F/A-18 C/D aircraft mod and textures (FSX/P3D)

[hd764jvgd843]

Thanks Pat, that's a ton of useful information concerning the engines, much appreciated.
I won't have much time in the near future, so I will focus on reading and getting a general understanding of how the engines work in the sim.

Lately I have been thinking about some other questions that came to my mind, too:

1) Currently when additional weight is added to the plane (fuel, loadout, etc.) it becomes easier to pull high AoAs, at slow speed with a given amount of stick input involved. This means, at the end of a flight when most of the fuel is gone, the maximum AoAs one is being able to pull during tight turns at slow speed is reduced. I do not know weather a real Hornet would behave in a similar way, my general understanding would say no, respectively the other way around, but I might be wrong.

2) One other thing that always kept me guessing is the elevator efficiency. Is it too strong or too weak? Against what can we actually benchmark it? My personal routine for testing/setting up the elevator efficiency is right after takeoff at sea level, at slow speed, with max dry thrust, during a tight turn/circle I try to reach 30-35deg. AoAs. with max stick input. Currently we use a V-shaped (linear) function for the elevator control (table 341). I have always wondered weather it would be more U-shaped (progressive) in real life or rather linear, as is?

Maybe someone is able to shed some light onto these questions or knows someone who might know such things, and might be willing to provide some additional information we could use.

Best regards, Peter

P.S. Glad to hear Sludge is back on the forum. A few years back it was his mod that got me interested in the legacy hornet first, and was the reason I always came back to simming and finally to modding. Sincere thanks!

[PhantomTweak]

Hello all!

Peter:
In addition to the two threads I posted from the FSDev forums, I was reading through Yves Guillaume's PDF Flight Dynamics in MSFS V1.0 After several hours of study of that, I got, besides a headache, totally and completely twisted sidewise trying to keep the interrelations involved straight in my poor old addled brain (well, addled NOW! ). What I essentially came away with was that your two questions are interrelated in a very complex fashion. I believe the short answer to #2 is basically that it changes with CG (like fuel weight, payload etc). This leads us back to question #1 in that the AOA is easier to change at higher weights has to do with how MSFS (including FSX) treats elevator effectivity overall vs "hand forces". It seems MSFS is designed for Joystick control, where the force is zeroed be returning the joystick to center. This is much like a stabaug system. Thus, the more weight on the bird, the same motion of the joystick causes a greater change in the pitch (or roll, or yaw) moment, since there is more mass available to "help" or increase the pitch moment. Thus, to my thinking, more weight, more moment per "hand force" or joystick movement per unit deflection of the joystick.

All this has complex math involved, but Yves does a pretty good job of explaining it all, to my mind. The PDF is readily available on the net, and in the FSDev forums, although I had to use Google to find the thread it was posted in. I just put Flight Dynamics in MSFS V1.0 in the search box and it was the second down. The first DL location Google gave required registration (Free) and I just didn't want to spend the time.
I thought you already had this PDF, but if you don't, I can put the zipfile up on ZippyShare for all, should you wish.
NOW, I am going flying to relax
Pat☺

[hd764jvgd843]

Hi Pat, thanks for your explanations, this really helped a lot. I already have the document "Flight Dynamics in Microsoft Flight Simulator" by Yves Guillaume, but I have only read a few passages so far, in particular pages 14-15 concerning the moments of inertia.

When I understand you correctly, the only thing I could do so far is to tweak elevator efficiency specifically for each model version/loadout so they will each have roughly the same behaviour according to their specific weight. All other aspects seem to be inherent to the system of the sim and cannot be changed. Thus, I will consider specific elevator efficiency tweaks for each model version/loadout for the next upgrade.

This leaves only the following questions open for debate:
a) How strong/weak should the general elevator efficiency be, e.g. max. AoAs at slow speed during a tight turn at sea level, with max. dry thrust and full stick input, the airplane should be able to reach? How would a real legacy Hornet behave in this situation, would the elevator deflection be strong enough to put the plane into a stall situation and would this be tolerated, or would this be countered by the FCS as a deviation from controlled flight path and the elevator deflection thus be limited?
b) Should the elevator function be linear (V-shaped) as it already is or rather be progressive (U-shaped) in order to empathize the correct flight behaviour of a real legacy Hornet?
c) Is the elevator efficiency function symmetrical or asymmetrical for up and down pitch in a real Hornet? Currently, the down pitch is slightly decreased (flatter angle) in comparison to the upward pitch - is this realistic?

Peter

[jimi08]

Peter,

Seems like you are starting to arrive at the same point that I am at and where Orion and I have been working in regards to the PIDs.

Your questions assume that stick movement directly correlates to stab/elevator positions when in reality it does not.  Stick positions correlates to either AOA or G.  If commanding G, then the stabs will move more at slower speeds to give the pilot the G that is requested based on the stick position.  If at lower speeds (below corner) then the stabs will adjust to give the pilot the correct amount of AOA as requested by stick position.

Last I checked cornering speed of the legacy is around 310 KIAS.  In theory, that should be the lowest speed in which the Hornet can reach 7.5 Gs.

In regards to a linear or exponential, I think it is more a matter of preference.  In our 2012 release, we used curved which provided nice fine adjustment flight characteristics near stick center, but still provided the "umph" needed to pull hard Gs.  The linear approach provided predictable pitch characteristics through the entire pull.

Being that the max pos and max neg are different, I would imagine that the logic would be different to match max G pos/neg with max pull or push.  A pull all of the way back would command max G of 7.5, while a push all of he way forward would give you neg. 3 Gs.  In order to accomplish this, the elevators need a little less "bang for the buck" while pushing.

But all of that is null and void if you are implementing PIDs for G and AOA commanded inputs.

Another option is to get SLUDGE's inputs since he has direct access to the Growlers/Grizzlies sims.  It's not Legacy, but far better than nothing.

Hope this helps.

Hope this helps.

[PhantomTweak]

That was going to be my next answer, too. Ask Sludge, since he works with the Navy's training sims, which are gaining more and more popularity (or at least use) in the tighter budget environments of late. Costs a lot less in maintenance and fuel to fly a sim, not to mention a lot less cost in ejection seats
As to how a real-world Hornet flies, other than what I can read in Approach magazine or other sources on the net, or ask in various forums, I haven't a clue. I was foolish enough to drop plans for college (Stanford or Davis) and go active USMC because I was mad at my parents. Boy I really showed them, huh? By the time I managed to get through all the hoops for MECEP (Marine Enlisted Commissioning Educational Program or they pay for my college, I stay in X years as an Officer), I was too old for flight school selection. Pretty dumb of me, I realize, but anyway...
I would suggest getting ahold of some of the real Hornet drivers in the General FSDT forum. Seems to be more than a few  on there, off and on. They may or may not have the mathematical details, but the anecdotal evidence can be invaluable.
For the linear vs exponential curves of R341, which is actually only a part of how "effective" the elevators are, first, you can trying making one of each, NO other changes to the .air file, same exact conditions, like fuel, payload, temp, pressure etc etc, and try your test (the high AOA low level edge of stall turn), as close to the same way. Same speed, same thrust, same G, same AOA, etc., and see which seems more "realistic". To you. Again the trick, I believe, is to isolate a single variable at a time, as much as possible. Being humans, we are far from perfect, but you should be able to get pretty close, I think. Second, I believe, although I may well be wrong, that to get a decent exponential curve to R341, you would need more X,Y pairs. Most of those tables are limited as to how many pairs or data points are permitted per table, so you may well actually have a less linear curve than you think from a glance, there's just so few data points it's not obvious visually, again, at a glance.
I have tried making some (very) small changes to R341, and studied the effect, but again, a real Pilot I aint, and a test pilot I am far from. I've also made some other minor .air file changes. Once I am "statisfied" (statistically satisfied I love English!) it's flying like I believe it should from all I've gathered, I'll send you a copy of the .air file.

Last I checked cornering speed of the legacy is around 310 KIAS.

Jimi, again I owe you a huge debt of thanks!! I've been looking for that tidbit of info for the longest time!!! And you just casually pop it out. Wow, all I can say.

Keep the clean side up, and for Heaven's sake, do NOT depart down that low
Pat☺

[PhantomTweak]

Jimi, hi! I forgot to ask last night: May I ask under what circumstances one would input extra/manual (pedal??) rudder during maneuvering? You mentioned that the FCS handles the rudder for coordinated turns, but you also mentioned that the Angels in particular tend to utilize rudder a LOT. Ok, do they/you (whatever) turn the FCS off (Master Arm ON) during specific maneuvers, all maneuvers, no maneuvers? Do you add rudder on top of the FCS inputs? I thought that reset the rudder inputs from the FCS. Did you mean the FCS makes large rudder inputs, as seen on the data page (shft-8) that is available? Speaking of the Data Page, on the NH Hornet version Peter put out, it shows the flaps system "OFF" under all conditions. no UA, no landing configuration, nothing, even when IN landing config (under 33K Gross weight, Gear down, Hook down, Flaps FULL selected) . Is it just not sensing the Flaps system operation for some reason? I am thinking of starting to burrow into it's XML file (please don't let it be a .GAU file!!) to see what I can see, just thought I'd go the easy route first Please see the attached JPEG for an example. The lower left part of the page. Note that several other things, whose gauges I know are in the Panel.cfg also are inactive according to the Data Page, like the G-LIM and ROLL-LIM features. The T/O trim /Landing Trim and ATC off is understandable, since they were, in fact, off. I haven't looked to see if they show ON at the appropriate times or not, but i will right now...
I'm just trying to fly right, as the saying goes.
Thanks again for all the help you are kind enough to give. I sure appreciate it!
Pat☺

[jimi08]

Pat,

Rudder is part of the Blues technique for keeping close formation.  Instead of banking left and right to keep proper lateral separation, the use rudder.  That way, all of the wings in the formation are not rocking back and forth and they appear to be solid and "welded together"

If you watch the diamond takeoff and as the #4 pilot transition into the slot position, you will see him using rudder as well.

On our team, we do not turn off the FCS.  The systems continues to add rudder (via use of rudder trim event) to coordinate turns and adds any additional manual rudder provided by the pilot.

As far as the data page, that FCS system needs to be updated.  Many of the gauges and parameters that was read by that gauge has been changed such as converting them from XML to C++.  Just need to updated/reconnect some of them.

Hope this helps.

[Orion]

On our team, we do not turn off the FCS.  The systems continues to add rudder (via use of rudder trim event) to coordinate turns and adds any additional manual rudder provided by the pilot.

I thought the current setup uses the AXIS_RUDDER_SET key event (actual rudder position) to coordinate turns (only when user input is rudder neutral) and uses rudder trim for RSRI?

[jimi08]

I'm think that's the setup for the PID version that you and I are working on.  The team hasn't transitioned to that one yet.  And I dont think that Peter and Pat are flying that one either.  If I remember correctly, the one they have has an algorithm that sums up rudder output needed for coordinating turns and for RSRI and sends as a numerical value to rudder trim.  Leaving normal rudder to be used as normal, thus adding or subtracting to what is already there.....i think....

Gonna have to take a look once I get back home.

[PhantomTweak]

Thanks Jimi! I wasn't expecting such a quick response. I knew about how the rudder was used in formation flying. Believe it or not. When I was 14 and learning to fly gliders, that's exactly how we "boxed the wake", a precision exercise when on the tow plane. Normal position is slightly above and centered, hence above the wake and in view of the tow pilot who has a "window" in the upper fuselage over the cabin (on a high wing) with a large rear view mirror, but for the exercise, I was expected to make a rectangle or square around the tow plane's wake. If I dipped a wing during the horizontal slide to the side top and bottom, I got smacked in the head. My IP had amazing accuracy with that yardstick. It was used to indicate to the tow pilot a desire to deviate from the briefed target for drop-off, indicating for him to go away from the position of the glider relative to his wake. Above left, please turn right level, that sort of thing. We didn't have radios in the gliders.
I had thought you meant that during certain maneuvers you used more rudder than just the FCS provided. I am utilizing what Peter terms the NH  model he has on page one of this thread. I am pretty sure it utilizes the same FCS system as the FSX BA 15.2 version, if that helps any.
So with this system, it sums the output from the RSRI xml, if any, with what it generates internally, so to speak, and applies that summation answer to the rudder trim of the aircraft, if I understand correctly, yes? This being enough to coordinate a "normal" turn at "normal" AOAs, but things like formation flying, or abrupt maneuvers at very high AOA's, or whatever, the rudders are fully available for pilot input, correct? That's the way I'm reading it, anyway. But with the new PID system, all this will change? I'm just being nosy, is all I think that's what Mr. Orion was indicating, anyway. I look forward to any new changes, since they always seem to be improvements.
Thanks again, I appreciate the responses. Helps me wend my way through all this
Pat☺

[jimi08]

Pat,

The way it your rudder should work right now is indicated below:

Turn Coordination (Angle of Bank + Airspeed)  +  RSRI (Lateral Stick Input + Airspeed) = Rudder Trim Output

Airspeed is used to increase rudder trim output as speed is decreased.

[PhantomTweak]

Thanks for explaining it in such simple terms this poor drug-addled (not by choice. No drugs, no walking or sleeping. All prescription and legal, I swear) brain can grasp quickly and easily. I'm not EVEN going to ask about the "new" method. Best of luck to you and Mr. Orion on it!

Peter: I had a thought, for when you choose to take a break from the Math and control surfaces to do more textures. VMFA-333, Trip Trey as we called it. I can dig up some pictures if they would help. That's the last squadron I was in just before I got out. On their last trip to Iwakuni, Japan, in F-4's, a C-141 ran off the runway and ended up sideways right about where our maintenance van complex had been placed until the night before. Very near the barracks we had just vacated. I have some pictures of it. NOT taken by me They trashed the model airplane field though. Some very upset folks about that. ANYWAY...
Just a thought. They transitioned to F/A 18C's just (3 months) before I got out. I didn't want to be afloat 8 months a year. Besides, the Radar shop went from component level trouble-shooting and repair to "plug it in, verify bad board, return board to depot, LRU to squadron" maintenance. Just not my style. But I am sure that if they are still active, they have paint jobs like the Phantoms had. Might be a nice bird to fly in, for old times sake.
Just a thought, anyway Great day and fair skies to all!
Pat☺

[hd764jvgd843]

Hi Pat, I will put in an USMC_VMFA-333 texture with the next release. Currently I am busy, so it will probably take a little while.

Best regards,
Peter

[PhantomTweak]

Very cool, Peter! Thanks much, I appreciate the thoughtfulness. No worries about rushing to get it. I am way too slow to ever hurry any more 
Pat☺

[PhantomTweak]

Hey all!
Peter: I found how MSFS calculates CDi, or the total Induced drag index. Mostly, it's R404 involved, but only a very narrow range of it, interpolated out linearly. 0°-10° to be specific, interpolated out to +/-30°. With R401 and the Oswald Efficiency factor for high Mach numbers, if necessary. It includes also CDo, R1101_17, I think. As usual, very convoluted. Point being, perhaps adjusting the two points in R404, the 0 and 10° points will accomplish what you desire. And adding in a R401, if necessary. I am giving it a try even as we speak. Remember that the scalars in the [flight_tuning] section are just mutlipliers. Also, Yves specifies that the flaps raises the entire CDi curve , not sections, or affects the curve of the curve, so to speak. 
I gleaned all this from page 25 down, and Appendix 2 of Yves' PDF. I don't know if this will help at all or not, but I thought it might.
Pat☺