adriannIs it possible that gentlemen exhausted their battles ?
Emile, probably nothing much….a/c would be somewhat trickier on landing due to shorter distance between main-wheels…more concentrated weight on fuselage would be more stressful, cross-section area distribution could be more adverse, but not necessarily…
adriannHere is nice, real life example of 360� “9G” turn.
http://www.youtube.com/watch?v=Wvjf6SA87BA
It starts from 4:04.
Pilot is entering the turn (not so hard) at about 0,6M. He is maintaining the G force between 8,3 and 8,8 with slow speed drop of about 0,1M at the and of the turn which lasts approximately 14,7 sec.
Of course there is relatively small modulation/drop in speed but for most of the time pilot is trying to maintain almost constant G force.
The same thing can be said for any other AF who participate in airshow, but without real confirmation this is only speculation.
Yeah, I watched this video 22 years ago, I think it was said that particular plane was for Turkish AF, I remember 120 kt min speed, warnings during slow speed rolls (most interesting part for me) and ~ 9g? at 375-390 kt, 26-21 deg per sec, inst./sustained TR and you can deduce what is happening in turn. Of course, you can use official graphs to check what is possible.
Do not let me attach these graphs about your planes.
Yes, as you said: The same thing can be said for any other AF who participate in airshow, but without real confirmation this is only speculation..
I stopped believing in fairy-tales about honesty in world. Of course that these corporations/manufacturers will do everything to sell their planes, least thing is to up-rate thrust. They will kill anybody, put puppet government in customer countries, provoke wars..do anything needed. Sales are always accompanied with corruption, bribery.. I remember couple years ago when Finland and Slovenia were caught doing this kind of “job”, two I’d say most corruption-free countries.
adriannWe are talking about 360° turn rate. You need (pretty much) to sustain your turn rate in order to make the best time for 360° turn. Max ITR is done at lowest speed you can pull your max G. If you do max ITR in the beginning of the turn you will cause speed to bleed off below the optimum value, resulting in reduced sustain rate. Generally you need to sustain speed that is slightly below the speed needed for max sustained G load at given altitude in order to extract max sustain turn rate.
Bottom line, Su-27 needs approximately 13 sec for 360° turn. If we compare 360° turn rate for different fighters, °/s is what counts and we still need to see similar result for F-15.
If we insist on factual data you will need to give some link for that claim.
If I should perform min time 360° turn in Su-SK (w=22.8 tonnes, ω inst = 28 º/s, ω sustain = 19.5 º/s SL), I would start turn at speed somewhat between corner and best sustained TR speed and I would maintain 24º alpha, probably averaging ω ~ 24 º/s, far quicker than max sust ω.
There’s difference between the same engines in operational squadrons. Production tolerances are tighter, incidentally, in some and wider in other engines. Law of probability. You can just take these ‘better’ engines/aircraft for airshow or you can additionally trim the same engine to higher RPM to easily achieve higher thrust, for the expense of service life.
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adriannWrong. Su-27SK manual says G limit can be founded by mass*PuMAX = constant = 171000 kg, with PuMAX not exceeding 9Gs. While it DOES correspond to 8Gs for 21400kg -which manual consistantly assumes normal payload-, it is *NOT* the G limit of the airframe. Its the G limit with 5100 kg fuel on board.
[ATTACH=CONFIG]216030[/ATTACH]PW220 engined weigh 13600 kg empty. Graph is for 37000 pounds so that F-15 only carries 3180 kg fuel. To be compared with it, Su-27 only needs to weigh 19480kg. If you are comparing with NTOW, F-15C should weigh 44000 pounds.
As for your logic for declaring the curves as fiction, its laughable. You read a 8G value from the SK manual and you take it as fact -which is not, as explained in the very same page-, but fail to mention the graphs a few pages ahead where clearly shows Su-27 can pull and exceed 9Gs with 4700 kg fuel and 4 missile payload, where its suggested limit is 5.5Gs.
[ATTACH=CONFIG]216029[/ATTACH]Overall CL can be extrapolated from G versus speed graph if we know aircraft weight and wing area.
Lift force = G*aircraft weight = CL * (density of air)/2 * (airspeed)^2 * wing area.That would be a idiotic form of engineering. Still, irrelevent if we are looking for overall CL of aircraft.
I am not fan of Su-27. Maybe I am a little biased towards F-16, but even that does not come before technical specifications.
Agreed about that. We have enough solid numbers videos etc etc to compare legacy types of Su-27, F-15, MiG-29 or F-16. But not for the types you mentioned.
However if you like to question the validity of the numbers -which are generally considered valid-, its up to you to disprove them. You will possibly say its also up to me to prove them, so I will try my best:
you are looking at page 33 which only shows G limits. Take a look at page 36 also, it clearly shows 1400km/h speed limit:
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The TsAGI data assumes a) 50% fuel load which is 4700 kgs b) 21000kg take off weight. This is inline with 16300kg empty weight + 4700kg fuel. With this weight it should have 8.15G limit according to SK manual. They may have rounded it up to 8.5, IDK how exactly formula should be used (171000/21400 gives less than 8Gs anyway)http://www.youtube.com/watch?v=4B00eSuLq0Q at the turn starting 4:25, Su-27 completes full 360 turn in 12,7 seconds, averaging at 28.3 deg/s turn rate. That turn made right before the landing, so lets assume 500kg (bingo) fuel present.
TsAGI data estimates 27,5 deg/s if I were to take highest G point (exceeding 9G limit) or 26.6 deg/s if I take 9G limit. Its pretty consistent, as this was not an exaclty 0 SEP turn and possibly aircraft slowed down a little.http://www.youtube.com/watch?v=n_4WBQDtQ70 at the turn starting at 4:27, Su-27S completes a sustained turn in 14.8 seconds averaging at 24.3 deg/s turn rate. Turn is completed at 4:41 and plane continues manuevers mostly on AB and camera cuts at at 6.28. Lets assume 500kg fuel at landing and 195,7 kg/kN/h SFC (reasonable, as its subsonic and sea level flight). By the time turn is initiated aircraft was carryying roughly 1930 kg fuel, and was weighing 18230 kg. For that weight TsAGI data estimates 25,34 deg/s if 9G limit is exceeded, 24,7 if not.
On both occasions, the difference between observed and theoratical data is 2-3%, IMHO validating it.
Also, If you are claiming Su-27 numbers are not reliable and F-15C is better in reality, its up to you to show F-15 sustaining a 360 turn quicker than those.
Guys we are off from subject ! Do not waste time and these characters….
First, let me wish you all Happy Worker’s Day – May 1st (no matter in how anti-peoples countries we are living) !! In Croatia it was beautiful Holiday until the country was sold.
G limit of Su-Sk is 9g at 19 tonnes weight (w empty is 17.2), 8g at 21.4. At w=22.8 limit is 7.5 for certified service life, a/c will not crack at 9g but life would be exponentially shorter, as in any other a/c..you can not play with certified limit ! How it is cleared to 8.5g at combat weight? I assume combat w is 1.33 X w empty. I do not understand what is not clear to you.
I compared it with F-15C at 39.ooo lb weight, official w with half fuel and 4 AIM-7.
You all guys should not talk about a/c without exact empty weight !
These flight manuals are not written for fun !!
I do not what is not clear in second your (russian official) graph. It says that limit is 8g with 4AAMs and half of NORMAL fuel load (w=21.4), that weight is bellow usual standard combat weight for fighter comparison.
Next: you extrapolated CL from sustained g curves to get CLmax for building instantaneous g curve ??? For both Su and F-15. If you do not have exact F-15 lift curve vs Mach you could use this official graph. Official does not necessarily mean true because one can find that max usable lift from this graph does not take into account huge buffet limitation at M> 0.9 !!!!
Max lift, F-18’s also for example, is achieved with wings stalled. You should read engineering magazines.
Your third graph shows IAS limit 1400 km/h, right. But I still say graph is childish because it show that although IAS limit is 1400, Su have enough thrust to fly 1600 km/h level !! That class of a/c can not achieve more than M 1.1 to 1.15 in level flight – because of thrust – drag relation.
I’m not showing F-15 is better. I’m not fan of countries that are stealing third world countries natural resources. I just want us to be objective and rely on official data.
In youtube videos turns are not sustained or instantaneous, but combined ! Engines are usually tweaked for more thrust.
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adriannAndraxxus, you are very good but point is not to wast our time… incidentally I’m flight operations engineer and I take my job home…
You said: “My first graph is from F-15C flight manual. Second being TsAGI data, I can say they are pretty much useful. Its just you who don’t see it.”
Problem is that “famous” TsAGI graph is pure fiction probably made by some enthusiast. I have already said that aviation fans should ask for official data ONLY. I’m not surprised that I’m the only one, as you had said, who don’t see usefulness of that graph.
First look at the graph reveals that a/c has 8.5 g limit. Su manual says that a/c has limit 8 g at a weight of 21.400 kg !!!
To be compared to F-15C, Su-SK needs weight of about 22.850 kg, and that gives 7.5 g limit !!! That’s just the beginning.
Next, it seems that Su can fly level at altitude of 200m at a speed of about 1600+ km/h. Curves are fiction. It is certainly not official Russian graph. Sorry that nobody has complained for all that. You had better not merge these graphs, in excel.
Su has higher bypass ratio only than PW229 ! Booklet explains why F-15/220 is faster.
F-15’s wing profile is modified and cambered 64A…and that’s just the profile, nobody can extrapolate whole a/c lift from that, especially if in max inst.turns wings are stalled and fuselage gives CLmax !
As I have said you guys aviation people, you should ask from your pilots, manufacturers, military…real facts if they want you to be fans of their planes. I wonder if, for example..there is any useful data on Typhoon or Rafale, Gripen..performances in media. And yet everybody know they are the best planes ever ! And Russia gave everything about their best planes ! Who is cheating whom !
adriannI do not want to argue, it is often useless…I remember you haavarla as a fair player, do not spoil that…
F-18 has best L/D of modern US fighters…it’s L/D can be challenged only with older fighters with slower supersonic speed capability… pity..among thousands of pages about fighters, you can not find that item, nor even for F-15 !
I can only recommend you guys, to insist on official fact and figures regarding these machines. If manufacturer declines to give real and important figures, do not play as they want, spreading their propaganda without useful facts, graphs, figures…
adriannIn 1940 they had an air to air with a Spitfire and Camel. The Camel won out. Later came the real bout between Spitfire and Fiat C.R.42, and the 42 didn’t do so well.
Very often, “duels” are orchestrated, depending on AirForce/Manufacturer/Gov will…
Speed was most important item for subsonic fighters…
adriannFor me, problem is that there are in ‘ether’ few real facts, to much fairy-tales…
For example, I didn’t see F-15’s stall speed ie lift, easily..I had to pay a lot for that info ..CL curve…and yet everybody is talking about F-15’s lift or instantaneous turns or who is better …
Also I think Hornet has the best L/D of modern US fighters..just thrust deficient, but it can be tolerated. The F-16’s pilots say that 15 is better slow because of lack of alpha limits and possible rudder rolls…at the edge of departure…
Su-27SK is heavy .. I do not know whether its exact basic weight is published in forums and internet…and how can we talk about performances without that info .. and a/c is 25 years old, people are wasting energy debating…
adriannMost graphs are fiction…look at the max speed SL !
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or how F-15 is better in sustained turns between 700 and 1000 km/h, 200 m altitude ?? (Russian graph, unofficial)
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Good lift has nothing to do with good L/D, M2000 or Gripen has good lift but less spectacular L/D.
I think that F-15 is optimized for low speeds also, but it is older. If lateral stability is not up to current standard, no FBW can help !
Lower BP ratio is better at hi-speeds only w/o afterburner !
I’m not saying who is better, I’m just saying that a/c are decades in service and shame is that no useful data are on forums !!
adriannAll these years in service and still unknown to public…both planes..
Problem with these last 3 graphs is that they are fiction… F-15C graph is clean…
You said that Su is better at low altitudes, what makes difference at hi altitudes ? (bypass, induced drag, lift…?)
Very few cited data is fact ….
adriannI didn’t mean to talk about good and bad guys, now all guys are bad …about hypothetical situations…
I wanted to talk about lift/drag ratio, a/c weights..stall speeds, turn rates, SEP, engine basics and limits…both planes are not new and I didn’t see much of these official numbers on a hundreds of pages in forums, how so ?
adriannComments on “F-15 vs Su-27” ?
http://www.scribd.com/doc/137334946/F-15-vs-Su-27 ….an article from Serbian Aeromagazin
adriannadriannInteresting but useless..
Wasting people’s money and patience..guarding regime and fighting unorganized crime..
adriannWhy AF should consider purchasing new fighters?
Which country to defend ?
We can see a bunch of special units performing exercises in front of the children in central Serbia in time when south territory is about to be taken away without fight.
Period
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