THE pilots of Sopwith Tabloids, French Nieuports and German Taubes opened the age of aerial combat by taking potshots at one another with rifles in the skies of World War I Europe. But the first military function of aircraft in that war was gathering intelligence. Tiny, unarmed biplanes scurried behind enemy lines to spy out troop dispositions and act as airborne forward artillery observers. Warfare has grown immensely more complex in the half-century since then, but gathering intelligence nonetheless remains one of the airplane's most significant and fascinating functions.
Present-day spy planes, with their elaborate electronic gadgetry, come in two main varieties. The more glamorous type is the fast, sleek jet that darts through another country's airspace to photograph anything of military interest, from missile installations to arms depots. Best known is the subsonic U2, which precipitated a major cold-war crisis when the Soviet Union shot down one piloted by Francis Gary Powers in 1960. Its replacement is the SR-71, the 2,000-m.p.h. Blackbird, which is probably the world's fastest airplane in sustained flight (TIME, April 11).
The less spectacular type of spy plane is the slower patrol aircraft that measures radar capabilities and eavesdrops obliquely on enemy radio communications from a distance. The plodding, prop-driven EC-121 shot down by North Korean MIGs last week is a military version of the Super Constellation airliner. The EC-121 is an ungainly bird, its basically graceful lines awkwardly broken by wartlike plastic radar domes above and below the fuselage. Four piston engines give it a cruising speed of only 300 m.p.h., but it has immense range. It can fly 6,500 miles, staying aloft for more than 20 hourswhich enables it to monitor communications longer and more intensively than could a speedier jet.
The EC-121's working altitude of 25,000 ft. gives its snooping gear a much wider reach than that of a surface ship like Pueblo. Because many of the signals to be monitored travel in straight lines rather than bending with the earth's curvature, an airborne collector sees a much more distant horizon and can keep signals within range far longer. One EC-121 radar can sweep a 40,000-sq.-mi. area. The plane carries six tons of electronic gear and a crew of 31, large enough to allow technicians and translators to spell each other frequently at tasks that demand intense concentration.
The two main sorts of data collected by aircraft of this type are "Comint," for communications intelligence, and "Elint," for electromagnetic intelligence. "Comint" primarily means verbal radio messages while "Elint" covers such nonverbal signals as radar, automatic landing aids and computer traffic. Since the early 1950s, EC-121s have flown the Atlantic and Pacific regularly as radar picket aircraft.
In Viet Nam and in North Korea, the planes have been used to eavesdrop on the enemy. They also plot the types and sites of radar installations and other electronic gear. They ply the Mediterranean, the Caribbean environs of Cuba and the entire East Asian coast from Viet Nam northward. -