Air Defense

In the last two decades, only a handful of combat aircraft have been downed by anti aircraft system. This has more to do with the fact that the majority of the high intensity conflict developed during that time mostly involved the use of aircraft designed in the United States. These aircraft were employing the latest in electronic and avionics packages as well as more advance electronic countermeasure systems. Add to this fact the new air tactics developed and you have a combination of circumstances that had enable Western aircraft to defeat and, in most cases, destroy enemy’s anti aircraft systems (AAS). Not since the early days of the Korean War (almost fifty years ago) had any US Army or Western-equipped ground force been attacked from the air. In fact, today the US Army maintains only a two level air defense system instead of the multi layer umbrella it use to have since World War II. Today’s Army used the short range, shoulder firing Stinger missile as its only short area air defense platform. For longer range, the Army employs an upgraded version of the Patriot system. The fact that the US Army only employs those two systems is a testament to the US Air Force ability to achieve and maintain air superiority over its enemies during the past six decades. It also a rebuff of the glomming predictions made after the Great War in 1918.

During the first three decades of air traffic military commanders thought that early air platforms such as the famous German, British or French mono and biplanes were easy prays to ground based gun fire. They believed that the fragility of those early aircraft would be shatter by a powerful, ground delivery shell or shells. But to the amazement of many commanders and visionaries, those glom scenarios never materialized over the Western or Easter front. Nevertheless, Luftwaffe leaders in Germany prior to the start of World War II still clung to the idea of shooting down a high percent of enemy aircraft with AAS fire. On the center of their assumptions was famous German 88mm anti aircraft gun shell. Engineers and commanders alike believed that it would take only fifty rounds of this impressive shell to down an incoming plane. Unfortunately for the Germans, the reality turned out to be very different. Between the summer of 1940 until the end of hostilities in May 1945, the German rate of AAS shoot down remain remarkable constant at 12,000 shells per one aircraft. Again, the prognostication of the demise of the aircraft proved to be greatly exaggerated. Notwithstanding the German experience, commanders of all nations again asserted the demise of the aircraft when the first anti aircraft missile batteries began to appear in the early 1950s. But again their confidence in those ground based system was misplaced. During the 1960s and 1970s and in the mist of highly involved conflicts such as the Vietnam War and the series of wars Israel and its Arab neighbors played out during those years the missile to downed aircraft ratio was about one per fifty launched missiles. Although the ratio appears to have decreased dramatically, close examination of the data shows that the improvement was not as sharp as originally seen. First, the fifty missiles use to down an aircraft had the same cost as 12,000 of the dreaded 88mm shells did in the early 1940s. Second and more importantly to the development of AAS is the fact that for the first time in history, incoming aircraft have develop the tactic of engaging AAS instead of going around them.

Although the ratio may not show it, AAS does have proved to be a real defensive deterrent, but not the all stopping platform early visionaries thought it will be. As it is currently employ a sophisticated AAS is develop with the idea of attrition. To make aircraft packages suffer as many losses as possible in order to deter further incursions. It is also design to maneuver the aircraft’s path towards a designated ‘target’ area where a concentrated fire could be muster on only one sector. A by product to these two factors is the profile the AAS force an aircraft to follow. In order to avoid heavy saturated AAS sectors, an incoming aircraft must follow a low altitude flight profile. Such a profile will expose the aircraft to a heavy concentration of small arms fire. It is in this, low level profile, that the majority of aircraft are shut down by small caliber, ground based fire. Case in point: North Vietnam. In that high intensity conflict, over eighty percent of all aircraft loss was due to low altitude gun fire. The ratio was somewhat smaller in the 1973 Israeli-Arab war. Almost fifty percent of Israeli jets lost were by heavy machine gun fire. One static that remained very similar in both conflicts was the shell-to-down aircraft ratio. Almost 10,000 machine gun shells were needed to shutdown a single airplane. A ratio closely similar to that achieved during Word War II. Fixed wing aircraft are not the only flying platform affected by low-level ground fire. Helicopters are probably the most exposed flying machine. Their profile: a low flying pattern can not be altered to counter AAS’ small caliber fire. They run low to the ground to avoid such system, thus making them perfect targets for small fire. Unlike the fix wing aircraft, their main threat does not come from heavy machine gun fire, it comes from RPGs (rocket propelled grenade). For RPGs to work, they need the helicopter to be real close (one hundred meters or closer) to have any opportunity to engage an incoming helicopter. Helicopter pilots know this. They know that the most likely areas for RPG attacks are city streets, canyons and river lines. Pilots also chance routinely their takeoff and landing patterns while operating from forward bases. They don’t use the same incursion pattern twice and when they fly in formations, they do it with a 500 meter+ gap between air platforms.

No matter which system the ground defense units utilized, there are four procedures that will always be employed. It’s a four step defense drill aimed to shutdown and incoming aircraft. The first step is to detect the air platform. Any aircraft, no matter how big they are, is just a “blimp” in the vastness of the sky. It is also because this vastness that AAS’s radars can not cover the entire skyline forcing AAS’s managers to select entry points. These “points” represent the expected incursion areas an incoming aircraft should take. Planners as well as pilots know this and they try to minimize the detection area by engaging AAS’s radars with advance electronic countermeasures (EC). If ECs did not suppress the enemy’s ability to read the aircraft, then the pilot will use the old age trick to “decking his airplane”. Most conventional radars arrays can not look below their profile scope altitude (usually between 100 and 300 meters from the ground) thus providing the aircraft with an invisible window. But this window is not without peril. It is in this low altitude area were the heavy concentration of small arm, ground fire occur. The third measure an aircraft can have to avoid detection is stealth. A technology currently use by the United States on its massive B-2 Stealth Bomber, the new F-22 Raptor air superiority fighter and to a lesser extent, on the broad based, F-35 Lighting II program. Others countries are now poise to break into the US stealth monopoly mainly with unmanned platforms. To counter the low flying tactic, in the early 1960s the US develop the concept of the Airborne Warning and Control System (AWACS). AWACSs platforms not only can be forward-looking post, but because they are airborne, they have look-down capabilities as well. Unfortunately, the sheer vastness of the earth comes into play here too. It is virtually impossible for any current radar system, ground based or airborne, to cover the complete spectrum of the sky.

If an incoming aircraft is detected, the next step is to acquire it. Before engaging any aircraft, AAS’s operators must make sure that the plane is either a friend or foe and then proceed to chart a flying course for it. The charting of the course is one of the most important aspects of the AAS procedures. In order to engage the aircraft, the AAS need to have it within range of its surface to air (SAM) batteries. Detection and acquisition of target have a longer range spectrum that that of the aircraft’s weapon package. This is significant because the AAS is design to engage and destroy any aircraft as far from its territory or defense area as possible. Most conventional ground radar can detect an aircraft up to 550Km away and at a top altitude of 30Km. On the edge of the 550 spectrum, the probability of making an accurate identification of the aircraft is between 45 to 55 percent. The percent improve as the aircraft move forward the radar covering zone. For example, at 375Km, the probability ratio jumps at 90%, high number, but ones that still leaves a substantial margin for error. This “probability window” between the top operational range of the radar and the 90% point is the area where pilots began to implement their countermeasures (EC or low flying patterns). An advance AAS can detect and acquire an aircraft within one minute of the incursion. If both areas are successfully taken, then the AAS shifts towards the tracking phase. Is essential for the AAS to track the inbound aircraft long enough until System’s batteries can be brought to beard. The tracking aspect of the AAS engagement begins while the aircraft is outside the System’s weapon platforms operational range. Once inside the weapons’ spectrum, the first platform to be employed is the long range SAMs. After, the guns aspect of the system is engaged. Because guns are shorter range weapons, their radars have to track the aircraft the longest. The last step of the AAS procedure is the destruction of the aircraft. Even if the AAS is successful in detecting, acquiring and tracking and incoming plane, this does not translate into a successful engagement. In fact, the majority of engagements favor the aircraft. Modern flying machines are built very advance defensive systems that it makes it difficult to shutdown even by a direct hit.

Air defense systems are built around various sub-systems such as missile, small caliber projectiles and even nuclear weapons. The size and complexity of the missile system varies depending of the warhead. The smaller missiles, primarily the low altitude, short distance portable systems utilized a small warhead (5-7 pounds). These missiles are very limited due to their lack of size and proximity fuse (a radar mechanism that allows the missile to explode near the target). The smaller missiles are heat seeking devices that in most of the times can only be fire from behind the aircraft’s tail. Frequently, portable operators had only a few seconds (10-12) to fire its missile before the aircraft is out of the weapon’s range. This kind of missiles operated at altitude no greater than 1,000 meters. Because the smallness of the warhead, the portable missiles have to hit the target almost in the middle of the fuselage or on one of its engines in order to be able to shot it down. Meanwhile, Anti Aircraft Artillery (AAA) gun’s shell ranged between 20 and 57mm in size. The gun shells need a direct hit to cause any type of damage. Even if a single hit the target, it probably will not be enough to bring down the plane. This is why guns shells are use in high quantities. Shells’ sizes also vary. A regular 20mm shell weight in at around 3.5 ounces, 23mm weight 7 ounces, 40mm weight 30 ounces and the much powerful 100 ounces. The guns are usually aligns in a multi-barrel configuration. Two prime examples of these platforms are the vaunted Russian ZSU-23 which mounts four 23mm guns and can fire up to 60 shells per second. The second battery is the Swiss-made GEPARD. The GEPARD consisted of two 35mm guns delivering a rate of 18 shells per minute. These weapons and other like them are use primarily against helicopters and slow moving, fixed aircraft. But upgrade in helicopter armor has made the use of the lower caliber guns almost obsolete. AAS also deploy some of the largest guns ever devised. The much discussed 75mm (and even larger systems) are a real threat to any airborne platform. These large shells usually have a proximity fuse and fragmentation warheads. 75mm and beyond shells are expensive to develop, thus they are not widely available. Also, as with the other shells, although not in the same ratio, 75mm shells need to be use in numbers to achieve the AAS objective. Gun engagement procedure has not changed much since the days of Word War II. A massive barrage of shells is thrown up in the area where the radar predicts an aircraft will be appearing. The main user of these high caliber weapons are the Russians along with many of their client states. The AAS also employs a large number of small caliber weapons. This use goes all the way back to the Great War when attacked ground troops would fire machine guns, rifles and even handguns in the air. This was not only done to down an aircraft but also to boots morale in the dreaded Western Front. The “fight back” idea behind the small caliber attack still permeates battlefields today. Although is extremely rear to bring down an aircraft utilizing such mechanism, most of the times pilots are unaware of small caliber action, it still can inflict some damages to the airframe.

The other spectrum of the weapons employed by an advance AAS is the large warhead area. Larger missiles are often more elaborated in its design and weight more heavily than its portable counterparts. Their warheads are designed to, not only hit the target with more accuracy, but in a case of a near miss, to inflict as heavy damage to the aircraft as possible. Some large warhead missiles utilized a shaped charge to direct a flight of high velocity metal fragments towards and aircraft. These type of warheads can be a deadly weapon is its makes it within a 100m radius of the aircraft. These warheads also carry the much use proximity fuse which detonates near, not directly, the aircraft. Heavy or large warheads are also use to shot at helicopters. In fact, the use of dedicated anti-tank weapons is being closely studied by military planners as a way of shooting slow moving, low flying air platform. The same reverse concept was utilized by the Germans during WW II. On that occasion, the Nazis employ their vaunted 88mm AAA in the tank busting role with great success.

The deployment of an integrated AAS is done accordingly to the System’s operational range and mobility profile. The shorter range weapon platforms always accompanied the combat formations while the lesser mobile systems are set up around 100Km behind the front in order to protect supply depots and other rear-area installations needed for the continuation of the war effort. The main key for an effective AAS alignment is the layer concept. The saturation with multiple depth areas at different altitudes is what it makes the AAS concept work more proficiently. Case in point: the USSR. During the hey days of the Cold War, Russian generals and commanders were well aware that in a case of war, they would most likely lose control over the skies, so they develop a multilayer integrated system to deter allied incursions. The first layer was saturated with ZSU-23 cannons with a 2Km firing range augmented by a variety of less accurate should fire missile systems. After the cannons, lay the once feared SA-9 (8Km range) missile batteries. The ground troops were covered by SA-7/14 and its 4Km practical range. Immediately after the front, the Soviet placed SA-8s (12Km range) and SA-10s (50Km) to protect the more sensitive areas supplying and maintaining their front line troops. Today’s pragmatic budget realities have made such multilayer systems almost obsolete in the East. Today, much of the former USSR’s supplied countries still use some kind of layering systems based on portable SAMs, small number of medium-to-long range missile batteries and a few cannons. Their Western counterparts on the other hand, relied on an integrated systems of short-medium and long range missile batteries augmented by the ultimate air defense weapon system: air superiority.

During the past five decades the only interaction between aircraft and AAS has pitted Western-developed air platforms against Soviet design air defense systems. These encounters has demonstrated to some extend the ineffectiveness of the Soviet designed systems. During the past fifty years, the hit, not the shutdown, ratio for a Soviet-made SAM was 50-1. Meanwhile, the Western’s SAMs ratio is almost 65% hit ratio. This is an amazing discrepancy figure that speaks volumes to the technological development of each side. In the 1970s Israel-Arab wars, Israeli Hawk SAM batteries require less than five shots for every hit on a Soviet-build, Arab operated combat jet. While the Arabs in the 1973 war fired 2,100 missile hitting 85 (4%) aircraft. Unfortunately 45 of the hit aircraft were Arabs. The US developed Stinger missiles has an even more impressive hit percentage (near 50%) in an impressive twenty plus year career. The incredible success ratio of Western aircraft against Soviet-developed AAS is the product of two convening forces. First and foremost, the Western aircraft are more advanced than the AAS they are facing. They also are usually fitted with the latest electronic countermeasure packages relegating the effectiveness of the AAS’ radar arrays. Finally, the Soviet/Russian AAS developed systems are designed with a more “fixed” operational profile than a mobile providing the incursion aircraft a window to operate. In the late 1980s the USSR constructed the most advance AAS network outside the one operated by its satellites states in Eastern Europe. Seventy six radar arrays, twenty four missile batteries locations and one hundred interceptor missiles were erected and deployed in the African country of Angola. Manned by East German technicians, the defenses proved worthless against the incursions of South Africa’s more westernize Air Force. The trend continued in both Gulf Wars (1991-2003) and the Afghanistan operation (2001) where the United State’s Air Force was able to suppress Russian developed AAS with amazing accuracy.

The chart below list the most utilized air defense systems. The Soviet/Russian developed weapon platforms are named after NATO’s codenames. The Effectiveness Ratio is a 1 to 100 scale that estimates the weapon’s combat accuracy and reliability. The Maximum Range is the top altitude a system can operate without loosing its overall capability.

WEAPON DESCRIPTION COUNTRY E. RATIO MAX ALTITUDE RANGE
Avenger Self Propelled System US 37 4800 m 5 km
Chaparral Self Propelled System US 18 1000 5
Hawk Mobile System US 45 11000 30
Advance Hawk System US 70 18000 40
M/42 Self Propelled System US 10 1500 3
Nike/Hercules Mobile System US 51 50000 150
Patriot Self Propelled System US 100 24000 60
Phalanx Naval-Based System US 47 2000 2
Sea Sparrow RIM-7h Naval System US 32 5000 5
SM2 ER Aegis Naval-Based System US 104 28000 180
SM2 MR Naval-Based System US 94 25000 150
Stinger Mobile System US 31 4800 5
Tartar RIM24b Naval-Based System US 33 20000 20
Vulcan Self Propelled System US 10 2000 m 2 km
Rapier Self Propelled System Great Britain 28 3000 7
Roland Self Propelled System Germany 39 3000 6
Regular .50 caliber gun mechanism Germany 5 1000 1
AMX 30SA Self Propelled System France 27 2000 4
Crotale Self Propelled System France 29 3550 9
SA-6 Self Propeller System Russia 36 2400 28
SA-9 Self Propelled System Russia 12 6100 8
SA-7 Fix/Portable System Russia 11 4500 6
SA-15 Self Propelled System Russia 21 6000 12
SA-8 Self Propelled System Russia 26 12000 15
SA-14 Fix/Portable System Russia 16 6000 6
SA-11 Self Propelled System Russia 48 14000 30
SA-18 Fix/Portable System Russia 25 3500 5
SA-17 Self Propelled System Russia 31 3500 32
SA-16 Fix/Portable System Russia 20 3500 5
SA-4 Mobile System Russia 32 20000 50
SA-13 Self Propelled System Russia 20 3500 5
SA-19 Self Propelled System Russia 24 8000 12
ADMG-630 Naval-Based System Russia 28 2000 2
SA-3Self Propelled System Russia 32 25000 25
SA-5 Self Propelled System Russia 65 30500 250
SA-10 Fix/Mobile System Russia 45 30000 45
SA-10(MU2) Self Propelled System Russia 94 24000 200
SA-12 Fix/Mobile System Russia 36 25000 100
SA-N3 Naval-Based System Russia 35 25000 30
SAN3 Upgraded Naval-Based System Russia 38 25000 55
SA-2 Fix/Mobile System Russia 23 24000 50
ZPU-4 Self Propelled System Russia 10 1400 1
ZSU-23 Self Propelled System Russia 19 2000 3
ZSU-57 Self Propelled System Russia 14 4000 6
Gepard Self Propelled System Switzerland 23 2000 4

Today’s air forces dedicate a great deal of training to the suppression of AASs. Suppression of Enemy Air Defenses or SEAD is one of the most sophisticated missions any aircraft can undertake. But, as important as SEAD is, the mission is not undertook without extensive research. Like air forces, AAS are encountering a greater threat from incoming cruise missiles such as the US Tomahawk. The US and Russia to a lesser extend, are either upgrading existing platforms or are developing new, purely designed Anti Ballistic Missile Systems (ABMS). One example of this latest development is the much publicized Patriot System. The Patriot first demonstrated its ability to, not only shutdown incoming aircraft, but to intercept ballistic missiles. A trend that should continue to develop as the situation on the air changes from the current, aircraft-based profile.

– Raul Colon

References:
Jane’s Aircraft Recognition Guide, Gunter Endres and Mike Gething, HaperCollins Publishing 2002
Skunk Works, Ben R. Rich and Leo Janos, Back-Bay Books 1994
US Strategic and Defensive Missile System 1950-2004, Mark A. Berhow, Osprey Publishing 2005
Russian Aviation and Air Power in the 20th Century, Robin Highanm (editor), Frank Cass 1998

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