Whereas the contemporary MiG-29 was designed as a short range fighter, the Su-27 Flanker was built for the longer range. It is significantly larger than the MiG and has a bigger, longer nose. Both aircraft are quite similar in appearance with their double vertical stabilisers and double, wedge shaped air intakes underneath the fuselage with space between. Both have air intakes under the forward fuselage and wing leading edge root extensions, while the middle and rear fuselage are below the wings, making it a mid-wing configuration. The forward fuselage measures about half of the total length. The bubble canopy pops out more than that of the Fulcrum. 

The Su-27 family has space in between the intakes, but unlike the MiG-29 the nose gear retracts forward (except for the prototypes). The space between the air channels and engines remains until the end of the fuselage. The end of the fuselage extends beyond the exhausts, creating a so-called stinger tail, typical for most members of the Su-27 family. Although short, the wings can be regarded more as swept wings than (cropped) delta wings.

The Su-27 was co-produced in China as the Shenyang J-11, but the Chinese quickly developed their own versions, effectively copying the Sukhoi design. Still they are highly similar in appea­rance to the original Russian aircraft, so they are described here.

The different versions of the Flanker and Fullback family can be distinguished by

• the presence of canards
• the shape of the canopy
• the width of the front fuselage 
• the presence of a 'stinger tail cone'
• the length and shape of the 'stinger tail cone'
• the number of wheels on the nose and main gear
• the location of the nose gear
• the presence of thrust vectoring nozzles
• the presence of a refueling probe
• the presence or a tailhook and enlarged flaps
• the shape of the wingtips
• the shape and visibility of the engine nozzles
• the position of the infrared sensor pod on the nose
• the shape of the vertical stabilizers
• the shape of the nose
• the presence of ventral fins
• the presence of a pitot tube at the point of the nose
• the presence of formation lights
• the presence of multiple radar/laser warning sensors
• the presence of a dorsal airbrake

The T-10 is the factory designation for the Su-27 development aircraft, or prototypes. They differ significantly from the later production models. While the T-10 design evolved over time, creating internal and external changes, few characteristics are common. First of all, the wings have curved leading edges, around the tip. Furthermore, the vertical stabilisers are placed on top of the engines and the engine nozzles are completely within the airframe. There is no 'stinger tail' in between the exhausts. The single wheel nose gear is located underneath the front of the canopy and retracts backward. The nose is not as long and wide as on the production models. Finally, the main gear retracts forward in the wing extensions, with the gear doors doubling as speed brakes.

In total nine prototypes were built, designated T-10-1 until T-10-11, without T-10-7 and -8). Changes applied during the test programme are placement and removal of wing fences (one or two on each side), and the additional of small streamline bodies near the top of the vertical fins, in the leading edge, acting as anti-flutter weights. Similar ones were placed in the wing leading edges (near the tips) and in the horizontal stabilisers (near the root). Other modification include the addition of a cannon in the top right wing extension, slightly canting the vertical fins outward, a longer nose with a larger radome, the extension of the exhausts and the addition of an infrared sensor in front of the canopy, slightly off-centred to the right.  

Fast forward to the T-10-10, which has a longer, wider nose and outward canted vertical stabilisers. From this viewpoint also the curved wings leading edges are well visible, as are the long exhausts fully enclosing the nozzles. (photo: Igor Bubin/WikiMedia)

The original design, the T-10, proved far from satisfactory, so Sukhoi went back to the drawing board. The result was a heavily modified T-10, the T-10S, that received NATO reporting name 'Flanker-B'. It formed the basis for the first production model, that is normally called Su-27P, Su-27S or simply Su-27. There is no visual difference between the Su-27P and Su-27S, the P model is just missing the air-ground mode (likely mostly applicable to early production examples). Su-27SK is the export designation for the Su-27S, with only internal differences like a downgraded radar. Also, the cannot carry the ECM pod at the wing tips, but these are removable so not a clear recognition point anyway. The Chinese Su-27SKs are the only ones having formartion lights on the nose, air intakes and tail. The same applies to the Shenyang J‑11 and J-11A, that are locally built Flanker As.

Compared to the T-10, all these versions have longer wings without the distinct leading edge curve, but with square tips including missle launch rails, larger vertical stabilisers outside of the engines - straight up and with higher rudders, ventral fins and long, externally visible engine nozzles. Also the single wheel nose gear is placed further aft, just behind the canopy. It now retracts forward. The nose is longer and has a wider diameter for the radar. It droops down a bit, giving the typical Flanker appearance. Another typical Su-27 feature, the 'stinger' tail cone, also appeared. The end is pointed and can house the drag chutes. On top of the fuselage is a single dorsal airbrake. A gun was added to the right leading edge root extension. Finally, the canopy is slightly lower and longer, and has an infrared sensor in front of the windscreen, on the aircraft's centreline. 

The T-10Ss have a few specific recognition points compared to the early production Su-27s, like the long nose-mounted pitot tubes on most examples. Some T-10Ss had square tips on the vertical fin, some had a second bow frame in the canopy, others didn't. On later T-10Ss and production Su-27s the tops of on the vertical stabilisers are pointed, i.e. their tops have a triangle shape. Early production Su-27s are recognised best by the small strakes along the sides of the tail cone and the anti-flutter fairings on the vertical fins. Later production aircraft do not have these anymore. Moreover, they received a box-like extension on the sides of the stinger tail (for detail photo see above, under the introduction). Finally, the wing tip launch rails were replaced by slender ECM pods with launch rails underneath and the nose cone painted white (these were until then dark green).

Su-27P1M and Su-27S1M are the designations of the Ukrainian upgraded versions, that are externally indistinguishable from the originals, as far as we know.

The Chinese Su-27SKs can be distinguished from other examples by the formation lights on the nose, under the air intake and on the tail, all lighting up in green on this photo. (photo: mil.ru/WikiMedia)

The Soviets really wanted to take over the records set by the F-15 Eagle, so Sukhoi modified a T-10S as the P-42. Removed were the tops of the vertical fins (including the anti-flutter fairings), ventral fins, stinger tail cone, wing tip rails, infrared sensor and gun. Also, the P-42 was devoid of paint. Added was a small blade antenna on top of the fuselage. And indeed, the P-42 set many new records.

The lack of paint is a good recognition point of the P-42 speacial version of the Su-27, as is the lack of ventral fins, an opening for the cannon and the low vertical stabilisers. (photo: Sergey Ryabtsev/WikiMedia) 

Another T-10S converted to set a record was the T-10-20R. This one also lost the vertical fin caps, ventral fins, infrared sensor and gun, but retained the early version of stinger tail cone. The wing tips are the curved ones of the T-10. It can also be recognised by the single frame canopy and the short, simple conical nose cone.

The Sukhoi T-10-20R was intended for setting records. Hence it had low vertical stabilisers, no ventral fins, curved wing tips and a simple conical nose cone. (photo: Alan Wilson/WikiMedia)

Already an early T10S, designated T-10-24, was fitted with canards just in front of the main wings, to test them for future versions. For the rest this specific aircraft is the same as the early production Su-27s, so with for example the anti-flutter fairing on the tail.

The 25th T-10 was a development airplane for the carrier-borne Su-27K fighter. Its main features compared to the land-based Su-27s was the arrester hook in between the engines, under a more pointed, slightly upward canted raised tail cone. Unlike the Su-27K, it has a single wheel nose gear.

Basically, the Su-27UB is the two seat version of the Su-27, officially designated T-10U. The Flanker-C has a tandem cockpit, in which the back seater sits higher than the front seater, and an enlarged spine to accommodate the larger cockpit. The vertical stabilisers are higher due to an extension at the bottom, and this is why the rudder do not extend all the way to the bottom of them. Otherwise, the Su-27UB is identical to the Su-27 Flanker-B, with the early production models still having the 'clean' stinger tail cones and anti-flutter fairing on the vertical fins.

Su-27UBK is the designation of the export version of the Su-27UB. It is only equipment-wise different from the Russian version. But beware the Chinese 'Flanker-C's have formation lights, like on the Su-27SK. Additionally likewise, the Su-27UB1M is the Ukrainian upgraded version also externally the same.

Already in an early stage Sukhoi was thinking about thrust vectoring for the Su-27. One early aircraft was converted to the Su-27LL-PS testbed. The left exhaust was made significantly longer and has flaps up and down to direct the jet's direction. The eventual thrust vectoring system was far less bulky than on this test aircraft!

The version of the Flanker that can be launched from aircraft carriers at first seems quite similar to the single seat land-based Su-27s. Looking closer, you see a lot of differences. First of all the Su-33 has canards and a dual wheel nose gear with a straight shock absorber instead of a trailing link type gear. Additionally, it of course has a tail hook in between the engines, and folding wings and horizontal stabilisers. The trailing edge wing flaps are larger and extend in two steps (double slotted). A retractable refuelling probe was added at left side of the nose, just beside the front of the canopy). To make room, the infrared sensor is moved to the right side of the centreline. Finally, the stinger tail cone is shorter and slightly pointing up, with the 'side boxes' stopping further from the end. All these features makes the Su-33 easy to confuse with Chinese J-15 family (see below).

The factory designation of this variant is T-10K. The prototypes already resemble the production variant in many aspects, but some have standard, non-folding wings and stabilos, a single wheel nose gear and no infrared sensor. Also, the different prototypes differed mutually.

From this viewpoint, the Su-33 looks very similar to the standard Su-27, except for the double wheel nose gear with a straight leg. (photo: Igor Bubin/WikiMedia)

The trailing edge flaps consist of the parts, each extending under a different angle. Also note the canards in front of the main wings. (photo: I. Rudenko/WikiMedia, modified)

Here the Su-33's folding wings and horizontal stabilisers are demonstrated. Also the shorter tail cone and tail hook are well visible. (photo: Rob Schleiffert/WikiMedia, modified)

This photo shows the retracted refuelling probe on the left side of the canopy of the Su-33, and the off-centre infrared sensor. (photo: Russian Ministry of Defence/WikiMedia, modified)

In search of a longer range Su-27, Sukhoi developed the Su-27UB further in the Su-27PU (T‑10P?), later designated Su-30 (Su-30K for the export model). Externally, the differences compared to the initial two seater are the addition of the retractable refuelling probe besides the canopy, and the relocation of the infrared sensor to the right side of the fuselage centreline. Su-30M (T-10PM) is a version with a TV screen in the cockpit in support of TV guided bombs.

Only a few of these variants were built, as is was quickly further developed into the Su-30MK family. Beware that some Su-27UBs are painted to represent a Su-30, but don't have the changes applied.

The Su-35 can be regarded as the second-generation single seat Su-27 family member. Known internally as the Sukhoi T-10M, and also referred to as Su-27M, the Flanker-E has the retractable refuelling probe, off-centre nose mounted sensor, double wheel nose gear and flat tips on the vertical stabilisers of the Su-30MK branch. Additionally, the Su-35 has canards in front of the main wings. 

This is what the Su-35 'Flanker-E' in its final form looks like. Note the squared of vertical stabilisers and double wheel nose gear. (photo: Alan Wilson/WikiMedia)

This was to be the two seat tandem trainer version of the Su-35, but only one Su‑35UB was built. It looks very similar to the Su‑30MKI, with its canards. However, the Su‑35UB has no thrust vectoring, but more importantly has tall vertical fins with long rudders down to the bottom, and square tops.

To recognise the Su-35UB look for a tandem seat Flanker with canards and high, squared top vertical stabilisers with long rudders. (photo: rvb/WikiMedia, modified)

The Su-37 is externally identical to the Su-35, but then with thrust vectoring nozzle. As such, it may not always be easy to distin­guish, although only one was built that crashed in 2002. This version is also known under the nickname "Terminator".

The sole Su-37 is a Su-35 with thrust vectoring nozzles. You may see them hang a bit down on this photo, but this could very well be the standard position. (photo: Mike Freer/WikiMedia)

The standard Su-30MK is not the export version of the Su-30M, as you would presume from the designation, but has two notable differences. Hence, it has a different Sukhoi model number (T‑10M) and NATO reporting name ('Flanker-G'). The 'Flanker-G' has a dual wheel nose gear, square tops of the vertical stabilisers and full length rudders, i.e. they extend to the base of the vertical stabilisers.

The export versions, Su-30MKK for China and Su-30MK2 for China, Indonesia, Venezuela, Vietnam, and Uganda, are externally the same as the Su-30MK, as is the Su-30M2, the Russian air force variant of the Su-30MK2.

The basic Su-30MK also has rudders down to the base of the vertical stabilisers, demonstrated here on a Su-30MKK of China. (photo: Dmitriy Pichugin/WikiMedia)

The Su-30MKI is another Su-30M variant, specifically developed for India. Compared to the standard Su-30MK it has canards and thrust vectoring nozzles, but also Su-30 vertical stabilisers, so with triangular tops of the fins and shorter rudders.

The Su-30MKA is externally the same as the MKI, but with different avionics and weapon systems, exported to Algeria.

Russia, Kazakhstan, Belarus, Azerbaijan and Myanmar have a similar version as the MKI, called Su-30SM. Only the head-up display (HUD) is different. Su-30SM2 is an upgraded version to bring it in line with the Su-35SM, but so far no external differences have been identified, but it may be in the nozzles.

A Russian Su-30SM, the equivalent of the Su‑30MKI, shows its canards and short rudders in vertical stabilisers with pointed tops. (photo: Vitaly V. Kuzmin/WikiMedia, modified)

Malaysia also has a dedicated version of the Su-30M, called Su-30MKM. It is mostly similar to the Su-30MKI, but with formation lights behind the canopy, vertical tails and wingtips. Moreover, it has many radar and laser sensors, such as underneath the nose, at the sides of the air intakes and on top of the fuselage in front of the vertical fins. Finally, it has four narrow blade antennas in front of the canopy.

Once the Su-35 was developed, an upgrade programme for the existing Su-27s 'Flanker-B' resulted in the Su-27SM, with Su-35 technology. Like the Su-27 it is a single seat version with a single wheel nose gear, and the infrared pod to right side of the fuselage centreline. The basic version has no refuelling probe, although the only export version for Indonesia, designated Su-27SKM, does have it.

You could describe the Su-35S (in early stages called Su-35BM) as a Su-35 with a thrust vectoring capability and without canards, but there are many more differences. Most notable are the absence of the large airbrake on the spine (top of the fuselage), and lower vertical stabilisers with wider chord rudders. Additionally, the stinger tail cone has a different shape, without the typical rectangular boxes along the sides. These sides are shorter and thinner. Near the tip of the tail cone are small triangular protrusions at the sides.

The Su-33UB, also designated Su-27KUB (and T-10KM?), is a one-off dual seat version of the Su-33. Both crew members sit side-by-side, needing a wider forward fuselage. Their canopy has one bow frame and one centre­line frame. It is covered at the rear, so they have a limited rear view. For the rest, this variant is externally the same as the Su-33.

The Su-27 platform was chosen by Sukhoi as the basis for a new fighter bomber to replace the Su-24. In the T-10V development aircraft for the eventual Su-34 a new wider forward fuselage with sharp flat sides was mated to a standard Su-27, although with higher vertical stabilisers. The T-10V seats two in a side-by-side configuration, has a double wheel nose gear, retracting forward, canards and enlarged horizontal stabili­sers/ele­vators. Compared to the Su-33UB the canopy has a longer front part.

The final production version of the T-10V received Sukhoi designation Su-34, and a new NATO reporting name, 'Fullback'. Compared to the prototype Su-27IB it has a tandem two wheel main landing gear (according to the designers copied from the British TSR-2), a longer and thicker stinger tail cone with an APU inside, reinforced wings, as well as shorter visible engine nozzles.

The Su-34M is supposedly a modernised version, likely only with different avionics and weapon systems.

Apart from the wide nose, the Su-34 has as main features a tandem two wheel main gear and a long stinger tail cone. (photo: Yevgeny Pashnin/WikiMedia)

The mid-life update (MLU) resulted in a slightly modified version of the J-11A, fitted with a missile approach warning system (MAWS) suite all around. There are small bumps on the outside of vertical stabilisers and the sides of the fuselage, just aft of the canopy.

While the J-11A was a license-built Su-27 composed of Russian and Chinese produced parts, the J-11B is a locally developed variant. Essentially, it is a redesign of the original, using lighter materials, new engines and avionics. Compared to the J-11A the main differences are a black nose cone, and lower mounted wingtip pylons to carry the PL-8 missile. It also has Chinese WS-10 engines which are supposed to have shortened nozzles, but that is difficult to see in practice. The main colour if the J-11B is dark grey, like on the Su-27SKs and J-11As.

The J-11BG is a modernised version of the J-11B, recognisable by the grey radome, but otherwise externally the same. The different radome paint has to do with the radar inside. 

The Chinese navy version is the J-11BH. This is externally the same as the J-11B, but it is painted with a white anti-corrosive paint due to it being used for long flights over the salty seas. J-11BHG is - you guessed it - the modernized J-11BH with a grey radome and white general paintjob, but also with low-visibility roundels.

These are two seat versions of the J-11B, similar to the Su-27UBK but with the J-11B upgrades including the changed wingtips. Both have a black nose, where the air force version (J-11BS) is dark grey and the navy version (J-11BSH) white.

The Chinese navy also has Flankers that operate from aircraft carriers. These are very similar to the Su-33, having a shorter stinger tail cone with a tail hook underneath, canards in front of the main wings and a double wheel nose gear with straight leg. Only the lower wingtip pylons and the white paint scheme are giveaways for the J-15 'Flanker-X2'.

As you can see the Shenyang J-15 is very similar to the Sukhoi Su-33, but has the J-11B style wingtips. (photo: 日本防衛省・統合幕僚監部/WikiMedia, modified)

The J-15DH is basically a “Growler” variant of the J-15, i.e. it has a role similar to the US Navy’s F/A-18G. Externally, it is based on the J-15S (and similar to the J-16D below) having a smaller radar, no cannon, no infrared sensor in front of the canopy, special wingtips for electronic warfare equipment and big jamming pods at pylons under the wings and fuselage. Also features longer rudder tips.

A J-15DH is recognised by the long pods with electronic warfare equipment under the fuselage and wings, and at the wingtips, together with the canards. Note its extended refuelling probe! (photo: WikiMedia)

This is of course the two seat training variant of the J-15. It looks much like the Su-33UB, so with canards, a straight leg nose gear with two wheels and a tail hook, unlike other tandem seat Flanker versions.

The J-15T is a single seat, catapult capable evolution of the J-15. It has a catapult launch bar attached to the front of nose gear. The J-15T also features a shorter nose without pitot tube at the tip, and with a slanted cut on the radome, opposed to the perpendicular cut all other Flankers have. Finally, this version has the wingtips of the Russian built Flankers and J-11A. 

'Flanker-N' is the reporting name of the Shenyang J-16, basically a Su-30MKK updated with a lot of J-11B technology. Compared to the Su-30MKK the main external differences are light grey overall paint scheme the dark grey nose without a long pitot tube at the tip. Further­more, the J-16 has Chinese WS-10 engines with short nozzles. Some later built J-16s have a more classic dark grey paintscheme, with a light grey noze cone and long nozzle s.

The J-16 is externally very similar to the Su-30MKK, but has a dark grey nose without long pitot tube at its point. (photo: 中華民國國防部/WikiMedia, modified)

Here is an example of a Shenyang J-16 with a light grey nose. (photo: N509FZ/WikiMedia)

Basically, the J-16D an electronic warfare variant of the J-16, much like the J-15DH is of the J-15. The J-16D has a smaller radome, while the gun and infrared sensor in front of the canopy were removed. It has special wingtips for the EW equipment, and jammer pods on pylons under the wings and fuselage. Compared to the similar J-15D, the J-16D has no canards, no tail hook and a trailing link nose gear.

The electronic warfare pods at the wingtips, under the wings and fuselage together with the lack of canards make it easy to recognise this as a Shenyang J-16D. (photo: 中華民國國防部/WikiMedia)