AK-AK ACCURACY

Nelson Evening Mail, Volume LXXIII, 11 December 1940, Page 7

AK-AK ACCURACY

SCIENCE WITH THE GUNS “BRITISH ANTI-AIRCRAFT FIRE UNBELIEVABLY ACCURATE” A GERMAN PILOT'S TESTIMONY Behind the anti-aircraft guns, known as Ak-ak in tlie Army, is a combination of science and skill which has had a tremendous influence in keeping the German raiders off their targets and in adding Nazi bombers to the collections of scrap metal dotted over the British countryside. Describing an anti-aircraft battery in action at night, T. A. Raman, a wellknown Indian journalist, mentions the mechanical aids to accuracy operated by the crews During a night raid he saw a group of men round what looked lik“ an oversize camera. This was the delicate “predictor.” Some little distance away three men worked the sound-locator, a weird instrument with huge trumpet-like appendages. A pause, and then comes word from the control room: “Target from the south-west.” Other messages come from the sound locator and from elsewhere: ‘Height twenty thousand feet.” This is repeated by the man at the predictor. Height, speed and other data are fed int( the machine. “Fire,” says a man at the predictor. “FIRE” bellows the sergeant. A terrific flash lights the meadow and the battery is in action. A CALCULATING MACHINE The key instrument (says Mr Raman) is the predictor, a thing of marvellous sensibility, worked by experts by irreverently called “the sausage machine” or even “that there sausage thing.” A miracle of speed and accuracy, it takes the data it is given, of estimated speed, direction and height, allows for the wind and the weight of the shells and other ballistic factors and gives a series of positions for the plane. It works out. too, the seconds it would tak« the shell to reach the objective, a most important factor, because heavy anti-aircraft guns fire shells which explode either on contact or at a set time. The machine works with its own “eyes” in daytime or with the searchlights at night. Otherwise it gets its data from the sound locators. “In a pause between the rounds, the sound officer takes me to his machine. Thomas, ex-piano tuner from Lambeth wa.y, is the key man. Pie sits among the trumpets, with two colleagues at lower levels all ear-phoned and watching flickering light rays in instruments before them. Three men gently rotate the turntable as and how they are directed Talking is sotto voce and every move stealthy, for small local noises might ge* mixed up with the sound of faraway engines. Thomas and his men feel round space till they are ‘dead on,’ arm then flash the message to the predictor giving the bearings “We go down to the control room. There is an almost scholastic atmosphere here—that is, if you omit the unscholastic jokes and asides. A goodhumoured man with a pipe in his mouth sits with earphones in one corner. map of a battle ‘All the time he keeps jotting data on pieces of paper and passing them on to his companion, a jovial youth who sits with a large map of London before him. Over the map is a transparent -sheet, and on this he pictures in arrows the data he is receiving. “We see the arrows pointing at us from different directions. They move nearer and one takes a leap to within our gun range, and the word is passed up: ‘Target approaching.’ 'Some come quite close and glance away at the last second. Other suddenly turn tail and are mopped off the map “The commanding officer is busy with a graph of curves and with books of figures. He is copying some figures into another book and making some quick calculations. ’Working out a barrage,’ he explains and tries to tell me how exactly it is done.” Ant'-aircraft firing is not taking potluck in the stratosphere. With the most accurate calculation it is still a chancv business, and all the time efforts are made to reduce the margin of error. Each shot is timed and predetermined, based on an array of calculation. Every shell goes out with a good prospect of meeting its target. It is this excellent ground work, this quick reckoning of maximum probability that extracted from the German the unwilling praise that the “British anti-aircraft fire was unbelievably accurate.”