Pugachev's Cobra

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

In aerobatics, Pugachev's Cobra (or Pugachev 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, before dropping it back to normal flight. It uses potent engine thrust to maintain approximately constant altitude through the entire move.[1] Some have speculated that the maneuver may have use in close range combat,[2] although it has never been used.

It is an impressive trick to demonstrate an aircraft's pitch control authority, high angle of attack (AOA) stability and engine-versus-inlet compatibility, as well as the pilot's skill. The maneuver is named after the Soviet test pilot Viktor Pugachev, who performed it in 1989 at the Le Bourget Paris air show.[1] But Igor Volk was the first who tested aircraft behavior at high super-critical angles of attack (around 90°) and performed aerobatics such as the "cobra" maneuver.[3]

Description

In the case of the Su-27, the pilot initially disengages the angle of attack limiter of the plane, normally set at 26°.[1] This action also disengages the g limiter. After that the pilot pulls back on the stick hard. The aircraft reaches 90–120° angle of attack 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 torque, thus making the aircraft pitch forward. At that time the pilot adds power to compensate for the lift loss.

In a properly performed Pugachev's Cobra, the plane maintains almost straight flight throughout the maneuver. The plane does not roll or yaw in either direction. Proper entry speed is significant because, if entering at too low a speed, the pilot might not be able to accomplish the maneuver. Entering at too high a speed might result in airframe damage due to the high g-force or for the pilot to lose consciousness.

While Pugachev's Cobra can be executed using only standard aerodynamic controls, it could be achieved more easily with modern thrust vectoring such as the case of F-22 Raptor which utilizes 2D thrust vectoring. In the latter case it would be an example of supermaneuverability,[4] specifically poststall maneuvering. The Herbst maneuvering and the helicopter maneuver are other examples of the recent growing use of vectored thrust in 4.5 and fifth-generation jet fighters, manned as well as unmanned.[5]

Potential use in combat

The Sukhoi Su-27 is capable of the manoeuvre.

It has been speculated that the maneuver could theoretically be useful when a combatant is being pursued closely by an opponent at a somewhat higher altitude. By executing the Cobra, a sufficiently closely pursued aircraft may suddenly slow itself to the point that the pursuer may overshoot it, allowing the previously pursued aircraft to complete the Cobra behind the other. This may give the now-pursuing aircraft an opportunity for firing its weapons, particularly if a proper pointing aspect (facing toward the former pursuer) can be maintained. Maintenance of the proper aspect can be facilitated when the aircraft employs thrust vectoring and/or canard control surfaces.

The disadvantage of performing this maneuver is that it leaves the airplane in a low speed/low energy 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[6]. 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.

Examples of aircraft capable of the manoeuvre

Production aircraft

Experimental aircraft

See also

References

  1. 1 2 3 4 5 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.
  2. ↑ Crane, David. "Air-to-Air Fighter Combat Application of Pugachev's Cobra Maneuver: Busting the Western Myth". Defense Review. Retrieved 14 January 2012.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ Benjamin Gal-Or. "Vectored Propulsion, Supermaneuverability, and Robot Aircraft". Springer Verlag, 1990, ISBN 0-387-97161-0, ISBN 3-540-97161-0.
  6. ↑ Bill Sweetman, Aviation Week & Space Technology, Jun 24, 2013, quoting Sukhoi chief test pilot Sergey Bogdan
  7. ↑ Mitko Ian. "Sukhoi SU-35 fighter has all the right moves at Paris Air Show". Gizmag.com. Retrieved 2013-06-18.
  8. ↑ https://www.youtube.com/watch?v=dggtma54dZc%5Bunreliable+source?%5D
  9. ↑ "Cobra Maneuver ?". International journal of turbo & jet-engines. 11. Retrieved 23 March 2011.
  10. ↑ https://www.youtube.com/watch?v=jqiDEcfSnXs%5Bunreliable+source?%5D
  11. ↑ https://www.youtube.com/watch?v=GrBx6G2O6A4&t=36s%5Bunreliable+source?%5D

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