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PostPosted: Tue Sep 06, 2016 4:51 am 
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Hi everyone,
I noticed on smaller planes, especially warbirds, the artificial horizon gauge really moves about when you start the engine and also when the engine is off it always seems to be at some angle like 50 or so degrees ? I know it uses gyros (or at least I think it does). Just wondering how come it moves around so much during start up and when engines are off it also goes on it's side.

Thank you in advance

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PostPosted: Tue Sep 06, 2016 5:50 am 
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This is normal behavior for this instrument.

Cheers Chris


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PostPosted: Tue Sep 06, 2016 6:53 am 
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If you've ever had a top-toy, then you should be familiar with this behavior. The sensitive part of the artificial gyro is a gyroscope which is, definitely, an example of a top.


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PostPosted: Wed Sep 07, 2016 4:11 am 
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ilya1502 wrote:
If you've ever had a top-toy, then you should be familiar with this behavior. The sensitive part of the artificial gyro is a gyroscope which is, definitely, an example of a top.


Ummmm yes sort of. So when everything is going the artificial hoz is straight then ?

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PostPosted: Wed Sep 07, 2016 4:13 am 
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Yep.... and that is one of the instrument checks before takeoff.

(Unless you are on non-level ground..then it will show your angle of "lean")

D

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PostPosted: Wed Sep 07, 2016 6:45 am 
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The artificial horizon contains special air vanes within it to automatically align itself vertically with respect to the force of gravity. A gyroscope needs to reach a certain RPM in order to become stable in space. I believe the gyros in an AI are turning at nearly 15-20K RPM at their normal operating speed.

The gyros will tumble about when initially starting to spin up until they become stable in space once they reach a sufficient RPM to somewhat stabilize. A stabilized AI will also tumble out of control if it reaches the limits of its gimbals due to the aircraft being put in an unusual attitude outside of the gimbal travel limits. This can last several minutes while the AI slowly corrects. The stability of the AI at a high RPM is what makes it take longer to recover from tumbling in flight vs when when the aircraft is initially started and the AI is just spinning up. Most AI gyros do not have full freedom of their gimbals to simplify construction.

http://www.experimentalaircraft.info/ar ... cators.php

See in this thread for an illustration showing the operation of the vanes
http://aviation.stackexchange.com/quest ... t-accurate

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PostPosted: Wed Sep 07, 2016 3:26 pm 
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Oracle427 wrote:
The artificial horizon contains special air vanes within it to automatically align itself vertically with respect to the force of gravity. A gyroscope needs to reach a certain RPM in order to become stable in space. I believe the gyros in an AI are turning at nearly 15-20K RPM at their normal operating speed.

The gyros will tumble about when initially starting to spin up until they become stable in space once they reach a sufficient RPM to somewhat stabilize. A stabilized AI will also tumble out of control if it reaches the limits of its gimbals due to the aircraft being put in an unusual attitude outside of the gimbal travel limits. This can last several minutes while the AI slowly corrects. The stability of the AI at a high RPM is what makes it take longer to recover from tumbling in flight vs when when the aircraft is initially started and the AI is just spinning up. Most AI gyros do not have full freedom of their gimbals to simplify construction.

http://www.experimentalaircraft.info/ar ... cators.php

See in this thread for an illustration showing the operation of the vanes
http://aviation.stackexchange.com/quest ... t-accurate


Perfect. Thank you s much Oracle :D

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