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Two good videos. Training video describing Artificial Horizons from the oldest pneumatic to newer electrically driven. Their basic functionalities and errors. The pendulous vanes of pneumatic horizons described (applicable to every WW2 Warbird). Pedagogic explanation of what precession is. EDIT University of Nottingham guy describes precession hands on. http://www.sixtysymbols.com/videos/axial_precession.htm On second thought, this video instead, watch 8:20 - 16:55. It's a pedagogically much better explanation of precession. Yes, he talks about gyro-compass, but precession is precession, everything applies to gyro-horizon as well.

Found weirdness. Didn't want to clutter the "Bugs and problems" forum. A sticky to collect all DCS manual "problems"? Page 24. Both rudders? Aileron stick travel is asymmetrical and identical with elevator stick travel?

The bug thread is "reported" and locked. Add a few comments here I can't add in the locked bug thread (also inappropriate longish gyro discussion for strictly bug description thread). 1) It's not Chris Hadley (I got in my head it was Hadley) flying the Mk IX in 1st video. It's some guy named Rick Voler. 2) I speculated in the bug thread that low RPM gave insufficient suction and that's why horizon drifts. Watching the "Hadley" video, one can see the horizon correcting on startup at just 800 rpm (first 40 seconds and after landing). Watching carefully RPM is the upper right "clock" instrument (marked 0, 2, 4, 6, 8 ) and below right is the "boost" instrument. Squinting hard at opportune moments (sun from behind), one can read "RPM" and "Boost" and also their readings make sense while flying. He takes off with boost 7 and max out 3000 rpm. He smoothly increases boost and only reach 7 and 3000 after takeoff it seems. In DCS I just jam it to ~8 instantly ... Then rpm is reduced to 2650. Point being, horizon seems to correct already with idling 800 rpm so ... it should NOT drift at idle? In DCS it drifts on idle (very little) and when engine shuts down (much more so). Should it drift when engine shuts down? I don't understand enough to know. On one hand it stops spinning (after a while) so there's no spinning-rigidity but is there a simple gravity thing that makes it straight when shut down? Hunting youtube gyro horizon videos ... Below is a good series for people so inclined. Video 1, guy shows an electric (helicopter) gyro self corrects way faster than it needs to, even if mounted in an SR71 flying over the curvature of the earth. Hmmm ... 22 degrees in 10 min (slower than the Spitfire's 90 degrees in 9 minutes) and 29 degrees in 6 min in opposite direction. Having watched all 8 videos (weirdly ordered in reverse 8, 7, 6 ... 1), this is a very good explanatory series (playlist) of artificial horizon gyros from a professional jet pilot. He'll explain in 2nd video (7) why it corrects faster in one direction. I'm getting the impression that self correction is an inherent basic feature of how every (mechanical) artificial horizon works. It self corrects level with gravity (video 3 (6)). Video 5(4) explains how self correction works. First, it is slightly gravity balanced to become straight, but that is not the primary correction mechanism. Spinning generates air pressure (even in an electrical gyro). Small opposed air pressure ports are opened or closed by gravity controlled "pendulous vanes". When the horizon is aligned all air ports are half open applying zero corrective pressure. Obviously the gravity controlled "pendulous vanes" are subject to inertia, they don't "know" if a force comes from "plain" gravity or if the plane is being thrown around. Summarizing. An important concept I struggled slightly with before getting. The internal mechanism will always strive toward "true level". So even, for example, if you put the aircraft (the instrument casing) in an extended climb, it will NOT align with the climb, it will always align with "true level" and hence always show a correct indication throughout the climb. He goes into details. The instrument balance (gravity) calibration is simple and elegant. It's just two big screws, one for roll, one for pitch, fixed with loctite. This electrical gyro is different from the Spitfire gyro in at least one respect, it can be rolled without tumbling. Getting tempted to test all DCS Warbirds horizon gyros to see if they will self correct...

Thanks. Every word is perfectly consistent with my ~2.5 year experience. I have [WWII Assets Pack], I don't have [Combined Arms]. See my list above. I wonder if modules can make a difference? It did with another bug. The rolling. Tímestamps of every roll in the channel video. 17:01, 27:15, 31:40, 32:40, 37:50, 38:47, 39:08, 39:40. Yeah, I'm sad.

^ No crazy moves required (*1). Just spawn ... and wait. I discovered where it happens and can easily and quickly reproduce it. Made a new short track ... and a movie. I found the horizon needles drifts visibly randomly whenever the engine shuts down or (less so) with the engine just idling. I want to interpret this as modeling insufficient suction causing drift by vibration (*2). That would be great, but the problem is that the horizon never self correct once the engine have enough RPM. It "always" drifts on engine shutdown. In submitted track it also drifts instantly on spawn (idling runway). Just realized, it was my 50x speed up that suddenly made "drift on idle" visible, whereas I otherwise usually don't see it. Again, I believe the drift-on-insufficient-suction is just fine, the bug is the horizon NOT self correcting on higher RPM (2650 cruise track). The track Spawned, noticed immediate drift, revved up a short while just to see if it would start self correction. No. Cycled engine off / on six times. Spawning would have been enough but I wanted the needle at 60 degrees so it would be unambiguous. Recorded at 50x. Took off, flew straight and level (1x real time) aiming for gyro course 320 (~Batumi runway extension out to sea). Still at 60 degrees 10 minutes on. Quit. 10 minutes, again, because video of a real Spitfire Mk IX takes 9 minutes to fully self correct. Neither I or the real Mk IX fly perfectly level, obviously an insane demand to correct the horizon. The film I filmed 50x speed on runway and then filmed 10x speed flying. 8min:07sec. You can obviously skip and Youtube can be sped up 2x. Also, again, I note that the real Spitfire has it's horizon go coco for cocopuffs anytime it rolls, it would be nice to see that in DCS. The DCS horizon is aligned after 10 rolls if it was aligned before the roll (just tested). If it was unaligned it goes back to the same unalignment (kind of, something more is happening). Attached new logs and new track. Again, more people could try this shorter track? Use speed up, track stops at 8:49:37, so look after 49 (sped up) minutes if horizon leveled or as below (~video thumbnail). *1) Note for NineLine. This did happen: Historically, one bug did not reproduce for ED when [Combined Arms], which I don't have, was included I reported bug, ED couldn't reproduce until having the same set of modules installed as I had. *2) The needles drift randomly and independently of each other. Random in speed, direction and length (they even switch direction while drifting). Sometimes one needle drifts much more than the other. All this is good to my mind, they should be random. Just noting, don't expect needles to drift just like in this video / track in other tracks, they won't. But they do drift just the same replaying track so ... canned random? Logs.zip spitfire_horizon_v3.trk

^ By this I assume your artificial horizon was "horizontal" & centered at end of track? That's decisively different from what I'm seeing (diagonal). So, something is unambiguously different, something that can be identified. What could be different? Historically, one bug did not reproduce for ED when [Combined Arms], which I don't have, was included. The modules I have installed are (note, no Marianas): [I-16] [Normandy 1944 Map] [WWII Assets Pack] [Bf 109 K-4 Kurfurst] [UH-1H Huey] [F-86F Sabre] [Flaming Cliffs 3] [Spitfire LF Mk. IX] [P-51D Mustang] Repaired, reran track again Ran repair off the Win 10 start menu (as opposed command line) and checked these: Check all files (slow) ✓ Search for extra files after repair ✓ Renamed SAVED GAMES to create a "fresh" one. Reran the track (real time). Same result. Zipped logs just after program exit. I'm still interested if it happens to more people than me? Could more people please run the track? Real time full run 2h20min with 5 min to spare before mission end. Divide by whatever time acceleration used. Can set Windows alarm if run in background. Note 1. I found I must hit [F1] immediately after start of replay, to not lose function of some vision keys (to zoom in on horizon while replaying). Not terribly important, would start other thread if I wanted to discuss that. Note 2. Yes, the track ends out west to sea. The weirdness of horizon includes it (may) straighten out if turning south back towards Batumi again (it did earlier track version). Logs.zip

I've had the Spitfire since ~2019 and fly it more than anything else. Though I never "properly" tested it, I can't remember it ever working correctly.

The Artificial Horizon is very often badly out of whack (henceforth "wrong"), as many have noted. A little surprised that despite really trying (loop, roll ...) I have yet to find a quick way to get it "wrong". I'd love to make a short track but I couldn't. Interestingly, one real Mk IX (see film), messes up it's horizon anytime it rolls and then takes 9 minutes to self correct. Two things. DCS Spitfire horizon does not get "wrong" on rolling and it never self corrects (at least not in 80 minutes). Anyway, after 50 minutes, I manage to make it wrong by doing "donuts" and then finally I could do the test I set out to do: 1) Parked on runway, RPM 2200 (to provide suction) for 40 minutes+, horizon does not not self correct. 2) Fly plain and level for 40 minutes+, horizon is not self correcting. Note1, the 50 minutes Batumi - Soochi were flown straight and level to see if it would get wrong spontaneously. It didn't) Note2, I found the behavior after it's "wrong" weird. If I turn, in the air or on the rwy, I can get the horizon "right" again) Real life video references. 1) Hadley, Spitfire MK IX. https://youtu.be/Njjl_smtMoQ Within the first 40 sec, one can visually see the horizon creep in self correcting while on the ground. 2) Spitfire Mk IX crossing the channel. https://youtu.be/O-_AwgYxUW0 At 17:01 it rolls. Horizon gets instantly wrong. Watching from 18:06 (film cut) horizon is 90 degrees wrong. After 7 min (25:00) it's corrected itself in roll axis and after 2 more minutes it corrected itself in pitch axis too (total 9 min to completely self correct). The real Mk IX, in the film, rolls twice (at least), at 17:01 and at 27:15 (31:40, 32:40, 37:50, 38:47, 39:08, 39:40). Both (all) times the horizon gets instantly screwed up. Seems any roll always messes up the horizon in the real thing. In DCS it does not. Anyone so inclined can fast forward my track to the end (~10:24 [F2] time) to quickly verify non straight horizon is not just me.By [F2] time, I mean the lower right corner clock. ~ Track timestamps ([F2] view) to fast forward to: 8:00:00 Takeoff Batumi. 8:49:30 Full stop Soochi, horizon still good. Repair (nothing) Refuel. 8:52:00 Start donuts. Horizon gets "wrong". 8:59:15 - 9:42:15 Parked runway, horizon "wrong", RPM 2200 for 40+ min. Observe horizon not correcting. 9:43:40 - 10:25:12 Takeoff, course 270 (gyro) fly plain & level 40+ min. Horizon not correcting. Installation completely kosher, no mods no nothing. DCS 2.7.6.12852 Open Beta (recorded track) DCS 2.7.6.13133 Open Beta (replay) Intel Core i7 3630QM @ 2.40GHz (Max Turbo 3.40 GHz) 16.0GB Dual-Channel DDR3 @ 798MHz 2047MB NVIDIA GeForce GT 635M 447GB KINGSTON SA400S37480G (SATA-2 (SSD)) (~ 9:43:40) Soochi takeoff. Horizon "wrong" (10:23:40) After 40 min+ flight plain and level . Horizon still "wrong". spitfire_horizon_v2.trk

Thanks. How far can gain be turned up? I googled "sdef" and found very little. "Apple protocol" or "project software management" really? Is "sdef" a general multi platform file type or is it DCS specific?

Mea culpa. Yes, now I hear it. I think this should be included in next Open Beta (maybe even louder). Assuming Hadley's Mk IX is typical sound wise. I interpreted what you stated as create "\DCS\Sounds" under "SAVED GAMES\DCS.openbeta" and unzip "sdef.zip" into it. I didn't have a "Sounds" folder. But DCS = DCS.openbeta in my context, I get that now...

Not different Tanuki44. Look closer, identical (copied yours and mine): C:\Users\username\Saved Games\DCS.openbeta\DCS\Sounds\sdef\Aircrafts\SpitfireLFMkIX\Cockpit\ValveDrainHissIn.sdef C:\Users\username\Saved Games\DCS.openbeta\DCS\Sounds\sdef\Aircrafts\SpitfireLFMkIX\Cockpit\ValveDrainHissIn.sdef Thanks for verifying. Yes, I only hear it going up too. But in Hadley's video, you hear nothing when he flips it down at 8:40, so that checks. I ensured a pristine kosher SAVED GAMES by renaming old and forcing a new SAVED GAMES. My sounds settings (all default except switches 300%, music 0%): I could zip and attach SAVED GAMES if it serves a point. For now, saving 26MB in my account. ??? Unfamiliar with "SDEF" file. Sound definition? 1K is to small for the sound itself? Ok, here's my recordings. Max volume in game and PC or I wouldn't hear anything. They're the same to me. Sound Unmodified: EDIT Sound Modified

Rechecked, made recordings, compared. It's the same. Ran once and then renamed the added folder ("DCS\Sounds...") to take it out and ran again. You meant SAVED GAMES and not somewhere in the main folder? Maybe someone else can volunteer to try it? In case I'm missing something.

By turning up max volume I can hear it. I was wrong, it's there, but very low volume. I've never heard it before and wouldn't have known, except for the Hadley video. Modification have exactly the same (low) volume. Just for the record, how I installed it: C:\Users\username\Saved Games\DCS.openbeta\DCS\Sounds\sdef\Aircrafts\SpitfireLFMkIX\Cockpit\ValveDrainHissIn.sdef I wonder if it's depending on microphone placement.

Now I did a proper test It was painful. It raised more questions. Next post might be an error report. I recorded a long track with three tests. I flew 4x speed. Best way to present is probably a video in 3x 30 minute chunks (sped up 10x maybe), which is also a lot of work. 1) Took off, flew straight and smooth Batumi - Sochi. Horizon (nearly) perfect all the way. Ever so slightly off after full stop. 2) Refueled and did donuts on Sochi rwy until I managed to get horizon crooked. Locked brakes and let it sit 30+ minutes. Horizon did not correct at all (Hadley's real Mk IX does visibly correct itself on the ground according to video). 3) Took off and flew back to Batumi (4x), starting with a crooked horizon. Here's weirdness and new questions. Horizon swings opposite directions depending if turning left or turning right (*1). Having turned either direction, it does not correct itself (as it should) if keep going straight. But turning other direction one can make it straight again, if turning just the right amount, if turning further, horizon gets crooked in opposite direction. *1) Same thing happens on the ground, doing donuts it gets crooked after 90-180 degrees, but straight again after 360 degrees. Eventually I managed to get it crooked while also pointing along the rwy so I could take off with horizon crooked and do the flight back to Batumi test. ~ Test 2) is conclusive enough I think, it doesn't work as it should. Not quite sure what happens in test 3) but it doesn't straighten out while flying straight, so that's seems wrong. Another point not explored is pitch. I did another long track first (can't use because stupidly landing on carrier and replay hits the sea) where I noted pitch wise the horizon was all wrong after a long smooth flight (1x time) Batumi - Guadata. So pitch correction is also not right. If anything it seemed pitch got worse and worse (horizon receding downwards). Trying to summarize. If it is correct, it stays correct (see test 1). If provoked "wrong" it stays wrong, no matter what. Track is very long and quite boring. Uploaded here, object oriented, so I don't lose track of the track. spitfire_horizon.trk

Hmm... I wrote "less than perfect test" above. Now trying to mess up the horizon for a proper test. I didn't manage to mess it up. My "less than perfect test" included a screaming dive from 30K as finish. May have influenced final result. Maybe the horizon works after all. I need to do a better proper test before I state anything. Ignore my complaint above for now. Out of time for more tests right now... What I want do to is to screw up it up properly and then fill the tank, fly straight and see if it corrects.

Scouring the net ... found 360' view 48 min video Dover to Dunkirk where horizon is visible. I might, at some point, gather the energy to watch all of it ... at 2x speed. It stays good for a good long while early on. Fastforward to 20:00, it's effed up, but at 25:00 it's straight again. Stays fine during turns until 27:15 when he rolls and it's effed up again. Generally seems it stays fine until a roll or looping, after which it takes ~5 min to get straight again. Generally, not all horizon does the dancing as in Hatfield's video above. The astronaut who besides space, also writes hit songs and fly Spitfire, I hate him so much... A thought, probably wrong: Are restored "modern" Spitfires required to have a calibrated top shape horizon instrument? Not much need for it VFR.

At 9:57 the pneumatic hiss is very audible in this real Mk9.

I think it corrects, if just slightly, between 6:34 - 7:15. Rewatched the startup more closely, one can visibly see it moving.

Real thing video. Note, it's effed up immediately after engine start but after time cut (warm up?) it's straight (auto correct or reset?). On landing it's almost straight and on taxiing one can see it auto corrects while taxiing straight, gets slightly off when turning and corrects again when taxiing straight again, on engine off it's perfectly straight. Fastforwarded the actual flying, I just imagine it would straighten if he didn't turn all the time. Unrelated, we're missing the loud pneumatic hiss when taking up the flap. Just spawned rwy Idle to verify, no nothing, just the lever click.

But they don't fail 100% of the time do they? The P-51 horizon is usable because it can be reset, you can get 15 minutes (or something) out of it, getting through a cloud maybe. Once the Spitfire is out of sync, which it is sometimes from takeoff (says some people, cant confirm), it's just gone. (personally I spun up the battery driven ball & turn in gliders just to listen to it ... never mind) As mentioned, I've had the Spitfire for 2-3 years and I've kept quiet wondering if it's something I just don't get on how to use it, or for it to be "fixed". It's getting old.

I can't believe a real life instrument would be completely useless.

I just emptied a tank without the horizon auto correcting. Spitfire has behaved like this the 2-3 years I had it. It's getting old. If it acted like this in real life it would be completely useless. I waited for it to be fixed a long while, without saying anything. I thought about making a long flight to test the "auto correct". Didn't set out to do this but flew a long while straight 100 nm at least, and noted still all wrong. Not a perfect test, stalled a bit, but didn't notice any correction. A way to "correct" it is to make wild acrobatics opposite direction, but that's ridiculous and can only get it approximately anyway.

At 8:43. The blue panel and the rad flap switches looks "off" to me. Can't say exactly what's "off", looks 2D 'ish. Otherwise much of the cockpit looks beautiful.

Move it elsewhere? Inside subforum it takes you to last unread post. Outside subforum it marks everything read.