Up There, Down Here

With the only refrigerated wind tunnel and the biggest low-pressure chamber in the U.S. aviation industry, Airesearch Co. of Inglewood, Calif. is developing equipment to send planes toward the stratosphere, whither the air battles of World War II are rapidly climbing. The refrigerated wind tunnel, an enormous doughnut 25 feet across, made of tubing three feet in diameter, contains a 300-m.p.h. wind that blows at temperatures down to -90DEG Fahrenheit.

The low-pressure chamber, 11 ft. in diameter and 45 ft. long (it will hold the fuselage of any pursuit ship or test segments of bombers), can simulate air conditions from sea level to 65,000 ft. Much that comes from these two laboratories is secret, but last week three of their products were announced:

Oil Cooler. Hot oil from airplane crankcases is usually forced into air-bathed tubes for cooling. But at high altitudes this system works too well. Air is often so cold that oil closest to the pipe surfaces freezes and insulates the circulating unfrozen oil against the cooling blast. So, to keep the system from breaking down, oil is usually bypassed around the cooler and therefore lubricates at temperatures too high for efficiency. Airesearch has developed a cooler that works in high-altitude cold. It regulates the flow of cooling air through shutters, which are narrowed when the oil becomes too cold, so that the oil remains at an even, efficient temperature.

Intercooler. Not only oil but air has to be cooled for airplane engines. To supply enough oxygen for an engine at high altitudes, compressed air has to be blown into its carburetor. Though air may be as cold as -40DEG F. when sucked into a supercharger (TIME, Aug. 18), it often heats up to 450DEG F. upon compression, and must be cooled to between 30DEG and 100DEG F. before it is fed to the carburetors. The coolers used are simply air scoops which pour wind around small pipes carrying the hot, supercharged air. Intercoolers on early Flying Fortresses weighed 92 lb. for each of four engines. Airesearch has produced coolers weighing only 32 lb. each--giving each Fortress an extra 240 lb. of useful load.

Air Vent. For substratosphere military flying, supercharged cabins are needed in planes, and the compressed air makes the crew feel hot, stuffy and uncomfortable. Airesearch's solution: an automatic outlet vent whose cone-shaped plug, controlled by an altitude-sensitive device and powered by the energy arising from differences between inside and outside pressures, varies the opening's size. With it is combined a safety valve ("overriding control") which lowers the pressure inside the cabin if the plane ventures into extreme low-pressure altitudes (above 40,000 ft.), where a supercharged cabin with its 8,000-ft. interior pressure might otherwise burst.

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