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Off Field piper cub

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Off Field piper cub

Postby skypup » Tue Mar 11, 2008 4:37 am

Hi, I'm new to the forums. I've been messing around with Flightgear for a couple months now.
One thing I have noticed, and would like to work on, is off field with the piper cub. The cub has been one of the great off field airplanes, and it seems rather strange that in flightgear, if it gets off field, it sticks tighter than bubblegum to a hot sidewalk.
I have been doing a lot of off field with the dragonfly with no trouble. My first thought was to find the dragonfly's ground reaction code and duplicate it with the cub.
It was no problem finding it in the Dragonfly file, but there seems to be nothing like it in the Pup file.
I am left with no idea where to start.
Has anyone else taken this on? I would love to hear what you did. I would really like to do some bush flying with the pup, but sticking tight and nosing over on touchdown is getting old.
Hoping to hear from someone who has had better luck than I with this.
Is it nap time yet? And where are the doughnuts?
skypup
 
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Postby skypup » Sun Mar 16, 2008 1:42 am

I guess there isn't as much interest in this as I thought there might be. Oh well.
Is it nap time yet? And where are the doughnuts?
skypup
 
Posts: 37
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Location: western Washington

Postby AndersG » Sun Mar 16, 2008 1:56 am

I suspect it is a feature and not a bug. The Cub is a YASim aircraft and YASim models the properties of unprepared (and prepared) ground. Your off field field is probably much more uneven than it looks :)
For JSBSim everything is a runway (unless the aircraft designer spent extra effort to mimick the effects).

/Anders
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Postby HeliFlyer » Sun Mar 16, 2008 3:27 am

Hi skypub,

I believe it is more your problem than one of the aircraft.

Although I am not taildragger experienced it was pretty simple to takeoff and land the Cub on grass/farmland.
Remember lifting the tail at about 35 miles you'll takeoff a short time later with about 50 miles. These are not "official" numbers, just the speeds I managed to do the job without problems :-)

Which scenery version? Give me the lat-lon coordinates where you have difficulties to takeoff. I would like to test it.

Regards
Georg EDDW
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Postby skypup » Sat Mar 22, 2008 6:06 am

Hi Heliflyer,

It's not a problem of takeoff technique, it is a problem of how to get the plane to move after landing. Once I was aware of the situation, I changed my landing technique, and can put down without mishap on any of the surfaces in the pup of the beaver.
It seems that only some surfaces will let you take off again though.
On a surface with trees, even if you land in a nice space between them, once stopped, the wheels seem to put down roots like a tree.
Full throttle will not move the plane.
My experiments so far have found that if the surface looks like bare sand, or if the random objects feature puts cows on a surface, you can take off again.
It's kind of strange flying around looking for cows to know if I can land there or not.
The intersting thing is, you can fly right through the trees, but a cow will stop you dead.
Also, some of the small fields don't place the plane accurately, and you find yourself stuck at startup. You might be looking at the field 25 meters away, but the plane won't move.
Anyway, I am using 1.0, and I have been trying this all over the western US.
Some of my favorite fields are; 00C Animas Air Park, 4WA8 Riverside, KSEZ Sedona, 0CO2 Buckhorn ranch, And UT59 Needles outpost.
What version are you using, and where are you flying?
Is it nap time yet? And where are the doughnuts?
skypup
 
Posts: 37
Joined: Mon Mar 10, 2008 2:55 am
Location: western Washington

Postby HeliFlyer » Sat Mar 22, 2008 9:21 am

Hi skypub,

I am using FlightGear CVS OSG (the development branch), therefore there could be some differences to FG 1.0 PLIB (your version) in the ground behaviour. AND I am flying mostly in Germany.

As I am curious how my FG version behaves when flying the fields you named I will try some of them and report later. This might not help you actually but could show the difference between the FG branches (or not :-/ ).

Regards
Georg EDDW
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Postby HeliFlyer » Sat Mar 22, 2008 12:53 pm

Hi skypub,

I am here again after some testing.

First I want to thank you pointing to these very interesting places. With some user-placed objects they would be even better. Are you familiar with these areas? Then you could try to place some fitting generic objects there :-)

But back to your problem. You are right for some of these areas - Needles and Sedona (could not find Animes, might be I don't have installed that area). An off-field landing is possible but you get stuck in the terrain, no chance to take off again. But it is possbile with some fake, I will return to this later.
But first to the two other places. You'll have no chance to land or take-off from off-field - if the FG used terrain is correct. See how these areas look in the new developers FG version - then you'll understand :
(pictures 2..4 = "NoChanceOutsideLandingXX". Click on the preview pic to get an enlarged pic. Click "zurück"= "back" ord "vorwärts" = "ahead")

http://home.arcor.de/vollnhals-bremen/CubTerrainFric/

But I made a really QUICK AND DIRTY workaround to make it possible to take-off outside Needles (did not try Sedona due to lack of time, but should work, too). Set full power, be a little patient .. and off you'll go (See pics "ChgdFricValXX").

Here is a snipplet of code you have to replace the gear-code part of your "j3cub.xml" file with (make a backup of the file first incase you don't like that patch):

<gear x="-5.17" y="0" z="-0.71" compression="0.1" sfric="0.1" dfric="0.1">
<control-input axis="/controls/flight/rudder" control="STEER"
src0="-1.0" src1="1.0"
dst0="0.5" dst1="-0.5"/>
</gear>

<gear x="0" y="0.95" z="-1.96" compression="0.01" sfric="0.2" dfric="0.2"> <!-- left main -->
<control-input axis="/controls/gear/brake-left" control="BRAKE" split="true"/>
<control-input axis="/controls/gear/brake-parking" control="BRAKE" split="true"/>
</gear>

<gear x="0" y="-0.95" z="-1.96" compression="0.01" sfric="0.2" dfric="0.2"> <!-- right main -->
<control-input axis="/controls/gear/brake-right" control="BRAKE" split="true"/>
<control-input axis="/controls/gear/brake-parking" control="BRAKE" split="true"/>
</gear>


As I already said, this is a quick workaround and not a solution. All values are "guessed" and might have some bad side-effect when landing/taking off on normal runways. Just try it.

Have fun!
Georg EDDW
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Postby skypup » Mon Mar 24, 2008 10:46 pm

Hi Heliflyer,

Sorry I'm a bit late geting back to you The goats are kidding now, so we have been a bit busy.
The workaround is great! The roughness really gives the feel of an off field landing. Haven't had any complications anyplace I have tried it. And still works great on normal fields.
The only thing I notice is the brakes seem to have disappeared. The cub's rollout is so short that it's not much of a problem though.
Yes, most of the fields I told you about are places I know. Animas air park is just outside my home town of Durango Colorado. Needles is in Canyonlands National park in southern Utah.
Arizona and Utah are great for off field flying. Lots of desert washes, slick rock and old dirt roads.
Riverside is a private field about a mile SE of where I live now in Washington state. Trees about 100 feet tall at the east end, and powerlines at the west.
I have played around a bit at placing objects, but not really good at it yet.
I was really surprised when I loaded the scenery for this area. It is mostly open fields with some stands of trees in flat areas in real life. Lotds more trees in flight gear. The hills and mountians forested though.
My long range ideal would be to model the two ultalights I am building, and the runway I have made in the pasture, and get the Neighborhood more accurate.
Then, when the weathers bad, I can still fly the ultralights around here.
I can see it will be a ways down the line though.
I haven't loaded any of Europe yet. As you are in Germany, can you recomend some interesting places?
Once again , great work on the gear! Thanks so much!
Is it nap time yet? And where are the doughnuts?
skypup
 
Posts: 37
Joined: Mon Mar 10, 2008 2:55 am
Location: western Washington


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