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Described as an aerodynamic miracle by some, and a masterpiece by others, the Sukhoi Su-27 (Сухой Су-27) Series (NATO name: Flanker) has evolved into one of the finest achievements in modern aviation - of any nation.
Su-35S of the Russian Air Force |
Below is Su-30
It should be noted that “departing the aircraft” has historically at times - been a necessity - to survive an engagement. Both U.S. and Russian engineers have largely supplanted this capability in exchange for ‘Super maneuverability’ (inherently unstable airfoils needing computerized flight-control fly-by-wire systems) that may no longer allow traditional departing? However, both this Su-35S and Su-30 [above] appear to have retained this essential capability.
Su-30SM of the Russian Air Force |
[Below] The Su-35S in 2012. Pay close attention to the superb energy recovery (and short distance flown) from a hard starboard turn into a simply impossible nose-pointing maneuver (starting at playback point 3:22 to 3:46 ). Note the engine-louver actuation on each engine nacelle at playback point 6:22.
[Below] Many in the Western defense establishment claim that Flanker cannot maneuver properly with a full weapons load - and why it is never shown doing so. That a weapons load makes Flanker not only too heavy but produces too much drag. [Below] This is yet another false Western assertion that is easily challenged simply by locating applicable footage. The flanker is so large that weapons loads have little impact. Watch this Su-27M:
And here this Su-30MK:
The Sukhoi Su-27 is a non-stealth design developed during the last years of the USSR by Sukhoi Design Bureau Chief Designer, Mikhail Simonov (prototype T-10S). At the time the Russians needed to counter both high-flying reconnaissance aircraft like SR-71 and the low-level penetration types like the F-111, FB-111, Panavia Tornado, cruise missiles, as well as the Rockwell B1. It also needed enormous range to cover the vast expanses of Soviet airspace of some 11 time zones, and together with the MiG-31 Foxhound, to replace the Sukhoi Su-15, Yakovlev Yak-28, and Tupolev Tu-28/128 series of interceptors.
The f-15-like model at the far right was used as a test baseline.
The other requirement was it needed to be significantly superior to the superb new 'super fighters' being fielded by NATO, including the Grumman F-14 Tomcat, McDonnell Douglas F-15 Eagle, General Dynamics F-16, and later, the Northrop-McDonnell Douglas F-18 Hornet.It must be said that developing an aircraft to counter the Grumman F-14 Tomcat, and its AWG-9 and AIM-54 Phoenix missile system - remained 'not a simple matter.'
Development started in 1970, and the first T-10-1 prototype did not fly until 20 May 1977. The test program was very difficult, and after a fatal crash on 7 May 1978, Mikhail Simonov was brought in by Sukhoi to design a whole new aircraft.
According to Mikhail, the only parts his new T-10S inherited from T-10 predecessors were landing-gear wheels and ejection seat. It was a total redesign. T-10S-1 made its maiden flight on 20 April 1981. Development problems persisted resulting in a second fatal crash on 23 December 1981.
Without going into a lengthy design analysis, the Flanker bears striking similarities in layout to both the American Grumman F-14 Tomcat and the General Dynamics F-16, seemingly a blend of these two concepts.
How much the design was influenced by the F-14 is a subject of debate in some defense circles. The Russian 'Tsentralniy Aerogidrodinamicheskiy Institut' (TsAGI) Central Aerohydrodynamic Institute also played a key development role. There is no evidence, however, to support - as many suggest - that the Soviets flight-tested F-14A-GR Tomcats from Iran after the Iranian Revolution of 1979.The Flanker is big (roughly 30% larger than the F-15 Eagle) and only makes Flanker agility for a 20+ ton aircraft - even more astonishing.
The Flanker not only uses a statically unstable roll axis (pioneered in the American F-16) but also a statically unstable pitch axis, using fly-by-wire flight control systems to compensate. Later variants of Flanker have effectively no AOA limits.
The Su-27 Flanker uses two Saturn/Lyulka AL-31 class turbofans, rated at ~122.8 kN (27,600 lbs), and has tremendous tolerance to severely disturbed air flows. Fitted at the bottom of each engine nacelle near the intakes is a clever louver system that assists engine gas flow - even if the aircraft flies tail-forward. The AL-31FP and AL-37FU variants have thrust vectoring (this included independent, fully-articulating 3D-asymmetric thrust-vectoring engine nozzles).
[Below] Flanker "P-42" was specially prepared (as was the American 'Streak Eagle') to perform time-to-climb flights.
Flanker 'P-42' has also taken over two dozen time-to-climb records away from the American F-15 Eagle. The Flanker's range is ~ 4,000 km (~ 2,480 miles) without external fuel tanks - this un-refueled range has no Western equivalent.
New upgraded engines should propel Flanker through Mach-1 into “supercruise’ at non-afterburner (non-reheat) power settings. This gives Flanker even greater combat persistence - and allows Flanker to remain at the top of the air-combat fighter tree, a tree that includes the American F-22A.
The Flanker will always be associated with the Pugachev Cobra Maneuver: a post-stall maneuver named after Sukhoi test pilot Viktor Pugachev, who first performed the maneuver officially in 1989 at the Paris Le Bourget air show. Many described seeing the Cobra for the first time as a religious experience.
It’s important to remember that Air Combat Maneuvering (ACM) training has always taught that nose-pointing is critical: “the guy that points his nose at the other guy first - wins.” Highly maneuverable aircraft are also better at defeating an opponent's missile shot.
The super-maneuverability demonstrated by Sukhoi without (without) thrust vectoring, was a concern in the West. The Americans and Europeans responded in the mid-90s with several super-maneuverability test programs that were to incorporate thrust vectoring and nose pointing. Below are two of these: the American NASA ‘MATV’ F-16 with a somewhat subtle (but nonetheless pronounced) altitude gain of the MATV F-16 during a 'Cobra' maneuver.
The second was the X-31 [below], a collaboration between Rockwell/Messerschmitt-Bölkow-Blohm. After listening to the narration, imagine what would have happened to Western air forces had war broken out against Flankers equipped with ultra off-boresight helmet-sighting.
Since its initial deployment, the Flanker has gone through a seemingly endless array of improvements and refinements. To date, Professor V.K. Grishin, the chief designer of Zalson S-800 passive phased array radar on MiG-31, has also focused attention on Flanker sets.
An infrared search and track (IRST) system is fitted which also incorporates a laser rangefinder. This system is nearly identical in concept to the Grumman F-14 Tomcat, in that it can slave (can point) its radar at what IRST 'sees' or can slave IRST to what the radar sees. The Sukhoi IRST system incorporates a unique twist, in that its IRST controls the cannon, providing greater accuracy than radar gun-sighting can.The most significant evolution of the air-to-air Flanker was designated Su-27M (possibly a derivative of the Su-33). Externally looking similar to other types in the series but in reality, was an entirely new airframe using advanced systems, radar, including DFRM wingtip pods, and a new rear chute stinger' housing that may incorporate some type of rearward "targeting device." This feature would allow Su-27M to fire a missile and then turn and fly away from the target while continuing to illuminate and provide datalink during the SARH/ARH missile shot.
[Above/Below] Su-27M was designated Su-35 for a period of time. This series of aircraft leapfrogged other Flanker derivatives and acted as a modernization/development vehicle for Flankers to follow. These machines can carry two (2) (some documentation states three) special ultra-long-range “anti-AWACS” [anti-radiation] class weapons to attack all manner of high-value AWACS / AEW / ISR / J-STARS / 'Rivet-Joint' platforms, tankers, reconnaissance, and electronic warfare aircraft. Simply the threat of these weapons in theater - fundamentally alters any ‘Power Projection’ doctrine.
One of the few Western documentary reports the author could locate on thrust vectoring and Flanker [American narration]:
The Flankers superb abilities did not go unnoticed by American military brass. Indeed, a proposal was floated in US Navy circles by retired USN Admiral (Rear Admiral Paul Gilchrist), that the US Navy acquire the Su-33 and equip them with US avionics and engines. [Click or tap picture below to enlarge].
US-Navy interest in the Su-33 should not be dismissed. The Su-33 folded width is smaller than the American F/A-18 Hornet and even an A-4 Skyhawk! Remarkable.
In 1997 the US acquired from Ukraine, two Su-27UBs (export variant) aircraft for evaluation and testing, under civilian registration. Recently, a Su-27P (Flanker-B) was photographed at Groom Lake "Area 51" in Nevada conducting dissimilar ACM with an F-16. The single-seat Su-27P is likely from Belarus.
It matters little, the American aircraft is totally outclassed. A climbing combat turn by the Su-27 is all that is required - and it's all over.
As of 2005, Sukhoi has reportedly made over ten thousand (10,000) changes to the Flanker series, to counter any technologies that could have been compromised as a result of the breakup of the Soviet Union.
The Flanker is going to be with us for quite a while. Its airframe has tremendous growth potential. Its large size allows for extreme high-power (and high cooling capacity) electronic offensive/defensive systems. New radar(s) have apparently been incorporated-embedded in the leading edges of the (Su-35S?) wings. This should ensure DoD / USAF / US-Navy planners plenty of restless nights well into the future.
F-22 proponents continue to assert the Raptor is superior - but do not produce any proof or empirical evidence to back up their claims. Certainly, air show demonstrations have not produced vastly superior low-speed maneuvering and a claimed turn rate of 28 degrees per second is never qualified or been shown to the public? - nor useful against a helmet Archer" class weapon. We have simply tired of wild American hyperbole.
[Below] The US Navy isn't taking any chances. An F-18 from VCF-12 'aggressor' in "Flanker Splinter" Su-35S camouflage including Russian red stars. Aggressor instructors will privately tell you that properly flown, the Flanker is exceedingly dangerous. Western aircraft literally cannot perform the same maneuvers as the Sukhoi - so even the best training - is only an approximation. Nevertheless, ACM training is essential.
Since the Russian intervention in Syria, several Russian paint schemes have been observed and adopted.
The best English language documentary author could locate on the development of the Flanker series aircraft.
When American fighter pilots we’ve spoken with, are casually asked about Flanker, the reply has been nearly universal: “That thing is a nightmare.”
With its large nose and radar angular-resolution potential, IRST assist, weapon load-out without carriage restrictions, helmet sighting, low-speed maneuvering, new wing radars, and unmatched unrefueled combat range - in the hands of a skilled pilot, the Sukhoi Flanker must be regarded as beyond-formidable, even in the presence of Stealth.
Had the Americans built such a machine – (which they could, but embraced Stealth instead) - the world would never have heard the end of it - it would have been paraded around the globe as the greatest triumph in aviation history.
[Be advised that Google has deleted this original writing dated 2009 - scholarship purposes require the original publish date to be retained. Original publish date can be derived by the comments section time-stamp(s)]
Your thoughts?
- All media found here is for scholarship and research purposes and protected under U.S. Internet ‘Fair Use’ Law -
F-22 proponents continue to assert the Raptor is superior - but do not produce any proof or empirical evidence to back up their claims. Certainly, air show demonstrations have not produced vastly superior low-speed maneuvering and a claimed turn rate of 28 degrees per second is never qualified or been shown to the public? - nor useful against a helmet Archer" class weapon. We have simply tired of wild American hyperbole.
[Below] The US Navy isn't taking any chances. An F-18 from VCF-12 'aggressor' in "Flanker Splinter" Su-35S camouflage including Russian red stars. Aggressor instructors will privately tell you that properly flown, the Flanker is exceedingly dangerous. Western aircraft literally cannot perform the same maneuvers as the Sukhoi - so even the best training - is only an approximation. Nevertheless, ACM training is essential.
Since the Russian intervention in Syria, several Russian paint schemes have been observed and adopted.
Part 7: Pay close attention to the Eurofighter Typhoon test pilot (John Turner) critique of the Cobra maneuver. We would remind Mr. Turner of 1) The brutal realities of the Boyd-Energy fight and 2) that later RAF Typhoons were indeed outflown by IAF Indian MKi Flankers during 2009 Indra Dhanush Exercises. The Cobra is (and always has been) simply another tool in the toolbox of Flankers larger-overall air-combat maneuvering abilities.
With its large nose and radar angular-resolution potential, IRST assist, weapon load-out without carriage restrictions, helmet sighting, low-speed maneuvering, new wing radars, and unmatched unrefueled combat range - in the hands of a skilled pilot, the Sukhoi Flanker must be regarded as beyond-formidable, even in the presence of Stealth.
Photo: Knaapo |
[Below] Russian Air Force Su-35S in Syria, February 2016. Note the aircraft carries both the R-77 ARH (Active Radar Homing) and R-27 infrared-homing (R-27T) medium-range missile rounds. If the Su-35S can also carry the semi-active-radar-homing (R-27R), and active-radar-homing (R-27EA) versions, then together with the R-77 (and R-73/74 series), a single Su-35S can introduce an array of threat-guidance types into a BVR/WVR fight that could cause big problems for opposing aircrews to counter? Potentially akin to a single F-15C carrying AIM-120, AIM-7, and AIM-9 rounds at the same time.
[Be advised that Google has deleted this original writing dated 2009 - scholarship purposes require the original publish date to be retained. Original publish date can be derived by the comments section time-stamp(s)]
Your thoughts?
- All media found here is for scholarship and research purposes and protected under U.S. Internet ‘Fair Use’ Law -
Comments
Nose authority is the key.
ReplyDeleteEvery plane with nose authority at 100 Kts can deal with a Su-27.
When doing its "things", the Su-27 is a sort of static point in the sky...easy to target.
(impressive plane anyway)
syntaxerror9
Well when the Su-27 is actually doing its "things" it is most likely in a dogfight, where timelines are extremely compressed. So even when it is a sort of static point in the sky the plane chasing it suddenly finds itself in front of the Su-27. While at altitude around 35000-45000 ft the IR sensing fighter has the advantage (generally speaking) so the F-15, F/A-18, F/A-22 cannot put out any countermeasures that will fool an IR gunsight; especially the F/A-22 since it puts out the same IR signature as an SR-71. Throwing a flare is not going to be that helpful
Delete-Cameron
Was my asessment fairly accurate?
DeleteModern day missiles do not care how agile a plane is, because the missiles are far more capable in turning. Having a super maneuverable plane doesnt matter much anymore. Which is why the US invented stealth. The F-22 is a long range hidden sniper, its sole purpose is to shoot down enemies and they never even know. You can not dog fight what you dont know is there and first shot is first kill in these modern times. The F-22 does not put out the same IR signature as the SR-71 either. It is very minimal and far less than most every other aircraft
DeleteAn ultra maneuverable fighter will always be a necessity. They even built super maneuverability into the F-22A (w/thrust vectoring). Your missile could have a mechanical failure, a motor failure, some other problem, be jammed, confused by DRFM or by expendables. There are a million reasons why you must retain super maneuverable fighters. But mostly - it’s a necessity for all the reasons one can’t thing of.
DeleteIf you read our post: Airborne Infrared and Supersonic Stealth:
http://theboresight.blogspot.com/2009/07/airborne-infrared-and-supersonic.html
The entire high-altitude/high-speed F-22A tactical usage model starts to have problems. F-22 requires this high/high arena to retain “first shoot.” Not only that - but F-22 has two hot spots on either side of the nose that will be more pronounced to a modern IRST at ultra freezing -40F, -50F, -60F, -70F degrees below zero altitudes.
- Boresight
“Which is why the US invented stealth”... http://en.wikipedia.org/wiki/Petr_Ufimtsev
DeleteAn early hard turn can cause long/medium range missiles on lead pursuit to make a huge detour, wasting a big chunk of their energy. Without energy a missile can't perform hard maneuvers or might even fall short.
DeleteIt's called "fire and forget" because you don't have to care about the missile after launch (in contrast to SARH), not because it's a 99% kill probability.
Russia (just like the US) uses data modems to share sensor information between different units, including ground radar (GCI). Combine all possible sensors (IR, Radar, passive emission detection ...) and think how big your chances are to be undetected until you are in firing range. We're not talking about obsolete radar equipment from Desert Storm, we're talking modern equipment designed to defeat stealth.
When pakistanni pilots were given chance to fly Chinese Su-27 we were greatly astonished by their agility as compared to F-16; but the point is at what expense...
ReplyDeleteWe have seen in Syria-Irael conflict that major ranking planes suffered end-game at the hands of Russian SAMs or in general missiles. So what I want to say a TVC equipped long-range AAMs the likes of Adder & or Meteor missile will play havoc with all ~super-manoeuvrable warplanes (simply because missile can pull out 5times more G's than planes) so the only option NOW is to 'deceive' them via stealth & ECM's ...we have to accept we can't 'out-run' them.
regards;;
SeerSucker,
ReplyDeleteA Stealth fighter (fighter) has a completely different set of problems it must resolve - to conduct its primary mission. Please see our: “Supersonic Radio-Spectrum Airfoils”
A supercruising stealth-fighter cannot alter the (same) laws of physics it uses to fly – and therefore not immune from thermodynamics: Please see: “Airborne Infrared and Supersonic Stealth”
Then there is the problem of radar. Please see: “Phased Array Radar and Flying Insects?”
Finally, good RWR gear (and DRFM), plus good heads-up flying can spell big trouble for a radio-spectrum-only weapon system. Please see “The Future of Air Combat?”
- The Boresight
Hello,
ReplyDeleteCorrect me if I'm wrong but the SU27 has no canards but the later models such as SU37 does. I think a number of the photos are SU37s referred to as SU27. Not really that important but I thought it might be worth mentioning.
The truth is, The American Military was caught with its pants down and is now trying to make up for their failure to recognize the "real time" threats and requirements that would usually drive the design of our fighters. Instead we are left with brass that are selling us on these overly priced stealth platform that have little increase in performance over our 4th generation fighters. We are well into the 5th gen fighter program and we have lost a long range air to air capability, how is this progress?
ReplyDeleteHello Boresight,
ReplyDeleteI believe I might know something with regards to the idea of the Flanker's unique design.
http://en.wikipedia.org/wiki/Fuselage
Please note Figure 4 in the "Types of Structures" section.
Yes this is wikipedia, but nothing else seems to consider the corresponding shapes with a certain optimal performance.
In contrast the U.S. has been building fighters that more closely follow types 2 and traits of type 6 (possibly present on the F/A-22) which are supersonic and hypersonic respectively. The only fighter that does fall under in those 2 categories is the F-14. In fact the F-14 appears closely related to the Flanker but still distinct from the Flanker. The other traits of the Flanker that are not uniquely its own are the principle location of the nose, and the 'strakes' or leading edge extensions from the F-16. The Flanker emphasizes the the downward orientation of the nose from the F-16 while the midsections resemble that of the F-14, but still distinct again as the engine nacelles are closer together and that the aft of the aircraft ends in a pointed radome of a tail warning radar. I don't see the Russians copying vertical stabilizer designs from anyone.
So in all, the Russians recognized the best accessible flight regime for manned fighters and designed accordingly. Right where the gap can be closed before the "100% success BVR policy" can take effect (we all know that it is in fact 50-50).
So with the inclusion of a full-spectrum air to ground arsenal (previously not very accessible to earlier Flankers) Su-35S-es can now carry 1 BVR salvo (a radar guided and an IR, as it is current Russian doctrine to fire 2 at a time), 2 WVR salvos + 30 ml cannon (accurate up to around 1.8 km, 3-5 shots to kill) with 150 rounds, and then carry air to ground munitions of great diversity(I know what the Su-34 is as well as its role, with that said a 34 would be escorted by 35s in full AA configuration to to make things as difficult as possible).
Sukhoi, as a a result, is fighting from the high ground as a result of recognizing the target flight regimes where modern air combat will occur. High ground in a tactical sense refers to the design of the Flanker's fuselage and airframe, and in a strategic sense the carrying capacity of the Flanker and hence its growth potential.
As for the miraculous miscorrelations between the model and life-size aircraft, that is something that occurs entirely by accident(and is a whole other ball of wax). Nonetheless, Pavel Sukhoi saw something brilliant and Mikhail Simonov followed through.
They were inspired, not funded. As a result, the plane has great performance for less than that of its funded counterparts.
-Cameron
Hi Cameron,
ReplyDeleteWhat we can say is Flanker uses a lifting body with engines and pilot-station in nacelles 'pods' like F-14 (with the engine spaced apart) and a very low wing loading, but unlike F-14, Flanker is an inherently unstable design in both roll and pitch axis. It appears the natural inclination of Flanker airfoil (without digital flight controls) is to flip over on its back and enter a flat spin.
The F-14A also had canards in a sense (deployable glove vanes) for extra lift at higher speed and for control authority (as the vanes unload the tailplanes at higher Mach numbers) for F-14 to pull 7.5 g at Mach 2+.
We find it interesting that a fighter design meant to outfly/outfight the F-15 Eagle - looks well...more like an F-14. The Flanker airframe is also very light weight. Also don't forget the Central Aerohydrodynamic Institute (TsAGI) folks.
Some have suggested the F-22 appears to use a NACA 6-series airfoil. A bit odd that Lockheed would have chosen a shape dating from the 1940s rather than designing a new shape better tailored to the specific performance requirements. But that takes R/D $$.
The NACA 6-series was designed for low-drag at transonic speeds, where the F-22 will spend most of its time, and it therefore makes sense that Lockheed would have chosen this sort of shape for the aircraft.
On the J-20 you asked “What good would it be to position a missile in the airflow before launch?”
IR missiles work better when their seeker heads “see” the target before launch. Yet another drawback of stealth fighters. Actually dogfight missile don’t work at all if your missile doesn’t see the target before launch.
Might as well be launching bottle rockets...
- Boresight
Ok...
DeleteI thought I was onto something
Hi Boresight,
DeleteHaving internal missiles is definitely not a drawback.
Modern IR missiles (developed in the last 10 to 15 years) do not necessarily work better when their seekers are locked on to the target before launch. These missiles incorporate LOBL and LOAL modes of operation. In LOAL mode the missile may be queued by radar and/or any optronic sensor (IRST, helmet sight etc.). The F-22 only employs the former and thus need to have the target in its radar’s zone of illumination (could be a drawback when you face an opponent with a helmet mounted queuing system). The track rate of some of these missiles is in excess of 100 degrees/s making high off-boresight angle scenarios a deadly killing ground.
A major drawback having missiles in the air stream is that they get heated aerodynamically and soak to above 100 degree Celsius internally. When moving to contact the pilot will be dashing with the missile in LOBL mode to get the seeker to lock on to the prospective target. In LOBL the missile will be generating a lot of additional heat due to digital hardware dissipating heat due to being switched on.
If the missile’s internal temperature rises above a certain limit the pilot can’t fire the weapon because there is no thermal headroom for the weapon to get to its intended destination, the targeted aircraft.
For example let say the missile is soaked at 105 degrees Celsius, and the internal temperature will rise 2 degrees per 1 km of flight, therefore the seeker will sit at 125 degrees Celsius after 10 km. I can guarantee you the seeker will definitely fail. Doctrine for any missile will dictate to the pilot the maximum time allowed to dash before he can’t fire his missiles. In my view this is a major advantage to platforms like the F-22 which is able to carry missiles internally against say the Eurofighter Typhoon or Sukhoi Su-27. BAE claims super cruise with a missile load for Typhoon. This is major BS. I can guarantee you all the missiles will be next to useless once the Typhoon enters the combat zone. They will be so overheated the pilot won’t be able to switch on any of them.
Another huge advantage of carrying missiles internally vs. externally is the impact of drag from the weapons load on fuel consumption. How long will the Typhoon be able to loiter vs. the F-22 after super cruising to the theatre of operation with a full weapons load, my guess is not more than 5 minutes, maybe 10 minutes max.
A lot of detail escapes most of the public due to a lack of exposure to the defence/military environment but it is these sort of engineering detail that make the F-22 a superior fighter aircraft in spite of all its shortcomings (and this is just two examples that I can think of out of many).
Regards,
Joe
Hi Joe,
DeleteWe agree that high off-boresight helmet-sighting has become a game changer in both LOBL and LOAL modes. Heat soak of an IR weapon would be more pronounced if the aircraft is flying a sustained mach 1 +. While we are not here to defend Eurofighter Typhoon usage model - you raise an interesting argument.
Indeed we assume the USAF intends to use the F-22A 6x primary weapons (short-finned AIM-120C) as the main ‘kinematic kill’ weapon – not its 2x short-range AIM-9?
Assuming one did - when an IR missile is released it quickly accelerates to (launch platform speed plus) ~ Mach 2+, so it must be designed to operate under austere rapid heating conditions regardless? Flanker at 450-550 knots just isn’t going to heat its R73/74s to militarily problematic temperatures?
Remember the MiG-25P, PD, PDS used two massive R-40T (IR homing) weapons that could be employed after sustained high Mach numbers against very high speed extreme high altitude targets. So the Russians are well versed in IR weapon thermodynamics.
There is no reason for Flankers to sustain a near Mach 1 approach to the merge. They would slow down after BVR releases - to get ready to maneuver.
It seems to us that missile electronic heating would actually be more pronounced inside a weapons bay? Our suspension is F-22A will require special versions of AIM-120 and AIM-9 to deal with the lack of air stream cooling at speeds below say Mach 1.1, 1.2? Having said that, F-22A high-speed high-altitude operational area will see surrounding air temperatures of say -30F, -50F, -70F below zero. [Note* this is a very bad place to try to stay stealthy against high-flying IR and IRST systems at ~ 40,000ft conducting a line abreast fighter sweep, racetrack loitering, or high value asset protection.]
We still believe LOBL is preferable to LOAL. Especially in a dogfight where friendly aircraft could potentially in the direction/vicinity of your indented target, a friendly hollering “get him off me!” Indeed Flanker uses laser rangefinder for gun aiming.
The impact of drag from the weapons load on fuel consumption is mitigated on an aircraft are large as Flanker. We can’t speak to Typhoon.
Good stuff Joe! Thank you for writing!
- Boresight
With regards to missile electronic heating inside a weapons bay, fighter aircraft avionics are specified and qualified to operate at a maximum temperature of 70 degrees Celsius. So I sincerely doubt the assumption that heating would be pronounced inside any weapons bay, the physics just doesn’t make sense.
DeleteOne of the reason militaries pushed for LOAL capability in IR and radar missiles were to gain a distinct advantage over adversaries employing LOBL technology. LOAL mitigates the necessity to gain situational supremacy in a dogfight in order to obtain a missile lock providing the pilot with a lot more headroom to engage a contact. Point in case is the first Iraq war; please correct me if I’m wrong. The US air force scored only 7 or so kills with IR missiles, the rest was done with BVR missiles in LOAL mode.
From my own experience with 6DOF simulations on LOAL scenarios, I can attest to the veracity of this capability. Consider the following scenario, a head on engagement within visual range starting out at close to 10 km without any aircraft having a distinct kinematic advantage. Exceptional IR seekers do anything from 5 km to 7 km head-on (old tech is at 3 km maximum). This allows the pilot with a LOAL system to engage an enemy aircraft at the start of the engagement. To engage your enemy at 10 km in this scenario is a major advantage in my view. In your view, who has the advantage in this scenario? You can work out the timeline, the pilot with the LOBL only capability will be dead before he can even fire his missile.
Another “surprise” scenario that might be worth your while to consider: that of the pilot queuing the missile on a fast approaching target, launching the missile after the enemy aircraft has passed, the missile then doing a 180 degrees in less than 2 seconds, locking on to the enemy fighter, accelerating to Mach 2.5, and shortly thereafter downing the enemy aircraft. Even if you do LOBL in this scenario you will be right back to LOAL as soon as the target aircraft moves out of the missile’s field of view.
I need to clarify one point; I am not arguing against LOBL. How does the old adage goes, if the shoe fits wear it? If you end up in a situation where you need to do LOBL you do LOBL no sweat. But to argue that LOBL does great in all WVR engagement scenarios or to hold on to the believe that LOBL is preferable to LOAL is ignoring the realities of modern air warfare. The Russians certainly don’t.
Regards,
Joe
With regards to the R-40T missiles (for the IR variant of the missile that is), I will bet you my last bottom dollar that they are transistorized reticule seekers able to withstand extreme temperatures with low power dissipation. This should be able to give you an idea of the capability afforded by the R-40T; a system severely limited by its kill probability. If you think comparable American technology was any better, think again. These missiles (R-40T) were in any case designed with LOAL capability. The MIG-25/31 was not designed as a dogfighter but interceptor, to hold and maintain the kinematic high ground with LOAL capability against supersonic bombers (the primary reason that Russia decided to develop LOAL capability). Missile heating at high altitudes are less pronounced than at lower altitudes. This takes us to your flanker scenario.
DeleteIt’s up to the flanker pilot to manage his weapon system, so this depends. If the missiles’ seeker has been scanning for more than 10 minutes yes, otherwise no. BTW the R-73 was one of the first high off boresight missiles in its class with LOAL capability. This prompted the west to developed modern missiles available today, including the AIM-9X.
I’m not here to defend the Typhoon usage model either, but what would you prefer? American pilots in a Eurofighter type aircraft or F-15 up against a modern flanker or even worse a T-50? You are back to the usage model you claim you’re not defending (I might be jumping to conclusions here so you might want to clarify your stand point to correct my ignorance).
The F-22 can sustain Mach 1+ at low altitude without its missiles overheating; this allows it to operate in an envelope that no other current fighter aircraft can operate in. This is called surpetition, not competition. Advantage F-22, period.
If you don’t have the F-22, what do you have?
Joe
Just one last comment, at low altitudes the air stream is actually the primary source that heats up missiles, even at speeds as low as 250 m/s. This is due to a process called friction, and is known as aerodynamic heating. This is also why modern IR missiles can lock onto fighter aircraft in the head on scenario at low altitude. The IR signature of the aircraft’s exhaust plumes is not even visible.
DeleteI have been working in the aerospace industry (outside of the US I might add) for more than 20 years on various air to air and surface to air missiles as well as avionics for various fighter aircraft. Would like to know a bit more about your background Boresight?
Regards,
Joe
Hi Joe,
DeleteWe know the F-22A had AIM-120 issues a few years back when its primary weapons were subjected to weapon bay environment too long during flight. Some type of bay harmonics or other problem scrambled the AIM-120 “brains” – and the weapons were not functioning properly. USAF was pretty tight lipped about the issue – and god knows if the problem is actually resolved.
The F-22 articulates its AIM-9 out into the airstreams before firing – I assume to allow the seeker head to be able to ‘see’ the target – and for some cooling after the weapon is activated.
I don’t have the Gulf War IR vs SARH kill ratios is front of me, but the AIM-7M performed very well in 1991. The AIM-9M – in 1991 - not so much - compared to the AIM-9L/P in the Falklands and Middle East in 1982. In other words AIM-9 performance in 1982 would not (not) be repeated 10 years later in 1991. Most 1991 kills were (with multiple friendlies) using repeated alternate firings of AIM-7 and AIM-9 at the same target (so from the same range as well). So it was all about overwhelming the targets defensives abilities. Allied F-15 exhausted a large portion of their missile load on a single target. It’s actually fairly shocking how many weapons were fired.
Remember under actual combat conditions weapon hit probabilities (for all weapons fired by both sides) will not exceed 50% - for all reasons.
LOAL utility is actually quite limited – and can only be used under advantages/aggressive rules of engagement or air tasking orders – so it is the exception and not the rule.
Yes the Russian have LOAL capability as well.
Good stuff Joe!
Thanks!
- Boresight
Yes but missile frictional heating on MiG-25 and MiG-31 during supersonic intercepts when the MiGs pushed through Mach 2 - is very high. During operational Foxbat and Foxhound intercepts of the SR-71 over the Baltic during the late 1980s – MiG skin and canopy temperatures exceed 1400F!!! The R-40T were still functional and able to be fired because both MiG-25 and MiG-31 used only their IRST to target Blackbird (who herself was heat soaked) from as far as 60 miles away (on MiG-31) - so as not to reveal sensitive radar signals to RC-135 ‘Rivet Joint’ nearby supporting SR-71 operations. RC-135s were there to collect just such signals. So the MiGs just used their IR channel.
DeleteThere is no doubt that both the MiG-25 and the MiG-31 put an end to SR-71 escapades along Russian airspace over the Baltic.
[Foxbat PD, PDS would almost always rollout behind and just below the SR-71 (the Blackbird flying at speed and at altitude) at a range of just less than 2 miles. Sounds like a perfect setup for an RD-40T shot.]
Regarding the Flanker scenario – the Typhoons best bet is to try and shoot Flankers at long range (to avoid the merge) with its Meteor missiles. But Typhoon is a short range aircraft (must operate with external drop tanks) so god knows how useful it will actually be?
If we didn’t buy the F-22A we’d have a lot more money for more F-16s and other things. The Raptor is just too expensive. It’s not $200/300 million dollars ‘better’ than F-15, F-16, Typhoon, or Flanker?
True IR signature of the aircraft’s exhaust plumes is not visible head on – but if F-22A wants to zoom around the stratosphere it might be visible from below for an IRST looking up.
It doesn’t matter because F-22A has 2x heated pitot-tubes coming off either side of its nose – and at -30F, -50F, -70F below zero it’s going to be seen by modern IRSTs at militarily useful ranges – from Raptors frontal aspect.
No the T-50 is not a “stealth” fighter. I don’t know what it is. Maybe just a development vehicle for other things they want to learn. I’m not sure. T-50 has worse visibility for the pilot than Flanker.
I have over 20 years in embedded software design and test.
Good stuff Joe!
Thanks!
- Boresight
Hi Boresight,
DeleteThe problem with the F-22 is definitely not its cost. The Typhoon is just as expensive as the F-22 no matter which way you go about calculating the cost. Interesting take on this is (you have probably seen this already): http://www.theregister.co.uk/2011/03/03/eurofighter_nao_analysis
The Su-27 and derivatives all have high LCC ask the Indian Air Force, less than the F-22 but not by much. They are cheap to procure but expensive to operate and less capable than the F-22.
Regards,
Joe
Yes, when the F-22 zooms around the stratosphere it will be visible with an IRST but I most definitely don’t want to be the pilot in the aircraft sporting the IRST. He’s a dead duck in hot water. The IRST will do 50 km max, by that time he’s got about 5 seconds before missile impact. He won’t know what hit him.
DeleteJoe
H Boresight,
DeleteSee the following link for SAABs take on LCC for various fighter platforms: http://forum.keypublishing.com/attachment.php?s=03d96e285524d296ec5409a25904b3f7&attachmentid=223978
Joe
I do agree with you on the F-22 numbers though, but it’s not like the Russians will have the numbers either, they simply can afford to operate a 1000 Flankers. Maybe China can afford otherwise but their 5 gen fighter timelines are pushed way out. If only the F-35 money was spent on the development of an affordable cost effective low-end F-22 export model without all the overkill add-ons and reliability issues:
Delete1. affordable AESA radar
2. minus stealth coatings
3. cheaper COTS avionics
4. lower rated engine
5. IRST
6. Helmet sight
No need to spend a trillion $ to develop a new aircraft like the F-35. USAF could have bought it in numbers for itself. I guarantee you that with numbers like 2500 units it should be comparable to the F-35 in terms of LCC and you end up with an aircraft that is aerodynamically competitive.
Thanks for the chat Boresight!
Regards,
Joe
Hi Joe,
DeleteDon’t get hung up on IRST published ranges of 50 km. NASA published the data proving that the higher an IR sensor is flown, the greater the transmission of IR wavelengths (due to the lack of atmospheric molecules that absorb IR). Expect IRST detect ranges on par with radar. Please see our "Airborne Infrared and Supersonic Stealth"
When you insist on flying at the edge of the atmosphere – things get weird.
So the deck gets stacked against the F-22s hallmark feature – the element of surprise - and the tax payer has flushed billions down the toilet on a (high/high) F-22 usage model.
We should definitely build and F-22 for export.
I’ve seen data for a brand new Indian Flanker at $30 million a copy. For the sake argument - let’s just quadruple that figure to $120 million – its still not even close to $350-400 per copy for an F-22 w/out helmet sighting.
Good stuff Joe!
Aerodynamically, the Flanker is half a generation beyond the F-14. Having said that, the F-14D is more than a match for the SU-27,30,33,35 in a BVR engagement. WVR, the "Super Tomcat" with it's VG wings, and high thrust to weight ratio would've been able to hold it's own. I guess we'll never know for sure.
ReplyDeletewhat?
Deletean obsolete plane with obsolete radar and the best western aa missiles (aim-120) that have lower characteristics then the comparable russian variants r-37/r-77.
The f-14 is dead and buried it's can't compare with the rafale let alone one of the flanker variants. All of the flankers have a large thrust/weight ratio some (su-35) much better then the tom cats.
You are 100% correct. The F-14D or F-15C just cannot turn with even the base SU-27. Compare the airshow demos, the SU-27 will leave either the Tomcat or the Eagle in the dust. And back in (I think it was published in Combat Aircraft magazine) 2002 US Navy F-14D's were easily defeated by French Rafales.
DeletePlease pardon me for my ignorance on this matter, but how do larger airframes (referring to Sukhoi-type aircraft in particular here) possess inherently larger growth potential than their larger counterparts? I understand that these aircraft have much larger internal volumes due to their larger cardinal dimensions, yet it appears to me as if nobody considers why these aircraft have such larger dimensions. Theoretically one can start from any design aspect, and I shall start from the two-engine requirement (completely arbitrary here.) The need for two engines necessarily increases aircraft size and requires far larger fuel tanks. This larger airframe necessarily increases drag, which requires a. a lower-drag airframe, b. more powerful or fuel efficient engines, or c. more fuel. In short, one requirement ensures that other aspects will be increased in size proportionally. Although it is possible that Sukhois have larger growth potential due to their larger volume (since aircraft designers normally measure growth potential in percentage of weight.) However, the larger kinematic requirements posed by a larger airframe (which produces more drag proportionally than a smaller airframe) possibly result in greater percentage of fuel storage than smaller (Western) aircraft. My question is, therefore, do Sukhois really have much more of a growth margin over their smaller peers? Additionally, more of a random question really, but could a D-band installation similar to the N036L be fitted to smaller aircraft (EF2000, Gripen spring to mind) considering the size and cooling requirements?
ReplyDeleteAnd to that end, if larger fighters do have much larger growth potential, what is the benefit of smaller fighters, besides lower life cycle costs?
DeleteWe don’t think the Flanker has greater growth potential than say a C-130 or a Boeing 707. Growth potential meaning derivatives/missions. However Flanker has evolved into a myriad of derivatives including the Su-33, Su-30, Su-30 MKI, Su-35S, and the Su-34.
DeleteSoviet airspace was e-n-o-r-m-o-u-s. Flanker (together with MiG-31) had to replace the Sukhoi Su-15, Yakovlev Yak-28, and especially the huge long range Tupolev Tu-28 series of interceptors. Flanker had to be big to given the endurance required to search for low level penetration threats (cruise missiles, B1, FB-111, etc). Typically aircraft size is predicated on the performance figures required which is based on what engines are available to power it. So the engine selection will almost always determine the rest of the aircraft layout – including its size.
We keep hearing about “drag” these days. A large fighter will typically be heaver and so gravity (not drag) will be the larger factor. Flanker is very light weight (for it size) and has taken over 20 time-to-climb records away from the F-15 eagle.
If you look at “Swirl of Controversy: Cope India and Red Flag 2008 Exercises” you will notice Su-30MK without extra tanks, while F-15 and Mirage operate w/tanks. The range of the F-15A was so poor that conformal fuel tanks (now standard on the F-15E) were developed in the 1970s to attempt to address the problem.
Whether the Flanker has greater growth potential than its western counterparts we don’t know. But its airframe is so large that almost anything can be fitted and any weapon carried – and in enough quality.
- The Boresight
The Lockheed F-104 had very little drag – but also very little fuel. Lockheed assurances that its “missile with a man” would reign supreme – turned out that Starfighter was effectively worthless as a combat aircraft - and was quickly bested (shot down) by the MiG-21 during the Indo-Pakistani war.
Delete- Boresight
So India is crawling for f-35 but Obama is not answering phones ?
ReplyDeletehttp://www.foxnews.com/world/2014/01/26/russian-rubbish-india-reportedly-disappointed-with-stealth-fighters-from-moscow/
I am sure that pak-fa has its problems. It may take a while for Russian electronics industry to catch up with avionics. But in the end pak-fa will fly and surely be better than any Su-27 variant. On the other hand I doubt that F-35 will have any use in a modern combat environment if it flies of course
no, the Indians wore disappointment with their variant of the PAK-FA the FGFA, the Russian version is a single seat variant with have different radar (not available for export) and different engines, the FGFA will be a 2 seater with an older radar and older engines (this might change) as they want to manufacture them locally, the Russians will keep their radars and engines secret for a minimum of 10 years and only export downgraded versions.
DeleteIf they buy yank they still won't get top avionics they'll get a downgraded version with a crappy radar a single engine and it will cost 10 more then the PAK.
ps The current Indian Su-30MKI's use French and Israeli avionics not Russian.
Correction, the current Su-30MKI uses French, Israeli, South African and Russian avionics.
DeleteRegards,
Joe
Perhaps. But stealth fighters have fundamental problems that are not being (or can not be) addressed in any real way. The F-35 is going to have a short combat radius (causing increased risks to your air-tanker fleet by drawing them in closer to the fighting) because valuable internal space for fuel is instead used for internal weapon bays: indeed we already see F-22A operating with 2 huge (zero stealth) wing drop tanks, pilot tubes on the nose and other protuberances. The whole stealth fighter thing ...is just to spend money.
ReplyDelete- Boresight
Hi Boresight,
DeleteDon't you think the Russians have successfully addressed this issue in the T-50? Please don't say its not a stealth fighter.
Regards,
Joe
from what I've seen the visibility is slightly worse in the PAK FA than the original Flankers
Deletebut ther is NO DOUBT that its a stelath fighter, just not the same type as the F 22, the F 22 is designed to carry a limited payload but its stealth would make it more likely to acheive its goal of air-superiority.
the PAK FA is also air-superiority but with the ability for long range and loiter capability, and heavier payload, allowing for more versatile fighting. ad its manuverability is better than any previous plane on the PLANET
here is MAKS 2015 demonstration footage, its phenominal!
https://www.youtube.com/watch?v=47YW7IMl9Og
I now this is hardly the most solid answer but I need some time to compile my enomrous quantity of info into something more readable.
Hello Boresight,
ReplyDeleteAside from the DRFM jamming techniques being readily fieldable on the Su-27 family, IRST is almost certainly the main make or break of future fighters to come. The AIM-9x block III is going to be the most dangerous missile fielded by the United States is is set to come out in 2022. It can solve some of the issues in the previous blocks, with three points of concern: distinguishing engines from flares, increased range and speed, and LOAL capability. Given that WVR missiles have an average kill probability of at least 74% it seems awfully likely that the F-35, while kniematically inferior may yet save the day IN POINT DEFENSE MISSIONS ONLY. You had brought up unit costs in the arguement of the equivalent capital vs capital in the scenario with 12-28 flankers vs 4 raptors; but given the fact that the USAF and allies are going to posses ~2000 F-35s total a capital vs capital scenario seems unlikely.
This leaves me with three questions, you had stated that IRST (in GENERAL) could see 50-150 miles out what does this mean? 50 at low altitude and 150 at high? Or depending on IRST quality?
People are claiming that the OLS-35 range is 50 km (~27 nmi), is this number true? If not what is it (I have heard that OLS-UMES can see 130 km (~80.something nmi)? Are OLS-35 and ...-UMES related?
What can a flanker do to respond to an AIM-9X block III launch given that its current counter measures are ineffective? Can the Russians field yet more convincing IRCMs (CMs = counter measures)?
Sincerely,
DeleteCameron
Hi Cameron,
DeleteSorry for the delayed response. I had finals.
Yes – we think that outside-the-radio-spectrum search/targeting will be essential
Unless AIM-9x series can be presented to the air stream so its seeker-head can see the target and tell the pilot “I see the target you directed me to look for” – BEFORE it is fired - some helmet cued weapons might (might) be susceptible to data-link jamming/denial. This would be classified so we don’t know.
Helmet cueing: tells the weapon first “fly that way” THEN find the target.
Helmet sighting: “Yes I see the target – fire me.”
This is a subtle - but (perhaps) huge distinction!
Missile lofting is good (thank you AIM-54!!).
The whole F-35 idea is an open question. The program has so many problems – that God knows what the plane will actually be able to do.
Yes the F-22A cost vs Flanker cost is just one argument. NATO will be able to field more aircraft than Russia. However, NATO will not be able to power project into Russia effectively with aircraft or UCAVs that require GPS or satellite based remote operation – so it’s a meaningless comparison.
The only thing that will work against a peer advisory is cruise-missiles with internal inertial guidance and manned long-range bombers with own targeting capability (no GPS).
True IRST capabilities are classified (Russian/American/Europeans) for everyone. IR propagation is greater (read: goes further) at higher altitudes. That’s just basic physics.
Helmet sighing is no guarantee and weapons will still be susceptible to new types of defensive expendables. Some Russian expendables produce a lot of smoke. What is that smoke comprised of - might be an interesting question?
- Boresight
Hey, I'm all for finals (NOT). I too finished them up; congrats.
DeleteI would have to respectfully disagree. The Sukhoi / MiG's IRST capability is awesome - I wish we had followed their lead. But the real make or break sensor is the Radar ! Radar has undergone its own stealth-like revolution in the form of PESA and now AESA radars. This is the cutting edge.
DeleteNow you combine AESA with IRST capability using some smart sensor fusion software, and you should have something that is dangerous all across the engagement envelope.
Yes. As we say in this link: http://theboresight.blogspot.com/2009/07/airborne-infrared-and-supersonic.html
DeleteIRST design cycles (which would include all manner of sensor integration/optimization) will outpace stealth airframes. Especially fitted to non-stealth designs with unobstructed unimpeded radar mechanics. It’s an arms race the stealth-fighter cannot win. This is why we will never see a stealth (radio-spectrum primary-emitter) AWACS. - Boresight
Inserting of stealth materials-technology between your primary radio-spectrum emitter/receiver – introduces a paradox. And creates is an engineering problem that should not be underestimated. - Boresight
DeleteHi Boresight,
DeleteThe transfer function of the F-22’s radome looks like is a band pass filter over the operating frequency of the radar. So there is really no paradox. Radar geometry and coatings may minimize RF returns so that the aircraft is stealthy head on. Not really difficult for the in band case considering that the radar antenna is in any case designed to absorb RF energy in its operating band.
Regards,
Joe
Yes. A band pass filter still passes frequencies (be it just the ones you want).
DeleteWith the proliferation of DRFM and other rado signal collection-replication technologies around the globe – we think it just a matter of time before AN/APG-77 frequencies will be collected and used to “see” through the F-22A nose cone. To an opposing radar using these frequencies the F-22 will effectively look like its flying without its nose-cone on.
- Boresight
Hello Boresight,
ReplyDeleteWe may have a first hand pilot account concerning Flanker maneuverability.
"I'm retired Royal Air Force governmentcheese411(another commentor of the video in). I flew the Tornado F3 and, later, the Tranche 2 Eurofighter from RAF Coningsby as part of QRA (Quick Reaction Alert) to intercept unidentified aircraft approaching and sometimes entering UK Airspace. I remember one incident vividly when a small group of Russian aircraft flew just 2 miles from the UK Airspace border and among that flight were 2 Su-27 Flankers designated 32 Red and 21 Red, an Il-76 Re-fueling aircraft designated 44 Blue and a smaller Il-12 (I believe) reconaissance plane. We came alongside them to their 9 o'clock and the Su-27 pilots saluted in our direction (As a sign of respect) of which we saluted back but then one of the Su-27s performed a hard left turn towards us which caused us to become caught up in the wash of the Sukhoi. I had to pursue him because of security reasons but I will admit the Flanker was not very quick to turn, descend or ascend. About 5 minutes later the flight began to turn away. Scary stuff though. I believe the F15 can outgun, outrun and out-manoeuvre the Sukhoi in any situation. Even the F15Es could out-do the Flanker."
Comment from: HMSDefender D36
The video the comment occurs on is:
https://www.youtube.com/watch?v=naIWWNxF1DQ
Granted this is an irrelevant video, and these are people commenting on YouTube, this may very well have a grain of truth. I attempted to check his profile, it not comprehensive but it is consistent with his comment.
So, what do you make of this account?
I wait with baited breath,
Cameron
Hi Gurney, Thanks for writing. We can’t speak to your experience obviously. :) All we can do is direct you to the first two videos provided in this post – which show maneuvering (I’m afraid) beyond anything in western inventories. If it’s any consolation it appears the RuAF has yet to adopt the R-77. - Boresight
ReplyDeleteHi Charlie,
ReplyDeleteYes – that’s the best demo we’re seen of T-50 to date. Whether the airplane is good enough to replace the Flanker fleet - I’m not convinced. Flanker still has better range and a bigger radar. If T-50 has quicker spool-up then perhaps as a replacement for MiG-29. It is good to keep a variety of aircraft in service – this presents a mix of threat aircraft and capabilities - to your advisory. More problems for him to have to cope with.Thanks for writing.
- Boresight
F22 does not have a big IR signature, in fact its very small. Much smaller than other aircraft
ReplyDeleteOh and F-22 flight characteristics are hugely underrated. We now know it sustains 28 degree per second turns. Flankers can't even approach that. Instantanous turn rate is also much superior. Sorry to spoil this flanker worshiping but it has already been outmached. Great airplane, but putting it ahead of F-22 is too much. Climb, turn, roll, you name it. F-22 surpasses flanker in every category
ReplyDeleteExcellent and objective research. You have been cited in a blog about:
ReplyDeletehttp://liberticida.altervista.org/concerto-a-palmyra-e-potere-aereo-un-punto-di-vista-tecnico-sullintervento-russo-in-siria/
and linked articles.
thankyou
y