1936 - 3454
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DECEMBER 17, 1936. FLIGHT. 655 Showing the installation of a drum-fed machine gun and 20mm. canon in the Fren ch Loire 46 fighter. The A.A.C. 37 mm. aircraft gun is an automatic weapon available in two forms: the type M (movable) is a 20- calibre mod el, whereas the typ e F (fixed) is a 50-calibre type. Intended for use on large machines to protect them against the attacks of fighters, the former is mounted in a nose or fuselage turret with a plastacele protective dome, being capable of 360 degrees traverse, 15 degrees depres sion, and 60 degrees elevation. The gun is traversed by a wheel at the gunner's right hand, and elevation is effected by a second wheel on the opposite side. The gunner has a seat which rotates with the gun, and he is provided with a right-angle sight which remains fixed in relation to his eye in any position of the gun. The tra versing brake is worked by the gunner's right foot and th e firing trigger by his left. Clips containing five rounds of ammunition are used and the firing mechanism mav be set at safe, single shot or full automatic. It is impossible to fire the last shot of a clip until a new magazine is inserted or the gunner intentionally fires the remaining round ; thus the only break in the continuous fire of the weapon is the time required to change clips. A thermostatically controlled electric heater may be fitted around the hydraulic cylinder of the gun to main tain constant temperature, regardless of altitude or weather. It is claim ed th at the recoil force is less th an 1,000 lb., and th at the com plete installation weighs 250 lb. The muzzle velocity is 1,250 ft./min. (it should be remem bered tha t the gun is only 20 calibre in length) and the rate of fire 100 rou nds a minute. The possibilities of a gun with a higher muzzle velocity have been studied, but it was decided tha t, in view of the fact th at for some years aerial engagements are likely to be held at compara tively close range, the tremendous increase in weight and size was not worth while. The A.A.C. 50-calibre type F aircraft gun is simply an enlargement of the tvpe M weapon and is essentially an offensive weapon for mounting in the nose of a multi engined machine. Firing is done electrically by the pilot, while a second member of the crew changes magazines. The muzzle velocity is 2,700 ft./sec, and the rate of fire 90 rounds a minute. Five of the leading American aircraft manufacturers have made provision in the new aircraft types for the installation of A.A.C. guns, and in this country these weapons are being specified on Burnelli type aircraft built by the Scottish Aircraft and Engineering Co. The manufacturers maintain that no explosive shell smaller than 37 mm . bore and equipped with a thoroughly modern fuse, day and night tracer and delay-action arrangement can be made bore-safe and absolutely deto nator safe. It is impossible, they claim, for one of their shells, which are loaded with cast T.N.T., to explode pre maturely while in the gun. Arrangements have been made so that the explosive charge is detonated after the tracer has completed its burning. However perfect an aircraft gun, be it a canon or a machine gun, it is useless without an efficient mounting, and today the design of a mounting is probably as diffi cult as the design of the gun. Power-driven mountings will henceforth be essential on multi-seater machines, and in the design of such devices Great Britain is undoubtedly ahead of the rest of the world. A combination of powerful forces militate against the production of a completely efficient mounting. Apart from the difficulty of evolving an operating mechanism capable of functioning satisfactorily under all conditions of flight aerodynamics enter into the problem, for not only do protruding gun barrels complicate affairs, but the shape of the actual turret must be carefully considered. Re tractable, or highly streamlined gun positions seem bound to come into vogue ; even the retractable type must offer as little drag as possible when extended. The rear turret in the Fokker G.i, previously mentioned, and the fuselage gun positions on the four-engined Boeing bomber are excellent examples of the progress made. Unhappily it is not possible to discuss at any length the merits of new British and foreign gun mountings. It is significant that during public appearances the gun positions on a number of our new multi-engined machines are either dummies or are screened with fabric. Mounting ifficulties Among the major problems to be faced to-day are those connected with the cooling of internal installations and the deflection, due to the speed of the machine, of bullets fired broadside. The latter problem will become more serious as the speed of aircraft and the effective range of guns increase, and if higher velocity has to be obtained at the expense of lengthened barrels additional complica tions will doubtless result. There is little news of improvements in the design of small-bore machine guns. Outboard installations are likely to become common in this country, being facilitated, no doubt, by the use of the Browning gun. Modern canti lever wings are comparatively free from torsion and vibra tions, old troubles met in outboard installations. Present-day single-seaters lend themselves to a variety of arm am ent installations enabling different combinations of guns to be mounted for different requirements. For exanrole, Fokker offers the D.21 fighter with any of the following installations: one moteur canon (Hispano Ycrs with 20 mm. gun) and two or four machine guns (0.3 in.) in the wings; one machine gun of 0.5 in. calibre firing through the airscrew and two rifle-calibre guns in the wings; two synchronised 0.5 in. guns in the fuselage end two 0.3 in. machine guns in the wings; or two 20 mm. canons in the wings and two rifle-calibre machine guns in the fuselage. The French Dewoitine D.373 is supplied with four or six machine guns (the former armament is specified for this machine by the French Navy, and the latter by the Lithuanian Government); two 20 mm. cations and two machine guns; or one Hotchkiss high- velocity 25 mm. canon and two machine guns. The immediate future will doubtless see intensive develop ment work with canons and mountings for free guns. We can only hope that the weapons which will be required to equip our naissant military aeroplanes will be as highly developed as the machines.
Transcript of 1936 - 3454
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D E C E M B E R 1 7 , 1 9 3 6 . F L I G H T . 655
Showing the installation of a drum-fed machine gun and20mm. canon in the Fren ch Loire 46 fighter.
The A.A .C. 37 mm . a i r c ra f t gun i s an au to ma t ic w eaponavailable in two forms: the type M (movable) is a 20-calibre mod el, wh erea s th e typ e F (fixed) is a 50-calibret y p e .
Int end ed for use on large ma chines to pro tect themagainst the a t tacks of f ighters , the former is mounted in anose or fuselage turre t with a plastacele protective dome,being capable of 360 degrees traverse , 15 degrees depression, and 60 degrees e levatio n. Th e gun is travers ed b ya wheel a t th e gu nn er 's r ight han d, and e levation iseffected by a second wheel on th e oppo site s ide . Thegunner has a seat which rota tes with the gun, and he isprovided with a r ight-angle sight which remains f ixed inre la t ion to his eye in any pos it ion of th e gun. Th e traversing brake is work ed by the gun ner 's r ight foot and th efiring trigger by his left.
Clips conta ining f ive rounds of ammunition are used andthe f ir ing mechanism mav be se t a t sa fe , s ing leshot or full au to m at ic . I t is impossible to f ire the last
shot of a c l ip unti l a new maga zine is inser ted or thegunne r intentio nally f ires the rem aining rou nd ; thu s th eonly break in the continuous f ire of the weapon is thet ime requi red to change c l ips .
A ther mo sta t ica ll y controlled e lectric hea ter may bef i t ted around the hydraulic cylinder of the gun to mainta in cons tan t tem pera t ure , r ega rd less of a l t i tude or wea the r .
It is claim ed th at th e recoil force is less th an 1,000 lb.,and th at the com plete insta l la t i on weighs 250 lb. Themuzzle velocity is 1,250 f t . /min. ( i t should be remembered tha t the gun is only 20 calibre in length ) and therate of fire 100 rou nd s a m in ut e. Th e possib ilities of agun with a higher muzzle velocity have been studied, buti t was decided t ha t , in view of the fact th at for someyears aer ia l engagements are l ikely to be held a t compara
t ively c lose range, the tremendous increase in weight andsize was not worth while .
The A.A.C. 50-calibre type F a ircraf t gun is s imply anenlargement of the tvpe M weapon and is essentia l ly anoffensive weapon for mounting in the nose of a multiengined ma chin e . Fir in g is done e lectrica lly by the pilot ,while a second member of the crew changes magazines.The muzz le ve loc i ty i s 2 ,700 f t . / sec , and the r a te o f f i r e90 rounds a min ute .
F ive of the lead ing Am er ican a i r c ra f t man ufac ture r shave made provision in the new aircraf t types for theinsta l la t ion of A.A .C. gun s, an d in this co un try theseweapons are being specif ied on Burnell i type a ircraf t buil tby the Scot t i sh Airc ra f t and Enginee r ing Co.
The manu fac ture r s ma in ta in th a t no explos ive she l lsma l le r tha n 37 mm . bore and equip ped wi th a tho rough ly
modern fuse , day and n igh t t r ace r and de lay-ac t iona r rangement can be made bore - sa fe and abso lu te ly de tona tor safe . I t is impossib le , the y c la im, for one of the irshel ls , which a re loaded wi th cas t T .N.T . , to explode pre ma tu re ly whi le in the gun . Ar rang emen ts hav e been mad eso th at the explosive charg e is det ona ted af ter th e t race rhas comple ted i t s burn ing .
However perfect an a ircraf t gun, be i t a canon or amachine gun, i t is useless without an eff ic ient mounting,and today the design of a mounting is probably as dif f icult as the design of the gun.
Power-d r iven mou nting s will henc efor th be essentia l onmulti-seater machines, and in the design of such devicesGreat Brita in is undoubtedly ahead of the rest of the world.
A com bina tion of powerful forces mi li ta t e against th e
prod uctio n of a com plete ly efficient m ou nti ng . A pa rtf rom the dif f iculty of evolving an operating mechanismcapable of functioning sa tisfactor i ly under a l l condit ionsof f l ight aerodynamics enter into the problem, for not onlydo pro t rud ing gun ba r re ls compl ica te a f fa i rs , b u t th e sh apeof the actua l tu rre t mu st be carefully considered. Re t r ac tab le , o r h igh ly s t r eaml ined gun pos i t ions seem boundto come into vogue ; even th e re trac tab le ty pe m ust offera s l i t t le d rag a s poss ib le when ex ten ded . Th e rea r tu r re tin the Fokke r G. i , p rev ious ly me nt ioned , and th e fuselagegun posit ions on th e four-engined Boeing b om ber areexcellent examples of the progress made.
Unhappily i t is not possible to discuss a t any length themerits of new Brit ish and foreign gun mo unt ings . I t issignif icant that dur ing public appearances the gun posit ions
on a number of our new multi-engined machines are e i therdummies or are screened with fabr ic .
Mounting ifficultiesAmong the ma jor p rob lems to be f aced to -day a re
those connected with the cooling of internal insta l la t ionsand the def lection, due to the speed of the machine , ofbulle ts fired broads ide . Th e la t t er probl em will becom emore serious as the speed of aircraft and the effective rangeof guns increase , and if higher velocity h as to be obta i nedat the expense of lengthened barre ls addit ional complicat ions will doubtless result .
There is l i t t le news of improvements in the design ofsma l l-bore machine guns . Outb oa rd ins ta l la t ions a relikely to become common in this country, being facil i ta ted,no doub t , by the use of the Browning gun . Modern can t i
lever wings are comp arativ ely f ree f rom to rsion and vibrat ions , o ld t rouble s me t in ou tboa rd ins ta l la t ions .
Present-day single-seaters lend themselves to a var ie tyof arm am ent insta l la t ion s enablin g dif ferent co mb inatio nsof guns to be mo unt ed for dif ferent requ irem ents . Fo rexanrole , Fokker offers the D.21 f ighter with any of thefo l lowing ins ta l la t ions : one moteur canon (Hispano Ycrswith 20 m m . gun) and tw o or four mac hine gu ns (0.3 in.)in the wings; one machine gun of 0.5 in. ca libre f ir ingthrough the a irscrew and two r if le-calibre guns in thewings; two synchronised 0.5 in. guns in the fuselage endtwo 0 .3 in . machine guns in the wings ; o r two 20 mm.canons in the wings and two r if le-calibre machine gunsin the fuselage. Th e Fren ch Dewoitin e D.373 is suppliedwi th four o r s ix machine guns ( the former a rm am ent i s
specif ied for this machine by the French Navy, and thel a t t e r b y t h e L i t h u a n i a n G o v e r n me n t ) ; tw o 2 0 mm.cations and two machine guns ; o r one Hotchkiss h igh-ve loc i ty 25 mm. canon and two machine guns .
Th e im me diate future will doub tless see intensive development work with canons and moun tings for f ree guns . W ecan on ly hope th a t th e weapons which wi ll be r equi red toequip our naissant mili tary aeroplanes will be as highlydeveloped as the m achin es.
