Grumman Cat

Some of the changes you made I like (in the air), however, when the aircraft loads for me, it bounces once and crashes. I see no difference in the class 1 contact points but I do in the class 2 points.

I did change the static height to -3.8 which resolves that issue.

With the geometry and reference changes you made, the center of gravity now sits in front of the wing at -12% of MAC making the nose heavy and the suspension harsh (too much weight on the nose gear, less on the mains). This causes smoking bouncy tires during rollout and over steering.

Changing the wing_pos_apex_lon =2.76000 corrects the CoG to 25% MAC but the suspension is still harsh and bouncy. This may be a result of moving the CoG reference forward 2' but not adjusting engine location, or the lighter MOIs.

Overall, unless you can resolve these issues, I prefer the original FM over your changes.
 
That is interesting Milton.

All the changes I made were guess work using trial an era without an aircraft cfg configuration utility of any kind. Was all freehanded then go fly, until it felt closer to what I remembered of the handling of the real plane. No dout here that the numbers are way out of bound compared to a configuration utility tool.

I see no smoking bouncing of the tires or the plane with my settings.

I'd also like to note that even with the original downloaded model's aircraft cfg file, I have never seen this model jump around.

This leads me to believe that not every downloaded model behaves exactly the same in every computer. For several years now I have suspected that may be true. I thought it odd in the beginning of this thread that many others were seeing a problematic bouncing plane and I never have.

Thanks for the feedback.

David
 
When I first downloaded the AA-1C, it shimmied and danced on the ground. I made some adjustments to the contact points and that went away. Then I found that the landing gear failed even during gentle landings...so some more contact point tweaking seemed to fix that problem.

But....the way this plane behaves on the ground when sitting/taxiing and during landings is not the same at every airport. Now, most of my scenery is stock in terms of airports. Mesh is the freeware Genesis US mesh, Rhumbaflappy's LOD5, 7 and 8 Mesh, and a few other meshes for Hawaii, Greece, etc. At one airport the AA-1C sits nice and sweet, at others the plane wiggles on the ground. At some airports the plane bounces so hard the landing gear fails. At one airport I can slam the plane onto the runway like I am trying to kill it, at another airport the main gear failed during a oh so gentle feather light landing.

In the air, this plane is a dream...but on the ground it is proving to be an unpredictable nightmare.

OBIO
 
Now that you mention that Obio, I had downloaded and installed a mesh for S.C. which may be why my copy of the plane never has bounced or jumped around. Different airport altitudes between default and the downloaded ones I suppose.

Well now that seems to kill the theory I was forming that same downloaded planes behave differently on different computers. Thanks for clearing that up for me.

I will try the plane out in another area of the country that has default airport elevations.


Yikes! Went to Charleston WV for some varied airport elevations and it was bouncing all over the place! I still like my flight characteristic settings as per the real plane's flight envelope. I think I will simply add your contact point settings to the cfg I tweeked. That should be sweet enough for me no matter where I fly to. And thanks for the pilot textures OBIO! Love this little trainer.
 
Well, I tried the mods so far and all I got for it was a plane that bounces all over the place when in motion on the ground. Even the beefed up landing gear proves to be no match and landings...well let's just say I can usually walk away from them.
However, I found out there is hope. In a fit of desperation I swapped out the aircraft.cfg file with that from the default 172 and pasted the contact points and lights from the original on. The result: no shaking, bouncing, sparking or smoking. Sure it flies like a 172 however at least I was able to find out that it is not the contact points that is giving me all this trouble. Will try to do more research during the day but take heart we will get this bird working yet!!!:jump:
 
By Jove I think I got it...

After replacing the aircraft.cfg file with that of a 172 I got to replacing individual sections in the .cfg file with parts from the original. Normally this would be an excruciatingly time consuming process. However I found the problem in my first try.
...It's all in the MOI's.
under the [Weights and Balances] section you will see this:
[weight_and_balance]
// ACM V2.5
max_gross_weight =1600.0
empty_weight =1141.00000
reference_datum_position = 0, 0, 0
empty_weight_CG_position = 0.000, 0.000, 0.000
empty_weight_pitch_MOI =681.78000
empty_weight_roll_MOI =381.35000
empty_weight_yaw_MOI =828.00000
empty_weight_coupled_MOI =0.00000
CG_forward_limit = 0
CG_aft_limit = 1
max_number_of_stations =1
station_load.0= 166, -0.144, -0.533, 0.000

Replace the above-referenced bold-faced figures with these figures (sourced from Piglet's AA-5A)
empty_weight_pitch_MOI =813.00000
empty_weight_roll_MOI =722.00000
empty_weight_yaw_MOI =1264.00000
empty_weight_coupled_MOI =0.00000

At this point it is a temporary fix--for some reason it 'feels' heavier (I would suppose with good reason seeing as the MOI's were taken from a 4-seater and all). Now I don't have the benefit of actually flying one of these but from what I have read on the internet they were twitchy little guys. I will continue to tweak the MOI's and see how close I can get it to be more twitchy without it doing the dance on the ground.
Hey, it's progress--who knows I might actually get a real flight out of it yet today lol
I would also like to thank OBIO for the revised pilot texture-lookin good:ernae:
Piglet if you are reading this I would also like to thank you for the AA-5:salute:
Thank you Ron Watson for coming up with this plane. It's beautiful.:ernae:

EDIT: I think I got it down to one line that might be causing the bouncing...the roll MOI line is too low. I bumped up the pitch MOI slightly as well and at this point the only time it dances is when I hit the brakes at over 45kts and it isn't much bouncing at all.
//empty_weight_pitch_MOI =681.78000
empty_weight_pitch_MOI =700.00000
//empty_weight_roll_MOI =381.35000
empty_weight_roll_MOI =722.00000
empty_weight_yaw_MOI =828.00000
empty_weight_coupled_MOI =0.00000

I'll probably be seeing just how low I can get that roll MOI line but with it bouncing when I hit the brakes at relatively high speed I'm thinking I'm near the lower limit already.
 
Gonna give your results a try Drzook. It would be nice to get this nice model dialed in right or close to right anyway.

The real plane certainly had a quick and athorative rudder When I flew the RL one rarely did I ever use rudder in turns in cruise flight. However on set up for approach to landing I always placed the feet on the rudder pedals to confirm rudder was still available if the need arised for them on final. You would test the rudder pedals and it quickly you were reminded that they were like quick powered steering. There was too much rudder for it's area size coupled to a short fuselage.

Aileron control seemed pretty much normal but it would roll at a nice rate, a slight bit better than a cherokee or a 150 or 172.

Elevator control and response was as good as the aileron response, a little quicker than what seemed normal. But that rudder seemed like it was magnified in comparison to a cessna 150-172 or cherokee. To me. it made me feel like their were snakes down at them pedals. Using the rudder in cruise you would say "Better keep those feet off them and on the floor. Seemed useless energy to keep the feet on the pedals. Of coarse when it come time to land, instinctively you would ready them for use should you may need it on approach. It was squirrely. Of coarse near stall speed the rudder felt more right with lessened airflow to it.

Will try the 172 cfg and try the new settings on the original cfg. Thanks for the time and effort. This is a very nice little model and cute as all get out.
 
Clearly I have been wrong about several things about this model. I had been calling it an AA1-A Grumman American trainer Clearly I was wrong. May have to scratch out any references I have made about this model. Seems there have been changes made as well as model and corporate names. Sorry bout that!:) Well it looks like an AA1A trainer! Wonder if the manufacterures tweeked down the squirrely rudder on the C's or kept it. They probably did tone it down some.

http://en.wikipedia.org/wiki/Grumman_American_AA-1
 
DrZook

YOU FIXED IT!!!! I plopped your MOI tweaks into the AA-1C's aircraft.cfg and she handles wonderfully on the ground. Yes, I did break the landing gear...but only after a series of 6 brutal landing tests....the last landing had the little plane slamming the ground at about 100 knots in a three point flat landing.....she went to bouncing like a frightened cat and the left main gear broke on the tenth or eleventh bounce. This is a drastic improvement over the stock landing behavior, which saw both main gear legs break after a super gentle touch down. Thank you!

OBIO
 
Just so you guys know, Ron Watson has been trying to join so he could post here but is still awaiting confirmation.

He has been reading the posts and responding to your feedback. Hopefully we will hear from him soon.
 
The fix cured all, much better now. Pilot texture is sharp, no jitters or dancing.

Thanks Ron
 
Ooh La La! Add some specular shine and reflectivity to this plane and it really comes alive. How do I know? Cause I tweaked the MDL file using MDLC 117 and a hex editor to add specular shine and reflectivity.....that's how I know. Working on a paint job for the plane...a totally fictional but very nice looking color scheme with a British registration number...and the plane just looked flat. So I added the specular shine....and it was better. Then I added the reflectivity and tweaked the paint with an alpha channel...and, as the French say, Voi Louis!...or something like that.

Will contact maker of this fine little plane and see if he would like to upload the tweaked MDLs as an update or give me permission to do so.

OBIO

Oh....this plane will look great in polished aluminum don't ya think?
 
Grumman AA1-C T-Cat

Hello fellow pilots,

I would lke thank you all for the support. This project has been a long time coming. And it is great to see so many people enjoying it. If anybody is interested in releasing the AA1C for FSX? Please contact me ( www.ronco@amcom.co.nz ) as I do not run FSX. My system will not handle it.
:ernae:
Regards,
Ron Watson.
 
You must log in or register to reply here.
Back
Top