The A-10A is a specialized close air support (CAS) aircraft. That is, it is designed specifically to act as "flying artillery" in support of ground troops in close proximity to the enemy—in general, within five miles of the front lines. Built around the awesome GAU-8A 30mm rotary cannon, the A-10's primary targets are enemy tanks and other armored vehicles. The big gun is backed up by other anti-armor weapons, most notably the AGM-65 Maverick missile, the GBU-12 Paveway 500 lb laser guided bomb (LGB) and the CBU-87 combined effects munition Other weapons, such as the Mk.82 Snakeye 500 lb retarded bomb, the (outdated) Mk.20 Rockeye cluster bomb (CBU), 2.75" rocket pods, and napalm bombs, can be used against trucks, troops and field installations.
In order to properly support ground troops, CAS aircraft must be able to stay on station, or loiter, near the front lines for extended periods. The A-10's high bypass TF34 turbofans were selected mainly for their excellent fuel efficiency, which together with the Warthog's internal fuel capacity of 10,650 lbs, allows the A-10 to loiter for nearly 2 hours over a radius of 250 n.mi., whereas high performance jets such as the F-16, can only loiter for 15-20 minutes at a similar radius.
Speed was definitely a secondary (or tertiary) criterion in the design of the A-10. More emphasis was placed on maneuverability in the horizontal plane; that is, the ability to turn quickly in a small radius. This allows the A-10 to fly very low, using terrain for cover, and to quickly bring its ordnance to bear on small, elusive mobile targets like tanks and troop positions. It also affords the Warthog pilot time to visually confirm friendly from hostile forces, which may be separated only by a few hundred yards.
To say that the forward edge of the battle area (FEBA) is a dangerous place is quite an egregious understatement, given the proliferation of light automatic anti-aircraft weapons, shoulder-fired surface to air missiles (SAMs) and larger, radar-controlled mobile SAM launchers. For any CAS aircraft, the danger is compounded first by the need to loiter over the battlefield (increasing exposure time); and second, by the high pilot workload (monitoring air-to-air and air-to-ground radio channels, trying to acquire the target, keeping track of friendly forces), which makes it difficult to see and evade many threats. For this reason, many air forces, including those of Germany, Israel and Russia, have relegated fixed-wing aircraft to a secondary role in CAS, placing their principal reliance on attack helicopters. The fixed-wing A-10 is something of an oddity, but it succeeds quite capably since its design stressed survivability through the protection of critical and redundant systems (widely separated hydraulic lines, a manual backup control system, widely separated engines to avoid total power loss from a single hit). Its effectiveness is due to it being a single mission, optimized platform. Even so, the A-10 can still be shot down, and special tactics have been developed to exploit its unique performance and design features and thereby improve its chances of survival.
Operational Threat Arena
Before one can understand the tactical repertoire of the A-10, one must understand the nature of the air defense threats that it faces in the performance of its primary mission. At the time of its design, the threat was defined as the air defenses of the Soviet Army on the NATO Central Front in Germany. Having suffered severely from German airpower in World War II, and recognizing that its own air forces were technically inferior to those of the NATO allies, the Soviet Army developed comprehensive and highly effective mobile air defense systems intended to protect its mobile forces from just the sort of threat posed by the A-10. The Soviet Union has been relegated to the ash heap of history, but the Russian Army remains, and its air defense systems remain the standard by which others are judged. In addition, many former Soviet client states and Third World countries are equipped with Soviet air defense weapons, and have air defense systems based on the Soviet model.
Soviet forward area air defenses are based on a layered concept of defense in depth, with multiple weapons of various types providing protection at different organizational levels. To begin within the tank and motor-rifle (mechanized infantry) battalions of the maneuver divisions, each tank, and most other armored vehicles, mount a heavy machinegun of 12.7 or 14.5mm bore. Visually aimed, each gunner has only a small chance of hitting an aircraft, but with 30-40 such weapons in the battalion, a wall of fire can be thrown into the path of an aircraft that is very hard to avoid. At the very least, these weapons exercise a deterrent effect on attacking pilots (forcing them to jink during their approach runs, thereby reducing bombing and strafing accuracy); at worst, a random hit (the notorious "Golden BB" can hit a critical component, bringing down a mult-million dollar fighter. The A-10's design largely negates this threat, allowing the pilot to concentrate on attacking with greater confidence of a successful mission profile through enemy air defenses.
Man-Portable Air Defense Weapons
Complementing the anti-aircraft machineguns are shoulder-fired SAM launchers, one of which is found in every motor rifle platoon (3-4 armored personnel carriers with 30-40 men). The oldest of these, the SA-7 Grail, is broadly similar to the U.S. FIM-47 Redeye. Armed with a 2kg high explosive warhead, it has a simple, uncooled infrared seeker that can only lock onto aircraft from the rear (i.e., hot engine nozzles), which in practice makes it a "revenge" weapon that can only be used on aircraft that have already made their attack. It has a range of 4-6 km, and a maximum ceiling of 2,500 meters. Now obsolete, it is still used in large numbers by Third World forces and terrorists.
The Grail has been superseded by the SA-14 Gremlin and the SA-16 Igla, both roughly comparable to the U.S. FIM-92 Stinger. Both have a range of 6 km, and a ceiling of 3 km. In contrast to the SA-7, they have much more sensitive IR seekers that can lock onto an aircraft from any aspect, including head-on, which makes them much more effective in disrupting an air attack. The SA-16 has a wide-angle seeker that allows it to track aircraft turning sharply.
All infrared missiles home on the heat generated by the target. The most common countermeasure against them are decoy flares, of which the A-10 can carry up to 480 in ALE-40 dispensers built into the wingtips and landing gear nacelles. The crude seeker of early missiles like the Grail simply homed on the hotest heat source in its field of view (sometimes including the sun or a hot chimney), so flares were very effective. Later missiles, like the SA-14 and 16, use seekers that operate in two frequency bands ("colors") in order to reject flares and other heat sources that do not closely resemble actual aircraft IR emissions. In response, flares have been developed that more closely match true IR signatures. Yet even these can be defeated. The latest models of Stinger, for instance, use the ultraviolet contrast between the target and the background sky to reject spurious emissions from flares. Nonetheless, individual shoulder-fired SAMs are not a serious threat; they can be spoofed, evaded or outrun, and a single hit from the small warhead may not cause fatal damage. Their true effectiveness lies in their ubiquity: passing over an enemy unit, a single aircraft may be attacked by upwards of a dozen missiles simultaneously, making a hit almost unavoidable.
SPAAGS
To the immediate rear of the front-line units one can find radar-directed self-propelled anti-aircraft guns (SPAAGs), six of which are commonly organic to each regiment or brigade. In the 1970s and '80s, the standard Soviet SPAAG was the ZSU-23-4 Shilka, many of which can still be found in Eastern Europe and the Third World. This formidable vehicle, with a tracked chassis and turret armed with four water-cooled 23mm cannon, was responsible for the majority of Israeli aircraft losses in the 1973 Yom Kippur War. Each gun has a cyclic rate of fire of 800-1,000 rounds per minute, for a combined rate of 1,600-2,000 rounds per minute. In operation, the guns are fired in bursts of 30 or 100 rounds. The guns are directed by a "Gun Dish" tracking radar, which passes range and range rate data to a fire control computer that accounts for lead and bullet drop in laying the gun. Typically, a radar directed burst has a 33% chance of hitting at a maximum range of 2,500 meters. The Gun Dish radar can be jammed, in which case an optical sight can be used with a corresponding reduction in accuracy.
Electronic countermeasures are one way to defeat the Shilka. Two others are to fly very low, using terrain masking to avoid detection by the Gun Dish; or to fly at heights abouve 6,500 feet, above the effective ceiling of the gun. To fly very low, an aircraft must either fly slowly (like the A-10) or have a terrain-following radar (like the F-111). In either case, it is extremely difficult to detect small targets like tanks unless one pops up to a reasonable height, which places the aircraft back in the vulnerable zone.
SHORAD
Aircraft attempting to fly over the Shilka's effective ceiling were normally engaged by a short-range air defense (SHORAD) missile system such as the SA-9 Gaskin or SA-13 Gopher. These are essentially enlarged versions of the SA-7 and SA-14, respectively, combined with infrared homing ranges of 9 km (SA-9) and 7 km (SA-13). Both have a ceiling of about 5,000 meters. The SA-9 is essentially a rear-quarter missile, but the SA-13 has a better seeker offering all-aspect capability. They have the same weaknesses as the shoulder-fired SAMs, but with greater range and larger warheads, they are significantly more lethal. Both the SA-9 and SA-13 are mounted on self-propelled chassis, wheeled in the case of the SA-9, tracked in the case of the SA-13. Target acquisition is visual in both, but the SA-13 has a range-only radar to assist the gunner.
In the Russian Army, both the SA-9/13 and the ZSU-23-4 are being replaced by a single combined gun/missile system, the 2S6 Tunguska, perhaps the most effective short-range air defense system in the world. Mounted on a large, tracked chassis, it combines on a single mount two 30mm water-cooled, high-velocity cannon and launchers for eight SA-19 Grisson short-range missiles. In addition, the 2S6 carries an integral target acquisition radar, a tracking radar, a laser rangefinder, and an electro-optical sight. In operation, the 2S6 would detect and engage targets first with the SA-19, a high-velocity missile with a range of 9 km. Relying on laser beam-riding guidance rather than IR, it is particularly difficult to defeat with countermeasures, and is too fast to evade easily. As a rule, two missiles are launched at each target. If the missiles miss, or if the target is detected inside of 4000 meters, it is engaged with the guns, the range and accuracy of which are significantly better than others of equivalent caliber. Not having been used in combat, the weaknesses of the 2S6 radar systems cannot be assessed, but later concurrently developed Soviet radars are very good indeed.
MSAMs
Overwatching the forward area air defenses are divisional air defenses based on short and medium range SAMs (MSAMs) such as the SA-6 Gainful and SA-8 Gecko. Both of these radar-directed missiles have been quite effective in combat, though their performance in the hands of Soviet clients like the Syrians and Iraqis might lead one to denegrate their capabilities. The SA-6 is an integral rocket ramjet missile with a maximum velocity of Mach 2.5, a maximum range of 24 km, and an effective ceiling of 11 km. A firing battery consists of four self-propelled triple launchers and a self-propelled "Straight Flush" engagement radar. The single radar represents the critical weakness of the system since only one target can be engaged at one time, and Israeli tactics in the Bekaa Valley in 1982 emphasized elimination of the radar in order to neutralize the battery.
The SA-8 Gecko's self-propelled launcher, in contrast, carries its own missile guidance radar, allowing a battery of four launchers to engage four targets simultaneously. Rather smaller than the SA-6, the SA-8 is a conventional solid-fuel rocket, with velocity of Mach 3, a range of 12 km, and a ceiling of 12.2 km.
Within the Russian Army, both SA-6 and SA- 8 have been replaced by the SA-15 Tor, a highly impressive weapon system featuring a self-propelled laucher with eight vertically launched missiles, an acquisition radar, a tracking radar, and a backup optical tracker. In contrast to earlier systems, each Tor launcher can engage two targets simultaneously. The SA-15 missile has a maximum velocity of Mach 3+, a range of 15 km, and a ceiling of 9 km. Used in conjunction with the 2S6, it gives the Russian Army the best short-range air defense in the world today. Both the SA-15 and 2S6 are being marketed quite actively by Russia in its quest for hard currency, so these weapons may pop up in many contingency theaters.
Overwatch
Behind all of the forward area systems, the Soviet and Russian Armies deploy MSAMs at the divisional and army levels. These included the SA-6, which has been superseded in that role by the SA-11 Gadfly. Mounted on a self-propelled launcher with four missiles and a guidance radar, the SA-11 has a maximum velocity of Mach 3, a maximum range of 30 km, and a ceiling of 15 km. It in turn is now being replaced by the SA-17 Grizzly, with even better performance. The divisional MSAMs overwatch the SHORAD and forward area systems, preventing the enemy from flying over or around them. Thus any attacker attempting to fly CAS against a Soviet-style air defense system would be confronted by a multiplicity of weapons, each with different and complementary characteristics, sited so as to provide mutual support and overlapping fields of fire. Small wonder, then, that the US places so much emphasis on "Suppression of Enemy Air Defenses" (SEAD) with specialized "Wild Weasel" aircraft to destroy SAM sites and radars, as well as on active and passive ECM. In this highly lethal environment, the A-10 must not only survive, but thrive.
