SEEN NOT HEARD

Evening Post, Volume CXIX, Issue 110, 11 May 1935, Page 28

SEEN NOT HEARD

SILENT AIKCEAFT

PRESENT EXPERIMENTS

Silent aircraft for the man on the ground as well as the passenger in the air are now being pioneered by military, commercial, and private aeronautical engineers of-the world, writes "A.D.H." in the "Christian Science Monitor." A new silent Diesel engine perfected for civil aircraft in Germany has once«again "focused attention on other silence designs which' have been worked out, not only for petrolpowered engines but also for new departures into the fuel-dil and. steampowered realms. ■ ' Noise elimination campaigns are spreading with such success into surface transport,' office buildings, city streets^ traffic,- and many other-ground activities,-and so rapidly, that.in time the noise"that comes from the-skies from aeroplanes will have to be considered" for elimination. There is small doubt that this innovation, though probably 'radical now, would eventually be welcomed.by every branch of the aeronautical industry. \ Eliminating aeroplanes sounds from the ear seems.likely to be accomplished by the cumulative effect of reducing the noises of. Whistling'struts, dampening areas of the aeroplane's, surfaces -from which sound may rebound, and cutting propeller "swish" by slowing-' down propeller speed without reducing blade efficiency. "" MILITARY ADVANTAGE. There are the .military men, for instance, \ who . would welcome silent motors and aeroplanes for the surprise element offered them, in being able to launch attacks from the air and recover before anti-aircraft guns of the enemy could get into action. Commercial operators, having spent thousands of dollars to achieve silence inside their craft, could benefit dwellers on the ground. Real estate men, faced with declining property values near airports, would welcdme aircraft silence to restore quiet' once again to airport vicinities. ■-• ■ Airports 'now isolated from the centres of cities because of their high noise factors would again be welcomed closer. Furthermore, the problem of ground transport^ which Vexes air transport operators,' might be solved^ One of the United States Army Air Corps' latest experiments iri silent engineering held a crowd of-spectators fascinated at the. recentVall-American air races at Miami. ■ Nine new attack aeroplanes from Port Crockett, Texas, deployed' across the'" airport at* a speed of 150 miles an hour,«the roar of their motors hushed by big collector rings on their exhaust stacks. These new attack aeroplanes are capable of carrying an armament of five machine-guns and 3001b of bombs; so that the significance of the damage that a large force of these aeroplanes could do in wartime was not lost upon the crowd. '-. ..;,■;• GERMAN SILENCE EXPERIMENTS. In Germany, the'noiseless, aeroplane is already in sight. The Lufthansa has eight aeroplanes" fully Diesel-equipped, and another is being fitted out. A saving of 65 per cent, over regular fuel costs has been achieved, because these, engines burn fuel oik. In addition to being quieter in operation, the motor is safer, due to lessened'danger of'fire from a crash and absence of an electrical system. ■-, v The Lufthansa began experimenting about fivo years1 ago; with a single Diesel engine. It was tried out in empty aeroplanes for:a year and a half and in that period, was greatly improved. In 1932, the first Diesel was installed in,.a.fr.eight..service aeroplane. It was not used- in a jiasseflger machine until 1933. Last year ; ifewas tried out in two-motored machines./ A .huge four-motored ship, the .Deutschland,- is the only one of its type in service at present. She flies between Berlin, Copenhagen.and'Malmo. 'Asister-ship, the Hindenburg, .is*being! similarly fitted out?at; Dessau.;. • . . William Harper, :jun.i" of Port Washington, .an American' aviation pioneer, has developed;a:quiet aviation engine which "A can *be ibperated .oh petrol, alcohol, or < distillates. *By the use of exhaust' gases' "oh -a^. 'super-charger method, the Harper engine \ is so muffledIthat^ atr"3soo revolutions a minutest;is. nearly silent.''■"•■» ■ '.~Y"<'.■' During Jests' atfßrooklirh,; Mr. Harper said; the ehgih'e"4 could hot be"; heard ;ih apartniehts 100 Ifeet away, :though -it was summertime and windows ■were open. This muffling, furthermore, has; been- accomplished with a/negligible loss: of power. ; . ■ ■■- ; Last year in Berkeley, California, William . and-..George. .Besler, wripte- a new page of. aviation history whenvthey -piloted- what, was said, to be -'theY first successful. steam:pow.ered flight:. The engine was.installedan a. standard biplane; and; except for the two cylinders which .projected above the hood, there was nothing .to distinguish .the aeroplane from regular, craft. The Besler, engine, using ;an extremely efficient- '. and : quick-acting flash boiler,: developed :90 horse-power in flight and ■ 150'horse-power4 in block tests. When taking off, the Besler aeroplane made little noise 'and William Besler's shout of "Hallo" could be heard plainly -fabove the swishing of the propeller as he flew within iOO feet of a group of cameramen. The Beslers estimated that the aeroplane would fly 400 miles on 40 gallons of fuel oil. The boiler for their engine requires only two gallons of. water, which is used over and over again. •