Altimeter - History of Altimeter

Altimeter

Paul Kollsman invented the altimeter in the United States in 1928. The altimeter is a very important instrument in airplanes. It is the device that tells the pilot the height, or altitude, of the aircraft. Before his invention, on cloudy or foggy days, pilots could not be sure how far above ground they were. This made flying in these conditions very dangerous. His invention made it much safer for pilots to "fly blind".

Paul Kollsman's altimeter was a "pressure altimeter", meaning that it worked by measuring the air pressure outside the airplane. Air pressure gets lower as you travel higher, so the altimeter converted the measured air pressure into height.

  • The atmospheric pressure changes based on the weather. Before takeoff, the pilot would have to adjust a knob on the altimeter to compensate for the weather that day.

  • The altimeter had to be in contact with the outside air to work. There was an inlet that ran between the outside of the plane and the housing of the altimeter. Two capsules that had been emptied of air changed size based on the air pressure outside them. The size change of these capsules was converted to the movement of the needle in the altimeter's dial.

  • Paul Kollsman was born in Germany in the year 1900. He studied civil engineering in Stuttgart, and at the Technical University of Munich. He moved to the United States in 1923.

  • Other kinds of altimeters have been invented. A radio altimeter can measure the distance between an aircraft and the ground below it. The device sends a pulse of radio energy toward the ground, and it measures the amount of time it takes for the signal to reflect back. The American Lloyd Espenscheid invented the radio altimeter in 1924, but they weren't sold until 1937.

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