Ground drag/friction & The NGX

[Sam 68]

Hello gents

So I stumbled upon this thread: http://forum.avsim.n...round-friction/

Someone in it created modification values for the sim1.dll for the ground friction

http://forum.avsim.n...n/#entry2534947

 

What are your thoughts on this 'find' and how reallistic do you think the NGX currently handles the ground friction problems of fsx

 

Here is my post on my experience using the tweak in FSX accelleration with the NGX

 

I where on the PMDG 737-700WL and used this tweak.

The aircraft was loaded trough the FMC with a 33% fuel (1/3 load) and 82% payload.

When advancing throttles it was like, the aircraft moved before I touched the controls.

To get some data I advanced throttles again to 40% n1 with the GS at 2-3.

When the engines stabalized at 40% n1 I brought them back to idle. The acceleration stopped at 26 GS.

 

With throttles at idle (Confirmed using F1 on keyboard) the GS slowly increases nothing bad.

Takeoff seemed realistic.. I really think so.. Wasent any unreal accelleration I think.

Took a turn with 25 GS.. a 80 degree one.. so the "bambi on ice" effect is surely better.. I still think there is something which is way off(not that my turn is anything real, should have been in the grass).. but still seems a bit "icy"

The landing:

I think the landing was great.. Didn't roll unrealistic imo.. ofc im not an NG pilot, or even a pilot at all but I can accept is at pretty real

Can someone with real piloting experience comment on this data?

I find it slightly over the top when taxing.... Maybe decrease it just a wee bit.

 

Taxied a bit in the 737-800 fully loaded fully fueled.

 

Started moving significally at 24% n1

the 40% n1 stabillization test got me to a gs of 16

The GS decreases slowly at idle.

 

Again comment from a RW NG pilot would be great to point the 'author' in the right dir.

 

here is the DL for accel

 

http://forum.avsim.n...25#entry2536372

 

You MUST download the file for your version (SP1/2/accel)

Would be ncie to find the NGX value for this, Pete dowson will include it in fsuipc soon

[scandinavian13 5,192]

None of the aircraft handle very well because the ground friction model is pretty messed up in FSX in general. Look carefully when you turn any aircraft. You'll note the nose wheel is usually turned more inward than the actual rate of turn (no matter the speed).

 

For what it's worth, you're quoting a guy who is using a butt dyno*. His only real 'data' is that it "feels/seems/etc realistic." Sure, there are numbers there, but there are no direct comparisons to how the real aircraft would behave. I'd hesitate to edit anything based on the suggestion of someone who said himself is neither a pilot of the aircraft, or a pilot at all, who is claiming something pertaining to operating an aircraft feels realistic.

 

*Butt Dynamometer - a term used in the car world to describe someone's testing by the seat of his or her pants, and not by using actual metrics.

e.g.: "Man, I installed a new air intake and my car totally feels a lot faster!"

See Also: Placebo effect

[Johan_Dees 84]

Maybe I didnt published it yet or complete, but you dont need to be a pilot to see it. Sorry for that.

 

http://forum.avsim.net/topic/392772-inherent-flaw-of-fsx-to-give-too-much-ground-friction/page__st__75#entry2537451

 

They (MS) used 0.055 where they should be using 0.025. And it only feels better, its actually working better.

[Sam 68]

None of the aircraft handle very well because the ground friction model is pretty messed up in FSX in general. Look carefully when you turn any aircraft. You'll note the nose wheel is usually turned more inward than the actual rate of turn (no matter the speed).

 

For what it's worth, you're quoting a guy who is using a butt dyno*. His only real 'data' is that it "feels/seems/etc realistic." Sure, there are numbers there, but there are no direct comparisons to how the real aircraft would behave. I'd hesitate to edit anything based on the suggestion of someone who said himself is neither a pilot of the aircraft, or a pilot at all, who is claiming something pertaining to operating an aircraft feels realistic.

 

*Butt Dynamometer - a term used in the car world to describe someone's testing by the seat of his or her pants, and not by using actual metrics.

e.g.: "Man, I installed a new air intake and my car totally feels a lot faster!"

See Also: Placebo effect

 

It is my own post i quoted.. Not that it makes your point any less true

 

But it does Work tis just wether The data is more accurate or not.

[scandinavian13 5,192]

But it does Work tis just wether The data is more accurate or not.

 

Right, but with a little tweaking, I can make the 737 fly like an X-15 if I wanted.

That would work, whether the data is more accurate or not, too.

[jbassue 181]

Right, but with a little tweaking, I can make the 737 fly like an X-15 if I wanted.

That would work, whether the data is more accurate or not, too.

Obviously we can never match the real flying experience, but through experimenting and implication, we can come pretty close.

This is a perfect example, I downloaded this file a while back and I can confirm that it works, as subtle as the change is. You should try it out Kyle. No Placebo here.

[Alec 370]

I have tested this with PMDG 737NGX, and it's achieving inaccurate Takeoff Distance, the aircraft takes a lot more runway to get to V1 without this MOD. So this is going to make the 737 feel better while taxing, but totally unrealistic during Takeoff.

 

Now we have to see if Developers will adapt their addons for this fix, or they'll pretend it never existed and anyone who wants can tweak their own files.

[Houghton11 12]

I have tested this with PMDG 737NGX, and it's achieving inaccurate Takeoff Distance, the aircraft takes a lot more runway to get to V1 without this MOD. So this is going to make the 737 feel better while taxing, but totally unrealistic during Takeoff.

 

Now we have to see if Developers will adapt their addons for this fix, or they'll pretend it never existed and anyone who wants can tweak their own files.

 

I should mention that some users of Saitek Pedals get some funny phantom braking going on, and this was a result of long t/o runs for me. I'd check that as well.

[Alec 370]

I made my test completely clear of any interference. I loaded the Flight Scenario for the Second Tutorial, Before Takeoff. Then I waited for engines to establish and pushed the TO/GA Button, when it reached V1 I paused and took a look from Top View, so there's no way anything other than Sim1.dll could cause the Distance to change.

 

Oh, and I didn't have any joystick connected, only keyboard and mouse.

[Sam 68]

Right, but with a little tweaking, I can make the 737 fly like an X-15 if I wanted.

That would work, whether the data is more accurate or not, too.

[michal 44]

They (MS) used 0.055 where they should be using 0.025.

I can only confirm that 0.025 is much closer to what engineering aviation books and scientific papers report than 0.055. For example Flight Theory and Aerodynamics - a Practical Guide for Operational Safety 2nd. ed. by Charles E.Dole and James E.Lewis on page 193 says that for dry asphalt/concrete runways a typical rolling coefficient of friction is 0.02. This is not the only source, others report similar range, An Introduction to Aircraft Performance by Mario Asselin reports the same 0.02, book by Steven A. Brandt gives range 0.02-0.04. If MS uses 0.055 then they are away from the 'sweet' spot.

[Alec 370]

But how come we know MS based this values to the same coefficient of frictions in real life? They did get so many things wrong, maybe this one requires too a lot of testing before just using Real World Numbers. It has been that way with most of the values used in Addons.

[ajpongress 467]

None of the aircraft handle very well because the ground friction model is pretty messed up in FSX in general. Look carefully when you turn any aircraft. You'll note the nose wheel is usually turned more inward than the actual rate of turn (no matter the speed).

 

For what it's worth, you're quoting a guy who is using a butt dyno*. His only real 'data' is that it "feels/seems/etc realistic." Sure, there are numbers there, but there are no direct comparisons to how the real aircraft would behave. I'd hesitate to edit anything based on the suggestion of someone who said himself is neither a pilot of the aircraft, or a pilot at all, who is claiming something pertaining to operating an aircraft feels realistic.

 

*Butt Dynamometer - a term used in the car world to describe someone's testing by the seat of his or her pants, and not by using actual metrics.

e.g.: "Man, I installed a new air intake and my car totally feels a lot faster!"

See Also: Placebo effect

 

He quoted himself.

And I've tried the updated sim1.dll and it does change the ground friction mechanic. Why don't you backup your own file, try the new one and check the results for yourself before knocking it with your usual sarcasm?

[scandinavian13 5,192]

Why don't you backup your own file, try the new one and check the results for yourself before knocking it with your usual sarcasm?

 

Because I have to stick to my MO...

And despite your own preconceived notions, I wasn't being sarcastic. My point was 100% serious. I'm not going to simply throw all caution to the wind because someone - who admitted himself has never controlled a real aircraft - said that it "feels" more realistic.

 

After that, I responded to the point that "it works." So does a nail gun pointed at my face if I hold the pressure sensor down.

 

Nothing sarcastic about any of those responses. Just putting the points out there.

 

Nowhere in there did I say it was incorrect, or completely stupid. I simply pointed out that it working and feeling correct aren't exactly the greatest measures to say it's accurate?

 

 

 

So, instead of jumping down my throat, if you're really concerned about backing someone up, how about doing something useful like providing hard evidence?

[ajpongress 467]

Ha I didn't jump down your throat. I said try something before criticizing it.

I also said that it changes the ground friction, but I didn't specify if it was better or worse. I don't need hard data to say the values in the file actually change.