Cobra maneuver

In aerobatics, the Cobra maneuver, also known as just the Cobra, is a dramatic and demanding maneuver in which an airplane flying at a moderate speed suddenly raises the nose momentarily to the vertical position and slightly beyond, momentarily stalling the plane and making it a full-body air brake, before dropping it back to normal, during which the aircraft does not change effective altitude.

Pugachev's Cobra maneuver is one of the tests for supermaneuverability, here performed by a Su-27.

The maneuver relies on the ability of the plane to be able to quickly change angle of attack (alpha), which momentarily stalls the plane without overloading the airframe,[1] and sufficient engine thrust to maintain approximately constant altitude through the entire move.[2] The maneuver demands accurate pitch control, alpha stability and engine-versus-inlet compatibility on the part of the aircraft, as well as a high skill level on the part of the pilot.

Although the maneuver is mainly performed at air shows,[3] it could be used as a last-ditch maneuver to make a pursuing plane overshoot in close-range air combat.[1][4] The maneuver is not known to have been used in real combat, although there are records of it being used during mock dogfights[1] and during border protection.[5]

Description of the Cobra

The Cobra must be performed at fairly high speed (sub-sonic combat speed) so that the aircraft ends the maneuver at a sufficient speed for level flight. By definition, the aircraft cannot lose or gain substantial altitude during the maneuver, which means that the change of alpha has to be fast and natural; high thrust is also needed to avoid a stall.

The maneuver can only be achieved in supermaneuverable aircraft, as "conventional" aircraft lack the "instability" needed to execute the necessary rapid attitude changes. The Cobra relies more on the core aerodynamics of the aircraft than its control surfaces and avionics.

Some conventional aircraft can perform similar maneuvers, but with differences, such as being performed at low speed, changing alpha too slowly, or using low thrust so as not to gain altitude, i.e. performing a forced stall climb with no thrust, usually ending with the aircraft performing a climb or stalling instead of completing the cobra movement.[6][7]

Description

In the case of the Su-27, the pilot initially disengages the angle of attack limiter of the plane, normally set at 26°.[2] 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.

In a properly performed Cobra, the plane maintains nearly straight flight throughout the maneuver. The plane does not roll or yaw in either direction. Proper entry speed is necessary because, if the maneuver is entered too slowly, the pilot might not be able to complete the maneuver, while entering at too high a speed would create g-forces so high that the pilot loses consciousness or the airframe is damaged.

While the Cobra can be executed using only standard aerodynamic controls, it can be achieved more easily with modern thrust vectoring. In either case it is an example of supermaneuverability,[8] specifically poststall maneuvering. The Herbst maneuver and the helicopter maneuver are examples of similar post-stall maneuvers that are often carried out by 4.5th Generation and 5th Generation fighter aircraft, often employing thrust vectoring.[9]

Derivatives of the Cobra

Because of the nature of the Cobra, it does not always end in the normal way. This has led to several derivatives of the Cobra which all initiate it but end differently.

(Names are not official as these are not standard maneuvers by any means)

Cobra Climb

A Cobra Climb is when an aircraft initiates the Cobra, but instead of remaining in altitude and continuing forward, it starts to stall climb (climbing vertically). The maneuver acts like 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.[10]

Cobra Stall

The Cobra Stall 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.[11]

Cobra Turn

The Cobra Turn initiates the Cobra but instead of returning to level flight, the aircraft achieves a negative angle of attack, ending the maneuver in a dive, therefore regaining airspeed sooner than the common Cobra.

Cobra Barrel roll

The Cobra Roll 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.[12]

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.[13]

Names

The maneuver goes by many names around the globe but it is most often referred to as the Cobra maneuver in the respective language.[14] The origin 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.

Other notable names include: Pugachev's Cobra (alternative the Pugachev Cobra), which is named after Viktor Pugachev, the first pilot to bring the maneuver to the public eye. Short parade (Swedish: Kort parad), the original Swedish name for the maneuver, probably referring to the way the plane stands up during the maneuver. Zero speed maneuver (Arabic: مناورة السرعة صفر‎), the Syrian name for the maneuver, referring to the way the plane loses speed during the maneuver.

History

The maneuver first came to the public's attention when the Soviet test pilot, Viktor Pugachev, performed it at the Le Bourget Paris air show in 1989 using a Sukhoi Su-27.[2] As this maneuver was largely unknown to the public previous to this the maneuver was quickly named after Pugachev. But apparently Pugachev was not the first Soviet pilot who had performed the Cobra. Another Soviet test pilot, by the name of Igor Volk, did the Cobra previous to this when he tested aircraft behavior at high super-critical angles of attack, up to around 90°.[15]

Sweden
The Saab 35 Draken, in which the maneuver was first executed.

Several decades prior to Pugachev showing off his cobra, during the early 1960s, the maneuver was performed by Swedish pilots flying the Saab 35 fighter jet.[16] It was invented during training on how to recover from what is called a "super stall" in Swedish, which, simplified, can be described as an uncontrollable stall which appears on planes with specific features when reaching high angles of attack, or alpha.[17] Super stall plagued the early years of the Saab 35's service life, leading to several deaths, which in turn lead the Swedish air staff to implement extra training on how to counteract and recover from it.[16] It is currently not known exactly when and how the Swedish invented or discovered the Cobra but it was during this intense training period the Swedish pilots learned how to do it, but the maneuver was fairly simple. When pulling high alpha, the pilot would have noticed that he was going into super stall, and he would then have pulled negative alpha to get out of it. The effects this maneuver had on the aircraft's speed were noted and pilots started to purposely use it as a way to lower speed.[16]

The Swedes named the maneuver "kort parad", or "short parade" in English, likely referring to the way the plane stands up during the maneuver as if on parade. The Swedish pilots quickly started to theorize on how to use this move in combat as a way to get a pursuing aircraft to overshoot, and it was not long until it was proven viable during mock dogfights.[16][1] 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 to set up a new engagement. However, the maneuver was too difficult and dangerous to use as anything more than a last-ditch maneuver, as without precise execution the aircraft's low speed after the maneuver would make it an easy target.[18]

The maneuver originated with the Bråvalla Air Force Wing, who were the first wing to receive the Saab 35 fighter plane. As the plane was in time adopted by other wings, so was the maneuver. The Scania Air Force Wing apparently called the maneuver "Wacka", which has no real meaning in Swedish.[1]

As Sweden effectively shared borders with the Soviet Union over the Baltic Sea, both sides regularly flew into the international space between the two. Due to this, the Saab 35s had to regularly intercept and escort Soviet planes away from Swedish airspace. Sometimes these meetings would result in non-combat dogfights, which were either of playful or threatening nature.[16] Apparently, the Cobra maneuver was used during some of these engagements, much to the surprise of the Soviets.[5] Later in the Saab 35's service life, the maneuver was used as a secret weapon by Saab-35 pilots in mock dogfights when facing the more advanced Saab 37 fighter plane. The Saab 37 was unable to safely enter super stalls, and therefore its pilots did not receive any major training against it. Due to this, the Cobra maneuver was unknown to many Saab 37 pilots prior to facing it in combat.[1] Due to the interesting nature of the tactic, some Saab 37 pilots tried to do it with the Saab 37, but to their dismay it was unable to effectively do it above speeds of 350 km/h as the Saab 37 couldn't safely take the necessary gs to do it above that, effectively rendering it useless in combat.[1]

When the Saab 35 went out of service, the maneuver did as well, as the next generations of Swedish warplanes, the Saab 37 and the Saab 39, couldn't effectively perform the maneuver. 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 brought it up years later in books[1][16] and articles,[5][18] although this was long after the Soviets had been credited with its discovery.

Austria

According to a video uploaded by the Scania Air Force Wing comrade association (Swedish: F10 Kamratförening), the Swedish Cobra was taught to Austrian pilots training on the Saab 35 in Sweden.[19] It is unknown if the Austrians used this as a combat maneuver or just as training against super stall.

Finland

In an interview, former Finnish Air Force pilot Ari Saarinen recalled performing the maneuver in a Draken while intercepting a Royal Air Force 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 caused the British pilot to praise them over the radio.[20]

Syria

Beyond Sweden, Syria also discovered the maneuver prior to the Soviets. In 1961 when Syria broke loose from the United Arab Republic, they were left with a very weak air force. Due to this, the Syrians had to order new combat aircraft, which resulted in the Mig-21F-13 in June 1962.[21] Once the aircraft had arrived and been set up a problem became apparent. All the unit commanders had been selected based on political associations and loyalty to superiors, instead of knowledge in air combat. Due to this, the newly established commanders were over-reliant on advice from about 30 Soviet advisers assigned to the Syrian air force to help them work with the new planes. Due to this era of power over knowledge, a handful of pilots with powerful connections were able to disregard Soviet advisors and orders from their commanders.[21]

One of these pilots, Mohammad Mansour, then a novice MiG-21-pilot fresh from conversion course in the USSR, had an older brother, Fayez Mansour, with deep connections high up in the chain of command in Damascus. Thus, Mohammad began challenging advice from Soviet advisors and demanding greater operational flexibility for himself and other pilots of his unit.[21]

During Mohammed's first clashes with the Israeli Air Force, he learned that there was a need for an effective defensive maneuver for close combat that made a pursuing plane overshoot. His initial solution was based on Soviet manuals and 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. As a reaction, he engaged the afterburner of his MiG which ended with the plane standing vertical on the verge of stalling out of control. Mohammad managed to recover the plane from the state, just in time to prevent a crash. To prevent this from happening again, 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 defensive maneuver for close combat that he had been looking for.[21]

The Syrians came to name 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.[21] The Cobra quickly became a standard part of defensive tactics for Syrian Mig-21s.

Pakistan and Egypt
Egyptian Mig-21

With time, as different air forces were stationed in Syria, the maneuver spread to both the Pakistan and Egyptian air force, who also started using it as a standard defensive maneuver for their MiG-21s, as well on their F-7s.[21]

There is some indication that the Cobra maneuver was performed in combat by an Egyptian pilot during the Yom Kippur War, but it is based on the quote of an Israeli pilot that doesn't mention anything more than an Egyptian MiG-21 standing on its tail when trying to evade an attack.[21]

Soviet Union

When the cobra came to the Soviet Union's attention is unknown. It is possible that they first learned about it from the engagements with the Swedish over the Baltic Sea during the 1960s, but one story says that the Soviets, during their visits to Egypt between 1970 and 1972, saw the maneuver being performed by Egyptian MiG-21 pilots, and brought it back to the USSR.[21]

However, as there is currently no known material on the Soviets performing the maneuver prior to the 1980s, it is possible the maneuver was "rediscovered" by pilots like Viktor Pugachev or Igor Volk when testing advanced Soviet planes like the MiG-29 and Su-27.

The sketch of the MiG-29 performing the super maneuver, the Pugachev's Cobra.

Use in combat
The Sukhoi Su-27 is capable of the maneuver.

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 and/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 disadvantage of performing this maneuver is that it leaves the airplane in a low speed state, which can leave it vulnerable to attack from opposing aircraft. It can also be countered by maneuvers such as high yo-yo.

The maneuver is also potentially a defense against radar, as the sudden change in velocity can often cause Doppler radars to lose their lock on the target.[22] 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. However, there is no available documentation of this being tested beyond theory.

The Cobra maneuver has been used in mock dogfights but there is little to no known documentation of it being used in actual combat. The mock dogfights were performed by planes using 1950s technology which differs greatly from modern aircraft. Existing material of these mock dogfights does not cover the elements of the engagements before and after the maneuver, which would be useful in assessing its usefulness in modern combat. That being said, there is evidence that it was a useful combat move during the third and fourth generations of jet fighters.[1]

Examples of aircraft capable of the maneuver

Production aircraft

Experimental aircraft
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See also

References
  1. Ulf Edlund & Hans Kampf (2009). System 37 Viggen, FLYGHISTORISK REVY. Sweden: Svensk flyghistorisk förening. pp. 212, 213.
  2. 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.
  3. "Example of the cobra being performed at an air show".
  4. Crane, David. "Air-to-Air Fighter Combat Application of Pugachev's Cobra Maneuver: Busting the Western Myth". Defense Review. Retrieved 14 January 2012.
  5. "F10 Kamratförening J 35 Draken". www.f10kamratforening.se. 20 October 2019.
  6. "Video of F-22 performing a "fake" Cobra (2:06)". Youtube.
  7. "Video of F-22 performing "fake" Cobra's". Youtube.
  8. Malcolm J. Abzug; E. Eugene Larrabee (2005). Airplane Stability and Control: A History of the Technologies that Made Aviation Possible. pp. 157–161. ISBN 978-0-521-80992-4.
  9. Benjamin Gal-Or. "Vectored Propulsion, Supermaneuverability, and Robot Aircraft". Springer Verlag, 1990, ISBN 0-387-97161-0, ISBN 3-540-97161-0.
  10. "Video of a Saab 35 Draken performing a "Cobra Climb". (3:38)". Youtube.
  11. "Rockwell-MBB X-31 performing a "Cobra stall" (2:24)". YouTube.
  12. "Video of a Saab 35 Draken performing a Cobra Barrel roll. (3:51)". Youtube.
  13. "Video of Su-30 performing a "Cobra Hover". (0:13)". Youtube.
  14. See for example the German article.
  15. Hall, Rex; Shayler, Davide; Vis, Bert (2005). Russia's Cosmonauts: Inside the Yuri Gagarin Training Center. Chichester, UK: Praxis Publishing. pp. 335–6. ISBN 0-387-21894-7.
  16. Ulf Edlund & Hans Kampf (2005). Draken 50 år, FLYGHISTORISK REVY. Sweden: Svensk flyghistorisk förening.
  17. Speciell förarinstruktion för J 35B Draken. Sweden: Swedish air force. pp. 73, 74.
  18. "Article on how it was to fly the Saab 35".
  19. "F10 kamratförening: filmer, clip Tisoe".
  20. "Interview with Ari Saarinen on the Saab 35 Draken, Youtube".
  21. "THE UNKNOWN STORY OF THE SYRIAN MIG-21 PILOT WHO DEVELOPED THE COBRA".
  22. Bill Sweetman, Aviation Week & Space Technology, Jun 24, 2013, quoting Sukhoi chief test pilot Sergey Bogdan
  23. Mitko Ian. "Sukhoi SU-35 fighter has all the right moves at Paris Air Show". Gizmag.com. Retrieved 18 June 2013.
  24. https://www.youtube.com/watch?v=eNY9sCgcyU0
  25. John Dovishaw, Russia Mig does Cobra Maneuver at Dayton Airshow, retrieved 8 February 2019
  26. Venci Dimitrov, Миг-29 управляван от Ген. Радев /Авиошоу 2014, летище София/, retrieved 8 February 2019
  27. "Cobra Maneuver ?". International journal of turbo & jet-engines. 11. Retrieved 23 March 2011.
  28. https://www.youtube.com/watch?v=RVXFNakwDiw

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