The Vertical Card Magnetic Compass The floating magnet type of compass not only has all the  errors just described, but also lends itself to confused reading.  It is easy to begin a turn in the wrong direction because its card  appears backward. East is on what the pilot would expect to be  the west side. The vertical card magnetic compass eliminates  some of the errors and confusion. The dial of this compass  is graduated with letters representing the cardinal directions,  numbers every 30°, and marks every 5°. The dial is rotated by  a set of gears from the shaft-mounted magnet, and the nose  of the symbolic airplane on the instrument glass represents  the lubber line for reading the heading of the aircraft from  the dial. Eddy currents induced into an aluminum-damping  cup damp oscillation of the magnet.  [Figure 5-22] As mentioned earlier, the lines of flux in the Earth’s magnetic  field have two basic characteristics: a magnet aligns with  these lines, and an electrical current is induced, or generated,  in any wire crossed by them. The flux gate compass that drives slaved gyros uses the  characteristic of current induction. The flux valve is a small,  segmented ring, like the one in  Figure 5-23 , made of soft iron  that readily accepts lines of magnetic flux. An electrical coil  is wound around each of the three legs to accept the current  induced in this ring by the Earth’s magnetic field. A coil  wound around the iron spacer in the center of the frame has  400-Hz alternating current (A.C.) flowing through it. During  the times when this current reaches its peak, twice during each  cycle, there is so much magnetism produced by this coil that  the frame cannot accept the lines of flux from the Earth’s field. But as the current reverses between the peaks, it demagnetizes  the frame so it can accept the flux from the Earth’s field. As  this flux cuts across the windings in the three coils, it causes  current to flow in them. These three coils are connected in  The three coils are connected to three similar but smaller coils  in a synchro inside the instrument case. The synchro rotates  the dial of a radio magnetic indicator (RMI) or a horizontal  situation indicator (HSI). Remote indicating compasses were developed to compensate  for the errors and limitations of the older type of heading  indicators. The two panel-mounted components of a typical  The Flux Gate Compass System Remote Indicating Compass Figure 3-22. Figure 5-22.  Vertical card magnetic compass. Figure 3-24. The current in each of the three pickup coils Figure 5-24. The current in each of the three pickup coils changes  with the heading of the aircraft. Figure 3-23. The soft iron frame of the flux valve accepts the flux from the Earth’s magnetic field each time the current in the  center coil reverse.This flux causes current to flow in the three  Figure5-23. The soft iron frame of the flux valve accepts the flux from  the Earth’s magnetic field each time the current in the center coil  reverses. This flux causes current to flow in the three pickup coils. picked coils. such a way that the current flowing in them changes as the  heading of the aircraft changes.  [Figure 5-24] 5-15 N  W  S  E  33  30  24  21  15  12  6  3 