reported Huey's new performance profile discussion

[Tim_Fragmagnet]

51 minutes ago, SMH said:

Ground effect hover in the OLD engine model... note the pedal deflection. Then compare with the new EM. Almost no pedal range left! Just to hover in ground effect!

The old EM behavior jibes with every real-world video I've carefully observed over the 7 years I've been flying this module. The needed pedal deflection has more than doubled. We don't have enough authority in cyclic, pedals, or stabilator anymore. (Again, no doubt because the new EM is overpowering them. You can't just change one thing independently of everything else and if you do you throw out literal man-years worth of testing and tweaking!)

Stop obsessing over little numbers in tables and take a look at the whole thing together! It's no longer coherent or believable. Do your really think it was that wrong before and 

I have said "Standard Day, Sea Level" several times. You're just not listening. You even have the Mission file to try it with and check anything you want in.

Well at standard day the coefficient of power would be 29.5 thus the end result is about 1.5inches from full left which is still close enough to be considered standard deviation.

However.

I have not once denied that the amount of engine power required in a hover is wrong.
It is wrong.

That's exactly what this chart from the opening post details 



This chart shows exactly how much lift is produced for any amount of given power.
As we can see, in no situation is it correct.
In every case we are producing far too little lift for any given input power, especially while out of ground effect.

Out of ground effect is actually the most important one there, because that is the rotor producing lift with nothing else interacting with it, meaning that is the baseline performance of the rotor, if that is wrong, everything else is wrong because of it.

If you fix the rotor, the engine power required comes down, the left pedal requirement eases up

yes, the engine needs more work I have said that on multiple occasions
but it's not just the engine.
it's the rotor
it's the flight dynamics
it's tweaking the ground effect.

Yes, the amount of left pedal required for any amount of input torque is close enough
but the amount of torque required for any amount of lift is not.
thus the amount of left pedal required for any amount of lift is not correct.
because the lift is not correct.

[CHPL]

I don't want to offend anyone, but the discussion has, meanwhile, the character of a dispute between 2 professors about theories for which neither of them has practical experience.

What I want to say is that the discussion is miles away from any practical application. Do we want a realistic flight model? Of course, but ED is working on it. Tango seems to be very popular among programmers, but still, in the end, it always goes two steps forward and only one step back. 

In real life, however, there are no two machines that are precisely the same, even if they are identical types and even if they fell off the same assembly line one after the other. There are performance ranges in which they should move, but that's it.  
Basically, I adapt to the circumstances. The reference to scales and tables helps little in practice and has, in the end, only legal significance. If I have moved outside the table, I am guilty. If I moved within and it still went wrong, it was just bad luck.

What I want to say is the effort in all honor, but always the same things with even more tables to boil up helps no one.

Let's take Vietnam as an example, the technicians on site pimped the engine, and even without these changes, they did what they could when the air was led and didn't care about tables.

 It is today's madness in which theorists have taken over, and the engine automatically shuts down in flight to protect it from overload. (No kidding, I think a Sikorsky engineer did that.) The test pilot didn't survive the surprise.

So we wait and see. When the final model arrives, I'll be the first to complain when the engine is still running even though I've set the throttle to ground idle but don't touch the collective, and the needles still don't separate properly. And, and, and. 
 

[Tim_Fragmagnet]

19 minutes ago, CHPL said:

There are performance ranges in which they should move, but that's it.  

Actually, I have a bunch of that kindof data too

This aircraft and its constituent parts were tested and documented in extreme detail.

 

 

But yes the argument has gone on long enough and won't change much.
The need for another rework has been acknowledged and we'll get it eventually.

Edited October 11, 2023 by Tim_Fragmagnet

[BIGNEWY]

Hi all, 

please keep the discussion friendly and allow us time, as you can see we have a handful of people all making various claims about the flight model and we have to take our time checking. 

We do appreciate your comments, and know that flight models are important to you and it is the same for us, DCS has a special breed of dedicated rivet counters with huge passion for accuracy which is awesome to see. 

Again ensure you are keeping to our rules which can be found at the top of the forum. 

thank you 

[SMH]

6 hours ago, fapador said:

You are right on the money saying that there is not enough lift produced by the rotor! I have been told the exact same thing from real operators that had a go at dcs huey as they needed a lot more power than normal for pretty much all maneuvers and they know their stuff really well

As I am waiting for a fix as a temporary workaround I recommend flying they Huey with as little weight as possible even with 50percent fuel if you want a slightly more reqlistic behavior

 

You want to be able to hover-takeoff at 3000 FPM instead of a mere 2400?

[fapador]

4 hours ago, SMH said:

You want to be able to hover-takeoff at 3000 FPM instead of a mere 2400?

I care for more realistic pedal inputs. I use the colective gently not like a car e/handbrake so dont care much if its not that accurate in that regime. I dont even know if in reality this would be even possible as the rotor rpm might drop as the disk loading increases too abruptly.

[fapador]

Also without being SME on rotorcraft (I am a fixed wing pilot). 2400 fpm at max torgue doesn't sound extreme for a military helicopter. I might be wrong though, maybe @Tim_Fragmagnet will know better as I havent researched this aspect a lot.

[Tim_Fragmagnet]

3 hours ago, fapador said:

Also without being SME on rotorcraft (I am a fixed wing pilot). 2400 fpm at max torgue doesn't sound extreme for a military helicopter. I might be wrong though, maybe @Tim_Fragmagnet will know better as I havent researched this aspect a lot.

He's asking for climb rate with no forward velocity.

Forward velocity reduces required engine power, the highest rate of climb velocity is when the engine uses the least amount of power for level flight.
For the huey that's between 55-65 knots.

@SMH This is the last time I reply to this argument.

However vertical rate of climb has no data available due to how it is made irrelevant by forward velocity.
What we do have, however, is thrust data. We can actually acquire vertical acceleration.
The OGE hover chart stops recording at 45 Ct, which equates to  12,834.0783692lbs of thrust.

Force = mass x acceleration
ie
acceleration = force/mass
so we can get acceleration in Gs from thrust/mass
so  12834.0783692/7500=1.7112104492266666666666666666667G
subtract 1 G for the force of gravity
1 G = 1930.4429751599998FPM/S
thus 0.7112104492266667G = 1372.95FPM/S

meaning with that much thrust, the huey at 7500lbs should be able to accelerate vertically, to a rate of climb of 1372.95FPM within 1 second.
However this does not provide us possible rate of climb, as the act of air rushing through the rotor vertically, changes things, and momentum exists as well, as does parasite drag.
it's not a simple question.

however, we can lazily estimate one

working backward on the hover chart, we can see that at 9500lbs, (a Ct of 33.30975452) we have a Cp of about 22.9, ( 966.9629541shp)
Thus hovering takes  966.9629541shp from the engine.
So if we proceed up to a Cp of about 35.3 ( 1490.558615shp (yes that's above its rated 1400shp, it's complicated, one engine pushed 1900shp in testing, the power it is rated for is not the maximum power it can push as that changes with atmospherics etcetcetcetc))
1490.558615-966.9629541=523.5956609

THUS, as per


predicted vertical velocity = 523.5956609 x 33000 / 9500
1,818.8fpm at 9500lbs

How about we do this for 7500lbs (a Ct of 26.29)
thus a Cp of what looks to be about 17.7, a shp of  747.3905802.
1490.558615-747.3905802=743.1680348
thus
743.1680348 x 33000 / 7500=3,269.9fpm

but we know that's wrong, because the increase in power creates an increase in torque, creates in increase in left pedal requirement, which creates an increase in the amount of power taken by the tail rotor, thus a decrease in the amount of power available to the main rotor.

That is the Nm in the formula, mechanical efficiency which for the above formulas was assumed to be perfect, which it's not.
Which is another thing to calculate, and EVEN IF WE HAD IT.





OK SO LETS DO THE MOMENTUM ANALYSiS
null



OH BUT WE ALSO HAVE TO ANALYZE THE BLADES
 

ENOUGH OF THIS

That's enough. I'm not going any farther right now. There's a reason my next thread is taking so long, because it's about actual full on flight dynamics and each individual error's compounding effects on the whole flight model.

Do I believe the rate of climb with no forward velocity is correct
NO, I don't. Of course I don't.

but it doesn't matter right now, because so many other things are wrong that trying to fix the rate of climb before then is literally just a waste of time and effort.

The aircraft doesn't even perform properly in a hover.
If it doesn't perform properly in a hover, of course it doesn't perform properly in a climb at ANY speed.

Fixing rate of climb, first requires fixing hover.
THEN when it starts climbing like a rocket because of the correct thrust values provided by the rotor, you fix the OTHER PROBLEMS that cause this.


AS PER YOUR OWN WORDS

Quote

and you don't seem to grasp through your spec tunnel-vision that you can't just change one part of this model without needing to change every other part.

How about you take your own advice. Realize that these things all compound into each other. Fixing ONE, requires FIXING MANY OTHER THINGS.
Just because fixing one thing breaks something else, does not mean that fixing that one thing is the reason that second thing is broken.

I'm not replying to this poorly thought out argument anymore.

I have research to do.


Mods, if you have to, lock this thread. Its point has long since been made.
I'm just going to make another one the next time a rework happens anyway.

Edited October 11, 2023 by Tim_Fragmagnet

[SMH]

Good! Please stop spamming the thread with it and go fly the thing and then tell us it's not ridiculous. 

(By the way, still waiting for that video of a Huey doing that, in any fuel-state. But we all know I'll be waiting forever because they don't do that.)

7 hours ago, fapador said:

I care for more realistic pedal inputs. I use the colective gently not like a car e/handbrake so dont care much if its not that accurate in that regime. I dont even know if in reality this would be even possible as the rotor rpm might drop as the disk loading increases too abruptly.

R/C modelers call this "flying scale". While it's a thing in their hobby it absolutely is not one in ours. And there's no need to yank it, you can be as gentle with it as you want, it'll still climb straight up at 2400 FPM with 100% fuel and torque and temperature within limits. (And you actually can't move the collective or any other control input faster than is plausible in real life, that's a feature of all DCS aircraft.)

Edited October 12, 2023 by SMH

[lassekongo]

1 hour ago, SMH said:

Good! Please stop spamming the thread with it and go fly the thing and then tell us it's not ridiculous. 

(By the way, still waiting for that video of a Huey doing that, in any fuel-state. But we all know I'll be waiting forever because they don't do that.)

R/C modelers call this "flying scale". While it's a thing in their hobby it absolutely is not one in ours. And there's no need to yank it, you can be as gentle with it as you want, it'll still climb straight up at 2400 FPM with 100% fuel and torque and temperature within limits. (And you actually can't move the collective or any other control input faster than is plausible in real life, that's a feature of all DCS aircraft.)

 

You dont know what you are talking about

[Tom Kazansky]

Tim has made the point: the FM isn't correct (enough) yet, and they are working on it. In a very comprehensive way imho.

What more can we ask for?

Let's move on.

[BIGNEWY]

Folks talk about the the UH-1H performance changes here, if you want to moan about development it will be considered off topic and deleted. If you have added your thoughts already and data please just give us time. 

1.10 Product feedback and constructive criticism is encouraged when provided in a mature and courteous manner. However, feedback that is abusive, insulting or condescending is not welcome. Additionally, to bring up a particular issue repeatedly after it has already been acknowledged will be considered "trolling" - in such cases a warning will be issued to the author and the post will be removed.

[lassekongo]

In Tim we trust

[=RS= Hart]

Tim is the only person outside of a Bell aircraft engineer, or actual Huey pilot I trust regarding the DCS module at this stage, dude's grasp of the mechanics, how the data presents itself, and how to apply it to DCS makes me wish I'd payed more attention in maths 

[MoleUK]

I will say the fact that ED gave us the option to enable the old engine system while the new stuff is being worked on deserves some praise.

Might it have been nice to have it as a tickbox in special options? Sure. But the idea that the userbase isn't capable of opening stuff up in notepad and changing some basic values is nonsensical.

I would LOVE for ED to take this approach with other stuff that is a WIP, letting us disable it without breaking IC while it's being worked on is much appreciated. Hopefully the second pass nails some stuff down, but i'm still very much enjoying the Huey in the meantime even with it's current oddities.

Edited October 15, 2023 by MoleUK

[fapador]

If only, ED improves Engine model according to advice given by @Tim_Fragmagnet  the DCS Huey has the potential of becoming one of the best helicopter FM for household pc simulation the world has seen to date. 

The biggest problem for me with the fm so far is:

A: All the problems tim has mentioned already regarding performance

B: The slip indicator not working properly

C : mast bumping  and rotor seperation occuring way too easily. Although this might get fixed as a byproduct of the above adjustments (I suspect it might have something to do with incorrect lift/thrust causing incorrect disk loading unloading and causing mast bump). As of now its impossible to perform these maneuvers shown in this video here (pushover seems doable with no airspeed)  and any aggressive flying generally...

Ps @SMH this is a great video (mind the low vhs quality) showing  powerful climb rates with zero airspeed in various segments... Watch from the start.

I think it might change your misconception regarding this behavior.

Edited October 16, 2023 by fapador

[SMH]

12 hours ago, fapador said:

Ps @SMH this is a great video (mind the low vhs quality) showing  powerful climb rates with zero airspeed in various segments... Watch from the start.

I think it might change your misconception regarding this behavior.

 

What are you talking about? He never climbs out of ground effect. 

Thanks for wasting 4 minutes of my life. I'll be ignoring you from now on.

[NineLine]

1 hour ago, SMH said:

What are you talking about? He never climbs out of ground effect. 

Thanks for wasting 4 minutes of my life. I'll be ignoring you from now on.

Friendly note, you could respond to and convey your disagreement without being so rude. Thanks.

[HILOK]

15 hours ago, fapador said:

If only, ED improves Engine model according to advice given by @Tim_Fragmagnet  the DCS Huey has the potential of becoming one of the best helicopter FM for household pc simulation the world has seen to date. 

The biggest problem for me with the fm so far is:

A: All the problems tim has mentioned already regarding performance

B: The slip indicator not working properly

C : mast bumping  and rotor seperation occuring way too easily. Although this might get fixed as a byproduct of the above adjustments (I suspect it might have something to do with incorrect lift/thrust causing incorrect disk loading unloading and causing mast bump). As of now its impossible to perform these maneuvers shown in this video here (pushover seems doable with no airspeed)  and any aggressive flying generally...

yes +1 ! absolutely A + B, then maybe C 

[fapador]

4 hours ago, SMH said:

What are you talking about? He never climbs out of ground effect. 

Thanks for wasting 4 minutes of my life. I'll be ignoring you from now on.

0:17. He ascents aggresively...  . You are right on this, he doesnt get out of ground effect perhaps entirely* but why does that exactly matter to you?

* Ground effect region is usually 1/2 rotor diameter

I am sorry if you didnt find the video interesting. Next time I will make sure not to disturb  by tagging you and save you the trouble of ignoring me...

[BIGNEWY]

Folks again be nice to each other. 

If you can not we will just shut this thread down. The back and forth between some of you serves no purpose to this thread. 

Tim has already given us enough to look at and it will take time. I suggest you all take a break. 

[NineLine]

I tried, but this has become more of a petty disagreement between users rather than a continued helpful bug report. Some things have been reported. When there is more news we will share. If you find something different wrong with the FM, feel free to make a proper bug report. Thanks.