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Aviation History
1934
1934 - 0639.PDF
FLIGHT, JUNE 28, 1934 Hot is provided with' a " loading handle," which enablesKim to reload without having to pull the belt through the feed block. The -rate of fire is from 750 to 1,000rounds per minute, A 0.5-in. automatic gun firing a bullet weighing 565 grains is manufactured by Vickers Arm-strongs, but is not a standard Service gun. With the increasing speed of military machines, arrange-ments are being made to collect the empty cartridge cases and links when they are ejected from the guns, as whenthey are carried away in the slipstream they are likely to cause damage to the aircraft. Standard single-seater and two-seater fighters used inthe R.A.F. to-day carry two fixed Vickers guns, while all other types using the fixed gun have but one. These gunsare usually placed near the engine to reduce the chances of the lubricant freezing. Thus the breeches are accessible tothe pilot during an action, and the ammunition boxes are easily replenished through doors in the cowling. There hasbeen a tendency, of late, in several countries to fit " out- board " guns. The term " outboard gun " is taken tomean a gun which fires outside the periphery of the air- screw. This installation offers many advantages, for themaximum rate of fire of the guns is allowed, and the pilot's cockpit is cleared of the guns, belt boxes and reservoir forthe synchronising gear. In the majority of aircraft using outboard installations, the guns are mounted in the wings.The Gloster S.S.19 " Multi Gun " fighter, which appeared two or three years ago, carried two Vickers guns in thesides of the fuselage and four Lewis guns mounted in the wings. The lines of fire of the four wing guns convergedat a predetermined point in front of the machine, forming a very deadly " cone of fire." Fixed Gun Sights Two types of sight are used in the R.A.F. with fixedguns—the " ring and bead " and the Aldis. Fighting air- craft usually mount both on top of, the fuselage, in frontof the pilot's windscreen. The ring sight consists of a metal ring with a smaller ring inside, supported by radialwires. A bright red bead is so mounted that the ring and bead harmonise with the axis of the guns at a predeter-mined range, usually about 200 yards in front of the machine. The Aldis sight is a tube containing a series oflens possessing neither magnifying nor diminishing proper- ties. A target, when viewed through the sight, has quitean ordinary appearance. So long as two circles, which are within the ring, are visible, the position of the pilot's eyeis immaterial. If he moves his eye slightly, the target appears to move with it. Tracer ammunition is notintended to take the place of sights but to supplement them. One recently-developed experimental sight consists of anelectrically-illuminated graticule reflected on to a mirror in front ofthe pilot's windscreen. The lumi- nosity may be regulated for vary-ing visibility and different kinds of background. " Camera " guns are used toinstruct pilots in the art of using a fixed gun. These are usuallymounted on a wing of the machine, and " shoot " photo-graphs' instead of bullets. "Free" Guns " Free " guns, like fixed guns,were developed from a " land " type. The belts of belt-fed gunsare apt to cause obstruction to a gunner operating a movablemounting, so the Lewis drum-fed pattern was chosen during the waras the standard movable gun for use in the R.A.F., which positionit still holds. The large barrel casing carrying the cooling finswas deleted, as it was found that the air stream cooled the gunquite sufficiently. Drums holding 97 rounds are used with the Lewisgun, but smaller drums seem to be coming into fashion as the97-round type is large and heavy to handle at high speeds. TheLewis gun is a " gas-operated " type, and is automatically operated by two forces—the pressure of the gas generated by theexplosion and a "return" spring. A pistol grip and trigger are provided beneath the gun, and, instead of thestock used with the " land " gun, a spade grip is fitted. The rate of fire is about 700 rounds a minute. The mounting of free guns on aircraft proved such aproblem during the war that, in 1916, Gen. Trenchard had one experimental machine supplied to each squadronof the R.F.C. so that any ideas that occurred to personnel might be tried out in practice. A remarkably efficientmounting was developed by W/O. Scarfi, R.N.A.S., and was adopted as standard equipment. This mounting,in a modified form, is still extensively used. One impor- tant alteration made since the war was the fitting of awind-balancing device, which gives a turning movement equal and opposite to that given by the wind on the guns.Fatigue caused by the rarified air at high altitudes pro- hibits the use of a mounting requiring much strengthduring operation. Quite a crop of " high-speed " mountings has appeared during the past few years, the best knownexamples being the Fairey, Hawker, Avro and an improved type of Vickers-Armstrong. The Fairey pattern scoresover the old ring type from several points of view. It is possible to fire directly behind, vertically upwards anddownwards, above and below the tail plane, and over the top main plane. The old type caused a serious drop in the.performance of fast aircraft, but the Fairey mounting permits the use of an aerodynamically efficient cockpithooding, and the gun, when not in use, is stowed away in the fairing. Gunners' positions, in aircraft having speeds of overabout 180 m.p.h., demand special attention. In the stan- dard Hawker " Hart " day bomber the gun ring is carriedclose behind the pilot in more or less the usual manner, but in the " Demon," the fighter version of the " Hart,"the. gunner's cockpit has been cut away and the ring tilted forward, thus bringing the mounting well below thetop line of the fuselage and at an angle to the line of flight. An interesting development is the " parrot cage "on the Bristol 120. A Scarfi ring is fitted low in the fuselage. Attached to and revolving with it is a largetransparent cupola, a section of which has been omitted to allow the Lewis gun to be used. The Westland AircraftWorks have also evolved a very efficient system of cockpit protection, which was described in FLIGHT of June 14, 1934.The arming of multi-engined aircraft entails the careful placing of guns to procure the best possible fields of firefor defensive purposes. Our latest night bomber, the Handley Page " Heyford," is an excellent example ofefficient distribution of armament. Besides the usual cockpit in the nose and the position roughly midway alongthe fuselage, there is a retractable and rotatable turret (or A TYPICAL INSTALLATION of twin Vickers guns showing their synchronising gear, ammunition boxes, feed arrangements and sights. 639
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