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Aviation History
1990
1990 - 2487.PDF
away from its licence-builder image forever. It admits that a 60-helicopter commitment hardly justifies development of a brand-new- machine. The company can reasonably claim to have come cut of the programme well, however with 70% of the $200 million development: costs borne h' the Government. Many of the technologies in the A. 129 are applicable to civil helicopters, and the fact that the Mangusta left the drawing beard and proved itself more than equal to the original specifications guaran tees Agustas place in the big league of helicopter manufacturers The goals were very ambitious.' says A 129 product manager Giuseppe Virtuani, adding: "We decided that to have a compet itive product we would need to introduce (he most modern technology to meet the sever: military requirement, and bung Agusta up to'the state-of-the-art." ; REDUCING RISK The only risk- and cost-reduci imposed by the Army was that the A. 129 should use an off-the-shelf engine, and weapons — but it should be able to accommodate new equipment, such as a mast-mounted sight (MMS), as it became either available, or affordable. The only readily available engine at the time was the Rolls-Royce Gem turboshaft. The three-shaft Gem, considered very ad vanced back in the 1970s, is described by Virtuani as an "...honest engine, without which there would be no A. 129". There is no doubt, however, that it lacks the reliabil ity and thrust-to-weight ratio of the 1980s' technology LHTEC T800 powering the A. 129 International now being offered for export. The 615kW Gem 1004 gives the helicopter plenty of power, however, and Rolls-Royce has made strenuous efforts to improve reliability. Probably the most revolutionary develop ment seen in the Mangusta lies in its rotor system. While carrying out a series of signature tests on an A. 109 to determine the Doppler radar return from a rotor, Virtuani says: "We noticed that during hover, far the strongest return came from the control rods running between the upper swash plate and the rotor." This led to the idea of enclosing the rotor control rods within a wide-diameter rotor shaft. The shaft would also protect the rods from ballistic damage and, by virtue of its width, would be better suited for carrying an MMS. The design is also aesthetically pleasing, since it leaves the A.129 with a * particularly uncluttered rotor head. The A. 129 rotor is designed, like the rest of the helicopter, to survive a single 12.7mm high-explosive hit, and, in Virtu- ani's words, to have the "maximum proba bility" of surviving a 23mm hit. An innova tion claimed by Agusta is that the A. 129 has the only articulated rotor with a single elastomeric bearing for each blade — an idea which helps reduce the parts count of the rotor system by two-thirds compared with that of tin- A109. The rotor system requires no lubrication. Blades are built around a glass-reinforced plastic (GRP) spar, with a nomex core, and upper and lowei carbon fibre reinforced plastic tCFRP) sums. They will be repaira ble in the field, says Virtuani A purpose- designed MMS, based on the Apache target acquisition and designation system (TAD'1) has been designed by Martin. Marietta, and tried in mockup form There arc no plans to lit an MMS (o production machines. howevei . The A. 129 is agile — Apache pilots who have flown the machine have been ...very impressed", says Virtuani. The principal reason is the relatively high, rotor hinge offset of s in the same league as that of one of the two LH competitors. Hinge offset is a measure of the "leverage" a rotor can provide in forcing a helicopter to change direction. The further away from the hub the blade is hinged, the more leverage — and hence manoeuvrability — there is. The trade-off is the greater diffi culty of designing a rotor system with the hinges distant from the mast. Agusta points out that the A. 129 makes no pretensions to being a "stealth" heli copter. Like the US Army LH, however, signature reduction is taken seriously — although not to the extent of the LH, with its conformal weapons bay, retracting un dercarriage and other features. Probably the A.129's best defence against radar detection is thai it is quite small, the tandem seating arrangement yielding the lowest possible frontal area. Radar warning receivers are also fitted, along with the usual chaff/flare dispensers and radar and mfra-red'jpmmers. ' • , : ' : '.. •'• /;*; ' A. 129 crashvvorthiness requirements orig inally called for ;he same specifications as those of the US Army — the machine had to survive a 12.8m's vertical descent rate with a 95% likelihood of crew survivability. This has now beer, reduced to a l!.lm/s rate, saving about 29% in subsystem weigh!. In a crash, the two-stage, fixed landing gear absorbs 60% of the kinetic energy. The fuselage lower section then begins to col lapse, the idea being to protect, the rotor pylori and gearbox from damage, and pre vent possible extensive further damage to helicopter and crew. Martin-Baker energy- absorbing seats take care of the remaining vertical energy. The pilot's centre-mounted cyclic control stick is attached to the seat to prevent injury during a crash. The co-pilot/gunner's cyclic stick is side- mounted to leave room for the central viewing tube through which he views tar gets by direct optics or forward-looking infra-red (FLIR). Both sticks are connected mechanically with the flight controls via wide-diameter composite tubes. The A. 129 has a backup fly-by-wire control system because, says Virtuani, "...the fly-by-wire technology was not advanced enough when we came to design the system". It is not yet working in the helicopter. "We'll flight test it in two or Agusta A129 Mangusta FLIGHT INTERNATIONAL 29 August-4 September 1990 35
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