Design Overview

The Su-27's basic design is aerodynamically similar to the MiG-29, but it is substantially larger. It is a very large aircraft, and to mimimize its weight its structure has a high percentage of titanium (about 30%, more than any of its contemporaries). No composite materials were used. The swept wing blends into the fuselage at the leading edge extensions and is essentially a delta, although the tips are cropped for wingtip missile rails or ECM pods. The Su-27 is not a true delta, however, because it retains conventional tailplanes, with two vertical tailfins outboard of the engines, supplemented by two fold-down ventral fins for additional lateral stability.

The Su-27's Lyulka AL-31F turbofan engines are widely spaced, both for safety reasons and to ensure uninterrupted airflow through the intakes. The space between the engines also provides additional lift, reducing wing loading. Movable guide vanes in the intakes allow Mach 2+ speeds, and help to maintain engine airflow at high alpha. A mesh screen over each intake prevents debris from being drawn into the engines during take-off.

The Su-27 had the Soviet Union's first operational fly-by-wire control system, developed based on Sukhoi OKB's experience in the Sukhoi T-4 bomber project. Combined with relatively low wing loading and powerful basic flight controls, it makes for an exceptionally agile aircraft, controllable even at very low speeds and high angles of attack. In airshows the aircraft has demonstrated its maneuvrability with a Cobra (Pugachev's Cobra) or dynamic deceleration - briefly sustained level flight at a 120° angle of attack. Thrust vectoring has also been tested (and is incorporated on later Su-30MKI and Su-35 models), allowing the fighter to perform hard turns with almost no radius, incorporate vertical somersaults into level motion and limited nose-up hovering. The usefulness of the 'Flanker's' maneuverability in real-world combat is hotly debated, with some western experts claiming it is inferior to the F-22 Raptor and Eurofighter Typhoon. With the advanced capability of modern air-to-air missiles, its turn performance may be of little actual benefit in a real fight. Of course, as history has often demonstrated, pilot training and strategy is often of far greater significance than raw performance. Nonetheless, the Su-27 is today one of the world's most agile aircraft, civilian or military.

The naval version of the 'Flanker,' the Su-27K (a.k.a. Su-33), incorporates canards for additional lift, reducing take-off distances (important because the Admiral Kuznetsov aircraft carrier has no catapults). These canards have also been incorporated in some Su-30s, the Su-35, and the Su-37.

In addition to its considerable agility, the Su-27 uses its substantial internal volume for a very large internal fuel capacity. In an overload configuration for maximum range, it can carry 9,400 kg (20,700 lb) of internal fuel, although its maneuverability with that load is limited, and normal load is 5,270 kg (11,620 lb). The advantage is that for long-range missions, the Su-27 rarely requires drop tanks, reducing drag and leaving its pylons free for weapons.

The Su-27 is armed with a single Gryazev-Shipunov GSh-30-1 30 mm cannon in the starboard wingroot, and has up to 14 hardpoints for missiles and other weapons. Its standard missile armament for air-to-air combat is a mixture of Vympel R-73 (AA-11 Archer), Vympel R-27 (AA-10 'Alamo') weapons, and Vympel R-77 (AA-12 'Adder').

The limitation of the Su-27 is its cockpit and avionics. The Su-27 has a HUD, but it does not have a true HOTAS control system, nor does it have modern multi-function displays. (Later Su-30 and Su-35 aircraft have a 'glass' cockpit, designed by the French company Sextant Avionique.) The original radar, the Phazotron N-001 (NATO 'Slot Back'), is a pulse-Doppler set with track-while-scan capability, but its processor is relatively primitive, making it vulnerable to false alarms and blind spots, as well as being more difficult to use. Su-30 and Su-35 aircraft have the vastly superior Phazotron 'Bars' N-011M with an electronically steered antenna, improving range, multiple target capability, and sensitivity.

The Su-27 has an infrared search and track (IRST) system in the nose just foreward of the cockpit, which also incorporates a laser rangefinder. This system can be slaved to the radar, or used independently for "stealthy" attacks. It also controls the cannon, providing greater accuracy than a radar sighting mode.