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Aviation History
1979
1979 - 1542.PDF
1476 RIGHT International, 5 May 1979 ''»M**''""•••»•«-• kjtiisyi -«§• lorn.. AatatOt •V*tmr"TaM Weapons for the black-box war One of the charges levelled at 19th century and early 20th century arms salesmen was that they sold weaponry to one nation and the counterweapon to the likely opponent. A month after reporting on military airborne radars, DOUG RICHARDSON emulates these entrepreneurs by describing some of the techniques used to degrade and confuse radar defences allowing bombers and strike aircraft to avoid or blunt fighter and missile attack. To the airmen of Kampfgruppe 100 who flew their Heinkel bombers over south-east England in the late autumn of 1940, aspirin was a panacea for headaches. For the personnel of the RAF's 80 Wing on the ground below, Aspirin was the answer to the radio beam system in tended to guide the Luftwaffe to its targets. The first "black-box war" was under way. Aboard the Hell Is, aircrew used the Lorenx blind-landing receiver to listen for highly directional radio beams transmitted from Cleves in Germany. One was modulated with Morse-code dots, the other with dashes. If the aircraft flew exactly along the centreline between the two overlapping beams the two signals merged to produce a steady tone in- dictating that the bomber was on course for the target. At least that was the theory. Using transmitters capable of reproducing the dash signal, 80 Wing was able to confuse the listening aircrew by pre senting them with a signal which stub bornly refused to obey the rules. These jammers were codenamed Aspirin, while the entire anti-beam programme was aptly known as Head ache. Electronic warfare had won its first victory but was soon to teach its successful user a painful lesson. On the night of November 14/15, KGr 100's Heinkels spearheaded the attack on Coventry using a second and more complex radio-beam system. New jam mers codenamed Bromide were ready to confuse the new system, but they had no effect. Investigations after the raid showed that the equipment had been set to produce a 1,500Hz modu lating tone rather than the 2,0O0Hz used by the Luftwaffe. That 500Hz spelled the difference between suc cess and failure and underlined the golden rule of electronic warfare— almost right is not good enough. For the past 15 years, electronic warfare has been a major activity in the field of avionics. Combat air craft carry an amazing assortment of bumps and bulges containing the least-publicised equipment outside the fields of espionage and nuclear weaponry. To get some idea of the techniques which can be used to protect fighters and bombers from attack, the follow ing crude, if absurd, analogy will be useful. Imagine that half-way down a long, dark tunnel two soldiers have been stationed with orders to shoot anyone attempting to pass. One is a blind officer. His somewhat slow- witted companion is a simple soldier equipped with a pocket torch and gun. The soldier searches the tunnel with his torch in the direction from which the intruders are expected. If he catches sight of anyone, he asks the officer for permission to fire and when this is granted, he promptly shoots the intruder. The soldier is simply a weapon system capable of detecting, tracking and destroying a target but he is commanded and dependent on a higher authority—the blind officer. What countermeasures could be used by the intruder to improve his chances of survival in the face of this unlikely threat? The most obvious would be to dress in black and blacken his face so as to present a poor target to the searching light beam and thus cut down the time available for the sentries to act. But this is not really enough to ensure survival. A smoke bomb lobbed down the tunnel would do the trick much better by preventing the soldier from seeing his target. Alternatively, the intruder could carry a high-intensity fight source such as a photographic flash gun and use this to dazzle the soldier as he raises his gun to open fire. Several moments thought will sug gest more exotic tactics. If the local discotheque could be persuaded to turn the volume control up to maxi mum for a few minutes, the intruder could stroll past the sentries, since the not-very-bright soldier would be incapable of receiving the order to fire from his officer. By adding ECM equipment to early F-l 11 airframes, Grumman has produced what must be the ultimate in jamming aircraft
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