The Drunk Compass

The trusty compass. That tool that is so important to hikers and aviators alike. Simply check it to determine north from south, and away you go. Right? WRONG!

It turns out this simple looking, helpful little instrument is actually the most complicated damn piece of equipment in the aircraft. Presumably, the stupid little floating ball should point towards the direction you are pointed, since the earth magically (and magnetically) pulls the north end...you guess it, north. However, it turns out that there are quite a few ways that the compass actually is out to fool you. And most of this is due to the fact that the earth’s magnetic poles are not actually located at the north and South Pole, but actually a couple hundred miles below them in the earths crust.

To give you an idea of how the compass really does hate pilots, take this example: You are flying along with no electrical power and your vacuum pumps have failed. Unlikely, but it would in fact require you to rely solely on your magnetic compass. You are in the clouds and on a easterly heading, but ATC wants you to turn to your left 270 degrees until you reach a southerly heading so they can get you around a nasty thunderstorm. You start your left turn, and the compass start turning...but the wrong way!! It is showing you turning towards your right. Quickly you access that it must be a mistake, so you continue along and sure enough it starts back the other way, and slowly catches up with your rate of turn. As you pass by the West heading on your compass, still in your turn, the compass seems to slow to a stop for a good few seconds. Then it leaps forward and almost faster than you can react, and it passes the southerly heading that you were aiming for. You level out thinking you have overshot your goal, and watch for the compass to settle out. Then it starts to turn on its own back past south and towards west. It turns out you are almost 30 degrees short of making it all the way to south! Stupid compass.

There are actually three ways that the compass tries to screw you up when you are flying:
-First, it is only accurate in straight and level, unaccelerated flight with no turbulence.

-Second. it often indicates turns in the incorrect directions for the first few seconds of the turn.

-And third, in order to stop directly on a northerly (271 degrees to 89 degrees) or a southerly (91 degrees to 269 degrees) heading, you need to compensate for the "turning error of the compass" at your particular latitude.

Now mind you all of this is going on during a time when you have lost all the major equipment on board and you are in a very nervous state of mind. Hence, this being a situation that I never want to be in, and am already tired of practicing for!!