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Andraxxus

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  • in reply to: Size of the new 5th gen fighters…too big !? #2224191
    Andraxxus
    Participant

    Engine limitations are what limit speed. The F-16 has a limit due to its fixed inlet, whereas a variable inlet likely would have allowed it to match the F-15’s max speed. There is nothing to suggest the F-16’s max speed is limited by drag.

    If Thrust was greater than drag, it would mean F-16 could have accelerated further, simple physics. Fixed inlet reduces pressure recovery and dynamic thrust at and above transonic regime. By Mach 2.0, pressure recovery is possibly less than 50%, add to that already low air density at high alt, reducing the thrust. Lower generated thrust means “thrust = drag” equity is reached at lower speeds, hence lower top speed.

    A variable inlet would improve pressure recovery, in many cases even above what engine could handle so there are bypass doors to regulate. This improves thrust, greater thrust overcomes greater drag and top speed improves. So, whatever the reasons, the statement is true.

    in reply to: Size of the new 5th gen fighters…too big !? #2224338
    Andraxxus
    Participant

    Yes if you design a plane to kill entire army at once you need to have a huge plane.

    You are missing the point. Design, be it small/medium/big, heavy/light, long ranged/short ranged, HAS to have design GOALs.

    Pratically I don’t comment on the idea of designing a small aircraft. I disagree about the method of doing so, and without specific purpose, a design cannot be said to work or not.

    For example you state, 3000 km ferry range is enough for your design aircraft. That is something, a numerical goal, but you fail to specifiy how much space for fuel your design has (in litres or m3) or how draggy it will be (Cd0, Cdx, wing Cd, inlet area). Those are part of preliminary design, a crude calculation made on excel before going further into design. Otherwise, your design would be unrealistic more like a concept design for sci-fi film or cartoon, or a child’s dream fighter.

    For example, you say combat range is 1000 km. An F-16 has 1288 km hi-lo-lo-hi combat range on bombing run when using 370 gals (when using 88nm combat zone radius), flying 892 km on externals, before dropping them. So without EFTs, an F-16 will have around 850-900 km combat range on internal fuel alone, depending on different CZR entry points. Your design apperantly has less than 2/3 fuel of F-16, and has less efficient engines. Will it achieve even 500 km combat radius?

    You say M3.0 capability. Top speed is the point where drag equals your thrust. 33% less thrust than F-16, same drag, same fixed inlet configuration. F-16 goes M2.05, how will your design go any faster than that?

    You say 30300 ceiling. F-16 has 18000 meter ceiling. With same wing area and less thrust, how are you hoping to make such improvement?

    9.5 G is not easily achived…I made a wooden racer R/C craft with 22 G limit. The fact is that if you make the plane lite it also endures easily more Gs.

    The Willy Messerschmitt HA-300 was 3200 kg empty with 47 kN engine…the F-CK-1 is 6500 kg with 2 x 42 kN engines. If you use wood in a strongly “lifting body” layout I bet you get 5800 kg empty weight easily..and 9500 kg Mtow. I am convinced it can do 15 Gs.

    9.5Gs at 9500 kg means 886110 Newtons. As lift will be generated by wings, there will be a maximal bending stress at the main wing spars. In roughest form, its a simple 3 point bending; each wing providing 443 kN lift at their lift centers, and aircraft weight at 9.5Gs = 886 kN providing equal force in opposide direction.

    http://fog.ccsf.cc.ca.us/~wkaufmyn/ENGN45/ENGN45_Online_Homework/06_Homework_MechBehavior_SOLUTIONS_files/MOR.PNG

    b will be total sum of thickness of your wing spars, h will be height of your wing spars. L will be the distance between lift centers, F will be your 886110 newtons. Instead of MOR, you will use 74 MPa which is the modulus of rupture of strongest wood, Cherrybark red Oak.

    Also at the wing roots, there will be shear stress where your wings will try to “cut” themselves off from the body, which is far more problematic for wood but I wont go into that. Simply make the calculation above and see how laughable your assumption about 9.5G is. You will possibly need far more wooden area than the entire wing airfoil.

    in reply to: Size of the new 5th gen fighters…too big !? #2224409
    Andraxxus
    Participant

    is that you don’t understand different phases of designing…we are at preliminary planning…not in detailed workplans.

    Oh you are wrong about this one; As a mechanical engineer, I am very well aware of design phases, and I am saying first phase of designing is laying out the technical specifications of your design. You can’t start designing a car, without defining if its a family sedan, sport sedan, grand tourer or executive class. Yet your first order of business is to put a twin-turbo V6 because it sounds good and modern. On simpler terms, you cant design a pump without specifying how much of what fluid its going to pump. For the aircraft its exactly the same. Before you even start drawing the first line; you have to decide on performance factors.

    -what is the design combat radius with design payload.
    -what is Maximum payload.
    -Ferry range.
    -G limit with design payload.
    -Top speed.
    -design acceleration at varying conditions; #1 = ? #2 = ? …..
    -instantenious turn performance at varying conditions; SL, 30k, clean, specified AAM payload, specified A/G payload.
    -sustained turn performance at varying conditions;
    -RCS (if calculable) at varying angles.

    An ideal design should be smallest and cheapest one to match or exceed all those paramaters. You shouldn’t be drawing your first line without specifying those. Doubling your G limit will roughly double your empty weight, and so will your wing design engine choice will differ. To increase the ITR you have to increase wing area, and your range, acceleration, top speed and STR will suffer. If you want to have good ITR and STR at the same time you will need bigger engines. bigger engines will need more fuel so design enlargens; to match all the parameters on the table.

    For example, I attempted to do preliminary design for a -rather ambitious- aircraft with following goals, merging a subsonic strategic bomber, supersonic tactical bomber, air-superiority fighter and an interceptor.
    -36 Mk-82s internally to 1500 km combat radius.
    -12 AIM-120s internally to 2000 km combat radius.
    -3 Kh-55s internally to 3000 km combat radius.
    -Ability to carry GBU-28, Kh-31, Kh-55 internally.
    -4 internal BVR missile carriage outside main weapon bay.
    -9G capability with 4 AAM missiles and 50% fuel.
    -Mach 3.0 capability with internal payloads.
    -15 minute Mach 2.5+ capability with 4 BVR missiles.
    -25000 meter ceiling with 4 missiles and 50% fuel.
    -32+ deg/s ITR and 23+ deg/s STR at S/L
    -18+ deg/s ITR and 11+ deg/s STR at 30k

    I started with same specifications of F-15E, I ended up with two F-135s with variable ramps, 22,2 meter length, 109m2 wing area, 22000 ton empty weight (target), and 15560 kg fuel capacity, and still couldnt match all the parameters I’ve laid.

    You ask WHY aircraft is so big, the answers are above. If you are going for “small” you can sit a pilot on an Teledyne J-69 add pair of glider wings and a fuel tank, it would fly too. What good it would do is another issue.

    in reply to: Size of the new 5th gen fighters…too big !? #2224692
    Andraxxus
    Participant

    Empty area in F-16’s fuselage is much greater than you specify;

    [ATTACH=CONFIG]227356[/ATTACH]

    If you compare with official cutaway from flight manual;

    [ATTACH=CONFIG]227357[/ATTACH]

    Almost every space within F-16’s body is equipment bays or fuel tanks.

    Going from F-16, you are trying to make a thinner version of F-16 by switching to two/four engines in ventral pod-like arrangements. If you do that, you have to relocate anything within lower equipment bay and the lower part of forward equipment bay to somewhere else. Also, with deletion on inlet, you have to relocate forward LG to somewhere else.

    The problem is you are thinking aircraft = engines + pilot + gun + radar + missiles, and rest of the area goes to fuel.

    Even within the definition of “fuelling system” alone you will need numerous transfer and pressurization pumps, valves cutoff/shutoff valves, ventilations for each reservoir, a halon reservoir for inerting presure, halon/air mixing valves, relief valves, electrical control equipment, wiring and sensors etc etc, then there will be fuel flow proportioners, only to provide a consistent fuel flow to the engine in all flight conditions.

    Then there will be engine fuel boost pump, providing fuel to AB fuel pumps and main fuel pump. There will be a digital engine control system, directing two sub control systems main engine control system MEC and AB fuel control computer AFC. There will be dozen servos and valves, and some fuel/oil and fuel/hydrolic heat exchangers before fuel finally reaches the engine.

    Even this is a VERY complex system and all these machinery electronics, 50++ meters of piping 100++ meters of wiring takes space within the aircraft.

    When you go into FLCS and hydrolics, you will need huge FLCS accumulators, two redundant hydrolic systems each containing an EPU driven and an engine driven hydrolic pumps, filtration system, piping to heat exchangers and an reservoir pressurazion accumulators. Than depending on redundancy, one or both of those systems will provide hydrolics to LE flaps, rudder, horizontal tails, flaps, ailerons, speedbrakes, FFP, LG system, NWS, drag chute system, AR, brakes, JFS systems etc etc. There will also be indepenendent accumulators for brakes and JFS. All of those system will have actuators, and pressure relief/return valves all around.

    Then comes the EPU, and there are hydrazine and nitrogen bottles to operate in emergency conditions. Beside the auxillary gear box driven main and stby generators, EPU also drives an emergency AC generator.

    To stop an aircraft on landing, there is brake system with brake fluid reservoir, a parking brake, both redundantly piped to be opareated both by hydrolics and a hand pump. Most aircraft carry a drag chute and a release mechanism, which also occupy space.

    Those are all essential equipment only to make an aircraft take off, fly and land. If you want a piloted aircraft, and you want your pilot to actually stay alive in the aircraft, you will also need a environmental control system, with a turbine/compressor assembly, modulating valves/flaps, and a different pipings for high/low pressure, cool warm air, bleed air and ram air areas. ECS also interconnected to fuel system for fuel tanks pressurization.

    So in short, there are many equipment that you discount, and those are the reasons why aircraft are so big. Then you want a fighter aircraft, this will add a million different equipment to the aircraft too. Each MAWS sensor will measure around 30-40 cm box, each RWR will occupy space, an internal jammer will size as much as ALQ-131 pod etc etc etc. When you put all those equipment I am actually impressed how small Rafale etc is.

    in reply to: Size of the new 5th gen fighters…too big !? #2224796
    Andraxxus
    Participant

    To be honest, I haven’t gone through all the post in this topic, but I would like to state out some fundemental errors regarding to design, (which may be pointed out or already solved in the posts i lazily skipped)

    First and most important issue is, drag is mostly related to the wing area, not the frontal area. In most basic calculations in fluid dynamics course, drag from body and inlet are all neglected.

    Speaking of subsonic, and level flight, thickness of airfoil or even airfoil geometry is second to wing area. When we are talking about a modern fighter with energy maneuverability in consideration, its sometimes better (like on F-16) to have smaller wings.

    going from your F-16 example;

    A4’s 27,7 m2 vs F-16’s 27,9 m2 will mean they will have very similar level flight drag. They will require same amount of thrust for sustained flight, and same amount of fuel for the same range. With 30% inferior thrust, it will have around 30% worse acceleration. Assuming your design is lighter, lower wingloading will allow it will reach 9G limit earlier. With 30% inferior thrust, it will have inferior sustained turns, with gap closing at higher altitude/slow speed conditions due to lower wing loading.

    What is more troubling is the lack of volume inside the aircraft; F-16 can carry 3175 kg fuel internally. Using 800 kg/m3 for fuel density, you will need approximately 4 m3 fuel tank area, and that is NET capacity, excluding the structural components, fuel pumps, piping and other equipment that would go inside the fuel tank. I am designing -a rather flawed- aircraft for fun myself, and I ended up in 15560 kg fuel capacity from 26.1 m3 fuel tank, Resulting around 600kg/m3. F-22 for example total fuel capacity of 13022 litres, and 8200kgs, results in 629 kg/m3.

    Assuming your design carry 500 kg fuel inside your wings just like F-16C, you need to put 2675 kg fuel inside your fuselage to match F-16’s range. Going from 629kg/m3 just like on F-22, you need to put a 0,6x1x4,5 meter box inside, and you clearly don’t have such volume on your design. Worse, 4 smaller turbofans will certainly have higher SFC, and as an EFT is out of question for a 5th gen fighter, you will need much greater fuel capacity than F-16.

    4 smaller engines will result in much greater maintanence costs, and 4 auxillary gearboxes, 4 individual inlets will all contribute to weight and take volume, which your design clearly lacks. Also you have to spare additional volume for APU, all the avionics, FCS, oxygen generators/bottles, hydrolics tanks, oil tanks, coolant tanks at least, plus additional equipment of 4+ 5th gen fighters such as IRST, MAWS, internal ECM will take space. In the end your design will end up in similar size to Typhoon at least.

    When designing an aircraft, design requirements dictate the shape, engine number etc etc. If I were to suggest; Find a easy-to-use 3d program, draw placeholders for all the equipment you want to put onto your aircraft. Chose an engine and approximate fuel volume for an approximate empty weight.. Select and use an appropirate airfoil and wing area, for the maneuverability criteria you desire, and determine its level flight drag. You will find your allocated fuel and/or thrust to be excessive or insufficient, resize fuel tank, re-select a new engine, and re-calculate the wing specifications accordingly, required thrust/fuel capacity will be changed again and after several iterations, this will result in a preliminary design study, which you can go on by adding structural calculations into these iterations. Since you are doing this for fun, basic formulae from strength of materials should suffice, giving you some structural material and weight data. Weight will be changed once again, and likely the load bearing structures will not fit to the areas you desire, so you will have to -once again- recalculate fuel capacity, wing geometry etc from the start. You can test your end result in ANSYS fluent or similar CFD capable FIA programs. Which by then you can add lerx, chines etc to modify/control vortices, determine the size/need of stabilizers, rudders, fins etc etc. Those results will likely to force you to modify your original design, and as a result, you will have to re-iterate everything from the start, until you have met all the design criteria you wanted to match.

    Andraxxus
    Participant

    1- It depends; flying too fast means too little time for correctly eyeballing targets and maneuvering to attack them. MiG-29 is already fast, it doesnt deploy LE flaps or anything.
    2 and 4- It possibly due to camera and cameramen, which unfortunately uses high shutter times and small diapragm opening and/or small CCD (likely to be a cell phone). As gun blast happens very fast, gun flash images can blend with clean MiG-29 images. Looking frame by frame, it does originate from correct place, but as camera shakes and flash is a too bright light source, it kinda shakes around. This kind of compositing on AE is very difficult to achieve.
    3- Maybe, maybe not due to gas expansion occurs too slow relative to aircraft’s speed, and circular looking muzzle flash can form in front of the aircraft. IDK about that.

    However, what suprises me is that it actually sounds right. Gun fires without sound, then explosions then the sound of the Gsh-301 firing. Happens due to supersonic muzzle velocity. I don’t think any uneducated syrian rebel would think about this while faking a video.

    in reply to: F-16 goes kapooya kapooya on Mig-29! #2230492
    Andraxxus
    Participant

    Its not a crash but turbulance caused by the stalled wings of Su-27 making cobra hook or tailslide. Smoke can be due to wingtip generators flares or combination of both. for example: http://youtu.be/JjNj3TWO_Q0?t=55s

    edit: it does not look like same image; smoke profile is different.

    PS; in his interview Syrian pilot said, he flew 7 km inside Turkish airspace. While I am from Turkey, I believe this is more logical than TSK statement, and would better explain how aircraft headed north, then west and then crashed 1 km south of turkish border at kesab.

    Though those statements are not contradictory; TSK may have meant greatest distance of intrusion is 1.5 km, and total flight distance can be 7 km like Syrian pilot said.

    in reply to: The PAK-FA News, Pics & Debate Thread XXIV #2230563
    Andraxxus
    Participant

    Will it be s-ducts, radar blockers, or something else?

    No consesus about this on this forum. All agree it has slight S-Ducts but not enough to cover entire compressor face. Then there are many opinions;
    1- there will be seperate radar blocker: idea is based on some patent designs, and possible presence of an available place on the PAK-FA inlets.
    2- there will be a blocker, but integrated to the inlet guide vanes.
    3- there wont be a blocker, and compressor itself will be built by special radar absorbing composites, based on some advanced materials recently developed by russian companies.

    Fortunately most people in this forum prefer thingking/brainstorming to plain, ignorant anti-russian bias.

    in reply to: F-16 goes kapooya kapooya on Mig-29! #2230760
    Andraxxus
    Participant

    The downed aircraft is a MiG-23; according to Turkish Armed Forces statment;
    -At 13:01 BIKIM (roughly translates as, integrated control&warning center) starts tracking two MiG-23s 80nmi away from Turkish borders.
    -Until the aircraft has reached within 10nmi of Turkish border, they were warned 4 times. One of the MiG-23s broke off and turned away, while other maintained course and crossed border by 1 km at 13:13, then headed west and flied within Turkish airspace by 1.5 km.
    -At 13:14 F-16s from 181st Pars Squadron engaged and shot down the MiG-23 with a single missile, which was headed for west.
    -MiG-23 crashed 1200 meters south of Turkish border, pilot ejected.

    In the interview with Syrian pilot admitted crossing the Turkish border while trying to track terrorists.

    The AA image is possibly a Su-27 making cobra with wingtip smoke generators.

    in reply to: A "Rough" F-35 Kinematics Analysis #2230980
    Andraxxus
    Participant

    And again, above statement should also apply to 70s era of fighters? Also, MiG-25 and R-40 missiles do have kill records againist fighters.

    @Trident; Speaking of BVR; To be honest, I find the possibility of R-40R shooting down an F-4E at 30-40 km hundred times greater than an AIM-120 hitting an Su-27 at 70-80 km. A -lucky- R-40T managed to shoot down F-18 didn’t it?

    in reply to: A "Rough" F-35 Kinematics Analysis #2231525
    Andraxxus
    Participant

    This, again turns into a MiG-25 discussion, which was not my intention. However if we are going into it;

    We have to consider MiG-25 belongs to a 3rd generation of fighters. While MiG-25 is only regarded for its speed, it also had the best radar/missile combination for BVR combat of its time. Its unfair to compare it with F-14 or F-15, just as it would be unfair to compare F-4E with Su-27 or MiG-31. (Though I will do such comparison later).

    When we look at 3rd generation fighters and interceptors, apart from MiG-25, there were F-4 and Su-15 in heavy class, and F-5 and MiG-23 in light class.

    Lets debate, which one of those 4 fighters could confront MiG-25 in BVR combat? None of them had any single metric that gave an advantage to play. MiG-25 has the ability to engage/disengage at will, flies above both their flight envelope, and their missiles’ target envelope, it has longer ranged radar, longer ranged missiles etc etc etc.. In 1970; MiG-25 would have simply dominated the skies.

    With the introduction of F-15A/AIM-7*M* combination, only advantage of MiG-25 remained speed and ceiling; and that advantage turned out to be debatable; Therotically F-15 could track, chase and shoot at MiG-25 under some circumstances (and it did in practice), but theoratically, MiG-25 could also fire back with its now-obsolete missiles, and theoratically also outrun the F-15s. All 3 theories proved to be correct in practice, and we are still debating if speed is really important or not. Putting this discussion aside;

    Lets reverse the roles; SU makes the Desert Storm, and tries to achieve air superiority with Su-27s, MiG-31s. Those aircraft are supported by AWACS and GCI radars, all use datalinks, and are in overwhelming numbers. Opposing force has poorly maintained, poorly flown F-4s, poorly armed with obsolete AIM-7Es.
    1- Do you think its possible for a lone F-4 will able to dodge eight AWACS/ELINT-assisted and fully datalinked Su-27/MiG-31s and be able to mission kill the aircraft they are escorting?
    2- Do you think its possible for two F-4s to shoot two approaching Su-27/MiG-31s before they do, and evade all of the 10 R-27RE/R-33 missiles fired by four of them?

    You may disagree, but for me, both scenarios are mathematical impossibility and I think this tells why speed is extremely useful.

    By the way @Sens, you are talking about “corners” of flight envelope being unimportant. I would agree if we were comparing F-15 with F-16, but 60k feet (18km) M2.0 is right at the center of the MiG-25’s flight envelope. Now the “corner” definition is relative; Are we talking about the “corners” of MiG-25 envelope where there wont be a F-15, or the corners of F-15 envelope? This also slightly disagrees with the first part of your comment. While F-15 does provide too little lift with too little exess energy to make any maneuver (and it truly is limited to small banking maneuvers) at around 60k feet, MiG-25, is in a pretty “safe” condition, right in the middle of its flight envelope. Surely it has excess power to go higher or faster, this excess energy can also be used to sustain a -relatively- quick maneuver.

    in reply to: Naval deployment to Black Sea? #2031285
    Andraxxus
    Participant

    http://www.janes.com/article/35260/turkish-milgem-and-lpd-naval-projects-allegedly-rigged
    Turkish Milgem and LPD naval projects allegedly rigged

    RMK shipyards are owned by Koç Holding. During gezi incidents, Koç holding opened up their Divan Hotel to protesters and supported the anti-goverment protests. Now the goverment wants to take multi billion $ bidding away from the Koç Holding. In short: You know nothing about our internal matters. I accept there is corruption in govement and some moronic Islamist guys still supports the goverment them despite the corruption. More, there are billions of religious and social problems in Turkey I would complain about.

    However, this is a military discussion, and all of these are irrelevant. According to any and all sources you can find on the internet, we still maintain 3000+ tanks in active service, we still maintain around 400 combat aircraft in active service, along with the Navy units I mentioned 50 times. We still do maintain our cold war numbers, and we don’t need this kind of army only to protect ourselves from Greece or Syria or anything. If we had slightest trouble maintaning our armed forces, we could have easily shrinked our army to 400 tanks and airforce 200 combat aircraft just like any EU country did, but we choose not to. Also, I’ve provided independent sources that both prove we have 18b$ military budget, and that is ever increasing from year to year. If you have problems believing in any of this, the problem is really you.

    I will repeat myself; Everything you say irrelevant to these discussions. You run theories and they are wrong, thats it. You make Russian propoganda, by denying even the FACTs that Russians accept. So all you do is losing your credibility.

    Turkey has 10 times more ships but Russia can deliver 1000 times more antiship and anti radiation missiles from Air and in very short period of time. each Flanker can carry six of them and can be reloaded from far off airbases outside from cruise missile range. so your history lesson does not apply.
    Russia is exporting huge amount of arms to Middleast and at the end it will jump into it to tip the balance. Turkey does not have any business.

    Stupid and childish comment and I wont enter into pissing contest. However i will have say these;
    1-Russians dont even have 1000 air delivered antiship missiles in their inventory; In fact, only Tu-22M3 and Su-34s are capable of delivering dedicated anti-ship missiles. Other than that; some upgraded Su-24 and Su-27/30s provide Kh-31A.
    2-Flankers cannot carry ANY antiship/antiradar missiles. Only upgraded ones, which is less than 1/3rd of the Su-27 fleet.
    3-I am sure Hitler said Napoleon’s history lesson about invasion of Russia did not apply too. “Those who cannot learn from history are doomed to repeat it.” is a really nice quote.

    By the way some another fact; Tatar Turks which constitute the 12% population of Crimea is now represented in Crimean Parliament by 20%. Each individual Turk in Crimea gets almost double representitive rights of a Russian. (1.6 per person vs 0,9 per person). I am 100% confident your RT will fail to mention this, as -almost certainly- will rest of the world media, but we certainly got what we want :stupid: Have fun proving your theories.

    in reply to: A "Rough" F-35 Kinematics Analysis #2231620
    Andraxxus
    Participant

    Exceed M2.83 if you’re okay with breaking the engines.

    Interpolating the envelope graph gives around M3.1/3.2 top speed. However, that not the point and importance of the ability. Its a room for less than optimal/clean conditions. MiG-25 can dash at M2,83 when armed with 4 missiles. Ability to exceed its mach limit in a way allows this.

    And of course the MiG-25s performance is pretty much limited entirely to being able to go very high and very fast as it was built for that. The F-15 meanwhile had to be a strong opponent in a much wider realm of speeds and altitudes.

    No one is denying that? Bias, and pro-F-15 defense aside, comparison is strictly about F-15 pilots claiming to go M2.5 to catch MiG-25s. Which is irrelevant of any qualities F-15 offer, its beyond the abilities of F-15. Mach number limitation aside, a clean F-15A is not a bit faster than a clean MiG-29 on real life conditions.

    There are many idiots who fail to understand that at seem to think that the MiG-25’s can hit such speeds at low and medium altitudes.

    True, at lower altitudes MiG-25 is limited to subsonic, and at medium altitudes remain comperable to any other fighter. Does this change the fact I am stating? That MiG-25 is WAY faster than F-15?

    Plus just about anything other than an SR-71 could turn circles around it.

    Untrue; just like flight envelope this -again- is a difference in its design altitude, can you say an F-15 can sustain turns better than a MiG-25 at 50k feet? or 55k feet where F-15 can’t go supersonic? At 75400 feet, there wont be an F-15 other than zoom climb, but MiG-25 will still be achieving some sustained turns.

    Where do you get these figures for the F-15?

    F-15A manual, IIRC posted the clean level flight envelopes to someone a few posts ago.

    EDIT: Apperantly I didnt; here is the page:
    [ATTACH=CONFIG]226518[/ATTACH]

    Compare with MiG-25’s:
    http://forum.keypublishing.com/attachment.php?attachmentid=164208&d=1217520140

    AFAIK that 102% thrust you speak off was enabled through some “V-MAX” button or switch or something.

    Yes; To quote the flight manual; “Vmax Switch: Use of Vmax Switch is prohibited. The Vmax switch is below the left canopy sill. The switch has a guard which is wired down. When the wire is broken and guard raised, the switch may be placed to Vmax which arms the system. With the system armed, throtle in MAX AB, and airspeed above MACH 1.1, the engine control schedules a 22C increase in FTIT and 2% increse in rpm. Main engine and afterburner fuel flow is incresed about 4% and thrust is increased about 4%. Maximum continious time in Vmax is 6 minutes. Each use of Vmax must be reported so that a hot section borescope inspection may be performed. Maximum total Vmax time before engine overhaul is 60 minutes.”

    As you can see, this is not an ordinary operation. The very description starts by saying its prohibited, the switch itself is not only safety guarded but also wired, and it has high probability of damaging the engines. Its comperable to overspeeding a MiG-25. Also while Vmax is allowed for 6 minutes, airframe limitation section marks area between M2,3 to M2,5 as “time limited pursuit” and limits it to 1 minute.

    Again; even with engine trim of 102%, its top speed reaches M2,35 on STD DAY, M2,5 on STD -10C, and M2,1 on STD +10C atmospheric temperature conditions.

    With Vmax switch on on STD DAY, F-15A is only fast as Su-27S (M2,35). When off, its fast as MiG-29 (M2,25). No dreams about it catching a MiG-25/31.

    in reply to: A "Rough" F-35 Kinematics Analysis #2231765
    Andraxxus
    Participant

    BTW; I think this last claim shows what Sens trying to say about claims being “comperable”:

    A clean F-15A at normal engine trim on a STD DAY can go up to M2,25 top speed. To reach M2.5, F-15A needs to have its engines overtrimmed to 102%, and operate on a day 10 degrees colder than the standard day. That is, M2,5 is achieved only at 45000 to 52000 feet.

    MiG-25 can exceed M2,83 from 59000 to 75500 feet on STD DAY.

    On a STD day if we compare unmodified aircraft, F-15A is clearly slow and low flying againist MiG-25, and the test pilots’ claim is false both on technical data, and the tactical assumptions.

    What pilots saying isn’t a lie, F-15A CAN reach M2,5, but they fail to mention the “conditions” for that ability. There will be many idiots on many forums that fail to understand the effects of those on performance, and claim F-15 is only slightly slower than MiG-25, because they take the word of AF pilots. Is it???

    Moving to even more unfavourable conditions; +10 degrees celcius hotter than STD DAY: a clean F-15A cannot exceed M1,95. Put only empty pylons, and F-15A wont pass M1,75. Funny thing is; MiG-25 could STILL exceed M2,83 in that same hot day. Now how could one claim F-15A is nearly fast as MiG-25?? No, it BY FAR isn’t…

    Unfortunately, for test pilots, pimping up the aircraft they are piloting is always the case. I expect many similar facts surfaced when F-22’s technical specifications are unclassified.

    in reply to: Naval deployment to Black Sea? #2031331
    Andraxxus
    Participant

    yep; IIRC, it was during overhaul where funding was canceled. I ask why Russians just didn’t cut funding to maintaining/upgrading Smetlivy instead and upgraded Ochakov with some modern weapons and be done with it? Kara class use very similar hull to Slavas, its larger than Udaloys. Surely there is room on it for newer weapons? Any reason? IMHO, its illogical to scrap/scuttle two of your cruisers, when your shipyards have trouble building new ones; and you really need such ships?

    By the way can anyone list which Ukrainian ships are still in Sevastopol?

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