Why didn't the terrorists' missiles
hit the passenger plane
1 Dec 2002, reposted 19 April 2003
IThere is a significant difference between military aircraft and passenger planes. The latter are generally equipped with "bypass" engines, whereas military aircraft usually are not. At the inlet of a civilian aircraft engine, a large fan. Only the central portion of the airflow is directed toward the turbojet; the remainder forms a kind of cold air casing.
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The overall propulsion efficiency is increased.
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The engine is quieter because sound waves emitted by the turbojet nozzle are reflected by the cold air casing.
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The infrared radiation emitted by the nozzle is also reflected by this cold air layer, due to the difference in refractive index between the hot jet and the surrounding gas. In terms of infrared emission, the entire jet then behaves like an "optical fiber," concentrating the infrared emission—and likewise the sound emission—along the aircraft's flight axis, toward the rear.
CThis is why infrared-guided missiles, designed to home in on an aircraft's nozzle(s) and even explode directly inside them, have difficulty tracking the exhaust from a bypass engine unless they are fired from within the aircraft's wake.
SIf airlines wish to protect themselves against terrorist attacks, they will need to carefully control the terrain areas located along the runway axes. Stinger missiles can hit their targets at altitudes up to three thousand meters. As long as the civilian aircraft has not reached this altitude, it is not safe—especially since it climbs in a very steep attitude. Complicating matters further is the fact that aircraft often turn quite early after takeoff, exposing their rear section toward another portion of terrain.
In the long term, if this type of terrorism were to spread, given its "efficiency," it would be necessary to equip civilian aircraft with launchers similar to those used on military aircraft—fired laterally, to the right and left of the aircraft. These are "fireworks" designed to lure infrared-guided missiles.
19 April 2003
. A "Missile Defense Act" was introduced to the U.S. Congress in February 2002. This indicates that it would cost between seven and ten million dollars just to protect American aircraft. Currently, only aircraft carrying political leaders are equipped with systems capable of detecting approaching missiles and decoying them. One solution is to release thermal decoys, though this carries the risk of starting ground fires (military decoys burn for 5 seconds). Another solution: release decoys with shorter burn times at low altitude. It should be remembered that 95% of aircraft hit by ground-launched missiles were struck by MANPADS (Man-Portable Air Defense Systems)—lightweight, easily transportable, undetectable until fired.
The "SAM-7" has an uncooled infrared seeker operating in the near-infrared range (wavelength: 1 to 2 microns). More advanced are the SAM-14 "Gremlins," equipped with a more sensitive seeker. The American Stingers are newer and use an indium antimonide detector operating in the mid-infrared range (3 to 5 microns). These missiles can thus "see" not only the nozzle gases but also the hot parts of the airframe.
The scale of the threat: During the time when the CIA supported Afghanistan against the Soviets, it delivered 250 launchers with 1,000 to 1,200 missiles. It is unknown how many were actually used. In 1989, the U.S. Air Force reported 269 Soviet aircraft shot down out of 340 missiles fired, yielding an 80% success rate. It is estimated that between 300 and 600 such weapons remain in circulation. Occasionally, recovered missiles are used against various aircraft—some targeting Indian planes flying over Kashmir. Stingers have been fired by Chechen rebels and Tamil Tigers. Twenty-seven guerrilla movements possess portable missiles. Fifty thousand SAM-7s were produced. The weapon has been copied, among others, by the Chinese. Pakistani engineers developed their version, the Anza, and Egyptians their own, the Ayn as Saqr. The Russians produced more advanced versions: the SA-14, SA-16, and SA-18. The SA-14 is very easy to transport. The Unità possesses them, as does the Irish Republican Army. In 2001, Israeli forces discovered four examples in the hold of a ship intercepted off the coast, the "Santorini."
Portable missiles could hit targets at altitudes not exceeding 3,000 meters. But newer portable systems can down aircraft flying at six thousand meters. Protecting civilian aircraft would therefore require controlling a zone surrounding airports, covering a radius of 50 km...
The Third World War has already begun. A choice between Pax Americana and Pax Islamica.
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