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Does the artificial horizon work correctly in FlightGear?

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Does the artificial horizon work correctly in FlightGear?

Postby 0303 » Sun Sep 17, 2023 7:54 am

The Artificial Horizon (AH) has two key attributes without which it doesn't work at all:
    a) A gyro provides inertia
    b) A continuous self correction to the gravity vector
The latter (b) continuously corrects the AH if it for any reason, jolt from turbulence, drift, is off in pitch or roll angle. In old classic AI this correction is performed by pendulous vanes. Modern AI's use different technology for the same self corrective purpose (mercury switches).

Old classic AI have built in mechanical stops to protect the mechanism. These typically limits movement to 110 degrees in roll and +- 60 degrees in pitch. When the mechanical stops are hit the AH will "tumble". This happens at every roll or looping.

Film of a real Spitfire with AH tumble at timestamp 17:01 (rolling) and showing self correction 18:05 - 27:00 from 90 degrees roll error at 18:05. Nine minutes ... I've read (see training film last) that vacuum driven AH self corrects at about 4 degrees per minute.


A P-51 AH in a bench, self corrects in 12 seconds.
https://www.reddit.com/r/WWIIplanes/com ... _artifact/

Real Spitfire startup. Watch correction 15 - 43 seconds.

~~~

A certain other simulator, which remain unnamed, with otherwise better graphic and flight model doesn't do this at all which I find very disappointing. Do FlightGear do this right?

Finally an excellent training film describing the AH instrument, old and new.
Last edited by 0303 on Sun Sep 17, 2023 11:31 am, edited 9 times in total.
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Re: Does the artificial horizon work correctly in FlightGear

Postby erik » Sun Sep 17, 2023 8:30 am

Yes, the Artificial Horizon in FlightGear can get disorientated and it takes (a long) time to re-stabilize.

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Re: Does the artificial horizon work correctly in FlightGear

Postby wlbragg » Sun Sep 17, 2023 5:28 pm

Also keep in mind, different aircraft, different equipment. The c172p for example used to have a "lock" button on the AH, that was removed after further research on the model we are simulating that suggested it had no "lock".
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Re: Does the artificial horizon work correctly in FlightGear

Postby david.megginson » Tue Sep 19, 2023 1:58 am

wlbragg wrote in Sun Sep 17, 2023 5:28 pm:Also keep in mind, different aircraft, different equipment. The c172p for example used to have a "lock" button on the AH, that was removed after further research on the model we are simulating that suggested it had no "lock".

By now, most Cessna 172P's will have gone through more than one attitude indicator, so who knows what you'll find on the panel? Some can probably be caged, and others, not. It would be least realistic to have the exact instruments it shipped with >40 years ago. :)
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Re: Does the artificial horizon work correctly in FlightGear

Postby wlbragg » Tue Sep 19, 2023 2:06 am

"Caged" Thanks for that, I couldn't remember the term.

It would be least realistic to have the exact instruments it shipped with >40 years ago

Good point. But ours was hidden in a hanger untouched for the last 35 years. :)
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Re: Does the artificial horizon work correctly in FlightGear

Postby david.megginson » Tue Sep 19, 2023 2:53 am

:) Actually, I based the original 172P on the rental planes used for my primary flight training in in 2002 at the Ottawa Flying Club (that's why FlightGear has that model; I also flew a 172M and a 172R, but most of the time I was in a P).

The interior needs to be a lot shoddier, the carpet should be dirty and threadbare, and several instruments and radios should be placarded U/S.
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Re: Does the artificial horizon work correctly in FlightGear

Postby david.megginson » Tue Sep 19, 2023 11:59 am

"The AI is placarded U/S, but it's not required for day VFR, so suck it up renter and make sure you have the plane back in two hours."

That's one of the reasons I ended up buying a plane.
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Re: Does the artificial horizon work correctly in FlightGear

Postby wkitty42 » Tue Sep 19, 2023 2:03 pm

/me wonders if changing a craft's livery can also change the instruments is has installed...

i'm thinking of craft like the c172p that has several liveries of IRL craft which may very well have slightly different instruments installed... i know that more recent work on the c172p used one from somewhere in Europe as the base for what was installed... i'm now kind of wondering if david's initial livery is still in the craft in FG and if so, maybe if my "wondering" is yes, then when david's livery is chosen for the c172p it will appear as david originally had it modeled... i remember the one in Europe went through some upgrades that the team followed and implemented... one of those "upgrades" brought is the pontoons and amphibious gear...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Does the artificial horizon work correctly in FlightGear

Postby wlbragg » Tue Sep 19, 2023 6:59 pm

one of those "upgrades" brought is the pontoons and amphibious gear

That was my doing and it wasn't based on any model in particular. At best it was based on the first 172 I saw in google with pontoons installed.:)

I don't remember if any liveries were removed? If they were, it wouldn't have been my call or doing as I don't subscribe to less options, only more.

Is someone saying that a livery that used to be there is no longer there? If so and it is still wanted, I'm sure I can get it out of history and restore it. I don't think the basic map has changed enough that it would probably just work. But it definitely doesn't change instruments. I don't recall any instruments attached to the livery system, but maybe? The textures certainly could be if one wanted to do the work, it's not difficult to include a texture change to a livery. Making the texture is probably the hardest part.
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Re: Does the artificial horizon work correctly in FlightGear

Postby wkitty42 » Tue Sep 19, 2023 7:58 pm

no, no one is saying anything... i don't know what the original c172p was wearing when the expansion by the current team got started... it was a simple question on my part...

as far as the pontoons go, i do remember you introducing them... i also remember seeing a picture of one of our livery models wearing pontoons... i'm not sure when that happened IRL compared to when you did your thing, though... i thought it was cool and figured you had done the pontoons because of that change of footwear that craft had done...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Does the artificial horizon work correctly in FlightGear

Postby david.megginson » Tue Sep 19, 2023 11:20 pm

I am not a visual artist, and any low-res liveries of mine from ~20 years ago are definitely not worth resurrecting.
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Re: Does the artificial horizon work correctly in FlightGear

Postby wkitty42 » Wed Sep 20, 2023 10:07 am

do you remember the tail number of the craft, david?

looking at the current c172p, i see these liveries/callsigns available... some are older lower quality and some are newer high quality... 4X-CHV is the current default...

4X-CHV_HD_livery.xml
CAP.xml
custom_callsign_1.xml
custom_callsign_2.xml
D-EEQA.xml
D-ENMU.xml
EI-MCF.xml
G-BEMB.xml
HB-CHX.xml
IVA.xml
KLM.xml
N301DP.xml
N35799_HD_livery.xml
N6575E.xml
N73429_HD_livery.xml
OH-CTL_HD_livery.xml
PT-IAO_HD_livery.xml
ZK-WAX.xml
ZS-MDF_HD_livery.xml
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Does the artificial horizon work correctly in FlightGear

Postby david.megginson » Thu Sep 21, 2023 7:47 pm

It would have been a Canadian callsign probably, perhaps a made-up one like "C-FGFS".
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Re: Does the artificial horizon work correctly in FlightGear

Postby wkitty42 » Thu Sep 21, 2023 8:05 pm

ahhhh... ok... it may still be around as the low poly AI c172... i was playing with several of the GA AI craft some time back and the c172 was one of those...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Does the artificial horizon work correctly in FlightGear

Postby 0303 » Wed Nov 08, 2023 3:15 pm

Does the artificial horizon tumble, go completely bananas, due to the built in mechanical stops (+-60 degree pitch or 110 degree roll) in older planes (like all Warbirds)?

You can see that in the first ("360") real Spitfire video in my thread start. Spitfire video roll timestamp: 17:01, 27:15, 31:40, 32:40, 37:50, 38:47, 39:08, 39:40.

Note how it flops multiple times after a roll, note it's 90 degree off when returned to level. As noted it takes about 9 minutes for complete self correction (for that specific Spitfire AH).

You can also watch it after it lands. It self corrects slowly, though not sure engine RPM while taxiing provides good suction, though it does seem to in my second Spitfire video. It corrects instantly on startup with engine idling, if I glean RPM meter right it's just 700-800 rpm.
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