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Aviation History
1938
1938 - 1639.PDF
i i 80 GOO pounds applied to outer and inner wi> g ^eUicosby pulleys opf*rcct:rig ovet these steel super- strvctutes and hydrauiic jacks pushing up under wings. Ecrch wing *akes 90,000 pounds. Hydraulic system inside plaaa tested by titis conti f Down loads of 50,000pouiidt applied to enginenacelies on each side of plane reproducing weight and puli ai engines. Totat dawn-ioads 180,000 pounds Pholo diagram showing prooi test of Douglas DC-4 super skyliner. Position of ship repro- duces on the ground all loads and stresses anticipated by engineers when plane, fully loaded and traveling at 235 miles per hour is ' —••- ' • i ^^^^HP^^^^BHI^^^^ sent into high angle of attack for climb at rate ol 2,000 leei a minute. Scores oi engineers and experts worked weeks to design and supervise tests in which the one pictured above was the dramatic climax. of 170,000 pounds and s a* loadi. o! 3S,000 pounds to eac.-i wheel were applied to landing gear. Nose whe^-I took upload of 42.000 and sid^-load of ssi This annotated photograph, issued by the Douglas Company, gives a good idea of the general scheme of the tests. STATIC TESTS of the D.C 4 T O quote a Douglas Press release, "Outin Santa Monica, California, Douglasengineers have just finished the jobof flying and landing the nation's largest and finest commercial transport without taking it out of the hangar. " It was a task in which mathematics and a million pounds of lead bars were handled in equal proportions, with slide rules and elbow grease doing their share. " When the last test was finished and the final figures checked and rechecked, the 65,000 lb. D.C. 4, designed and built by Douglas to the order of the five major air- lines, was pronounced ready and fit for its acceptance flights." Normally prototyDe machines are turned upside down for static tests and the loads are piled on the wings and fuselage. The D.C. 4, however, was too large to be handled so unceremoniously. Several rehearsals of the tests were held to ensure that each man knew his job. De- flection readings were taken at 201 separate points on the machine. Some were made to load factors of three and a third times the gross weight of the aeroplane. The most complicated and spectacular of the tests were made on the outer wing panels to simulate deflection duing flight. To repro- duce this condition pulleys and cables were hooked on to the leading edge and upper skin from tall steel structures. Twelve men at the end of blocks and tackles gradually increased the load at given signals, while under the inner wing sections hydraulic jacks, operated from a central control panel, pushed upwards. _ One test was made with the D.C. 4, in the "high angle of attack" position. This reproduced all the forces exerted were the machine to be zoomed at the rate of 2,000ft. a minute from level flight at 240 m.p.h. Mechanics working on control adjust- ments were so far apart that a loud- speaker telephone system had to be fitted up for communication. Showing details of the gear with which loads of 180,000 lb. were applied to the wings of the D.C. 4. Prelude to Initial Flights of America's 30-ton '.-.': v Giant
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