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Aviation History
1989
1989 - 0024.PDF
composite airframe is being readied for a tensile test to destruction. This programme, costing around $12 million, is described by MBB as "a poor man's Acap", referring to the US advanced composite airframe programme. The prototype "all-composite" BK.117 will be 50kg lighter than its conven tional counterpart, according to MBB, but a production version would realise a weight saving equal to the weight of one passenger. Instruments in the BO. 108 are of conventional design within a modern ergonomically designed cockpit. MBB is studying the feasibility of an advanced cock pit design with two 5|in x 5 in LCD flat- screen displays, one for primary flight instru ments and the other for navigation and systems management information. With a take-off weight of 2,400kg and an empty weight of 1,225kg, the first prototype BO. 108 is powered by two Allison 250-C20R engines developed from the earlier C20B. A range of 800km is attainable with standard fuel. A cruise speed of 270km/ hr and a hover ceiling of 5,000m are included in the BO.108's specification. Powerplant possibilities The main reason cited by MBB for choosing the Allison C20-R for the BO.108 was that it was already available, and would thus avoid delays in the programme or engine-related development risk. The engine compartment in the BO. 108 has sufficient volume to allow installation of other engines. Pratt & Whit ney's PW205B/1 and Turbomeca's TM319 are new engines which would both suit the BO. 108 should MBB decide to put the helicopter into production as a BO. 105 replacement. The Pratt & Whitney engine is already involved in a test programme in Canada in the BO.105LS. It is being consid ered by MBB to power the second prototype BO. 108, which is under construction and will be completed in mid-1989. Both the Turbomeca and the Pratt & Whitney engines have distinct advantages over the Allison powerplant, namely large growth potential and electronic control. Since its first hover flight on October 15, 1988, the BO. 108 has achieved transition into forward flight and speeds up to 255km/hr. The demonstrator programme is certainly well advanced, and the aircraft embodies much of the technology which must be proved before a new breed of more economical, more comfortable, and- more efficient helicopters can become a reality. The question of whether the BO. 108 goes into production at a later date is really of secondary importance to a programme which arose out of a need to bring a variety of advanced features together into a single aircraft. MBB will be in no rush to do this, for two reasons. Firstly, BO. 105 sales could be adversely affected by a production BO. 108, and, secondly, all ministry funding for the project would have to be repaid (to date this amounts to more than $34 million). E Military programmes dominate Europe Aerospatiale has fared better than most European helicopter manufacturers in recent years thanks to continuing export sales of its Ecureuil, Dauphin, and Super Puma machines. Now the French company is discussing with MBB the possibility of merging their helicopter businesses in an effort to chal lenge Sikorsky for number one position in the world. Aerospatiale's major efforts over the past few years have been in developing military versions of its established range of helicop ters. The five-seat Ecureuil has spawned light-attack and anti-ship versions, as has the larger 12/14-seat Dauphin. Most recently the French company has produced the SA.356M, a military multi- role variant of the Dauphin powered by two 910 s.h.p. Turbomeca TM333 turboshafts in place of the original 724 s.h.p. Turbomeca Arriels. The 1,200 s.h.p. Allison/Garrett T800 will fly in the Panther later this year. Panther improvements which could find application in the commercial Dauphin include the increased-efficiency fenestron "fan-in-fin" anti-torque tail rotor. Aero spatiale is to test-fly a single-turbine AS.350 Ecureuil with a scaled-down fenestron, but is not yet convinced that anti-torque will prove cost-effective on smaller helicopters. Much of Aerospatiale's research and development effort has been directed towards the much larger Super Puma. This includes development of a new low- maintenance main rotor hub. Making extensive use of elastomeric bearings, the new Spheriflex hub is both lighter and simpler than its predecessor. On the Super Puma Mk II, the Spheri flex hub will be combined with new, longer rotor blades with parabolic tips designed to increase lift while reducing drag. The Super Puma Mkll will also feature a new electronic cockpit and digital avionics. Agusta, in common with Aerospatiale, diverted resources to developing military derivatives of established designs when the commercial market slumped. The Italian company's principal products are the multirole A. 109 Mkll and the anti-tank A. 129. Now the company plans to develop a utility version of the A. 129 in co operation with Fama of Argentina. This will be larger than the existing A. 109. The company's other major project is the EH Industries EH. 101, which it is devel oping in co-operation with Westland Heli copters of the UK. In commercial form, the triple-turbine EH. 101 is a 30-seat helicop ter suitable for offshore and commuter use. Other than with the EH.101, Westland has virtually dropped out of the commer cial helicopter business. Now essentially dormant, the Westland 30 programme culminated in the -300 variant with General Electric CT7 turbo- shafts, five-blade main rotor with advanced composite blades, and sophisticated vibration elimination and health and usage monitoring techniques. A feature of both the EH.101 and the Westland 30-300 are the so-called "Berp" rotor blades—named after the British experimental rotor programme which produced them. These blades feature distinctive broadchord tips which are shaped to allow use of highly cambered blade aerofoils to increase rotor lift. Looking ahead, military- programmes will continue to dominate European heli copter development and production into the next century. One commercial initiative is the Euro pean future advanced rotorcraft (Eurofar), a programme to develop a civil tilt-rotor aircraft for service next century. MBB's BO.108 made its first hover flight on October 15, IS 22 FLIGHT INTERNATIONAL, 7 January 1989
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