How Magnets Help Us Navigate The Skies
The History of the Compass
The magnetic compass dates back to the Chinese Han Dynasty in 206 BC and relied on a naturally occurring magnetized rock whose iron ore strangely demonstrated magnetic properties. This rock was later known as Lodestone after the Greeks’ independent discovery in Magnesia during the 6th Century BC. The Greek “discovery” happened accidentally when iron studs in a shepherd’s sandals suddenly stuck to the ground, rendering him speechless and perhaps incredibly superstitious! It was later denounced from being an act of God and magnetism was thereafter rediscovered
In the search for more accurate compasses, iron needles were magnetised by striking them with Lodestone which led to the compasses we all know and recognise today. Remarkably, the same basic principles still aid pilots all over the world and without them – well, they’d be pretty lost.
How does an aircraft’s magnetic compass work?
In their official Instrument Flying Handbook, the Federal Aviation Administration refers to the Earth as a “huge magnet, spinning in space”. They use this example because the Earth is surrounded by a magnetic field called the magnetic flux. This is best described as magnetic lines stretching across Earth and influences certain types of rocks, like Lodestone. The magnetised needle of a compass aligns with the Earth’s magnetic flux which explains why compasses point North at all times.
The compases built in today’s aircraft consist of a metal base that holds a float and a magnetic bar. The float becomes magnetised and feely spins 360 degrees in the body of water indicating its present direction which is accompanied with a lubber line at the front of the aircraft. The lubber line is a fixed line on a compass binnacle or, alternatively, on a radar PPI (plan position indicator) display and points towards the front of the aircraft thus corresponding with the craft’s centerline; accurately demonstrating the pilot’s current direction of travel.
The simple process of the compass has paved the way for truly revolutionary points in our history – from the Age of Exploration all the way to more recent events like the two world wars when our pilots flew across Europe and the Pacificl. This all happened from the single event in 600BC when the shepherd’s feet ‘mysteriously’ stuck to the floor – fascinating!
