11Remember the iron filings experiment? Navigation 11Remember the iron filings experiment?The filings show the magnetic field---(Lines of Magnetic Flux)
12Navigation 11 Well the earth has a magnetic field too The bad news is the magnetic North pole is not exactly at the geographic North pole (True North).This means the compass does not align itself with true North.
13Navigation 11The compass attempts to align itself with the magnetic field and therefore Magnetic NorthThe difference between true North(°T) and Magnetic North(°M) is called Variation
14Navigation 11How much Variation depends on your location on the earths surfaceIn the UK variation is less than 5°, in some parts of the world it is as high as 40°UKIsogonals are lines joining places with equal variation. This chart shows World wide Isogonals for the year 2000.
15Navigation 11The Earths magnetic Field is moving, and so are the earths magnetic PolesEdition 28Shift of the 3½° Isogonal, in 5 editions of the 1:500000chart.(30 months)Edition 33
16Navigation 11We need to convert our measurements on the chart (bearings) into something meaningful on our compass.Magnetic Variation is given as either East or West of True North.In the exam you will probably be given variation as 5°West.
17Navigation 11 Variation West magnetic Best True North Desired Heading Magnetic North035°(T)+5°=040°(M)035°(T)Variation 5°WComparing the magnetic and true bearing, the magnetic is larger—hence the rhyme
18Navigation 11 Variation East magnetic Least True North Desired Heading Magnetic North035°(T)-5°=030°(M)035°(T)Variation 5°WComparing the magnetic and true bearing, the magnetic bearing is smaller
19Navigation 11The lines of longitude on the chart always pass through True North.The compass always tries to align with Magnetic NorthSo we draw a line on the chart, measure the angle, and then convert it into a compass bearing---then the compass becomes useful.
20Navigation 11 °T variation °M Fill in the Blanks— Variation west magnetic best, Variation east magnetic least°Tvariation°M145°5°W??°349°16°E3°E235°12 ° W023°098°1°W157°6°E299°4°E340°005°8°W085°4°W9°E195°10°E288°
21Navigation 11 °T variation °M Fill in the Blanks 145° 5°W 150° 349° 333°232°3°E235°011°12 ° W023°098°1°W099°157°162°293°6°E299°344°4°E340°005°8°W013°085°4°W089°204°9°E195°298°10°E288°
22Navigation 11 Compass deviation The angular difference between where the compass actually points and magnetic North.Deviation is typically caused by metal materials within the airframe, or metallic objects placed near the compass.You do not need to be able to calculate compass north (deviation west compass best)
23Navigation 11 Cadburys Dairy Milk—Very Tasty Compass North Deviation Magnetic northVariationTrue NorthThe difference between Compass north and Magnetic North is Deviation.The difference between Magnetic north and True North is Variation
24Acceleration and turning Errors Navigation 11Acceleration and turning ErrorsA compass is unreliable in any thing but straight and level flight.To understand this we need to revisit the Earths Magnetic Field
25Navigation 11 Earths magnetic field The only place the magnetic field is parallel with the surface is at the magnetic equator.The dip angle increases as we move towards the poles.
26Navigation 11The compass aligns itself with the magnetic field, and is therefore not horizontal in our latitudes.Magnetic North PoleIncreasing dip angle as we move towards the pole
27Navigation 11 At the magnetic Equator Lines of Magnetic Flux Centre of gravityPivot
28Navigation 11 At the mid latitudes Compass no longer horizontal Centre of gravityPivotLines of Magnetic Flux
29Navigation 11Plan viewNorth seeking polePivot no longer at the CofG
31Acceleration error heading North South is Zero Navigation 11Decelerate NorthSteady state heading NorthAccelerate NorthReading 360°Reading 360°Reading 360°Acceleration error heading North South is Zero