WOLFSBERG RAVEN 257

TYPE: Light utility twin-prop transport.

PROGRAMME: Definitive design began in June 1997. Wings and tail surfaces of prototype made by Letov Air in Prague; rest of aircraft and flight testing by Evektor-Aerotechnik in Kunovice, Czech Republic. First flight (OK-RAV) 28 July 2000. Original date set for certification to FAR Pt 23 was April 2002, but delays caused this to be postponed. Design and manufacture transferred back to Letov Air in September 2000. Some major modifications were carried out to prototype, increases in wing span and MTOW; and forward port and starboard doors repositioned to provide direct access to flight deck. Production of the conforming prototype and structural test aircraft was proceeding in late 2003/early 2004 after reorganisation and changing the name of the company to Wolfsberg Letecka Tovarna s.r.o. Initial plan to customise 'green' aircraft at various Western European locations has been abandoned.

COSTS: Approximately €750,000 (2003).

DESIGN FEATURES: High-wing, twin-boom configuration with square section fuselage and high-set tailplane. Design goals include ability to operate from short unprepared strips, simple systems and easy field maintenance for operation in less-developed areas, combined with low acquisition and operating costs; seen as modern replacement for aircraft in the B-N Islander and Piper Aztec class, and as a 'step up' for operators of single-engined utility aircraft such as the Cessna 206, with applications in passenger, cargo, medevac and airdrop roles.
NACA 23018 section wings, with 2o 30' dihedral; 3o incidence; NACA 0012 section horizontal and vertical tail surfaces.

FLYING CONTROLS: Conventional and manual, via push-pull rods. Control surfaces statically balanced. Two-section elevator with independent controls and trim tab on port side. Maximum elevator deflection +27/-22o, aileron deflection +25/-15o; rudder deflection ±25o. Trim tab on starboard rudder. Four-section electrically actuated flaps, T-O setting 20o, landing 48o.

STRUCTURE: Conventional, mostly riveted metal, with glass fibre wingtips, nosecone, cargo hatch and engine cowlings.

LANDING GEAR: Non-retractable tricycle type, based on, and mostly interchangeable with, that of B-N Islander, with twin wheels on each main unit and single nosewheel; oleo strut suspension; mainwheel legs braced to bottom of fuselage. Mainwheel tyre size 7.00-6; nosewheel 6.00-6; Cleveland 40-98F brakes on mainwheels; 40-76D on nosewheel.

POWER PLANT: Two 224 kW (300 hp) Teledyne Continental IO-550-N8B flat-six engines, driving two-blade Hartzell HC-C2YF-2CUF/FC8475K-6/SM8 composites propellers. Fuel contained in two integral tanks in outer wings, combined capacity 536 litres (141.5 US gallons; 118 Imp gallons), with filler port in upper surface of each wing.

ACCOMMODATION: Two-crew cockpit (although aircraft will be certified for single-pilot operation); up to eight passengers, or combi configuration with four passengers and 500 kg (1,102 lb) of cargo. Crew door on each side; sliding semi-bulkhead separates flight deck from cabin/cargo area, which has flat floor and quick-change features, with passenger door at rear on port side and upward-hinged rear cargo door. In cargo configuration, fuselage can accommodate 304 x 139 cm pallets, 1.2 x 1.0 m Europallets and bulk cargo under netting. Baggage door on port side, emergency exit on starboard side.

SYSTEMS: 24 V electrical system includes two engine-driven alternators and 24 V 19 Ah accumulator.

AVIONICS: Dual VHF nav/com, ADF, transponder, GPS and DME.

 

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