The Sukhoi Su-47 Berkut (Russian: Су-47 Беркут - Golden Eagle ), also designated S-32 and S-37 during initial development, is an experimental supersonic jet fighter developed by Sukhoi Aviation Corporation. A distinguishing feature of the aircraft is its forward-swept wing, similar to that of the Grumman X-29. Its NATO reporting name is "Firkin".
Originally known as the S-37, Sukhoi redesignated its advanced test aircraft as the Su-47 in 2002. Officially nicknamed Berkut (Golden Eagle), the Su-47 was originally built as Russia's principal testbed for composite materials and sophisticated fly-by-wire control systems.
The aircraft makes use of forward-swept wings allowing superb maneuverability and operation at angles of attack up to 45° or more.
Forward-swept wings yield a higher maximum lift coefficient, reduced bending moments, and delayed stall when compared to more traditional wing shapes.
At high angles of attack, the wing tips remain unstalled allowing the aircraft to retain aileron control.
Unfortunately, forward sweep also induces twisting (divergence) strong enough to rip the wings off an aircraft built of conventional materials.
Only recently have composite materials made the design of aircraft with forward-swept wings feasible.
However, Sukhoi is now attempting to market the Su-47 to the Russian military and foreign customers as a production fighter in its own right.
The aircraft's performance has been so impressive that the Russian government has made funds available for further testing of the design.
Though similar in overall concept to the American X-29 research aircraft of the 1980s, the Su-47 is about twice the size and far closer to an actual combat aircraft than the US design.
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 while retaining maneuverability in supersonic flight.
he Su-47 has a maximum speed of Mach 2 at high altitudes and a greater than 9g capability.
The Su-47 aircraft has very high levels of maneuverability with maintained stability and controllability at extreme 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:
- a lower minimum flight speed
The Su-47s fuselage is oval in cross section and the airframe is constructed mainly of aluminium and titanium alloys and 13% (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.
The forward-swept midwing gives the unconventional (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 all-moving and small-area trapezoidal canards are connected to the leading-edge root extensions.
The downside of such a wing design is that it produces strong rotational forces that try to twist the wings off, especially at high speeds.
This twisting necessitates the use of a large amount of composites in order to increase the strength and durability of the wing. Despite this, the plane was initially limited to Mach 1.6. Recent engineering modifications have raised this limit, but the new limit has not been specified.
Although not revolutionary, the thrust vectoring (with PFU engine modification) of ±20° at 30°/second in pitch and yaw will greatly support the agility gained by the forward-swept-wings.
The aircraft is equipped with a new ejection seat and Life support (aviation). 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 and missile avoid maneuvers with significantly higher g loadings than can normally be tolerable.
The Su-47 pilot uses a side-mounted, low-travel control stick and a tensiometric throttle control. This reclined seating arrangement was first used in the F-16 Fighting Falcon but was determined to be of little value and has not been replicated in any American fighter since.
(This text was adapted from http://www.wikipedia.org/ )(GFDL)
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