In aerobatics, the cobra maneuver (or just the cobra), also called dynamic deceleration, 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 making the plane into a full-body air brake, momentarily stalling the plane, 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, and sufficient engine thrust to maintain nearly constant altitude through the entire move, 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, 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.Benjamin Gal-Or. "Vectored Propulsion, Supermaneuverability, and Robot Aircraft". Springer Verlag, 1990, , .
The maneuver is typically performed at air shows, but could be used as a last-ditch maneuver to force a chaser to overshoot in close-range air combat. The maneuver has never been verified in real combat, although it has been used during mock dogfights and border protection.
Etymology The maneuver has many names, but it is most commonly known as the cobra or the cobra maneuver in the respective language; for example: (Kobra), . 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. 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"), the Swedish term for the fencing manoeuvre "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.
Maneuver description 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 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.
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) 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°. 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.
Use in combat 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.Bill Sweetman, Aviation Week & Space Technology, 24 Jun 2013, quoting Sukhoi chief test pilot Sergey Bogdan 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.
History Sweden
During the early 1960s, the maneuver was developed and performed by Swedish pilots flying the Saab 35 fighter jet. 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. 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. 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. The Swedish test pilots who discovered the cobra were and , who developed the technique around 1961–1963.
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. 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.
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.