Taming the Aardvark.

Sbob

Sbob

SOH-CM-2024
This is a project I've tried to tackle several times over the last fifteen years. :dizzy:
I would either give up and reload the original files or lose interest when real world stuff would become more important.
This is also an on-going process, I've made quite a bit of head-way but there are still some miles left in the trip, so don't expect a wham-bam-thank-you-Ma'am thread. :playful:

The aircraft I'm talking about is the Alphasim/Virtavia F-111/FB-111 for FS9. Like the real aircraft, it was years ahead of its time. The flight dynamics are surprisingly good once you learn how to fly it. Steve Hess did an incredible update job for FS9 and FSX several years ago but didn't really tackle some of the original bugs. Its also important to understand that there are bugs AND the limitations of the sim itself. Some of this stuff may eventually fall into the "as good as we could make it" box. :indecisiveness:

If you still have this plane loaded in FS or if you have some real-world stories about the 'Vark, I would greatly encourage your feedback and views. :encouragement:
I had a buddy from High School named Don who wound up being a Crew Chief for FB-111's (Pease AFB) and F-16's (Wright Pat AFB) during an almost 30 year career in the Air Force.
Sadly, we lost Don several years ago so all of those answers are gone.

Anyway, my next post will concentrate on the [contact points] section of the aircraft.cfg file. I have it about 80% complete but I still need to fine tune some of the complex gear animation.
 
OK, so no participation yet... :playful:

I want to start with the basics, so let's look at the basic [contact points] to see what we're dealing with:


[contact_points]
static_pitch = -0.3
static_cg_height = 7.44
max_number_of_points = 8

point.0 = 1.0, 23.800, 0.0, -7.550, 2000.0, 0.0, 0.900, 20.0, 0.150, 5.0, 0.900, 5.0, 5.0, 0.0, 300.0, 350.0
point.1 = 1.0, -1.3, -8.5, -8.5, 2500, 1, 1.9, 0, 1.5, 2.5, 0.9, 5, 5, 2, 300, 350
point.2 = 1.0, -1.3, 8.5, -8.5, 2500, 2, 1.9, 0, 1.7, 2.5, 0.9, 5, 5, 3, 300, 350
point.3 = 2.0, -17.991, -15.971, 2.100, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5.0, 0.0, 0.0
point.4 = 2.0, -18.537, 16.009, 2.100, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6.0, 0.0, 0.0
point.5 = 2, -17.2823, 0, -3.1525, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.6 = 2.0, 41.238, 0.0, -2.931, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 4.0, 0.0, 0.0
point.7 = 5.0, -24.323, 0.0, -1.152, 1600.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.200, 0.0, 0.0, 0.0
gear_system_type=1

On first glance, its a hot mess. I'm only dealing with the first three "point" lines at this stage (which will soon turn into four).
The first thing I want to do is get everything aligned so it isn't so easy to get lost. I'll also fix some format problems, things like single digit integers.
These format problems don't mean a thing to your computer, but is sure makes it confusing for the humans.

That leaves us with:

point.0 = 1, 23.80, 0.0, -7.55, 2000.0, 0, 0.90, 20.0, 0.150, 5.0, 0.900, 5.0, 5.0, 0, 300.0, 350.0 (nose gear)
point.1 = 1, -1.30, -8.5, -8.50, 2500.0, 1, 1.90, 0.0, 1.500, 2.5, 0.900, 5.0, 5.0, 2, 300.0, 350.0 (port main)
point.2 = 1, -1.30, 8.5, -8.50, 2500.0, 2, 1.90, 0.0, 1.700, 2.5, 0.900, 5.0, 5.0, 3, 300.0, 350.0 (stbd main)

Considering that the main wheels are supposed to be the same size, we already have a big problem. Someone installed the run-flat spare. :indecisiveness:
This is why its important to make the formats match. We don't even need to know what all of those numbers DO yet to see that there are issues.

At this point its a good idea to add the following table so we know what we're looking at:

//0 Class <0=none,1=wheel, 2=scrape, 3=float>
//1 Longitudinal Position (feet)
//2 Lateral Position (feet)
//3 Vertical Position (feet)
//4 Impact Damage Threshold (Feet Per Minute)
//5 Brake Map (0=None, 1=Left, 2=Right)
//6 Wheel Radius (feet)
//7 Steer Angle (degrees)
//8 Static Compression (feet) (0 if rigid)
//9 Max/Static Compression Ratio
//10 Damping Ratio (0=Undamped, 1=Critically Damped)
//11 Extension Time (seconds)
//12 Retraction Time (seconds)
//13 Sound Type
//14 Airspeed limit for retraction (KIAS)
//15 Airspeed that gear gets damage at (KIAS)

At this point, its a good idea to load the beast in FS9 and get some ball park ideas of what we're dealing with. More in the next post. :wiggle:
 
When looking at the F-111 on the ground, it becomes apparent that it was designed by a committee, a large committee that didn't agree on much. :playful:

One of the first things that strikes you is the main wheels and tires. As it turns out, they are the same wheels and tires that are used on the C-130. Their over-all diameter is 47 inches and we can convert this into a wheel radius of 1.96 feet. The nose wheels and tires? Well, good luck finding that info but they look about the same size as the nose wheels on an F/A-18 Hornet. The C-P section lists them as 0.9 feet, which is an OK ball park number for now.

At this point, we can update some numbers and see how the plane looks on the ground. I try to use an airport ramp that I know isn't "floating" and I want the sun low on the horizon so it makes some long shadows. This makes it much easier to position the tires so they are slightly "sunk" into the ramp, it just looks more realistic. Yeah, I know there's a program you can use for this BUT it doesn't take into account the idea that your ramp and runway textures might be sitting slightly above (or worse, below) the actual ground level. Instead, I start with a close range of numbers and test the results to see what works best. You'll also need to do some slow speed taxi runs and turns to look for the weird stuff like floating tires. Crank in your outside view and its position so you can see how well the tires match the shadows. Try to get your landing height (section 3) as close as you can. If the nose or main gear seems to be floating and you can't adjust them, the static pitch (listed right below the [contact points] line) might be wrong and you can try adjusting it slightly, nothing greater than +/- 2 degrees.
The other thing to always remember, the gear height is ALWAYS a negative number. The more negative it is, the longer the gear leg. So, all we've done so far is adjust the numbers in sections 3 and 6 from the table above. We've done some taxi tests but it was just to spot any goofy values. One thing that did pop up in the taxi and turning tests (among several other issues) is that the plane is a bit "tipsy". Bombers should "wallow" a bit but this seems excessive. The easy way to fix this is to add the fourth wheel and tire to the nose gear. What I have so far looks like this:

point.0 = 1, 23.80, -0.6, -7.440, 2000, 0, 0.90, 40.00, 0.35, 1.25, 0.520, 5.0, 5.0, 0, 300.0, 350.0
point.1 = 1, 23.80, 0.6, -7.440, 2000, 0, 0.90, 40.00, 0.35, 1.25, 0.520, 5.0, 5.0, 0, 300.0, 350.0
point.2 = 1, -1.3, -9.5, -8.100, 2500, 1, 1.96, 0.00, 2.50, 0.50, 0.500, 5.0, 5.0, 2, 300.0, 350.0
point.3 = 1, -1.3, 9.5, -8.100, 2500, 2, 1.96, 0.00, 2.50, 0.50, 0.500, 5.0, 5.0, 3, 300.0, 350.0

The new point.1 is a copy of the old point.0. All I did was space the tires 1.2 feet apart. With the plane sitting still, it looks good. Also, if you add an extra wheel don't forget to update the "max_number_of_points =" line from 8 to 9. One other small change was how far the main wheels are spaced apart. I made this one foot wider for extra stability and to account for the (real) 18 inch tire width. Note the 40 degree steering angle for the nose wheels, I wanted to increase this (for now) so I could really stress the taxi tests. You can also notice some other numbers I changed. In the next post, we'll dive into the dreaded sections 8, 9, and 10 to tighten up the shock absorbers and travel limits. :dizzy:

On .mdl files with complicated gear animations, this is ALWAYS a hoot. :banghead:
 
The first link, yes.
The second link, no and thank you for posting it. :jump:

Real world numbers are great but they don't always match an FS MDL. I just find all the info I can and try them out.
We need to remember that FS wasn't designed with swing wing aircraft in mind. The Center Of Lift is supposed to change with the amount of wing sweep.
FS just can't handle that. Mike Stone also produced some F-111 models. While you can't "mix-n-match" the .air files directly or borrow chunks of one .cfg file for the other, you can learn about what the designer's had in mind. Well, you can borrow chunks from other FS aircraft, but I only do that as a "last ditch" kind of thing. :listening_headphone

There are also similar FS aircraft out there with the same over-all characteristics, the Mig-23/27 from Alpha and IRIS and the F-14 from IRIS again.
All of these aircraft have to rely on a "best fit" approach to FS. :indecisiveness:

I think I'm close to getting the [gear and scrape] numbers right for the F-111. The only problem area is how the MDL's main gear animation matches up to aircraft.cfg data.
What will happen is that the plane is either overly sensitive to "ground effect" and the mains on the MDL will leave the ground (slightly) before the .cfg file can catch up or else the Static Pitch value is just wrong and I'll have to go back to "square one". :pop4:

I've also tried out some early edits to the Yaw parts of the .air file (section 1101) and it looks promising. :wiggle:

I warned y'all this was going to be a long thread. :playful:
 
I've had a quick look at it in ACM, the contact points aren't too horrible although the static pitch & CG height need adjusting. The biggest problem is, when viewed from the front, the main gear points are way off where they should be; there may well be a good reason for this FS-wise, I'll have a play and see what works.

Aardvark.jpg

Biggest problem, of course, is that Alpha/Virtavia used "one size fits" unlike their later approach with the Lightnings, Phantoms etc, so to get it right they should probably be split in to separate packs/installs. Again, I'll have a play & run them through AirWrench and ACM later today.
 
That jpg looks interesting. :wiggle:

I need to stress that I'm not using progs like airwrench for this edit.
I wanted something that would work within the limits of the MDL file that also looked good in higher resolutions.
A large part of the problem comes down to the movement/animation of the gear parts in the MDL files.
A lot of this stuff is going to have to be "best fit".

Here's the current version of the [contact points] numbers I'm using:

[contact_points]


//0 Class <0=none,1=wheel, 2=scrape, 3=float>
//1 Longitudinal Position (feet)
//2 Lateral Position (feet)
//3 Vertical Position (feet)
//4 Impact Damage Threshold (Feet Per Minute)
//5 Brake Map (0=None, 1=Left, 2=Right)
//6 Wheel Radius (feet)
//7 Steer Angle (degrees)
//8 Static Compression (feet) (0 if rigid)
//9 Max/Static Compression Ratio
//10 Damping Ratio (0=Undamped, 1=Critically Damped)
//11 Extension Time (seconds)
//12 Retraction Time (seconds)
//13 Sound Type
//14 Airspeed limit for retraction (KIAS)
//15 Airspeed that gear gets damage at (KIAS)




static_pitch = -0.3
static_cg_height = 7.44
max_number_of_points = 9

point.0 = 1, 23.800, -0.6, -7.330, 2000, 0, 0.91, 40.00, 0.35, 1.25, 0.520, 5.0, 5.0, 0, 300.0, 350.0
point.1 = 1, 23.800, 0.6, -7.330, 2000, 0, 0.91, 40.00, 0.35, 1.25, 0.520, 5.0, 5.0, 0, 300.0, 350.0
point.2 = 1, -1.3, -9.5, -8.100, 2500, 1, 1.96, 0.00, 2.50, 0.50, 0.500, 5.0, 5.0, 2, 300.0, 350.0
point.3 = 1, -1.3, 9.5, -8.100, 2500, 2, 1.96, 0.00, 2.50, 0.50, 0.500, 5.0, 5.0, 3, 300.0, 350.0


point.4 = 2, -17.991, -15.971, 2.100, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5.0, 0.0, 0.0
point.5 = 2, -18.537, 16.009, 2.100, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6.0, 0.0, 0.0
point.6 = 2, -17.2823, 0, -3.1525, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.7 = 2, 41.238, 0.0, -2.931, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 4.0, 0.0, 0.0


point.8 = 5, -24.323, 0.0, -1.152, 1600.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.200, 0.0, 0.0, 0.0


gear_system_type=1


I don't think things will be changing all that much from here on out. The only downside is that the main gear will tend to "float" at airspeeds above 50 knots.
If you really whack the thing down on the runway, the mains seem to work fine but will then start to float off again.
I've beat on the numbers long enough and I think its as close as it can get. Any other changes would mean goofing around with the Static Pitch/Static CG Height/over-all position of the CG and that's going to throw everything off. :dizzy:

Sections 9 and 10 (Max/Static Compression Ratio and Damping Ratio) seem to be really "tight" and even small changes have large consequences.

What seems to work best is to get the nose gear off the ground ASAP for take offs and to hold it off as long as possible for landings.
Speaking of landings, you'll also want to check the aircraft.cfg file and see if you have any brakes. If you can't find a BRAKES section, add the following:

[brakes]
toe_brakes_scale=0.45

to your aircraft.cfg file. I went with some softer brakes because, in reality, you don't touch them until your airspeed drops below 60 knots, unless you REALLY want to meet the firemen. :playful: Just keep the stick in your gut and use the nose to bleed off airspeed. The brakes are also VERY effective at taxi speeds.

I would encourage anyone else who wants play around with this plane to post their results in this thread. :wiggle:

Next up, I want to fix the "barn door" rudder and Yaw effects in the .air file. I'm making some progress and I'll post the results soon.
 
BTW, in case anyone has back-converted this plane for FS2002, that [contact points] edit seems to work even better than it does in FS9. :dizzy:

Why? Well, that's a good question. :indecisiveness:
 
IIRC, none other than Milton Shupe had a tinker with the contact points etc. Some time ago

Might be worth a forum search for you to compare notes

Ttfn

Pete
 
Motormouse said:
IIRC, none other than Milton Shupe had a tinker with the contact points etc. Some time ago

Might be worth a forum search for you to compare notes

Ttfn

Pete
Click to expand...


Holy Brushes With Greatness! :encouragement:
Do you mean here or over at Nel's site?
That could have saved me a bunch of time but I like diving into this kind of stuff. :biggrin-new:
 
BTW, if anyone would like to edit the MDL files to add night textures to the fuse, I would love to add some "slime lights" for night missions. :adoration:

Just look at Alpha's F-101 Voodoo or drop a PM on me for more details.
 
One last update for tonight (I'm fixing stuff as I find it).

If your version of the F-111 didn't include a [brakes] section in the aircraft.cfg file, add or update the following:

[brakes]
toe_brakes_scale=0.45
parking_brake=1

I'm working with the Steve Hess version and I *think* he was aiming more for FSX with the Tac Pack?

I wanted to try some aircraft carrier launches and landings using ARRCAB and the parking brake wasn't enabled. :jump:
 
Well, I may as well post my .air file adventure tonight. :wiggle:

This fixed a problem I wound up calling "Black Ice".
The rudder wouldn't do much in terms of changing direction, the nose would move to the side but it was like the plane was on glare ice and it would keep flying along the same path.
Not good for what was supposed to be the USAF's premier bombing platform in the 1970's and 80's and it made flying at low level and high speed a bit of an adventure. :dizzy:

My gut told me it was probably in the .air file.

Open the .air file with AirEd and scroll down to section 1101, Primary Aerodynamics.
Open that and scroll down again. Get to the Yaw section near the bottom.
The first thing I changed was:

Cn_dr Yaw Moment Rudder (Control)= to 128. This felt like I was moving in the right direction, but I still wasn't there.
Then I noticed:

Cn_r Yaw Moment - Yaw Rate (Damps - tailwagging)= and the old alarm bells started to ring. :wiggle:
Back in the old FFDS days, Sam Chin and I used to mess around with this stuff.

It looked too good to pass by, but what should I change it to?

I've always enjoyed how the Dean Reimer F/A-18 Hornets handled, so why not borrow the value from there?

The line now reads:

Cn_r Yaw Moment - Yaw Rate (Damps - tailwagging)=-6955 (DON'T FORGET THE MINUS SIGN!)

I saved the changes and started FS.

And, DANG doesn't it feel smooth! :biggrin-new:
Co-ordinated turns are a LOT more crisp but it still feels like a bomber.

For a first guess, I guess I nailed it.

Can I make it better? Maybe, but I like what I have now. I want to do a couple more hours of flight testing plus running the Auto Pilot and some low-level TFR flights but the flight dynamics feel MUCH better. This also works great in FS2002.

So, what's left? Honestly, not much. I DO want to try to fix the bleeping joy stick in the VC. It always blocks the HSI and I think I can either "ghost" it by playing around with the texture file and changing the alpha layer to a shade of gray or black to remove the grip part entirely. After that it will be small stuff like punching up the glass texture and shine and this project will be finished. :wiggle:
 
Nice.. :biggrin-new:

I tried Milton's numbers but it still felt too tipsy/top heavy and the NO BRAKES problem returned.
I'll goof with it some more over the weekend and post any changes. :wiggle:

Its neat to see he also set the static pitch so it sat a little more "nose high".
That's what probably cures the "floating mains" at speeds above 60 knots.
That was something I tried early but it really messed up the contact points so I abandoned it.
I also like my "four tires" mod and steering angle changes.

The BIG payoff (note to Jorge) was where he mentioned that (section 8) X (section 9) = TOTAL GEAR TRAVEL ( z axis).

//6 Wheel Radius (feet)
//7 Steer Angle (degrees)
//8 Static Compression (feet) (0 if rigid)
//9 Max/Static Compression Ratio
//10 Damping Ratio (0=Undamped, 1=Critically Damped)
Now that I see it, it makes total sense. :jump:

That does bring up what (section 10) is really doing?
If it means the same thing as shock absorbers on a car, a number closer to zero would be like soft shocks while a number closer to one would be firm shocks, why is this value usually GREATER THAN ONE?? :dizzy:
 
Sbob said:
... I tried Milton's numbers but it still felt too tipsy/top heavy...
Click to expand...

The real 'vark always looked tipsy/topheavy so it's no surprise that the model is.

I'll betcha that's why AlphaSims set the contact points a bit wider than the wheels.
 
So, its getting down to the nitty gritty. :running:

I took a really close look at what Milton came up with and made some final (???) edits.
One thing I forgot, this plane had to take off very close to its max gross weight with stuff hanging off the pylons.
I did some final tweaking to the damping and I think this will be it:



[contact_points]

//0 Class <0=none,1=wheel, 2=scrape, 3=float>
//1 Longitudinal Position (feet)
//2 Lateral Position (feet)
//3 Vertical Position (feet)
//4 Impact Damage Threshold (Feet Per Minute)
//5 Brake Map (0=None, 1=Left, 2=Right)
//6 Wheel Radius (feet)
//7 Steer Angle (degrees)
//8 Static Compression (feet) (0 if rigid)
//9 Max/Static Compression Ratio
//10 Damping Ratio (0=Undamped, 1=Critically Damped)
//11 Extension Time (seconds)
//12 Retraction Time (seconds)
//13 Sound Type
//14 Airspeed limit for retraction (KIAS)
//15 Airspeed that gear gets damage at (KIAS)




static_pitch = 2.25
static_cg_height = 6.6
max_number_of_points = 9

point.0 = 1, 23.800, -0.6, -7.330, 2000, 0, 0.91, 40.00, 0.35, 1.25, 0.620, 5.0, 5.0, 0, 300.0, 350.0
point.1 = 1, 23.800, 0.6, -7.330, 2000, 0, 0.91, 40.00, 0.35, 1.25, 0.620, 5.0, 5.0, 0, 300.0, 350.0
point.2 = 1, -1.3, -7.8, -8.350, 2500, 1, 1.96, 0.00, 2.30, 1.50, 0.700, 5.0, 5.0, 2, 300.0, 350.0
point.3 = 1, -1.3, 7.8, -8.350, 2500, 2, 1.96, 0.00, 2.30, 1.50, 0.700, 5.0, 5.0, 3, 300.0, 350.0


point.4 = 2, -17.991, -15.971, 2.100, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 5.0, 0.0, 0.0
point.5 = 2, -18.537, 16.009, 2.100, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 6.0, 0.0, 0.0
point.6 = 2, -17.2823, 0, -3.1525, 1500, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.7 = 2, 41.238, 0.0, -2.931, 1500.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 4.0, 0.0, 0.0


point.8 = 5, -24.323, 0.0, -1.152, 1600.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.200, 0.0, 0.0, 0.0


gear_system_type=1


The other edit is for the brakes:

[brakes]
toe_brakes_scale=0.45
parking_brake=1


(Feel free to crank the toe brakes scale to something higher like 0.90, but I wanted it to feel more like a bomber than a fighter.)

Plus the two fields I changed in the 1101 section of the .air file (see posts above).

I'd like to see some feedback if you'd like to try it out. :wiggle:

Fold it, spindle it, mutilate it, and get back to me.

Some quick flight notes:

-Take off. Get some back pressure on the stick sooner than you normally would (around 100 knots or less). A couple of extra dabs of upward trim also won't hurt.

-Cruising. Its normal to keep the wings swept about half-way back in normal cruise flight.

-Low level and TFR (autopilot). F-111 crews had to be above average. Act the same way. Resist the urge to tuck the wings all the way back at low level until you are sure of what you're doing. The same goes for high gross weights at low level.

-The F-111 is NOT a dog fighter. Do you see any missiles hanging off the wings? Forget about high AOA and 9 G's. While the -111 could carry guns, they were ONLY fitted to strafe ground targets. Think of the -111 and the F-105 as being very similar. YOUR domain is at 450+ knots, 200-500 feet above the ground, AT NIGHT. That's more than enough to get your adrenalin pumping.

-Pattern work. Watch your airspeed. With the wings out and the gear down, its a bit of a pig. Turns will bleed off speed, do your best to maintain 150 knots. Don't set that last notch of flaps until you get in the glide slope.

-Landing. Keep the nose high (about 5 degrees) until the mains touch down. Cut power as soon as possible. Try to keep the nose wheels off the ground as long as you can. Use the wings and flaps as air brakes, do NOT touch the wheel brakes until your airspeed drops below 100 knots, the wheel brakes work better at speeds below 60 knots.

-Try not shake as you climb down the ladder. :playful:


Some final edits:
You may want to adjust your view point in the VC. I've found it better to move the view point up and a little forward, but its your call.
Try changing the following section

[Views]
eyepoint=23.0, -1.14, 2.30

The blue number changes the forward part while the red number changes the height. Try to keep your edits to the right of the decimal point, a little goes a long way.
 
Oh, almost forgot scenery. :wiggle:

The "prime base" for most US F-111 models was at Cannon AFB (KCVS) in New Mexico.

Forward deployed bases included Takhli RTAF (VTPI), RAF Lakenheath (EGUL), RAF Upper-Heyford (EGUA), McClellan AFB (KMCC), and Nellis AFB (KLSV).

The FB-111's were based at Pease AFB (KPSM) and Plattsburgh AFB (KPBG).

Australian F-111s operated out of RAAF Amberley (YAMB).
 
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