TYPE: Twin-turboprop pressurised short-haul transport.
VARIANTS: An-26 ('Curl-A'): Original version; electrically manually operated conveyor flush with cabin floor for freight handling.
An-26B (Curl-A): Improved version, announced 1981, to carry three standard freight pallets, each 2.44 m (8 ft) long, 1.46 m (4 ft 9½ in) wide and 1.60 m (5 ft 3 in) high, with total weight of 5,500 kg (12,125 lb). Improved freight handling equipment.
'Curl-B': Signals intelligence (sigint) version; many short blade antennae mounted on fuselage.
CUSTOMERS: Military An-26s assigned to air commands in Soviet regiments and squadrons; exported to at least 27 air forces. Angolan and Mozambique aircraft have bomb racks. Aeroflot has more than 200, available as military reserve. Civil customers include Aero Caribbean (Cuba), Aeronica (Nicaragua), Air Mongol, Alyemda (Yemen), Ariana Afghan Airlines, CAAC (China), Cubana, Syrianair and Tarom (Romania).
DESIGN FEATURES: Generally similar to earlier An-24RT specialised freighter, with auxiliary turbojet; more powerful turboprops and redesigned 'beaver-tail' rear fuselage Oleg Antonov's special loading ramp forms underside of rear fuselage when retracted, slides forward under rear of cabin to facilitate direct loading and when airdropping cargo. Wing anhedral 2° on outer panels; incidence 5°; sweepback on outet panels 6° 50' at quarter-chord. 9° 41' on leading-edge, swept vertical and horizontal tail, tailplane dihedral 9°.
FLYING CONTROLS: Mechanical controls, mass balanced servo compensated ailerons with electrical glassfibre trim tabs, manual tab in each elevator, electrical trim servo tab in rudder, hydrauhcally actuated tracked and slotted TsAGI flaps, single-slotted on centre-section, double-slotted outboard of nacelles.
STRUCTURE: Conventional light alloy; two-spar wing, built in centre,two inner and two detachable outer sections, with skin attached by electrical spot welding, bonded/welded semi-monocoque fuselage in front, centre and rear portions, with 'bimetal' (duralumin-titanium) bottom skin for protection during operalion from unpaved airfields; blister on each side of fuselage forward of rear ramp carries track to enable ramp to slide forward; large dorsal fin; ventral strake on each side of ramp.
LANDING GEAR: Hydraulically retractable tricycle type, with twin wheels on each unit. Emergency extension by gravity. All units retract forward. Shock absorbers of oleo-nitrogen type on main units; nitrogen-pneumatic type on nose unit. Mainwheel tyres size 1,050 x 400 mm, pressure 5.9 bars (85 lb/sq in). Nosewheel tyres size 700 x 250 mm, pressure 3.9 bars (57 lb/sq in). Mainwheels fitted with hydraulic disc brakes and anti-skid units. Nosewheels can be steered hydraulcally through 45° each side while taxying and are controllable through ±10° during take-off and landing.
POWER PLANT: Two 2,103 kW (2,820 ehp) Ivchenko AI-24 VT turboprops, each driving a four-blade constant-speed fully leathering propeller. Electric de-icing system for propeller blades and hubs; hot air system for engine air intakes. One 7,85 kN (1,765 lb st) RU 19A-300 auxiliary turbojet in starboard nacelle for use, as required, at take-off, during climb and in level flight, and for self-contained starting of main engines. Two independent but interconnected fuel systems, with 5,500 kg (12,125 lb) of fuel, contained in integral tanks in inner wings and ten bag tanks in centre-section. Pressure refuelling socket in starboard engine nacelle. Gravity fuelling point above each tank area. Carbon dioxide inert gas system to create fireproof condition inside fuel tanks.
ACCOMMODATION: Basic crew of five (pilot, co-pilot, radio operator, flight engineer and navigator), with station at rear of cabin on starboard side for loading supervisor or load dispatcher. Optional domed observation window for navigator on port side of flight deck. Toilet on port side aft of flight deck; crew door, small galley and oxygen bottle stowage on starboard side. Emergency escape hatch in door immediately aft of flight deck. Large downward hinged rear ramp door, hinged to an anchorage mounted on tracks running forward under the blister fairings. This enables ramp/door to slide forward under fuselage for direct loading on to cabin floor or for airdropping of freight. When doing so, its rear is supported by the pivoted swinging arm on each side which also raises and lowers door in the alternative fixed-hinge mode. Door can be locked in any intermediate position. Electrically powered mobile winch, capacity 2,000 kg (4,409 lb), hoists crates through rear entrance and runs on a rail in the cabin ceiling to position payload in cabin. Electrically and manually operated conveyor, capacity 4,500 kg (9,920 lb), built-in flush with cabin floor of original An-26, facilitates loading and airdropping of freight. An-26B has removable rollgangs, mechanism for moving pallets inside hold, and moorings, enabling two men to load and unload three pallets in 30 mins. Rollgangs can be stowed against sides of cabin. Both versions can accommodate a variety of motor vehicles, including GAZ-69 and UAZ-469 military vehicles, or cargo items up to 1.50 m (59 in) high by 2.10 m (82.6 in) wide. Height of rear edge of cargo door surround above the cabin floor is 1.50 m (4 ft 11 in). Cabin is pressurised and air-conditioned, and can be fitted with a row of tip-up seats along each wall to accommodate a total of 38 to 40 persons. Conversion to troop transport role, or to an ambulance for 24 stretcher patients and a medical attendant, takes 20 to 30 min in the field.
SYSTEMS: Air-conditioning system uses hot air tapped from the 10th compressor stage of each engine, with a heat exchanger and turbocooler in each nacelle. Cabin pressure differential 0.29 bar (4.27 Ib/sq in). Main and emergency hydraulic systems, pressure 151,7 bars (2,200 lb/sq in), for landing gear retraction, nosewheel steering, flaps, brakes, windscreen wipers, propeller feathering and operation of cargo ramp and emergency escape doors. Handpump to operate doors only and build up pressure in main system. Electrical system includes two 27V DC starter/generators on engines, a standby generator on the auxiliary turbojet, and three storage batteries for emergency use. Two engine driven alternators provide 115V 400Hz single-phase AC supply, with standby inverter. Basic source of 36V 400Hz three-phase AC supply is two inverters, with standby transformer. Permanent oxygen system for pilot, installed equipment for other crew members and three portable bottles for personnel in cargo hold. Bleed air thermal de-icing system for wing and tail unit leading-edges. Electric windscreen de-icing.
AVIONICS: Standard com/nav avionics comprise two VHF transceivers, HF, intercom, two ADF, radio altimeter, glidepath receiver, glideslope receiver, marker beacon receiver, weather/navigation radar, directional gyro and flight recorder. Optional avionics include a flight director system, astrocompass and autopilot.
EQUIPMENT: Standard equipment includes parachute static line attachments and retraction devices, tiedowns, jack to support ramp sill, flight deck curtains, sun visors and windscreen wipers. Optional items include OPB-1R sight for pinpoint dropping of freight, medical equipment, and liquid heating system.
ARMAMENT: Provision for bomb rack on fuselage below each wingroot trailing-edge.