SILENT FLYING

Evening Post, Volume CXIX, Issue 128, 1 June 1935, Page 29

SILENT FLYING

RECENT EXPERIMENTS

WHAT GERMANY HAS DONE

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-oil 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 npw, 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 noise 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,1 ■ who would welcome silent motors and ■aeroplanesif or the surpris_e element offejped 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.. Eeal estate men, faced with declining property values near- airports, would welcome aircraft silence to restore quiet once again to airport Vicinities.. . -.- '. '...:■. ; Airports npw 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 in silent engineering held a crowd of spectators fascinated at the recent all-Ameriean air races at'Miaml. . Nine .new attack aeroplanes i from Fort 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 hew 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 war time was not lost upon the crowd. ..--.'' 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 "cerit. Wer regular fuel costs has been, achieved, because these engines burn fuei oil. 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. The Lufthansa began experimenting about five years 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 freight service aeroplane. It was not used in a passenger machine until 1933. Last year it was tried out in two-motored machines.. A huge fourmotored ship, the Deutschlarid, is the only one of its type in service, at present.'She flies between Berlin, Copenhagen, and Malmo. A sister ship, the Hindenburg, is being similarly fitted out at Dessau. William Harper, jun., of Port Washington, an American aviation pioneer,' has developed a quiet aviation engine which can be operated on petrol, alcohol, or distillates., By the use. of, exhaust gases on ■ a super-charger method the Harper engine is so muffled that at 3500 revolutions a minute it is nearly silent. .. During tests at Brooklyn, Mr. Harper said, the engine could not be heard in apartments 100ft away, though it-was summer time 'and windows were open. This muffling, furthermore, has been accomplished with a' negligible loss of power. A NEW PAGE. Last year in Berkeley, California, William and George Besler wrote a new page of aviation history when they piloted what was said to be the first successful steam-powered flight. The engine was installed in 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-power in block tests. When taking off, the Besler aeroplane made little noise, and William Besler's shout of "Hallo" could be heard plainly above the swishing of. the propeller as he flew within 100ft 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.