Sukhoi Su-47
Encyclopedia
The Sukhoi Su-47 Berkut (NATO reporting name
Firkin), also designated S-32 and S-37 (not to be confused with the twin-engined delta canard design offered by Sukhoi in the early 1990s under the designation Su-37
) during initial development, was an experimental supersonic
jet fighter
developed by Sukhoi Aviation Corporation. A distinguishing feature of the aircraft was its forward-swept wing
that gave the aircraft excellent agility and maneuverability. While serial production of the type never materialized, the sole aircraft produced served as a technology demonstrator prototype for a number of advanced techhnologies later used in the 4.5 generation fighter SU-35BM
and current 5th generation fighter prototype Sukhoi PAK FA
.
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. Conversely, forward sweep geometrically creates increased angle of incidence of the outer wing sections when the wing bends under load. This creates more lift, more load, more angle of incidence, etc. This leads to a tendency for the wings to fail structurally at lower speeds than for a straight or aft-swept wing. Forward swept wings counter this by being designed to twist downward as they bend upward. This twisting-as-it-bends is done with composite materials on the S-37, but it can also be done, to an extent, with conventional materials.
The project was launched in 1983 on order from the Soviet Air Force. But when the USSR dissolved, funding was frozen and development continued only through funding by Sukhoi. Like its US counterpart, the Grumman X-29
, the Su-47 was primarily a technology demonstrator for future Russian fighters; however, Sukhoi briefly attempted to market the Su-47 to the Russian military and foreign customers as a production fighter in its own right.
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, an internal weapons bay, and space set aside for an advanced radar. Though similar in overall concept to the Grumman X-29
research aircraft of the 1980s, the Su-47 is larger 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 wing
s in order to fit inside Russian hangars.
Like its immediate predecessor, the Su-37, the Su-47 is of tandem-triple 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
.
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. Like most other fighters with fly by wire
controls, the Su-47 achieves some of its high maneuverability through relaxed stability
.
The swept-forward wing, compared to a swept-back wing of the same area, provides a number of advantages:
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.
A downside of such a forward-swept wing design is that it geometrically produces wing twisting as it bends under load, resulting in greater stress on the wing than for a similar straight or aft-swept wing. This requires the wing be designed to twist as it bends - opposite to the geometric twisting. This is done by the use of composites wing skins laid-up to twist. 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.
(with PFU engine modification) of ±20° at 30°/second in pitch and yaw will greatly support the agility gained by other aspects of the design.
. 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 avoidance 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. Pilots, however, claim that the cockpit gives them low visibility due to poor design. This reclined seating arrangement was first used in the American F-16.
NATO reporting name
NATO reporting names are classified code names for military equipment of the Eastern Bloc...
Firkin), also designated S-32 and S-37 (not to be confused with the twin-engined delta canard design offered by Sukhoi in the early 1990s under the designation Su-37
Sukhoi Su-37
The Sukhoi Su-37 is an experimental single-seat, supermaneuverable multirole jet fighter, designed by Sukhoi. A further development of the original Su-27 'Flanker', it was modified from the first-generation Su-35 prototypes...
) during initial development, was an experimental supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
jet fighter
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
developed by Sukhoi Aviation Corporation. A distinguishing feature of the aircraft was its forward-swept wing
Forward-swept wing
A forward-swept wing is an aircraft wing configuration in which the quarter-chord line of the wing has a forward sweep. The configuration was first proposed in 1936 by German aircraft designers.Perceived benefits of a forward-swept wing design include...
that gave the aircraft excellent agility and maneuverability. While serial production of the type never materialized, the sole aircraft produced served as a technology demonstrator prototype for a number of advanced techhnologies later used in the 4.5 generation fighter SU-35BM
Sukhoi Su-35
The Sukhoi Su-35 is a single-seat, twin-engined supermaneuverability multirole fighter. It is a derivative of the Su-27 'Flanker', and was initially known as the Su-27M. More than a dozen of these were built with some used by the Russian Knights aerobatic demonstration team...
and current 5th generation fighter prototype Sukhoi PAK FA
Sukhoi PAK FA
The Sukhoi PAK FA is a twin-engine jet fighter being developed by Sukhoi OKB for the Russian Air Force. The Sukhoi T-50 is the prototype for PAK FA. The PAK FA is one of only a handful of stealth jet programs globally...
.
Development
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.TsAGI
TsAGI
TsAGI is a transliteration of the Russian abbreviation for Центра́льный аэрогидродинами́ческий институ́т or "Tsentralniy Aerogidrodinamicheskiy Institut", the Central Aerohydrodynamic Institute....
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
Junkers Ju 287
-Bibliography:* Hitchcock, Thomas H. Junkers 287 . Acton, MA: Monogram Aviation Publications, 1974. ISBN 0-914144-01-4.-External links:*...
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. Conversely, forward sweep geometrically creates increased angle of incidence of the outer wing sections when the wing bends under load. This creates more lift, more load, more angle of incidence, etc. This leads to a tendency for the wings to fail structurally at lower speeds than for a straight or aft-swept wing. Forward swept wings counter this by being designed to twist downward as they bend upward. This twisting-as-it-bends is done with composite materials on the S-37, but it can also be done, to an extent, with conventional materials.
The project was launched in 1983 on order from the Soviet Air Force. But when the USSR dissolved, funding was frozen and development continued only through funding by Sukhoi. Like its US counterpart, the Grumman X-29
Grumman X-29
|-See also:-References:NotesBibliography* Thruelsen, Richard. The Grumman Story. New York: Praeger Publishers, Inc., 1976. ISBN 0-275-54260-2....
, the Su-47 was primarily a technology demonstrator for future Russian fighters; however, Sukhoi briefly attempted to market the Su-47 to the Russian military and foreign customers as a production fighter in its own right.
Design
Sukhoi Su-27
The Sukhoi Su-27 is a twin-engine supermanoeuverable fighter aircraft designed by Sukhoi. It was intended as a direct competitor for the large United States fourth generation fighters, with range, heavy armament, sophisticated avionics and high manoeuvrability...
family. Nonetheless, the aircraft includes reduced radar signature features, an internal weapons bay, and space set aside for an advanced radar. Though similar in overall concept to the Grumman X-29
Grumman X-29
|-See also:-References:NotesBibliography* Thruelsen, Richard. The Grumman Story. New York: Praeger Publishers, Inc., 1976. ISBN 0-275-54260-2....
research aircraft of the 1980s, the Su-47 is larger 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 wing
Folding wing
A folding wing is a design feature of aircraft to save space in the airfield, and time, and is typical of naval aircraft that operate from the limited deck space of aircraft carriers. The folding allows the aircraft to occupy less space in a confined hangar because the folded wing normally rises...
s in order to fit inside Russian hangars.
Like its immediate predecessor, the Su-37, the Su-47 is of tandem-triple layout, with canards
Canard (aeronautics)
In aeronautics, canard is an airframe configuration of fixed-wing aircraft in which the forward surface is smaller than the rearward, the former being known as the "canard", while the latter is the main wing...
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
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
, while the longer boom houses a brake parachute
Parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...
.
Maneuverability
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 1.6 at high altitudes and a 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. Like most other fighters with fly by wire
Fly by Wire
Fly by Wire: The Geese, the Glide, the Miracle on the Hudson is a book written in 2009 by William Langewiesche about US Airways Flight 1549 with emphasis on the role played by the advanced fly-by-wire flight control system of the aircraft....
controls, the Su-47 achieves some of its high maneuverability through relaxed stability
Relaxed stability
In aviation, relaxed stability is the tendency of an aircraft to change its attitude and angle of bank of its own accord. An aircraft with relaxed stability will oscillate in simple harmonic motion around a particular attitude at an increasing amplitude....
.
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 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.
A downside of such a forward-swept wing design is that it geometrically produces wing twisting as it bends under load, resulting in greater stress on the wing than for a similar straight or aft-swept wing. This requires the wing be designed to twist as it bends - opposite to the geometric twisting. This is done by the use of composites wing skins laid-up to twist. 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 vectoring
The thrust vectoringThrust vectoring
Thrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....
(with PFU engine modification) of ±20° at 30°/second in pitch and yaw will greatly support the agility gained by other aspects of the design.
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 maneuvers. The aircraft is equipped with a new ejection seat and life support systemLife support (aviation)
Life support, or aircrew life support, in aviation, is the field centered on, and related technologies used in, ensuring the safety of aircrew, particularly military aviation. This includes safety equipment capable of helping them survive in the case of a crash, accident, or malfunction.Life...
. The variable geometry adaptive ejection seat is inclined at an angle of 60°, which reduces the impact of high g forces
G-force
The g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
on the pilot. The seat allows dogfight and missile avoidance 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. Pilots, however, claim that the cockpit gives them low visibility due to poor design. This reclined seating arrangement was first used in the American F-16.
