KI-13K

Magnetic indication principle of the KI-13K

The compass works through the interaction of permanent magnets with the Earth’s magnetic field. The magnetic system is attached to the compass card, and the card rotates inside the liquid-filled bowl. A fixed lubber line on the compass glass shows the aircraft heading against the rotating card. This layout is different from many handheld compasses: the pilot reads the course number aligned with the aircraft’s forward direction. The instrument is simple in principle, but it must be installed and compensated correctly to give usable heading information in the cockpit.

Liquid damping in the KI-13K compass

The KI-13K compass bowl is filled with compass liquid, typically ligroin or a special alcohol-based solution depending on execution and maintenance documentation. The liquid damps oscillations of the compass card during aircraft vibration, maneuvering and turbulence. Without damping, the card would swing too much and the pilot would have difficulty reading a stable course. The liquid level and condition matter during inspection. Bubbles, leakage, contamination or sluggish movement of the card can make the compass difficult to read or unsuitable for aircraft use.

Deviation compensation on the KI-13K

Aircraft structures, wiring, electrical equipment and steel parts can distort the magnetic field around the cockpit. For this reason, the KI-13K includes a deviation compensation device with small compensating magnets installed in the lower part of the housing. These magnets are adjusted during compass compensation so that the remaining deviation is reduced to acceptable values. The compass should not be treated as accurate simply because it points north. Its final accuracy depends on the installation point, nearby magnetic influences and proper deviation adjustment on the aircraft.

Installation area of the KI-13K compass

The KI-13K is usually mounted on the cockpit windshield frame, on the central glazing post, or on an upper cockpit panel where the crew can read it directly. The instrument must be aligned with the longitudinal axis of the aircraft. On aircraft such as An-2, An-24, An-26, Yak-18T, Yak-40, Yak-52, Tu-134, Il-76, Mi-2, Mi-8 and Ka-26, installation details depend on cockpit layout and aircraft documentation. The mounting position is chosen so that the compass remains visible and is affected as little as possible by local magnetic interference.

KI-13K execution for red cockpit lighting

The “K” index identifies an execution without permanent radioactive luminous compound. The scale is adapted for use with red cockpit lighting, which is important for night operation and for aircraft where radioactive luminous materials are not permitted or are being replaced. This should be checked when ordering, because outwardly similar KI-13 series compasses can differ by scale marking, lighting execution, compensation arrangement and documentation. For supply, the exact designation KI-13K should be used, not just “KI-13 compass”.

Inspection and supply of KI-13K

During maintenance, the KI-13K is checked for card freedom, damping time, liquid condition, absence of leaks, glass condition, compensation device condition, mounting alignment and lighting circuit serviceability. The compass should return smoothly and should not stick when the aircraft changes attitude within the specified limits. For aviation supply, it is useful to confirm the passport or label, condition, storage history, lighting voltage, compass liquid condition and whether deviation compensation hardware is present. A visually clean compass may still require inspection before installation.