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Aviation History
2003
2003 - 1096.PDF
Cover story CHOICES Embraer made bold decisions on the 170's fuselage design, wing size and engine. With the huge changes in the regional market, have these choices proved wise? PAUL LEWIS / SAO JOSE DOS CAMPOS hen Embraer began consider ing a new 70-seat aircraft to follow its successful ERJ-145 in 1998, it faced three imme diate and fundamental ques tions that would shape the programme's future. The Brazilian manufacturer had to decide on a fuselage cross-section, wing size and powerplant at a time when the regional airline industry looked a lot differ ent than it does now. Through foresight and good fortune, its choices have proved flexible and adaptable enough to evolve into today's Embraer 170/175 and 190/195 family of four aircraft. Among the first pre-design concepts explored was a derivative of the ERJ-145's low wing and rear engine mount configu ration, but going from a three- to a four- abreast cabin. This was ruled out on the grounds that it was too marginal a design in terms of performance and capacity. A more efficient solution from an engineer ing and operational standpoint was an all- new design incorporating underwing- mounted engines built around either a four-abreast fuselage or, like the rival Fairchild Dornier 728JET, a five-abreast cross-section. "We took the two aircraft to the airlines and the result was the adoption of the Differences between the 170/175 and 190/195 focus on the wing, engine and landing gear four-abreast," says Luis Carlos Affonso, Embraer 170/190 programme director. "I think it was the right decision and confir mation came at last year's Farnborough air show, when we showed not a normal four- abreast but a new double-bubble four- abreast fuselage. It has the same comfort level as a larger jet, but no middle seat. The response from the mainline carriers was very positive." Robust family The response reflects the shift in emphasis since 1998 away from a product geared solely to the regional airline market to a more robust family design with equal appeal to traditional mainline carriers. At the urging of launch customer Crossair - now Swiss International Air Lines - the 195 version was added, stretching the maxi mum design capacity to 110 seats. By the end of the joint definition phase in March 2000, overall cabin volume had increased and greater flexibility was incorporated into the design to offer a wider range of seat, galley and toilet layouts. The double bubble was chosen rather than a cylindrical shape. This has enabled Embraer to design a four-abreast cross-sec tion, offering up to 2m (6.5ft) interior headroom, plus a 0.94m-high underfloor baggage hold, and lay claim to greater cabin volume per seat than the rival Bombardier CRJ700/900 or even the Airbus A320 series. The drawback is a more com plex pressure vessel that has required struc tural strengthening and added some weight. To mitigate risk, a fuselage barrel has already completed 320,000h of fatigue testing - four times the 170's design life. Today, Embraer is offering operators four pre-designed configurations, with the base line 170 accommodating from 70 seats at 32in (81cm) pitch up to 78 seats at 30in pitch, and either a 42+28-seat, 33/31in pitch mixed-class or 6+60-seat, 36/3 lin pitch dual-class layout with a three-abreast business section. The 190 with the same pitch options will seat between 98 and 108 in a single class, 58+40 in mixed or 8+86 in a two-class plan. The 195, again based on a similar pitch, is designed to hold between 108 and 118 seats in single, 58+40 in mixed and 8+86 in dual class. The 175 was the fourth member to join the family in 2001 which, thanks to the addition of 83.8cm forward and 93.9cm aft plugs, will accommodate two more rows of seats. The aircraft was added to better counter the now-stillborn 728JET and new CRJ900 stretch. The 175 will accommodate 78 seats at 32in pitch, or can match the 86- seat CRJ900 in a 31in-pitch layout. The air craft could have been stretched further to close the gap with the larger winged 190/195, but this would have further eroded payload/range performance. "There is no perceived demand to fill that gap currently," says Satoshi Yokota, Embraer executive vice-president indus trial. "Technically it can be done if some one comes up with a scope clause limit of 85 seats one day and says he'll order 100 if we make an 85-seater." Embraer's other option is to remove about the same amount of fuselage from the basic 170 as was added to the 175 and produce a 60- seater version, but again the company says there are no plans on the table to do so. Embraer's two other major design deci sions centred on the choice of engine and the sizing of the wing. Prospective opera tors had been pressing the company for a choice of powerplant, but the need to enlist risk-sharing partners drove Embraer to enter into a sole-source business agree ment with General Electric for the CF34. The company has elected to go with two different baseline versions of the engine, the CF34-8E for the 170/175 with a range of different take-off thrust ratings up to a maximum of 14,2001b (63kN), and the CF34-10E for the 190/195 rated at up to 18,5001b thrust. The latter is essentially a new engine, incorporating a larger 53in diameter wide chord fan and new nacelle from Goodrich in place of Aermacchi/Hurel Hispano design on the -8E. The -10E draws heavily on GE's existing powerplant technology, including CF6 composite swept and leaned outer guide vanes and fan blade retention, the CFM56's high-pressure compressor aerodynamics, single-stage high-pressure turbine, single annular combustor and the CF34-8's four-stage low-pressure turbine and full authority digital engine control. To preserve the 170's 3,430km (l,850nm) range and accommodate the 195's heavier operating empty weight (OEW) of 28,970kg (63,8601b), versus the 56 13-19 MAY 2003 FLIGHT INTERNATIONAL www.flightinternational.com
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