Navigation in the 1940s: The Four Course Radio Range
Why Aviation Stack Exchange recommends it
Aviation Stack Exchange answerers point people to it when explaining how pre-VOR radio range navigation and its audio signals actually worked.
Recommended by 1 people across 1 different months, 2016 to 2018.
What it is
A short demonstration of the 1930s-1970s four course low-frequency radio range, built as a scale model on the 28 MHz amateur band by the staff of Radio Station WWRB and Airline Transport Communications. It explains how pilots followed Morse code tones to stay on course and links approach plates showing how it was used.
Cited in 1 Wikipedia article, including Low-frequency radio range.
What people said
Recommends Mike Sowsun · 2017-08 · Aviation Stack Exchange · on “What navigational aid(s) would WWII bomber pilots have used while flying in instrument conditions?”
The accident report is referring to Radio Range navigation which predates ADF or VOR navigation. Radio Range is used by listening to a radio tone. When the pilot is on course, he hears a steady tone. If off course to the left or right, the steady tone is replaced by a "dah dit" or "dit dah" morse code signal. Because the antenna iced up, they were unable to hear the signal and had no directional guidance. More info: Wikipedia Radio Range [LINK] YouTube Video: Four Course Radio Range [this video]
Cites user14897 · 2016-09 · Aviation Stack Exchange · on “What was the range of a low-frequency radio range station?”
The low-frequency radio range [LINK] is a historic navigation aid that was in use from the 20's to the 70's. I find it quite interesting. Using AM frequencies, what was the range of a high power LFR station? A video on YouTube [this video] suggests it was even used to cross the Atlantic with stations in Greenland. [LINK] Source [LINK] , LFR across the U.S., 1933. Secondary question , based on the approach plate below, the red rectangle area shows what I believe is the AM frequency. What about the other four VHF(?) frequencies? The frequencies seem to correspond to the ranges used by today's FSS/CTAF and military UHF. Searching CAA historic regulations wasn't helpful. [LINK] Image source [LINK]
Cites mins · 2018-11 · Aviation Stack Exchange · on “Were there ever instrument approach procedures utilizing only Four Course Range Navigation?”
Yes such approaches have existed. As early as 1944 the North America Low Frequency Radio Range [LINK] (aka Four-Course Range and Adcock Range [LINK] ) network was quite developed. There are several approach plates using this type of radio aid, e.g. this one from May 1944 for Meridian [LINK] : [LINK] Source [LINK] The station is used for IAF and FAF. The approach is done using 334°/154° headings. None of them, nor the station are aligned with a runway, this looks like a circling maneuver. Other plates: Fort Chimo [LINK] (Quebec) Joliet [LINK] (1957) Some editions of the AAF Radio Facility Charts can be bought online, but the edition of June 1944 [LINK] has been scanned by North Texas Universi