Cobra maneuver

In aerobatics, the cobra maneuver (often shortened to the cobra), also called dynamic deceleration,[1][2] among other names, 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.

Cobra maneuver
"Dynamic deceleration"
The cobra maneuver performed by a Swedish Saab 35 Draken

The maneuver relies on the ability of the plane to be able to quickly change angle of attack (alpha) without overloading the airframe,[3] and sufficient engine thrust to maintain nearly constant altitude through the entire move,[4] 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,[5] 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.[6]

The maneuver is typically performed at air shows,[7] but could be used as a last-ditch maneuver to force a chaser to overshoot in close-range air combat.[3][8] The maneuver has never been verified in real combat, although it has been used during mock dogfights[3] and border protection.[9][10]

Description of the cobraEdit

 
Cobra maneuver schematic of the MiG-29 in profile, showing alpha numbers.

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.

AerodynamicsEdit

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. This is because conventional aircraft are designed to lack this "instability" for safety reasons, and can thus not execute the maneuver by conventional means. Some conventional aircraft can however perform maneuvers reminiscent of the cobra but do so with differences which disqualify them as real cobra maneuvers; such as: performing at low speed, changing alpha too slowly and using advanced thrust control so as not to gain altitude (i.e. performing a forced vertical climb with no thrust, usually ending with the aircraft performing a short climb or stalling instead of completing the cobra movement), among other examples.[11][12]

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)Edit

 
Cobra maneuver schematic of the Su-27. It is one of the tests of supermaneuverability for the Su-27.

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°.[4] 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 combatEdit

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 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.[13] 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.[3]

NamesEdit

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. Kort Parad, Swedish for Short Parry (literal) or Beat Parry (English equivalent fencing term),[15] the original Swedish name for the maneuver, putting the aircraft in the perfect position to riposte. Zero speed maneuver (Arabic: مناورة السرعة صفر), the Syrian name for the maneuver, referring to the way the plane loses speed during the maneuver.

The maneuver has also been given the name dynamic deceleration as a more scientific name.[1][2]

HistoryEdit

The cobra maneuver came to public attention when Soviet test pilot Viktor Pugachev performed it at the Le Bourget Paris air show in 1989 using a Sukhoi Su-27.[4] The tactic was previously unknown to the public and it was quickly named after Pugachev. But apparently Pugachev was not the first Soviet pilot to perform the cobra. Another Soviet test pilot by the name of Igor Volk performed it previously while testing aircraft behavior at high super-critical angles of attack, up to around 90°.[16]

SwedenEdit

Decades prior to Pugachev showing off his cobra, during the early 1960s the maneuver had been performed by Swedish pilots flying the Saab 35 fighter jet.[17] 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.[18] 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.[17] The result was the cobra maneuver. 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.[17] The Swedish test pilots who discovered the cobra were Bengt Olow [sv] and Ceylon Utterborn [sv], who developed the technique around 1961–1963.[19]

 
Saab 35 Draken executing a sharp turn, visually reminiscent of a cobra

The Swedes named the maneuver "kort parad", or "short parry" in English. 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.[17][3] 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.[20]

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.[3]

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.[17] Apparently, the cobra maneuver was used during some of these engagements, surprising the Soviets.[9] 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.[3] 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.[3]

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[3][17] and articles,[9][20] long after the Soviets had been credited with its discovery.

FinlandEdit

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 drew praise over the radio from the British pilot.[10]

AustriaEdit

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.[21] It is unknown whether the Austrians used this as a combat maneuver or just as training against super stall.

SyriaEdit

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.[22] 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.[22]

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.[22]

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 and 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.[22]

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.[22] The cobra quickly became a standard part of defensive tactics for Syrian Mig-21s.

Pakistan and EgyptEdit

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, as well on their Chinese counterparts, Chengdu F-7s.[22]

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.[22]

Soviet UnionEdit

Research and developments on supermaneuverability started in USSR in the early 1980s by Central Aerohydrodynamic Institute, Gromov Flight Research Institute, Sukhoi and Mikoyan.[23]

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 who publicly demonstrated the maneuver in the Su-27 aerobatics display at the Le Bourget airshow of 1989.[23]

Derivatives of the cobraEdit

There are several derivatives of the cobra which all initiate it 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.[24] 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.[25]

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.

Example aircraftEdit

Examples of aircraft capable of the maneuver.

Production aircraftEdit

Experimental aircraftEdit

See alsoEdit

ReferencesEdit

  1. ^ a b c "Air Show - Paris 1989". youtube.com. 1989. Archived from the original on 13 December 2021. Retrieved 14 March 2021.
  2. ^ a b "rec.aviation.military newsgroup: Su-27: The history". aviastar.org. 1999. Retrieved 14 March 2021.
  3. ^ 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.
  4. ^ 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.
  5. ^ Abzug, Malcolm J.; 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.
  6. ^ Benjamin Gal-Or. "Vectored Propulsion, Supermaneuverability, and Robot Aircraft". Springer Verlag, 1990, ISBN 0-387-97161-0, ISBN 3-540-97161-0.
  7. ^ "Example of the cobra being performed at an air show". YouTube. Archived from the original on 13 December 2021.
  8. ^ Crane, David. "Air-to-Air Fighter Combat Application of Pugachev's Cobra Maneuver: Busting the Western Myth". Defense Review. Retrieved 14 January 2012.
  9. ^ a b c "F10 Kamratförening J 35 Draken". www.f10kamratforening.se (in Swedish). 20 October 2019.
  10. ^ a b "Interview with Ari Saarinen on the Saab 35 Draken, Youtube". YouTube. Archived from the original on 13 December 2021.
  11. ^ "Video of F-22 performing a "fake" Cobra (2:06)". Archived from the original on 13 December 2021 – via YouTube.
  12. ^ "Video of F-22 performing "fake" Cobra's". Archived from the original on 13 December 2021 – via YouTube.
  13. ^ Bill Sweetman, Aviation Week & Space Technology, 24 Jun 2013, quoting Sukhoi chief test pilot Sergey Bogdan
  14. ^ See for example the German article.
  15. ^ Flyghistorisk revy, System 37 Viggen. Svensk Flyghistorisk förening. 2009. p. 212.
  16. ^ 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.
  17. ^ 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.
  18. ^ Speciell förarinstruktion för J 35B Draken. Sweden: Swedish air force. pp. 73, 74.
  19. ^ 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.
  20. ^ a b "Article on how it was to fly the Saab 35". 2011.
  21. ^ "F10 kamratförening: filmer, clip Tisoe".
  22. ^ a b c d e f g h "THE UNKNOWN STORY OF THE SYRIAN MIG-21 PILOT WHO DEVELOPED THE COBRA". 7 August 2019.
  23. ^ a b Bjušgens, Georgij S. (1993). CAGI - centr aviacionnoj nauki (in Russian). Nauka. ISBN 978-5-02-007017-2.
  24. ^ Gordon, Yefim (1999). Sukhoi Su-27 Flanker: Air Superiority Fighter. Airlife Publishing. ISBN 1840370297.
  25. ^ "That Magnificent Flying Machine". Time. 7 June 1982. Archived from the original on 30 September 2007. Retrieved 30 April 2010.
  26. ^ Mitko Ian (18 June 2013). "Sukhoi SU-35 fighter has all the right moves at Paris Air Show". Gizmag.com. Retrieved 18 June 2013.
  27. ^ Archived at Ghostarchive and the Wayback Machine: "Sukhoi Su-57 PAK FA / T-50 doing the Pugachev's Cobra at MAKS 2013 ПАК ФА". YouTube.
  28. ^ John Dovishaw, Russia Mig does Cobra Maneuver at Dayton Airshow, archived from the original on 13 December 2021, retrieved 8 February 2019
  29. ^ Venci Dimitrov, Миг-29 управляван от Ген. Радев /Авиошоу 2014, летище София/, archived from the original on 13 December 2021, retrieved 8 February 2019
  30. ^ "Cobra Maneuver ?". International Journal of Turbo & Jet-engines. 11. 1994. Retrieved 23 March 2011.
  31. ^ "General Dynamics NF-16 VISTA". YouTube.
  32. ^ "2018 Chinese J-10B 殲10矢量 TVC performing vertical take-off & Cobra MANOEUVRE & roll". YouTube.

External linksEdit