ATPL General Navigation - Class 5: Direction.

Summary

In this educational video, Grant explores the complexities of navigation using a compass, which isn't as straightforward as it seems. He explains the Earth's magnetic field, generated by the molten iron core, and its misalignment with the geographic poles. The video delves into concepts like magnetic variation, deviation, and the impact of wind on navigation. Grant teaches viewers how to convert between magnetic and true north and highlights the importance of compass calibration, especially in aviation, to account for metal and electrical components that can affect compass readings. The summary also touches on the difference between heading and track, and the necessity of wind correction angles to maintain course.

Takeaways

• 🧭 A compass points towards the magnetic north pole, not the true geographic North Pole.
• 🌐 The Earth's magnetic field is generated by its molten iron core, which is offset and changes over time.
• 🔍 The magnetic field's offset causes a difference between magnetic and true north, known as variation.
• 🌀 At the magnetic equator, the compass would not point downwards but would spin flat due to the lack of vertical force.
• 📍 Close to the magnetic poles, the magnetic dip can be so high that the compass becomes unusable.
• 🔄 The horizontal component of the magnetic force is called directive force, which spins the compass, while the vertical component is known as magnetic dip.
• ⚖️ Variation can be either east or west, and it affects the accuracy of a compass reading.
• 🔄 To convert between magnetic and true north, use the equation: Magnetic + Variation = True.
• 🛫 Aircraft generate their own magnetic fields, causing an error in compass readings known as deviation.
• 🔄 Deviation is corrected using the equation: Compass + Deviation = Magnetic, with similar rules for east and west as variation.
• 🚀 For accurate navigation, pilots must account for both variation and deviation, as well as wind effects on heading and track.

Q & A

Why doesn't the Earth's magnetic field align perfectly with its geographic poles?

The Earth's magnetic field doesn't align perfectly with its geographic poles because it is formed mainly by the molten iron core at the center of the Earth, which is liquid and has a life of its own, causing the magnetic field to be slightly offset and change year to year, day to day.

What happens to a compass if you stand directly on the magnetic north pole?

If you stand directly on top of the magnetic north pole, the compass would be pulled all the way down and try to stand up vertically because the magnetic force is directly beneath it.

What is the term for the imaginary line at the halfway point of Earth's magnetic field?

The imaginary line at the halfway point of Earth's magnetic field is called the magnetic equator.

What are the two components of the magnetic force experienced by a compass?

The two components of the magnetic force experienced by a compass are the horizontal component, known as the directive force, which spins the compass around, and the vertical component, known as magnetic dip.

Why can't a compass be used near the magnetic north pole?

A compass can't be used near the magnetic north pole because the horizontal component of the magnetic force becomes so weak and the magnetic dip is so high that the compass becomes unusable and can't spin effectively.

What is the difference between magnetic north and true north called?

The difference between magnetic north and true north is called variation.

What is the significance of the term 'variation' in navigation using a compass?

Variation signifies the difference between magnetic north and true north. It is crucial for accurate navigation as it accounts for the inaccuracy when using a compass due to the misalignment of the true and magnetic north poles.

How can you convert between magnetic and true north?

You can convert between magnetic and true north using the equation: Magnetic + Variation = True. Remember that east is positive and west is negative.

What is deviation in the context of aircraft navigation?

Deviation refers to the error in the compass readings caused by the aircraft's own magnetic fields due to its metal structure and electric components. It is corrected through a process called compass swinging.

How is the error check for variation and deviation performed?

The error check for variation and deviation can be performed using the phrase 'if the variation is east, the magnetic will be least; if the variation is west, the magnetic will be best' and similarly for deviation.

What is the difference between heading and track in aircraft navigation?

Heading refers to the direction in which the aircraft's nose is pointed, while track is the actual path the aircraft is following. The difference between the two is due to factors like wind, which can cause the aircraft to drift off course unless corrected.

How can you remember the order of operations for converting between compass, magnetic, and true north?

You can remember the order of operations using the acronym 'CDMVT', standing for Compass, Deviation, Magnetic, Variation, and True, which can be associated with 'Cadbury's Dairy Milk', a popular chocolate bar in the UK.