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MiG-29's BFM characteristics / doubts


Top Jockey

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Thank you for your reply. I would say the data cannot be used for comparison - not illegitimate per say - just that there are obvious instances of incompatible results. for example the STR the same but turn radius smaller on the one with higher airspeed. Too many variables are unknown about the tests and the conditions which means you can't make a meaningful comparison.

 

"pitch rate" needs definition in this context, do you mean the rate that you can increase AoA? which again would be very hard to test in equal measure, which explains the subjective conclusion.

 

In summary, you wanted a response - I'd say the data is not good enough for comparing in a legitimate way.

 

Thank you.

 

There are perceptible divergences in some values yes.

And, indeed if the ITR and STR values might be more or less consensual (as they tend to appear in EM diagrams), on the other hand the Turn Radius ones are not so easy to come by - so I posted what I've found.

 

I do have a doubt however on your references between STR and turn radius:

- although maximum STR is supposedly similar for both ( 22 deg/sec );

- I believe minimum Turn Radius is not achieved at maximum STR, neither at corner speed - but at speeds lower than these circumstances;

- they are different airframes; also one is FBW, the other is not...

 

But there's a lot I don't know, so I come here seeking for data / info regarding those 2 aicraft's turn performance.

 

edit:

 

Pitch Rate would be (for me) roughly the ability of how quickly one aircraft can point its nose into a different direction in order to get a snapshot... so not being myself an expert on this, I imagine it can also be measured in deg / sec ?

 

And in that regard, without using "Direct Control", the Su-27 seems considerably sluggish when comparing with the MiG-29.


Edited by Top Jockey

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..,

 

The diagram at post #139 from Hummingbird...where is the corner speed on that diagram ?)

Like a lot of other numbers involved with this topic, it won’t be a single number but, rather, a range that depends on altitude. On the chart, if you read down from the intersection of the max-AoA and max-G lines for 200m altitude you’ll have the speed for that altitude.

 

I really would like to see a similar diagram for the MiG-29.

So would I. I’ve been looking through various Russian sources but haven’t found anything yet.

 

 

...

- I believe minimum Turn Radius is not achieved at maximum STR, neither at corner speed - but at speeds lower than these...

Well...the slower you go the tighter you can turn. The minimum would be the point at which you stall and fall out of the sky. You have the smallest turn radius. You just can’t scribe it quickly.

 

Pitch Rate would be (for me) roughly the ability of how quickly one aircraft can point its nose into a different direction in order to get a snapshot...

Seems a reasonable number to look at, since pitch and AoA are two different things. And deg/sec would work for that.

 

And in that regard, without using "Direct Control", the Su-27 seems considerably sluggish when comparing with the MiG-29.

But, in the sim‘s Su-27 cockpit, you should be using the “Y” key (or whatever the key command is) to simulate pulling through the stick limiters. That is very different from taking direct control (“S” key).

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Like a lot of other numbers involved with this topic, it won’t be a single number but, rather, a range that depends on altitude. On the chart, if you read down from the intersection of the max-AoA and max-G lines for 200m altitude you’ll have the speed for that altitude.

 

Thank you.

 

Well...the slower you go the tighter you can turn. The minimum would be the point at which you stall and fall out of the sky. You have the smallest turn radius. You just can’t scribe it quickly.

 

In that case I don't know why / how do they state a 450 kph speed in the link I've posted... as I'm sure the Fulcrum can maintain a slow turn without stalling and fall at speeds lower than that...

 

But, in the sim‘s Su-27 cockpit, you should be using the “Y” key (or whatever the key command is) to simulate pulling through the stick limiters. That is very different from taking direct control (“S” key).

 

Absolutely - the Deflection Limiter Override (also mapped in my stick), and that's how I've always been testing both the MiG-29 and the Su-27 behavior.

 

In my not very scientific tests; 300 kts speed, 1000 ft above sea level, roughly level flight (near 0º pitch), 2 AAM, and very low internal fuel, I give a sharp pull on the stick - to nose up attitude, and pause the sim after 1 second passed:

 

MiG-29A

- using Deflection Limiter Override : attains 50º - 55º nose up

 

Su-27

- using Deflection Limiter Override : attains 20º + nose up

- using "Direct Control" (ASC) : attains 70º + nose up


Edited by Top Jockey

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...In that case I don't know why / how do they state a 450 kph speed in the link I've posted... as I'm sure the Fulcrum can maintain a slow turn without stalling and fall at speeds lower than that...

Not really sure. The Flanker # is probably close to the minimum turning speed, though minimum straight line speed is 200 km/hr. You might want to jump into their respective cockpits and see what those numbers represent.

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...

 

In my not very scientific tests; 300 kts speed, 1000 ft above sea level, roughly level flight (near 0º pitch), 2 AAM, and very low internal fuel, I give a sharp pull on the stick - to nose up attitude, and pause the sim after 1 second passed:

 

MiG-29A

- using Deflection Limiter Override : attains 50º - 55º nose up

 

Su-27

- using Deflection Limiter Override : attains 20º + nose up

- using "Direct Control" (ASC) : attains 70º + nose up

Just for fun, I ran your experiment with slightly different parameters. MiG-29A with max weight and Su-27 stripped down so that their respective gross weights were as close as possible, though still 2000 kG apart with the MiG being lighter. I ran until their swing rates began to slow, then averaged the time. Starting airspeed 600 km/h.

 

MiG-29A: 61°/sec (it only took 1 second)

Su-27: 22°/sec (took 3 seconds)

 

I guess you can see where the MiG-29's famed nose pointing ability comes from.

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Review of the real pilot of the MiG-29 flight model in the DCS:cry:

 

Quick translation: there are many discrepancies in the DCS flight model with the real MiG29. The MiG-29 is one of the easiest aircraft to fly and land. Landing on the MiG29 is easier than on a modern Airbus

 

Опять все заново который раз))))) . Если честно то я использую только одну функцию модуля любимого самолета - красивые обои МиГ-29((((. И каждый раз пытаясь на нем полетать ощущаю разочарование и опять откладываю в долгий ящик. Потому что не может быть так , что на самолёте на котором ты отлетал кучу лет было летать тяжелее чем на куче других самолетов на которых ты не летал и даже не знал заданных параметров захода на посадку. Тем не менее есть элементарные методики их определения и после пары минут любой самолет элементарно сажается . Тут же зная все до мелочей происходит постоянная борьба с самолетом особенно на этапах захода и посадки . Конечно , его можно посадить и нормально и почти отлично и это иногда получается, но это не тот самолет и он заставляет напрячься чтобы более менее хорошо это сделать. Если бы так было в жизни , я думаю , не досчитался бы многих своих товарищей и не уверен что выжил бы сам :) Еще раз поторюсь, реальный МиГ можно сажать ковыряясь одним пальцем в носу . Вся молодежь после училища вылетала на нем самостоятельно без всяких проблем. На моей памяти только у одного летехи были серьезные трудности из за которых его и списали. Даже Airbus , на котором я летаю сейчас с его fly by wire несколько сложнее на заходе и посадке МиГа .

В общем то модуль для упрощенного варианта не плохой, но посадочные режимы конечно не соответствуют прототипу. Видать поведение математической модели отличается от физической при точном копировании графиков из учебников . Что конкретно отличается тут уже много раз обсудили .

Что касается видео , то тут ничего удивительного , за мгновение до касания , когда самолет уже почти не летит , иногда хочется его еще мягче досадить поддернув РУС, но тут скорость уже настолько мала, что как правило это уже ни к чему не приводит, кроме морального удовлетворения, а самолет сам тем временем плавно касается обжимая амортизаторы . А чтобы РУС не упирался в живот надо от него избавляться :) ( от живота) .

По сравнению с Л-39 наш 29-й не имеет тенденцию к взмыванию , в то же время приличный запас тяги и бешенная приёмистость сильно облегчают заход и посадку .


Edited by Flаnker
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Just for fun, I ran your experiment with slightly different parameters. MiG-29A with max weight and Su-27 stripped down so that their respective gross weights were as close as possible, though still 2000 kG apart with the MiG being lighter. I ran until their swing rates began to slow, then averaged the time. Starting airspeed 600 km/h.

 

MiG-29A: 61°/sec (it only took 1 second)

Su-27: 22°/sec (took 3 seconds)

 

I guess you can see where the MiG-29's famed nose pointing ability comes from.

 

Thank you for your time experimenting this stuff.

I've re-learned to appreciate the MiG-29 again, and knowing an aircraft's "weaknesses" is part of knowing it better.

(In its case, the rapid speed / energy bleed while hard turning copmpared to others, as amongst several reasons it isn't FBW controlled, does need more AoA for the same Gs, etc.)

 

Eventually managed to get better with it while ACM against AI opponents... however the Su-27's ability to not bleed speed so quickly (much like an F-16) when chasing the AI's JF-17 in sustained turns, did cause a very good impression on me.

 

On this kind of "experimenting" , tipically I test both aircraft with the respective fuel quantity for roughly 3 - 4mins. full AB... but I guess the way you've done (full internal fuel) highlights even more the MiG-29's pitch rate (nose pointing ability).

 

Also, if one pays the due attention, the MiG-29's supposed small Turn Radius does allow to get on the opponents 6 o-clock in somewhat better position (not so large turning room) than other fighters... provided one doesn't lose too much speed to get there either.

 

Review of the real pilot of the MiG-29 flight model in the DCS:cry:

 

...

 

Quick translation: there are many discrepancies in the DCS flight model with the real MiG29. The MiG-29 is one of the easiest aircraft to fly and land. Landing on the MiG29 is easier than on a modern Airbus

 

Yes, it was posted already at post #158, but would also be interesting to know the pilot's opinion on turn / pitch performances, speed bleed rates while turning and that stuff.

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Go figure. Anyone thinking the FC3 "PFM" flight models are anywhere close to the real thing are kidding themselves. They are good for producing certain numbers like turn rate, radius and thrust to weight ratio but that's mostly it.

 

They have shown that the FC3 PFMs are just as accurate and well done as the PFMs of full fidelity planes. This was all finished with the MiG-29 being last with its PFM coming out in 2018

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They have shown that the FC3 PFMs are just as accurate and well done as the PFMs of full fidelity planes. This was all finished with the MiG-29 being last with its PFM coming out in 2018

 

That's not a complement to FF modules then:)

Anyway, now, when ED is considering making FF 29 smth might change for the best. If it becomes full fidelity of course

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That's not a complement to FF modules then:)

Anyway, now, when ED is considering making FF 29 smth might change for the best. If it becomes full fidelity of course

 

What ? MiG-29 SMT ?

I fully agree - keep them comming ! :D

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Go figure. Anyone thinking the FC3 "PFM" flight models are anywhere close to the real thing are kidding themselves. They are good for producing certain numbers like turn rate, radius and thrust to weight ratio but that's mostly it.

 

https://www.digitalcombatsimulator.com/en/support/faq/505/

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The realism of a PFM is NOT depend from the system modeling

My english level is adequate for this forum, but my German is much better

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Don't know if I am late to the party, but regarding the turn rates and radii: I did some extensive research on the topic and it turns out that in a coordinated turn (no side slips), that has no altitude changes and with constant speed the aircraft will have smallest turn radius (TR) and highest rate of turn (RT) at the lowest speed possible. This is determined by the maximum coefficient of lift (CoL) the lift surfaces can produce, which in turn is directly connected to the maximum angle of attack (AoA) - basically just before stalling.

 

The slower you fly the tighter the turn and there fore the higher the turn rate.


Edited by Cmptohocah

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Don't know if I am late to the party, but regarding the turn rates and radii: I did some extensive research on the topic and it turns out that in a coordinated turn (no side slips), that has no altitude changes and with constant speed the aircraft will have smallest turn radius (TR) and highest rate of turn (RT) at the lowest speed possible. This is determined by the maximum coefficient of lift (CoL) the lift surfaces can produce, which in turn is directly connected to the maximum angle of attack (AoA) - basically just before stalling.

 

The slower you fly the tighter the turn and there fore the higher the turn rate.

 

Thank you for your time Cmptohocah.

 

I'm trying to know the real life values on the data below; I've been in the russian DCS forum, but its not easy.

Can you confirm if the data below sounds more or less plausible ?

 

MiG-29A

maximum ITR: 28 deg/sec

maximum STR: 22 deg/sec

minimum Turn radius: 300 meters at 450 km/h

 

Su-27

maximum ITR: 30+ deg/sec

maximum STR: 22 deg/sec

minimum Turn radius: 355 meters at 350 km/h

Pitch rate: lower than the MiG-29's (if not using Direct Control)

 

 

From:

 

post #1

https://www.team-bhp.com/forum/comme...-rests-us.html

 

slide #34

https://www.slideshare.net/mishanbgd...-su27-19577861

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Thank you for your time Cmptohocah.

 

I'm trying to know the real life values on the data below; I've been in the russian DCS forum, but its not easy.

Can you confirm if the data below sounds more or less plausible ?

 

MiG-29A

maximum ITR: 28 deg/sec

maximum STR: 22 deg/sec

minimum Turn radius: 300 meters at 450 km/h

 

...

 

I am on holidays at the moment, so I don't have access to DCS, but what I can confirm regarding MiG-29S turn performance (from memory) is:

 

  • at 60 degrees of bank it pulls 2G and has almost identical measured turn rate as the theoretical value, so at least for this bank angle the performance is as expected - fight tests confirmed
  • at full after-burner (AB) and carrying 2xR-27, 4xR-73, central fuel tank and 100% fuel load, the maximum sustained turn rate happens somewhere between 500 and 450km/h and the pulled G's are somewhere around 6-7. There is some degree of variation due to difficulty of maintaining the constant AoA/Gs, but this might be also a limitation of my control hardware.
     
    Flight conditions: standard atmospheric pressure, standard DCS temperature, below 50m MSL altitude (IAS/TAS can be considered same) and clean configuration (no flaps).

Once I am back form holidays, I do some more flight testing and post detailed results regarding the Sustained Turn Rate.

 

When it comes to Instantaneous Turn Rate, I had big difficulties measuring it since the maximum AoA for the MiG-29S seems to be somewhere between 22 and 25 degrees, but I will give it another try.


Edited by Cmptohocah
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Review of the real pilot of the MiG-29 flight model in the DCS:cry:

 

Quick translation: there are many discrepancies in the DCS flight model with the real MiG29. The MiG-29 is one of the easiest aircraft to fly and land. Landing on the MiG29 is easier than on a modern Airbus

 

Thats not the whole truth. In a later post, he said that these discrepancies are a result of flight sim hardware not being able to replicate the feel real life Mig-29 flight controls, both in deflection and force.

FWIW I have no problems landing the Mig-29 owed to my stick extension and heavy spring set. But I see how people with lower grade hardware (presumably like the guy who wrote the post) have lots of difficulties, as the Mig-29 is insanely sensitive in pitch.


Edited by sLYFa

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Thats not the whole truth. In a later post, he said that these discrepancies are a result of flight sim hardware not being able to replicate the feel real life Mig-29 flight controls, both in deflection and force.

Thanx a lot for posting this essential piece of additional info. :)

No problem in landing the MiG-29 here either.

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Thanx a lot for posting this essential piece of additional info. :)

No problem in landing the MiG-29 here either.

 

Thats not the whole

 

 

The russian MiG29 thread is amongst other things about reproducible landings in accordance with the manual parameters, not about random touchdowns

This "guy" ( post ) is a pilot and instructor with 20 years of experience with the MiG29, currently on the job with an A320


Edited by HDpilot

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