METHODS OF DEFENCE AGAINST AIRCRAFT

Hawke's Bay Herald-Tribune, Issue 166, 31 July 1937, Page 15

METHODS OF DEFENCE AGAINST AIRCRAFT

Germany Has Guns Which Can Drive a Shell to a Height of 40,000 Feet But Her Searchlights Are Unwieldy When Compared W ith Those of Britain

^TATEMENTS have been made that our defence against invading aircraft is deficient bqeause ground troops are controlled by the Army and air fighters by the Boyal Air Force, says a writer in the London Observer. Further, the guns are administered by the Boyal Artillery, the searchlights by the Boyal Engineers, the Observer Corps is civilian and proteetive measures against gas and fire are looked after by the Home Office. Critics of our methods point to the German anti-aircraft defence, which is completely in the hands of one department, and neglect to give any credit for the very complete system of correlation which has been worked out for the defence of London and other important centres. Whether the defence is in the hands of one or two, or even three or four, separate services does not matter provided that in'action they are under one command. Unity oi' command provided for in our defence scheme.

German ideas differ to some extent from our own, but whether these ideas are better than outs only actual test can de'termine. The German military, authorities have allowed something to be known of the defences of Berlin, but little or nothing about their proteetive measure for other parts of Germany. We, with the neeessity for getting recruits for a volnntary service, have advertised our own methods fairly completely. The Germans believe in the nso of two different types of gun for fighting aircraft from the ground. THey have a very quick-firing weapon of ubout Hin. bore for tackling low-flymg aircraft, and an effieient high-altitude weapon of approximately 3Jin. bore, which is said to be capable of driving a shell to a height of 40,000 ft. Tliey have also been experimonting with a roeket type of projeetile, but of thi3 very littie is known. The present British gun has only an altitude range of about 19,000ft., but the new guns will have a range of atleast 30,000ft. -

"There is also in pteparation a rapid-fire gun, firing a shell of abont 2 lbs., but no official information is available as to whether it is to be used in the organised defence o£ London and other cities. It will certainly be used in the field against low-flying aircraft. The German searchlights have always been good, and there is little to choose between theirs and ours. They are believed to be experimenting with an extremely effieient type of mercury arc, but they have no moncpoly of these lamps, for British, as well as America- and Dutch, companies are already producing them, at any rate in the laboratory. The advantage of this type of lamp is that it requires nO carbons and no adjustment of the light. Onee the light is switched on it remains eonstant and does not flutter. In theory the German predictor is a better mstrument tban ours. The predictor is a complicated calculating instrument, which solves the problem of the direetion in which the gun 'is to be pointed and the height at which the shell is to burst. It allows for the speed of the aircraft, the direetion of its travel, whether it is

climbing or descending, and the amount of its drift. The name predictor indicates that its work is so to aim the gun that the bursting shell and the aircraft will meet on ' their respective eourses. It is, in ,-fact, an electrical and mechanical means of doing what the game shot djps instinctively when he swings on to, and in f ront of, a flying bird. The British predictor is worked by six men. The German instrument, which also allows for swooping or curved flight, requires ten men to work it. It is also a considerably bigger piece of apparatus. British authority is of opinion that the additional complieations necessary to allow for curved flight are not worth while, in that every man added to the predictor crew multiplies the chances of mistakes. A good deal has been heard lately of the balloon apron, or "barrage," for anti-aircraft defence. We have been told that both the German and French balloon aprons are' set mueh higher in the air than ours. Since our defence

spokesmen have wisely declined to give any actual figures in eonneetion with our balloon aprons, copying the reticenee in this matter of other countries, no comparison can be made. The Germans are said to have some taobile aprons, bnt their efficiency is . doubted, as a kite balloon cannot be towed very fast when it is inflated, and if it is taken from place to place deflated the fllling of the gas bag will occupy a considerable time. Multiple tuhe fllling cuts down the time considerably, but hydrogen tubes are weighty things to cart about. ' Critics who compare the air dot'ences of one country with those of another usually fail to take into consideration the fact that arrangements which are ' quite suitable for one type of country might be quite unsuitable for another. The British defenco scheme has been worked out for ou» own country. Our military o authorities are satisfied that it will be effieient when w6 have the men and the material to make it complete.-