SU-27 Flanker

The Sukhoi Su-27  (NATO reporting name: Flanker) is a one-seat Mach-2 class jet fighter originally manufactured by the Soviet Union, and designed by the Sukhoi Design Bureau. It was intended as a direct competitor for the large United States fourth generation fighters, with long 3,530 km range, heavy armament, sophisticated avionics and high agility. The Su-27 most often flies air superiority missions, but is able to perform almost all combat operations. Complementing the smaller MiG-29, the Su-27's closest US counterpart is the F-15 Eagle.

There are several related developments of the Su-27 design. The Su-30 is a two-seat, dual-role fighter for all-weather, air-to-air and air-to-surface deep interdiction missions. The Su-33 ‘Flanker-D’ is a navy fleet defense interceptor for use on aircraft carriers. Further versions include the side-by-side 2-seat Su-34 ‘Fullback’ strike variant and the Su-35 ‘Flanker-E’ improved air defense fighter.

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 minimize 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.

Sketch of Su-27 performing Pugachev's cobra maneuver.

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 maneuverability 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-30MK and Su-37 models), allowing the fighter to perform hard turns with almost no radius, incorporate vertical somersaults into level motion and limited nose-up hovering.

 

2016 (c)