Archimedes Archive: Kollsman’s Barometric Altimeter

ASK OCE — January 12, 2007 — Vol. 2, Issue 1

Up is up and down is down. That much is easy for a pilot flying by the clear light of day. But at night or when a fog rolls in, a pilot must rely on instruments for guidance. Without them, even the most experienced pilots can become dangerously disoriented. Inventor Paul Kollsman’s barometric altimeter was among the key innovations that allowed a pilot to safely “fly blind” using cockpit instruments alone.

Born in 1900 in Germany, Kollsman studied mechanical engineering in Stuttgart and Munich. He came to America in 1923, eventually landing a position as a mechanic for Pioneer Instrument Company. Pioneer manufactured compasses, gauges, accelerometers, and other instruments for airplanes. But the work did not inspire Kollsman, who dreamed of creating his own avionics instruments. In 1928, with $500 as capital, he started his own company, Kollsman Instrument.

At this point in history, altimeters existed that could accurately determine an airplane’s height, but only within a few hundred feet. For fair-weather flying this was acceptable, but flying at night or among clouds or fog was still virtually impossible.

In 1928, Kollsman designed a new altimeter that responded to changes in barometric pressure. It was so accurate that it could determine accurate altitude within a couple of feet.

Though his invention was a tremendous feat of design and engineering, it was difficult at first to get anyone to take it seriously. That changed on September 24, 1929, when aviator James “Jimmy” Doolittle agreed to try Kollsman’s altimeter on a 15-mile test flight. Using Kollsman’s altimeter in concert with three instruments by other manufacturers, Doolittle completed the first blind flight, proving it possible to fly “by the gauges.”

Soon Kollsman’s instrument had practically cornered the altimeter market. He opened manufacturing plants in Elmhurst, New York, and Glendale, California, where he continued to make improvements to the altimeters. His altimeter became known to pilots the world over 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. In addition to altimeters, Kollsman developed a number of other cockpit instruments at his factories.

Over the course of his career, he acquired more than 200 patents and manufactured products for World War II airplanes as well as the Apollo missions, including a sextant used on Apollo 13 that helped guide it back home to earth. He was awarded the Guggenheim Medal for his notable achievement in the advancement of aeronautics.

Kollsman, Incorporated, now located in Merrimack, New Hampshire, still designs and manufactures avionics flight instruments, night vision equipment, lasers, and medical diagnostic equipment.