Embraer's 170 filled a niche for large regional jets. Can its bigger sibling, the 190, making its air show debut at Farnborough, satisfy the 100-seat-plus sector?
If you had asked anyone at the 1994 Farnborough air show to predict which company would be bringing an advanced, fly-by-wire, 100-seat airliner to the 2004 show, almost certainly the answer would have been Airbus, Boeing or even perhaps McDonnell Douglas (MDC).
But no one would have said Embraer, the relatively small Brazilian manufacturer which, in September 1994, was still more than a year away from the delayed first flight of its 50-seater ERJ-145 regional jet. Back then, the newest 100-seater on the horizon was the MDC MD-95, with the company receiving launch authority from its board only two months before the 1994 show.
But 10 years can be a long time in aerospace. Embraer is now one of the largest civil aircraft manufacturers in the world. More than 800 ERJ-145-family jets have been delivered, and the first of the latest-generation Embraer 170 large regional jets are entering service after a prolonged and sometimes painful birth. The MD-95, meanwhile, is being produced as the Boeing 717 following the company's 1997 takeover of MDC, and has been fighting for sales in a tough market against competition from the Airbus A318. The samedifficult market ended production of earlier-generation 100-seaters such as the British Aerospace BAe146/Avro RJ family and Fokker 100, and it is only in the past two or three years that the long-hoped-for potential of this sector appears to have been coming to life.
Growing gap
Launched into a much more uncertain future in 1999, Embraer's 170/190 new large regional-jet family was aimed at what the company saw as a growing gap in the 70- to 110-seater market. Balanced between the regional and mainline airline worlds, this was the elusive 2,500 aircraft-plus market originally identified by Boeing when it decided to continue with 717 development. Unlike Boeing, however, Embraer had the opportunity to come in with a clean-sheet design and build up to the market, rather than take an existing design and scale down to the 100-seater arena.
By the end of the 1990s, Embraer was also completing development of the main members of the 145 family, particularly the last derivative - the ERJ-135. "After the 135, we thought, what next?" says senior vice-president, engineering and new product development, Luis Carlos Affonso. "Embraer thought there was no specifically designed aircraft for this larger segment, so we launched a family. It benefited regional airlines requiring higher-capacity aircraft as well as bigger airlines that wanted a better match between capacity and demand. The regionals were growing up and the majors were 'right-sizing' their fleets to meet changes in demand."
Target area
Within two years of the launch decision, the dynamics of the market changed virtually overnight after the 11 September terrorist attacks, with regionals growing and majors shrinking capacity towards Embraer's "right size" target area. Also, the dire years since 2001 have seen the continuing erosion of the pilots' scope clauses that for decades prevented the 70- to 110-seat market from taking off in the USA. "I see that being relaxed even more - it's just a matter of time," says Embraer president Mauricio Botelho. "It is, and always has been, an artificial market restriction at the cost of the consumer and it is quite unfair. You see communities in the USA that could be served by air that are not because of this - so the consumer is paying the bill."
Embraer's 170/190 family has also survived while direct competitors the Bombardier BRJ-X and the Fairchild Dornier 728JET projects have fallen by the wayside. But even before their demise, the prospect of such fierce competition, as well as the emergence of Bombardier's well-founded CRJ700/900 derivatives, helped push Embraer to new lengths in terms of design drivers. "From day one we were after great passenger comfort and appeal," says Affonso. "For the airlines, we wanted low operating costs, which is the most important aspect today, as well as easy maintenance, flexibility and commonality across the family. Flexibility had to include quick turnaround times and the performance characteristics of a big jet - not a regional jet. This had to climb and cruise like an airliner, and it had to have high maturity at entry into service. Finally, it had to meet or exceed future environmental requirements."
The earliest concepts included stretched and widened ERJ-145 derivatives with tail-mounted engines and a four- or even five-abreast cabin. The configuration's performance and capacity restrictions quickly became apparent, however, and the all-new "mini-737" shape of the current 170/190 was born. The crucial question of cross-section was then solved after consultations with airlines such as Crossair (now Swiss). "The cross-section is one of the most innovative aspects of the design, and we discussed a lot before launch whether to go four or five abreast," says Affonso. "In the end we chose four because it avoids the middle seat - but it is not a typical four-abreast layout. This layout has nothing to do with smaller jets. We wanted to get the same seat width, aisle width and overhead bins that you would find on the big jets."
The result was the adoption of a classic double-bubble cross-section comprising two circular arcs of different radii instead of the structurally more efficient, but restrictive circular shape. The larger of the two arcs forms a 2.74m (9ft) -wide cabin with up to 2m interior headroom, the lower arc provides a 0.94m deep underfloor hold, a fairing joining the two in a smooth-contoured ellipse. Embraer decided the trade-off between simplicity and the structurally more complex and weighty cross-section was worth it from a marketing perspective - a decision that seems to have been justified by the 170/190-family orderbook, which now stands at 258 firm orders and 342 options.
Bigger market
The early success has already prompted changes in the company's 10-year sales forecast for the family, which has risen from 600 in 1999 to "about 920" today, says Affonso. Four basic configurations are offered around this cabin, with the baseline, 29.9m-long 170 offering 70-78 seats and a range of 3,700km (2,000nm), and the slightly larger 31.7m-long 175 carrying between 78 and 86 passengers over ranges up to 3,330km. The stretched 190 is 36.24m long and seats between 96 and 108 on routes up to 4,070km, while the largest member of the family, the 195, is 38.7m long and will fly on routes up to 3,330km with up to 118 passengers. Systems commonality between baseline variants is 85%, and up to 95% between each of the derivative pairs. The result is, at the top end, an aircraft that is longer than the 737-700 and within a metre of the overall length of the -800.
Fly by wire
The aircraft were also to be technically state of the art, with fly-by-wire flight controls to reduce pilot workload, provide automatic structural load protection and compensate for engine thrust asymmetry and configuration changes. They would also have a Honeywell Primus Epic digital avionics suite, an on-board central maintenance computer and CF34-8E/10E turbofans provided by General Electric under an exclusive agreement.
Despite the planning, persistent problems with the avionics and flight control system delayed certification and entry into service of the 170 from December 2002 to March 2004, when Polish flag carrier LOT became the first airline to put it into revenue service. Just five days before its smaller sibling began earning its living, on 12 March 2004 the 190 flew for the first time from the company's Sao Jose dos Campos site. The flight marked the beginning of an all-out effort to certificate the aircraft by August 2005, with the first of up to 100 deliveries to launch customer JetBlue Airways due to follow in September.
Although sharing an identical flightdeck, common type rating and 85% of the systems, the larger 190 is more than a simple stretch of the 170, which, in terms of cabin comfort and overall spaciousness, is described by Embraer as a "trunkliner" rather than a regional jet.
Main changes include a much larger wing, increased-span horizontal stabiliser and more powerful engines, all driven by the decision not to compromise performance for the sake of commonality. "It was a key decision," says director of development and programmes Mauro Kern. "The whole point of making the wing bigger was to have good performance at both ends of the family. If we had designed the same wing for both, it would have been too heavy for the 170 and not optimised for the 190."
The 190's span (with winglets) is 28.72m, 2.72m longer than the 170's, while the wing area increases from 72m2 (775ft2) to 92.5m2. The wing structure consists of a "two-box" wing-stub assembly and outer wings section. The forward wing stub box is made from 7000-series aluminium alloy with integrally machined skin panels, ribs and spars, and the aft wing-stub section is made up of an auxiliary spar to support the main landing gear, and carbon fibre composite top panels. Shrouds are enclosed within the box to protect internal systems and provide noise abatement for the double-wheel set of each Liebherr Aerospace-produced landing gear leg.
The outer wing sections which, like the stub, are assembled by Kawasaki Heavy Industries (KHI) at a new site near Embraer's flight-test centre at Gaviao Peixoto, are also fabricated from 7000-series alloy, with skins made by Vought.
Torsion box
Each comprises a torsion box formed by two main spars, with a third (auxiliary) spar attached at the trailing edge to support the gear. The torsion box, extended into the wing stub with continuous flow through the baffle ribs, provides capacity for up to 16,000 litres (4,220USgal) of fuel - 8,000 litres per side. It takes about 10min to refuel the aircraft at a maximum flow rate of 800 litres/min. The winglets are constructed from three main 7000-series spars, wrapped in 2000-series, chemically milled skin.
The fixed leading edge is also a torsion box made of rib-stiffened skins. Nine pairs of machined ribs on each side provide slat-track support through four main rollers and two side rollers at each track station.
A rack-mounted rotor actuator drives the outer tracks of the four slat surfaces, three outboard of the engine and one inboard. A silicone rubber "P" seal runs along the back side of each slat to aerodynamically seal the gap at the retracted position.
Because the larger wing has greater lift, the composite flaps are slightly different on the 190, with only the inboard section double-slotted, compared with both inboard and outboard on the 170. The outboard section is single-slotted and supported by two stations, while the inboard flap has an additional support mid-span. Located between the main and aft flap panels, this is designed to prevent the aft panel separating after a bird strike.
The wing supports five spoiler panels, made by Hexcel from composite honeycomb with a carbonfibre channel-shaped spar. The two inboard spoilers are for ground operation only, whereas the three outer panels function on the ground and in flight. Hexcel is the predominant composite supplier, providing fairings, leading edges, elevators, landing gear doors and rudders.
Although Embraer originally hoped to retain identically sized horizontal stabilisers, initial 170 flight tests showed that additional span and a 10% increase in area would be required to improve pitch authority when it came to the larger version. "We found this quite late in the 170 flight-test campaign," says Kern. "By then we didn't have time to redesign the 190 units, so they are hybrid 170 stabilisers with added 1m tip sections. They are not therefore fully representative, and the first production-standard unit with added tips and reinforced structure will fly on the third flight test aircraft in July."
The stabiliser is movable and hinged on the rear fuselage structure, the hinge attached at the rearmost of three spars in the main box structure. The unit is trim-actuated through duplicated brackets at the central spar (see box left), while the front spar is interrupted around mid-span to reduce the fuselage cutout and to allow the surface to move. The leading edge is a single fibreglass/Kevlar/Nomex-honeycomb sandwich construction bolted to the stabiliser forward spar.
The vertical fin, which is of conventional construction with three spars, remains unchanged but the aircraft stands slightly taller overall at 10.5m compared with 9.7m for the 170 because of its taller main landing gear. The fin is attached to the fuselage by 24 tension bolts, and lies aft of a small dorsal fin that is also bolted to the fuselage structure.
The 190's longer fuselage structure comprises seven major segments, compared with five on the 170. The Embraer-made nose section remains common, as does the Latecoere-built centre fuselage I section, with a built-in forward cargo compartment door. Aft of this is the first of two plugs (centre fuselage IIA), the second of which (IIB) is aft of the Embraer-made centre fuselage II. The forward plug measures 2.4m and the aft 3.7m. In the next, and final, stretch for the 195, the forward plug length is extended to 3.22m and the aft to 5.32m. The centre fuselage II section incorporates a cutout for the wing stub, but is reinforced by a keel beam. Pressurisation is achieved by mating to the stub, plus the forward and aft pressure bulkheads attached to the stub spars.
The aft common fuselage section (centre fuselage III) is also built by Latecoere and incorporates a cargo door on the lower right side, as well as right and left passenger and service doors. The rear fuselage (built by Gamesa Aeronautica of Spain along with the rest of the empennage) carries a dome-shaped pressure bulkhead constructed from a forged and rolled ring with 10 radial sections, and incorporates a cutout for the horizontal stabiliser. The last frame comprises two separate upper and lower "D" shapes joined by duplicated stabiliser hinge fittings made from 7000-series aluminium and titanium.
Attached to the aft section is the Hamilton Sundstrand-made tail cone containing its APS2300 auxiliary power unit (APU), which provides shaft power to drive a 40kVA AC generator and bleed air for main-engine starting up to 25,000ft. The APU itself can be started up to 30,000ft and operated up to 33,000ft. Three damage-tolerant soft mounts connect the APU to a failsafe attachment system comprised of seven steel rods that connect the powerplant to the fuselage.
Much of the 190 flight testing has focused on the performance of the GE CF34-10E engine, which is essentially a new-centreline 18,500-20,000lb-thrust (82-89kN) design developed specifically for the 90- to 110-passenger market, and as a natural extension of the increasingly common CF34-3 regional jet engine on the CRJ family. "When the requirement for the bigger aircraft came out, we originally proposed a growth version of the -8 [which powers the 170], but the more we looked at it, the more we thought a scale of the CFM56-7 core was a better solution," says GE small commercial engines general manager Chip Blankenship.
Engine development
The decision was obviously the right one, because GE subsequently won the Chinese AVIC ARJ21 engine competition with the-10A version. Along with partners Ishikawajima Harima Heavy Industries, which has 30% of the programme, and Techspace Aero of Belgium, which makes the high-pressure compressor (HPC), GE undertook an aggressive development schedule that called for first flight on its Boeing 747 testbed in November 2003, and flight tests on the 190 in early 2004. The engine has a 1.3m-diameter wide-chord fan, a three-stage low-pressure compressor, nine-stage HPC, single-stage high-pressure turbine and four-stage low-pressure turbine.
"We've got around 2,000h of tests, including more than 1,900h on the ground," says Blankenship, who adds that GE expects to meet its third-quarter 2005 certification target. "We like what we see so far, although we've got the usual types of thing we will change on the first production engines that will come off the line at the end of this year." Configuration changes are expected to concentrate on "ideas for weight reduction and reduced fuel consumption", he adds.
In anticipation of possible higher thrust requirements for the 195 programme, GE has also "done a lot of our testing at the 20,000lb-thrust level, and we liked the results", says Blankenship.
"To have an engine we'd like at a bit higher thrust, however, we would have to change some of the materials. It all comes down to what they want. If they want a bit of growth, we will find the way, but the feedback we're getting so far is that what we have will be OK."
Preparations for the 195 are now in hand, with assembly of the first aircraft due to begin this year and certification targeted for the second quarter of 2006. With the lessons learned from the 170 certification effort, Embraer hopes the 190 programme will lead to an equally smooth 195 certification, and perhaps fresh orders for both this stretch and the 175 variant. Either way, the chances are good that the Brazilian manufacturer will have yet another "first" waiting in the wings for Farnborough 2006.
GUY NORRIS / LOS ANGELES CUTAWAY / TIM BROWN & GIUSEPPE PICARELLA
Source: Flight International
