When I started in BOAC, although a pilot, we all had to obtain Flight Navigators' Licences. I was on Britannia 312s from 1962 until 1964 and have navigated the one at Duxford many times.
The navigation kit consisted of 2 ADFs, 2 VORs, 2 DMEs, a weather radar, a LORAN set and a bubble sextant. When out of range of ADF, VOR and DME we used LORAN, astro and Consul.
LORAN was a hyperbolic long range navigation aid. There was a master ground station and two slaves. The navigator tuned to the correct frequency and lined up on the oscilloscope the two green blips (one from the master station, the other from the slave) to measure the time difference between receiving the two signals. Lines of constant time difference were printed on the nav chart. You plotted a position line corresponding to one of these lines and then tuned to another station to do the same and get another position line.
Consol was an old German wartime long range navigation aid. You used the ADF receiver to tune into the station and listen to a series of As and Ns in morse code. Having counted the number of As and Ns you then found the corresponding line on the chart and drew a position line. It was quite normal to combine a LORAN position line with one from Consol. There were stations at Bushmills in Northern Ireland, one at Quimper in Brittany and one at Stavanger.
Astro navigation was an art in itself. Using an Air Almanac and sight reduction tables you selected three suitable stars and took sights in quick succession. Each star was observed through a periscopic bubble sextant for 2 minutes. During this time the navigator manipulated a toggle switch on the side of the sextant to keep the star in the centre of the bubble to average out the errors produced by the motion of the aircraft. The resulting position lines would, you hoped, produce a nice cocked-hat fix. With practice a 30 min schedule between fixes was straight forward.
You could also combine single astro position lines (the moon and sun by day) with position lines from any other source.
Having got a fix, you then estimated the wind from the MET chart and calculated a course to steer which was passed forward to the pilots. After half an hour you took another fix, measured the difference between the air position and the fix you had just obtained, recalculated the estimated wind, calculated another course to steer, and passed the new course to the pilots. You continued to do this all the way across the Atlantic, Sahara, or Pacific until you got within range of ground stations at the other end.
Difficulties came when cloud cover prevented observation of the stars or when ionospheric conditions affected the LORAN signals, or both. You then had to rely on an airplot and DR positions and hope this didn't go on for too long.
Last edited by Bergerie1; 2nd Sep 2013 at 11:13.