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How to Set an Analog Altimeter

Analog altimeters are used to indicate an aircraft's altitude. They are simply precision aneroid barometers calibrated to indicate altitude above mean sea level by measuring changes in atmospheric or barometric pressure. Atmospheric pressure can vary along an aircraft's route, so it is necessary to periodically adjust or set the altimeter. The Federal Aviation Administration requires an adjustment every 100 nautical miles of flight and before takeoff and landing. The altimeter is set by a knob on the front. Twisting the knob right or left changes the barometric pressure reading in the Kollsman window and simultaneously moves the altitude indicator hands. The altimeter is set by either setting the altimeter hands to the correct altitude or the sea level barometric pressure, called the altimeter setting, in the Kollsman window.

Things You'll Need

  • Analog barometer
  • Current sectional chart
  • Current Airport Directory
  • VHF aircraft radio
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Instructions

  1. Setting by Known Elevation on the Ground

    • 1

      Find the departure airport's elevation or altitude on a current sectional chart. It̵6;s listed directly under the airport̵7;s name.

    • 2

      Look up the airport's elevation in a current Airport Directory.

    • 3

      Look for signage near the runway indicating the airport's elevation .

    • 4

      Turn the knob on the front of the altimeter until the airport̵7;s elevation is indicated by the altimeter̵7;s hands.

    Setting by Barometric Pressure Before Landing

    • 5

      Find the airport̵7;s Automated Terminal Information Service (ATIS) frequency on a current sectional chart.

    • 6

      Tune the VHF aircraft radio to that ATIS frequency.

    • 7

      Listen for the altimeter setting given in inches of mercury.

    • 8

      Turn the adjustment knob until the ATIS altimeter setting is lined up with the indicator mark in the Kollsman window.

    Setting by Barometric Pressure along Flight Route

    • 9

      Find the frequency of a nearby Automated Weather Observing System (AWOS) on a current sectional chart.

    • 10

      Tune the aircraft radio to that frequency and listen for the altimeter setting.

    • 11

      Find the frequency of a nearby Flight Service Station (FSS) on a current sectional chart.

    • 12

      Call the FSS on the VHF aircraft radio.

    • 13

      Identify your aircraft and politely request an altimeter setting. Set the altimeter to the new settings.

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