Bad Attitude!

A couple of weeks back I come across the following video staring Dave AKA DMurphy25 on Late Nite, in the first minute and a half he talks about gyroscopes and artificial horizons (attitude Indicators as they are called in the aerospace industry). This got my interest, not in the rest of the video but in gyroscopes and artificial horizons.

 

I paused the video at that point and went to google attitude Indicators. I knew what they where and that they had a gyro in them but hadn't put much thought in to how they worked.

“The Attitude Indicator shows rotation about both the longitudinal axis to indicate the degree of bank, and about the lateral axis to indicate pitch (nose up, level or nose down). It utilizes the rigidity characteristic of the gyro. It is gimballed to permit rotation about the lateral axis indicating pitch attitude, and about the longitudinal axis to indicate roll attitude. Once powered up, the indicator is maintain in a fixed position no matter what the aircraft attitude may be.” www.pilotfriend.com

After learning a little more about attitude Indicators I found DMurphy25 to be correct in that they are mechanical (some of the newer ones are more electronic but this is more for digital displays and autopilots) I find it disturbing that the pilot didn't now this. The pilot should know the plains instruments and the false readings some can give in certain instances.

A gyro will maintain its orientation in space this makes it very useful as an artificial horizons, however a gyro can “drift” off its original position if and outside for acts up on it. Procession is when a out side force pushes on the gyro and the force is transferred 90° round the gyros axis. You can test this your self, take a bicycle wheel and hold it upright by its axle so it can spin freely. now have someone spin it nice and fast (preferably a friend as strangers in the street may look at you oddly) now try to turn the wheel on its side you will feel it resits and try to push you round to your left or right. The mechanism that houses the gyro in an attitude Indicator will inevitably produce a small amount of friction acting on the gyro causing procession and over time the attitude Indicator will begin to give a false reading this is called mechanical drift. There is a second kind of drift called apparent drift this is where the plains axis changes as it follows the curvature of the earth but the gyro dose its job and holds its original orientation. (click hear to see a beautiful 1960 Navy Aviation Training Film explaining all this) 

So DMurphy25 is correct again, pilots don't see this "Apparent Drift" but why don't they? Mechanical drift would be a problem no matter what shape earth is, both mechanical and apparent drift are problematic to a globe traveller. Mechanical drift would need to be corrected for and engineers have come up with a couple of ways to correct for drift. they are called attitude arrestors. the following video explains it all far better then I can.

so dose an attitude Indicator prove or disprove a flat Earth?
No, with the attitude arrestor attached and working gravity will keep it pointing to the ground weather you are flying over a globe or a flat earth. The only way to detect the change caused buy flying over the curvature of a globe earth is with a straight up none correcting gyro.

I have to say that the attitude Indicator is busted as a proof for the flat Earth. but experiments with a gyroscope on a plain are worth looking in to. (providing you don't spook airport security or you get proper permission first)