Air to air combat began in the World War I. Aircraft were originally used for reconnaissance and in that role Allied aircraft played a key role in finding von Kluck's swerve toward the Marne and that key defensive battle early in WWI.

Because such information was useful, it was also deemed useful to deny it to the enemy. Early efforts were makeshift, and even bricks were used in the attempt to down enemy aircraft. Anti aircraft artillery did not exist and had to be developed as conventional guns could not fire at sufficient angle to target aircraft.

Air-to-air combat became serious when Anthony Fokker developed the first synchronizer gear which permitted machine guns to be fired within the propeller arc without sawing the prop off. This allowed the introduction of fighter aircraft. Fighter pilots aimed their weapons by maneuvering the aircraft. This led to a stylized series of maneuvers as pilots tried to gain a firing position. Ambush is the preferred tactic, as it is very difficult to outfly a skilled opponent, even with superior aircraft.

The first key tactical innovation was Allied, with the formation of specialized squadrons and the introduction of unit tactics, the fighter sweep, and the fighter element system, where a wingman would be responsible for protecting his wingman and vice versa. The next major innovation was German, the "flying circus" system created by the Oswald Boelcke, and later perfected under Baron Manfred von Richtofen, the Red Baron of Peanuts fame. Under the circus system whole groups of picked flyers could be switched from sector to sector as required to attain local air superiority The development of aerial bombardment created additional demands for interceptor aircraft, in order to prevent the damage wrought by bomber aircraft and zeppelins. In essence, fighter aircraft are defensive weapons, used to prevent bombing, or to deny the enemy information sought by its reconnaissance arm.

The key aspects of air to air combat were defined during the first world war. Aircraft performance is often critical, with rate of turn, rate of climb, speed, acceleration, ability to dive, roll rate and armament always playing key points. Generally, different aircraft offer different advantages, with speed being the advantage of the British SE-5a, ruggedness of the French Spad, turn rate for the Sopwith Camel and rate of climb for the Fokker Triplane. These advantages may switch from one aircraft to the other at differing altitudes. Airframe weakness may also play a role, with the nimble French Neiuport displaying an alarming tendency to shed its upper wing during violent maneuvers.

For pilots key aspects seem to be training, experience, vision, aggression and aircraft identification skills. Combat experience seems the most critical factor, with pilots being most vulnerable during their first dozen or so missions. They suffer from air blindness which is a catchall term that describes the inability of green pilots to spot other aircraft because they search poorly. Also, quick reactions are required in combat so experience is necessary. Vision is critical because the person who sees his opponent first often gains a critical advantage, and often the opportunity for an ambush. Aircraft identification skills are often down played, but critical because misidentification can lead to fatal mistakes or delays.

During the interwar years fighter aircraft advanced steadily in terms of speed, altitude and other performance characteristics but the essential nature of aerial combat remained unchanged. The Spanish Civil War contributed greatly to the refinement of Luftwaffe tactics and aircraft, particularly the Messerschmitt Bf-109.

The first real innovation in air to air conflict was British, with the invention of radar. Radar permitted a limited number of aircraft to be vectored onto attackers, making the use of fighter aircraft particularly efficient. Without radar, Britain would certainly have been defeated during the Battle of Britain, and Nazi Germany victorious during World War II. Radar also permitted the development of specialized night fighters such as the Beaufighter and Northrup P-61 Black Widow.

The second major innovation was German, with the use of fighter aircraft to escort bombers to their targets. The key characteristic of an escort fighter was long range, with the P-51 Mustang as the premiere escort fighter of the war. Fighter escorts sought to keep defending fighters away from their bombers or reconnaissance planes, so those aircraft could fulfill their missions.

The next real breakthrough came with the introduction of jet aircraft, primarily with the Messerschmitt Bf-262 jet fighter. Jet aircraft offered matchless speed and rate of climb, with the difference being so dramatic as to render propeller powered fighters immediately obsolete. Earlier introduction of jet fighters might very well have altered the course of the war for Germany, but limited numbers and lack of fuel greatly limited the impact of the new German jets. Tactically, the introduction of jet aircraft reinforced the importance of three dimensions in air-to-air combat. Physics teaches that an object within a gravity well that is at a higher altitude operates at a higher energy state. In practical terms that means altitude can be traded for speed. Propeller aircraft climb much less efficiently than jets, so they recover their energy state slowly. This means that a faster, more powerful aircraft can 'use the vertical' to cut the corner on a slower aircraft that might turn tighter in the horizontal plane. It is for this reason that jet combat is often described as a vertical scissors.

Two near simultaneous developments anchored air-to-air combat during the late fifties and up through the 1980's. The first is the development of supersonic aircraft abetted by improved aerodynamics particularly with the 'coke bottle' fuselage and afterburning jet engine. Afterburners inject fuel directly into a jet's hot exhaust where it is ignited in an almost rocket effect. The process uses lots of fuel, but it can produce a significant and immediate increase in thrust. Without afterburners, all current jet fighters would be limited to subsonic flight for a number of reasons. However, the high fuel consumption limits aerial combat to minutes, making fuel management critical. The long running fights of WWII are things of the past .

The second key development is the development of the air-to-air missile. Rockets had been used as aerial weapons against bombers during both world wars, but they were unguided and useless against aircraft operating in a loose formation. There are two basic types of air-to-air missile, heat seeking and radar guided. The US AIM-9 Sidewinder family is typical of the heat seeking variety. Early versions would chase after a jet exhaust heat which meant that the aircraft still had to be maneuvered into a rear quarter attack, much like the combats typical of the first two world wars. The vertical scissors still reflects jet combat today.

The US AIM-7 Sparrow family and the Navy's Phoenix missile represent typical radar guided weapons. Radar guided weapons are considered all-aspect weapons because they can be launched at an aircraft moving at any aspect relative to attacking fighter, so long as a radar lock can be gained.

However these missiles suffer from significant disadvantages. They require complex systems that are prone to failure. Radar missiles require the attacking plane to emit radar beams in order to acquire and attack targets. These radar beams betray the fighter's presence and rough locations as enemy aircraft carry their own specialized radar detectors, usually at a range far greater than either the radar or missile. Sparrow missiles require the launching aircraft to illuminate the targeted aircraft with their radar throughout the entire attack. If the beam is broken for any reason [eg counterattack, mechanical failure, etc] the attack will fail.

The Phoenix and AMRAAM missiles are much more advanced. And expensive. Each carries its own radar and attack computers, so the missile itself can conduct the attack once it is fired. Like the Sidewinder, these missiles are 'fire and forget' weapons which allow the attacking fighter to change tasks once the weapon is launched, a significant advantage. However, their computer brains prove more easily 'spoofed' than a human Radar Intercept Officer. And their long range makes it relatively easy to attack a friendly target, leading to friendly fire losses. It is partly for this reason that Navy F-14 Tomcat fighters carry a telescopic TV system, for target identification.

The development of missiles did not remove the usefulness of the more traditional gun in combat, though missiles became dominant. Early versions of the F-4 Phantom carried no gun. Vietnam war experience returned the gun in the later F-4E variant.

The 1980's brought two significant improvements. The first is that the newest generation of US fighters, the F-15 Eagle and F-16 were the first jet fighters whose thrust-to-weight ratio was greater than one to one. This removed many limitations in how these aircraft could be maneuvered. Because aircraft are turned by moving control surfaces, any turn in an aircraft requires a loss of speed. A violent turn may shed speed that cannot be soon recovered. Enough such turns and combat maneuvers may become all but impossible. We say that a fighter in such circumstances is at a low energy state. Though it can turn tighter, it is for this reason that US fighter tactics for the F-4 Phantom aircraft limit maneuvers to four gees. The Phantom bleeds off too much speed in turns.

The current generation in fighters, which includes the MiG-29 and F/A-18 Hornet can sustain turns of greater than seven gees, in a vertical corkscrew climb. In essence, they are not G-limited tactically. In fact, the primary limit is the pilot's g-tolerance. However, such power requires using the afterburners. An hour's worth of fuel can be burned in a minute. High fuel consumption is the primary penalty of such aircraft. No current jet fighter can sustain supersonic flight for this reason. All are subsonic aircraft with a limited supersonic capability. The new US F-22 fighter under development represents a leap as substantial as the move from propellers to jets for that reason, at least in part because of its supercruise capability to sustain supersonic flight.

The second great leap came with the development of the AIM-9L version of the Sidewinder Missile. Previous versions of the Sidewinder could only be used in rear-quarter attack, as they needed a hot tailpipe to target. The niner-lima Sidewinder was the first version capable of detecting engine inlet IR. In essence, the 9L and later missiles can see through a jet engines compressor section and read the heat of the combustor. This changed the Sidewinder from a rear-aspect weapon to an all-aspect weapon. During the 1982 Israeli invasion of Lebanon the AIM 9L had far more to do with the annihilation of the Syrian air force in combat than the real superiority of Israeli pilots and F-15 and F-16 Falcon aircraft. British and Argentine pilots also cited the 9L as decisive during the Falklands War.

Future air-to-air combat may involve more drones than piloted planes. The biggest reason for this is that pilots cannot tolerate the gee-loads generated by modern aircraft. G-tolerance problems first appeared in the late thirties, as hard maneuvers force blood away from the head and down into the legs. The G-suit was developed to moderate this problem. It contains inflatable bladders which force blood back into the upper body during violent maneuvers. However, the F-16 can sustain nine gees! Even with g-suits and extensive weight training humans black out at that heavy a load, a process marked with narrowing vision. Artificial intelligence programs have been developed to take over until the pilot can recover. However, the continuing development of airframes and engines will soon pass beyond the ability of any human to tolerate.

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