The Scissors is an aerial dog fighting maneuver commonly used by military fighter pilots. It is primarily a defensive maneuver, used by an aircraft that is under attack. It consists of a series of short turns towards the attacking aircraft, slowing with each turn, in the hopes of forcing the attacker to overshoot. Performed properly, it can cause the attacking aircraft to move far enough in front to allow the defender to turn the tables and attack. The scissors is a close-maneuvering technique, and as such, is really only useful when defending against guns or low-performance missiles. It was a major technique from World War I to the Korean War, but is much less common today. The introduction of high-angle missiles makes it much less effective, as the attacker can shoot even when the defender is not in front of them. Modern aircraft also make it difficult to use this technique as they maintain energy much better than earlier designs and the maneuvering limits are often the pilot's physical limitations, not the aircraft. In fact, for many years now, fighter pilots flying aircraft with even a reasonable thrust-to-weight ratio and average wing loading are well advised to avoid engaging in a scissors maneuver, since any turning, rolling or slow-speed disadvantage the pilot's aircraft might have with respect to that of his opponent (or pilot skill in energy assessment and management techniques) will quickly become evident in the scissors, and lead to his defeat in short order. Basic fighter maneuvering theory recognizes two different types of scissors maneuvers; the flat scissors and the rolling scissors.
The flat scissors is the simpler of the two to explain. The flat scissors maneuver commonly results when two fighters of similar capability encounter each other at similar speeds and in the same plane of motion, and the fighter approaches the defending "bandit" (enemy fighter), usually from the bandit's rear hemisphere, and has failed to press an initial positional and angular advantage into a kill, and has "overshot", or passed behind the bandit. (To overshoot is to fly from an AOT (angle-off-tail: the angle between the nose of the attacker and an imaginary extended line from the nose through the tail of the bandit and extending behind it into the air) of less than 90 degrees to an AOT of greater than 90 degrees.)
As such, an attacking pilot who finds himself in a flat scissors has transitioned from an offensive to a neutral engagement, and has lost his offensive advantage, as it represents a failure to press an initial attack into a kill, and the scissors can be difficult to disengage from without being exposed to the weapons of the bandit at close range. The bandit pilot is often surprised initially by what was likely an unobserved attack from the rear, and while he has survived a highly defensive situation that has become a somewhat neutral encounter after the overshoot, the bandit pilot must still react quickly. After the co-planar overshoot, if the bandit chooses to remain engaged with a nose-to-nose turn (that is, a turn toward the attacker in the general direction of the attacker's direction of flight) to either gain the advantage, or maintain the neutral situation, the flat scissors is a common result.
Once initiated by the bandit, it is also difficult for the bandit to disengage from a flat scissors without being exposed to danger from the weapons of the other aircraft. An experienced and patient bandit might be able to turn the scissors to his advantage, however. The bandit possessing superior turning capability may also initiate a flat scissors offensively, although this is certainly a dangerous gambit (as it involves allowing the attacker to approach to close range from behind), but one that may be forced upon the bandit by the attacking fighter's superior engine power or speed: after becoming aware of a more or less co-planar attack from his rear hemisphere, the bandit uses co-planar energy techniques (using power reduction, uncoordinated flight, flaps, slats or speed brakes) without moving out of the initial plane of the attack. By remaining in the same plane of the attack, the bandit might be able initially to deceive the attacker about the two airplanes' rate of closure, quickly placing the attacker into a position in which a successful attack cannot be made due to close proximity, too much angle-off-tail, or both; in the same circumstances, by not adopting hard evasive maneuvering, the bandit might also convince the attacker to reduce speed to prevent the overshoot, (the attacker has thereby given up a major advantage in the hopes of getting a quick kill, believing that the bandit has not seen him), and thereby, however, mistakenly played into the strengths of the slower but better turning bandit.
In any case, if both pilots' reaction to a co-planar overshoot with only a minor air-speed differential is a co-planar nose-to-nose turn, then a flat scissors will often result.
The goal of the flat scissors is to get into a successful firing position; the attacker and bandit each pull their fighters' noses toward the other, executing consecutive reversing nose-to-nose turns, while trying carefully to use energy depletion methods, or using slightly oblique, out-of-plane turns to get behind the enemy. The resulting flight path looks like scissors in the sense that both fighters approach each other, cross over, and then separate again, over and over while the scissors continues. The maneuver results when both fighters initially bank (or "roll") about 90 degrees toward the opponent and turn (In the theory of fighter combat turning is often called "pulling", due to the pilots' efforts to tighten their turns by pulling back on the control stick - the banked attitude would cause the aircraft to turn in any case in a sustained "1 G" turn, but pulling back on the stick serves to "tighten" (decrease the radius of) the turn. All level turns result in a loss of speed and energy, and the tighter the turn - the more "pull" used - the greater the resulting loss of speed and energy, and in the pilot experiencing higher "g-forces" in the turn) toward the opponent until their flight paths cross, at which point each pilot flies outward trying to assess if he has an offensive advantage or disadvantage, and then reverses his turn (to avoid flying out too far into a disadvantageous position, where a quick turn "reversal" (a 180 degree roll accompanied by the resulting turn) by the enemy would result in the enemy pulling in behind the pilot) by rolling opposite the initial turn by 180 degrees of bank, and pulling toward the opponent again.
During the repeated brief passes it is occasionally possible to get off what is called a "snap shot" (A snap shot is an opportunistic shot of brief duration, brief because of the rapid change of the LOS (line-of-sight) to the target caused by the aircraft's maneuvering in different planes of motion. The preferable "tracking shot" opportunity lasts longer; as long as the attacker can maintain a constant LOS to the bandit, accomplished by maneuvering in the same plane of motion as the bandit. The process of getting into the same plane of motion as a bandit and setting up a tracking shot is called "getting into the saddle" or "saddling up".) at the opponent fighter, although due to the typically close range of the scissors, usually only guns may be used for this "snap shot". This process of 180 degree rolls and reversed turns can be repeated many times while each pilot seeks a positional advantage through energy management, and seeks to avoid a disadvantage.
In the flat scissors, the turns and maneuvering are accomplished approximately all on one plane, an imaginary flat surface (thus the term "flat" scissors) that is not necessarily horizontal, although the horizontal is a common case. The flat scissors continues until either one fighter (usually the fighter with better rolling or instantaneous turning characteristics) gains an advantage (usually due to an ability to reduce speed effectively while retaining sufficient roll and turn response from his aircraft) and gets behind his opponent and successfully shoots him down (with either a snap shot or tracking shot), or one of the pilots maneuvers successfully to disengage from the scissors, and gets to a safe distance to make an escape, or attempt a new attack.
The flat scissor if flown to its conclusion is usually a contest of who can fly more slowly while maintaining sufficient controlled maneuverability to get into position for a kill as quickly as possible.
As mentioned above, the objective of the flat scissors is to coerce an attacker with superior power or initial speed and energy to overshoot and engage in a turning fight which he will probably lose if the attacker has inferior turning characteristics than the bandit. For this attacker the objective is to avoid the scissors against such a bandit. There are at least two ways an attacker can avoid becoming engaged in a flat scissors.
The vertical counter-maneuver is especially effective for an attacker who possesses an advantage in thrust-to-weight ratio (sometimes called "power-loading") or energy over the bandit, but who conversely may have a worse instantaneous and/or sustained turn rate than the bandit. Such an attacker who recognizes that he is about to overshoot a bandit could, upon seeing the bandit's initial turn, pull up into a vertical zoom or power climb or a high yo-yo (a climbing turn in the same direction as the defender's horizontal turn). Even if the attacker has overshot the bandit this vertical maneuver will help to preserve the attacker's total energy and allow the attacker at or near the top of the climb to nose down and re-establish contact with the bandit's rear quarter. The bandit at this time having probably pulled a hard turn will have lost energy as a consequence of the "high-G" turn. This vertical maneuver also has allowed the attacker to put distance between itself and the bandit that might serve to foil a shot due to being out of range. The attacker is now in the position to dive in for another attack, or to disengage, therefore maintaining its offensive stance. The bandit, on the other hand, has depleted its energy in its initial turn, is below the attacker, and is possibly in a worse position than when the fight originally started. Note however that the aim of the attacker possessing an aircraft with superior power or energy, or inferior turning capabilities, is to avoid the scissors maneuver.
For an attacker with a lower thrust-to-weight ratio or initial energy but who possesses a turn performance advantage, a better option upon seeing the bandit perform the initial hard turn is to take advantage of the bandit's error and avoid the overshoot. This might require reducing energy/air speed using flaps, reduced throttle settings, or other means at its disposal. Energy is valuable, and should only be depleted as necessary to avoid the overshoot. Excess depletion of energy is never a good idea. The goal here is for the attacker to remain in the rear quarter of the bandit, and for the attacker to employ its turning advantage to turn inside the bandit's turn, seeking a tracking shot opportunity. Thus the point again is to use an advantage to avoid entering the scissors maneuver. If the bandit with inferior turning capabilities commits the serious error of engaging in a flat scissors, then his inferior turn performance will soon become apparent, and the skilled attacker can quickly maneuver behind the bandit to obtain a successful shot. If the aircraft are of similar power and turning capabilities, however, a scissors might be unavoidable, and the fight becomes one of the skill of the pilots involved. However, an attacker is often in hostile airspace, and will have limited time due to fuel constraints to engage in a prolonged turning fight. This puts an attacker, even in a similarly capable aircraft, at a significant disadvantage.
The rolling scissors maneuver is somewhat different. Like the flat scissors, the rolling scissors maneuver is typically an engagement of two fighters of similar capabilities with respect to their thrust-to-weight ratios (and thus similar climbing capabilities), turning characteristics and wing loading. Whereas the flat scissors typically results from a failed attack resulting in a slow speed differential overshoot of the defender by the attacker, the rolling scissors usually results from a failed attack at higher speed, and overshoot. The rolling scissors is also often initiated by the attacker first diving from a higher altitude at the bandit and overshooting the bandit in the vertical, as well as horizontal plane.
As the attacking aircraft makes its failed attack and overshoots, the bandit immediately initiates a pull-up (a "zoom" climb, trading airspeed for altitude) into the vertical to further aggravate the attacker's overshoot by slowing the bandit's speed while maintaining its total energy, and increasing the speed of separation of the two aircraft. Both of these factors contribute to a larger overshoot, and an increased offensive potential for the bandit. Then the bandit rolls his aircraft toward the attacker (In ACM terminology this is called "putting his lift vector" on the opponent. The lift vector is more or less a line perpendicular to the plane of an aircraft's wings.) that has overshot him, and pulls his nose toward the attacker. This move is similar to a turn reversal in the horizontal plane, and both of these moves give the bandit the offensive after an overshoot. A skilled bandit at this point might be able to make a successful snap shot with guns, or possibly a short range missile shot, and no scissors results.
More typically what happens next in the rolling scissors is that the initial attacker, aware of his vulnerability caused by the overshoot, also rolls his aircraft, and pulls his nose toward the bandit's aircraft. Due to the two components of the initial overshoot (vertical and horizontal), if the pilots keep attempting to turn their noses toward their opponent, then energy management, elements of roll and turn (as in the flat scissors; although in the rolling scissors there are no reverses of turn), as well as climbs and descents will be required to maintain maneuvering that might, if successful, result in a position from which a shot can be made. What evolves therefore in the rolling scissors is a maneuver that is essentially two aircraft barrel-rolling, involving rolling and looping motions, climbing and descending and turning while the aircraft rolls around its longitudinal axis. The barrel roll has a vertical component which the aileron roll lacks. Unfortunately, the two maneuvers are often confused in many contexts, or are used as if they are interchangeable terms. They are not. The "snap roll" is yet another maneuver, commonly seen in aerobatics performances, and is similar to a flat spin (thus involving an aerodynamic stall) and is not typically of any use in ACM) around each other's flight path, which might look like two interwoven cork-screws, or a double helix. The more barrel rolls that are flown in the rolling scissors, the more nearly the rolls become horizontal only, as each pilot attempts to deplete enough forward speed to place his fighter behind the other.
By imagining the difference between the initial conditions of the flat and rolling scissors, one can see how that the addition of the vertical component of the initial overshoot turns the rolling scissor engagement into a three-dimensional rolling encounter. Unlike the flat scissors which results in a fight to roll and turn the plane quickly, reverse turn quickly, and attempt to deplete energy in order to get behind the other aircraft to set up a successful shot, the contest in the rolling scissors is still one of successfully controlling forward motion so as to maneuver behind the other aircraft (get "on his six" in fighter pilot terminology). In the rolling scissors, the successful pilot is the one who best manages his energy in the climbs and descents of the barrel rolls, as they eventually come to have a larger overall effect on the reduction of forward speed than the simpler strategies used to reduce thrust, add drag or time the rolls and turns in the flat scissors.
The rolling scissors decidedly favors an aircraft with a power advantage over a bandit, so it is of some offensive value even to this day, although it is a difficult attacking maneuver and is very unforgiving of poor technique.
To disengage from a rolling scissors, the best opportunity is when the pilot is on the downward part of one of his barrel rolls, preferably behind his opponent (but obviously not quite in a position to get a shot), and then accelerate in a power dive to try to extend away to a safe distance to escape, or initiate a new attack.
Situational awareness in both of the scissors is critical, as flight paths become very predictable to an outside observer, and an unseen enemy could easily approach this mentally demanding situation and attack with near impunity. Also, particularly in the rolling scissors (due to the vertical component of the maneuvering), awareness of the ground and other obstacles must be maintained while most of the pilots' attention is demanded by the close and hard maneuvering required of the scissors engagements.
As stated above, the modern fighter pilot is well advised to avoid the scissors engagements, as they do not favor the characteristics of many modern fighter aircraft: aircraft with medium-to-high wing loading, powerful engines (and attendant high rates of climb allowing for significant maintained vertical maneuvering capabilities), and long-range missile weapons. The scissors are also very physically and mentally taxing on the pilots involved, and can lead to a dangerous loss of situational awareness due to fixation on the one other enemy aircraft involved, leading to vulnerability to other enemies that may be flying in the area unobserved, or ground threats such as surface-to-air missiles.