CLASH OF THE TITANS Su-27 vs F-15 Predrag Pavlović, dipl.ing. Conflicts in Vietnam and the Middle East revealed a number of weaknesses and conceptual faults in 2nd and 3rd generation Mach 2 fighter- interceptors. Fighters of so the called 4th generation (F-15, Su-27 etc.) besides agility, which can cope with late WW2 fighters, have the ability to detect targets below the horizon, at a very low altitude. It seemed that until the appearance of the next generation fighters, no plane would have a better overall capability than the F-15. Ten years newer, the Su-27 has an internal fuel range comparable to rivals with additional external tanks, better subsonic agility and an innovative weapon concept. 1
• The primary requirement in the design of the late 50's fighters was the speed needed to intercept supersonic fighters / bombers. To reach speeds greater than Mach 2 with available engine power at that time, most manufacturers considered it was necessary to make a number of compromises. • In order to reduce drag, wings suffered and were dimensioned for max. acceptable landing speed of 270-315 km/h. If a configuration allowed, by the way, a slow minimum speed / good maneuverability (at angles of attack [hereinafter α] 2-3 times higher than landing α), it was not taken seriously because attention was focused on Mach 2 and not on that flight domain. These planes (F-106, MiG-21 for example) did not have the necessary thrust or relative wing span to sustain such maneuverability in continuous turns. • The need for wave drag reduction made canopy flush into fuselage and the pilot was supposed to solve the interception flight-path problem by ‘chasing the dot’ in the radar display, so the field of view from the cockpit was minimal. • Rolling at the g-load or noticeable α was such that aircraft often responded opposite to pilot inputs or went out of control (departed). • Range was less than desired, it was necessary to defend the homeland far away from home. 2
• On the so called 4th generation fighters, these flaws were corrected. Confirmed were the importance of a large radar, medium-range AA missiles and surface radar / AWACS support. Planes and pilots brought back close air combat capabilities so situations where old, subsonic fighters outclassed Mach 2 interceptors (as earlier when Gnat and Hunter succeeded vs. Mirage 3 and F- 104, and MiG-17 vs. F-4 / 8) would not be repeated. • The first 4th generation fighters were the F-14 and F-15. Tomcat was less convincing because it did not have the thrust required. F-15 configuration - wings, tail, fuselage and engine intakes (of type that at supersonic speeds unloads tail, similarly to canards) is inspired by MiG-25. More cambered airfoil, more proverse relation of moments of inertia (i.e. relatively larger wings) and later mentioned factors give it a more docile handling. The designers thought that big wings eliminated the need for LE slats / flaps, reduced cost and simplified maintenance. Impressed with the MiG-25, planners in the U.S. initially requested Mach 2.7 speed. 3
• The US knew the rough dimensions of the MiG-25 • The US fighter of the time was the and demonstrated performance records (people slatted F-4 Phantom. Soon after, at McDonnell Douglas thought some things USAF abandoned Mach 3 couldn’t be done without additional rocket motor) interceptors XF-108, YF-12 and but the weight of a MiG-25 was unknown at that later also Navy F-14 and 3-engined time. Only after defection to Japan in '76 it was Vigilante, interceptors considered found that subsonically it is in the F-4 class by USAF. because of the engine cycle (turbine inlet temperature and pressure ratio) required for high-speed flight and heavier weight of the conservative materials in the structure of the aircraft. Later, the US quit high Mach requirement because of the huge fuel consumption of TF engine at that speed (until the revolutionary solutions in the compressor) while available fuel was modest. Also, the cockpit transparency area would be limited, much like of F-4. It was impossible to merge the performance of a MiG-25 with other requirements based on experiences gained in Vietnam. • The 4th generation fighters caught Soviets mid- step because they had just deployed inter- generation fighter / interceptors MiG-23 and MiG- 25. The first followed the trend of that time - variable geometry (VG) wings with all the advantages and disadvantages that this brings, and the other went on the road less traveled – its flight domain practically starts where the speed / ceiling of other aircraft end. • Other types of that inter-generation were the French Mirage F1 (with unsuccessful VG Mirage G8), the Israeli Kfir and Swedish Viggen. 4
The main features of 4th generation fighters, besides agility and wide field of view that cockpit transprency allows (the pilot in an F-15, sits more ‘outside' than inside the cockpit), is the ability to detect and engage targets below the horizon, at a very low altitude - in the presence of ground clutter. Increased maneuverability of 4th gen. fighters is achieved through: • Large wings (in span & area) that brought back the minimum speeds of early jet fighters (such as F-86) of 200 instead of 270-300 km/h. This allowed a two times tighter turn radius. A side benefit is slower landing speed of 225-250 km/h, at lower α, which means that fleet will not be spent in peacetime accidents on landing. • More engine power (all relative to the weight of the aircraft) which allows sustaining a 40% higher g-load without losing speed and the maximum rate of climb increased from about 150-220 to 230-330 m/s. Max thrust without afterburner for a given air flow, depends on the temperature that turbine can withstand, without burning. A significant increase in thrust of that engine generation is achieved with the use of directional solidification of nickel superalloys, similar to choosing the direction of graphite fibers in epoxy resin (polymer composites) gets greater strength of the composites in a stress direction. The first engine that used that metallurgy in the West was J58 that powered the SR-71, a 1st fighter engine, F100- PW-100 which powers F-15 and TF30-P-100 for F-111F bomber. Combined with air cooling for the turbine (hot compressor air), an increase of about 300ºC (from about 1100 to 1400) was achieved, compared to the previous generation. Further development in turbine metallurgy were single crystal blades (whole turbine blade in one crystal) applied after 1986 with much fanfare on the F100-PW- 220. L-julka AL-31F, the Sukhoi 27 engine, has a single crystal turbine blades cooled by compressor air previously cooled in the heat exchanger. 5
The last of the Soviet fighters designed before the collapse of their ideological system. Their leaders failed in promotion of ethics and social justice, so the people opted for consumer freedom, vice and justice for corporations. 6
The F-15 Eagle is an all-weather, tactical fighter of extreme performance and maneuverability, designed to gain and maintain air supremacy over friendly or enemy-controlled airspace. It is the fastest conventional fighter with agility and avionics unmatched until MiG-29, Typhoon and Rafale, fighters that entered inventory 10 (MiG) to 27 years later (Typhon). 7
L-julka AL-31F, Sukhoi 27 engine, has a single crystal turbine blades cooled by compressor air previously chilled in the heat exchanger. The second, less well-known contributor for thrust increase and weight reduction is in the turbofan concept itself. It has lighter turbo-machinery weight (about 200-300 kg in this class) and higher afterburner thrust increase (more unused oxygen in the bypass channel. The compressor diameter (weight) is much smaller than that of turbojet (see GE129 scheme). That’s why only 60% of the air is compressed to 23 atmospheres, and the remaining 40% to 3 atm only, for example. Specific fuel consumption is 25% lower than the in previous generation fighter engines, partly because of the higher compression ratio (about 24 vs.14) and partly because thrust of bypass air has slower exhaust velocity. AL-31F has active compressor stall protection measures (e.g. when flying behind another aircraft or when missiles are launched) for stable operation of the engine, which is the standard previously applied even in the MiG-21. 8
• Better structural and volumetric (for fuel and systems) efficiency due to wing-fuselage blending. Wing-body fairings give the wing root rib more height increasing structural rigidity and strength, or vice versa, for required strength weight of the structure could be lighter. F-15 and Su-27 both contain a high percentage (25-30%) of titanium alloys for better strength / weight ratio than steel or aluminum, resulting in a weight reduction of 20% of those structural parts. Less known is another feature of newer materials, given in the table: Material Cost in the U.S, late '80s Material price ($/kg) Aluminum AL 2024-T4 3.3 Aluminum AL 7075-T6 11.8 Carbon epoxy composite 357.5 Steel D6AC 4.4 Titanium alloy Ti-6Al-4V 502.5 • Improved controllability and stability: Adverse characteristics such as pitch-up and wing-rock, yaw divergence, adverse yaw due to roll and spin tendency are reduced or eliminated. To improve handling – i.e. to ‘fix’ pilot commands, Command Augmentation System (CAS) has been added to Flight Control System. CAS has a subsystem to reduce yaw during roll at high α (ARI Aileron-Rudder- Interconnect). Su-27 has α and g-loads limiter, while F-15 has subsystems for α, over-g and departure (yaw-rate) warning tone. 9
• Improved controllability and stability: Adverse characteristics such as pitch-up and wing- rock, yaw divergence, adverse yaw due to roll and spin tendency are reduced or eliminated. To improve handling – i.e. to ‘fix’ pilot commands, Command Augmentation System (CAS) has been added to Flight Control System. CAS has subsystem to reduce yaw during roll at high α (ARI Aileron-Rudder-Interconnect). Su-27 has α and g-loads limiter, while F-15 has subsystems for α, over-g and departure (yaw-rate) warning tone. To be docile i.e. not to have spin and loss of control / departure tendencies, a plane should have positive directional stability, favorable dihedral effect, efficient rudder and ailerons and proverse aileron yaw. The maximum usable α depends on the combination of these factors. It is crucial that dynamic directional stability along flight-path and factor called 'lateral control departure parameter’ (LCDP) i.e. roll response to roll command are positive to the highest α. It was found that if the LCDP is negative (opposite roll response), it will cause yaw divergence and if dynamic stability along the flight path is also negative, the plane will go into spin. Radome shape - depth / width ratio and curvature of the lower part of the nose cross section are considered factors which contribute significantly to the spin resistance. 12
Minimizing the coupling between roll and yaw axis is crucial for improved handling of the 4th and newer generation fighters. In fact, depending on the Mach and α, along the pilot commanded deflection of ailerons, the system adds rudder which reduces sideslip angle and provides an appropriate response to the rolling inputs. Similar control feedback (loop) helps aircraft to roll along the flight path axis and not about the longitudinal axis of the aircraft. Loss of control in the F-15 is not possible when α is less than 20º. At higher α, if there is any significant asymmetry of fuel, external payload or asymmetrical flow emanating from the nose (due to geometry erosion caused by years of service) increases susceptibility to loss of control / departure. ARI reduces pilot aileron inputs and therefore the aircraft is slower in roll response at higher α, but the aircraft is safer. Rudder inputs can make rolling faster - creating a sideslip angle, but there is a thin line to spin. At Mach numbers between 0.5 and 0.76 and 30-35º α, F-15 is directionaly dynamically unstable (along the flight-path), like many modern aircraft. In this domain, spin resistance is reduced. Otherwise, if the commands are placed in a neutral position at the first sign of loss of control (uncommanded roll or yaw) the plane will be 'back' under control. Good controllability at high α comes from effective roll and yaw controls (high-quality airflow around them, influence of LERX, rudder position out of disturbed airflow that comes 13 from h. tail and body) and aileron proverse yaw.
Su-27 is a newer airplane and therefore aerodynamically more refined. Wing profile with leading edge flap (LEF), at high α has more curvature providing more lift and lateral- directional stability. Ratio of flap chord over the wing chord length is higher at the wing tip than at the wing root, so when flap is deflected wing tip profile has more camber than root profile, resulting in proverse increment of pitching moment at high α. - Leading edge wing root extensions (LERX) / strakes large sweep angle generates vortices on the inner wings and Sukhoi fuselage, delaying stall. Same mechanism improves the static directional and lateral stability and significantly reduces buffet at higher α. These two innovations combined significantly reduce buffet, increase lift and lift-to-drag ratio in turn. - Wide fuselage, LEX and blended wing-body together form low aspect lifting area that continues to generate lift at high α, when the wing stalls. Attention is paid to the distribution of masses and side-area to obtain a combination which as sideslip angle increase gives a negative increment (nose down) of pitching moment, so that spin would be oscillatory rather than stable. - Sukhoi saw benefits of reduced trim drag by relaxing longitudinal static stability and incorporation of electronic commands. Su-27 is up to 5% mac unstable. Spin prevention system limits α to 24º at low Mach, but the system can be overridden as seen in Cobra maneuver. 14
When F-15 set the standards, other manufacturers such as Dassault-Breguet could later produce fighters better in one aspect, e.g. M2000 has more wing, relatively, for better instantaneous turns (but with greater speed loss) for faster target IR missile acquisition but overall, as U.S. military claims, none of the newer fighters, except for 'Stealth' has significant (>10%) better performance. It seemed that until the emergence of the next generation fighters, no aircraft would have better overall capability. F-15 has been operational for 35 years. Then came the Su-27, the Russian answer to the F-15. It was intended to be a superior aircraft so everything was designed 10% larger – from radar antenna diameter (by the way, radar is 2/3 heavier) to engine air flow i.e. thrust, aircraft dimensions...Unlike earlier short- range air-defense interceptors, Su-27 was intended primarily for combat over enemy territory. It looks like a combination of F-16 and F-14. The initial configuration of the aircraft did not have an appropriate position of the vertical fins which caused bad stall behavior. Also, wing geometry with double curvature leading edge, along with twist and camber in profile, was technologically difficult to produce. In the design of Sukhoi, special care was taken to the optimization of the cross-section area and distribution (see picture of nose to nose Su-27 / F-15). Relative size of cross- section area was about ¼ less than in competitors, which gives max. trimmed L/D of 11.6 compared to 10 of the F-15, which is equivalent to the addition of 15% of the engine power. The difference is noticeable in turns and range. Su-27 has the largest amount of internal fuel ratio relative to aircraft weight, which provides range as competition with additional external tanks. To keep the weight of the aircraft under control, structure weight had to be reduced at the expense of lower allowable g-load, 8 versus 9g standard, and 50-100 km/h less allowed airspeed (q). 15
When Su-27 appeared, it was a difficult tactical problem for adversaries. Range with internal fuel was 2 times greater than of the F-15A, turn performance and controllability better, radar had similar range, radar missiles had greater range because of inertial mid-guidance phase, large off-boresight angle, helmet cued IR missiles - 20 years before the West, were considered fatal. That's not all, because the Soviets were practised in smart attack tactics, where a pair of fighters would approach the opponent with crossing paths, together making a horizontal 8, which creates a tracking problem for the radar and radar-guided missile, similar to that of a deception jammer that transmits a phase-shifted signal (reflects false target position) which takes the radar centroid off the target, until the break of lock-on (like Sorbcija jammer). 16
Climb record breakers To break climb records to the tropopause (about 11 km altitude) an aircraft needs best thrust to weight ratio. The operational F-15 is still unsurpassed in that respect. Up to 20 km altitude, it is important that the plane also has great acceleration to Mach 2 +. To even greater heights, the aircraft must be particularly fast (MiG-25). These planes are also weight stripping champions. At the start of the attempt to the first height step (H=3 km) F-15's take- off weight was 12700 kg and the Su-27’s was 14100 kg. Stripped down F-15 had no flap and air brake actuators, cannon, radar and electronics, displays, generator, backup hydro- system and even landing lights and paint were missing. Sukhoi has gone even further and removed the ventral fins, tip of vertical stabilizers and an engine inlet VG ramp and aileron actuators. The F-15 took about 1 minute to 12 km altitude, from the start of take-off. It held the records to 3, 6, 9, 12, 15, 20, 25 and 30 km. The F-15 still holds the record to 20 km. The P-42 (Su-27) climbed about 10% faster all the way up to 15 km and the MiG-25 has re-taken the records to 25, 30 and 35 km. 17
Their engines were tweaked to increase thrust 5-10%, which gives them the thrust to weight ratio of 1.7 and 1.9 respectively (to H=3km). F-15 had the highest 'spec. excess power' about 420 m/s at 0.95 Mach, SL. That means it could climb vertically and at the same time accelerate at 0.3 g (3 m/s2) or accelerate in level flight at 1.3 g i.e. to increase speed 450 km/h in 10 seconds. TO ground run was 120 meters in 4 seconds after the release of the brakes. It was supersonic after the next 19 seconds. 18
Cobra Until 1988 Soviet military aircraft were missing at Western airshows, a fact that made room for underestimation. E.g. the notorious spy-airliner interceptor - Su-15, was praised as the interceptor with the best performance by Belenko, the pilot who escaped in the MiG-25. Its predecessors, Su-9 and 11 held the world record for sustained altitude, 1 kilometer more than Phantom and that is an indicator of overall performance. Not to mention figures that MiG-29 did at Farnborough 1988, the loop immediately after takeoff, with leveling off at the top (the most challenging stability and control ‘test’ where high α transitions to β and again to α at top of the loop and the lowest airspeed, the domain where half the Phantoms in Vietnam were lost, the figure that even F-18 does not dare to replicate). It was followed with another loop at the top of the first one – S figure. Or tailslide / 'bell', the vertical climb until running out of speed until the plane starts to go backwards (0g). With forward stick nose was pitched down, retaining throughout the full longitudinal and lateral stability. The aircraft needed 10 times less airspace to complete the figure than the best previous fighters whose behavior was not always predictable! The reason why MiG-29 needed such a small altitude for tailslide was simultaneous AB light-on on both engines (otherwise it would yaw and roll, the aero-surfaces would not be able to compensate at that airspeed). No Western engine would have a satisfactory response under those conditions (GE, PW, RR, MTU, IHI, FIAT). 19
The F-15 does not test odds against mishaps and does tailslide at high altitude, from which an aircraft would have the time to recover from unwanted situations. At the Paris Airshow 1989. the pilot Viktor Pugachev in Su-27 stunned the world audience with a figure that showed a remarkable degree of the aircraft’s pitch agility. In level flight, at about 400 km/h, the pilot suddenly pitched the plane to about 120º (with approximate α) while continuing to fly forward. The whole time there were no signs of rolloff or yawoff. The figure was reminiscent of a cobra that takes momentum before the attack. Before the performance, the Soviets had problems logging a flight program. According to Pugachev, the French had taken the position that they invented aviation and that such a figure should not be performed because it was dangerous. Pugachev showed documentation, convincing them that he had performed the figure a thousand times. Before the show, he had to demonstrate the figure a few times for the organizer. There were similar, poor-man Cobras, demonstrated earlier at high altitudes. For example, the famous pilot-strategist Boyd used to bet with colleagues that within 40 seconds he’d outmaneuver them even if they were at his back. He used to pull stick full back, 'stopping' in the air (probably achieving α of about 50°) and with a rudder rolls managed not to lose the bet. But sometimes the aircraft would be lost, brining him before a Court Martial, where he defended himself by saying that in the Flight Manual nothing said that this should not be done. Other famous performers of a modest 'Cobra' (up to 80°) are Draken and F-14. Many 4th generation fighters have been tested to 90º α but at high altitudes (during Tailslide), where there was enough airspace to restore control, after 20 possible engine flame-out, departure or spin.
Pugachev performed the Cobra in front of audiences every day at an altitude of 300 meters. Needless to say, Su-27 (like the F-22 e.g.) does stall/roll off at about 40º (Mach 0.3) and 33° α (Mach 0.9). The key to the Cobra maneuver are four characteristics of the aircraft: - High pitch agility: A huge so called tailplane 'volume' (relative area and arm), with the help of LEX vortex lift mechanism and longitudinal instability allows dynamic pitch angles and α in excess of 100°. F-14/15/18/M2000 planes cannot reach these angles; - Lateral stability: every plane is to a lesser or greater extent dynamically unstable directionally at α of about 20-40º, where the airflow begins to separate. Su-27 rolls-off here at 40° α. The essence of the Cobra figure is to quickly pass unstable α region (while the large inertia of the aircraft prevents the potential roll/yaw-off) and come into benign region of completely separated air flow; - Longitudinal stability at 100°+ α: because of the high pitch rate, the aircraft passes the point of max trimmed α (that is about 50-60º α), but the tailplane size and deflection pitch aircraft back to the initial α. The author believes that the aircraft was designed with over- dimensioned tailplane (as a backup) because the static longitudinal instability was still unproved. F-16/18 fighters have large LEX compared to tail ‘volume’ so planes have difficulty returning from about 60° α. The pilot of an F-16 needs to move stick in phase with falling leaf - rocking motion of aircraft, trying to get out of the α region where full forward stick does not result in pitch down motion. - Stable engine operation at 100° α / less than 200 km/h IAS (earlier generation turbofans has about 20º α limit); Su-27 set new standards in fighter design and paved the way for super and hyper (up to 120º α) maneuverability (dynamic entrance into supercritical α - flight mode that perm 21 its a decrease of airspace needed for turn by 2 times).
Radar F-15 has always had the most modern radar. The planar antenna, combined with the high and medium-pulse repetition frequency (prf) transmitter gave the Hughes APG-63 radar 10 years advantage over other radars with a mechanical antenna. European radars on Tornado, M2000, and JA-37 Vigen (the latter had a modest Hughes license) had the older type of antenna with inferior sidelobe characteristics - reverse cassegrain, while both high and medium prf (the first provides greater look-down range and the latter is more suitable for the detection tail-on, low-altitude targets) was far away. So Viggen has two times less range while Tornado chases nose-on targets. Neither did the F-14 have medium prf. The French M2000 RDM radar had a low prf, unsuitable for target detection below the horizon. Sukhoi -27 radar N001 has both prf, but because of the technology gap, it kept the reverse cassegrain antenna on previous fighters. Before Su-27 appeared, the F- 15’s radar range data that circulated in the media, was 100 (nautical) miles. When the Sukhoi revealed a figure for their radar - 100 km against fighter sized targets, the USAF confirmed that they had the same range. 22
Electronic warfare F-15 has always had the most advanced and capable automatic active jammer, ALQ-135 (jamming by shortening threat radar range, by emitting ‘noise’ or by deception of own position) that can be stored internally. Its operational status, like of some other systems of the U.S. Military, is often accompanied by criticism that it has serious flaws and therefore limited operational capability (to protect the carrier-aircraft in this case). The GAO (General Accounting Office), was established by the U.S. Congress to prevent 'deception' by Military and big corporations. According to GAO, system ALQ-135 had been purchased although it did not show an acceptable operating performance (they were not published in the media in order not to spoil the mood of the possible opponents for surrender). The Sukhoi jammer - Sorbcia-S is bulkier but uses innovative methods of deception jamming. Located in the containers at the tip of wings, with front and rear wideband phase-steered antennas. For effective noise jamming, a very high transmitter power is required, which only specialized planes have. The second method - deception jamming is not effective against monopulse antennas. But if the jammer antennas are spaced (15 m in Su-27 wingtip case or better if the plane tows jammer on a long wire) the 'cross eye' technique gives good results, especially with phase controllable beams that rationally use available power, as in Sorbcia. It allows simultaneous jamming up to 10 threat radars. 23
Weapons acquire target in the second phase of the flight, when it gets close to 30-40 km. Western missile guidance system improvements Density of missile guidance were evolutionary, based mainly on improving the electronics was always on the West components and the packing density of electronics. side. As it turned out in conflicts (i.e. The launching of AIM-7M missiles at a speed of SAM systems of the '60s and F- Mach 2 would not increase launch distance, just the 117/16), fighters fall down even when limits of target’s max speed and g-load. A large they are hit with missiles with less amount of fuel allows Sukhoi to fly generously at densely packed electronics. It is supersonic speeds providing the missile launch more important to design i.e. speed and kinematic advantage. monopulse antenna seeker for more Regarding speed and altitude, both missiles can accurate guidance and resistance to shoot targets in the SR-71 aircraft class. jamming or to add an inertial subsystem for guidance at ranges where the missile seeker/radar antenna is too small to acquire the target. Missiles AIM-7F / M and R-27R have almost the same max range of about 40 km. However, the R-27R has an advantage when launched at supersonic speeds. In that case, because of the additional inertial mid-guidance phase, it can be launched from 60 km and missile 24 guidance radar seeker can
Turn performance Su-27 has 5-10% advantage in lift limited turns i.e. instantaneous turns at subsonic speeds. As directional stability decreases with Mach number, α limiter of the Su-27 (as in F-16) cuts allowed α and so min airspeed (with 4 AAMs and half fuel) increases from 203 to 230 km/h at M 0.9. This is visible at high altitudes where corner velocity migrates to transonic speeds. The F-15’s FCS does not limit α but buffeting at higher subsonic Mach numbers does. At Mach 0.9, F-15 experiences heavy buffet at above 10º α so it is physically impossible to sustain cited α more than a couple of seconds. At trans/supersonic speeds, structural g- limit advantage is on F-15’s side, but no one will look at the limits during a dogfight. However, as at high altitudes, at trans / supersonioc speeds, turn radius exceeds the target practical visual range limit (about 2000 m) and dogfights do not normally occur here. The situation is similar with the thrust limited (sustained) turns. At subsonic speeds the advantage is on the side of the Su-27, between 0.9 and 1.3 M there are no noticeable differences, and above that, the advantage is on the side of the F-15. The latter is possible thanks to PW220’s digital engine controls, which can more flexibly support supersonic thrust increase within turbine temperature limits. According to the US pilots who flew it, Su-27 has a higher roll rate (max about 270 º/s), something in the F-18 class. To suppress possible departure and spin, analog flight control systems limit aileron / tailplane deflection and so roll rate with α decreases, where 25 at about 30º it is close to zero.
Against each other The author’s intention is not to present anybody’s propaganda nor to be involved in marketing. We’ll just look at the validity of some allegations about the kill ratios mentioned in the media. Regarding the F-15, the reported figure is about 100:0, achieved by US and Israeli AF. Clearly the plane, at least when it appeared, had no competition in combat, up to Mach 2. But circumstances where such combat occured did not always involve an isolated one to one scenario. In close combat, according to Rand studies, with the same generation weapons "all die equally“. At medium ranges, the circumstances are crucial. For example, single Yugoslav AFMiG-29s clashed with a number of F-15s, which had the support of special aircraft for surveillance and jamming E-3B / C, E-8C, EC-130, RC-135, EA- 6B, P-3C, while the bombers and cruise missiles attacked MiG bases and ground radars. The F-15 had only to approach, fire AMRAAMs and immediately withdrew. The number of hours of flight crew training and reality were additional factors. Ethiopian Sukhoi 27 shot down the Eritrean MiG-29, supposedly only because of Russian support. Alleged results of so called simulated combat between Su-27 and F-15 during the Su-27’s visit to U.S. were not serious because the Sukhoi even without afterburner, not exceeding 18 º α, succeeded to outmaneuver F-15. 28
After Vietnam, the U.S. military learned a lesson about the public and the media, and now all information is censored and journalists are not allowed to access war zones uncontrolled. Even Congress has a problem to know the truth in such media management. Long before Wiki-leaks, there were individuals – fighters for truth in war. One of them is the American pilot of B-52, Dana Drenkowski, a decorated Vietnam vet, whose personal life was ruined because of his endeavors. He wrote about the long tradition of concealing losses of US aircraft, from Korea and after. He touches on losses in Operation Linebacker II, in '72, in which he participated. The U.S. Air Force told the media that 17 B-52 planes were shot down, while Congress was presented with a figure of 13 aircraft. He and other pilots personally counted 22 planes (+5 which landed with damage beyond repair). He thought that Vietnamese claims of 25 planes should also be noted. Israeli historian Shlomo Aloni in his works on the '67 war touches on air combat. He writes that IAF/DF’s (Israeli Air Force/Defence Force) two downed Israeli Mirage IIICJ officially attributed to the Syrian air defense, according to Israeli intelligence agency were in fact shot down by the Egyptian pilot Nabil Shoukry flying the MiG-21. Of course, in the so-called “free world” nobody ever heard the Egyptian claims. It is interesting that the same Egyptian pilot, decades after the war, as a general, in the local presentations for Western media, flying the two-seater MiG-21 demonstrated handling and maneuverability at low and 'zero' airspeed. 29
Su-27 in the US Air Force According to U.S. aviation authorities (FAA - Federal Aviation Administration) there were two Su-27s in the United States, privately owned. Using a favorable political situation in Ukraine in 2008, two Su-27 aircraft were sold to the private company Pride Aircraft, Inc. in Illinois, US. The company website claims that the planes are no longer in their possession, that they were sold. Russian news agencies reported that the track leads to U.S. Military. 30
Neither the F-15 nor Su-27 are able to land with both engines-out, because aircraft systems can not support that. During the decades of operational use of F-15 there were opportunities to see the usefulness of the dual flight control system (mecha-hydraulic and electro-hydraulic [CAS]) for some aero-surfaces. The Israeli Air force F-15 in simulated close combat with a light subsonic A-4 attack aircraft of the '50s, collided with one another after which the F-15 lost one wing. The plane fell into a spiral and the pilot was not immediately aware of damage. He switched to the electrical FCS because the horizontal tail controls for rolling uses electro-hydraulics and established control. He considered whether to leave the plane and yet no warning light that something is wrong was blinking. He managed to land safely at about 400 km/h. F-15 has max lift (minimum speed) at about 35° α. Above 20° wings are stalled and fuselage carries the plane. The advantage of F-15’s early appearance, has now turned into a handicap because the average age of operational aircraft is now 25 years. 31
TECHNICAL DATA* F-15C (PW-220) Su-27SK First Flight (initial model) 1972. (F-15A) 1977./1981. Operational from 1976. (F-15A) 1985. (1990.) Length overall, without pitot-tube, m 19,4 21,9 Wing span, m 13,05 14,7 (14,95 w tip R-73) Wing area, m2 56,5 62 Wing aspect ratio 3 3,5 Height, m 5,63 5,93 Tail span, m 8,74 9,8 Weight empty equipped, kg 13400 17200 Fuel internal, kg 6100 (ρ=0,78) 9220-9400 (ρ=0,785) Fuel external, kg 3 x 1800 kg - Take-off Weight, 4 AAM, 100% int. fuel 20675 kg 27390 kg Max external payload, kg 6 - 8000 6000 Combat weight with 50 % fuel, 4 AAM, kg 17625 22780 Thrust/Combat weight ratio 1,21 1,1 Max. Take-off Weight, kg 30850 28-33000 =f (wheels) 2 x F100-PW-220 2 x AL-31F Engine 33 6,52-10,64 t 7,77-12,5 t
TECHNICAL DATA (cont) * F-15C (PW220) Su-27SK Range (internal fuel), km 2200 3700 Range (with external fuel), km 4000 - Limit airspeed / Mach in dive 1470 km/h IAS / 2,5 M 1400 km/h IAS / 2,35M Combat ceiling, 4 AAM, m 17100 18000 Max level speed at SL, clean config, Mach 1,15 1,12 Max level speed, clean config, Mach 2,4 (2,2 PW100 engine) 2,15 Min airspeed, 1/2 fuel, 4 AAM, SL, km/h 230 203 Max rate of climb, ‘’ ‘’ SL, m/s 300 290 Max instantaneous turn rate, SL, º/s 26,4 (9g) SL 28,0 (8,0g) SL corresponding inst. turn radius, m 415 330 Max sustained ‘g’ in turn, altitude (H)=5km 6,65 6,67 Max sustained ω in turn, H=SL, º/s 19 (9g) 19,4 (8,0g) Min sustained turn radius, H=SL, m 450 at 370 km/h, (2,6g) 355 at 350 km/h, (2,9g) Acceleration 600-1100 km/h, Combat w, SL 14,5 sec 15 sec Acceleration 1100-1300 km/h, Comb. w, SL 11,5 sec 12 sec 34
TECHNICAL DATA (cont) * F-15C (PW220) Su-27SK Limit g-load (subsonic) 9,0 at 17,0 tonnes (M<1) 8,0 at 21,4 t. (M<0,85) “” 9,0 at 19 t. (M<0,85) Take-off speed, km/h 265 at 20,7 tonnes 290 at 27,4 tonnes Take-off ground run, m 380 at 20,7 tonnes 650 at 27,4 tonnes Landing run, m 1300 620 with chute Internal armament 1/6 x 20 mm 1 x 30 mm External AA armament 8 AAMs 10 AAMs Number built 1200 680 Price 1998 year, m$ 30 30 * All data are official or computationally derived from official sources * Comparison F-15/Su-27 is done with a proportionally lighter F-15 (relatively less fuel to a/c weight) and with less missile drag (only AIM-7 with conformal method of carriage) w/o MRM/SRM combination as in Su-27 Similar, more comprehensive title (at email@example.com): Fighter Performance in Practice: Phantom versus MiG-21: How to do split-S in Mig-21 within 3000 ft: Unexploited low speed maneuverability 35