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Helicopter woes

Helicopter flying is completely different from flying a fixed-wing aircraft and thus requires different skills.

Helicopter woes

Postby tduell » Sat Mar 28, 2009 4:53 am

Hullo All,
I am relatively new to FlightGear, so I am finding my way.
Firstly, what a wonderful open source program. Well done to all who have worked on it.
I have v1.0.0 installed on a Linux Fedora 9 x86_64 system, and am using a logitec Extreme 3D Pro Joystick. I should add that this is the latest version available for Fedora (9 or 10) as a package from the Fedora repositories.
I have been having some troubles with Helicopters, which is probably not unusual.
After much practice I have managed to get the bo105 flying, but it does seem to be quite a hit and miss business...more luck that good management.
After starting the engine the Torque settles to about 20%. I have my joystick 'throttle axis' (which I understand from wiki, docs etc to be the collective pitch) set at the most negative setting, and the 'copter sits OK awaiting input.
Adding collective pitch is severly non-linear. As I slowly add pitch nothing happens then at about 30% to 40% 'throttle axis' input the Torque immediately jumps to 110% to 120%. At this instant all hell breaks loose and the 'copter leaps into action, and if I'm lucky I can bring it under control. Mostly it is just 'crash and burn'!
This behaviour doesn't seem like real life, so is there something wrong with the physics model for this machine, something wrong with my joystick, or something else?
I should add that the joystick behaves quite nicely when flying fixed wing aircraft.
I have also attempted to fly the Alouette2, but that fails with the following message 'FATAL: ac_to_gl: Unrecognised token 'rep 1 1'. Does anyone else have the Alouette2 working OK on a Linux version of FG?
Cheers,
Cheers,
Terry
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Re: Helicopter woes

Postby Ineedhelp » Sat Mar 28, 2009 12:31 pm

Let me guess, it gets in the air and the body starts spinning real faster and tilting up and down until you crash, right? That happens to my brother in the Bo105 in Windows 1.9.1. I suggested the EC135 and he now loves it and can take off like a pro.(But not land.) So, try the EC135, it's easier to control. I did it with a mouse.
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Re: Helicopter woes

Postby Groucho » Sat Mar 28, 2009 3:38 pm

Ineedhelp wrote:Let me guess, it gets in the air and the body starts spinning real faster and tilting up and down until you crash, right? That happens to my brother in the Bo105 in Windows 1.9.1. I suggested the EC135 and he now loves it and can take off like a pro.(But not land.) So, try the EC135, it's easier to control. I did it with a mouse.


Somewhere in the change between 1.0 and 1.9.1 I some changes seemed to have been applied which make the Bo105 much more nervous than before at least with my setup, especially around the roll and nick axes.
Having flown most of the helicopters I have to say that the Bo105 now behaves even much more instable than the R22 on those axes (though not in other aspects:) )
As you said for starters the EC135 is propably fine.
The Alouette is definitely not for beginners. I am flying it regularly and it needs constant handling in all aspects.

About that throttle-pitch problem I have not encountered this but I would suspect the joystick is not calibrated or the potentiometers are a bit dirty.
Notifying this with fixed wing aircrafts is hard if you do not play with the throttle and leave it at a constant rate (as some virtual pilots do :) )
Last edited by Groucho on Sat Mar 28, 2009 7:56 pm, edited 1 time in total.
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Re: Helicopter woes

Postby redneck » Sat Mar 28, 2009 4:09 pm

I run on Windows and experience a similer problem with the bo105. Of course, it doesn't help that I have a digital throttle, which can only be changed in increments of 25%. I have found the Sikorsky S76C to be the easiest heli to fly. I don't have rudder pedals either. I use a $10 three-axis, three-button joystick with autocoordinate turned on. I'm usually lucky if I manage to bring control over the bo105, and even luckier if I manage to land without crashing. I found the EC-135 to be less easy than the S76C. It seems like the S76C has some kind of automatic torque compensation simulated. The R-22 and Aloute-II just tips over and crashes without even getting off the ground. I've also tried the Super Frelon and had a unique experience with that. I get it into the air, and then the tail rotor dies, leaving me to spin out of control for a couple of minutes until I come back down and crash.
If you have any trouble with the EC-135, I would definitely recommend the Sikorsky S76C. I always feel like I have full control over it, unless I'm doing more than 200 kts, and it's technically not supposed to go any faster than 150 kts, but that's not always fast enough for me 8)
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Re: Helicopter woes

Postby HHS » Sat Mar 28, 2009 8:27 pm

Groucho wrote:...
I am flying it regularly and it needs constant handling in all aspects.



All helicopters need it! A helicopter is naturally instable flying object and it has to be forced to fly!

Regarding tduells post it seems to me that the joystick settings are wrong. It doesn't seem that the throttle is linear- but is has to be, if you want to fly helis.
Then the helis are quite realistic- I read threads in X-plane forums and new users report the same ( now wonder- we use the same principe of simulating! ;-))
Helis need very small inputs- every input on one of three controls need adjustements on the other. Or like a german helicopter pilot once said: "flying an aircraft is like balancing a ball- easy. But flying a helicopter is like balancing a blall, which is balancing on another ball, and this finally balancing on a ball too.

For starting I recommend trying large helis like CH53E or the Aircrane, which can be found here in the forum. When you fly with mouse, you have to enlarge the sensitivity of it ( have a look how long the way of the stick in the bo105 is, and try to match that with the mouse). Still it needs very small inputs! Pedals would be also useful, but you can lay the rudder on the mouse wheel.

Btw: The bo105 in CVS now nearly 99% realistic and behaves like the original.

Regards
HHS
Last edited by HHS on Sat Mar 28, 2009 9:48 pm, edited 1 time in total.
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Re: Helicopter woes

Postby HHS » Sat Mar 28, 2009 9:47 pm

Here are some videos showing the Bo105 in Flight- you can see in each video the movements of the stick the pilot has to do- so you can compare it with FGFS!

http://www.youtube.com/watch?v=DtGq-Tf089s
http://www.youtube.com/watch?v=RHTroAhP5qE&feature=related
http://www.youtube.com/watch?v=id7Gz8AZ5j0&feature=related
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Re: Helicopter woes

Postby tduell » Sat Mar 28, 2009 10:26 pm

Many thanks to all who have replied.
Regarding the comment that my joystick may not be calibrated, that is something that I had tried but have fallen foul of the problem with the available version of plim for Fedora x86_64 and the calibration tool doesn't work. I also have FG 1.9.1 on an XP laptop, could I do a calibration on that and then use the resulting file in Linux?
Re. the ec135, I have downloaded that aircraft but it would seem that the Linux version of FG doesn't like some of the texture files. I get many messages like this...
[terry@phenom ~]$ fgfs --aircraft=ec135
WARNING: Converting textures not yet implemented under Linux.You may convert '/usr/share/FlightGear/Aircraft/ec135/Models/tail.dhecz.png' manually to '/usr/share/FlightGear/Aircraft/ec135/Models/tail.dhecz.rgb' and reload the model.

I have found all or most of the offending files and converted them to rgb format, but that has introduced a new problem! When I first start FG with the ec135 I get a normal view out the front screen. Soon after I start the engine the front screen goes opaque, so I am guessing that the conversion (possibly of 'glass_shader.png' in this instance) is not correct. I have been doing the conversion using Gimp which provides 3 possible formats, which are described as 'no compression', 'RLE compression', and 'Agressive RLE (not supported by SGI)'.
Can someone please advise what is needed here?

Cheers,
Cheers,
Terry
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Re: Helicopter woes

Postby MAKG » Sun Mar 29, 2009 1:35 am

HHS wrote:All helicopters need it! A helicopter is naturally instable flying object and it has to be forced to fly!


This one is inherently stable. Not that I'd like to fly on an oversized salad shooter....
Image
http://www.unrealaircraft.com/wings/hillier_platform.php
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Re: Helicopter woes

Postby Fahim Dalvi » Sun Mar 29, 2009 4:09 am

tduell wrote:I have been doing the conversion using Gimp which provides 3 possible formats, which are described as 'no compression', 'RLE compression', and 'Agressive RLE (not supported by SGI)'.
Can someone please advise what is needed here?
Cheers,


Hi,
While converting RGB-->PNG it doesn't ask me for any compression...! Anyway, AFAIK, its RLE Compression.
If you still have problems, i'l convert the file and then you can test it out!
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Re: Helicopter woes

Postby tduell » Sun Mar 29, 2009 5:34 am

[quote
"
Fahim Dalvi wrote:Hi,
While converting RGB-->PNG it doesn't ask me for any compression...! Anyway, AFAIK, its RLE Compression.
If you still have problems, i'l convert the file and then you can test it out!



The message suggested conversion PNG --> RGB. The PNG files are there, but only some RGB. I have since tried with and without RLE compression but none of it helps. I have been making copies, i.e I now have fred.png and fred.rgb, but I wouldn't have thought this would be a problem.
Having the RGB files has meant no messages re format conversion when run but with the RGB files I still get opaque screen/windows that are greenish in colour. Without the RGB files (i.e the aircraft files as downloaded from the website) the screen/windows go opaque red just after engine is started. Rotating the view shows some gaps at edges of windows through which the proper scenery can be seen, almost as if someone has stuck some film over the windows that doesn't quite fit. Does that give anyone a clue as to what might be happening here?

It does seem to me that there is some other problem with this aircraft when run on Linux FG, as I suspect that some instruments may be missing, but that is just a guess.

I should add that I am using a 9600 Nvidia card with the Nvidia driver.
A number of other aircraft work very nicely.

Is there anyone using FG V1.0.0 on Linux (x86_64) that has the ec135 helicopter displaying and working correctly? If so could you please tell me where you got your ec135 aircraft files, or what you had to do to get it all displaying/working correctly?

Cheers,
Cheers,
Terry
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Re: Helicopter woes

Postby AndersG » Sun Mar 29, 2009 11:45 am

tduell wrote:The message suggested conversion PNG --> RGB. The PNG files are there, but only some RGB. I have since tried with and without RLE compression but none of it helps. I have been making copies, i.e I now have fred.png and fred.rgb, but I wouldn't have thought this would be a problem.
...
I should add that I am using a 9600 Nvidia card with the Nvidia driver.
A number of other aircraft work very nicely.

Is there anyone using FG V1.0.0 on Linux (x86_64) that has the ec135 helicopter displaying and working correctly? If so could you please tell me where you got your ec135 aircraft files, or what you had to do to get it all displaying/working correctly?


If you are using FlightGear 1.0.0 and have installed aircraft that provide PNG files for their textures you have almost certainly installed the wrong version of the aircraft!
1.0.0 did not support PNG textures, while 1.9.0 and later does. However, the format of the textures is not the main problem - FlightGear changes over time in ways that are often not backwards-compatible (we develop the program and the aircraft together) so installing and using aircraft archives that isn't of the same version as your FlightGear binary is likely to fail in many ways.

If you really cannot upgrade to the current version you should fetch any additional aircraft you may want to install from the appropriate (i.e. matching) release. The (IMHO) most convenient way to do that is to fetch them from the FlightGear CVS repository (which, IIRC, contains all releases since 0.9.0 - as well as all intermediate developments since that time.)

Cheers,

Anders
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Re: Helicopter woes

Postby Groucho » Sun Mar 29, 2009 3:54 pm

HHS wrote:
Groucho wrote:...
I am flying it regularly and it needs constant handling in all aspects.



All helicopters need it! A helicopter is naturally instable flying object and it has to be forced to fly!


This is undoubted. What I was referring to is that the alouette reacts more sensitive to torque changes than most of the other helicopters in fgfs (except the r22 :) ).
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Re: Helicopter woes

Postby tduell » Sun Mar 29, 2009 10:14 pm

AndersG wrote:If you are using FlightGear 1.0.0 and have installed aircraft that provide PNG files for their textures you have almost certainly installed the wrong version of the aircraft!
1.0.0 did not support PNG textures, while 1.9.0 and later does. However, the format of the textures is not the main problem - FlightGear changes over time in ways that are often not backwards-compatible (we develop the program and the aircraft together) so installing and using aircraft archives that isn't of the same version as your FlightGear binary is likely to fail in many ways.

If you really cannot upgrade to the current version you should fetch any additional aircraft you may want to install from the appropriate (i.e. matching) release. The (IMHO) most convenient way to do that is to fetch them from the FlightGear CVS repository (which, IIRC, contains all releases since 0.9.0 - as well as all intermediate developments since that time.)


OK. I have been fetching aircraft files from the link on the website. Perhaps it would be helpful if that site indicated which version of FG each aircraft is suited to.

I have looked about for the CVS files but all I have seen thus far is an option to get the whole of the source and data, much more than I need.
I will have to look a bit harder.

Thanks for your help.

Cheers,
Cheers,
Terry
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Re: Helicopter woes

Postby Gijs » Mon Mar 30, 2009 8:35 am

tduell wrote:OK. I have been fetching aircraft files from the link on the website. Perhaps it would be helpful if that site indicated which version of FG each aircraft is suited to.
Each of the planes on FlightGear.org works with our latest version (1.9.1 at the moment). They might not work with older versions, doing so is at your own "risk".
Some planes have "versions". Those versions are usually dates. If such a date is between two FlightGear releases, then you'll have a good change that it works with the latest FG version available at that date. (see the release timeline on our wiki: http://wiki.flightgear.org/index.php/Fl ... e_timeline)
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Re: Helicopter woes

Postby AndersG » Mon Mar 30, 2009 11:08 am

tduell wrote:OK. I have been fetching aircraft files from the link on the website. Perhaps it would be helpful if that site indicated which version of FG each aircraft is suited to.

I have looked about for the CVS files but all I have seen thus far is an option to get the whole of the source and data, much more than I need.
I will have to look a bit harder.


The aircraft on the main download page are always for the latest release, but yes that could be made clearer.

You can also checkout individual subdirectories from CVS. Just include the path to the directory you want when doing the checkout. E.g.
Code: Select all
cvs -d :pserver:cvsguest@cvs.flightgear.org:/var/cvs/FlightGear-0.9 checkout -r RELEASE_1_0_0 data/Aircraft/787

Use -r to set the version you want (or -d for a certain date). For 1.0.0 you want
"-r RELEASE_1_0_0", and for CVS/HEAD you just leave out "-r RELEASE_1_0_0".

Btw, you can do this with TortoiseCVS for windows too - there you just select the module (i.e. aircraft directory :) you want in the module list (click "fetch list" first).
Set the desired version using the revision tab before commencing the check out

Cheers,

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