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Re: New MD-11 Development

Postby Lincoln » Tue Apr 28, 2020 8:02 am

MD-11 for best plane in FG :)
Currently flying the 737-800YV / MD-11-GE / 747-400

GE90-115B for life!

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Re: New MD-11 Development

Postby Octal450 » Mon May 04, 2020 3:46 am

OK so.
I finally after many many hours of work figured out how to get around this stupid FGTurbine problem.
Let me explain.

FGTurbine assumes that rated power = max N1/N2.... but this is a bullshit thing. Not realistic at ALL.
I will use N1% here as reference since that is what the GE engines use (PW use EPR) and I started with the GEs cause they are simpler and I have more data on them.

In 30C at sea level, 111.7% N1 is rated thrust. Not the max N1 of 117.5. in fact, you can bypass maximum rated thrust by the overboost bar or ALTN FADEC mode (simulated). So custom calculations are used to make the correct thrust amount. This is done "smartly" so that the thrust still is proper at various altitudes/mach, but now temperature and proper scaling is done.

I still have a lot more work, porting the FADEC into JSBsim completely. I did program in new thrust limits which are more accurate to the real thing as well... and FINALLY the MD-11 is no longer underpowered! It climbs like it should!

I do have to check the drag though, I think a few things are wrong and were done because the engines were weak (and I didn't know why at the time)

And when the entire GE is done, I will do PW with EPR. For now its in the branch "engines", but I warn you this is not stable for flying!

Kind Regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

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Re: New MD-11 Development

Postby Octal450 » Wed May 06, 2020 10:08 pm

Image
Its coming..... trust me...

but I'm warning - once some FMS pages work, the plane will get more restrictions on A/P requiring some FMS inputs and such to even function at all.

Kind Regards,
josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

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Re: New MD-11 Development

Postby Gijs » Thu May 07, 2020 9:36 am

Hi Josh,

Octal450 wrote in Mon May 04, 2020 3:46 am:I finally after many many hours of work figured out how to get around this stupid FGTurbine problem.

Thanks to Jonathan I discovered the 744 had the same issue. While designing my own solution (pleasantly similar to yours it seems), I noticed my MilThrust table was quite wrong. High bypass turbofan engines have a rather big decrease in thrust when speed increases (at low altitudes), which was not properly reflected in the table. This lead to excessive thrust actually, which may have obfuscated the rated thrust issue...

I've fine-tuned my table to an aircraft design document now which nicely matches the limited curves that I've found in some GE sources. The MD-11 has a different variant of the engine of course, but I'd expect the MilThrust tables to be similar.

Image

I still need to do some more cleanup and cross-checking, but initial flight tests seem to be quite promising with correct cruise speeds. I'll let you know once I've pushed it to FGAddon in case you want to try the new table on the MD-11, before you start make changes to the drag based on the engine power.

Thanks a lot for finding the root issue!

Regards,

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Re: New MD-11 Development

Postby Lincoln » Thu May 07, 2020 10:26 am

Great news! :)
Currently flying the 737-800YV / MD-11-GE / 747-400

GE90-115B for life!

Follow me to the sun on SXS98X!

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Re: New MD-11 Development

Postby Octal450 » Thu May 07, 2020 2:47 pm

Hallo Gijs,
Thx for that info! The difference between B1F and D1F appears to be rated thrust only, that's really it! (and maybe some minor things). I would love to use your table.

My solution involves calculating what the MilThrust "should" be at the N1 setting for rated thrust, then calculating what FGTurbine's wrong amount would provide at that setting, and using that quotient as factor to adjust the actual engine's MilThrust. It works quite well, at 111.7% N1 at 30C Sea Level, I am within 200lbs of the rated power!!! :)

So your table would compliment this correction well. I would much look forward to that! I would also be appreciative if I could have the source data you used for your table, for research purposes.

Kind Regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

My GitHub|MD-11 and ITAF Dev Discord|Airbus Dev Discord
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Re: New MD-11 Development

Postby Lydiot » Thu May 07, 2020 2:57 pm

Josh,

Thank's so much for working on this and sharing!
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Re: New MD-11 Development

Postby Octal450 » Thu May 07, 2020 5:54 pm

Lydiot,
My pleasure!

Kind Regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

My GitHub|MD-11 and ITAF Dev Discord|Airbus Dev Discord
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Re: New MD-11 Development

Postby Octal450 » Wed May 13, 2020 5:34 pm

Made the following updates to the MD-11:
- GPWS fixed (thx legoboyvdlp)
- Fixed FADEC response
- Fixed throttle position markers on EAD
- Fixed reverse thrust too low
- Fixed bug in how ATS handles idle and thrust limits
- Adjusted roll and pitch aerodynamic response slightly

Kind Regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

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Re: New MD-11 Development

Postby Octal450 » Thu May 14, 2020 3:08 pm

Image
TAT now works on the EAD (engines branch only).

Anyways the GEs are nearing completion, just have to finish porting the rest of the FADEC logic and fix the idle limits. I will probably temporarily disable the PW engines, and merge this into master. Then I will do the PW FADECs.

Kind Regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

My GitHub|MD-11 and ITAF Dev Discord|Airbus Dev Discord
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Re: New MD-11 Development

Postby Octal450 » Sat May 16, 2020 1:17 am

More FADEC work today.
Fixed reverse thrust amount
Fixed behavior of some things.
Fixed EAD Throttle Target not showing in reverse thrust
Fixed yellow unlocked REV indicator showing "REV" instead of "U/L"
Optimizations

Kind Regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

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Re: New MD-11 Development

Postby Octal450 » Mon May 18, 2020 3:31 am

Engines branch:
- Completely refactored reverse thrust system, probably the most advanced rev thrust system in FG!
- Works with existing keybindings for MD-11, A320-family, Airbus_A330
- Engines 1 and 3 will open right away
- Engine 2 will sit on U/L (unlocked) until nose gear touchdown, then it opens
- Reverse thrust "T" is shown on the EAD to show the target N1 for that setting even when still on U/L
- The engines will spool down BEFORE they begin to close, and open all the way before spooling up (prevents damage)
- Fixed some other little bugs and quirks.

Assuming my next test flights with the new FADEC/Engines go well, it will be merged into master! Then I will start on the much more complex Pratt and Whitney FADEC.... :mrgreen:

Kind Regards,
Josh (MD-11 man)
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

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Re: New MD-11 Development

Postby wlbragg » Mon May 18, 2020 4:11 am

Josh, are you capable of recording a video demonstrating the engine reverse thrust on touchdown? That would be nice to see in a video!
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Re: New MD-11 Development

Postby LH-9920 » Mon May 18, 2020 12:21 pm

Thanks for continuing MD11 Development. For me it is one of the most exciting planes in FlightGear!
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Re: New MD-11 Development

Postby Octal450 » Mon May 18, 2020 1:47 pm

Hallo wkitty42:
Sure

Hallo LH-9920:
Glad to hear that!!

Kind regards,
Josh
What I do: Flight Dynamics, Systems, Canvas Displays, Autoflight, FlyByWire, Cockpit Animations
Aircraft I currently develop: MD-11 (Mainly), Secret, A320-family (Quality over Quantity)

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