The Sukhoi Su-47 Berkut (Russian: áу-47 Ñõрúут - 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".
Although the Berkut has been referred to as the Su-47 since 2002, suggesting that it is a ready-for-production warplane, the sole aircraft produced is an advanced technology demonstrator prototype and manufacture of a planned second flying prototype was cancelled.
[edit] History
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.
TsAGI has long been aware of the advantages of forward-swept wings, with research including the development of the Tsibin LL and study of the captured Junkers Ju 287 in the 1940s. 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.
Like its western counterpart, the Grumman X-29, the Su-47 is primarily a technology demonstrator, one intended to lay the foundation for the next Russian fighter. Such a fighter must not only be as advanced as the US F-22 Raptor and German/British/Spanish/Italian Eurofighter Typhoon, but must also compete for funding with the more conventional MiG 1.44. 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.
Design
The Su-47 is of similar dimensions to previous large Sukhoi fighters, such as the Su-35. To reduce development costs, the Su-47 borrowed the forward fuselage, vertical tails, and landing gear of the Su-27 family. Nonetheless, the aircraft includes reduced radar signature features (including radar absorbent materials), an internal weapons bay, and space set aside for an advanced radar. 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.
To solve the problem of wing-twisting, the Su-47 makes use of composite materials carefully tailored to resist twisting while still allowing the wing to bend for improved aerodynamic behavior. Due to its comparatively large wingspan, the Su-47 is to be equipped with folding wings, in order to fit inside Russian hangars. Like its immediate predecessor, the Su-37, the Su-47 is of tandem-triplane layout, with canards ahead of wings and tailplanes. Interestingly, the Su-47 has two tailbooms of unequal length outboard of the exhaust nozzles. The shorter boom, on the left-hand side, houses rear-facing RADAR, while the longer boom houses a brake parachute.
Manueverability
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. The Su-47 has a maximum speed of Mach 2 at high altitudes and a greater than 9g capability.
Maximum turn rates, and the upper and lower limits on airspeed for weapon launch, are important criteria in terms of combat superiority. 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:
higher lift-to-drag ratio
higher capacity in dogfight maneuvers
higher range at subsonic speed
improved stall resistance and anti-spin characteristics
improved stability at high angles of attack
a lower minimum flight speed
a shorter take-off and landing distance
Fuselage
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.
Wings
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 wing panels 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.
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.
Thrust evctoring
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.
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 (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.
General characteristics
Crew: 1
Length: 22.6 m (74 ft 2 in)
Wingspan: 15.16 m to 16.7 m (49 ft 9 in to 54 ft 9 in)
Height: 6.3 m (20 ft 8 in)
Wing area: 666 ft² (61.87 m²)
Empty weight: 36,100 lbs (16375 kg)
Loaded weight: 55,115 lb (25,000 kg)
Max takeoff weight: 77,162 lbs (35,000 kg)
Powerplant: 2Ã Lyulka AL-37FU afterburning, thrust-vectoring (in PFU modification) turbofans with digital control
Dry thrust: 83.4 kN (18,700 lbf) each
Thrust with afterburner: 142.2 kN (32,000 lbf) each
Thrust vectoring: ±20° at 30° per second in pitch and yaw
Performance
Maximum speed: Mach 2.1 ((2,550 km/h, 1550 mph)
* At sea level: Mach 1.35 (1,400 km/h, 870 miles))
Range: 3,300 km (2,050 mi)
Service ceiling: 18,000 m (59,050 ft)
Rate of climb: 230 m/s (45,300 ft/min)
Wing loading: 79.4 lb/ft² (360 kg/m²)
Armament
Guns: 1Ã 30 mm GSh-30-1 cannon with 150 rounds
Missiles: 14 hardpoints (2 wingtip, 6-8 underwing, 4-6 conformal under the fuselage)
Air-to-air: R-77, R-77PD, R-73, K-74
Air-to-surface: X-29T, X-29L, X-59M, X-31P, X-31A, KAB-500, KAB-1500
