Can someone help with small Alphasim F-111 issue please?

[Bushi]

Hi everyone,

I’m hoping that if you have chosen to read this post, you have an interest in the Alphasim F-111, and with any luck, some will have a knowledge of editing aircraft cfg. Files and might be able to help with this niggling little problem.

I’ve had this airplane for a long time now, but just recently became re-interested in it, and after a flying it as it came in the download, decided that for me at least, it needed some ‘tweaks’.

So, to keep it short, I’ve modified a few bits on the original aircraft, specifically, weight… fuel and payload, and the contact points.

As best I could, I’ve gotten the aircrafts range / fuel consumption close to real world figures. (no more Lossiemouth to Cape town on internal fuel!) I’ve added the 600 gal external tanks to the fuel menu and adjusted the internal fuel volume and fuel consumption scalar.

But the big stuff came with the aircrafts contact points, and that's the reason for this post.

I’ve edited the steer angle to give it a tighter steering circle (much nicer), and the sections that adjust the max/static compression ratio and damping ratio (sections 8,9,10 in the contact points for the main gear) to get a better sit at various weights.

There is now a nice sit to the gear at all weights from fully loaded to empty, without the aircraft looking like a ballerina up on her tiptoes when taxiing in at near empty weight! THAT drove me nuts!! LOL
I like the external visuals MUCH better with these modifications...

HOWEVER……. and here it is......
Now… for reasons beyond my knowledge, when the aircraft is accelerating down the runway, instead of the fuselage beginning to adopt a nose down attitude as the wings take her weight as seen in the original cfg., the main gear tires simply sink into the runway! So… it seems to me that something else needs to be addressed here to fix this issue… and I haven’t been able to identify it yet.

So, anyone out there familiar with contact point editing etc. that can address and fix this for me????

It’s only an issue of perception if you are outside, watching the takeoff.. so.. not really a problem since I like to sit ‘inside’ the airplane, but if I upload my changes for anyone who wants them, I would be happier if this little visual issue was gone!

I’ve included a few screenshots of the original 'sit' of the aircraft, and after my mods, so you can see the differences.. and the takeoff visual issue!

Plus below, is the entire contact point and weight changes sections of the cfg. File if anyone wishes to try it out on their personal F-111 and see if they know the problem! (don’t forget to make a backup copy of your original!!)

ps. if you use my fuel and weight sections below, edit the fuel consumption scalar to 1.0 to get a 2500 mile range on internal fuel.

thanks for reading
Dave




[fuel]
fuel_type = 2
number_of_tank_selectors = 1
electric_pump = 1
Center1 = 0.000, 0.000, 0.000, 1000.000, 0.000//2000.000, 0.000
Center2 = 0.000, 0.000, 0.000, 650.000, 0.000 //1350.000, 0.000
LeftMain = 0.000, -8.000, 0.000, 600.000, 1.500
RightMain = 0.000, 8.000, 0.000, 600.000, 1.500
external1 = 0.000, -8.000, 0.000, 600.000, 1.500
external2 = 0.000, 8.000, 0.000, 600.000, 1.500


[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, 40.0, 0.150, 5.0, 0.900, 5.0, 5.0, 0.0, 300.0, 350.0
point.1 = 1, -1.3, -8.5, -7.4, 2500, 1, 1.9, 0, 0.9, 1.7, 0.9, 5, 5, 2, 300, 350 //left main
point.2 = 1, -1.3, 8.5, -7.4, 2500, 2, 1.9, 0, 0.9, 1.7, 0.9, 5, 5, 3, 300, 350 //right main
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



[weight_and_balance]
max_gross_weight = 100000.000
empty_weight = 50000.000
reference_datum_position = 0.000, 0.000, 0.000
empty_weight_CG_position = 0.000, 0.000, 0.000
empty_weight_pitch_MOI = 251614.000
empty_weight_roll_MOI = 225692.000
empty_weight_yaw_MOI = 456426.000
empty_weight_coupled_MOI = 0.000
max_number_of_stations = 3
station_load.0 =200.000000, 23.290000, -1.110000, 0.740000, Station 1
station_load.1 =200.000000, 23.270000, 1.000000, 0.730000, Station 2
station_load.2 =12000.000000, 0.000000, 0.000000, 0.000000, Payload
CG_forward_limit= 0.000
CG_aft_limit= 1.000

[Bushi]

[Motormouse]

Iirc Steve Hess did some tweaks and improvements to the Alpha F-111; available at flightsim.com
Dont know if theres anything in that package you can adapt?

Ttfn

Pete

[Bjoern]

A faster download for the SHRS F-111 is here:
https://sites.google.com/site/shess0757/fs9downloads

[glh]

As I do not have the F-111, I would go back and get your original data and then adjust each value one at a time. It appears that you have really "stiffened" the suspension and are not allowing it to work as it should. Just my $0.02.

[Tom Clayton]

It could also be a limitation in the model's animation. Even though you have the spring height/loading right for static display, the heavier loading might not animate correctly.

[Desert Rat]

I found the perfect fix for your Aardvark woes.....

http://www.irissimulations.com.au/ha...nado-superpack

Shame the Aussies never choose this one, lol.

[Bushi]

As I do not have the F-111, I would go back and get your original data and then adjust each value one at a time. It appears that you have really "stiffened" the suspension and are not allowing it to work as it should. Just my $0.02.

It's been stiffened and the oleo travel shortened to get a decent looking sit at all weights, but as you can see.. that contact point does some weird stuff just before rotation. I've seen this sort of thing before, on multi wheel bogey aircraft. I've adjusted and tweaked the values so many times to get the gear to look good 95% of the time... ( I must have ten or fifteen 'saved' cfg. files!)

I can live with tires sinking into runways on liftoff.. as I'm usually inside.. busy with stuff during this part of the flight! LOL

I just wasn't sure if anyone else would be happy with this issue if they wanted to use my changes.

cheers, and thank you for answering
Dave

[Bushi]

It could also be a limitation in the model's animation. Even though you have the spring height/loading right for static display, the heavier loading might not animate correctly.

The only time this is an issue is at rotation, so... I'm happy with it as I like to be um.. inside my plane when I takes off! LOL


Even on landing, there is good rebound and damping of that main gear, so it's not just static. And the aircraft is not heavier, the gear has been adjusted to limit the oleo extension as the aircrafts weight is reduced. (at least.. that's what I think I have done here!) that is the effect I see.

Seeing it sitting properly from the spot view as it taxis in after a flight... okay.. THAT I needed to fix! and pretty much succeeded.

I was thinking along the animation issue line too.

thanks for the input!
Cheers
Dave

[Bushi]

Iirc Steve Hess did some tweaks and improvements to the Alpha F-111; available at flightsim.com
Dont know if theres anything in that package you can adapt?

Ttfn

Pete

I have looked at Steve's page and considered it. might just add it as aseperate aircraft in the Aircraft folder, copy some of my custom paints over, and see if my system handles what I perceive is a higher use of it's resources! and I'm running flightsim on a six year old Toshiba Qosmio.... :-)

thanks,
Dave

[Milton Shupe]

Dave, the reason you are experiencing the issue is that the modeled animated suspension travel distance does not match the total contact point designated distance.

The contact point distance is "static compression" times "max-static ratio" = "total suspension travel".

Total suspension travel must equal the modeled animated movement for the visual to stay correct in all situations.

So, your first challenge is to determine the total modeled suspension travel. Here's how:

To find that, you can modify the contact points to get 100% compression sitting on the tarmac.
Just use a larger static compression number and set your max-static ratio to 1.0.
Now set up a nav light to find the bottom of the tire (with suspension fully compressed). Use the contact point location as a starting point and adjust the vertical axis to you split the light.
Once you find that, change the static compression to 0.00 and find the bottom of the tire (with the suspension hanging).
The difference in the two vertical numbers is your total animated suspension in feet.

Now that you have the total animated suspension travel distance, change the contact points to reflect that number. Here's how:

Because the total travel is likely significant due to difference in empty and total weight and if this is a carrier landing craft, long travel is required, you want most of your travel in static compression when fully loaded. So, load up the aircraft and set up the contact points on a fully loaded aircraft.

Set Static compression to be 70% of the total animation, and use 1.428 as the max-static ratio. (1.00 divided by .70)

Once you have this, only then can you set the contact point verticals for good visuals setting on the tarmac. i.e. always get the suspension right before adjusting vertical distance to ground for good tire visuals.

[vonernsk]

Bushi,

Your query on suspension visuals and Milton's complete reply (carefully noted in the 'Milton's Gems' notebook), are the reasons why I am constantly engaged with the 'sim-outhouse' site.

Very rarely does someone come up with a problem that another member cannot professionally solve. Even rarer is a member with a problem (no matter how obscure) being left without the feeling that, even though the problem remains un-solved - a lot of thers have at least considered it and proffered their 'two penny worth' on it.

Thanks guys for giving me such a 'warm fuzzy' feeling when I see an exchange of problem and solution like this one.

Mal

PS: I do not contribute much to this site - but I sure appreciate what I have been given by being a small part of it.

[aeromed202]

Before I try Milton's formula (sounds catchy) you can try these out, they seem to work well for me anyway. I had reduced the wheel size significantly which seemed to help the floating tires on landing then settling during roll out I also decreased the turning radius and softened the main gear compression a little. The main gear width is well beyond the visual location which is just my compromise to achieve a certain compression on landing yet not allow the aircraft to roll significantly on sharper taxi turns. I made some other changes but these are the points I use. Haven't tried out different loads yet. Have fun.


point.0 = 1, 23.8, 0.0, -7.55, 2000, 0, 0.9, 45, 0.15, 5.0, 0.9, 5, 5, 0.0, 300.0, 350.0
point.1 = 1, -1.3, -8.5, -8.30, 2500, 1, 0.9, 0, 1.60, 2.3, 0.7, 5, 5, 2, 300, 350
point.2 = 1, -1.3, 8.5, -8.30, 2500, 2, 0.9, 0, 1.60, 2.3, 0.7, 5, 5, 3, 300, 350

[Bushi]

Dave, the reason you are experiencing the issue is that the modeled animated suspension travel distance does not match the total contact point designated distance.

The contact point distance is "static compression" times "max-static ratio" = "total suspension travel".

Total suspension travel must equal the modeled animated movement for the visual to stay correct in all situations.

So, your first challenge is to determine the total modeled suspension travel. Here's how:

To find that, you can modify the contact points to get 100% compression sitting on the tarmac.
Just use a larger static compression number and set your max-static ratio to 1.0.
Now set up a nav light to find the bottom of the tire (with suspension fully compressed). Use the contact point location as a starting point and adjust the vertical axis to you split the light.
Once you find that, change the static compression to 0.00 and find the bottom of the tire (with the suspension hanging).
The difference in the two vertical numbers is your total animated suspension in feet.

Now that you have the total animated suspension travel distance, change the contact points to reflect that number. Here's how:

Because the total travel is likely significant due to difference in empty and total weight and if this is a carrier landing craft, long travel is required, you want most of your travel in static compression when fully loaded. So, load up the aircraft and set up the contact points on a fully loaded aircraft.

Set Static compression to be 70% of the total animation, and use 1.428 as the max-static ratio. (1.00 divided by .70)

Once you have this, only then can you set the contact point verticals for good visuals setting on the tarmac. i.e. always get the suspension right before adjusting vertical distance to ground for good tire visuals.

Thank you Milton!! and once my head stops spinning... LOL......... If a spare hour or so.. probably longer for me... comes available, and if Aeromed202's lines don't do the job for me, I will get pad and paper... and start with your formula!

As has been noted... this site is so chock full of talented individuals.... all willing to help others with issues.... Warm and fuzzy??? YOU BET!!! :-)

cheers
Dave

[Bushi]

Before I try Milton's formula (sounds catchy) you can try these out, they seem to work well for me anyway. I had reduced the wheel size significantly which seemed to help the floating tires on landing then settling during roll out I also decreased the turning radius and softened the main gear compression a little. The main gear width is well beyond the visual location which is just my compromise to achieve a certain compression on landing yet not allow the aircraft to roll significantly on sharper taxi turns. I made some other changes but these are the points I use. Haven't tried out different loads yet. Have fun.


point.0 = 1, 23.8, 0.0, -7.55, 2000, 0, 0.9, 45, 0.15, 5.0, 0.9, 5, 5, 0.0, 300.0, 350.0
point.1 = 1, -1.3, -8.5, -8.30, 2500, 1, 0.9, 0, 1.60, 2.3, 0.7, 5, 5, 2, 300, 350
point.2 = 1, -1.3, 8.5, -8.30, 2500, 2, 0.9, 0, 1.60, 2.3, 0.7, 5, 5, 3, 300, 350

I shall give this a try.... since you seem to be well versed in alphasim Aardvarkishian.....

And as for Milton... Getting advice from him is like visiting Yoda... the words of the master! As they say.. easy as riding s bike.. once you know how!!!!

somehow.. I do not feel worthy!!!

thanks
Dave

[Bushi]

Bushi,

Your query on suspension visuals and Milton's complete reply (carefully noted in the 'Milton's Gems' notebook), are the reasons why I am constantly engaged with the 'sim-outhouse' site.

Very rarely does someone come up with a problem that another member cannot professionally solve. Even rarer is a member with a problem (no matter how obscure) being left without the feeling that, even though the problem remains un-solved - a lot of thers have at least considered it and proffered their 'two penny worth' on it.

Thanks guys for giving me such a 'warm fuzzy' feeling when I see an exchange of problem and solution like this one.

Mal

PS: I do not contribute much to this site - but I sure appreciate what I have been given by being a small part of it.

YOU CAN SAY THAT AGAIN!!!!!

Amazing group of people!

[Milton Shupe]

I downloaded this aircraft just to see for myself what the original aircraft.cfg was like.

I found generally that the contact points were very close to accurate as they were originally. (Over-looking the over-wide main gear stance in the cfg shown in the attached, apparently for lateral stability).

I corrected one error in the left/right position of the main gear (8.5 and 8.7) that caused one wheel to appear higher than the other on the tarmac. Easy fix.

The vertical distance from the ground was set about .1 to .2 too high. Easy fix.

I had no issues with suspension not acting correctly with any weight load on the tarmac, on take off or landing.

So, with that said, here are my tweaks.

[Bushi]

I downloaded this aircraft just to see for myself what the original aircraft.cfg was like.

I found generally that the contact points were very close to accurate as they were originally. (Over-looking the over-wide main gear stance in the cfg shown in the attached, apparently for lateral stability).

I corrected one error in the left/right position of the main gear (8.5 and 8.7) that caused one wheel to appear higher than the other on the tarmac. Easy fix.

The vertical distance from the ground was set about .1 to .2 too high. Easy fix.

I had no issues with suspension not acting correctly with any weight load on the tarmac, on take off or landing.

So, with that said, here are my tweaks.

Hi Milton,

Yes, I corrected the uneven sit as well. my issue with the aircraft in relation to it's 'real world' counterpart was the unrealistically high sit of the aircraft on it's main gear when lightly loaded. It looked to me like a ballerina up on her toes! LOL

Studying pictures of f-111's sitting on their gear clearly show that the lower landing gear members are horizontal when the aircraft is sitting on the ground, and not much different when the aircraft is close to it's empty weight.
The Alphasim F-111's main gear angles down too much(which results in quite a bit of camber of the wheels) when lightly loaded, giving it an awkward appearance.

On the real McCoy, those big tires are ALMOST in contact with the underside of the fuselage when she is at high weights, and there isn't a whole lot of difference to that appearance when lightly loaded. see pic.....

I'm ust trying to get that 'look' when taxiing for takeoff... and then when she is light on fuel and back on the ground. with my tweaks, I have this, and the gear dynamics work well as far as rebound etc. is concerned on touchdown (either that or I'm incredibly good all the time LOL)

Here are mine full fuel including wing tanks (no payload), it since I usually land with 20% fuel left on board.. so... not as bad!

and at empty wt. (even now, there is STILL a bit of camber to the mains.. but I can live with

I was just hoping for a way to 'fix' that weird sink into the runway visual on rotation! :-)

I will try out your tweaks and see if things still look 'right' to me though, as I'm always open to experimentation.

thank you for taking the time to help me out on this issue Milton... GREATLY appreciated!!

Cheers
Dave

[Bushi]

Before I try Milton's formula (sounds catchy) you can try these out, they seem to work well for me anyway. I had reduced the wheel size significantly which seemed to help the floating tires on landing then settling during roll out I also decreased the turning radius and softened the main gear compression a little. The main gear width is well beyond the visual location which is just my compromise to achieve a certain compression on landing yet not allow the aircraft to roll significantly on sharper taxi turns. I made some other changes but these are the points I use. Haven't tried out different loads yet. Have fun.


point.0 = 1, 23.8, 0.0, -7.55, 2000, 0, 0.9, 45, 0.15, 5.0, 0.9, 5, 5, 0.0, 300.0, 350.0
point.1 = 1, -1.3, -8.5, -8.30, 2500, 1, 0.9, 0, 1.60, 2.3, 0.7, 5, 5, 2, 300, 350
point.2 = 1, -1.3, 8.5, -8.30, 2500, 2, 0.9, 0, 1.60, 2.3, 0.7, 5, 5, 3, 300, 350

Hi aeromed202,
I tried your tweaks abut found that the aircraft still has that ballerina on her toes look when lightly loaded, which is what I'm trying to get away from.

thanks for the input and help though... much appreciated that you took the time sir!

cheers
Dave

[Milton Shupe]

Hi Milton,

Yes, I corrected the uneven sit as well. my issue with the aircraft in relation to it's 'real world' counterpart was the unrealistically high sit of the aircraft on it's main gear when lightly loaded. It looked to me like a ballerina up on her toes! LOL

Studying pictures of f-111's sitting on their gear clearly show that the lower landing gear members are horizontal when the aircraft is sitting on the ground, and not much different when the aircraft is close to it's empty weight.
The Alphasim F-111's main gear angles down too much(which results in quite a bit of camber of the wheels) when lightly loaded, giving it an awkward appearance.

On the real McCoy, those big tires are ALMOST in contact with the underside of the fuselage when she is at high weights, and there isn't a whole lot of difference to that appearance when lightly loaded. see pic.....

I'm ust trying to get that 'look' when taxiing for takeoff... and then when she is light on fuel and back on the ground. with my tweaks, I have this, and the gear dynamics work well as far as rebound etc. is concerned on touchdown (either that or I'm incredibly good all the time LOL)

Here are mine full fuel including wing tanks (no payload), it since I usually land with 20% fuel left on board.. so... not as bad!

and at empty wt. (even now, there is STILL a bit of camber to the mains.. but I can live with

I was just hoping for a way to 'fix' that weird sink into the runway visual on rotation! :-)

I will try out your tweaks and see if things still look 'right' to me though, as I'm always open to experimentation.

thank you for taking the time to help me out on this issue Milton... GREATLY appreciated!!

Cheers
Dave

Oh, now I understand what you were saying.

That's just a matter of adjusting static compression (to add more compression under load) and max-static ratio (to maintain total animated suspension travel), then of course the vertical distance to ground once that is resolved.

I also adjusted static pitch and height.

See attached for copy.

[contact_points]
static_pitch = 2.25
static_cg_height = 6.6
max_number_of_points = 8

point.0 = 1.0, 23.800, 0.0, -7.550, 2000, 0, 0.900, 20.0, 0.150, 5.0, 0.900, 5.0, 5.0, 0.0, 300, 350.0
point.1 = 1.0, -1.3, -8.5, -8.5, 2500, 1, 1.9, 0, 2.3, 1.8, 0.9, 5, 5, 2, 300, 350
point.2 = 1.0, -1.3, 8.5, -8.5, 2500, 2, 1.9, 0, 2.3, 1.8, 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, 5.0, 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, 6.0, 0, 0.0
point.5 = 2.0, -17.2823, 0, -3.1525, 1500, 0, 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, 4.0, 0.0, 0.0
point.7 = 5.0, -24.323, 0.0, -1.152, 1600, 0, 0.0, 0, 0, 0.0, 1.0, 1.0, 1.2, 0.0, 0.0, 0.0
gear_system_type=1

[Bushi]

Oh, now I understand what you were saying.

That's just a matter of adjusting static compression (to add more compression under load) and max-static ratio (to maintain total animated suspension travel), then of course the vertical distance to ground once that is resolved.

I also adjusted static pitch and height.

See attached for copy.

[contact_points]
static_pitch = 2.25
static_cg_height = 6.6
max_number_of_points = 8

point.0 = 1.0, 23.800, 0.0, -7.550, 2000, 0, 0.900, 20.0, 0.150, 5.0, 0.900, 5.0, 5.0, 0.0, 300, 350.0
point.1 = 1.0, -1.3, -8.5, -8.5, 2500, 1, 1.9, 0, 2.3, 1.8, 0.9, 5, 5, 2, 300, 350
point.2 = 1.0, -1.3, 8.5, -8.5, 2500, 2, 1.9, 0, 2.3, 1.8, 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, 5.0, 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, 6.0, 0, 0.0
point.5 = 2.0, -17.2823, 0, -3.1525, 1500, 0, 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, 4.0, 0.0, 0.0
point.7 = 5.0, -24.323, 0.0, -1.152, 1600, 0, 0.0, 0, 0, 0.0, 1.0, 1.0, 1.2, 0.0, 0.0, 0.0
gear_system_type=1

NAILED IT!!!
that was it Milton... and you hit it bang on!

those main gear contact points and compressions are all lined up with the animation of the gear now... BRILLIANT SIR!!!

THIS is why you are, to me, one of the best flight sim airplane designers no... ENGINEERS out there!

The only thing I 're-edited' in your contact point section was to change the turning circle (steer angle) in the nose gear line to what I had done before. As supplied.. it is painfully wide! Changing the 7th value from 20.0 to 40.0 brings it into realistic parameters.

but the main landing gears sit at all weights is a good as it gets, with those big low pressure tires looking the part now as well... and no more disappearing act into the runway on rotation!


I'm happy with this, and can put it to bed!

thanks to all who chimed in with suggestions, all were valid... and I appreciate the time and effort of everyone here.

Cheers.. and happy flying lads!

Dave