adriannIt looks to me that pictures you attached are not from real a/c. Dial 1 should be combined IAS/TAS indicator (thin needle shows TAS, thick IAS), that’s why dial goes much beyond 1300 km/h. The 790 km/h IAS is Mach 0.65 close to the ground. It is the same as TAS at standard temperature.
To reliable work of the R-11 engine contributes, beside 2-shaft design, also number of compressor stages that is less than half the competition. Byproduct is higher fuel consumption.
Despite the resistance of the compressor to the extreme conditions of airflow at the inlet, if afterburner is engaged at almost zero speed (Syrian case, well below the conservative engine envelope) other undesirable phenomena are possible. Distortions of the inlet airflow causes disruption of relations of air and fuel in the AB chamber, which changes the speed of combustion. Pressure fluctuations coupled to acoustic velocity fluctuation (AB chamber is also exposed to sound fatigue, the noise is up to 180 decibels) associated with combustion instability (called rumbling), can cause extreme resonant structural vibrations of the engine with subsequent engine destruction and the loss of the aircraft.
adriannEvery a/c must have indicated, Soviets call it instrument speed, (some calibrated or even equivalent) airspeed indicator with readings from several tenths km/h or kt to above max allowed limit IAS (1100-1300 km/h in case od MiG-21)..There is transonic “gap” in accuracy only and no reading at very slow speeds, say below 50 km/h. Mentioned stall or slow speeds are always in IAS.
Older soviet a/c also has TAS reading used for example to hold climb speed…
Sens, you are great analyst, add a shade more theory and you’ll got it.
adriann“To the stall” is just phrase.. You have to decide if 21 is flown to the manual allowed and recommended limits then all that stories about good turns, you mentioned or slow speeds should be forgotten (F-13 than has min speed ~ 143 kt / 265 km/h or 8 g corner velocity about 405 kt / 750 km/h IAS).
Point is that 21 can be safely flown beyond manual limitations (to the wing rock or nose slice) where it shown better instantaneous turns than most fighters. Unfortunately, besides Aggressor pilots, only a few Egyptian, Syrian and couple of Soviet test pilots used to fly it to full extent.
adriannWe are at the beginning, again..
I’m saying that nobody flies 21 to the stall (maybe Romanians are ‘slowest’ with 250 km/h) and that limits it combat use. It has potential to fly trimmed and controlled at very hi-alpha and that also has limits (a/c and engine envelope which is another issue). Coupling with helmet cued AAMs makes 100 to 1 shoot ratio with even against fourth generation fighters w/o AIM-9X.
F-15’s configuration (medium sweep and low tail) becomes superstable at hi-alpha and cannot be trimmed above say 33 deg while 21’s strong wing vortical flow unloads its tail.
I’m waiting to hear what are that 21’s stall alpha, corner velocity, split-S altitude….in those AF which makes full use of ’21 ??
Loop entry speed is associated with a/c min speed and T/W. For MiG-29/F-15 it is about 300 km/h (160 kt) min.
adriannAdriann, sadly that the F-13 climb diagram is rude…
Sorry for the delay, I’m not on net regularly..
1. Original Soviet F-13 manual you are referring is in fact published 1963. I’m not taking it very seriously (as I’ve already said) and I use other Soviet F-13 manual where combat ceiling is for example 18200m where in former F-13 climbs at 40 m/s.
2. Figures you are referring are at unknown weight, but this Excess thrust graph could help. You can divide figure on Y-axis with speed (on X) and again with F-13’s weight to get SEP i.e. climb rate. Differences you are saying ..L/D, EP..are in fact included in SEP and you do not need to worry about them.
Maybe it is not worth time to calculate, but roughly F-13’s climb is shade behind F-4 while MiG-23 is in Super F-4 class or about 15% better than F-4.
3. F-5E vs MiG-21 is not subject but…shortly 21 is tonne heaver, 50% more powerful and 1 m shorter wingspan (you will not find correct F-5E’s wingspan or wing area/aspect ???). That speaks a lot. 21 has SEP to fly Mach 0.7 faster! VG inlet would not help F-5E since it can not reach speeds where they begin to move. But it has better lift (or similar to 21’s if flown in forbidden part of envelope) and wings that gives slightly better sustained turns subsonically. Also I think only one F-5E version has stall handling like 21, roll-off, others are more dangerous. 21 is better at high speeds and surprisingly at very low speeds – in stall turns and trimmed alpha.
4. Clues about Serbian manuals (I use Soviet Tech.m)..I think they were not satisfied with 21’s service life and wanted to prolong it.
adriannYour and other experienced pilot’s here opinion must be especially respected.
Other moments in Iraqi-Iranian air combat scenario also are important, such as IR missile homing head’s acquisition angle. Magic is generation ahead of earlier IR missiles with their fixed 2-3 degree a.angle.
During “Falkland” war Harriers reportedly did not use any VIFF, but relied only on AIM-9L off boresight acquisition angle to achieve, by British report, such a high shot-down ratio.
I’m interested, to what angles of attack Iraqis flies MiG-21?
adriannAbout the graphic. The MiG-21MF…
What is the reason why the speed limit of 702 kt was kept till 11500 m height, when the air pressure has dropped considerably at 5000 m already?!
The allowed limit for the F-4 is Mach 1,5 at 5000 m.
MiG’s 1300 km/h IAS limit apply to 11350 m (roughly 11500) where it corresponds to Mach 2.05 limit. After that altitude Mach limit applies.
At 5000 m, this IAS corresponds to Mach 1.37, where F-4 750 kt limit is equal to Mach 1.47. IAS limit is in fact q limit (dynamic pressure, air density times true speed divided by 2). All that a/c and engine limits are in that Serbian book.
adriannCould you please post a graph showing BIS climb rate from that Serbian book?
Well, according to Czechoslovak airforce directive 04/81, the total lifetime of the Mig-21MF was stated 2400hours/30years, but I cant help with the BIS figures.
There are rumors that in Serbian book Bis climb rate is presented in F-4 format for comparison to be possible, but I can put F-13 graph as interesting to match with 23’s. What can be deduced…max SL climbs are ?? And where are M2000, Super F-4, Gripen, F-18, F-14 ?
I thought that even if service life of Bis and MF could be simmilar, Bis could be designed to more, say 4g cycles for the same period…I do not know.
Limit g may not be as much important as a/c lift charcteristics, except for evading missiles whose proportional navigation guidance laws recognize huge difference between 8 and 9g.
Flap BLC temperature depends on particular engine, from which commpressor stage air is taken, in fact how much air pressure is in that stage. There is simple formula that states Temp is ambient Temp times {(1 + pressure ratio power 0.2857..[this is quotient of gas constants] minus 1) divided by comp.efficiency, say 0.83}. All in Kelvins. That means if PR is 3, exit temp is 142 deg C. If PR is 2, t = 90 deg C. If PR is 12 as in J79, t = 372 deg C. Of course, air is cooling as it expands out of tube nozzles or with friction at at the walls. Of course, engine rpm counts for PR.
adriannIt seems that MF and Bis can withstand equal structural strain…8.5g at 7.1 tonne weight and 1300km/h IAS. (MF is certified to 8.5g with less than 1200 liters fuel or 8g with less than 1600 l). Bis is 300-500 kg heavier empty, depending on equipment, yet it has more Titanium in structure and engine.
That means limit load with half fuel/2 AAMs – MF -8.5, Bis 8g. I do not know their service life with equal fatugue spectrum.
adriannWe can learn that Northrop data for wingspan is higher also ! Besides thrust..
It is really interesting to know that F-5E climbs at higher speed than most fighters (in spite of lower wing sweep than most, that means drag divergence Mach is more favorable ??)
adriannI do not know, but I can’t get more than 140 m/s at SL, 6000 kg weight..(F-5E)
Here’s one Russian graph.. any more serious ?
They were used as 21 simulators probably, because of their size and lift..
adriannplease explain where is this diagram showing 190m/s climb rate?
Sens, what diversity in a climb rate (105-230)!!
In fact, no variant has max initial climb rate less than 80% of Bis’s in second AB with half fuel (225m/s)!
Graphs in different form can help understanding initial climb. Here is one from that Serbian book..
Bdw, I saw Belyakov/Marmain book, it seems that Belyakov, (like my boss) is expert in some topics, say structures, but fl.mechanic could be something totally different. I read climb of 130 for F-13..
It seems that we are loosing us in all sundries…
I’m waiting to see book from the same author about MiG-23 vs F-14
http://http://cgi.ebay.com/Fighter-Performance-Practice-Phantom-versus-MIG-21-/290431956256?cmd=ViewItem&pt=US_Texbook_Education&hash=item439f17f520
adriannIt is not matter if 23 can reach max speed at lo altitude (in fact, graph shows that it exceeds its limit M1/1200 IAS). Initial climb rate has the same importance as SEP or acceleration as it is the same thing..Zoom climb is different since a/c looses true airspeed.
But let’s talk about 21’s climb rate ?? From F-13 to BIS ?? Dynamic thrust, drag and weight counts…
adriannI said one could think that 23’s climb is in Mirage F-1 class, according to that graph. But instead, it is in M 2000 class (with similar T/W, about 1). French are telling that 2000 has SL climb rate ~ 280 m/s, while from this graph 23 climbs at 190 m/s. Just an example of positive and negative marketing.
Dart shape is relevant, as for its lower max lift.
adriannSchorsch: For some Russian aircraft pretty detailed “Aerodynamic Manuals” exist. They have thrust and drag data as well as some other information (control limits).
One must take every manual with reserve. For example, in those aerodynamic manuals, you can see that MiG-23 (a/c with T/W > 1 and dart like shape and cross section) has such trust and drag that it has max climb < 200 m/s with 2 R-23 (?? lower than MiG-21 with ICs), you can see that Su-27 lift gradient (and resulting Cl) is higher at Mach 0.5 than at 0.7 contrary to laws of physics, MiG-25 has abnormal Cl w/o AFCS limit…
martinez your definition “rough with purpose” is an arrant nonsense in general. Compared to those aerodynamics manuals the F-4 performance data appendix looks poor and miserable. Some diagrams in other manuals might not be as accurate as you would wish, mostly bcs they dealt with different aspects of pilot instructions, but when important the weight info was there. I wonder, whether you are refering to the Serbian book when complaining about data discrepancies?
To me, US manuals are often saturating with tedious details, I can’t imagine who can deal with all that drag indexes, unsymmetrical moments and w/o any interesting flight mechanics details that are not must for operator to know, but it is difficult to find mistakes. Soviet manuals are easy, interesting but sometimes with discrepancies. I am not competent to complain about Serbian book, but there are rumors that US graphs are matched with Soviet Technical manuals.
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(Maybe Serbs are not that stupid, remember they downed 117).
A funny comparison Actually, a hungarian brain Zoltan Dani, a former colonel of Yugoslav army found the way how to shot down US stealth, so therefore you should listen to Sainz here as hungarians are even smarter than Serbs in that matter. All I can see so far, you`ve sent diagrams without weight info copied from former soviet or serbian Mig-21 manuals, so where is the “dot by dot conversion” to flawless F-4 format?
Unfortunately and thanks God, I am not Serb, but incidentally my grandma was Hungarian, anyway it is not matter where you are from but in what surrounding or system you live, does it provide independent mind and education. I have heard that in former Yugoslavia all that was possible and all that died with it.
Weights are with half fuel and AA armament in attached graphs. Dot by dot conversion is in cited book.
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Regarding Serbian book, please send the page where all soviet manuals are listed , those ones used to create that book. thanks
I think that all about that matter is on its back cover.
From your attached instantaneous turn F-13 graphs, I checked just one figure, 7 g and Cy max at 5000 m altitude and I got Cy max higher than in any Soviet manual at that Mach. Next figure, for 6.5g at alt 10 km is lower than in US evaluation.
sainz Quote:
Btw. When talking the best all around turn performer among exported Mig-21versions, definitely the Mig-21PFM (Fishbed-F)according to manual data and memoirs of my colleagues, former fighter pilots of CSLA.
It is probably difficult to rate all variants all-around. Drag and dynamic thrust are important. Lift and controllability even more. Early versions excels. BIS model has 15-20% higher ratio of inertia moments in yaw to roll. It certainly results in more sideslip during rolls and somewhat lower stall angle of attack, angle when breakdown of dynamic directional stability occurs IF FLOWN UP TO. But the prevailing factor in this equation is the dihedral effect i.e. roll stability and it is the same in all models because it depends on airflow around the delta wing, so it can be expected good behavior of BIS model at low speeds also.
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