Updating Ivan's Jurcaga's MiG-21MF

#1
Hi everyone. I recently undertook to work on the excellent MiG-21MF by Ivan. It appears Ivan is no longer supporting the model, so the work will proceed without access to the model source. Nonetheless, there are many things that can be done to get it improved.

This thread is for those interested to discuss and make their voice heard in the development of the upgrade. Feel free to respond with your thoughts if you are interested in the project.

Disclaimer: I don't have unlimited free time to work on this, nor can I change the model. But I am interested in a project to make the MiG-21MF fly and fight more realistically than it currently does. So I have committed to spend some time on this. I can't promise exact completion dates.

Here are the priorities as I see them:

1) Fix the FDE. In doing this, I am using the DCS MiG-21Bis as my model for roughly how this airplane should fly. The MF and the Bis are different, with the Bis being heavier but with a larger engine to make up for it. They won't fly exactly the same, but it isn't possible to get an FSX airplane flying exactly like a DCS one anyway. However, the performance and fuel burns should be roughly the same, and I will try to reproduce climb, turn, descent, and landing numbers as close to the DCS as I can.

2) Add an RP-21 or RP-22 Radar. I have the update to the Jurcaga MiG-21 model that allows access to the radar area in the VC. I am coding a custom written gauge that should simulate an authentic MiG-21 radar experience. Exported MFs had the -21 which has a little less range, less jamming filters, and could not act as guidance for the R3R missile. Domestic Soviet MFs have the RP-22 like in the Bis. I am likely to implement both and let the user select which one. As a practical matter, in FSX, they are almost identical.

3) Various fixes to the systems to make them work more accurately, and provide an English cockpit.

4) Implement weapons to the extent possible, both CS Weapon and Tacpack.

5) Provide some optional more modern navigational options (perhaps the KLN-90B).

Your input is welcome.
Dutch
 

Heretic

Resource contributor
#2
I'll be watching this, as promised.

Does "english cockpit" mean english tooltips or english labels?
Tooltips only would keep up immersion, but I don't know if their weird behaviour in DX10 (no-show when in fullscreen) has ever been fixed.
 
#3
The best would be an option for either original or English in the cockpit. It would involve the renaming of one texture, I think. Maybe two.

Yes, DX10 won't show tool-tips in full screen.
 
#5
MiG-21MF had a RP-21MA Radar.

I saved a file with personal handwrited notes of a MiG-21 pilot or something close. In these notes he explain things about RP-22 and the ASP gunshight. Sadly He was banned and his account deleted in ED forums so I dont remember who is the author but the info is good. But the text is in cirilic letters. DOWNLOAD
 
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#6
Hi, just a note... 21 Bis is a fairly different bird... and this one was flighttested by Czech/Czechoslovak pilots, so it is pretty close. There was a bit of an issue with afterburner thrust, but otherwise it should match MF performance.
 
#7
In the original Jurcaga release (without any of the user-developed FDE mods) the MiG-21MF was considered an under performer that used too much fuel, according to many of the comments I read. Not that that matters a lot - I suspect many simmers want their fighters to fly faster and consider an accurate sim to be under-powered sometimes!

The user mods that came later increased thrust for performance and reduced fuel consumption. But this could never work out right without an afterburner -- the increased thrust made the non-AB performance far too powerful. The reduced fuel flow scaler reduced fuel flow to non-AB rates but didn't account for the far higher fuel flow with reheat on.

I added a two-stage afterburner, and it makes quite a difference. Without the AB, it could barely make mach 1 in level flight. Which is accurate, at least for the 21Bis too. It will build to about 1.1 in level flight at 5,000 meters.

The 21MF needs the afterburners to get to 2.0, and it now flies much faster with it on. However, even with the afterburners, currently it will only get about mach 1.5 at 10,000 meters. Which matches the 21Bis performance with the UB-32s attached. Without the UB-32s, clean, it should get to 2.1. But the FSX version won't so far. I'm working on that, increasing afterburner thrust without affecting non-AB performance.

With the burners on it drinks much more gas. Accurately, according to the 21Bis numbers.

Unfortunately, adding an official afterburner makes it incompatible with FSX SP2 - it will require Acceleration, P3D, or Steam to use it.

The problem of drag I'll mention later. I need to increase drag when weapons are attached.
 
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#8
The original release was underpowered under afterburner a bit; a later patch was available to make it match afterburner power, but overpowered on normal power.

MiG-21 is not a very fuel efficient aircraft, what I recall the fuel figures worked well.

I hope you don't take this wrong, but there were indeed some user modifications, even very early on after release, that totally butchered the dynamics, and I'd just like to make sure you understand that the plane flies quite realistically already, so there is not that much need for changes (even well meaning.) Well except for exactly what you mention - as mentioned, it was a tradeoff between normal and afterburner power. Not sure if you can get a patch for afterburner from Ivan. Used to be on now defunct migsim.ic.cz page...

One of those early user modders was particularly funny, basing his dynamics on airshow displays and flying from tower views, and asserting his authority on basis of being a PPL holder with Night rating...
 

Heretic

Resource contributor
#9
I remember that discussion about the FDE. It can still be found in the Flightsim.cz archives.

One issue I've had with the original .air file was the latent instability. I just can't imagine that the bird is that wobbly.


Dutch: (Afterburner) Performance and mach drag were adjusted by me in the .air file, so you can use the table for inspiration. I've trimmed it for mach 2.1 in a clean configuration with 15 or 20% of fuel at 30 to 40 thousand feet.
 
#10
I have been making small, careful adjustments based on the original. I'll post up some numbers on climb and cruise performance with speeds and fuel burns in a while.

I agree some of the user mods to the FDE departed reality, from what I've seen. I've tried all I found to get a starting point for my own investigations. The original came closest.
 
#11
Here are some numbers, comparing the DCS MiG-21Bis to the original release (with no user mods) of the MiG-21MF. The impression that the MF is significantly under-powered seems to hold very true.

We're comparing climb profiles on a clean airplane (no weapons.) The procedure is a takeoff at sea level with no wind at 20C. Full afterburner (throttles fire-walled) for takeoff, with trimmer set at recommended settings for each airplane, neutral for the Bis, and with the trimmer light lit for the MF.) After liftoff, retract gear and flaps, set to full military power (the point just under where both afterburner lights are off.) Climb straight ahead at 2000M per minute to 10,000 meters and level off. (All readings are from the instruments and are in metric.)

For the DCS 21Bis the aircraft nose is lifted at 250 and liftoff occurs at 330. At 1,000 meters speed is 550; at 5,000 meters speed is 810, and at 10,000 meters speed is 580 (mach .82) with a total fuel burn of about 600L.

For the Jurcaga 21MF the nose is lifted at 250 and it flies immediately. At 1,000 meters speed is 600. The 21MF will not reach 5,000 meters without the afterburner lights lit. Speed will drop off until it stalls at about 4,000 meters at below a speed of 300. At full power for takeoff with both AB lights on, the N1 needle shows about 90%.

Changing the profile to use full afterburners all the way:

The 21Bis reaches a speed of 900 at 1,000 meters and 1400 (mach 1.4) at 5,000 meters, while burning 1200L of fuel. The engine flames out at 6,000 meters because on the DCS simulation you can't abuse the afterburners for that long without consequences.

Flying the 21MF at absolute full power all the way to 10,000 meters results in a speed at 1,000 of 700; at 5,000 meters we are at speed 1,050 (mach 1.0), and at 10,000 we have reached a speed of 830 (mach 1.12) with a total fuel burn of 900L.

I know the MF is not a Bis, but I can't believe it's that different.

Afterburner fuel burn is way too low, 900L to get to 10,000 on full AB, whereas the 21Bis has already burned 1200L just to get to 5,000. It does need to be able to reach 10,000 meters without an afterburner on.

We're never going to get this to match the DCS numbers exactly, because their flight modelling is superior to anything we can get out of FSX.

We can only fix the ones that are way out of proportion. Like fuel burn and basic speeds in basic situations.
 
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#13
It is from the original ZIP distribution I downloaded. Could you send me your aircraft.cfg and .air files? That might help.
 
#14
Where we stand with the FDE mods I am working on.

On the non-AB climb profile test as mentioned above, my modified 21MF has the nose up at 250 and lifts off at 320 (very close). At full military power it reaches a speed of 800 (vs 550Bis) at 1,000 meters. At 5,000 it is flying at 950 (vs 810 Bis); and at 10,000 meters it is pretty close to the Bis numbers, speed 550/mach .81 (vs 580/.82) with a total fuel burn of 700L (vs 600L.) I will tweak fuel flow to get it down a bit. The real problem here is the 5,000 meter numbers which are too high. But if I reduce the thrust_scalar to make those numbers right, it will barely even climb to 10,000 without AB. I need to modify the .air file to reduce the performance loss as altitude is gained, and that's something I will have to learn about.

Here are some details of what I've done.

1. In the aircraft.cfg the numbers are from the book, empty weight of 12880LB clean, with a static thrust of 14550. (The original had a weight of 25,000LB and a thrust of 12,665.)

2. I have adjusted the thrust_scalar to 0.90 and the fuel_flow_scalar to 1.20 plus tweaking the 1502, 1503, 1504, and 1505 records in the .air file to get those numbers and to make the N1/N2 numbers correct.

3. I have modified the locations of the pilot, added weapons stations, and adjusted the fuel tank locations. Now the CG and therefore takeoff trim is more reasonable.

4. I modified the 1524 record for afterburner thrust in the .air file.

5. I added a "true afterburner" (not available in SP2) by adding these records to the aircraft.cfg:

afterburner_throttle_threshold = 0.90 // Percent of throttle range where a/b begins
ThrustSpecificFuelConsumption = 0.81 // Thrust specific fuel consumption (Jets)
AfterBurnThrustSpecificFuelConsumption = 0.77 // TSFC with afterburn/reheat engaged

The biggest problems I have now are the altitude thrust loss, and the fact that it rolls at almost idle thrust, whereas the 21Bis will not move even with no brakes on until about 65% N1.

The other problem is afterburner thrust doesn't work so well at altitude, but I think that will be fixed when I fix the altitude thrust loss problem.

The other looming problem is drag from weapons. Particularly the UB-32 which cuts the 21Bis numbers dramatically down. We'll cross that bridge once we get the basic clean flight pretty much right.

None of this addresses combat performance like turn radius, we will see what we can do with that, but I doubt we can get close to reality given that FSX is not a combat sim.



PS. Edited to add this link to a good discussion here on thrust loss vs altitude and why FSX gets it so wrong: http://www.fsdeveloper.com/forum/th...rease-with-increase-in-altitude-in-fsx.34404/
 
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Heretic

Resource contributor
#15
Set thrust_scalar and fuel_flow_scalar to 1.0 each and work the airfile tables instead.

Also make sure to adjust the 400 series of tables to get the basic coefficients and drag right.
 
#16
One of my biggest concerns is lift. The airplane seems to have too much of it. For example, if on landing, at 350 KMH, at 100 meters AGL I cut the engine, it will float on in and land perfectly.

The same thing done with the DCS Mig-21Bis, and it sinks like a stone and ploughs up the ground way short of the runway.

Those delta wings just don't give much lift. As soon as the engine is cut, down you go at a steep angle, specially with gear and flaps out.
 

Heretic

Resource contributor
#17
One of my biggest concerns is lift. The airplane seems to have too much of it. For example, if on landing, at 350 KMH, at 100 meters AGL I cut the engine, it will float on in and land perfectly.
That's due to the ground effect. I think there's an .air file table somewhere to adjust this.

I case you haven't done so already, get AFSD and Yves' documentation of the FSX FDE.

http://www.aero.sors.fr/designer_pilot_utilities.html
http://library.avsim.net/download.php?DLID=170811
 
#18
Hi everybody,

It's been a while since an update, but we're getting close to a beta for this upgrade. I have been working on important revenue projects (the kind that pay my bills!) and so haven't been able to put huge time into this, and that will continue for the foreseeable future. But still, since early January, I've been able to add cockpit sounds, overhaul the systems, rebuild the FDE, add weapons, and install a realistic RP-21MA radar system.

I hope to get a beta posted up for testing in the next few weeks, but most of my time in spent on a development project that won't be done until mid-May at the earliest. But all questions and comments are welcome.

Meanwhile, here's a video of a demo flight involving engine start, takeoff, intercept a drone and shoot it down, then return and land.

Enjoy, and stay tuned for the posting of the beta code.

Thanks!
Dutch
 

Heretic

Resource contributor
#19
Missiles and destructive testing of their functionality are courtesy of TacPack, I presume?

Other than that, I can't wait.
(Hopefully, some of my code survived.)
 
#20
Not Tacpack but Captain Sim weapon in this video. I plan on adding Tacpack, but that's a much more substantial effort than the much easier and cheaper CS weapon.

However- Tacpack will allow me to implement the R3R SARH missiles and integrate them with the radar. CS weapon doesn't have this capability. It has radar guiding missiles but they are locked on from the CS HUD, I don't know of a way to lock on a particular target outside their system.
 
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