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Real Pilots Fly Adcock Ranges

A look at the navigation systems that preceded today's technology.

[Courtesy of Peter Garrison]
Gemini Sparkle

Key Takeaways:

  • Early aerial navigation evolved from visual landmarks and beacon lights to instrument flying, with the Low-Frequency Four-Course Range (LFR) introduced in the late 1920s being crucial for making instrument flight commercially practical.
  • LFR systems guided pilots using four distinct radio "beams" created by overlapping A (dot-dash) and N (dash-dot) Morse code signals, which produced a continuous tone when a pilot was on course.
  • Navigating with LFR involved complex techniques like maintaining a continuous tone, understanding signal strength, and identifying the "cone of silence," requiring significant pilot skill and limited onboard equipment.
  • These early methods, demanding and challenging as depicted by a 1953 chart's features, were eventually superseded by more advanced systems like VAR and VOR, highlighting a vast technological leap to modern GPS.
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A friend bought me an old aeronautical chart he found in a map store. Dated August 16, 1953, it covers roughly the same area as the current Los Angeles VFR [visual flight rules] terminal area chart. In the lower margin are the words: “PRICE 25 CENTS.” You got more square miles for your money then than you do today, even taking inflation into account.

The scene depicted on the chart is at once familiar and strange. Many small airports have vanished; runway diagrams of some larger ones have changed. There are only three VORs [very high frequency omni-directional range]: Long Beach, Ontario, and Palmdale. The airways are 10 statute miles wide—the FAA did not go nautical until the mid-1960s—and they are defined by what look like localizers. They aren’t localizers, however; they’re the beams of four-course ranges.

Peter Garrison

Peter Garrison taught himself to use a slide rule and tin snips, built an airplane in his backyard, and flew it to Japan. He began contributing to FLYING in 1968, and he continues to share his columns, ""Technicalities"" and ""Aftermath,"" with FLYING readers.

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