#24
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por faterra » Seg Jan 19, 2009 8:42 pm
The Ilyushin Il-78 (NATO reporting name Midas) is a four-engined aerial refueling tanker based on the Il-76
The Il-76 tanker was conceived as long ago as 1968, but the transferable fuel load for the initial version was only 10 tonnes, which was insufficient, and development was shelved. When the higher performance Il-76 became available, the tanker project was re-started, as the Il-78, in 1982. In addition to the increased fuel load of the late model Il-76, the Il-78 has two, removeable, 18,230 litre fuel tanks installed in the freight hold, giving a transferable load of 85,720 kg(188,584 lb) with hold tanks and 57,720 kg(126,984 lb) without hold tanks. Controlled from the Gunners cockpit, which is stripped of military equipment, three aircraft may refuel in flight, simultaneously, from the UPAZ-1A (Il-78) / UPAZ-1M (Il-78M) refuelling pods fitted to the outer wings and rear fuselage. In addition four aircraft can also be refuelled on the ground using conventional refuelling hoses extending from the freight hold. Due to the high weights after take-off, which, in an emergency, would mean landing at weights well in excess of maximum allowable landing weight, the Il-78 has a fuel jettison system, with jettison ports at the wingtips.
Soon after the Il-78 passed acceptance tests, in 1984, Ilyushin were instructed to design and produce an upgraded version to be known as Il-78M. The Il-78M is a dedicated tanker and cannot be converted back to the transport role easily. Adding a third freight hold tank increases the transferrable fuel to 105,720kg(233,070lb),and the Maximum Take-Off Weight (MTOW) to 210,000 kg,which required the wing torsion box to be strengthened. Fitted with the improved UPAZ-1M refuelling pods, the maximum fuel flow was increased to 2,340 litres/min (514.8 Imp gal/min). Because the Il-78M is not "convertible" all cargo handling equipment is removed and cargo doors deleted, saving approximately 5,000kg in structural weight.
Early versions of the Il-78 have the fuselage pod mounted on a short horizontal pylon, but the Il-78M has the fuselage pod suspended from an identical pylon to the wing pods, attached to a short stub wing, this modification was carried out to isolate the pod from turbulence generated by the fuselage, with the added benefit of commonality with the wing pod/pylon combination. Il-78's were produced with Aeroflot colours and civilian registrations, but production Il-78M's received military markings, registration and colour scheme.
The majority of the twenty Il-78 aircraft on the strength of the Ukrainian Air Force have been permanently converted to pure transports by removal of freight hold tanks and refuelling equipment.
Variants
Il-78 - The Il-78 was the original production version with two removable fuselage tanks, giving a maximum transferable load of 85.72 tonnes(188,540 lb).
Il-78T - Alternative designation for Il-78 due to retention of all cargo handling equipment and convertible freight hold.
Il-78M - The Il-78M entered service in 1987 as a dedicated tanker equipped with three permanent fuselage tanks, a higher gross weight of 210 tons, and no cargo door or cargo handling equipment, the cargo ramp is retained but non-functional. The total fuel capacity of the Il-78M is 138 tonnes(303,600 lb), of which 105.7 tonnes(232,540 lb) is transferable.[1]
Il-78ME - Export version of Il-78M
Um abraço!
Fernando Augusto Terra
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