Could They Hit Air Force One?

By Philip Elmer-DeWitt

A heat-seeking surface-to-air missile hurtles skyward faster than the speed of sound. In a matter of seconds, it can zero in on a plane, blasting it from the sky in a sickening burst of flame and smoke. Moreover, such missiles are all too available to terrorist groups and criminals around the world. Last week intelligence reports indicated that the Colombian cocaine cartels may be stockpiling just such antiaircraft devices. The fear is that the drug lords could use them to mount an attack on President George Bush when he flies into the Colombian city of Cartagena for a four-nation antidrug summit starting Feb. 15.

Could the President's plane be shot down? Military experts say the chances of a guerrilla group mounting a successful air attack on Air Force One are extremely small. Although the exact nature of the plane's defenses is top secret, they are known to be formidable. Not only can the President's Boeing 707 be protected by a full complement of military fighter jets but the plane is also loaded with sophisticated electronic safeguards.

The heart of the defense rests in a collection of computerized equipment mounted in the 707's cockpit. There, at a console packed with indicator lights and video monitors, a specially trained electronics war officer can monitor the airspace around Air Force One. Should danger be indicated, he can unleash several electronic countermeasures, including radar jammers, fine-tuned infrared flares and billowing clouds of metallic chaff.

The most serious threat comes from surface-to-air missiles (SAMs) launched either just before the President's plane lands or just after it takes off. Although the Colombian drug cartels have apparently never used such weapons before -- and there is still no hard evidence that they have acquired them -- there are certainly plenty of SAMs, primarily U.S.-made Stingers and Soviet-built SA-7 Grails, available through illegal channels. Both are portable, shoulder-mounted rockets that use tiny infrared sensors to home in on the heat generated by a jet engine.

The standard defense against a heat-seeking missile is to divert it with another heat source, typically a flare that emits a broad range of infrared radiation. The missile, drawn by the heat of the flare, follows it and not the plane. But modern SAMs are equipped with filters that can cancel out radiation from a simple flare. Air Force One is believed to carry flares that burn brighter and longer in the infrared frequencies that the SAMs' sensors follow.

But not all missiles are heat seekers. Air Force One must also be protected against radar-directed air-to-air missiles, like the French-built R-530s that Colombian air force jets are known to carry. These rockets spot their prey with radar beams and follow the echoes toward the target. One way to divert a missile flying along a radar beam is to fire off a burst of metallic chaff particles. They cause the missile's radar guidance system to go haywire amid a blizzard of electronic gibberish.

A more artful way to avoid an incoming missile is to deceive it with false or misleading radar signals. Air Force One is equipped with a variety of sophisticated jamming equipment designed to do just that. One widely used technique: delaying the echoes of incoming radar pulses, thus fooling the attacker into calculating that its target is farther away than it really is. Alternatively, the target plane may generate dozens of false radar echoes, each aimed slightly differently, creating the impression of a whole squadron of planes arrayed at various intervals across the sky.

Clever as these tricks may be, the equipment in Air Force One is primitive compared with what is being installed in the jumbo jet scheduled to start transporting the President in October. That $325 million "flying Taj Mahal," a specially modified Boeing 747, bristles with so much computerized hardware that it needs 57 antennas and 238 miles of wire to support its electronics. Says an official involved in its construction: "We put every last piece of modern gimmickry in that plane."

Determined to protect its Commander in Chief from all threats, the Air Force included features that would enable his plane to survive an atomic attack, as long as a bomb did not explode too close by. Rather than use silicon computer chips and copper wire, which can melt down in the electromagnetic pulse that follows a nuclear blast, the designers are loading up the new 747 with pulse-resistant fiber-optic cable and gallium arsenide chips. Barring a direct hit from an H-bomb, the new plane should enable the President to fly anywhere in unprecedented safety and comfort.

CHART: NOT AVAILABLE

CREDIT: TIME Diagram by Joe Lertola

CAPTION: MISGUIDING THE MISSILES

With reporting by Bruce van Voorst/Washington