7/27/2019 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.