AERIAL ATTACK

Evening Post, Issue 12, 14 July 1936, Page 10

AERIAL ATTACK

THE GUNNER'S ANSWER

ANTI-AIRCRAFT UNITS

NEW EQUIPMENT

A sardonic subaltern of the Royal Field Artillery once remarked to a iriend in the "Archies"—Anti-aircraft Artillery—"You know, old man, your job does seem a pretty chancy sort of one—rather like trying to knock out a nippy young blowfly with a peashooter." That little story goes back to the days of the war. Today a different one can be told of the science of anti-aircraft gunnery. Still, the task of the modern A.A. gunner is no sinecure. Since 1914-18 the weapons of the hunter have been revolutionised, and equal service has been done for his prey, the aeroplane. The menace of the air is being preached on all sides as the nightmare of future warfare, and anti-aircraft defence appears to be the answer to that burning' problem. As the improvement in technique continues the range, height, and speed o£ -aircraft become greater, with the result that more, distant objects come within bombing range and the weight of attack becomes correspondingly heavier. To meet this emergency manufacturers have concentrated on producing a highly-developed counter-weapon, and the result is the modern anti-aircraft gun:

With other countries, New Zealand has realised the danger of air attacks, and the Government has augmented the country's mobile defence with some of the /latest menaces to aircraft. They were imported early this year, some of. the equipment being stationed at Auckland and some at Fort Dorset, Wellington. The guns and their necessary units were recently assembled, and "in fighting trim they were paraded before a "Post" reporter and photographer a day or two ago. The officers concerned spared no time or effort to explain the working operations of the various units, and one can only pay a tribute to their knowledge and efficiency. Also, the men who man the units have responded to their training in a manner which does them great credit. GUNS DESCRIBED. The guns at Fort Dorset, which are mounted on four-wheeled trailers, from which they are fired, are three-inch, and they fire 161b high-explosive shells. The total weight of gun, mounting, and trailer is approximately eight tons, but as the trailer has giant pneumatic tires it can vbe drawn by the six-wheeled tractor-lorry at speeds r.p to 30 miles an hour. The lorry is not confined to ordinary hard-surfaced- roads, for it can travel over country which could not be traversed^ in a car. Huge chains can be fitted if necessary, and in the event of the lorry becoming bogged it can draw itself out by means of a winch operated by the engine. But for this device valuable time might be . lost in getting the machine on to a suitable running surface. The breech mechanisms on the guns are ■ semi-automatic, to enable a high rate of fire to be maintained. After p. round has been fired the gun recoils and runs out and the breech opens and ejects the empty case. Thrusting the next round into the breech causes the breech to close automatically, and the gun is again ready to fire. The guns j are fitted with telescopes and sighting 1 gear for direct laying on aircraft, and 3 they are exceptionally easy to traverse ' and elevate or depress. The sighting < gear, calling as it does for elaborate de- i flections and corrections, is complicated < but very sturdy, but while the task of \ any of one man is not undul" difficult ■ intelligent co-operation and a high degree of concentration are required of ; the detachment. Direct laying by the j gun-layers, however, is only a second- < ary means of laying. ' \ Since the war advances have been < made m the design of instruments for < computing the various deflections ne- i cessary to, allow for a fast moving tar- t get in space, and the new "magic" box c is known as the Vickers Predictor. .The predictor, which is part of the ( new-equipment at Fort Dorset, is un- i impressive at first glance to the eye, 1 though closer scrutiny dispels this idea.' It is a box-like structure with 1 nothing visible but a few eye-pieces, i Wheels, and dials. yet-it will predict c the position of the target aeroplane in £ space, and work out the correct "fuse- 1 length"—in other words it will auto- t matically fix the times at which the i shell should explode in order to burst i on or near its aerial target, together i with the angle to which the gun must c be raised to make this possible. This j instrument weighs aboUt 6001b and re- t quires six men to operate it. Two are s layers, who follow the target through i telescopes for direction and. elevation. ,The. rate of movement necessary to < follow the target varies with speed, t height, and direction, and the effect of i it is transmitted to the interior of the i instrument by the layers. The other i men. of the detachment, who watch 1 various pointers and dials, make ad- \ justments to the mechanism as mdi- i nated by the pointers and dials, and the final result is transmitted electrictfly to dials on the guns. With this method of laying, the gun-layers keep one pointer on a dial coincident with • the pointer operated^ by the predictor ■and m so doing lay the gun indirectly for elevation and direction. Two layers only need watch the target when this method is used. Summed up, the predictor automatically churns . out the constant deflections, both vertical and lateral, as made by the target \ m addition to the required fuse-length! , it is certainly a very complicated-look-mg instrument, and as an officer naively remarked: "It apparently does ] everything except play gramophone re- C cords and wash clothes." r A very necessary adjunct to the predictor is a height-finder, which actu- f ..ally ls a two-metre base range-finder * , with additional gearing for converting . range into height. All three—heightfinder predictor, and gun—can cope J with the heights and speeds at which it ; is expected a bombing machine would c fly. It is low-flying aircraft that cause r some concern, and for this form of at- f . tack anti-aircraft Lewis guns and spec- T ■ lal anti-aircraft multiple gun mount- s ings are available. ~ ' POWERFUL SEARCHLIGHT. t The heavy type of bombing aircraft depends for its safety on high flying * and night bombing, and to deal with I , this type of attack air defence organi- J , sations have what is known as anti-air- i craft searchlights. At Fort Dorset . there are several searchlights, and like the guns they are of the latest kind c Each searchlight unit consists of a six- i , ton lorry into which is built a genera- I tor for supplying power to the light c a projector with a 90mm mirror, and a a high-current-density arc lamp. The t station is carried complete in the lorry t with the men who operate the light A c special compartment is available for t the detachment. .When required the c searchlight is erected on the ground li and is connected to the lorry by 300 t yards of cable. The object in placing d the lorry 300 yards away from the light s is to take the engine noises away c from the sound locator. The sound p locator, which is part of the equipment 3 of the searchlight, has four "ears," or p trumpets, on long arms, connected byU tubes to stethoscopes. The listeners h fit on the stethoscopes and normally fliey; can locate with accuracy an air- a

craft four to six miles away and flying at a height of up to 30,000 feet.! Naturally the sound boxes will not; differentiate between aircraft noises and such outside disturbing factors as trams and car engines, with the result that' when a searchlight has to be erected in a populous area the work of the listeners is complicated by extraneous noise. The men on the sound locator direct the searchlight layer by, telephone on to the spot in the sky indicated by their instrument. The searchlight itself is easily handled and comparatively simple to operate. It produces a beam candle-power of over j 300,000,000, and it has a very narrow pencile beam which on a clear night! will illuminate an aeroplane at a height of 30,000 feet. ( Photographs of the new equipment | appear on the illustrations page today, i :