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Announcing NEW Boeing 777 'Seattle' - Pre-Release

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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby V12 » Sun Apr 14, 2019 2:17 pm

Are You sure ? In .xml files I found friction definitions :
Code: Select all
<gear x="-6.39" y="5.6" z="-5.7" compression="0.8" spring="1.0" sfric="1" dfric="0.9">

When I changed sfric from 1 to 0.5 and dfric from 0.9 to 0.4, I obtained braking time 38 seconds what is 1800 meters of distance and almost 2 .5 m/s2 deceleration, much more realistic value. Probably, values 0.6/0.5 for sfrict/dfrict should be correct.
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Octal450 » Sun Apr 14, 2019 3:03 pm

That must be new since I last looked at yasim then. Hmm.
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby V12 » Sun Apr 14, 2019 6:19 pm

Some more details are here - viewtopic.php?f=49&t=33612&hilit=efficiency
Friction 0.5 give realistic deceleration around 3 m/s2
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby biloute974 » Mon Apr 15, 2019 5:40 am

Hi,
It's really nice, very good upgrade of the 777, thanks to all dev.
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Isaak » Mon Apr 15, 2019 8:50 am

Hi V12, thanks for pointing that out, now that you mention it I remember your topic of last year. I 'll take a look at it at last next weekend and see if I can get more realistic breaking action. I 'll look up some real data though, since I do want to simulate it as realistic as possible.

And thanks @biloute974 ;)
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby V12 » Mon Apr 15, 2019 8:54 am

Isaak :
For simulation as realistic as possible You will need convert 777 from YASIM to JSBSIM :(
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Isaak » Mon Apr 15, 2019 10:01 am

I know, but that definitly goes beyond what I 'm capable of at the moment. :) Don't be too harsh on the 777's YASIM FDM though, two years ago I did an unprepared training flight on a certified B738 fixed base simulator and I was able to land her as if I 'd done nothing else before. All my experience comes from flying the 777 in FlightGear, so it definitely doesn't behave thát unrealistic. It could be better, I agree, but it isn't rubbish either ;)
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Octal450 » Mon Apr 15, 2019 12:11 pm

Not really. All you needed was the basics of HOW to fly. The FDM itself did little to matter at that point. This one makes no sense from an aerodynamic point of view in many cases, which is partly why I abandoned my FBW attempt.

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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby V12 » Mon Apr 15, 2019 1:20 pm

Isaak wrote in Mon Apr 15, 2019 10:01 am:I did an unprepared training flight on a certified B738 fixed base simulator and I was able to land her as if I 'd done nothing else before.

I too. Perfect experience. Check viewtopic.php?f=3&t=35007
My landing was not absolutly perfect, but old good 737-800 NGX survived without any scratch.
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby V12 » Mon Apr 15, 2019 1:29 pm

it0uchpods wrote in Mon Apr 15, 2019 12:11 pm: All you needed was the basics of HOW to fly.

Correct, it is crucial. But when I compare circling approach to Quito in 707 or Concorde and Your Bus with FBW, it is great difference, with FBW it is much simpler.

Latest 777 flying much better than previous version, it is big step forward.
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Octal450 » Wed Apr 17, 2019 5:26 pm

Dear Isaak
You made a mistake a while back and I didn't notis -- when you implemented my changes, you didn't carry over my trim handler, hence joysticks trim is broken in the last FGAddon version. I make correction.

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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Isaak » Thu Apr 18, 2019 12:24 am

Sorry for the inconvenience, thanks for helping us out!
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Octal450 » Thu Apr 18, 2019 12:25 am

No worries :)
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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Octal450 » Thu Apr 18, 2019 3:52 am

Now the fix is in FGAddon trunk. All further updates from me thru launcher please when stable. Unstable changes by me probably in my github.

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Re: Announcing NEW Boeing 777 'Seattle' - Pre-Release

Postby Octal450 » Thu Apr 18, 2019 4:08 pm

Flight control laws done for Roll and Yaw. They aren't perfect, or have all features because YAsim... but they should be somewhat convincing.
It has the bank angle "protection", wheel forces applied after 35 bank. It can be overridden if you turn hard enough. If you let go, it will bounce back to around 30 degrees.
Outer ailerons lock at high speed, I tried to get it close to real life. I couldn't lock spoilers 5 and 10, because the 777 doesn't model the hydraulics currently, and the spoilers are together in the 3D. If someone wants to fix all that, I'll add that logic.
Yaw Damper/Turn Coordinator simulated. Because property rule doesn't have a good washout (there is a high pass, but it isn't right for this purpose), I tuned the turn coordinator to also act as a yaw damper. It works decently even in bad weather.
Rudder Ratio is simulated, including the 2 set ratios when PFCs are switched off.

Also
Just like in my IDG Airbus and MD-11, if you turn yoke while A/P is on, he will switch off. If you turn off PFCs, A/P turns off as well.

PFD sideslip no longer uses the generic instrument, but my calculations derived from FCOM.

If a JSB version ever is done properly, most of my code can be reused, which is good.

It is on my github 777 page shortly. I will work on the C*U pitch law next. I think I found a workaround for YAsim not allowing me to change the trim property and still keep trim ref speed somewhat correct.

When its all done, I'll need testing before I put it in FGAddon. Pavlin has agreed to do long hauls to test system stability.

It appears that the -200s have weird trim behavior, needing much to much nose down trim at all times. YAsim is weird, so I will set a trim bias for the 200s only, as the 300s trim is less weird. Maybe something to do with the hstab being more aft on the -300, and how YAsim calculates pitch moments.

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