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National Resources Planning Board 



structure, is also based on theoretical work in a 

 university. 



Propellers 



(1) Metal propellers: The use of forged duralumin 

 i)lades dates from 1925 when the industry developed 

 from Albert Sjdvanus Reed's original invention. More 

 recently, research efforts in the industry are being 

 directed toward hollow duralumui or steel blades, or 

 the use of magnesium or reinforced-plastic material to 

 avoid increasing weight for the greater power required 

 by the new engines. 



(2) Variable pitch: Metal propeller blades with var- 

 iable pitch, automatically governed, and feathering, 

 have been developed by the industry on its own initia- 

 tive, as mentioned previoush'. 



(3) Stress measurement: The design of metal pro- 

 pellers for modern engines required exact knowledge of 

 the distribution of stress in the blade imder operating 

 conditions. Methods for making such measurements 

 have been developed by the industrj' in connection 

 with a university laboratory. 



Materials 



(1) Duralumin: This strong alloy of aluminum was 

 developed and made generally available by the Alu- 

 minum Compan}' of America after extensive research 

 undertaken in connection with the Navy's airship 

 program. 



(2) Stainless steel: This remarkable material and 

 means to spot weld it are available in the metallurgical 

 industry. It may become important as airplanes in- 

 crease in size. 



(3) Magnesium : As a result of research in the metal- 

 lurgical industry, alloys of magnesium are becoming of 

 increasing use, especially for engine parts and castings. 



(4) Extruded sections : The industry has developed a 

 comprehensive set of standard structural shapes for 

 extrusion with consequent gain in efRciency and reduced 

 cost of manufacture. Research by the industry has 

 established the stability and strength properties of such 

 sections. 



(5) Plastics: Many uses for plastics are being found; 

 in particular, the flexible transparent plastics which 

 replace glass. Research is conducted by the industry 

 and by the government. 



Accessories 



(1) Soundproofing : The industry has evolved, tlirough 

 its own research, effective methods and materials for 

 soundproofing airplane cabins. The improved passen- 

 ger comfort has done a great deal to i)opularize air 

 travel. 



(2) Fuel tanks: Research by the industry has pro- 



duced safe riveted and welded fuel tanks and tanks 

 lined with synthetic rubber. 



(3) Supercharges: Both exhaust-driven and gear- 

 driven superchargers have been developed by the indus- 

 try to boost the power of engines at altitude. As a 

 result, air transport planes can fly high enough to avoid 

 most of the bad weather. 



(4) (ivro pilot: Firet introduced by Sperry in 1931, 

 the automatic gyro pilot has revised flying technique as 

 regards large airplanes and has contributed greatly to 

 safety in flight. 



(5) Radio: Direction finders, radio beacons, two-way 

 radio telephone sets, and other radio aids to navigation 

 have had an important effect on the growth of air lines. 

 Without radio, operations could not be conducted with 

 safety in bad weather. Radio eqiupment is the result 

 of research in the radio industry. 



(6) Gyro compass, sensitive altimeter, turn and bank 

 indicator, and other flight instruments have been devel- 

 oped by the industry. They are indispensable. 



(7) De-icing equipment: To permit flight under icing 

 conditions, the industrj'' developed de-icing equipment 

 of very effective nature. Such equipment is essential 

 to the maintenance of schedules on northern routes in 

 winter. 



(8) Blind-landing equipment: Current research by 

 the industry under the direction of the Civil Aero- 

 nautics Authority is developing radio means for guiding 

 an airplane to a landing in times of no visibility. 

 Blind-landing research was initiated in 1926 by the 

 Guggenheim Fund, and the first demonstration made 

 by Maj. James H. Doolittle, September 24, 1929. It is 

 expected that the next important improvement in air 

 transport service awaits the successful reduction to 

 practice of means now being experimented with. 



Military and Naval Research 



Research within the Army and Navy deals primarily 

 with the adaptation of the airplane to service require- 

 ments and the development of armament and other 

 special equipment. For this purpose both the Anny 

 and Navy maintain extensive research facilities and 

 scientific staffs. 



Special equipment is developed witliin the service, 

 with N. A. C. A. advice when requested, and is usually 

 built by the industry. Examples: Navigating instru- 

 ments, machine guns, cannon and moimts, bombs, bomb 

 sights, torpedoes, catapults, arresting gear, hoisting 

 gear, special radio and signaling apparatus, photo- 

 graphic and mapping equipment. 



Just as certain improvements in the airplane leading 

 to greater speed, pay load and economy have resulted 

 in the growth of an air transport industry, so also have 

 the same improvements resulted in the growth of the 

 military and naval air forces. The relative importance 



