Original, complete and excellent condition WWII German Luftwaffe Orterkompass (Observer compass) type Lkf 5b Franz Fl.23203-1.
Designation: location compass
Requirement mark: Fl.23203-1
Type: Lkf 5 b "Franz"
Manufacturer: Askania-Werke AG, Berlin
Year of construction: 1937
Note: Variant without luminous material on compass rose and control line
Installed in: e.g. Junkers G23, G24, W33, W34
The liquid-filled magnetic compass was always installed in such a way that the internal compass rose could rotate and swing freely in order to ensure good and precise vertical readability.
The principle of the magnetic compass is based on magnetic sticks, which are firmly connected to the course rose and align themselves with the earth's magnetic field. Several magnets are used at the same time to increase the magnetic straightening force. In order to dampen the shocks and vibrations occurring during flight operations, the course rose was stored in a pressure-tight housing (compass chamber) filled with liquid.
There are different liquids for filling (e.g. Tulol), which in all cases
Must be permanently transparent and thin, and, due to the chemical composition, must compensate for the strong temperature fluctuations that occur. The liquid must be absolutely frost-resistant (at least down to -50 °), as very low temperatures prevail at high altitudes. To compensate for the change in volume of the compass fluid in the event of large temperature differences, the compass tank is connected to the so-called "compensation vessel", which is located in the rear part of the housing. The compensation vessel consists of several interconnected membrane boxes, which can "inflate" when the volume increases or "contract" when the volume of the compass fluid decreases, similar to an accordion.
The compass case is made of Bakelite. The glass pane at the front is held in place by an aluminum flange (ring). The Fl number, the manufacturer (also coded) and the serial number are usually noted on the flange.
The magnetic compass is a real navigation instrument and allows the pilot to keep a certain direction of flight.
The compasses used for navigation use the earth's magnetic field to determine direction. But since the magnetic poles do not coincide with the geographic one, there is a difference between the compass north display and geographic north, which is known as magnetic declination. This magnetic declination differs from place to place and changes its value over the years. It is therefore particularly important to take into account the deviations that occur when using magnetic compasses.
In addition to the magnetic deflection mentioned, there are also distractions caused by magnetic interference fields in the aircraft itself. These interference fields are caused, for example, in existing steel components, ignition magnets and electrical devices. This deflection, called deviation, has to be compensated for by attaching small magnetic bars. The so-called compensation is used for this. In practice, this compensation is seldom completely successful, so that the residual deflection must be specified on a deviation table in order to undertake a corresponding correction of the compass reading. The deviation table is only associated with the respective tested magnetic compass.
The most important component of the magnetic compass is the magnet system. The compass rose, on which the graduation (0-360 °) is located, is connected to this. A control line is affixed to the window of the compass housing. When the course changes, the housing and thus the control line rotates around the compass rose, thereby indicating the change in direction.
In order to achieve a steady compass display in spite of the constant changes in position and accelerations that occur, the movements of the magnet system (compass rose) must be dampened by means of a "damping fluid". A liquid consisting of a mixture of gasoline and mineral oil is usually used as a dampening agent.