On October 1, 1962, Trans world Airlines (TWA) inaugurated the first fully automatic doppler radar system of navigation on scheduled transatlantic flights. The New York to London flight held the honour of being the first transatlantic flight to operate without a professional navigator as part of the flight crew.
Before this, the professional navigator was an integral part in any long haul flights. The navigator would use a technique called “Dead reckoning” in which the navigator would pinpoint the position of the aircraft using a previously determined position. The navigator would use weather information received from ships and other aircraft to plot an initial heading as well as recommend the speed that would compensate for any drift. He would use any land-based navigation aids to confirm his position but flights over the oceans did not give this option. The navigator would make corrections to the heading and groundspeed if the position of the plane differed from the initial estimate.
Printed tables, formulas or a E6B flight computer allowed the navigator to calculate the effects of air density on aircraft rate of climb, rate of fuel burn and airspeed. Through this, the navigator would be able to determine the point of no return which is the point at which the plane has just enough fuel plus any mandatory reserve to make it back to the airport and the Equal time point where it would take the same amount of time to continue straight to the destination or trackback to the airport. The constant stream of information from the navigator was vital for the pilot to make decisions.
One of the primitive tools we used was called a driftsight. It was sort of a inverted periscope extending from the belly of the aircraft. Laying flat on the deck, one could look through the driftsight at the waves below, assuming we were below the clouds. We lined up two parallel cross hairs in the eyepiece with the movement of the waves, and then could measure our crab angle, or the difference between the aircraft heading and its actual track. Knowing our true airspeed, we could then compute the winds using simple geometry.
-Taken from “Navigating in the Old days” by John Dill
The Doppler radar is a specialized radar that operates based on the Doppler effect to produce ground speed and drift data. The radar emits a electromagnetic signal and analyses the bounced off signal. The Doppler effect or a change in frequency occurs when there is relative motion between the transmitter and receiver. This shift is proportional to their relative motion. Therefore the instrument can determine the proximity between nearby objects and it’s radial velocity.