The third prototype Yak-42
In the Soviet Union the prototype (SSSR-1974) of a new short-range civil transport accommodating a maximum 120 passengers, the Yakolev Yak-42, made its maiden flight on 7 March 1975. This was powered by three Lotarev D-36 turbofans, in a similar rear-engine layout to the Yak-40. Three prototypes ordered initially; first prototype (SSSR-1974) flew 7 March 1975, with 11 degree wing sweepback and furnished in 100-seat local service form, with carry-on baggage and coat stowage fore and aft of cabin; second prototype (SSSR-1975, later SSSR-42304) had 23 degree sweepback and more cabin windows, representative of 120-seat version with three more rows of seats and no carry-on baggage areas; third prototype (SSSR-1976, later SSSR-42303) introduced small refinements; flight testing proved a 23 degree wing superior.
The second Yak-42 flew in April 1976 and the third, which was exhibited at the Paris Air Show earlier this year and is representative of the production version, flew in February 1977. By May, these three aircraft had totalled some 320 hrs of testing.
The Yak-42 is designed to have a fatigue life of at least 30,000 hrs and 30,000 landings, and the life of the turbofans that power the new aircraft is said to be 18,000 hrs, subject to major overhaul and revision at 6,000 and 12,000 hrs. Glassfibre and carbon fibre com-posites are used to a considerable degree in the construction of the Yak-42, and it is claimed that the noise levels meet the newest require-ments.
The maximum take-off weight of the Yak-42 was increased in 1981 to 117,945 lb (53 500 kg), maximum and normal useful loads remaining unchanged. Cruising speeds have been reduced marginally to 466-503 mph (750--810 km/h), and range with max payload has been reduced to 559 mls (900 km) at 478 mph (770 km/h) at 29,530 ft (9000 m). Ranges with 23,148-lb/10500-kg and 14,330-lb/6500-kg payloads are quoted as 1,243 mls (2000 km) and 1,864 mls (3000 km) respectively. The practical life of the Yak-42 is claimed to be 30,000 hours or 30,000 flight cycles over a 15- year period and the service life of its Lotarev D-36 turbofan is 18,000 hours with two major overhauls.
The first series of production aircraft, built to replace some Aeroflot Tu-134, generally similar to SSSR-42303 as exhibited 1977 Paris Air Show. Changes for production included substitution of four-wheel main landing gear bogies for twin-wheel units on prototypes.
The Yak-42 entered service in 1981 as a 100-seat medium range airliner on Aeroflot's scheduled service Moscow-Krasnodar route. An accident in June 1982 caused the type to be grounded until October 1984, the aircraft being drastically redesigned during its temporary withdrawal from service. In 1990 the Yak-42D was introduced, this version having been stretched to include seating for 120 passengers. First exports of the Yak-42 were achieved in 1990, aircraft being sold to Cubana and CAAC.
Yak-42D introduced from second quarter of 1989 and manufactured by Saratov Aviation Plant (SAZ). The Yak-142 transport is a new variant of Yak-42D, featuring mostly US digital avionics and other improvements. Yak-42A and other versions have been produced in small numbers or been proposed.
Power Plant: Three Lotarev D-36 turbofans, 14,320 lb st (6500 kgp) for take-off, with a nominal static rating of 11,015 lb (5000 kg) and a thrust of 3,525 lb (1 600 kg) cruising at Mach 0.75 at 26,245 ft (8000 m)
Max fuel load, 27,090 lb (12 300 kg).
Max. speed: 870 km/h / 541 mph
Typical cruising speed, 510 mph (820 km/h) at 25,000 ft (7600 m)
Take-off distance, 4,920 ft (1 500 m) at ISA and 5,900 ft (1 800 m) at ISA plus 15 deg C
Landing distance r, 5,900 ft (1 800 m)
Range with max fuel, 1,520 mls (2450 km)
Range with max payload, 620 mls (1000 km)
Range with 26,430-lb (12 000-kg) payload, 1,150 mls (1 850 km).
Typical empty weight, 63,788 lb (28 960 kg)
Max payload, 31,938 lb (14500 kg)
Max fuel, 27,090 lb (12 300 kg)
Max take-off, 114,540 lb (52000 kg)
Wing span, 112 ft 2.5 in (34,20 m)
Length, 119 ft 4 in (36,38 m)
Height, 32 ft 3 in (9,83 m)
Wing area, 1,615 sq ft (150 sq.m)
Undercarriage track, 18 ft 6 in (5,63 m)
Wheelbase, 48 ft 5.5 in (14.776 m)
Accommodation: max high density, 120 six abreast at 32-in (81-cm) seat pitch.