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DHC-6 Twin Otter development

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Re: DHC-6 Twin Otter development

Postby CaptB » Fri Jan 30, 2015 11:26 pm

Honzaku wrote in Fri Jan 30, 2015 11:09 pm:Hello,

You all have done awesome work, however you missed some small detail in propeller animation. The Twin Otter is equiped by free-turbine type of a turboprop engine. This kind of powerplant usually feathers the propeller if the engine is not running. So the engine spinup is starting with prop blades in feathered position and when the engine is already started the pilot or automatic control sets the prop to fine pitch. In your animation the propeller starts to rotate with fine pitch. That would be true for most single-shaft turboprops like older russian turboprops, Fokker f-27, Transall, Hercules etc.., but not for Twin Otter. See following videos:
Honza


It's just not simulated yet :) got some files and I'll see what I can do to integrate it if I have some spare time ( I still have my own project to work on )
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Re: DHC-6 Twin Otter development

Postby dg-505 » Fri Jan 30, 2015 11:39 pm

Honzaku wrote in Fri Jan 30, 2015 11:09 pm:The Twin Otter is equiped by free-turbine type of a turboprop engine. This kind of powerplant usually feathers the propeller if the engine is not running. So the engine spinup is starting with prop blades in feathered position and when the engine is already started the pilot or automatic control sets the prop to fine pitch. In your animation the propeller starts to rotate with fine pitch.

You're absolutely right, Honzaku, I know this. But the problem is that the propeller pitch is not (yet) animated. To animate this behaviour of the powerplant, you have to know, at which RPM the prop pitch is set from feather to fine pitch.
I think, then it is not very difficult to animate this, at least for a competent programmer. (Not for me... :roll: )
Do you know or have a rough guess about this RPM?
A mile of road will take you a mile, but a mile of runway will take you everywhere.

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Re: DHC-6 Twin Otter development

Postby lanbo64 » Sat Jan 31, 2015 1:26 am

dg-505 wrote in Fri Jan 30, 2015 11:39 pm:
Honzaku wrote in Fri Jan 30, 2015 11:09 pm:The Twin Otter is equiped by free-turbine type of a turboprop engine. This kind of powerplant usually feathers the propeller if the engine is not running. So the engine spinup is starting with prop blades in feathered position and when the engine is already started the pilot or automatic control sets the prop to fine pitch. In your animation the propeller starts to rotate with fine pitch.

You're absolutely right, Honzaku, I know this. But the problem is that the propeller pitch is not (yet) animated. To animate this behaviour of the powerplant, you have to know, at which RPM the prop pitch is set from feather to fine pitch.
I think, then it is not very difficult to animate this, at least for a competent programmer. (Not for me... :roll: )
Do you know or have a rough guess about this RPM?


When the engine is running on a stable idle RPM, it is fine pitch.

In real world, the RPM of DHC6 actually spins very fast from 0 to idle, and the human eyes would never feel it. This situation is same in this FGFS model. Therefore, I prefer to use a nasal dirty hack to just tweak (interpolate) the prop pitch animation to feather when is it not running.

If you still want to use complicated nasal codes or even recompiling the c++ codes to do a real degree (angle) of pitch animation for a constant RPM turbobprop, I have no idea how to do that. Or I know how to do that but do worry about the performance.
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Re: DHC-6 Twin Otter development

Postby Patten » Sat Jan 31, 2015 6:12 am

dg-505 wrote in Fri Jan 30, 2015 10:08 pm:
tauchergreg wrote in Fri Jan 30, 2015 2:55 pm:on the door you can see the text from the left side

Ah. Thats's a texturing problem.

Here is a small update.

Changes:
- Some details added: antennas, headlights for the landing lights, and others
- Texturing fix
- The door-closing sound of Patten's version was a bit delayed; that's also fixed: Now the closing sound is heard exactly then, when the doors close
- Some effects added like tyresmoke on landing (my first lines of nasal code, yeah! :mrgreen: ) and exhaust smoke when starting the engines.


Good job, tanks.

Image

Welds are not made? :)

Image
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Re: DHC-6 Twin Otter development

Postby lanbo64 » Sat Jan 31, 2015 6:34 am

Good eyes Patten! LOL

I am doing some cleaning work. The model has some useless vectors, and I will fix this glitch.

Image
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Re: DHC-6 Twin Otter development

Postby Honzaku » Sat Jan 31, 2015 6:58 am

dg-505 wrote in Fri Jan 30, 2015 11:39 pm:
Honzaku wrote in Fri Jan 30, 2015 11:09 pm:The Twin Otter is equiped by free-turbine type of a turboprop engine. This kind of powerplant usually feathers the propeller if the engine is not running. So the engine spinup is starting with prop blades in feathered position and when the engine is already started the pilot or automatic control sets the prop to fine pitch. In your animation the propeller starts to rotate with fine pitch.

You're absolutely right, Honzaku, I know this. But the problem is that the propeller pitch is not (yet) animated. To animate this behaviour of the powerplant, you have to know, at which RPM the prop pitch is set from feather to fine pitch.
I think, then it is not very difficult to animate this, at least for a competent programmer. (Not for me... :roll: )
Do you know or have a rough guess about this RPM?


The pitch should change from approx. 90deg (feather) to fine pitch (probably around 5 - 10 degs) when pilot moves prop lever from feathered position to some working position (for taxiing and takeoff surely full fine). This occurs in rather high rotational speed, when prop is substituted by rotating bllured disc in animation anyway, so I dont thing the exact animation of this is required.

If you wanted to do so it shouldnt be too difficult from the modelling angle of view but from the information angle of view. You would need the prop characteristic (thrust and power coefficient vs. advance ratio for different blade pitch) and the engine characteristic (shaft power curves of engine). Than you have to re-code the JSBSim bulit-in model of propeller and turboprop engine to some yasim fríendly form and write at least simple P regulator to simulate prop governor....

Cheers

Honza
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Re: DHC-6 Twin Otter development

Postby lanbo64 » Sat Jan 31, 2015 8:18 am

Hi all,

Here is my latest build: https://drive.google.com/file/d/0B1TXYE8yc_ktTVRIOE8xU28xNlk/view?usp=sharing

I am sorry that I cannot export the dhc-6.ac correctly, so I cannot help to fix some 3D glitches at the moment.

A small history (including this update log) :
For better development and contribution, in this post, I list the files I changed here (from old that day I touch this model from Patten's website), and what they are doing, and why I change them:

1) dhc6.xml
Yes, I changed the Yasim. I downgrade the engines' flat-rating power to alt 4700 ft. This is a golden key for get a correct torque number in your Torque PSI instrumentation. I also change the Cruise speed at 25000 to 172 TAS for more realistic performance at high altitude.

2) dhc6-base.xml
Every time I added nasal codes, I will definitely modified it. Therefore, if you use my build but use your own or others' dhc6-base.xml, some codes may not work well.

3) Nasal/Electrical.nas
I added something about engines start at the very beginning when I was on this forum. This is a good old history.

4) Nasal/systems.nas
I know somebody wants to kill me because I wrote a bad code for autostart. But now, in the current update, it works better.

5) Nasal/printGforce.nas
This is a simple code to print your landing quality. It used to work bad, but in the current update, I simplified it a lot. I clean it for better performance.

6) Nasal/failures.nas
Somebody want to kill me because they burned their engines and iced their propellers and pitot tube. Deal with it...

7) Nasal/t5.nas
A more realistic T5. Actually, you are very hard to burned your turbine in this aircraft. If your torque psi is lower than 50 and the T5 is lower than 695, you can even push your power to full (MCP) for better climbing rate.

8) Nasal/torque.nas
This is the code which works with the dhc6.xml yasim together. The yasim give us a basic torque number, but I use this code to tweak it and add more outside influence to it. For example, the airspeed, the heaters, and the intake deflectors would influence it. This is why you cannot delete this file or use the original yasim, unless you know what you are doing.

9) Nasal/direction-gyro.nas
This is the first realistic gyro heading indicator simulator in the world. Yes, in the world. It has transport wander, earth rate wander, and latitude nut influences (no lat nut in this aircraft, but you can port to other aircraft) . I read a lot of real world ATPL exam papers before coding this one.

10) Nasal/earth-rate.nas
This one is new in current update. It feeds the earth rate wander and transport wander every 0.1 second to the directional-gyro.nas. It is a "slow-to-fast" coding method for better CPU performance. It means that, the direction-gyro.nas is a fast loop, so it should be simple. In contrast, earth-rate.nas is a slow loop, it runs every 0.1 second, but feeds a lot of important data and it is more complicated.

11) Nasal/smoothAnimate.nas
When the AP engaged, the yoke animation will be more smooth. It will NOT influence neither the AP performance and your manually control.

12) systems/autopilot.xml
A good old history too... pitch-for-speed system, hdg follow my direction-gyro, and alt hold follow the pressure altitude or QNH rather than GPS position.

13) Model/Flightdeck/flightdeck.xml and flightdeck.ac
I used to added a lot of things to it, but it is not very clean. Patten cleaned it very well. So I completely merged. However, in the current update in this post. the smoothAnimate.nas feeds data to the yoke, so there are two conditions have been added to flightdeck.xml. It will not influence anything if you don't like to merge this update.

14) Model/Flightdeck/No-smoking
I used to put a bloody light box, but I am not a good artist, so Patten pick it up for me. : )

In conclusion, this is just a history log. If you have problem after merging, please read which files you need or not. If you have any question about fly, control, or manage this aircraft, feel free to ask. If have any problem in old school navigation skills, please also feel free to ask.

Have fun!

Sincerely,
Bo
Last edited by lanbo64 on Sat Jan 31, 2015 7:35 pm, edited 1 time in total.
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Re: DHC-6 Twin Otter development

Postby dg-505 » Sat Jan 31, 2015 9:49 am

Patten wrote in Sat Jan 31, 2015 6:12 am:Welds are not made? :)


Oups, thanks for the hint, I didn't notice that at all.
A mile of road will take you a mile, but a mile of runway will take you everywhere.

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Re: DHC-6 Twin Otter development

Postby Patten » Sat Jan 31, 2015 2:34 pm

dg-505 wrote in Sat Jan 31, 2015 9:49 am:
Patten wrote in Sat Jan 31, 2015 6:12 am:Welds are not made? :)


Oups, thanks for the hint, I didn't notice that at all.


No problem, everything is ok. :wink:
I put the last change in my hangar tonight or tomorrow (in France).

Image

:D
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Re: DHC-6 Twin Otter development

Postby dg-505 » Sat Jan 31, 2015 3:31 pm

Patten wrote in Sat Jan 31, 2015 2:34 pm:I put the last change in my hangar tonight or tomorrow


Wait with the upload, shortly I'll give you a link with the fixed weld, and also I've integrated CaptB's propeller system. Then you can upload this into you hangar, too.
A mile of road will take you a mile, but a mile of runway will take you everywhere.

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Re: DHC-6 Twin Otter development

Postby tauchergreg » Sat Jan 31, 2015 4:53 pm

thanks for the RFdoor fixing :D

here is a Link for the BRT Liverie

Datei von filehorst.de laden

and can you edit some in the registation.xml for display 7digits

<text>
<name>RHreg</name>
<offsets>
<x-m>-0.310</x-m>
<y-m>5.5</y-m>
<z-m>1.09</z-m>
<roll-deg>0</roll-deg>
<pitch-deg>-3</pitch-deg>
<heading-deg>90</heading-deg>
</offsets>
<alignment>center-center</alignment>
<axis-alignment>reversed-xy-plane</axis-alignment>
<type>text-value</type>
<property>sim/multiplay/generic/string[1]</property>
<format>%0.7s</format>
<font>arial_black.txf</font>
<character-size>0.5</character-size>
<character-aspect-ratio >1.3</character-aspect-ratio>
<font-resolution>
<width type="int">128</width>
<height type="int">128</height>
</font-resolution>
</text>


for using the Saitek Yoke you can do this:

insert in the main folder

Datei von filehorst.de laden

insert in dhc6-base.xml

input section after keyboard
<joysticks>
<js n="1" include="Input/dhc6-Saitek-Yoke.xml" />
<!-- depending on your system -->
</joysticks >

in dhc6.xml

for better taxi-speed controling set n2-low-idle="30"


best regards
greg
C160 Transall , Twin Otter DHC6, both with small modification
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Re: DHC-6 Twin Otter development

Postby dg-505 » Sat Jan 31, 2015 5:33 pm

Finally, here is the update, including the fixed weld, all of lanbo64's nasal files and CaptB's new propeller: https://drive.google.com/file/d/0B2wA-loaS2xnT2dVZVNVbXhWbHM/view?usp=sharing
I tried to animate rotating wheels, but this turned out to be more difficult as I thougt, so that will be in a later update.
A mile of road will take you a mile, but a mile of runway will take you everywhere.

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Re: DHC-6 Twin Otter development

Postby CaptB » Sat Jan 31, 2015 6:38 pm

I'd like to work a bit on texture improving. Anyone working in that area?
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Re: DHC-6 Twin Otter development

Postby dg-505 » Sat Jan 31, 2015 6:48 pm

CaptB wrote in Sat Jan 31, 2015 6:38 pm:I'd like to work a bit on texture improving. Anyone working in that area?

Not from my site. Feel free to improve everything you want.
A mile of road will take you a mile, but a mile of runway will take you everywhere.

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Re: DHC-6 Twin Otter development

Postby henrikp » Mon Feb 02, 2015 7:52 am

First of all, I like the quality of the plane - big thanks to the developers. I haven't looked at the real checklists but shouldn't there be a notice about prop ice, pitot heat and intake deflectors somewhere? They are more or less present in the tutorial though. Found some reference material and could contribute, if someone hasn't done it yet.
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