(no subject)

[camwyn]

Had flight school on Saturday. Hour and a half of ground training, forty-five minutes or so in the sky. I need to get caught up on the ground training front; we're a little behind compared to what the instructor has me doing in the air. Not that we're doing anything all that fancy in the air yet. The instructor has me practicing landing techniques, which are kind of tricky, and I'm still not entirely sure how much of the stuff we do during the takeoff process is him and how much is me. I'm still trying to get the hang of hovering, too, although this week there was a point during stationary hover when the instructor took both hands off the controls and waved them in the air because I was doing well enough. Didn't last long, but still.

One of the things we covered in ground training was magnetic navigation, and all the specific ways you have to compensate for the compass's failings. Some of them are individual to a given helicopter, which is why any bird you get into will have a compass card indicating "if you wanna plot a zero degree heading, you'll have to aim for one degrees on the compass; ninety degree headings need eighty-nine, etc". Some of them are just because the magnetic north pole is about thirteen hundred miles from the geographic north pole, plus it moves, because otherwise it would be too easy. The farther east or west you are from an imaginary line drawn through Chicago and St. Louis (at the moment- like I said, the damn thing moves), the more you have to compensate when taking a compass reading.

Also the pole is beneath the surface of the Earth, a thing which I do not remember learning from school but do remember learning from H. P. Lovecraft, since "The Dunwich Horror" mentioned 'the hidden inner city at the magnetic pole'. This causes more compass screwiness in the form of magnetic dip, since it pulls the needle in different directions during turns and changes in speed- when a helicopter accelerates it tilts its nose down and its tail up and the compass needle suddenly goes "OH HEY YOU'RE GOING NORTH NOW" even if you're headed on a perfectly straight east-west course. Which would be fun enough in itself, but if you're heading northward and turn west or east, your compass needle is gonna lag behind, so don't try making a ninety-degree turn based solely on your compass readings because you'll wind up turning way too far. Heading south and making a turn, the needle overshoots what you've already done, although it falls back eventually. My instructor, who is from Tennessee, told me the easiest way to remember this was 'South Leads, North Lags', though of course that only works in the northern hemisphere.

It never ceases to amaze me that we jumped-up little monkeys have managed to get as far as we did by following splinters of rock and metal that point at an erratic wiggly arbitrary spot in the ground somewhere most of us will never see.

Comments

[tam_nonlinear]

I honestly didn't know the magnetic pole was underground. I just assumed it was more of an axis than a point. Neat.

The one that gets to me is big maps. Big maps made when people were limited in elevation to buildings made of stone, tall trees, and maybe mountains, if the weather was clear. So we built maps of the world when any one given person could probably see something like twenty miles at a given time, under good conditions, without trees in the way. We crossed oceans like that. Seriously, humans found Hawaii, based on generations of people in tiny little boats saying 'Hey, I wonder what's thataway."

[leeshajoy]

I can't remember which episode it was in, but on QI at some point, Stephen Fry showed off a specialized map used for navigation by Pacific Islanders. It was a representation of the ocean currents around a particular island... which a sailor would check by dipping his scrotum in the water. Not even kidding.