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DHC-6 Twin Otter development

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Re: DHC-6 Twin Otter development

Postby it0uchpods » Mon Oct 23, 2017 2:50 pm

Try this version: http://www.github.com/FGMEMBERS/DHC6

I recently made some fixes to it.

Kind Regards,
Josh
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Re: DHC-6 Twin Otter development

Postby wkitty42 » Mon Oct 23, 2017 3:53 pm

Trennor_ wrote in Mon Oct 23, 2017 2:30 pm:I am very annoyed with this aeroplane. Downloaded revision 3058 yesterday via svn.

looking at my update logs, i, too, have svn revision 3058 which i downloaded two days ago (on the 21st) but it didn't bring any changes to the dhc6... none of my last 10 updates have brought any changes to the dhc6... digging deeper shows that the last changes for this craft were pulled 11 months ago... nothing is shown newer than then... the files listed below are the newest ones for this craft...

Code: Select all
2017 Oct 23  11:47:42 -0400
myuser@mymachine:~/flightgear-dev/fgaddon-ng/Aircraft/dhc6$ find . -newermt '11 months ago' -type f
./dhc6-menu.xml
./dhc6-base.xml
./dhc6F-set.xml
./gui/dhc6.jpg
./gui/dialogs/about.xml
./gui/dialogs/options.xml
./dhc6-aircraft-data.xml
./dhc6-input.xml
./dhc6-help.xml
./dhc6-set.xml
./Splash_screens/dhc6S-splash4.png
./Splash_screens/dhc6S-splash5.png
./dhc6S-set.xml
./Models/DHC6.xml
./Models/Effects/skin-reflect.eff
./Nasal/systems.nas

2017 Oct 23  11:47:45 -0400
myuser@mymachine:~/flightgear-dev/fgaddon-ng/Aircraft/dhc6$ find . -newermt '10 months ago' -type f

2017 Oct 23  11:49:47 -0400
myuser@mymachine:~/flightgear-dev/fgaddon-ng/Aircraft/dhc6$


since you're on linux, try this... make sure you are not running the sim and delete ~/.fgfs/aircraft-data/dhc6.xml and see if that might help... this file contains aircraft settings that are saved at each proper exit of the sim... sometimes some settings may cause problems between versions... we've seen it with the c172p during its recent -detailed development... it can't hurt to try it... rename it if you want but just get it out of the way so the sim will recreate it at the next proper exit the next time you try flying the craft...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: DHC-6 Twin Otter development

Postby zacarias » Mon Oct 23, 2017 3:56 pm

The PAF hangar version works very well:

http://pattenflightgear.wifeo.com/dhc6-300-twin-otter.php
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Re: DHC-6 Twin Otter development

Postby Trennor_ » Mon Oct 23, 2017 4:16 pm

wkitty42 wrote:since you're on linux, try this... make sure you are not running the sim and delete ~/.fgfs/aircraft-data/dhc6.xml


That file doesn't exist on my system in that dir; as I'm using Launcher, is there somewhere else it may be? Thanks for the tip though. :D
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Re: DHC-6 Twin Otter development

Postby Trennor_ » Mon Oct 23, 2017 6:42 pm

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Re: DHC-6 Twin Otter development

Postby Thorsten » Tue Oct 24, 2017 5:24 am

I want to fly this airplane, but I don't want to have to put up with the BS I've had in the past several attempts to get this thing even started. I've been flying the DHC6 since Syd Adams first introduced into Flightgear, and never have I had the problems with it I'm having with it now.


Generally speaking, a lot has been added to it in terms of systems and failure simulation. So while the plane previously did 'just fly'. now it actually punishes you if you omit certain steps.

I've myself run into the 'frozen pitot tube' simulation once and, well, entertained the notion that the plane is buggy, but the reality is that I made the mistake when not switching the pitot tube heater on and got inconsistent airspeed and altitude readings as a result once I crossed a certain altitude threshold - which is pretty realistic.

I've found it an excellent plane once I operate it correctly though.

I had ONE successful flight late last night, ironically using Autostart of all things.


Which, admittedly, is suggestive of an omitted step when starting it manually.

Well, if you consider the addition of such system failure simulations 'B/S', then I suggest you just don't fly the plane but revert to the older version - I believe that will still run.
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Re: DHC-6 Twin Otter development

Postby zacarias » Tue Oct 24, 2017 8:28 am



I sent them a message. The linked is fixed now.
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Re: DHC-6 Twin Otter development

Postby Trennor_ » Tue Oct 24, 2017 8:47 am

Thorsten wrote:I've myself run into the 'frozen pitot tube' simulation once and, well, entertained the notion that the plane is buggy, but the reality is that I made the mistake when not switching the pitot tube heater on and got inconsistent airspeed and altitude readings as a result once I crossed a certain altitude threshold - which is pretty realistic.

I've found it an excellent plane once I operate it correctly though.


Granted, Thorsten, and thank-you for pointing that out. I admit now to the frozen pitot tube error; pilot error, "nut behind the wheel," call it what you will, and after my pitots thawed, AP came back and all was fine for the duration of the flight. I had forgotten that in the time I wasn't flying, and it came to me mid-flight, then I read your post where you kindly reminded me of this. :oops:

It doesn't explain though the other freeze-ups though: frozen brakes, engines that won't start after completing the checklists etc.
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Re: DHC-6 Twin Otter development

Postby Thorsten » Tue Oct 24, 2017 10:16 am

It doesn't explain though the other freeze-ups though: frozen brakes, engines that won't start after completing the checklists etc.


I can't comment on the specifics - my flight experience with the plane is limited, and I've never really looked into systems. But I can say that in general complex systems simulations will do that - the Space Shuttle will find a million ways of not working if you omit checklist items - including thrusters not firing because the fuel line heater was off and so on.

There's also the possibility that there are genuine bugs in complex models - in any case, the maintainer is the person to talk to, and, really, you have to enjoy these types of models, if you want to 'just fly' they're not for you.
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Re: DHC-6 Twin Otter development

Postby dg-505 » Tue Oct 24, 2017 11:21 am

Hi Trennor,

glad that you could resolve the problems with the Pitot heat :)

About your other problems:
  • No starting engine
    Are you sure that you have removed the engine covers? (I don't know if you completed the "Preflight inspection" checklist)
    If the engine covers are in place, the engine will not start at all!

  • Aircraft not moving when releasing the parking brake
    Maybe the wheel chocks are still placed and/or the tie downs are connected?
    Again, these elements are part of the "Preflight inspection" checklist!

When using Autostart, the procedure executes the items of the Preflight inspection checklist. That includes pitot tube covers, wheel chocks, and tiedowns.

So that may be an explanatoin why it works when you use Autostart, but doesn't work when you start manually.

Hope this helps.
Please report if my suspicions are correct ;)


Thanks

Jonathan
(current maintainer of the DHC-6)
It's not just a hobby. I'ts a passion: FLYING !!

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Re: DHC-6 Twin Otter development

Postby wkitty42 » Tue Oct 24, 2017 11:41 pm

Trennor_ wrote in Mon Oct 23, 2017 4:16 pm:
wkitty42 wrote:since you're on linux, try this... make sure you are not running the sim and delete ~/.fgfs/aircraft-data/dhc6.xml


That file doesn't exist on my system in that dir; as I'm using Launcher, is there somewhere else it may be? Thanks for the tip though. :D

if the file doesn't exist, then the sim hasn't been exited properly (use F10->File->Exit instead of the 'X' in the top right) after using that craft... there is nowhere else for it to be on a *nix system... but i see that this is unlikely to be the cause of the problem...

funny thing about realistic simulators, they're quite lifelike and real life problems can easily rear their heads in a realistic simulator... eg: frozen pitot, flooded engine, iced over windows, etc...
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: DHC-6 Twin Otter development

Postby Lydiot » Wed Oct 25, 2017 3:33 pm

Just a big thanks to the developers of this model. It's great!
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Re: DHC-6 Twin Otter development

Postby dg-505 » Sat Nov 18, 2017 4:04 pm

Heads up to all Twin Otter Pilots! :D :D

I have just commited one BIG update to FGADDON!
We now have a JSBSim variant of the Twin Otter, and a much more extensive simulation of various systems, especially the electrical systems with it's various buses, c/b's, bus tie, etc.

Because this was a massive intervention in this aircraft and it's files, I can almost guarantee that it is not 100 percent bug-free, so PLEASE TEST and report any errors and abnormalities here!
Thank you!


Known issues:
  • JSBSim variant has only the three landing gears as contact points. If you always land on the wheels, that's won't be a problem ;)
  • Due to my lack of knowledge and experience I couldn't figure out how to implement a realistic thrust reverse simulation in the JSBSim variant.
  • The flight behaviour of the JSBSim variant is quite unrealistic, again due to my lack of knowledge.

Have a nice flight and always happy landings
Jonathan :D
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Re: DHC-6 Twin Otter development

Postby Thorsten » Sat Nov 18, 2017 5:12 pm

This sounds lovely :-)

Due to my lack of knowledge and experience I couldn't figure out how to implement a realistic thrust reverse simulation in the JSBSim variant.


What do you have in terms of data? If you have nothing, you can probably just flip the engine orientation in the JSBSim FDM. If you have data on the force, you can pass the thrust through a filter. Or zero normal thrust and create an external force which does the reverser. There's multiple ways to skin that particular cat.
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Re: DHC-6 Twin Otter development

Postby AndersG » Sat Nov 18, 2017 6:55 pm

Isn't the DHC-6 a turboprop? Then thurst reverse is a propeller operation, i.e. the propeller pitch is moved in to the reverse (beta) region. It should just be a question of extending the propeller tables and adding a system to control the propeller pitch (outside the default constant speed behaviour, but you could add your own constant speed controller too).

An aircraft that implements reverse propeller pitch, but without a constant speed controller, is the Zeppelin NT (ZLT-NT).

There is a program called JavaProp that might be helpful for constructing propeller tables.
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