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Aviation History
1962
1962 - 0155.PDF
FLIGHT International, 1 February 1962 157 Avro 748MF •:'.f*SHait"- L\ST Friday A. V. Roe & Co announced the Avro 748MF ' military freighter, which has leapt into the limelight as a contender to meet the RAF Operational Requirement to provide tactical airlift in support of the Army. It was in June 1959 that the company concluded a licence agree ment with the Indian Government, under the terms of which the Indian Air Force at Kanpur are producing the 748 (the first flew there last November) and have the right to make possible variants. The first military derivative was the high-wing 758, which was followed by the 748M. It was the former which was tendered last July to meet the British OR, in competition with the Caribou and HP. 124; but by this time the successful fatigue-testing, flight development and promise of future growth of the civil 748 had led Avro to believe that the requirement could be met by an aeroplane less extensively redesigned, and the result is the 748 MF. Compared with the current airliner it introduces the following features: Rolls-Royce Dart RDa.12 engines; a completely new rear fuselage and modified tail; local strengthening to permit operation at increased power and much greater weight; and a new freight floor and provision for three-crew operation (the two last changes having been already designed for the IAF). Another modification, which is not immediately apparent, is that the span has been increased to 101ft 6in. This has been done by extending the centre section, which also makes way for propellers of increased diameter. Another important point is that the tyres are larger than in the civil aircraft, although they retract into the same bays. The tyre pressure chosen is largely a function of prevailing conditions, but recent—satisfactory, and very spectacular—trials from deeply rutted mud at Martlesham Heath have been done with 501b/sq in on the mainwheels and 38 on the nose. Although a low-wing design, the 748MF has a rear ramp matched to truck-bed heights. The latter vary from about 3ft (Land-Rover) to nearly 6ft, and the door-sill height given in the data can be altered—obviously by a variable-length nose leg. Raising the nose also increases the ground clearance under the propellers, which are Dowty-Rotol units much larger than the 12ft model used on the 748 airliner. In such an aircraft 6in of additional propeller diameter means 8001b more payload or 100ft off the field-length. It is logical in a military short-field aircraft to use the most powerful available engines, and the RDa.12 rating could readily be cleared. The engine is physically the same as the RDa.10, and the increased military rating is achieved by slightly raising the turbine-entry temperature, and reducing the time between over hauls below the level which Rolls-Royce would hope to achieve with a commercial powerplant. A military Dart of this general type passed a special-category 25hr test at 3,200 s.h.p. in June 1958. Physical data on the 748MF are given below. Typical loads might include: 48 troops (12,0001b) in aft-facing seats, with their kit-bags stowed above the ramp; 40 paratroops, dropping from the inward- opening doors on each side at the rear; 18 litters, 15 sitting cas ualties and attendants; and the three Land-Rovers illustrated. Avro are going to put the new rear end on one of the 748 proto types, and could fly a genuine 748MF in about 18 months. AVRO 748MF (Two Rolls-Royce Dart RDa.12 turboprops, each rated at 2,995 s.h.p for take-off, driving 14ft 6in propellers) Dimensions Spin, 101ft 6in; length, 78ft; height, 29ft; gross wing area, 846 so, ft; track, 27ft 9in; wheelbase, 23ft 8in; fuselage external diameter, 8ft 9in; internal diameter, 8ft l|in; floor width, 6ft 9iin; headroom on centreline, 6ft 3Jin; usable length of hold, 39ft; usable volume, 1,970 cu ft (1,690, +280 above the ramp); mean height of ramp sill, 4ft 3in; ramp width, 7ft; crew door (forward to port), 48in x 53in; paratroop doors (both sides, aft), 65in x 36in. Weights Gross weight, 46.2861b; max payload, 14.0001b: STOL weight, for unprepared surfaces, 39,4351b. Performance (ISA + 20°C, with full reserves) Payload: range, max range with 14,0001b payload, 200 n.m.; ultimate range with 1,140 Imp gal and no payload, 920 n.m. Prepared-surface mission, with 10,0001b payload, take-off at max weight in 2,600ft field-length, climb at I I4kt e.a.s., cruise at 233kt, descend at I40kt, arrive ac destination 750 n.m. away at 40,1311b, divert 200 n.m. to alternate at I88kt, stand-off 30min at 1,000ft and land at 37,521 lb. STOL mission, with 7,0001b payload. take-off at 39,4351b in 1,500ft field-length, climb at I08kt, cruise at 239kt to point 165 n.m distant, descend at I37kt, land in 1,350ft field-length, unload and pick up new 7,0001b cargo, take-off without refuelling at 37,2251b in 1,300ft field length, climb at I08kt. cruise at 240kt back to base, descend at I37kt and land at 34,9951b in 1,210ft field length. Ground runs, 700ft at 39,4351b on semi-prepared scrub surface at 4,000fc. or about 550ft at sea level; landing at 37,5001b, 950ft at 4,000ft or 820ft at sea level. A makers' general- arrangement drawing for trie Avro 748MF, and (above) sectioned side elevation showing a typi cal air-landed load: three quarter-ton Mk5 Land- Rogers
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