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Can you post also the first part of table 28 and probably the next page after this table, as looking at this part of the table alone, I cannot figure out the meaning of PX, X, P, У and PУ.

I think I can help with the translation of the rest.

 

Chapter VII - Weight and balancing characteristics

Table 28 continued

===============

Table headers:

Name / PX (measured in kg) / X (measured in meters) / P (measured in kg) / У (measured in meters) / PУ (measured in kg)

==============

Under the wings

==============

Inner pylons loadout

==============

R-2R missiles loaded (2 pcs)

--------------------------------------------

pylon BDZ-60-21D

launch rail APU-13U

R-3R missiles

==============

R-55 missiles loaded (2 pcs)

-------------------------------------------

pylon BDZ-60-21D

launch rail APU-68UME

R-55 missiles

===============

R-13M missiles loaded (2 pcs)

--------------------------------------------

pylon BDZ-60-21D

launch rail APU-13MT

R-13M missiles

==============

UB-16 rocket pods loaded (2 pcs)

--------------------------------------------

C-5M unguided rockets (16 * 2)

rocket pods UB-16-57UMP

pylon BDZ-60-21D

===============

OFAB-100 bombs loaded (2 pcs)

---------------------------------------------

pylon BDZ-60-21D

bombs OFAB-100

===============

Unguided missiles S-24 loaded (2 pcs)

---------------------------------------------

pylon BDZ-60-21D

launch rail APU-68UME

unguided missiles S-24

===============

OFAB-250 bombs loaded (2 pcs)

---------------------------------------------

pylon BDZ-60-21D

bombs OFAB-250

===============

UB-32 rocket pods loaded (2 pcs)

--------------------------------------------

pylon BDZ-60-21D

rocket pods UB-32A

C-5M unguided rockets (2 * 32 pcs)

===============

Incinerating canisters ZB-500 loaded (2 pcs)

-------------------------------------------

pylon BDZ-50-21D

ZB-500 incinerating canisters (from me - something like napalm bombs I guess)

================

 

By the looks of it, the table shows parameters with various types of weapons loaded, giving first total amounts for the whole unit loaded under the wing (weapon+pylon+launch rail) and then giving a break-down for each component - the weapon alone, the pylon alone, the missile rail alone (if one is needed for the weapon; naturally no missile rails needed for bombs and rocket pods). Hope that helps.

Edited by Svetlin

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Thanks Svetlin. This page looks like the introduction for the weight and balance section I've posted:

RackWeight2.thumb.jpg.4329f18783f1c28f9bfc2742bb7762b5.jpg

This page has some info on the 490 liter drop tanks at the bottom of the page:

RackWeight3.thumb.jpg.ceeaaac04acaaf5cec0abda5a57fd64e.jpg

There is another page that I haven't posted that shows information for the 800 liter centerline drop tank. Not sure when that tank became available and what MiG-21 versions it fits but it might be a nice add-on project for someone. ThirdWire only made the 490 liter version.

 

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Hi, I will translate these for you as well, but after a quick glance at the 2 pages, I still cannot make out what PX, X, P, У and PУ mean.

As for the 800L drop tank, that could be loaded under the fuselage, from what I have read at www.airwar.ru, the tank was first introduced on the MiG-21SM (first flight in 1967) and was available on all subsequent variants such as SMT, M, MF, bis.

I am not 100% sure, but I am willing to believe that the subject 800L drop tank was later used also on the MiG-23 and we do have that tank stock in SF2.

In fact I have modified the MiG-21s in my install to carry the MiG-23 800L drop tank and it fits quite nicely, here is a proof of concept :wink:

image.thumb.png.aa3d38c4da89a8b44080fab5b33fec0f.png

Edited by Svetlin
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OK, now here goes the first page:

Aircraft Weight Summary

In order to calculate the balance of the aircraft at the possible changes in aircraft construction and equipment, the weight and center of weight of various aircraft equipment and systems are listed. Aircraft balance calculations are performed using the X and Y axis. Axis X is the aircraft longitudinal axis and matches the aircraft constructional horizon. The Y axis is perpendicular to the X axis and is vertical, situated 600 mm towards the aircraft tail from frame #16. The point where axis X crosses axis Y is the starting point in the center of weight position calculations for the aircraft, its systems and each component, which is part of the various aircraft systems. The coordinates of systems and components, situated in the direction of the aircraft tail on the X axis and up vertically on the Y axis, have a "+" sign and those towards the aircraft nose on the X axis and down vertically on the Y axis have a "-" sign.

(Picture 92 shows the location of the balancing axis)

Weight summary and load balance and the main equipment with respect to the centering axis are listed in table 27.

Weight summary and balancing of loadout with respect to the centering axis are listed in table 28.

Weight Summary and load balance and main equipment

Table 27

===============

Table headers:

Name / PX (measured in kg) / X (measured in meters) / P (measured in kg) / У (measured in meters) / PУ (measured in kg)

==============

Aircraft with normal load (landing gear is lowered position)

Empty aircraft

Normal load

Normal load

Pilot with parachute

R-3R missiles (2 pcs)

Cartidges (250 pcs)

Fuel in fuel tank #2 V = 830L

Fuel in fuel tank #3 V = 340L

Fuel in fuel tank #4 V = 175L

Fuel in fuel tank #5 V = 245L

Fuel in fuel tank #6 V = 185L

Fuel in the front wing tanks V = 360L

Fuel in the rear wing tanks V = 220L

Fuel in the fuel tank on the aircraft back (in the structure behind the canopy that flows into the aircraft vertical tail) V = 530L

Launch rail APU-13U-2 (2 pcs)

==============================

The other page will follow probably tomorrow.

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It might be starting to make some sense. Using column P, the aircraft empty weight is 5843kg,  2883KG is the full internal fuel+pilot+missiles etc, and 8726kg is the sum of the parts.  That's important because now I know which column to look under to get the weight of various racks etc. X and Y columns, as you mentioned, are the length of the horizontal and vertical arm, in meters, from the center reference point. PX and PY might be the resulting moment of the weight times the arm but that doesn't seem to quite work out. Using the two 490liter drop tanks the chart shows 940KG under P column for the mounted tanks and an arm of +1.34M under the X column. If I multiply those together I get a moment of 1259.6KG which is close to the 1257KG under the PX column but, not exactly.

Anyway, that's been a big help!  :good:

Edited by baffmeister
mistake

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After looking through the rack weights it looks like there is some room to save some weight. Keeping in mind the posted documents show the weight for 2 racks, they seem to average around 30-35KG each, with some variation probably due to additional hardware required for certain weapons. ThirdWire is using 60KG for each main rack. On the other hand, the weight of the missile rails from the document are heavier than the 25kg used in the ThirdWire data but overall, with a full loadout, the weight reduction would be around 100kg.

I checked the fuel plus tank weights for the 490L and 800L tanks and the ThirdWire tank+fuel is lighter than the document weights but the document info indicates a bit more fuel available. For the next update I will probably leave the tank weight/capacities as is but will include Svetlin's idea of using the 800L MiG-23 on the center pylon. It does look like the correct tank, from the diagrams in the document.

Svetlin, I don't need any more translations for the previous documents but could you take a look at this one? I'm checking the deflection angles for the control surfaces and the TW rudder and ailerons match the documents but the H-Stab is different. I'm quite sure the red box I outlined is for the H-Stab but I'm curious about the statement underlined in yellow:

5d62b046481da_MiG-21H-Stab.thumb.jpg.967dad6a69f9783acafec5badd3432ae.jpg

For anyone interested, here's the info, at the bottom, for the 800L centerline tank.  The way the fuel weight is divided might indicated the 490 and 800 liter tanks had 2 compartments:

MiG-21-800L.thumb.jpg.f3edc120cd5a0848cd3f4bd2882d8541.jpg

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Hi, my pleasure, here it goes.

 

Chapter II - Geometrical data

Horizontal tails

a) moving surface

Area

Mean aerodynamic chord (MAC) of the moving part of the horizontal tails

- along the air flow

- perpendicular to the rotation axis

Spread

Sweep angle at 1/4 MAC

Elongation

Waist

Cross angle V

Relative thickness (along the air flow)

Profile along the air flow

Horizontal tail shoulder (distance from wing 0.32 MAC to 0.25 MAC of the moving part of the horizontal tail)

=======================================================

Here is the part you are interested in:

Deflection angles along the air flow (maximum angles at high level setting of the automatic booster control)

- front part of the stabilizer turned up

- front part of the stabilizer turned down

Sweep angle of the stabilizer rotation axis

Location of the rotation axis in % from the MAC of the moving part of the horizontal tail

========================================================

b) with ventral fin

Area

Spread

Mean aerodynamic chord along the flow

 

Vertical tail (fin)

(without the ventral fin)

Area of the vertical tail

Mean aerodynamic chord

Sweep angle along 1/4 MAC

Elongation

Waist

Relative thickness of the vertical tail (mean or average)

Profile along the air flow

Vertical tail shoulder (distance from wing 0.32 MAC to 0.25 MAC of the vertical tail)

Rudder area

Rudder mean aerodynamic chord (perpendicular to the rotation axis)

Area of the axial compensation of the rudder (in % of the rudder area)

Maximum rudder deflection angle (perpendicular to the rotation axis)

 

I must ask you to excuse me as my translation is that of an amateur. I have no technical education and I have only read about most of the technical terms used here, but only in Russian and Bulgarian, so I believe I understand what most of these terms mean, yet my lack of experience with the English terms is rather obvious. So I just hope you are able to make something out of what I am trying to translate as I am sure I am not using the proper English term in most cases.

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I pinged Topolo a message who is the author of many of the HFFM flight models over the years and has done quite a bit of work on aerodynamically modelling the MiG-21s as well and he does confirm that Emergency Reheat value is not static zero airspeed but exactly as that Bis manual states at M1 SL.

 

 

 

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While searching for proper schemes for 1982 Bekaa 21Bis, I found this story, not sure is true, but at least is interesting. MiG-21 doing Pugachev Cobra ( shoudln't the engine flame??)

https://nationalinterest.org/blog/buzz/unknown-story-syrian-mig-21-pilot-who-developed-cobra-maneuver-72081

specially this part...

Mohammed’s initial solution was based on Soviet manuals and consisted of rapid descending turns followed by a sudden activation of the afterburner and a climb. However, in the course of one of related test-flights, in early 1967, Mohammad inadvertently pitched the nose of his MiG too hard, so that the forward movement of his aircraft nearly stopped. When he engaged the afterburner his MiG ended ‘standing on its tail’, with the nose pointing almost vertically into the sky, on the verge of flipping out of control. Mohammad recovered on time to prevent a crash, but it was a close call: in order to prevent this from happening again, he decided to try flying the same manoeuvre after engaging the afterburner, so to enable the engine to spool up on time (the Tumansky R-11 was notorious for its slow reaction to throttle movement).

 

That was the moment that what later became known as the ‘zero speed manoeuvre’ was born.

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in 67 they were flying different MiGs with different engines if you are referring to the DCS Bis - which according to all the Bis pilots that test flew and verified the DCS FM the engine flames out as soon as there is much in the way of negative G especially at low speeds as soon as the nose goes forward. :ok:

That doesn't sound like a cobra........the aircraft that have done that (Su-27 etc) still had some directional stability, likely pitched up to a far higher transient AoA and still appear to be in control and flying when the nose came down.

 

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BTW, is always interesting to read about new MiG tactics against the Mirage III for 1966-73 timeframe.

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Jeanba, thanks for that, curious how close those two planes were. Any MiG-21 expert can explain his tactics here?

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What do you mean ?

No tactics here

Topolo's work is an estimate of performances based an available Flight Manual.

The data and curves were then converted and adapted to a format which made them easier to compare under the NATOPS framework

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I haven't expressed properly, I mean, how you fly in a MiG-21 in dogfight, which tactics do you use?

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As far as I am concerned : Boom & Zoom, vertical plane, high subsonic, high altitude

Avoid Dogfight, missile attack mainly.

Be carefull of improved IRM missiles such as AIM-9D or Shafrir II, compared to AIM9B

The only time I make hard maneuver is to avoid being in the missile arc.

 

I fight in Early VN environments, Six days War (early migs), Yom-Kippur (Mig21MF) and Ogaden (vs F5s or even otehr Migs 21)

Edited by jeanba
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I agree with jeanba. I still think there is some room to improve the low speed performance of the TW MiG-21 but in general you want to keep the speed up. Better, and I think more realistic low speed behavior would improve the defensive capabilities as well as improve the potential for firing solutions during lower speed turns but only in certain situations.

I've been trying a few things with the Bis FM to better match the low speed behavior as described in the flight manual but it involves too much conjecture at this point. I'm still taking a look at the charts from the CheckSix site but I need more data to test against before releasing anything.

From the flight manual, it seems the MiG-21 can easily get into the higher alpha zone while the TW MiG-21 FM tends to get "stuck" at about 28deg AOA. There seems to be a number of reasons for that. TW modeled quite a bit of nose down pitch moment in the stall region and the lift distribution is almost 70% on the outer/aft wing panel which makes it more difficult to get the nose up at low speeds. It will take some research and a lot of testing to see what might be improved regarding the low speed/higher alpha performance.

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I think  that low speed fight in SF2 is very dangerous, especially when you are outnumbered :

It seems  AI is very good at coordinating attacks from several direction, and I was often shot down by an unseen attacker :

"A Mirage in your six is better than no Mirage at all"

 

Edited by jeanba
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