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Barometric Altimeter

Kollsman Inventor Paul Kollsman was among the innovators responsible for solving key mechanical challenges in the early days of aviation. His particular claim to fame was his invention of the first and ultimately most successful barometric altimeter, which made possible the notion of flying by gauges, also known as "blind flight," or "instrument flight."

Born on Feb. 22, 1900, in Germany, Kollsman studied mechanical engineering in Stuttgart and Munich. He emigrated to the United States in 1923 and began work as a truck driver's assistant before finding a position as a mechanic for Pioneer Instrument Co., a subsidiary of Bendix, near Brooklyn, New York. Pioneer was a maker of compasses, gauges, accelerometers and other instruments for airplanes. There, Kollsman was uninspired, and so he left with dreams of building devices of his own that he could believe in. In 1928, with $500 as capital, he started his own company, Kollsman Instrument Co.

Aviation itself was in its very early days, with the Wright brothers having completed their historic flight at Kitty Hawk, N.C. in 1903. Altimeters existed that could accurately determine an airplane's height within a few hundred feet, and this was fine for good light and perfect weather, but it made flying at night or among clouds or fog virtually impossible. Kollsman knew an altimeter that responded to changes in barometric pressure could change all that, and his 1928 invention measured air pressure and determined altitude with accuracy within just a couple of feet.

It was a struggle to get anyone to take his device seriously at first. Then aviator James "Jimmy" Doolittle agreed to try Kollsman's altimeter on an historic flight on Sept. 24, 1929. Employing Kollsman's altimeter in combination with a gyroscopic, artificial horizon gauge invented by Lawrence Sperry, a ground-based radio navigation system for communicating the aircraft's position, and a cockpit navigation display built by the National Bureau of Standards, Doolittle completed the first blind flight, proving it possible to fly "by the gauges."

Before too long, Kollsman's altimeter had nearly cornered the altimeter market, and he continued to improve on these devices while creating a variety of other dashboard instruments out of his Elmhurst, N.Y. plant and Glendale, Calif. branch factory. He acquired more than 200 patents and supplied products for planes around the world in addition to technology for the U.S. military, World War II airplanes, and U.S. Apollo missions, including a sextant used on Apollo 13.

His altimeter became known as the "Kollsman Window," as it incorporated a window that allowed pilots to dial in a setting manually for calibrating barometric pressure at current sea level. To this day, pilots coming in for a landing may ask radio communications tower operators to give them their "Kollsman number," or atmospheric pressure in the area, which tells him or her whether an adjustment is needed in the plane's altimeter for accurate landing.

Kollsman died on Sept. 26, 1982. Today Kollsman, Inc. is based in Merrimack, N.H., where the company continues to develop avionics and electro-optic instrumentation, as well as aerospace equipment and defense system technology.

[May 2005]

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