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Old 05-18-2018, 07:03 PM   #1
Sanatog
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Question ADI bounce

Im just getting into the F-5E and im really enjoying the module, but i have come across a strange issue.

I can't seem to find any mention of it in the forums, or the manual so I'm wondering if i am missing something obvious here.

After a Cold start and getting lined up on the runway with the ADI and the Standby ADI set to the horizontal I throttle up to 90% and release the breaks. As soon as i do that the ADI bounces down by around 10 degrees. The standby ADI is fine and doesn't move.

Any help gratefully received.
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Old 05-18-2018, 09:29 PM   #2
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Yeah. The ADI is not so stable. Not really sure if it's supposed to be this way or not. Guess only a real F-5 pilot can tell.
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Old 05-19-2018, 11:58 AM   #3
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Thanks, glad its not just me!

I could understand the bounce during high G manoeuvring, i was just really surprised it happens on take off as well.
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Old 09-30-2018, 03:48 PM   #4
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The ADI showing a wrong pitch attitude even after doing only a quick traffic pattern is still there.
Can BST/ED confirm this bug?
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Old 11-09-2018, 08:45 AM   #5
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Quote:
Originally Posted by bbrz View Post
The ADI showing a wrong pitch attitude even after doing only a quick traffic pattern is still there.
Can BST/ED confirm this bug?
Anyone?

The only situation when the Fast erect button should be used (according to -1 manual) is power failure in flight. Not 2 minutes of traffic pattern.

Also the fast erect moves HSI card to the north, which is incorrect. HSI should use its own Fast Slave switch.
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Last edited by some1; 11-09-2018 at 02:59 PM.
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Old 11-09-2018, 02:17 PM   #6
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Quote:
Originally Posted by some1 View Post
Anyone?

The only situation when the Fast erect button should be used (according to -1 manual) is power failure in flight. Not 2 minutes of traffic pattern.

Also the fast erect moves HSI card to the north, which is incorrect. HSI should use it's own Fast Slave switch.
I have this issue not only with the F-5, but with the Spitfire and P-51 as well.
IMO this is a system-wide problem, not specific to the F-5. And yes, like many things it's been like this for years..
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Old 11-09-2018, 02:58 PM   #7
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In Spitifire and P-51 it simulates the old vacuum gyros which were not very reliable or accurate after several hard maneouvers and couldn't be used during aerobatics. That's why they have the "cage" button to prevent them from tumbling.

But the one in F-5 is much newer and shouldn't have such problems.
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Old 11-09-2018, 08:42 PM   #8
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Quote:
But the one in F-5 is much newer and shouldn't have such problems.
'Much newer' means nothing here. A quote from Wikipedia:

"Older AIs were limited in the amount of pitch or roll that they would tolerate. Exceeding these limits would cause the gyro to tumble as the gyro housing contacted the gimbals, causing a precession force. Preventing this required a caging mechanism to lock the gyro if the pitch exceed 60° and the roll exceeded 100°. Modern AIs don't have this limitation and don't require a caging mechanism."

So it's NOT about vacuum or electricity, it's just the mech the ADI was built on. Which might not have been that good just yet back in the day when the F-5E was introduced.
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Last edited by msalama; 11-09-2018 at 08:51 PM.
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Old 11-09-2018, 09:04 PM   #9
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Next time before you quote some random wikipedia article, at least read it fully, because it repeats what I just said.

There is no "Cage" switch on the artificial horizon installed in the F-5, nor there are any pitch limits listed in the manuals. It can be used for full aerobatics. So by that definition F-5 ADI is in the "modern" category.

Vacuum gyros can be less accurate than electric ones, as it is harder to keep them spinning at constant speed all the time, especially during maneouvers. But the F-5 ADI is electric, so again, it is more "modern" than the gauges installed in WWII fighters if you consider the propulsion type.

By the 1960's the tech to make an accurate artificial horizon was pretty much sorted out.
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Old 11-10-2018, 08:31 PM   #10
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Yah, well, it's kinda borked then innit?
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