Harmon Technologies, Inc.

VOR Displays

N4907J has two VOR displays.  The top display receives information from the NAV-1 radio and the bottom display shows information received from the NAV-2 radio.  This provides two independent navigation displays.  (The NAV-1 data may also be displayed on the HSI at the pilot's option.)

The top display also can receive glideslope information from an Instrument Landing System if the airport is so equipped.  In this area, Logan, Manchester, Hanscom, and Lawrence are all ILS equipped airports.  ILS allows sage descent in the clouds to about 200 feet above the ground and allows flight operations to continue in most weather conditions.  It is the same system used almost all of the time by the airlines.

VOR is a highly accurate navigation system that can measure the direction from a ground based transmitter and display how the airplane's position relates to the magnetic course that is dialed in by the pilot.  VOR navigation is the mainstay of instrument flight and has been in use since the late 40's.  It is now gradually being replaced by GPS but this will take years.  Most airlines are still using VOR as their primary navigation (except on long-range international flights where inertial navigation or Loran is used).

Once the proper station is set on the radio and the desired course is dialed in, the needle indicates if the plan must fly to the left or right to be on course.  When on an ILS approach to an airport, a second horizontal needle indicated if the airplane is above or below the desired glideslope.

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