Plane of the week: S-37

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SU-47 (S-37) BERKUT EXPERIMENTAL FIGHTER AIRCRAFT, RUSSIA

The Sukhoi Design Bureau of Moscow, Russia has developed the Su-47 (previously called the S-37 Berkut or Golden Eagle) fighter aircraft, which first flew in September 1997. Su-47 is in a forward swept wing configuration and uses a highly unstable triplane (with three main lifting surfaces) aerodynamic configuration. The Su-47 completed the first stage of flight trials in December 2001. In May 2002, Sukhoi was selected as prime contractor for the next-generation Russian PAK FA fighter programme. The PAK FA will be a development of the Su-47 but without the forward swept wings.

The design of the very high manoeuvrability prototype is based on the avionics and aerodynamics technologies developed for the Su-27 upgrade programme. Some of the systems and component designs from the Su-27, (the all weather supersonic fighter aircraft with NATO reporting name Flanker), have been used in the Su-47, for example the design of the canopy, landing gear, some of the avionics and the near-vertical tails

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MANOEUVRABILITY

The Su-47 has extremely high agility at subsonic speeds enabling the aircraft to alter its angle of attack and its flight path very quickly, and it also retains manoeuvrability in supersonic flight.

Maximum turn rates and the upper and lower limits on air speed for weapon launch are important criteria in terms of combat superiority. The Su-47 aircraft has very high levels of manoeuvrability with maintained stability and controllability at all angles of attack.

Maximum turn rates are important in close combat and also at medium and long range, when the mission may involve engaging consecutive targets in different sectors of the airspace. A high turn rate of the Su-47 allows the pilot to turn the fighter aircraft quickly towards the next target to initiate the weapon launch.

The swept-forward wing, compared to a swept-back wing of the same area, provides a number of advantages: higher lift to drag ratio; higher capacity in dogfight manoeuvres; higher range at subsonic speed; improved stall resistance and anti-spin characteristics; improved stability at high angles of attack; a lower minimum flight speed; and a shorter take-off and landing distance.

FUSELAGE

The Su-47 fuselage is oval in cross section and the airframe is constructed mainly of aluminium and titanium alloys and 13 per cent by weight of composite materials.

The nose radome is slightly flattened at the fore section and has a horizontal edge to optimise the aircraft's anti-spin characteristics.

WINGS

The forward swept midwing gives the unusual and characteristic appearance of the Su-47. A substantial part of the lift generated by the forward-swept wing occurs at the inner portion of the wingspan. The lift is not restricted by wingtip stall. The ailerons - the wing's control surfaces - remain effective at the highest angles of attack, and controllability of the aircraft is retained even in the event of airflow separating from the remainder of the wings' surface.

The wing panels of the Su-47 are constructed of nearly 90% composites. The forward-swept midwing has a high aspect ratio, which contributes to long-range performance. The leading-edge root extensions blend smoothly to the wing panels, which are fitted with deflectable slats on the leading edge; flaps and ailerons on the trailing edge.

The all-moving and small-area trapezoidal canards are connected to the leading-edge root extensions.

COCKPIT

The cockpit's design has focused on maintaining a high degree of comfort for the pilot and also on the pilot being able to control the aircraft in extremely high G-load manoeuvres. The aircraft is equipped with a new ejection seat and life support system. The variable geometry adaptive ejection seat is inclined at an angle of 60°, which reduces the impact of high G forces on the pilot. The seat allows dogfight manoeuvres with significantly higher G loadings than can normally be tolerated by the pilot.

The pilot uses a side-mounted, low-travel control stick and a tensometric throttle control.

LANDING GEAR

The aircraft uses a retractable tricycle-type landing gear with a single wheel at each unit. The smaller nose wheel retracts towards the rear and the two mainwheels retract forward into the wing roots.

http://www.airforce-technology.com/projects/s37/