MiG-21Bis and Bis-B FM Mods

[+baffmeister 1,205]

On 1/5/2020 at 11:59 AM, Coupi said:

In the previous v0.95 you have added an emergency thrust with the Tumanskiy R-25-300 (MiG-21bis Late).

In your v0.96 these data were deleted. Is it volontary ?

The previous emergency thrust levels were overstated based on the flight manual and other sources. The ThirdWire default values are correct up to about 13000ft. Based on what I know now, I would actually have to model LESS thrust above 13000ft to more accurately model the Bis engine performance.

[Svetlin 544]

baffmeister, may I ask you a question? I am using this thread since it is somewhat MiG-21 related as well. I have not had the time to test the new data.ini you offered here, so I do not know, may be the issue I have in mind might have been addressed there. I am writing about the angle of attack the aircraft has on the ground (or the stance as I've heard it being called). The stock TW MiG-21 sits in a well visible nose-up position, while in real life pictures the aircraft seems horizontal or just slightly nose-down (I am not considering pictures of the aircraft on the runway before take off with the throttle up and brakes applied). Is there any way to control  the stance of the aircraft on ground, without affecting the FM of the aircraft? I know out of personal (and rather ignorant I must admit) tests with the CG position entry in the aircraft data.ini file, that by changing the position of the CG, the stance of the aircraft on the ground changes. Changing the CG position does affect the FM though, so I doubt it is the right thing to do. I also know that each aircraft component in the data.ini file has an entry for the weight (for example weight of the nose, weight of the tail, weight of the wing, etc.) and I guess a rather low weight entry for the nose or a rather high one for the tail or other component aft of the CG may cause the aircraft to have a nose-up stance, but I have not messed with that yet. I believe I recall seeing somewhere an entry in the aircraft data.ini addressing just the angle of attack on the ground (it was something like aircraftongroundangle=) and I checked several stock TW aircraft, but could not find the correct entry. Any ideas?

[+Cliff7600 1,148]

Svetlin

I think the entry you're searching is :

[AircraftData]
...
OnGroundPitchAngle=

though it doesn't make much for the stance on the ground.

-------------------------------------
I agree with all you said in your post about the factors that make the plane sits on its wheels.
In my opinion there's something more : the shock animations, or the shock travel value / spring factor /damping factor.
In the game the stock values for the landing gear is too stiff. But if you lower the spring factor value, it doesn't always lower the plane as well.
It might be a combination of all the factors mentioned, but it requires some tests and checking.
The first would be the "ShockStroke=" and the "RollingRadius=" using Mue's LOD viewer, it's easy.

[+mue 715]

From the Thirdwire forum (archive):

Post by ThirdWire » Sat Dec 20, 2008 1:56 am:

OnGroundPitchAngle is the angle the object is first placed, but once the object is placed, its final resting place depends on where your gears are and what their shock values are. So check your wheels data.

[Svetlin 544]

Hi Cliff7600 and mue, thank you both. Fiddling with the gears entries seems less risky, as long as it does not lead to the aircraft exploding on the runway, so I will give it a try.

[+baffmeister 1,205]

4 hours ago, Svetlin said:

Hi Cliff7600 and mue, thank you both. Fiddling with the gears entries seems less risky, as long as it does not lead to the aircraft exploding on the runway, so I will give it a try.

I agree, that's probably the best approach to get what you want. It isn't something that I even noticed but if you get a more realistic look please pass along the edits.

[Svetlin 544]

OK, so by slightly adjusting the ShockStroke and SpringFactor values for the nose gear I achieved a result that satisfies me. The aircraft has in my view a better stance than before.

My current nose gear values are:

ShockStroke=0.33
SpringFactor=0.6

The nose wheel sits well on the ground and during take off, the nose slowly gets raised, the shock gets slowly extended with the wheel staying on the ground until the shock is fully extended and only then the wheel leaves the ground.

 

baffmeister, after checking your data.ini, I noticed room for some more visual improvements.

The first one would be to add the correct ejection seat and we have the KM-1 seat from Florian's MiG-21UM mod (though the seat there is named KV-1, the correct designation of the ejection seat is KM-1 and KM-1M).

 

The second one would be to add 3d parts created by Spillone104 and available here at CA, which consist of new pitot tube and engine detailing:

 

The third one would be to make use of the APU-60-1 launch rail for R-60/AA-8 missile, which (if I remember well) Cocas was kind enough to build by my request:

 

I have a Bulgarian MiG-21bis for personal use with the above improvements added. I am in the process of updating it with your data.ini, so eventually I will have your data.ini with my minor modifications to it to add the proper seat, Spillone104's details and Cocas's porper missile rail. I posted a screenshot of it on page 2 here with the missile rail added to the inner wing pylon. The proper stance in that screenshot was achieved by changing the CG position. Now with the help of the community I am happy to have that stance without negative effect to the FM.

Edited January 17, 2020 by Svetlin

[+baffmeister 1,205]

Thanks for the update ideas. I will test the nose gear edits and look into the other improvements. This project is becoming a long term one but there may be a formal upload at some point in the future so it's good to get information on any past mods that would make for a better package.

[+baffmeister 1,205]

Data.ini for the TW MiG-21F attached. This has the same aerodynamic changes as the latest Bis FM's. The rack/rail weights have been adjusted based on the Bis info and I added Svetlin's nose gear edit but forgot to have a look at it in game.

The ammo load out has been increased to 60 rounds, based on information obtained from another thread. There may be a possibility some early Soviet versions only had 30 rounds but it seems like the 60 round load out was standard by the time the type was getting exported.

Canopy is on Shift0[zero]

The lighter weight MiG-21F seems to have a bit better chance of getting a guns solution at the low end of the speed range but I'm a bad shot and haven't managed it yet. I did do some successful evasive maneuvering in the low speed range and think you can probably force an overshoot against most of the ThirdWire types but watch the sink rate at low altitude.

Here it is: MIG-21F_DATA0.96.zip