A & N

[earl1937]

  During the 30's, 40's and early 50's, the letter A in Morse code and the letter N in Morse code played a very important role in development and advancement in both military and commercial aviation! How were they used and for what purpose?

[Megalodon]

dot dash .. dash dot

90 degree LF Navigation

 

http://www.taphilo.com/history/WWII/wwii-navigation.shtml

[Traveler]

It was called a "Range" and it was one of the first attempts to create electronic navigation keyways.  It was replaced with Omni ranges in the 60's and 70's.   

[pembquist]

you'l have to look it up but somewhere, somebody, with an airport has an ol fashioned range.  Where you listen to know if your on the beam.

[earl1937]

It was called a "Range" and it was one of the first attempts to create electronic navigation keyways.  It was replaced with Omni ranges in the 60's and 70's.   

"Drum Roll Please", you are correct sir!

[colmbo]

IIRC when on course you heard nothing, Null.  And you had to pay attention not to overfly the station. 

[earl1937]

you'l have to look it up but somewhere, somebody, with an airport has an ol fashioned range.  Where you listen to know if your on the beam.

You are on the right "track". The A and N were radio signals transmitted by a low frequency station. When you crossed or stayed on the area where the N and A came together, you heard a constant, steady signal, which was called a "leg". When you arrived at the radio beacon and crossed it, you would pass over the "cone" of silence and you knew by your charts, where you were. There were low freq ranges all over the U.S. and some forgien countries. Both military and commercial airliners and general aviation aircraft would use these to navigate from point to point. This was accomplished by the pilot by listening in his or her head sets for the signal. To verify that you were going to the station, you would turn your radio down until you could barely hear the signal. If the signal grew as you flew, you were going toward the station, if it disappeared, you were going away. This was called a range orientation maneuver. When you arrived at your destination airport, you consulted your chart for heading to the airport, unless, as in many cases, the transmitter was located on the airport. Of course, these were "non-precision approaches and were nerve racking to say the least, especially in bad weather such as very low ceilings or thunderstorms. The Bombers and fighters during WW2 also used these navigational aids in returning to base after missions.
To shoot approaches to the airport of intended landing, you would first maneuver to pass over the beacon on a heading which was 180 degrees from the direction of the runway in which you intended to land. Example: Cleared to land, runway 27, Atlanta International airport, you would fly a heading of 090 degrees until you passed over the "cone" of silence, then, after determining which speed at which you wanted to work the procedure, 180 knots= 3 miles per minute, 120 knots= 2 miles per minute. Back in those days, 120 knots was the common speed at which to work the procedure. After crossing the "cone" of silence on a heading of 090, you would time, by watch or clock on instrument panel, for 3 to 5 minutes, then you would do a procedure turn by turning right 45 degrees to 135, fly 2 min, then a turn back to a heading of 270 degrees, using a standard rate turn, and with no wind, you should be headed inbound to the airport and you could start descending for landing. If you descended to minimum decent altitude as dictated by your approach chart and you couldn't see the runway or airport, you would then execute a "missed approach", climbing straight ahead to a specified altitude, then start all over again.
When ADF indicator instruments came into use in late 30's and 40's, it really simplified the navigational system, but that is a subject for another thread!

[earl1937]

IIRC when on course you heard nothing, Null.  And you had to pay attention not to overfly the station. 

Thanks for your post, but the low freq ranges, when you were located where the A and N came together, you heard a constant tone. This was referred to as "riding the beam". If you turned your radio way down, you could determine whether or not you were going to or away from the station. Sometimes, more often than not, you would have to bracket the specified range leg by crossing back and forth across the steady tone, using 45 degree intercept angles and eventually you could determine which magnetic heading to fly to go to the station. Of course, you had wind drift calculations to make also to determine the best heading to fly to stay on the "beam".

[Megalodon]

You are on the right "track". The A and N were radio signals transmitted by a low frequency station. When you crossed or stayed on the area where the N and A came together, you heard a constant, steady signal, which was called a "leg". When you arrived at the radio beacon and crossed it, you would pass over the "cone" of silence and you knew by your charts, where you were. There were low freq ranges all over the U.S. and some forgien countries. Both military and commercial airliners and general aviation aircraft would use these to navigate from point to point. This was accomplished by the pilot by listening in his or her head sets for the signal. To verify that you were going to the station, you would turn your radio down until you could barely hear the signal. If the signal grew as you flew, you were going toward the station, if it disappeared, you were going away. This was called a range orientation maneuver. When you arrived at your destination airport, you consulted your chart for heading to the airport, unless, as in many cases, the transmitter was located on the airport. Of course, these were "non-precision approaches and were nerve racking to say the least, especially in bad weather such as very low ceilings or thunderstorms. The Bombers and fighters during WW2 also used these navigational aids in returning to base after missions.
To shoot approaches to the airport of intended landing, you would first maneuver to pass over the beacon on a heading which was 180 degrees from the direction of the runway in which you intended to land. Example: Cleared to land, runway 27, Atlanta International airport, you would fly a heading of 090 degrees until you passed over the "cone" of silence, then, after determining which speed at which you wanted to work the procedure, 180 knots= 3 miles per minute, 120 knots= 2 miles per minute. Back in those days, 120 knots was the common speed at which to work the procedure. After crossing the "cone" of silence on a heading of 090, you would time, by watch or clock on instrument panel, for 3 to 5 minutes, then you would do a procedure turn by turning right 45 degrees to 135, fly 2 min, then a turn back to a heading of 270 degrees, using a standard rate turn, and with no wind, you should be headed inbound to the airport and you could start descending for landing. If you descended to minimum decent altitude as dictated by your approach chart and you couldn't see the runway or airport, you would then execute a "missed approach", climbing straight ahead to a specified altitude, then start all over again.
When ADF indicator instruments came into use in late 30's and 40's, it really simplified the navigational system, but that is a subject for another thread!

 Thank its posted in my link 

[Traveler]

An interesting side note if you take a look at many areas on a modern day sectional map, you can see that many of the original Range towers are still standing.  They make great check points for students on training  Cross Country flights.  Many of the training aircraft I fly are all glass cockpits now. That makes for lazy students and instructors both when it comes to navigation.  So I like to take my students up on a long cross country in my J3 Cub.  As they attempt to navigate by seat of the pants at the blistering speed of 50MPH.  No radio, No VOR, NO GPS.  It's great fun to watch them sweat.  When it becomes obvious that they are lost and it doesn't take very long for that to happen, the real fun begins.  As we watch the fuel float gage in the fuel tank slip lower and lower.  The cub will stay airborne an honest 3  hours burning 4 gallons an hour at a cruise setting.  I have the student plan at 5 gallons an hour to keep them honest and keep their moms happy.  Teaches them how to really use that Sectional and the benefit of understanding exactly how to deadreckon and be able to know exactly where they are on that sectional where the next usable airfield is and how long it will take to get to it and how much fuel it will take.  They learn to love all those small towns that put the town name on their water tower.   I also take them into controlled airspace for light gun signals at a semi-busy towered airfield.   Don't worry, perfectly legal , My cub has all the modern toys.  Transponder, radio, Omni and GPS.  Every student I have every taught will never get lost, and has a tail wheel endorsement.

[earl1937]

An interesting side note if you take a look at many areas on a modern day sectional map, you can see that many of the original Range towers are still standing.  They make great check points for students on training  Cross Country flights.  Many of the training aircraft I fly are all glass cockpits now. That makes for lazy students and instructors both when it comes to navigation.  So I like to take my students up on a long cross country in my J3 Cub.  As they attempt to navigate by seat of the pants at the blistering speed of 50MPH.  No radio, No VOR, NO GPS.  It's great fun to watch them sweat.  When it becomes obvious that they are lost and it doesn't take very long for that to happen, the real fun begins.  As we watch the fuel float gage in the fuel tank slip lower and lower.  The cub will stay airborne an honest 3  hours burning 4 gallons an hour at a cruise setting.  I have the student plan at 5 gallons an hour to keep them honest and keep their moms happy.  Teaches them how to really use that Sectional and the benefit of understanding exactly how to deadreckon and be able to know exactly where they are on that sectional where the next usable airfield is and how long it will take to get to it and how much fuel it will take.  They learn to love all those small towns that put the town name on their water tower.   I also take them into controlled airspace for light gun signals at a semi-busy towered airfield.   Don't worry, perfectly legal , My cub has all the modern toys.  Transponder, radio, Omni and GPS.  Every student I have every taught will never get lost, and has a tail wheel endorsement.

Outstanding!!! I did not know there were any instructors left that teach what you are teaching your students!! As your students gain experience and flight time in the old log book, their respect for you will grow and grow!
 

[earl1937]

dot dash .. dash dot

90 degree LF Navigation

 

http://www.taphilo.com/history/WWII/wwii-navigation.shtml

FYI, all radio ranges had 4 legs, usually 90 degrees apart: the way it worked was this: In the Northeast quadrant from the transmitter, the letter A was all you could hear. in the Southeast quadrant, all you could hear was an N. In the Southwest quadrant, all you could hear were A's and in the Northwest quadrant, all you could hear was N's. You could take your stop watch and as you crossed one of the four legs, you could time your time across the signal and you could tell how far you were from the station. If I remember right, we used the number 6 as the common factor in computing distance. If it took you 3 seconds to cross the leg of the range, you were 18 miles from the station. Then you had to figure out if it was North or South of you, if you were flying Easterly or Westerly. I used to measure it twice and if the time to cross was larger on the second crossing of the signal, I knew I was getting further away from the transmitter. Sounds really complicated, but after you did it a few times in practice with an instructor, was pretty simple.

[colmbo]

Every student I have every taught will never get lost, and has a tail wheel endorsement.

Nice.  You sound like the guy that taught me to fly.  Very different from a "school" setting.  Was working on the commercial, doing a dual cross-country.  A checkpoint I had plotted (tramway across a river) no longer existed so I didn't find the checkpoint and therefore for time entry in my log as we flew.  No biggee, just fly to the next checkpoint and do elasped time calcs to it.  But Nooooo says the instructor, if we don't put something in the log the Chief Pilot will have a fit.  Seems it was more about filling out the log than actually doing some navigation.

FYI I've never gotten lost, even scud-running through the backwoods of the Yukon when crossing Canada.

[colmbo]

Thanks for your post, but the low freq ranges, when you were located where the A and N came together, you heard a constant tone.

Yeah, was sitting at work last night and remembered that.  Never used an LF range.

[earl1937]

Yeah, was sitting at work last night and remembered that.  Never used an LF range.

Since starting to play this game three years ago, it has revivied memories that I had long ago forgotten. I did get my instrument ticket in 1951 at the ripe old age of 17, had a grand total of 212 hours flight time. Took my training in a Piper PA-12A, "super cruiser", cruise at fantastic speed of 112MPH. I took one flight with my new ticket just to see if I could really do it, climbed up through a big hole in the clouds, headed to Atlanta, called FSS and filed en route. Had about a 1200 foot ceiling as I recall at ATL but had no problem getting in, the problem was getting home. We had no approach system of any kind at home, so pulled out the old sleeping bag Mr. Swanson kept in the baggage compartment, curled up under the right wing and slept until next morning, scud ran back home next day. Shows you how stupid I was at times back then because a lot of the mountain tops were obscured by clouds, but finally got home OK.
One of the problems with LF ranges was they were affected by atmospheric conditions! The signal was bounced off the Ionosphere and so it was bad to "bend" sometimes. Even the "Northern Lights", which I am sure you see a lot of times at night, would affect the signal. Then VHF VOR system came on line and was fantastic as long as you had line of sight with the transmitter. Most VOR's in the U.S. were reliable for about 70 miles because of the curve of the earth, but that is a subject for another day!
Before I report to the Big hangar in the sky, I would dearly love to retrace some of my steps when I was learning to fly, with the knowledge that I now have. Probably wouldn't be as much fun though. Flying into the unknown, not knowing what was behind that cloud up ahead, or where or not you might find the airport manager closed up and gone and you couldn't get fuel. Call him at his home, come out and sell you 12 gallons at 24 cents a gallon, call dad to take the old 49 Plymouth over to the airport, turn on his lights where I could see where I was supposed to land. Had great lights on the Cessna 180 which a local Doctor owned, so was no big deal at night to land on that 1800 foot dirt strip. Ha, I better shut up!