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Aviation History
1942
1942 - 1298.PDF
616 . FLIGHT JUNE I8TH- J942 NAVAL DEFENCE Are We on the Right Lines ? : Basic Principles Challenge "Height Charges" Advocated By C. WHEN anti-aircraft guns first came into being in the last war the need was urgent and the adaption of the field gun obvious. The short-barrelled gun of about 3m. calibre was capable of reaching the normal heights at which aircraft then operated, and the shell velocities of that period were considered to be sufficient for the comparatively low speeds of 1914-18 military air craft. These top speeds/by the way, were approximately the same as the present-day stalling speeds! The last war can be considered as the '' coming out period of the machine gun (although in 1914 an infantry battalion of 1,200 men did have just a quarter of the number of machine guns now mounted on a Mark I Spitfire or Hurricane), and it is not surprising that the rifle-calibre machine gun came to be considered as the defence weapon par excellence against low-flying aircraft. Watchmaker's Shells Hypnotised, as it were, by these original weapons, an attempt has been made to modify them, in order to keep up with increased aircraft performance, by improving their range, effective height, rate of fire, muzzle velocity and sighting. In this attempt the cannon and machine gun have each gone their own way and, in addition, met on common ground in the present-day shell-firing automatic cannons up to 40 mm. calibre. The classic example of this merging of the two types occurs, of course, in the famous multi-barrelled naval pom-pom, which squirts an incredible number of " watchmaker made " shells into the sky in an equally incredible short space of time. Do we shoot rocketing pheasants with needle-calibre tommy guns? If not, why try to stop a Jap pilot of a torpedo bomber—who is of the opinion that dying in battle is a good idea—with a stream of projectiles varying from .303m. to 40mm. None of these is able to quash immediately a really determined attack because the damage done is insufficient to stop a machine in the last stages of an attack which may be made at a speed of 400ft. per sec. What are the most feared forms of air attack at sea? There is mass or pattern'bombing in daylight by a forma tion of aircraft; dive-bombing or low horizontal bombing attacks; and, "finally, the air-launched torpedo which has served us so well and, in turn, punished us-so severely. Make Air Untenable How can all these forms of attack be rendered ineffec tive? It seems possible that the answer is to be found in the employment of "aerial height charges" in somewhat the same manner that we employ depth charges against submarines. What is visualised is a gun of maximum calibre (15, 18 01 even 2oin. if possible) for employment against high-flying aircraft and a short-barrelled cross-bred weapon, between a gun and a mortar, for use against dive- and torpedo-bombers. The extreme range in the latter case need not be more than 4,000 yards. The projectile in each case would have the thinnest walls possible, con sistent with safety, to accommodate a maximum amount of high explosive. Let us consider the effects of such weapons in action against these forms of attack. In daylight pattern-bombing by formations of bombers escorted by fighters we have the target most suited to the present A.A. system because a formation cannot jink in the same manner as can a single DUCKHAM machine. Nevertheless, instead of shooting salvo after salvo of 3.7m. or ^in. shells into the air, why not plant 500 lb. of explosive in their midst? The formation must be fairly close to make the bombing effective, and the least result must be a loss of formation jus': at the moment when the attack is imminent. Good snooting should bag more than one machine at a time. The essential of .defence against any low-flying attack, which includes shooting-up with cannon-armed aircraft, horizontal bombing, dive-bombing, and torpedo-dropping," is that ttper-aim of the attacker must be instantly destroyed. Whether the aircraft itself is destroyed as well is a secondary consideration since its purpose has been frus trated. There must have been hundreds of cases in this war in which an attacking pilot has been mortally wounded and /or his machine damaged, and yet they have carried on those last few necessary yards to make the attack which may cripple a battleship. Any low-flying aircraft attacked by an aerial height charge is in exactly the same predicament as a bomber which has come down too low to drop instantaneous fuse bombs and blows itsjrtf'up in consequence. This actually occurred several times, in the earlier stages of the war. In other words, if the aim of the defence is bad, all . thaf happens is that the violent shock waves from the explosion of the height charge puts the attacking machine off its aim. Shock Wave Effect Even very bad shooting should bring the target within an area where the intensity of the shock wave is in the region of 10 lb. per sq. in. In the case of a Junkers Ju 88 this means a load of nearly three-quarters of a million pounds-over its wing area of 515 sq. ft. If the shootingA$ good and the height charge explodes slightly above the dive-bomber or torpedo-dropper, then the enemy will either disintegrate completely or will most certainly hit the water before any. semblance of control can be recovered. The great point is, however, that the attacking pilot—be he super-fanatic Jap or super-heroic Hun—will at the very least be put off his target and must make another attempt; and super-heroics; or super-fanarticism are seldom so super during second runs. Remember, a battle-mad man will still come on with half a dozen 0.303 bullets in J*rm, but a.mortar bomb stops him instantly. It takes a lot of shell splinters or bullet= — to stop an aircraft from flying on for a last 1,000 yards, which in time means roughly seven seconds. The '' aerial height charge'' has been dealt with here entirely from a naval defence point of view, but in certain circumstances it could be used on land. In sparsely in habited areas it could be employed against the night bomber. This, however, is a terrific problem because, despite modern aids to gun-laying, many seconds must elapse from the time a gun fires until the shell explodes. During this period the machine can slow down, accelerate, climb, dive, skid sideways or perform a combination of any of these. The "aerial height charge" visualised will score in that it will have the effect of putting any machine within 300 yards out of the pilot's control. To recover physically from the shock of the explosion and then regain control of an aircraft which is by that time probably doing 500 m.p.h. in a nose dive at night—if it has not already disintegrated—will, to say the least, make a pilot watch his step when approaching a known defended area again. v
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