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air defence

air defence
Raul Colon
PO Box 29754
Rio Piedras, Puerto Rico 00929

In the last two decades, only a handful of combat aircraft have been downed by anti aircraft systems. This has more to do with the fact that the majority of the high intensity conflicts 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 advanced 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 defence system instead of the multi layer umbrella it used to have since World War II. Today’s Army uses the short range, shoulder firing Stinger missile as its only short area air defence platform. For longer range, the Army employs an upgraded version of the Patriot system. The fact that the US Army only employs these 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 gloomy 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 prey to ground based gun fire. They believed that due to the fragility of those early aircraft, they would be shattered by a powerful, ground delivery shell or shells. But to the amazement of many commanders and visionaries, those gloomy 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 percentage of enemy aircraft with AAS fire.  At the centre 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 successes remained remarkably constant at 12,000 shells per 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 between Israel and its Arab neighbours 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 great as originally believed. Firstly, the fifty missiles used to down an aircraft was the same cost as 12,000 of the dreaded 88mm shells used 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 had developed the tactic of engaging AAS instead of going around them.

Although the ratio may not show it, AAS has proved to be a real defensive deterrent, but not the all stopping platform early visionaries thought it will be. As it is currently employed, a sophisticated AAS is developed with the idea of attrition. To make aircraft packages suffer as many losses as possible in order to deter further incursions. It is also designed to manoeuvre the aircrafts’ path towards a designated “target’ area where a concentrated fire could be mustered on only one sector. A by-product to these two factors is the profile of the aircraft approach that the AAS forces it 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 shot down by small calibre, 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 statistic that remained very similar in both conflicts was the shell-to-down aircraft ratio. Almost 10,000 machine gun shells were needed to shoot down 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 cannot be altered to counter AAS’ small calibre fire. They run low to the ground to avoid such systems, thus making them perfect targets for small fire. Unlike the fix wing aircraft, their main threat does not come from heavy machine gun fire, but from RPGs (rocket propelled grenades). For RPGs to work, they need the helicopter to be very close (one hundred metres 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 change 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 defence units utilize, there are four procedures that will always be employed. It’s a four step defence drill aimed to shoot down an incoming aircraft. The first step is to detect the air platform. Any aircraft, no matter how big they are, is just a “blip” in the vastness of the sky. It is also because of this vastness that AAS’s radars cannot cover the entire skyline forcing AAS’s managers to select entry points. These “points” represent the expected incursion areas an incoming aircraft might 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 arms ground fire occurs. The third measure an aircraft can employ to avoid detection is stealth. A technology currently use by the United States in 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 poised to break into the US stealth monopoly mainly with unmanned platforms. To counter the low flying tactic, in the early 1960s the US developed the concept of the Airborne Warning and Control System (AWACS). AWACSs platforms not only can be forward-looking posts, 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 needs to have it within range of its surface to air (SAM) batteries. Detection and acquisition of target have a longer range spectrum than that of the aircraft’s weapon package. This is significant because the AAS is designed to engage and destroy any aircraft as far from its territory or defence area as possible. Most conventional ground radars 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 percentage improves as the aircraft move forward the radar covering zone.

For example, at 375Km, the probability ratio jumps to 90%, a high percentage, but one 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 begin to implement their countermeasures (EC or low flying patterns). An advanced 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 bear. 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 are the long range SAMs. Afterwards, 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 favour the aircraft. Modern flying machines are built with very advanced defensive systems that it makes it difficult to shoot down even by a direct hit.   

Air defence systems are built around various sub-systems such as missile, small calibre projectiles and even nuclear weapons. The size and complexity of the missile system varies depending upon the warhead. The smaller missiles, primarily the low altitude, short distance portable systems utilize 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 most of the time can only be fired from behind the aircraft’s tail. Frequently, portable operators have only a few seconds (10-12) to fire the missile before the aircraft is out of the weapon’s range. This kind of missile operates at an altitude no greater than 1,000 meters. Because of 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 shoot it down. Meanwhile, Anti Aircraft Artillery (AAA) gun’s shell range between 20 and 57mm in size.

The gun shells need a direct hit to cause any type of damage. With a single hit, it probably will not be enough to bring down the plane. This is why gun shells are use in high quantities. Shells’ sizes also vary. A regular 20mm shell weighs in at around 3.5 ounces, 23mm weight 7 ounces, 40mm weight 30 ounces and a much powerful 100 ounces. The guns are usually aligned in a multi-barrelled configuration. Two prime examples of these platforms are the well regarded 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 consists of two 35mm guns delivering a rate of 18 shells per minute. These weapons and others like them are used primarily against helicopters and slow moving, fixed wing aircraft. But upgrades in helicopter armour has made the use of the lower calibre 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 used 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 calibre weapons are the Russians along with many of their client states. The AAS also employs a large number of small calibre 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 boost morale at the dreaded Western Front. The “fight back” idea behind the small calibre attack still permeates battlefields today. Although it is extremely rare to bring down an aircraft utilizing such mechanism, most of the times pilots are unaware of small calibre action, it still can inflict some damage to the airframe.

The other spectrum of the weapons employed by an advanced AAS is the large warhead area. Larger missiles are often more elaborate in design and weigh more 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 types of warheads can be a deadly weapon if it makes it to within a 100m radius of the aircraft. These warheads also carry the much used proximity fuse which detonates near, not directly, the aircraft. Heavy or large warheads are also use to shoot 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 platforms. The same reverse concept was utilized by the Germans during WW II. On that occasion, the Nazis employed their excellent 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 its hey day in 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 developed 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 shoulder fired 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, rely on an integrated system of short-medium and long range missile batteries augmented by the ultimate air defence 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 defence systems. These encounters have demonstrated to some extent 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 difference that speaks volumes of the technological development of each side. In the 1970s Israel-Arab wars, Israeli Hawk SAM batteries required 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 have 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 converging 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 reducing the effectiveness of the AAS’ radar arrays. Finally, the Soviet/Russian AAS developed systems are designed with a more “fixed” operational profile than mobile providing the incursion aircraft with a window to operate in. In the late 1980s the USSR constructed the most advanced AAS network outside the one operated by its satellite 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 defences proved worthless against the incursions of South Africa’s more westernised 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 defence 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                           4800m                                   5Km

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                           2000m                                   2Km

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                               Russian                 16                           6000                                       6

SA-11 Self Propelled System                             Russian                  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 Defences or SEAD is one of the most sophisticated missions any aircraft can undertake. But, as important as SEAD is, the mission is not undertaken 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 extent, are either upgrading existing platforms or are developing new 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 shoot down incoming aircraft, but to intercept ballistic missiles. A trend that should continue to develop as the situation in the air changes from the current, aircraft-based profile.  

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