The new critical angle of attack might be too low!

Ok so try the FM and compare with real data. If you find discrepances, post that in the bugtracker and help M3 to improve it.

LOL... nice trolling post. You cant be serious with such attitude.

And what is the right attitude?

Complaining without data reference? This is wrong because i think is wrong?

There are tables available for the Mig-21Bis with tons of real info to check. If somebody thinks something is wrong they should provide some data about that compared to something, in this case real manuals available.

Anyway i have enough. There are always the same comments from the same people.

Bye.

double post, sorry

Guys here's a simple visual test for you to do:

1. Fly the MiG-21 slow straight and level at 20 deg AoA according to instruments

2. Pause the game

3. Note the AoA reading on the info bar.

4. Switch to external view and try to eyeball the attitude of the aircraft

5: Answer the below questions:

- Does it look like the aircraft is flying at the AoA indicated by theinstruments?

- Does it look like the aircraft is flying at the AoA indicated by the infobar?

After completing the test ask yourself the following:

- How come the ingame MiG-15 is capable of flying at a higher AoA as indicated by the info bar than the ingame MiG-21?

- Does the real MiG-21 or MiG-15's wings diverge by more than 5-10 deg in attitude in comparison to the nose? If not the info bar AoA reading will roughly equal wing chord AoA.

The UUA-1 is not supposed to always agree with the geometrical (pitch minus flight path angle) AOA. Flow direction around structures of the airplane at DUA-3 sensor or wing chord maybe different than "big picture" geometrical AOA.

I direct you to page 29 of 30 this document which describes an installation of sensor in similar position to DUA-3 on MiG-21. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930085167.pdf Note that for M0.6 when real alpha is 10° sensor may be seeing 14° locally. At M0.92 when real alpha is 0 sensor reports -2. This is a generic example but can show normal position error of AOA sensor based on installation location, alpha (and beta) magnitude, and Mach.

Example performance table says descent (landing approach) to 2000m should be 153 m/s speed, -40m/s descent rate, -7 AGD pitch. This is flight path angle -15(.2) and pitch -7 giving calculated AOA 6°. Table also says to expect 5-7° by UUA-1. This is basically exact agreement, but it is at low Mach and low total AOA.

And lastly who knows what Mikoyan did with design. DUA-3 to UUA-1 is electrical and manual warns that needle position will be less at 22V battery compared to 28V normal flight. Does UUA reading have deliberate calibration built in or is it "dumb" repeating what DUA-3 sensor reports?

And what is the right attitude?

 

Complaining without data reference? This is wrong because i think is wrong?

 

There are tables available for the Mig-21Bis with tons of real info to check. If somebody thinks something is wrong they should provide some data about that compared to something, in this case real manuals available.

 

Anyway i have enough. There are always the same comments from the same people.

 

Bye.

What? Not patronizing the posters, for one. Do you really think those of us who "always complain" are basing their arguments on faith or something?

Look, Frederf pointed out the problem in your argument. The instruments we have in cockpits are not the only reference because, as Frederf pointed out, have an error factor simulated or cannot even show information due its design. But you should have known that as you are the only one who uses real manuals.

Problem of instrument envelope from the manual:

As is seen on the picture... Mig21 is producing lift past what AoA in cockpit can display.

 

And lastly who knows what Mikoyan did with design. DUA-3 to UUA-1 is electrical and manual warns that needle position will be less at 22V battery compared to 28V normal flight. Does UUA reading have deliberate calibration built in or is it "dumb" repeating what DUA-3 sensor reports?

In a module that fails to properly simulate basic stuff such as afterburner engagement sequence and castering nosewheel, do you seriously think they simulated AoA probe errors due to low battery voltage??

:doh:

I suggested no such thing. You can't even attempt UUA readings on battery voltage it requires AC generator from running engine in DCS (in real airplane it is DC powered). What I am suggesting is that assuming that DCS module UUA is responding like real life UUA is unfounded and all comparison based on DCS UUA reading is similarly suspect. Comparisons with cockpit gauge readings can only be made if accuracy of gauges is verified.

Problem goes much deeper: Consider gauge AOA and physical AOA in the following way. Examine maximum endurance condition which is L/Dmax practically by definition (lift constant, minimum power, minimum fuel consumption). We expect this in range 5-7° for a design like MiG-21.

Fly 480 km/h IAS and then look at your "F2" alpha 2.5-2.6°, not even close to believable. Wingman flying in formation at this speed ~6.0°, much more sensible. But look at your UUA at 480 IAS, about 6.3° indicated. That should be about your airplane's physical orientation relative to the horizon. It's crazy town! Airplane is acting like UUA reading but model orientation is much too flat.

Unless we are to believe that at very low Mach the local flow around the sensor and wing is nearly 4 degrees higher than true alpha.

That's all great, however being a delta the MiG21 should still be able to hold a higher AoA in terms of true aircraft attitude than the MiG-15, yet ingame the opposite is true as evidenced by the info bar.

I suggested no such thing. You can't even attempt UUA readings on battery voltage it requires AC generator from running engine in DCS (in real airplane it is DC powered). What I am suggesting is that assuming that DCS module UUA is responding like real life UUA is unfounded and all comparison based on DCS UUA reading is similarly suspect. Comparisons with cockpit gauge readings can only be made if accuracy of gauges is verified.

 

Problem goes much deeper: Consider gauge AOA and physical AOA in the following way. Examine maximum endurance condition which is L/Dmax practically by definition (lift constant, minimum power, minimum fuel consumption). We expect this in range 5-7° for a design like MiG-21.

 

Fly 480 km/h IAS and then look at your "F2" alpha 2.5-2.6°, not even close to believable. Wingman flying in formation at this speed ~6.0°, much more sensible. But look at your UUA at 480 IAS, about 6.3° indicated. That should be about your airplane's physical orientation relative to the horizon. It's crazy town! Airplane is acting like UUA reading but model orientation is much too flat.

 

Unless we are to believe that at very low Mach the local flow around the sensor and wing is nearly 4 degrees higher than true alpha.

Thanks for explaining your point, it's clear now ;)

I think the FM in this model is just broken.

After all, this is the oldest 3rd party module in DCS, and it was developed in a fragmented way (Beczl, then LN). I wouldn't be surprised if the "EFM" of this MiG-21 would be more akin to an embellished SFM, in fact it does feel very scripted during stalls etc, like flipping a switch.

I would love for anyone to take this module up, and bring it up to DCS standards. I also feel ED should guarantee more quality control, because they are the ones putting the DCS label on it at the end of the day, and we (used?) to trust that label.

Here we are with an unfinished product, 4 years into "early access" and there's not even the shadow of a roadmap to fix the issues. No word form the devs, nothing.

Even a "Sorry, we fu**ed up and we don't know how to fix it" would be far more acceptable than this rubber wall. This community has a lot of passion and heated conversations, but it's also very understanding and forgiving when devs are transparent.

ED should buy the rights to this project from LN, and finish it.

Few quick answers:

- UUA shows local angle of attack (note local)

- F2 view in human module will show you relative pitch angle although it says AoA

- local angle of attack is greater than relative pitch angle about 2 times

- exact local AoA calculation is implemented in the code

The only correct information about local AoA is what UUA shows.

Thanks Dolphin.

What some were saying, use the instrument, not the F2 bar.

Thx Dolphin.

A small story for you guys, some years ago I was engaged in a discussion regarding the MiG's speed limit. I was sure as hell that I'm correct because Tacview said so. Vyrtuoz confirmed to me that his software had an error reading the flight instruments that time. On that day I learned to question at first the tools with which we work when accusing developers doing fundamental errors in FM programming.

A further lesson I learned from Tharos and Esac was to always compare modules to it's RL charts and manuals and not other modules since this seem to be a new kind of sport recently.

Feel free to laugh over my naivety, ignore everything I said or take a message home but I would hope that at least some of you guys change your attitude a bit. Otherwise I would have only one wish. Keep this stuff out of the other 3rd party dev forums which I use frequently, it really ruins my day and is far from constructive. Maybe this gives you a hint why devs aren't talking to the community. And regarding dev time.... Maybe some of you are simply not long enough here to know how long it took ED for finishing Nevada

Here is a graph of calculated CLy values for 28 and 33 degrees UUA-1 indicated AOA. Background graph is from MiG-21bis handbook.

Methodology is as follows:

Perform pitch up banked (constant altitude) turn to achieve desired indicated AOA by UUA gauge at TAS corresponding to fraction of Mach to record corresponding load factor. Assumption is lift is equal to aircraft mass times load factor times gravity. Coefficient of lift is calculated in the following way:

CL = LF*m*g / (rho * v^2 *0.5 * A)

LF is load factor measured in units "G" F2 bar

m is mass 7503kg held constant by infinite fuel cheat

g is 9.81m/s^2

rho assumed standard atmosphere 1.111kg/m^3 at 1000m and 0.736 kg/m^3 at 5000m (M0.4-M0.7 and M0.8-M0.9 respectively)

v is true speed in m/s corresponding Mach fraction shown on F2 bar

A is 23 square meters reference wing area MiG-21

Atmosphere is DCS standard 15C no winds.

Result is UUA28° CL decreased smoothly from value 1.2 dimensionless ratio at M0.4 to slightly less than 1.0 at M0.9. UUA33° was approximately 10-20% higher in all cases similarly decreasing with increasing Mach. Data is overlaid on existing performance chart showing CL with 28, 33, and maximum lines.

Further work could be done to calculate expected load factor to be achieved based on real chart at UUA 28, 33 and CLmax and compare to indicated UUA reading when those load factors are achieved.

E.g. M0,5 UUA 28° expect CL 0,7. At 1,100m air density this is L = 0.7*0.5*1.111*156^2 *23 = 217650N lift. Given 73604 weight of airplane at LF 1 then LF should be the ratio 2.96 "G".

If airplane is flown at this speed and altitude and pulled to this "G" then UUA indication is: 17° which is much less than 28° expected.

Victory :v: but…

What are local/relative pitch angles ? :dontgetit:

I do not understand the question.

Thank you for clarification Frederf.

I'll take a look at the code.

I do not understand the question.

Mine ? it about this :

Few quick answers:

 

- UUA shows local angle of attack (note local)

- F2 view in human module will show you relative pitch angle although it says AoA

…

F2 AOA is "global AOA" which is motion and orientation of airplane with respect to the undisturbed air mass. This includes wind so it is really AOA not just pitch relative to TVV. Parked with a tailwind you'll see it show 180 degrees.

But air flow around airplane structures is disturbed so every location on the airplane can have a different angle (and speed) of air flow.

I just had to look at your diagram for less than half of a second to understand everything :smartass:

Thank you for all your detailed explanations :thumbup:

F2 AOA is "global AOA" which is motion and orientation of airplane with respect to the undisturbed air mass. This includes wind so it is really AOA not just pitch relative to TVV. Parked with a tailwind you'll see it show 180 degrees.

 

But air flow around airplane structures is disturbed so every location on the airplane can have a different angle (and speed) of air flow.

Exactly, and here it makes no sense that a delta like the MiG21 stalls before a MiG15.

Any news on this issue?

Exactly, and here it makes no sense that a delta like the MiG21 stalls before a MiG15.

Might be. "Stall" means the maximum lift point, the peak of the curve. MiG-21's maximum lift point might be less body angle than MIG-15. The benefit of delta wing is that the curve post-stall (after the peak) is not so dramatic. If MiG-21 has maximum lift at 15-17° body angle then it still has significant lift at 20-25° body angle in the post-stall regime where other airplanes have practically no lift this far past the peak value.

I decided to scale and align the 3 Lift vs Mach charts in this thread to each other to help me visualize the difference in data.

Interesting, only lines for UUA readings match between the 3 data sets.

That's an interesting comparison. I'm not surprised that the C-Ly max values vary so much. It's really hard to measure the exact maximum point and since the C-Ly can only really be achieved in a very transient manner or a wind tunnel.

The one that has lines for SUA-1 and UUA-1 interests me. What is the SUA-1 instrument?