Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM The Compass The ancients recognized the pole star as being a constant reference for determining direction. The Norsemen in the 11th century used a needle of magnetic iron inserted in a straw and floated on water to point to the pole star. Petrus Peregrinus de Maricourt invented the pivoted floating compass with lubberline and sight for bearing. The modern compass is little more than one hundred years old.The compass card, due to wind rose origins is older than the magnetic needle. Names of the cardinal compass points are from the ancient terms for wind direction. Variation was understood by 1800 as a problem. Edmond Halley at end of 17th century mapped lines of variation and drew isogonic lines (lines of variation) on his maps. George Graham showed that variation was subject to diurnal (seasonal) changes with variation being less in winter. John Smith wrote about deviation in 1627 by John Smith. He saw it as a problem encountered through use of metal nails in his compass box. Captain. Mathew Flinders in 1801-2 found way to correct by use of "Flinder's Bars as did Lord Kelvin through use of Kelvin spheres. Placement of soft iron spheres at sides of compass could be used to correct deviation. The magnetic compass depends on the horizontal component of the earths' magnetic field. The directional properties of the lodestone were known to early man. The term magnet comes from the name of a region in southern Europe which was a major source for lodestone. The development of the magnet grew form a floating needle in a straw, to the needle in a cork, a pivoted needle, the pivoted card, the pivoted card in a bowl, to the use of gimbals, and finally the liquid chamber with a pivoted card. Compasses were in use as early as the 12th century but their operation was imperfect and not fully understood. About 18090 Mathew Flinders discovered a solution to the problem of local attraction. Deviation as used in aviation. Flinder's Bars, large masses of unmagnetized iron, are universally used on ships. In 1838 Sir G. B. Airy used magnets and iron to neutralize effects of iron ships. The initial dry card compass was developed by Lord Kelvin who determined that a cards steadiness depended on the natural period of vibration of card and needle. A light card with a heavy rim was suspended by a pyramid of threads to a central pivot point. This produced a steady card. The use of a liquid float chamber with the buoyancy of the magnet and card only slightly less than weight to reduce fraction. The liquid has a dampening effect as well. The development of the gyro compass began in 1851 when Leon Foucault used suspended cannon shot on a long wire pendulum to show the rotation of the earth as well as the inertia of the free swinging ball. By 1852 he had created the gyroscope but had trouble applying continuous power. By 1900 the electric gyroscope was invented by both Elmer A. Sperry and Anschutz-Kampfe of Germany. By 1911 gyro compasses were in use soon to be followed by gyro repeaters (selysn(sp) units) flux-gate compasses and gyro pilots.. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM