So... I'm a little drunk

2-Bit Speed

2-Bit Speed

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2-Bit Speed
Why does a gyro compass need correction for procession but not a gyro artificial horizon? Or does the gyro AH?
 
The ball in the AI probably does precess, but it's not giving you directional information so you probably don't notice it.
 
Because planet drift rate (15deg/hr) is information not transmitted to an unslaved DG, hence the need to manually reset with the passage of time. In the case of the attitude indicator, the erection mechanism is also the gravity vector slaving, via pneumatic pendulous vanes always referencing the the gyro to [gravity]vertical. It's effectively a slaved gyro in the way a DG is not.
 
ab6765630000ba8a2ba6b095dda9fb7d656f03d1.jpeg

Just to translate from hindsight2020© to English in case anyone missed it:
The AI does precess, but is constantly being corrected by gravity.
 
Last edited:
hindsight2020 said:
Because planet drift rate (15deg/hr) is information not transmitted to an unslaved DG, hence the need to manually reset with the passage of time. In the case of the attitude indicator, the erection mechanism is also the gravity vector slaving, via pneumatic pendulous vanes always referencing the the gyro to [gravity]vertical. It's effectively a slaved gyro in the way a DG is not.
Click to expand...
You seem well versed in this so color me surprised that you neglected to even mention the effect that the turbo encabulator has on operation of the erection mechanism.
 
It would seem I have some catching up to do to keep up with this conversation.
 
2-Bit Speed said:
Why does a gyro compass need correction for procession but not a gyro artificial horizon? Or does the gyro AH?
Click to expand...

Precession not procession.

See the figure below for a pneumatic AI. The weighted device at the bottom of the gyro allows air to exhaust equally from four ports. When the gyro precesses, ports are opened or closed, letting the moving air apply a force opposed to the precession and thus keeping the gyro upright.

1744425198850.png
 
Half Fast said:
Precession not procession.

See the figure below for a pneumatic AI. The weighted device at the bottom of the gyro allows air to exhaust equally from four ports. When the gyro precesses, ports are opened or closed, letting the moving air apply a force opposed to the precession and thus keeping the gyro upright.

View attachment 139779
Click to expand...
Note that because of the resultant forces in a coordinated turn, the vanes will actually process the gyro slightly, maximum at 180 degrees of then, and then decreasing for the next 180.
 
Could be wrong, but believe the AI self corrects the drift because it gradually adjusts to gravity/down being level. Which should work unless you fly in a circle or crooked for a long time. Again, could be wrong.

To test, sit in the airplane with the AI spun up, on the ground, while something holds one wheel up so you're at a 15 degree or so tilt for 30 minutes, and let us know what happens.

Haven't had a drink all day, but I am tired, so I'll use that as an excuse.
 
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