra maneuver (or just the cobra), also called dynamic deceleration,[1] among other names (see Etymology), is a dramatic and demanding maneuver in which an airplane flying at a moderate speed abruptly raises its nose momentarily to a vertical and slightly past vertical attitude, causing an extremely high angle of attack and momentarily stalling the plane, making a full-body air brake before dropping back to normal position, during which the aircraft does not change effective altitude.

The maneuver relies on the ability of the plane to be able to quickly change angle of attack (alpha) without overloading the airframe,[2] and sufficient engine thrust to maintain nearly constant altitude through the entire move,[3] but also post-stall stability and aerodynamics that allows for the recovery to level flight. The maneuver demands accurate pitch control, alpha stability and engine-versus-inlet compatibility for the aircraft, as well as a high skill level on the part of the pilot.

The cobra maneuver is an example of supermaneuverability,[4] specifically poststall maneuvering. The Herbst maneuver and the helicopter maneuver are similar post-stall maneuvers that are often executed by 4.5th generation and 5th generation fighter aircraft employing thrust vectoring.[5]

The maneuver is typically performed at air shows,[6] but could be used as a last-ditch maneuver to force a chaser to overshoot in close-range air combat.[2][7] The maneuver has never been verified in real combat, although it has been used during mock dogfights[2] and border protection.[8][9]

Etymology

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The maneuver has many names, but it is most commonly known as the cobra or the cobra maneuver in the respective language; for example: Russian: Ко́бра (Kobra), German: Kobramanöver. The etymology for the name cobra is unknown but it could refer to the plane displaying its top and bottom profile, much like a cobra spreading its shield, or rearing its body up vertically to attack.[citation needed] A notable variant of the "cobra" name is Pugachev's cobra (alternatively the Pugachev cobra), referencing the Soviet pilot Viktor Pugachev, who was the first to bring the maneuver to the public eye.

In Sweden, the country which presumably was the first to discover the maneuver, the maneuver is traditionally known under the name kort parad ("short parry"),[10] the Swedish term for the fencing maneuver "beat parry", in which an incoming attack is deflected using a beat (a sharp strike to the opponents blade, knocking it out of line), leaving the enemy open for a riposte.

As a more scientific name, the maneuver has been given the name dynamic deceleration, referring to the way the plane loses speed during the maneuver.[1] In a similar manner, the Syrians apparently called the maneuver the Zero speed maneuver (Arabic: مناورة السرعة صفر, "Munawarat alsureat sifr") during their usage of MiG-21F-13s and the like.

Maneuver description

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Profile diagram of the cobra maneuver showing angle of attack (α = alpha). The aircraft in the motif depicts a MiG-29.

The maneuver can simply be described as; a rapid vertical pitchup from level flight without initiating a climb, followed by a forward-pitch back to level flight. If properly performed, the plane maintains nearly straight flight throughout the maneuver. The plane does not roll or yaw in either direction. This greatly lowers the speed of the aircraft due to the un-aerodynamic under-surface of the aircraft going against the airflow.

To perform the cobra, the maneuver must be entered from fairly high subsonic speeds. Proper entry speed is necessary because, if the maneuver is entered too slowly, the plane might be unable to complete the maneuver or return to level flight with sufficient speed, while entering at too high a speed would create g-forces so high that the pilot loses consciousness or the airframe is damaged. High thrust is also needed throughout the maneuver to not stall out.

To execute the maneuver the aircraft only needs to use its standard aerodynamic controls, however executing it can be achieved more easily with the addition of modern thrust vectoring.

Aerodynamics

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The cobra maneuver requires more than just pilot input and aircraft maneuverability to be performed. Since the maneuver requires the aircraft to not lose or gain substantial altitude during the maneuver, the change of alpha during the vertical pitchup has to be fast enough to break the airflow of the wings, as to not make the aircraft climb. To be able to perform this rapid vertical pitchup the aircraft needs an "aerodynamic instability" in its core aerodynamics which will make the aircraft rapidly pitch up by itself once the elevator of the aircraft is pitched to the point where it breaks the airflow during a pitch up; but also post-stall control and stability to not enter an uncontrollable stall at the peak of the pitch; which then allows the aircraft to center the elevator and using the torque from the elevators added drag to pitch forward and make an aerodynamic recovery to horizontal flying again.[1]

Only specific aircraft feature this "instability" and thus the maneuver can only be performed by a small number of aircraft models. This is because conventional aircraft are designed to lack this instability for safety reasons, and can thus not execute the maneuver by conventional means.

Simply put, the cobra relies more on the core aerodynamics of the aircraft than its control surfaces and avionics and can thus only be performed by specific aircraft featuring aerodynamics allowing for the maneuver.

Execution (Sukhoi Su-27)

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Cobra maneuver schematic of the Su-27 (called supermaneuverability in some sources)

In the case of the Su-27, to execute the maneuver the pilot initially disengages the angle of attack limiter of the plane, normally set at 26°.[3] This action also disengages the g limiter. After that, the pilot pulls back hard on the stick. The aircraft reaches an angle of attack of 90–120° with a slight gain of altitude and a significant loss of speed. When the elevator is centered, the drag at the rear of the plane causes a torque that makes the aircraft pitch forward. At the same time, the pilot adds power to compensate for the reduced lift.[citation needed]

Use in combat

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If pursued by an enemy fighter in a dogfight, by executing the cobra, a sufficiently closely pursued aircraft may suddenly slow itself down to the point that the pursuer overshoots it, allowing the previously pursued aircraft to complete the cobra behind the other. This may allow the now-pursuing aircraft an opportunity for firing its weapons, particularly if a proper pointing aspect (facing toward the former pursuer) can be maintained. Due to the speed loss when performing a cobra, maintaining weapons on target may require the use of thrust vectoring or canard control surfaces. Otherwise, the maneuver may also allow the pursued plane to flee as the overshooting attacker may lose track of the target.

The maneuver is also potentially a defense against radar, as the sudden change in velocity can often cause Doppler radar to lose its target lock.[11] Doppler radars often ignore any objects with a near-zero velocity to reduce ground clutter. The cobra maneuver's sudden change to near-zero velocity often results in the target being momentarily filtered off as ground clutter, making it difficult for the radar to lock onto the target, or breaking the target lock if already established. There is no available documentation of this being tested beyond theory.

While the cobra maneuver may appear to be useful to force a pursuer to overshoot, the tactic would almost never be employed in any active threat scenario for a variety of reasons. The most obvious of these is the extreme loss of speed. Assuming the defending aircraft successfully forces the aggressor to overshoot the attack, the defender often does not have enough energy to counter-attack. The second more prevalent reason for avoiding the use of the maneuver is taught in most fighter pilot training. When attacking an aircraft, the pilot must be mindful of the closure-rate between both aircraft. If the closure rate is too high, the defender can change direction rapidly, which denies the attacker a shot opportunity, and thereby decreases the probability of kill. If the attacker manages their speed and rate of closure properly, the defender executing a cobra maneuver presents the attacker with a larger target to shoot due to the increased presented surface area when the defender is oriented vertically.

The cobra maneuver has been used in mock dogfights but there is little to no known documentation of it being used in actual combat. One primary described mock dogfight was fought between two planes in Swedish service. In this case, a Saab 35 Draken was pursued by a Saab 37 Viggen. The Draken suddenly performed a cobra maneuver and the Viggen overshot it. Existing material of this mock dogfight does not cover the elements of the engagement before and after the maneuver in detail, which would be useful in assessing its usefulness in modern combat. The pilots say that the maneuver was a useful combat move if performed correctly, with the caveat that it was only effective as a last ditch maneuver due to the loss of speed when performed.[2]

History

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Sweden

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Swedish Saab 35 Draken (J 35A, a/f 35076) during camouflage tests in the early 1960s

During the early 1960s, the maneuver was developed and performed by Swedish pilots flying the Saab 35 fighter jet.[12] It was invented during training for recovery from super stalls (also known as deep stalls) to which the double delta tailless design of the Saab 35 is susceptible.[13] A super stall is an uncontrollable stall which is much harder to recover from than a standard stall. Super stall plagued the early years of Saab 35 service, causing several deaths, which led the Swedish air staff to implement extra training on how to counteract and recover from them.[12] The result was the cobra maneuver. The Swedes named the maneuver "kort parad" (short parry) after a fencing maneuver of the same name, known as "beat parry" in English. When pulling high alpha, the pilot would have noticed that he was entering super stall, and would then have pulled negative alpha to recover. The dramatic effect of this maneuver on aircraft speed was noticed and pilots started to purposely use it to drop speed.[12] The Swedish test pilots who discovered the cobra were Bengt Olow [sv] and Ceylon Utterborn [sv], who developed the technique around 1961–1963.[14]

Saab 35 Draken

The Swedish pilots soon considered how to use this move in combat to get a pursuing aircraft to overshoot, putting it in a perfect position for a riposte, and it was not long until it was proven viable during mock dogfights.[12][2] In real combat, depending on the situation and the execution of the maneuver, it could be used to confuse the enemy by making it lose the target or to overshoot, which would allow the pursued pilot the opportunity to either flee from combat or re-engage. However, the maneuver was very difficult and dangerous to use as anything more than a last-ditch effort, as without precise execution the aircraft's slow speed after the maneuver would make it an easy target.[15]

The maneuver originated with the Bråvalla Wing, the first one to receive the Saab 35 fighter plane. As the fighter was adopted by other wings over time, so was the maneuver. The Scania Wing apparently called the maneuver "Wacka", which has no real meaning in Swedish.[2]

Sweden effectively shared borders with the Soviet Union over the Baltic Sea, so both sides regularly flew into the international space between the two. In the event, the Saab 35s regularly intercepted and escorted Soviet planes away from Swedish airspace. Sometimes these encounters would result in non-combat dogfights, which were either playful or threatening in nature.[12] Apparently, the cobra maneuver was used during some of these engagements, surprising the Soviets.[8] Late in the Saab 35's service life, the maneuver was used as a 'secret weapon' by Saab-35 pilots in mock dogfights facing the more advanced Saab 37 fighter. The Saab 37 was unable to safely enter super stalls, and therefore its pilots did not receive any major training against its use. The cobra maneuver was therefore unknown to many Saab 37 pilots prior to facing it in competition.[2] Due to the appeal of the tactic, some Saab 37 pilots attempted it, but to their dismay were unable to effectively perform it above speeds of 350 km/h (220 mph) as the Saab 37 couldn't safely handle the necessary gs, rendering it effectively useless in combat.[2]

When the Saab 35 was retired, so was the maneuver, as the next generations of Swedish warplanes, the Saab 37 and the Saab 39, couldn't effectively perform it. Due to the secrecy of the Cold War era and other factors, the Swedish cobra was largely unknown to the world until some former Saab 35 and 37 pilots wrote about it years later in books[2][12] and articles,[8][15] long after the Soviets had been credited with its discovery.

Finland and Austria

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As Sweden exported the Saab 35 Draken, so was the cobra maneuver. Fighter variants of the Saab 35 were exported to both the Finnish Air Force and the Austrian Air Force.

In an interview, former Finnish Air Force pilot Ari Saarinen recalled performing the maneuver in a Draken while intercepting a Royal Air Force Hawker Siddeley Nimrod over the Baltic Sea; the Nimrod pilot reduced power in order to get the Finns to overshoot, but the Finnish Drakens performed the maneuver to slow down, which according to Saarinen drew praise over the radio from the British Nimrod crew.[9]

According to a video uploaded by the Scania Wing comrade association (Swedish: F10 Kamratförening), the Swedish cobra was taught to Austrian pilots training on the Saab 35 in Sweden.[16] It is unknown whether the Austrians used this as a combat maneuver or just as training against super stall.

Syria

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Beyond Sweden, Syria also discovered the maneuver prior to the Soviets.

In 1961 when Syria left the United Arab Republic, they were left with a very weak air force. The Syrians had to order new combat aircraft, and procured the Mig-21F-13 in June 1962.[17] Once the aircraft had arrived and been integrated into the fleet, a problem became apparent. All of the unit commanders had been selected based on their political associations and loyalty to superiors, instead of knowledge of air combat. The new commanders were over-reliant on advice from about 30 Soviet advisors assigned to the Syrian Air Force to help with training on the Migs, but were generally ineffective. In this era of power over knowledge, however, a handful of pilots with powerful connections were able to disregard their Soviet advisors and orders from their commanders.[17]

One of these pilots, Mohammad Mansour, then a novice MiG-21-pilot fresh from a conversion course in the USSR, had an older brother, Fayez Mansour, with deep connections high in the chain of command in Damascus. Those connections enabled him to challenge Soviet advisors and demand greater operational flexibility for himself and other pilots of his unit.[17]

During Mohammed's first clashes with the Israeli Air Force, he realized that there was a need for an effective defensive maneuver in close combat that forced a pursuer to overshoot. His initial solution based on Soviet manuals consisted of rapid descending turns followed by a sudden activation of the afterburner and a climb. However, during a test flight in early 1967, Mohammad inadvertently pitched the nose of his MiG-21 too hard, so that the forward movement of his aircraft nearly stopped. In reaction, he engaged the afterburner of his MiG, and ended with the plane standing vertically on the verge of stalling out of control. Mohammad managed to recover the plane from that state, just in time to prevent a crash. Intrigued, he decided to try to replicate the maneuver in a controlled manner, this time by engaging the afterburner beforehand, as the Tumansky R-11 engine of the MiG-21 had to spool for full effect. After successful replication of the maneuver, it became clear that this was the close combat defensive maneuver that he sought.[17]

The Syrians named the cobra the "zero-speed maneuver" (Arabic: مناورة السرعة صفر "munawarat alsureat sifr"). Mohammad soon saw combat again with the Israeli Air Force but never got to use the maneuver.[17] The cobra quickly became a standard part of defensive tactics for Syrian Mig-21s.

Pakistan and Egypt

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Egyptian MiG-21

With time, as their air forces were stationed in Syria, the maneuver spread to both the Pakistan and Egyptian air force, who also began using it as a standard defensive maneuver for their MiG-21s.[17]

The cobra maneuver may have been performed in combat by an Egyptian pilot during the Yom Kippur War, but the theory is based on a quote from an Israeli pilot that only mentions an Egyptian MiG-21 apparently standing on its tail while trying to evade an attack.[17]

Soviet Union

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Research and developments on supermaneuverability started in USSR in the early 1980s by Central Aerohydrodynamic Institute, Gromov Flight Research Institute, Sukhoi and Mikoyan.[18]

Soviet Sukhoi Su-27

In flight testing the Su-27 test pilot Igor Volk was the first to perform the maneuver in that aircraft in practice. Viktor Pugachev was the first to publicly demonstrate the maneuver in the Su-27 aerobatics display at the Le Bourget airshow of 1989.[18][3] The tactic was previously unknown to the public and it was quickly named after Pugachev.[19]

Derivatives of the cobra

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There are several derivatives of the cobra which all initiate similarly, but end differently.

Cobra climb

In the cobra climb, the aircraft initiates the cobra, but instead of remaining in altitude and continuing forward, it starts to stall climb (climbing vertically). The maneuver is similar to a regular stall climb except that the change from level flight to stall climb happens much faster. However, unlike a regular climb, this still achieves the effect of the cobra and the aircraft will still stall momentarily which lowers speed and momentum. The maneuver ends with the climb and the aircraft can return to common flight in various ways.

Cobra stall

In the cobra stall, the aircraft initiates the cobra, but instead of returning to level flight, the aircraft instead fully stalls out after which it applies thrust and rudder to change the direction of the aircraft.

Cobra barrel roll

In the cobra roll, the aircraft initiates the cobra but instead of returning to level flight, the aircraft uses its ailerons and rudder to initiate a barrel roll at the peak of the initial nose climb which ends the maneuver with a barrel roll.

Cobra hover

The cobra hover is an extension of the original maneuver in which an aircraft initiates the cobra but remains in the "cobra state" for a longer period of time by the use of thrust control, thus achieving the "hover" part of the maneuver. After which the aircraft can complete the maneuver in various ways depending on its energy.

Cobra turn

The cobra turn is an air combat maneuver.[20] It is a variation on the cobra maneuver where the aircraft performs the pull-up, but instead of returning to level flight applies rudder or thrust vectoring and turns downward. The aircraft achieves a negative angle of attack, ending the maneuver in a dive, therefore regaining airspeed sooner than the common cobra. John Turner of BAE considers[citation needed] the cobra maneuver to have little use in air combat maneuvering. It could also be argued that the combat effect is likely to be similar to the “Vectoring In Forward Flight" or VIFFing maneuver. In theory, VIFFing allows the aircraft to effectively slow down or stop while the enemy overshoots, leaving the aircraft in a favorable position to attack the enemy.[21]

Unlike VIFFing, however, the fully developed cobra maneuver leaves the aircraft in a precarious and non-offensive attitude, with no energy, with weapons pointing toward empty sky and with the pilot having lost sight of the enemy. If the pilot exits the cobra by using rudder, this is a very slow version of the hammerhead. At the same time, the aircraft is defenseless, unable to maneuver, nearly stationary, offers the largest lateral visual and radar target and is creating a massive plume of hot exhaust, making it an easy target for any type of weapon and attack which an enemy might choose.

The transition from cobra maneuver to effective and controlled flight takes several seconds, and airspeed sufficient for defensive maneuvering is not recovered for more than ten seconds. While entering the cobra is effective as a "speed brake" maneuver, usefulness in combat is limited at best, and then only if exited while sufficient energy remains to bring the weapons to bear before the opponent can break into an evasive maneuver—or, worse, loop back and attack. One simple defense-into-attack maneuver is for the opponent to split-S, pass under the cobra aircraft, then half-loop again to bring the cobra aircraft into the cone of fire. The primary danger for the opponent becomes the possibility of a mid-air collision with the slowly moving target.

The cobra turn first gained widespread attention after it was performed by the Sukhoi Su-27, Su-35 and Su-37 at various European airshows.

List of cobra capable aircraft

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Cobra capable aircraft (alphabetical order)
Name/Designation Type Year of introduction Country of origin Sources
Chengdu J-10B TVC Demonstrator 2018  China [22]
General Dynamics F-16 VISTA Demonstrator 1992  US [23]
Mikoyan-Gurevich MiG-21F-13 Fighter 1960  Soviet Union [17]
Mikoyan MiG-29A Fighter 1983  Soviet Union [24][25]
Mikoyan MiG-29M OVT Demonstrator 2001  Russia [26]
Saab 35A Fighter 1960  Sweden [14]
Saab 35B Fighter 1962  Sweden [14]
Saab 35C Trainer 1962  Sweden [16]
Saab 35D, 35Ö Fighter 1963  Sweden [14][16]
Saab 35F, 35J, 35S Fighter 1965  Sweden [2][9]
Sukhoi Su-27 Fighter 1985  Soviet Union [1][3]
Sukhoi Su-35 Fighter 2014  Russia [27]

See also

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References

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  1. ^ a b c d "Air Show - Paris 1989". youtube.com. 1989. Archived from the original on 13 December 2021. Retrieved 14 March 2021.
  2. ^ a b c d e f g h i j Edlund, Ulf; Kampf, Hans, eds. (2009). System 37 Viggen. Flyghistorisk revy, 0345-3413 ; [Specialnr 2009] (in Swedish). Stockholm: Svensk flyghistorisk förening (SFF). pp. 212, 213. SELIBR 11717818.
  3. ^ a b c d e Mike Spick (2002). The Illustrated Directory of Fighters. St. Paul, Minnesota: MBI Publishing Company. p. 442. ISBN 0-7603-1343-1. Retrieved 29 October 2011.[permanent dead link‍]
  4. ^ Abzug, Malcolm J.; E. Eugene Larrabee (2005). Airplane Stability and Control: A History of the Technologies that Made Aviation Possible. Cambridge University Press. pp. 157–161. ISBN 978-0-521-80992-4.
  5. ^ Benjamin Gal-Or. "Vectored Propulsion, Supermaneuverability, and Robot Aircraft". Springer Verlag, 1990, ISBN 0-387-97161-0, ISBN 3-540-97161-0.
  6. ^ "Example of the cobra being performed at an air show". YouTube. 7 February 2018. Archived from the original on 13 December 2021.
  7. ^ Crane, David. "Air-to-Air Fighter Combat Application of Pugachev's Cobra Maneuver: Busting the Western Myth". Defense Review. Retrieved 14 January 2012.
  8. ^ a b c "F10 Kamratförening J 35 Draken". www.f10kamratforening.se (in Swedish). 20 October 2019.
  9. ^ a b c "Interview with Ari Saarinen on the Saab 35 Draken, Youtube". YouTube. 5 August 2018. Archived from the original on 13 December 2021.
  10. ^ Flyghistorisk revy, System 37 Viggen. Svensk Flyghistorisk förening. 2009. p. 212.
  11. ^ Bill Sweetman, Aviation Week & Space Technology, 24 Jun 2013, quoting Sukhoi chief test pilot Sergey Bogdan
  12. ^ a b c d e f Edlund, Ulf; Lundborg, PeGe; Kampf, Hans, eds. (2005). Draken 50 år: en antologi [Draken 50 years: an anthology]. Flyghistorisk revy, 0345-3413 ; [Specialnr 2005] (in Swedish). Stockholm: Svensk flyghistorisk förening (SFF). SELIBR 10082650.
  13. ^ Speciell förarinstruktion för J 35B Draken. Sweden: Swedish air force. pp. 73, 74.
  14. ^ a b c d Bratt, Erik (1986). Silvervingar: en bok om flyg och flygplan [Silverwings: a book on aviation and aircraft] (in Swedish). Linköping: Flygföretag. p. 267. SELIBR 577714.
  15. ^ a b "Article on how it was to fly the Saab 35". 2011.
  16. ^ a b c "F10 kamratförening: filmer, clip Tisoe". Archived from the original on 22 October 2016.
  17. ^ a b c d e f g h Cooper, Tom (7 August 2019). "The Unknown Story of the Syrian MiG-21 Pilot who Developed the Cobra Manoeuvre".[dubious – discuss]
  18. ^ a b Bjušgens, Georgij S. (1993). CAGI - centr aviacionnoj nauki (in Russian). Nauka. ISBN 978-5-02-007017-2.
  19. ^ Hall, Rex; Shayler, Davide; Vis, Bert (2005). Russia's Cosmonauts: Inside the Yuri Gagarin Training Center. Chichester, UK: Praxis Publishing. pp. 335–336. ISBN 0-387-21894-7.
  20. ^ Gordon, Yefim (1999). Sukhoi Su-27 Flanker: Air Superiority Fighter. Airlife Publishing. ISBN 1840370297.
  21. ^ "That Magnificent Flying Machine". Time. 7 June 1982. Archived from the original on 30 September 2007. Retrieved 30 April 2010.
  22. ^ "2018 Chinese J-10B 殲10矢量 TVC performing vertical take-off & Cobra MANOEUVRE & roll". YouTube. 5 November 2018.
  23. ^ "General Dynamics NF-16 VISTA". YouTube. 24 January 2009.
  24. ^ John Dovishaw (9 September 2015), Russia Mig does Cobra Maneuver at Dayton Airshow, archived from the original on 13 December 2021, retrieved 8 February 2019
  25. ^ Venci Dimitrov (12 October 2014), Миг-29 управляван от Ген. Радев /Авиошоу 2014, летище София/, archived from the original on 13 December 2021, retrieved 8 February 2019
  26. ^ "Cobra Maneuver ?". International Journal of Turbo & Jet-engines. 11. 1994. Retrieved 23 March 2011.
  27. ^ Mitko Ian (18 June 2013). "Sukhoi SU-35 fighter has all the right moves at Paris Air Show". Gizmag.com. Retrieved 18 June 2013.
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Video clips

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