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An aircraft's compass reads 002°. The deviation card shows 1°W on northerly headings and the variation is 5°W. What is the aircraft's true heading?

• A
008°
• B
006°
• C
358°
• D
356°

True Direction, the North Pole is taken as a geographic reference and is assigned an angular value of 000º T or 360º T.
In most light aircraft True directions aren’t the most precise because the airplanes aren’t equipped with instruments that will align itself with the True North Pole.

The primary source for directions inside a cockpit is the magnetic compass and he will align itself with the Magnetic North Pole and not with the True North Pole, those are not co-located.

Magnetic Direction, have as reference the Magnetic North Pole and is assigned an angular value of 000º M or 360º M.
Variation is the angle between the True and Magnetic North and is assigned in degrees East or West of the True North.

• If the Magnetic North is west of the True North, westerly variation, the magnetic direction will have a higher angular value than the true direction.
• If the Magnetic North is east of the True North, easterly variation, the magnetic direction will have a lower angular value than the true direction.
Variation (-) West – Magnetic Best

Variation (+) East – Magnetic Least

The utility of a magnetic compass on the aircraft will depend on the accuracy of its response to the magnetic field of the earth.
The metallic structure of the airplane, its engine and equipment can affect the accuracy of the compass, an effect called the compass deviation.
Compass deviation is defined by the number of degrees by which unwanted magnetic fields deflect the compass from magnetic north indication (desired indication).

Deviation (-) West – Compass Best

Deviation (+) East – Compass Least

The relationship between the different directions can be expressed by the following table:

 True Heading (T) Variation (V) Magnetic Heading (M) Deviation (D) Compass Heading (C) 356º 5ºW 001º 1ºW 002º
Note: The TVMDC table can be used to relate both Heading directions or track directions.

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• United Kingdom
• France