Flight Model Question?

[Duckie]

Need some help with this question please. Is it possible for a "user" (me) to modify a flight charactistic for personal use or, with the author's permission, to publish the mod?

Here's the situation. Some of you may have followed the thread I started concerning Piglet's OV-1 throttle problem I was having. Thanks to aeromed202 I've been able to satisfactorily address that situation via the config file.

One last sitution exists that I'd like to address. Rudder induced roll. Rudder input induces the correct YAW direction, however the same input also induces incorrect or opposite ROLL. In other words, left rudder induces left YAW AND RIGHT ROLL! This isn't so bad in flight unless you make quick or radical flight atitude adjustments. But landing in cross wind can be disasterous! You want to keep your flight path lined up with a little rudder input but then your leading wing begins to dip so you get off the rudder and next thing you know your over the dirt or worse!

If this OPPOSITE ROLL effect can be corrected or modified I'd like to try and address it. If it cannot, then I need to stop waisting my time with it and learn to get along with what I have. I really like this model and not just because it's the only one in town! It really "LOOKS" like a Mohawk and I'm very pleased with it other than the Rudder probelm.

Is AirEd, or some other edit app a possible solution? If so where do I start? If not, I'm OK with that too.

Any comments and suggestions are greatly appreciated.

Thanks,
Duckie

[OBIO]

Duckie

If you want to share the flight dynamics tweak for Piglet's Mohawk...just shoot him an e-mail telling him what you did to tweak the flight dynamics and ask him if he has a problem with you uploading it to the library for others to use. Very simple approach.

As far as the rudder/roll thing goes...I am clueless.

OBIO

[Duckie]

Duckie

If you want to share the flight dynamics tweak for Piglet's Mohawk...just shoot him an e-mail telling him what you did to tweak the flight dynamics and ask him if he has a problem with you uploading it to the library for others to use. Very simple approach.

As far as the rudder/roll thing goes...I am clueless.

OBIO

Thanks OBIO. Clueless is my middle name when it comes to flight dynamics (and a lot of other stuff too)! Absolutely plan to ask Piglet for permission to share it, but first I need to see if this roll problem is reasonably addressable otherwise there may be nothing to request from Piglet!


Duckie

[aeromed202]

I would love to find a fix for this because there are other aircraft that have this problem. It is also possible that my messings with other parameters created or inflamed this specific issue.

As I've said before, my attempts to make planes fly realistically force me to consider all CFG sections as fair game for editing. Usually I get good results but there is always a possibility of an unintended side-effect that I missed. Feel free to slaughter my tweaks if a better CFG comes out of it. The end result of a plane that flies like the real thing is what I'm always after.

For starters consider the weight and balance section and maybe airplane geometry. Getting the opposite roll on rudder input would happen real life if you could imagine a huge mass connected somewhere well below the aircraft, like a helicopter bambi bucket on a short solid rod instead of a rope. A momentary right rudder input would tend to roll the left aircaft wing downward. So my thinking is that somewhere in those two sections there might be that sort of condition, or even a fix. Air files I can't do anything with.

[Duckie]

Hi aeromed202,

I meant it when I said above I was "CLUELESS!" ...meaning I wouldn't, on my own, have a clue as to where to start or what to adjust. My feeble mind keeps trying to tell me that it could be as simple as changing a minus to a plus or something like that in one of the many tables somehwere buried deep in that dungeon that I know as the .air file. Not much better off when it comes to the .cfg file. I'm hoping one of the FD gurus will be able to tell me yea or nay on the possibility of a fix. I don't mind doing the work, ie trial and error, if that's what it takes. I just don't know what to try else it all becomes one BIG error!

Steve

[Milton Shupe]

If the mass of the rudder is above the thrust line and center of gravity, an opposite roll is normal. If the mass is at CoG, then roll will be more at neutral to normal. If below, you will have serious issues with yaw and flip.

These factor are addressed in table 1101 of the air file at CL_dr

Cn_dr * (Distance Rudder Vertical / Distance Rudder Horizontal)

The value will be negative or positive depending on location of mass relative to CoG.

You can try adjusting this parameter in the aircraft cfg Geometry section but not sure it gets invoked.
vtail_pos_vert = 0

[Duckie]

Thank you very much for the reply, Milton. I have taken out my bow and will now begin to fiddle!

Thanks
Steve

[aeromed202]

Sorry Milton but I'm pretty sure that you are right. Not sorry that you are right, but sorry that I agree that "vtail_pos_vert = x" probably does not work. I tried some way out values there just to see if anything changed and got nothing. Duckie, you can try some bigger numbers to see if you get a response. I think I stopped at +/-100. I'll give this another go too.

I have seen similar problems especially with the recent work on the Vigilante. The pitch axis was aft of the tail. There was no reverse of expected movement with elevator input but it took a new air file to right the problem. CFG edits were simply useless. The opposite yaw problem is on a Northrop F-5 as well.


edit. After another quick look the above cfg line has no effect and can even be set to 0.00 (I tried -1000). However if you alter the empty weight line, vertical position to say 20, in the section below

[WEIGHT_AND_BALANCE]
max_gross_weight = 18109
empty_weight =8747
reference_datum_position = 0, 0, 0
empty_weight_CG_position = 0.55, 0, 20.0
CG_forward_limit = 0
CG_aft_limit = 1
max_number_of_stations = 2
station_load.0 = 200, 6, -1.2, 0, Pilot
station_load.1 = 200, 6, 1.2, 0, Observer
empty_weight_pitch_MOI = 23836
empty_weight_roll_MOI = 19346
empty_weight_yaw_MOI = 28537
empty_weight_coupled_MOI = 1000

which makes it almost unflyable, if you steady it out you get more or less the correct roll direction with rudder input. Where this leads I don't know, but again I think an air file edit may be needed?

[Duckie]

Sorry Milton but I'm pretty sure that you are right. Not sorry that you are right, but sorry that I agree that "vtail_pos_vert = x" probably does not work. I tried some way out values there just to see if anything changed and got nothing. Duckie, you can try some bigger numbers to see if you get a response. I think I stopped at +/-100. I'll give this another go too.

I have seen similar problems especially with the recent work on the Vigilante. The pitch axis was aft of the tail. There was no reverse of expected movement with elevator input but it took a new air file to right the problem. CFG edits were simply useless. The opposite yaw problem is on a Northrop F-5 as well.

Yep am202, my quick tests proved to have the same results. I even tried increasing numbers and changing the signs (+ -) in the air file without effect. I just don't have the smarts do dig any deeper. I'll fiddle some more with these parameters but I'm flying blind.

However, I know more now than I knew an hour ago, and that is just how much more I don't know!

Thanks guys,
Steve

[aeromed202]

Ha! I'm no smarter than anybody. I just have fun fiddling. What's the worst that can happen as long as I have a back-up file? Somewhere I have a cfg that allows a 747 to fly in 10 kts, it's hilarious!!

[srgalahad]

Need some help with this question please. Is it possible for a "user" (me) to modify a flight charactistic for personal use or, with the author's permission, to publish the mod?

Here's the situation. Some of you may have followed the thread I started concerning Piglet's OV-1 throttle problem I was having. Thanks to aeromed202 I've been able to satisfactorily address that situation via the config file.

Any comments and suggestions are greatly appreciated.

Thanks,
Duckie

I'll give you another perspective.

1. What you do in the privacy of your own sim is up to you.
2. Regarding public distribution, the first place to look is the original author's Read Me. Some are very specific about changes and public distribution. In many cases the author won't mind (and may clearly say so) - as long as the changes are true to the original model or correct a demonstrated 'flaw'.
3. If you look at uploaded 'fixes, 'updates' and 'mods' it's not often that there is any mention of the original author being asked or approving so your intent to seek that approval is commendable.

I've seen so many changes made and posted with absolute comfort that it's "fine since it's freeware", without documentation of the changes and rarely with any flight test data to show the accuracy of the mods. I sometimes wonder if there is a belief that none of this matters much as long as the user is satisfied.

However, some people are interested in a level of accuracy that is measurable. (Note: not "perfection") Some models do need extra help, but often simple 'hacksaw' mods to just the config file can upset other flight parameters (eg. climb performance, fuel consumption, speeds) that move the aircraft away for a fine balance of performance. Comprehensive 'repairs' may involve recalibrating the airfile and many are unwilling to go the extra mile to obtain fidelity. In others, they are deliberate attempts to 'tweak' a model regardless of real-world numbers for convenience (or even to massage it to deliberately sneak in a bit "more" so it "feels better").

While this may not concern 90% of the FS users, there are cases where this has some importance and the RTWR is one of those. While Piglet's OV-1 (in this case) may not become a popular RTWR aircraft, it's a process that has implications outside the simple world of individual sim flying and this is as good a time as any to address it.

To ensure a level playing field we've compared many a/c models to their real-world known performance and they have achieved acceptance as a result. The rules intend that mods maintain this realistic (& tested) performance envelope and must be "publicly available for download". Hence, a forum post about "just change this line..." doesn't fit as it is not generally available except to members of a forum. Also, there is rarely any flight test data or "beta-testing" to show what the mods have accomplished or changed. The issue is that there is a possibility for anyone to make the mods (or copy them), end up with adjusted but unpublicized performance enhancements or handling mods and then, in the RTWR use an aircraft that is NOT comparable to the original that has been in use, or available for testing.

Even for updates uploaded to the major sites, the aircraft so modified have been found to sometimes have enhanced performance. Sadly, this is showing up more and more as port-overs to FSX are being posted - some even billed as just 'modified textures'.

Sometimes a tiny 'fix' is all that's necessary, but why hide it in a forum? - bundle it, document it and upload it. Sometimes it's a major remake and all that deserves wide-spread availability for the masses to enjoy. RTWR racers have benefited from having some of these mods available, but to avoid lengthy debate, a comprehensive 'read-me' with the changes certainly helps and erases most of the doubt about accuracy or acceptability.

I'm glad to see you're willing to dig a bit deeper in the hope of enabling a better model. A couple have been discussed in the Outhouse (with input and descriptions of the frustrations):
http://www.sim-outhouse.com/sohforum...ad.php?t=26160
http://www.sim-outhouse.com/sohforum...ad.php?t=26231
http://www.sim-outhouse.com/sohforums/showthread.php?t=26156&p=300117&viewfull=1#post300 117

good luck!

Rob

[aeromed202]

Thanks for the review Rob. It's good to remember the more serious aspects of sim artistry, legalities that is. A you say it is more than just following the wishes of an author. And where I would, a time or two, admit to being not 100% compliant, any deviation is for my part unintentional and would more aptly be described as arising from the heat-of-the moment. I just get carried away with the fun. The last thing I want is to disrespect or ignore an authors work. I can stand to be more diligent but think I've managed to keep everyone in play so far. Legalities, even simple ones, give me hives.

I see the forum as something of a test platform. I would go the whole written permission and file upload more often but I want to be more confident that what I upload is really good. For that I hope for others to try something out informally and comment. I agree that where serious changes are made, a level field is optimum. What group wants to fly the same visual aircraft but no two perform the same because of tweaking?

Maybe there could be a topic section on this, a go-to place for advice and such. Or maybe a flight testing panel? Members with real flight experience or similar to try and approve or critique the changes. Just tossing out ideas here.

[Duckie]

Thanks, Rob, for your thoughts. But I have to confess that I'm a little "taken aback" by it. With all due respect, I think you may have misunderstood the intent of my request. My intent was to seek help with correcting what I believe to be an inaccurate flight characteristic in an otherwise very good flight model. My intent was not to create some super Mohawk to go higher, farther and faster than anyone else’s Mohawk, nor to plagiarize or otherwise abuse another's work.

Now, my definition of enjoyment (fun?) and my definition of "accurate" may very well differ from others. But I assure you I have no ulterior motives regarding steroidical aircraft performance. I simply would like a Mohawk that flies the way I remember a Mohawk flies, nothing more, nothing less. In order to have a hope of getting that, I have to solicit the assistance of those with the skills and interest to help. Skills I do not possess.

As far as aerodynamic correctness from a pure engineering specification point of view, I wouldn't know it if it hit me in the face. I do know that I enjoy flying what are billed as closely modeled aircraft. The key word here being "enjoy". And although neither a pilot nor an engineer, I am somewhat familiar with aeronautics and the general characteristics of flight, and have both flown and air-crewed aircraft, specifically the subject of this thread. Relying on my aged and sometimes feeble memory, this model, in the subject flight characteristic area, doesn't behave the way I believe it should. Hence, my request for help in determining if this perceived flaw could be corrected to the point of "feeling" right, right as opposed to "good".

So, please forgive any misunderstanding. And I'm still looking forward to any tweaks or ideas for tweaks that will bring about the desired results, which is a more correctly flying Mohawk, at least in this hobbyists’ opinion.

Steve

[Milton Shupe]

Just curious, have you asked the author for a fix?

[aeromed202]

I've tried a time or two over the weeks but my e-mail has been weird. Until it gets straightened out anyone else can have a go.