The earth inductor compass was popular in the United States for long distance flights in the period 1924-1934. Charles Lindbergh relied on this type of compass on his New York to Paris flight to maintain course until it malfunctioned. It's primary attraction was that it was far more stable than liquid-filled "whiskey" magnetic compasses and featured a controller that could dial in a heading that could be followed with a left/right indicator similiar to that used for VOR navigation decades later. This made is far easier to hold a heading over long periods, particularly when fatigued. It used a wind-driven generator to create an induction field that created variable current as it interacted with the Earth's magnetic field. Less reliable than a liquid compass, it fell out of favor by the mid-1930s, replaced by gyroscopic heading indicators. Albert Hegenberger oversaw its development in the early 1920s for the U.S. Army Air Service.
Caption:
Lindbergh relied on this type of compass in the Spirit of St. Louis to maintain course on the way to Paris until it malfunctioned.
