BUG REPORT: V/S indication mismatch HUD and VVI

Hi there!

Not sure if many of us likes steamclocks. But there is a bug in indication of vertical speed. It appears when the sink or climb rate is more than 20 m/s. Numbers on the HUD and VVI doesnt match.

Well spoted! The VVI is incorrect for both climb and descent. See the attached track for a test. According to Tacview the HUD indicator is correct whereas the VVI is not.

Please excuse my embarrassing, unprofessional over-control whilst rolling out after the immelman.

DCS World 1.5.3.

The meter units are correct, the needle needs adjustment.

Edit: working fine...

Good catch. The problem is that the VVI scale, I believe, should be displaying vertical velocity in units of "1" from 0* to 10*, then units of "2" between 10* and 30*, then whatever.

 

BUT, what is happening now is that it's displaying units of "1" from 0* to 30*. So a HUD reading of 25*, for instance, will display on the VVI as 30*, 15* as 20*, etc.

Disregard everything I said. It's incorrect. Both the HUD and VVI correspond to each other. The VVI measures in units of "1" from 0* to 20* but "20" is where we think "30" is. ("20" is actually the larger tick mark just before "50".) Then it uses units of "10" to get to 30, 40 and, finally 50*.

Rich

Yea, your last post made me check that once again and yea totally correct. Meter shows all correctly. Call it a false alarm?

...Call it a false alarm?

Yes. But only because people like myself have been thinking "20" was the 3rd tick mark above and below "0".

Visually, when you look at the VVI, the positioning of the number "20" on the dial makes you think that it's associated with that 3rd major tick mark. But it's actually marking the 4th. There just isn't room for it up there toward the top of the dial. It would run into the number "50". So it's actually placed under the appropriate tick mark instead of across from it as it would be if so were further down the dial.

Call it a false alarm?

Partially right. But in the real plane indication cannot be so confusing. Is it worth changing VVI texture to the less confusing one?

The bug is that the texture is wrong the fat lines should only be on increments of 10 up until 20

Partially right. But in the real plane indication cannot be so confusing. Is it worth changing VVI texture to the less confusing one?

The bug is that the texture is wrong the fat lines should only be on increments of 10 up until 20

Never had reason to go searching for the real life equivalent until today. Both of you are, of course correct. Yes, it would be much less confusing if the texture were changed to match the real one. Found another example as well...

This any better?

This any better?

(For english cockpit)

Superb, it couldn't be any better!

Yes. But only because people like myself have been thinking "20" was the 3rd tick mark above and below "0".

 

Visually, when you look at the VVI, the positioning of the number "20" on the dial makes you think that it's associated with that 3rd major tick mark. But it's actually marking the 4th. There just isn't room for it up there toward the top of the dial. It would run into the number "50". So it's actually placed under the appropriate tick mark instead of across from it as it would be if so were further down the dial.

Ah, now that makes sense. That's got to be the most non-linear and confusing steam gauge that I've ever seen!!!

This any better?

Thank you for taking the time to provide both ENG and RUS versions. This is much better.

Darkfire,

Much less confusing with Hydrox's rework. Now it resembles the real deal

This any better?

Yes, that's a huge improvement, thanks for developing this :thumbup:

Thanks, everyone, for revealing the truth ;) I never noticed that one.

And thanks Hydrox for providing that excellent texture modification! It looks much better.

I just dropped the texture in my custom cockpit textures (\Mods\aircraft\Su-27\Liveries\Cockpit_Su-27\…). That new feature is really neat for that kind of adjustments.

You just have to modify the description.lua accordingly.

As we are here, could you please help me verify how that turn rate should be read (yellow curved line)?

If I'm not mistaken it should report the turn rate in degree(s) per second, from 0° to 45° (left/right) (15/30/45, per tick mark), for a reference speed of 500 km/h, is that right?

As we are here, could you please help me verify how that turn rate should be read (yellow curved line)?

If I'm not mistaken it should report the turn rate in degree(s) per second, from 0° to 45° (left/right) (15/30/45, per tick mark), for a reference speed of 500 km/h, is that right?

I think the yellow curved line displays approximate bank angle rather than turn rate, at least according to page 36 of the Su-27 flight manual?

You're welcome all. I'm glad that this came up, and it's better to read the meter now.

When this thread eventually banks and dives into bit heaven, you can always find the textures in user files.

...bit heaven...

:) that's funny!

I think the yellow curved line displays approximate bank angle rather than turn rate, at least according to page 36 of the Su-27 flight manual?

Thanks ;) I read the same thing, so I guess that's it. I really don't know much about aircraft instruments and I remember I was surprised with that "bank indicator" behavior. Then I searched for some russian sources but I didn't find anything really reliable or easy enough to translate.

Указатель поворота (from the russian manual) seems to also describe the turn and not only the roll "movement".

And the ADI seems way more consistent with the bank angle (that was confusing).

I also found some descriptions like this one:

Указатель поворота — это такая стрелка, связанная с электрическим гироскопом, которая отклоняется в сторону в случае, если самолет поворачивает (заметьте, поворачивает, а не просто кренится, находясь в скольжении). А вот указатель скольжения – это слегка изогнутая стеклянная трубка с тем самым «шариком».
По-английски этот комбинированный прибор называется Turn and Slip Indicator, что является аналогом русского названия. В разговоре и литературе его часто тоже сокращают до Turn Indicator, хотя указатель скольжения в нем, как правило, всегда есть.

>>> Google translate.

I assume the apparently inconsistent behavior might be due to the limitations of its gyroscopic nature.

Similar intruments (without the VVI) are called: Электрический указатель поворота.

I'm still searching for a clear explanation about how it works and what it shows.

But bank indicator seems acceptable.

Here are a few recent screenshots with specific discrepancies. (but, well, they told us it was an approximation ;) )

But who uses that part of the instrument anyway? :music_whistling:

I just did a quick test & I'm pretty sure that in-game at least it's just a bank indicator, and not a very accurate one at that :disgust: Tacview seems to agree with the bank indicator displayed on the HUD.

I guess it doesn't help that the Russian aviation industry don't always use the same nomenclature as Western manufacturers. Add in translation difficulties (when direct translation is even possible) & it creates a situation ripe for confusion :(

Edited to add: I'm actually surprised at how innaccurate the bank indicator can be. From what I remember from flying small single-engine prop planes 15-20 years ago the bank indicator was usually accurate. I wonder if the entire VVI + bank & slip instrument on the Su-27 is operated by a single gyroscope that isn't very good at accurately displaying multi-axis data.

DCS World 1.5.3

...

 

But who uses that part of the instrument anyway?

I can honestly say I've never paid the slightest attention to it, either. But...

Google translation aside...

"Указатель поворота — это такая стрелка, связанная с электрическим гироскопом, которая отклоняется в сторону в случае, если самолет поворачивает (заметьте, поворачивает, а не просто кренится, находясь в скольжении). А вот указатель скольжения – это слегка изогнутая стеклянная трубка с тем самым «шариком»."

Turn [not bank] indicator - this needle, coupled to the electric gyroscope, diverts to the side in the event that the aircraft turns (take note, turns rather than merely tilts [banks], as indicated by the slip). And here is the slip indicator - this slightly bent glass tube with a very "small ball".

A turn/slip indicator does not give a direct indication of bank angle. So it won't match the bank angles defined on the HUD. The gyro is mounted so that it responds to yaw or heading changes making the needle shift to the right or left. So it's indicating a turn. Just not sure what the rate is for each demarcation, etc.

But it is not a bank indicator, regardless of what the manual says, assuming your Russian source is referring to what we have in the cockpit.

Darkfire,

I'll take a look at your results, when I can. Hope to do some checking of my own as well. I suppose a quick way to check whether or not it's a bank indicator is to stop on a rudder pedal while holding wings level....

EDIT: Bourrinopathe's last two images at least strongly suggest that it's a turn indicator rather than bank indicator.

Good points. I don't have a set of pedals so I was banking without any pitch input. Not ideal but best I could do.

Thinking again about the instrument - it probably should be a turn indicator. What in the Flanker is called the VVI is in other aircraft normally called the turn & slip indicator.

I need to get a decent set of pedals.

I don't think it's neither bank or turning indicator, the needle reacts when I use stick or rudder, so more input I give the harder the needle moves, after I release stick, the needle still can stay somewhere else than middle, but could that be the fly by wire system where it gets the input data then. Anyway something like that, hard to type how I think it.

I don't think it's neither bank or turning indicator, the needle reacts when I use stick or rudder,...

Yes. The gyro is tied to the vertical axis so that it reacts to any change in heading whether caused by yaw (rudder) or bank (stick).It's used in conjunction with the slip indicator to make a coordinated turn. As such, it's a turn indicator:

Skip to time 3:43 and you'll see what I mean. But the entire video is well worth watching.

Interesting video, thanks for posting it.

Not sure what the value of such an indicator is on a modern aircraft that essentially takes care of coordinated turns automatically (i.e. flight control system). Setting rudder trim for asymmetric loads maybe?