Lazy sbst275! This week, will be the Sukhoi S-37 Berkut (Golden Eagle).
Dedicated `company-funded' research programme to explore post-stall manoeuvrability and `supermanoeuvrability' for next-generation fighter; despite original purpose, Sukhoi OKB soon began promoting S-37 as alternative `heavy' fighter to Mikoyan's MFI and, for this reason, it was designed as large, heavy twin-engined aircraft with some `stealth' features and with room and/or provision for incorporation of operational and mission equipment and systems. Design bureau and defence ministry sources have recently denied that the S-37 is a prototype of any combat aircraft; daily Red Star stated in 1997 that S-37 has zero priority for Russian air force; however, Russian Air Forces' C-in-C quoted in 1998 as foreseeing ``a future for the S-37''. Funds for programme derived from foreign sales of Su-27 `Flankers'.
First reported as Su-32 in 1996, then as S-32; possibly derived from - or follow-on to - 1982 forward-swept wing (FSW) demonstrator reportedly seen at Saki test airfield and supposedly codenamed SYB-A in West; existence of such an aircraft has been denied by Russian sources, although the Tsybin OKB built several forward-swept gliders and rocket-powered test aircraft in the late 1940s. Reports suggest that the SYB-A was a Sukhoi product, perhaps a converted Su-9. Sukhoi also used a forward-swept wing on the proposed S-86 propeller-driven corporate transport.
Design reportedly began in 1987. S-32 and S-37 originally had no tailplane, instead having shallow, broad, flat surfaces extending back from the wing trailing-edge; these later evolved into very narrow-span tailplanes. Reshuffle of designations continued with use of the Berkut as a `home' for the S-37 designation already employed by a single-engined light fighter with canard foreplanes and a cranked, cropped-delta wing, probably designed to meet the air forces' LFI requirement. S-37 designation became available when this design project was cancelled.
Prototype (marked `01') first flew at Zhukovsky test airfield, near Moscow, on 25 September 1997; following eighth sortie, on 27 November 1997, was temporarily grounded for increase of horizontal tail span and area, improved avionics integration and better tailoring of engines. Total of at least 31 flights by January 1999 and 50 to August 1999, when reported to be at half-way point of test programme; first phase completed 23 February 2000, after which the aircraft began a second supersonic phase; this included a brief deployment to the Russian Federation MoD Flight Test Centre at Akhtubinsk, where the aircraft exceeded M1.0 for the first time on its 88th flight, in August 2000. A third phase (with an expanded envelope) was due to begin at the end of November 2000, with this planned to include the type's 100th flight. However, in early 2000, testing was expected to continue for further ``four to five years''. 30º AoA achieved by mid-1999. Public debut at Aviation Day, Tushino, 15 August 1999.
Customers
After company testing, S-37 may be passed to LII trials centre at Zhukovsky, where some Russian air force participation is expected. Series production is not planned.
Design Features
Incorporates features and technology applicable to a fifth-generation fighter. Described as `integrated triplane' with short span, broad chord, tapered foreplanes; forward-swept, slightly tapering wing; and very short span, broad chord horizontal tail surfaces. Wings reported to incorporate provision for powered folding, without which the aircraft would be too large to fit in a standard hardened aircraft shelter. Twin tailfins each canted outwards at approximately 6º FSW improves subsonic agility, high AoA controllability, take-off and landing performance, reduces drag and diminishes frontal radar reflectivity. Other measures, including radar-absorbent materials and engine air intake shape and internal S ducting, taken to reduce frontal radar signature. Large, curved LERX above semicircular engine air intakes resemble those of an earlier Sukhoi light fighter project (a previous carrier of the Su-37 designation). Slightly flattened nosecone enhances supermanoeuvrability. Expected to demonstrate AoA up to 120º at speeds from zero to supersonic. The aircraft reportedly makes extensive use of RAM coatings, these having been developed in the late 1980s under project `Astra' which used two modified Su-25 preproduction aircraft.
Major components, such as tailfins, canopy, windscreen and landing gear, appear to be standard Su-27 parts. S-37 01 not equipped with radar, weapons or mission systems, but conspicuously has provision for their later fitment: forward- and aft-facing radomes, vented gun bay with cannon port, IRST mockup ahead of windscreen (offset to starboard) and dielectric panels in leading-edges of tailfins, LERX and foreplanes. Of twin, rear-facing radomes, starboard is on extended mounting and protrudes beyond trailing-edge of horizontal tail.
Wing swept forward (all data approximate) by 20º on leading-edge (except 24º sweptback gloves) and 37º on trailing-edge; rounded wingtips. Foreplane leading-edge has 50º sweep and -16º trailing-edge sweep. Horizontal tail swept 70º. Fin leading-edge sweep of 45º.
Flying Controls
FCS presumed developed from Avionika quadruplex digital FBW system of Su-35 and Su-37, probably with manual override; credited to Petrov. Wing appears to have two-thirds span leading-edge flaps on forward-swept portion, these each being in two parts, of which only the inboard has been noted deployed; trailing-edge has plain flaps inboard and ailerons outboard. Foreplanes may operate differentially and/or in unison. All-moving horizontal tail surfaces; conventional rudder in each fin.
Structure
Follows Su-27/Su-35 practice, but with wing of 90 per cent composites construction to ensure adequate stiffness.
Landing Gear
Generally as Su-33 (Su-27K) naval version of `Flanker'.
Power Plant
Two Aviadvigatel D-30F6M turbofans, each 93.1 kN (20,930 lb st) dry and 153.0 kN (34,392 lb st) with afterburning. Engine choice reportedly dictated by other programmes - all AL-41 engines dedicated to Mikoyan MFI; AL-37FU to Su-30MKI and Su-37 programmes. Potential for replacement with Saturn/Lyulka AL-37FU turbofans with two-dimensional vectoring nozzles; by R-79M engines; or by three-dimensional AL-41Fs rated at 196 kN (44,092 lb st). Last-mentioned reported in early 2000 as candidates for retrofit in 2005. Fixed geometry air intakes; rectangular auxiliary intake door for each engine above mid-fuselage. Unconfirmed reports allege engines have new nozzles which assist cooling of exhaust gases to reduce heat signature.
Accommodation
Pilot only, on 30º rear-tilted Zvezda K-36DM ejection seat, beneath rear-hinged, Su-27-type transparencies.
Avionics
Integrated avionics suite by Technocomplex. May receive new integrated suite by Kronstadt, including Transas Abris navigation and landing system.
Radar: Provision, only, in nose to install multimode, phased-array Phazotron radar of unspecified type, with supplementary, rear-facing radar in starboard tailcone. Planned radar will have range of up to 132 n miles (245 km; 115 miles) and be capable of simultaneously tracking 24 and engaging eight targets.
Instrumentation: Ramenskoye instruments and displays.
Mission: Provision for Pribor weapons control system.
Armament
Nil. Alleged provision for underwing pylons, wingtip missile launch rails and internal GSh-301 30 mm gun with aperture in upper surface of port LERX. Some sources report provision for conformal weapons carriage to reduce radar signature.
http://www.aeronautics.ru/archive/vvs/s37-01.htm
