The FDU-70 Flux Detector Unit is a 2 axis sensor that provides long-term magnetic heading data to the compass system. The FDU-70 perceives the horizontal component of the earth's magnetic field. The FDU-70 outputs generated are proportional to the sine and cosine of the aircraft magnetic heading angle. The cosine and sine signals generated by two coils are perpendicular to each other in the horizontal plane. The processing circuits that convert FDU-70 flux measurements into heading data which can be found in the attitude heading computer or directional gyro system.

The FDU-70 unit has a round mounting flange but variations are available with a pendant mounting cable mating connector kit, panel mount mating connector kit, or no mating connector kits depending on the part number. The FDU-70 is 4.76 inches in length, 4.76 inches wide, 2.69 inches in height and weighs 0.9 pounds.