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A-10C FM discusion


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I wanted to reopen a discussion on the A10 FM on the forums, it seems that the road to getting fixes is going to be a long one. Both Habu (a rlf active duty A10 piolt) and I have been very suspicious of the A10's FM for a long time. Habu has been on the forums for a while now since he got assigned to an A10C unit and started talking about the differences in performance. Recently however we started to make a big push for fixes especially considering that the GAU-8 dispersion finally got mostly fixed (something else he has been saying is wrong for a long time)

 

Now with the FM we believe the biggest issue is some combination of drag especially at high aoa and/or lift. With a secondary concern being engine thrust.

 

-----------Drag--------------

Habu's notes after testing the FM and comparing it to the docs he has from his unit in response to this quick vid I made as a baseline.

His response:

 

- yup! 4.5 G's chopped tone confirmed bulls* at this airspeed and configuration you should have 0 problem pulling 5G with no tones; generally at 350 knots steady tone is achieved at about 6.3-6.4 G's. The biggest and most egregious thing is the speed bleed off that's what's causing the problem. On a normal turn level turn at that altitude and temperature you should have 0 problem pulling 5G's with a bleedoff to nothing less than probably 280 knots and that's a wag, i'll give you better data later.

 

Extra data:

 

...and that is why ED are absolutely and positively wrong i had no idea what the Em diagram was going to say, it was just based on experience and feel, and I was 100% correct based on science at exactly 4G's turn it's a little over 5 knots lost per second.

 

So, for a Turn level turn safe escape one should roll to 90° of bank reaching 4g's within 2 seconds for at least 60° of turn one should bleed speed at around 5kts per second. The turn should take around 4 seconds and as such bleed off around 20kts of airspeed. (75% fuel, 2mavs, 6Mk82, full gun)

 

Currently in game with a clean jet at 75% loses just under that 20kts let alone a jet with munitions.

 

----

 

Also as you were asking about the buffet, the buffet comes well after chopped tone steady is 1 aoa unit away from "stall". Stall occurs well before "buffet"in my experience chopped tone is stall in DCS; it's not necessarily true. The reason why we respect chopped tone is due to engine flameout considerations. Tactically it's because in chopped tone you have no idea where you live in the stall and engine disturbance region

Qf8fReL.png

U4C647D.png

 

 

Engine -------------------

 

So something that has been disused a lot is the engine performance while habu and I don't think its the main cause for the performance issues it does seem some parameters are off. Now Habu shared with me an image he took while flying of the instrument panel, now he didn't want me sharing the image on a public forum but I can share the results. Take note we matched the ingame conditions to the rlf one as much as possible for pressure, temperature, and winds. The picture however was shared with 9L so it should be in ED's hands.

 

Current in Game

YUGX7cV.png

 

 

Temps in DCS are low and the max temps marked in the real jet are higher

 

- Just under 800 DCS and ~805-850 rlf

 

PSI is quite high

 

- DCS ~94 and ~70 rlf

 

Fan is low, now this is important as this gauge has been described to me as being representative of the thrust being put out by the engine.

 

- DCS ~82-83 and ~86 rlf

 

Fuel flow is high in DCS

 

- DCS ~3650 and ~3350 rlf

 

Now I know its been debated the engine parameters for a long time but I hope this can shed some light on the issue.

 

--------------------------

Thanks for the feedback, currently ED is working with the USAF, and real A-10C pilots are interacting with DCS World. I know this becomes my A-10 pilot vs yours, and I don't mean it to, but its important for ED to also have these private contracts, and if they are happy with the A-10C, I am not sure where else I can take it, perhaps have your A-10C pilot directly contact ED management.

 

Well at this point we don't know who your piolts are or if they've even really tested the jet. Habu spent well over an hour doing tests of the jet and comparing to the actual docs he has from his unit. Not only that but at this point there's been what 3 other rlf piolts who've all said the same thing and a few crew chiefs... like I'm sorry but I don't see how its even possible that your piolts can even say its accurate if they've actually tested it and cared about how accurate the FM is. People who I know personally who I've been sitting in discord with as they've tested the FM and compared to the docs they got from the unit they fly with say its wrong often very wrong... Not to mention the actual image he took while in the jet shows with out a doubt that the ingame engines are off. Ontop of that when compared to the A-10A-1-1 document DCS is off as well.

--------------------


Edited by nighthawk2174
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Very nice analysis, hopefully this will push ED to implement the necessary changes to correct the behavior, though this might be due to contract agreements made when the A10 module became a thing. It might be intentional.

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In my opinion as an actual pilot of this jet, this is the single most important issue facing ED's simulation of the A-10 in DCS. Based on testing and comparison to "feel" which I can speak for personally, the issue is primarily 1) G available and 2) airspeed bleed off when AoA is applied to the jet, specifically during a 4G safe escape maneuver in the horizontal (TLT) or vertical (CLM). As it stands right now, the current A-10 will frag itself in every iteration of a low altitude Mk-82AIR PO1 delivery due to insufficient turning ability.

 

 

 

When I talk about "feel" of the jet, this is one thing. When I compare the jet's performance to the data I have access to, that's another ball game completely. Long story short, it's positively incorrect in this sim, and I highly recommend looking at this topic from an independent standpoint, i.e. starting from 0 when it comes to sources, before releasing the next iteration of A-10 for DCS.

 

 

 

I'm very happy to share my career field with enthusiasts using the venue provided by DCS. This thread, and hundreds like it, are not a criticism of the sim meant to be taken personally or for the satisfaction of passive internet observers. Criticism in this way is simply an indicator of passion and enthusiasm for the product you have created.

 

 

 

I have offered my assistance to help assess the A-10 as it stands in DCS. That offer is still open.

 

 

Habu


Edited by Habu23

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In my opinion as an actual pilot of this jet, this is the single most important issue facing ED's simulation of the A-10 in DCS. Based on testing and comparison to "feel" which I can speak for personally, the issue is primarily 1) G available and 2) airspeed bleed off when AoA is applied to the jet, specifically during a 4G safe escape maneuver in the horizontal (TLT) or vertical (CLM). As it stands right now, the current A-10 will frag itself in every iteration of a low altitude Mk-82AIR PO1 delivery due to insufficient turning ability.

 

 

 

When I talk about "feel" of the jet, this is one thing. When I compare the jet's performance to the data I have access to, that's another ball game completely. Long story short, it's positively incorrect in this sim, and I highly recommend looking at this topic from an independent standpoint, i.e. starting from 0 when it comes to sources, before releasing the next iteration of A-10 for DCS.

 

 

 

I'm very happy to share my career field with enthusiasts using the venue provided by DCS. This thread, and hundreds like it, are not a criticism of the sim meant to be taken personally or for the satisfaction of passive internet observers. Criticism in this way is simply an indicator of passion and enthusiasm for the product you have created.

 

 

 

I have offered my assistance to help assess the A-10 as it stands in DCS. That offer is still open.

 

 

Habu

 

 

Thank you very much for your input and time. It does give more worth to something I said myself as a non-pilot as I felt from playing it a few years and comparing with a few videos of it diving, climbing and cornering and it felt to me like the A-10C in DCS was "draggy", well that thread turned out into a huge discussion and is probably the most popular thread I've opened on these forums.

 

I had no proper way of explaining it in detail or anything specific. I know the basics now well, I did lurk around and I did play Lock-On way back in the day, I watched a TON of Air Crash Investigations (not saying that counts here, but overall it should heh) and I never piloted any real plane, not flew with anything except a little sport plane once, so my feeling could aswell be regarded as "beginner luckiness" or a coincidence, I don't want to brag or take credit at all that I was able to see the discrepancy by just a youtube video and my unprofessional DCS experience, it could be true but won't try to prove it myself.

 

Looking back now, as suggested by the people in that thread, I should have done a more detailed explanation and test comparisons more closely resembeling the weight (loadout/fuel) as seen in the videos, and the second thing is I didn't even use any TacView replays and data because the big world in game can make it appear that you move slower than you actually are, and cockpit camera FOV (cockpit zoom) also plays a big factor to that feeling, so there's quite a few factors I didn't count in.

 

But if you say so ... and that's similar of what I felt, then I guess it adds credence, but as I said I don't want to be the one proving that unless I take this issue seriously and have more data/experience/tests behind me.

 

I just listened to the Air Combat Sim podcast where they talked about the A-10C FM and it was again mentioned that it was already explained that the DCS versions can't be exactly the same because of all the usually documentation and classification as well as license limitations, if speed is one of them ... I ask my self why would speed be the issue where all the adversaries probably know all the real numbers already and the whole military community knows it's slow and the biggest issue is the engines, why would we get even slower version, if there's issues in these kind of negotiations I suggest that the negotiation sacrifices something else in turn to get the best and most realistic speed possible, and we just don't have access to some sensor or something else that's touchy, now ... would we give up HMCS for Speed ... ugh that one's really hard.

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could it be nerfed on purpose? anyone compare the alpha version against the charlie? from what i have read it seems all alphas were upgraded to charlies. mostly internal systems. like improved avionics for precision weapons. i see nothing of improved engines from an alpha to a charlie. means the engines are from the late 60s.

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Except I don't think the drama is necessary, on all sides, first we can't expect the sim to ever be 100% accurate in 100% of areas, and they can't expect to be necessairly be able to get it right even if they "looked at all the docs and stuff" (not quoting literally), it's been said so many times it's realism at the point of when things are relased is "up to the level docs/effort/resources allow" so this means there will always be something that we may find that needs improvement later on, and so things keep going, but it's still more realistic as time goes on, this is infact a journey, this is to be expected, the expectations may be unrealistic, it just happens that this touches the buttons because it happens to be a thing that has a big consequence, there's probably so many other unintentional and intentional inaccuracies most of the community doesn't know about and they go through as thin air thinking they're playing the real thing ... do the AoA lights blink at the same exact frequency?

 

But what is an intentional inaccuracy, it's just an area that received less focus/resources/time, most of the time, and perhaps some of those come out a bit lower than it was intended even with the low focus/resource allocation, and the biggest problem of the community here is they whine it up as if it's this big sin has been commited and oh may gawd it's a huge mistake, ahh the drama ... what about all the ground units damage modelling, is that a mistake too, it's just not been focused at, it's that simple, if for me reading and watching youtube videos in general about the this wasn't done that wasn't done, imagine how it must be annoying and demotivational for them.

 

I mean this in general, for every of these "mistakes", if it's a real mistake I don't think why do they need to get in everyone's face admitting it like, it's far easier if you let the time pass and the mistaker comes out himself when it is comfortable, rather than being forced, heck it may happen in a progress report down the line prior to II release.

 

If you guys really believe the nerf was an evil intention that was decided ... like we know it's speedier but we're going to make it slower to piss of the community, then that must be a sabotage!

What if it's a typo, that some factor that determines how much airspeed bleeds off in that particular case has an extra zero in there. But I guess you guys may be ahead of me, I do not know the history of this issue, but what is the reasoning behind the perception this is intentional and not a bug, I assume the responses?

 

I rather have this thing discussed well, AND so many other juicy A-10C things like emmmm multiple suites variations mmmmm, than a rushy FM fix.


Edited by Worrazen

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could it be nerfed on purpose? anyone compare the alpha version against the charlie? from what i have read it seems all alphas were upgraded to charlies. mostly internal systems. like improved avionics for precision weapons. i see nothing of improved engines from an alpha to a charlie. means the engines are from the late 60s.

 

No there weren't any performance improvements just internal upgrades, hence why yo-yo in the past has said if you want to prove the fm is off then get your hands on the a10a-34-1-1 and prove it.

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I have an out there theory to toss up: If I buy a 20HP lawnmower engine, I get a new engine and a guarantee it will product 20.0 HP for at least the duration of the warranty, and likely much longer if maintained properly. Now to deliver on the 20.0 guarantee, the engine will actually product well over 20.0, but the documents are going to indicate the minimum/guaranteed performance. Drawings come from engineers, who pad their numbers with safety margins to ensure their products always exceed their designs.

 

Thus my theory is that ED building to the published docs means they are building the worst possible (but technically passable) A-10 FM with worst-case drag and minimum passable power.

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I can't speak to drag issues, but it is a convincing argument. In terms of the engines, if you put what DCS has into a real aircraft it would be grounded. So there is a difference of putting it at the low end of performance limits and that. Passion on this subject stems less from "blinking lights and rivet counting", but where simulation of the FM=simulation of the aircraft. Wildly off when you bill yourself as a highly detailed simulator makes heads crop up.

 

There was a reddit post a few weeks back that basically said "we checked and the Air Force is happy". Either their Air Force rep has no idea what the engine should be doing or they are nerfing it on purpose for whatever reason. In any case it is what it is. I said my piece earlier and now I will just enjoy it for what it is.

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It hits the numbers. It a simulation of the A_10C

No need for your expertise unless you also have a engineers degree.

And a spare 1000 hours $$. To try and make it better and still hit all the chart numbers as it does now. Are you going to pay for these hours to TRY and get this web of equations correct because it feels off. Sounds like a costly enterprise.

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@David. So since I do have an engineering degree, am I permitted to continue an engaging discussion about the sim I love? I wasn’t aware of that prerequisite, but I’m glad I make the cut in your eye. Nothing said was negative, simply offering a theory that might help resolve discrepancies others have reported.

 

My personal opinion is that I enjoy flying within limits of an airframe. If I wanted a “point and fly” aircraft I’d place ace combat. If you don’t want to hear opinions, maybe don’t read forum posts?

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It hits the numbers. It a simulation of the A_10C

No need for your expertise unless you also have a engineers degree.

And a spare 1000 hours $$. To try and make it better and still hit all the chart numbers as it does now. Are you going to pay for these hours to TRY and get this web of equations correct because it feels off. Sounds like a costly enterprise.

 

It is not a feeling. It doesn't reach acceptable fan speed limits on the trim chart used by jet troops. Don't need an engineering degree to read a chart and perform maintenance runs.

 

I don't know how they approach the simulation coding or if it is like real world where 80% of thrust comes off the fan. If it is, it is thrust deficient and the fan speed needs punched up at least 3% to be minimum limits. Doesn't sound like a lot to most, but to an engine troop it is a lot, especially multiplied by 2. Not asking for complete recoding and deadnuts on peformance. Just a fan speed tune up in the current format.

 

In any event, nothing is going to be changed and I am perfectly okay with that just to be clear.

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My interest in the question is because I am frequently cross referencing information and procedures from other sources, but if we can confirm there is a discrepancy then it would help educate on any conversions required when taking procedures into DCS. Still love DCS, still not suggesting any changes, just enjoy studying the behaviours.

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Yes a fix to the engines would be amazing but me and Habu are both quite convinced it is not the primary issue, just one of them. It would also be nice if it could hit the available g's as per the 1A-10A-34-1-1 and not bleed off as much speed. Beyond this I have concerns regarding its stability at high aoa/g-loads as per video evidence and discussion with Habu.

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You've convinced me too, I just don't have any material experience to add to the matter. Engine building, and systems testing and tuning is more my baliwick so I responded to that specifically. In the mean time I'll just keep blowing **** up :pilotfly::joystick:

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@David. So since I do have an engineering degree, am I permitted to continue an engaging discussion about the sim I love? I wasn’t aware of that prerequisite, but I’m glad I make the cut in your eye. Nothing said was negative, simply offering a theory that might help resolve discrepancies others have reported.

 

My personal opinion is that I enjoy flying within limits of an airframe. If I wanted a “point and fly” aircraft I’d place ace combat. If you don’t want to hear opinions, maybe don’t read forum posts?

 

Discuss a way.....

 

"I permitted to continue an engaging discussion" The "pun / joke " here is for YOU to get a job with ED and put up the 1000 free hours of your time to make it better.

 

If you are an engineer? "YOU" should no ED will not touch this unless someone here has access to more info, not it doesn't feel right. Just play with the equations until our now "new SME" will sign it off for you. Who is paying for this?

 

ED had many SME's to go over this aircraft, many would have agreed / disagree on many things. But now these guy's want 1000's of engineer hours spent because someone said... On a 60 dollar product. Good luck with that. This was built with supplied wind tunnel data by the way, to change the data means just playing with it until someone now feels like it's ok? Yep sure, we will put our to top engineers on it right away. This may set the F-16 and hornet back a year or so, everyone good with that.

 

It is not a feeling. It doesn't reach acceptable fan speed limits on the trim chart used by jet troops. Don't need an engineering degree to read a chart and perform maintenance runs.

 

I don't know how they approach the simulation coding or if it is like real world where 80% of thrust comes off the fan. If it is, it is thrust deficient and the fan speed needs punched up at least 3% to be minimum limits. Doesn't sound like a lot to most, but to an engine troop it is a lot, especially multiplied by 2. Not asking for complete recoding and deadnuts on peformance. Just a fan speed tune up in the current format.

 

In any event, nothing is going to be changed and I am perfectly okay with that just to be clear.

 

Find more info than ED has for the engineers to work with. They will not play with it for 100's / 1000's of hours to guess what it should be.

 

"Available" A10C engine model documents

https://forums.eagle.ru/showthread.php?p=2868802#post2868802

 

Edit

They possibly are "allowed" to perform better IRL. We just don't no how or why? (The air force engineers would have documented this) and the new allowable tolerances on these engines etc.

 

and the engines / air frame we have now does hit the chart numbers in the A-10C documentation etc.

 

People who I know personally who I've been sitting in discord with as they've tested the FM and compared to the docs they got from the unit they fly with say its wrong often very wrong... Not to mention the actual image he took while in the jet shows with out a doubt that the ingame engines are off. Ontop of that when compared to the A-10A-1-1 document DCS is off as well.

--------------------

 

Show me how and where it's wrong. I know this got beta tested to death with all the documents.

Don't just SAY it's very very wrong because discord said lol. Tell me where so others can test it, like it has been 1000's of times by beta testers way way back.


Edited by David OC

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Edit

They possibly are "allowed" to perform better IRL. We just don't no how or why? (The air force engineers would have documented this) and the new allowable tolerances on these engines etc.

 

and the engines / air frame we have now does hit the chart numbers in the A-10C documentation etc.

 

Already did here: https://forums.eagle.ru/showthread.php?t=269627

 

Since I didn't get a response, I'm assuming they do not have engine 10C TO access.

 

So this site has the 1A-10A-2-71JG-2: http://www.newportaero.com/home/manuals/technical_orders/browse/___5004/to.html

 

I'm not going to buy a manual I have access to with the same info just to prove a point. Limits haven't changed in 40 years, though accuracy in recording data has. Even going through that thread I tested parameters from the example CETADS picture. The engine still falls short.

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Already did here: https://forums.eagle.ru/showthread.php?t=269627

 

Since I didn't get a response, I'm assuming they do not have engine 10C TO access.

 

So this site has the 1A-10A-2-71JG-2: http://www.newportaero.com/home/manuals/technical_orders/browse/___5004/to.html

 

I'm not going to buy a manual I have access to with the same info just to prove a point. Limits haven't changed in 40 years, though accuracy in recording data has. Even going through that thread I tested parameters from the example CETADS picture. The engine still falls short.

 

You think it falls short of power? Or what the gauges say in pit are off. Many have said and tested this against the chart numbers and it's good still. I'm not saying that a real A-10 is like this, it could very well outperform the supplied charts. Even so , not sure what ED would do about it or with it. How much should they keep spending to find the knife edge of pc simulation.

 

Edit: Added video

 

Professional expectations?

 

discussing the DCS OH-58D

 

Many SME's on this module

. To make it as good and as close as it can be.

Not even there own million dollar sims could match the real thing. OH-58D or the AH-64 Apache that they have flown.


Edited by David OC

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You think it falls short of power? Or what the gauges say in pit are off. Many have said and tested this against the chart numbers and it's good still. I'm not saying that a real A-10 is like this, it could very well outperform the supplied charts. Even so , not sure what ED would do about it or with it. How much should they keep spending to find the knife edge of pc simulation.

 

Both. Operating under the assumption that A: the model is such that fan speed is representative of thrust as it should be, B: Being a video game the gauges are 100% accurate of the "digital engine information" in the simulation. If the gauges don't reflect the simulation data than okay, that is odd, hard to have solid starting point there.

 

Not sure what charts were tested against, but only one is used to determine proper thrust output and tuning and that is the fan speed trim chart found in the 1A-10(A)C-2-71JG-2 or 2J-TF34-116-9.

 

Further explanation in my older post along with reference photos. Ignore the minor other stuff, main focus is the fan output.

 

https://forums.eagle.ru/showthread.php?t=269627

I edited post #1 to be a little more specific, but those with legitimate access can look into the documents and find the same fan speed trim chart to verify I am not talking out of my a**. New engines, old engines, test cell, installed, all are trimmed to this chart (EPU calculates sensor data to figure out where the engine should be along it). Based on Outside Air Temperature (OAT), engines MUST produce target fan speed as this is the primary indication of proper thrust on a high bypass turbofan. ITT is more of an indication of efficiency, how much fuel it takes, at producing said fan speed. A 790 ITT motor and an 830 ITT motor are both producing the same thrust (core output is marginal) at any identical fan speed. The 790 motor is just better at it and will last longer. Henceforth I am ignoring ITT in further discussion of thrust except for comparison sake or explaining fuel flow relationships.

 

Why am I bringing any of this up? If Fan trim (NF Trim, NFTR) is a few percent under target, performance recovery is a concern. If GE is concerned with that narrow of a margin, it is probably important to thrust output and achieving that ~8900lbs.

 

The Test

The chart is based on static engine runs so we will mimic that. A simple "trim pad" simulation is to set the desired OAT in Mission Editor and setup a hot start. Upon starting the flight, shut down an engine, stand on the brakes and giv'er the beans. There are some assumptions being made when looking at expected performance:

 

1. Bleed air and generator effects on the engine are not modeled. The switch does nothing to performance. It is not uncommon to lose ~1-1.5% fan speed on static runs with bleed air and respective generator on as they sap the power output of the compressor. This is why the trim checks are typically done with these items off. Now, even though these are on in flight, data suggest most of the loss is recovered from ram air into the fan inlet as the aircraft moves. This is also not modeled as far as I can tell. So it's a wash and negligible. I will look for "bleed air off" speeds.

 

2. Rectifying gauge data and direct digital data we use for engine monitoring. In the real world there is some acceptable slop in analog gauges displaying digital information. Unless ED models gauge variance, in the perfect video game world I'm expecting gauges to be direct digital information.

 

Factoring the chart and averaging real world data at different OAT, I expected fan speed to be somewhere in the blue area or a little less. The fan fall off per OAT is good, but fan speed looks to be about ~4-5% below normal across the power band. This doesn't seem like much but it is well outside usual NFTR and would be cause for grounding in the real world. Looking at the example engine data shown before, I decided to focus in on #1 since #2 is in a throttled back state. The 15.78 OAT picture has red lines for real engine reference. The DCS engine should still have fan brought up ~2-3% to be within limits.

 

Some minor thoughts on gauge information that isn't really about performance but rather increasing representative data accuracy.

 

1. Fuel flow is kinda high but within limits. There appears to be a direct relationship between fuel flow and fan speed. This is incorrect. The fuel control is mechanically tied to the compressor and thus should have a flow rate correlating with core speed until it reaches the T5 limit at the top end. Once there fuel rate should stabilize with ITT no matter the OAT.

 

2. I wasn't watching oil on spool up but ditto oil/core relationship. Oil pressure at max is too high. 95 is max allowable and typically only seen with cold starts. Once warmed up, pressures soak back to look more like the example engine at max.

 

4. There should be a delay in fan spool up after core spools up in both motor and normal starts. Fan will stop rotating before core on shutdown.

 

5. A good average ITT is 820 but that is here nor there.

 

A big item is the fuel override switch. This doesn't do anything in DCS. It should turn off the T5 and unlock full potential power of the engine with no restraints. This is where you should see the 9,060 number. I haven't fire walled an unlimited engine to know what kind of fan speed you obtain but if I had to guess it would be ~3-5% maybe. Core and all other gauges should be approaching or exceeding maximum values. It would be nice having a working get out of jail free card.

 

That is my 2 cents.

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