Graham Warwick/SAO JOSE DOS
EMBRAER HAS YET to capitalise on the success of its EMB-120 Brasilia 30-seat regional airliner by bringing a second product to the market. Its first attempt was the 19-seat CBA-123 Vector, a technical success which perished in the airline recession of the early 1990s. Its latest attempt is the EMB-145, a 50-seat regional jet.
This time the Brazilian manufacturer looks set to succeed, if it can deliver the price and performance it has promised. First deliveries of the EMB-145 are scheduled to begin in late 1996 - more than three years later than originally planned - but the delays have allowed the regional-jet market to mature, and airlines are now eager for an aircraft such as the EMB-145. The price has increased a little over those three years, to $14.5 million, but the aircraft is still keenly priced.
Price has been a major factor in the success of the EMB-120, with more than 270 delivered to airlines worldwide. Embraer expects the EMB-145 to be competitive with both the similarly priced Saab 2000 high-speed turboprop and the more-expensive Canadair Regional Jet, and says that it will offer lower operating costs than either aircraft on both 370km (200nm) hub-feeder and 1,100km hub-bypass missions.
When the EMB-145 project was announced at the June 1989 Paris air show, the first flight was planned for late 1991 and first deliveries for mid-1993. The definitive rear-engined configuration was not unveiled until January 1992, however, and the programme was further delayed by the prolonged process of privatising Embraer, finally completed in December 1994. The first flight took place on 11 August, and certification and first deliveries are now planned for late 1996.
Although Embraer decided in January 1992 to proceed with the programme, its financial problems meant that it did not have the resources to proceed alone. So it embarked on a search for risk-sharing partners. As a result, the estimated $300 million development cost is being divided between Embraer (34%), risk-sharing partners (33%) and participating suppliers (10%), with the balance being provided in the form of long-term loans from Brazilian development-funding institutions.
DESIGN EVOLUTION
Embraer's risk-sharing partners are Gamesa of Spain, providing the wing, wing-fuselage fairing, main landing-gear doors and nacelles (subcontracted to International Nacelle Systems); Sonaca of Belgium, supplying centre- and rear-fuselage sections, doors, engine pylons and wing leading-edges (with Gamesa); Enaer of Chile, providing the vertical and horizontal stabilisers and elevators; and the USA's C&D Interiors, supplying the passenger-cabin and baggage-compartment interiors.
Embraer's original concept was for an aircraft with engines mounted over a straight wing. This design offered the maximum commonality with the EMB-120, and therefore the minimum development cost, but proved not to provide the desired performance. The aircraft was redesigned with engines mounted under a swept wing, but the high ground-clearance required created ground-handling problems.
The final design, combining a swept wing with tail-mounted engines, still allowed used of the EMB-120 nose and cabin cross-section, and proved to exceed the desired performance. After windtunnel tests at Boeing in late 1993, Embraer reduced the take-off and landing distance figures, decreasing or eliminating operating restrictions at hot-and-high airports.
The swept wing lacks the winglets originally planned for the EMB-145, and has a supercritical-section aerofoil evolved from that developed by Embraer for the CBA-123. There are two flap sections and two spoiler panels per side, but no leading-edge devices. Vortillons under the outboard section of each leading edge control airflow over the ailerons at high angle-of-attack.
Gamesa builds the wing in two sections, left and right, which attach to an Embraer-produced wing stub mounted under the fuselage. Each wing half has two main spars and an auxiliary rear spar, inboard of the trailing-edge break, to support the landing gear. All fuel is housed in the wing, in integral tanks running from the roots to inboard of the ailerons.
The wing stub consists of the carry-through structure and main-gear wheel-well and is enclosed in a glassfibre-reinforced-plastic/honeycomb wing-fuselage fairing. Forward of the wing, this fairing houses air-conditioning packs and the pressure-refuelling point, while the hydraulic packs are located aft. There are no wheel doors - instead, brushes seal against the exposed tyres.
Embraer essentially stretched the EMB-120 fuselage by 9.2m and mounted it on the new wing to create the EMB-145. "The fuselage concept is similar to that of the Brasilia; 30% of the parts are the same and the nose is built on the same tooling," says senior vice-president, engineering, Luiz Carlos Affonso.
Centre fuselage
The constant-section centre fuselage is produced in four pieces. The forward section, including the main door, is supplied by Sonaca, while the other three are produced by Embraer. The rear fuselage is two pieces. The forward section, including engine pylons and baggage door, is supplied by Sonaca, while the aft section, to which the Enaer-built tail is attached, is produced by Embraer.
Cabin width, at 2.1m, is identical to that of the EMB-120, but height has been increased to 1.82m by dropping the aisle by 60mm. Three-abreast seating (two plus one) at 790mm pitch results in six more seat-rows than in the EMB-120. Overhead bins with a total capacity of 1.9m3 (67ft3) and 288kg, are provided on the right side of the fuselage only. There is a full-width lavatory aft, and a galley area with service door on the forward right-hand side of the cabin.
Compared with the EMB-120, an increased pressure differential of 0.54bar (7.8lb/in2) provides an 8,000ft (2,440m) cabin altitude at the EMB-145's higher, 37,000ft, service ceiling. The engine inlets are just aft of the final seat-row and Embraer is predicting a maximum take-off noise-level of 80dBA at the rear of the cabin and an average cruise noise-level throughout the cabin of less than 76dBA.
C&D Interiors is responsible for the complete outfitting of the cabin and baggage compartment, including passenger, flight-attendant and cockpit-observer seats, overhead passenger-service units and baggage bins, and sidewall panels. The baggage compartment has a capacity of 9.2m3 and 1,000kg, with access through a 1 x 1.1m inward-opening plug-type door below the left-engine pylon.
Structurally, the EMB-145 is conventional. The basic structure is aluminium, with chemical milling used extensively to reduce weight. Wing skins and spars are machined. Fuselage skins are produced by stretching clad aluminium sheet - as with the EMB-120, the standard external finish is polished aluminium. Titanium straps are used for damage tolerance. Three forged frames support the wing-fuselage attachment.
All wing control-surfaces - ailerons, spoilers and flaps - are of carbonfibre-reinforced plastic. Landing-gear doors and the upper skin on main-gear wheel well are also made from carbonfibre. Glassfibre-reinforced plastic is used for the wing-fuselage fairing, cabin sidewalls and elsewhere. The fin fillet, leading-edge and cap are made from impact-resistant Kevlar composite. Cockpit, cabin and baggage-compartment floors are a sandwich of carbonfibre or glassfibre-reinforced plastic and Nomex honeycomb.
The parts count is reduced compared to the EMB-120, says Affonso. "There are more machined parts in the wing, because of the machining resources available in Spain," he says, adding that Embraer intends to improve its manufacturing capabilities for the production phase. Automatic riveting will be introduced, he says, and applied to the EMB-120 also.
ADVANTAGE ALLISON
Engine technology is key to producing a regional jet with the price and performance sought by Embraer. The Allison AE3007 was first selected to power the EMB-145 in March 1990. Embraer re-affirmed its choice in July 1992 after a re-evaluation of the engines available and after the AE3007 had been chosen for Cessna's Citation X high-speed business jet.
Rated at 33,2kN (7,476lb) maximum take-off thrust for the EMB-145, the AE3007 uses the core of the T406 turboshaft powering the Bell Boeing V-22 tilt-rotor and the AE2100 turboprop powering the Saab 2000, IPTN N-250 and Lockheed Martin C-130J. This high-pressure core is mated to a low-pressure system consisting of a wide-chord fan and three-stage, uncooled, low-pressure turbine.
The 980mm-diameter fan provides a bypass ratio of 5:1, resulting in reduced noise and fuel consumption. The engine has a full-length, load-bearing, carbonfibre bypass duct and a forced-mixer nozzle. Embraer estimates that the EMB-145 will be a cumulative 20EPNdB below Stage 3 noise levels - and witnesses to the aircraft's first public flight on 18 August can attest to its impressive quietness.
Dual-redundant Lucas full-authority digital engine-control (FADEC) is standard, and provides engine fan-speed control based on thrust-lever setting. Other FADEC functions include automatic engine starting, auto-ignition, and overspeed and overtemperature protection.
Under subcontract to Gamesa, the Shorts/Hurel Dubois joint-venture International Nacelle Systems is responsible for the engine nacelles. Shorts is producing the nacelle structure and Hurel Dubois the exhaust module and optional pivoting-door-type thrust-reverser.
An Auxiliary Power International auxiliary power unit (APU) is standard on the EMB-145 and provides both air and electrical power, both on the ground and in the air. The APU is mounted on a truss structure in the titanium and stainless-steel tailcone. Full-authority electro-mechanical control provides for automatic operation from start-up to shut-down.
AVIONICS ADVANCE
Experience with the CBA-123 has allowed Embraer to take a major step forward in cockpit design from the EMB-120 to the EMB-145. Although it has changed avionics suppliers, lessons learned on the CBA-123 have been applied, Embraer says, and the result is a relatively high-performance, but low-cost, solution.
Honeywell's Primus 1000 system for the EMB-145 consists of dual integrated avionics-computers (IACs) driving five 200 x 180mm cathode-ray-tube displays. The IACs also perform the functions of dual flight-director, single-channel autopilot, and engine-indication and crew-alerting system (EICAS).
Primary-flight and multi-function displays are provided for both pilots, with the EICAS display located centrally. The multi-function displays are primarily dedicated to navigation, but can also present weather radar and traffic advisories. These screens act as back-ups to the adjacent primary-flight and EICAS displays in the event of a failure.
The standard avionics suite includes dual radio-management units, through which the integrated communication/navigation/identification systems are controlled. Also standard are dual digital air-data computers and dual fibre-optic-gyro attitude/heading-reference systems, plus a TCAS II traffic-alert and collision-avoidance system and a ground-proximity warning system with windshear-detection function.
Options include a flight-management system (FMS), a global-positioning system (GPS), or an integrated FMS/GPS. The autopilot/flight-director will be certificated for Category I operations, with Cat II as an option, and Embraer plans to offer optional Cat IIIa low-visibility landing capability using a head-up display.
Switzerland's Vibrometer is developing the central maintenance-computer and engine vibration-monitoring system. Maintenance messages will be displayed on the cockpit multi-function display and both maintenance and engine data will be able to be downloaded to a personal computer for analysis.
SYSTEMS COMMONALITY
Since the majority of EMB-145 customers are expected to be existing EMB-120 operators, Embraer's goal has been to maximise the commonality in systems-design philosophy between the two aircraft, to simplify training and troubleshooting. Changes have been made where demanded by the EMB-145's greater performance or allowed by advances in technology, such as in engines and avionics.
An example is the flight controls. Ailerons, mechanically actuated on the EMB-120, are hydraulically powered in the EMB-145. This is because of the aft loading on the supercritical wing, Affonso says, and because the decision to have large flaps resulted in small ailerons, requiring large deflections.
The hydraulically actuated two-segment rudder is essentially unchanged, with the trailing segment geared to deflectat a greater rate than the main rudder, to increase effectiveness. Elevators are mechanically actuated, as on the EMB-120.
For pitch trim, an electrically driven, variable-incidence, horizontal stabiliser replaces the fixed surface used on the EMB-120. Spoilers are hydraulically actuated, the outboard panels acting as speedbrakes and all four panels being used as ground spoilers. Flaps, hydraulically powered on the EMB-120, are electrically actuated on the EMB-145.
There are two independent, 207-bar, hydraulic systems, each with a primary engine-driven and back-up electric pump. Electrical power is provided by four engine-driven generators (two per engine), an APU starter/generator, two nickel-cadmium batteries and a back-up lead-acid battery. There are three submerged electrical boost pumps in each of the two 2,620litre, wing fuel-tanks.
Bleed-air anti-icing is used on the wing and horizontal-stabiliser leading-edges and engine air-inlets, replacing the pneumatic boots used on the EMB-120. The Hamilton Standard environmental-control system consists of two high-capacity air-cycle machines and mixes fresh (bleed) and recirculated air. Cabin pressure is digitally controlled.
Embraer's equipment division, EDE, designed the landing gear, with assistance from Germany's Leibherr Aero Technik. EDE produces the dual-wheel, trailing-arm, main gear, while Leibherr supplies the dual-wheel nose gear. BFGoodrich provides the wheels and multi-disc carbon brakes; Crane Hydro-Aire, the digital "brake-by-wire" anti-skid braking system; and Parker Hannifin, the "steer-by-wire" nosewheel steering system.
PRIVATE-SECTOR PROJECT
Embraer was privatised by the Brazilian Government in December 1994 and the EMB-145 is its first project as a private-sector company. The manufacturer has already cut its workforce substantially to reduce costs and president Juarez Wanderley says that Embraer's new shareholders have undertaken to pump sufficient capital into the company to fund production of the EMB-145.
Aircraft are being built from the outset on production tooling. The EMB-145 was designed entirely on the Intergraph computer-aided design system, first used on the CBA-123 project, but marked Embraer's first use of an electronic mock-up. "This saved a lot of time and the assembly of parts was surprisingly correct," Affonso says.
The prototype will be followed by three pre-series aircraft and two ground-test articles. A 13-month, 1,300h, flight-test programme is planned, leading to Brazilian and US certification in October 1996. European certification is also planned for October 1996, although Affonso admits this might be "a struggle".
First deliveries are scheduled for December 1996, with the initial four aircraft destined for Australia's Flight West Airlines, Regional of France, Denmark's Eastern Trade Wings, and Trinidad-based BWIA International Airlines. By the time of the first flight in August, Embraer held firm orders for 18 aircraft, options on 16 and letters of intent for 127.
Embraer and its partners are gearing up for production of three aircraft a month by 1998, but could increase this to four a month "...if the market demands", says senior vice-president, programmes, Satoshi Yakota.
The Brazilian manufacturer is counting on continued regional-airline growth, coupled with increased demand for jet-airliner service, to generate demand for at least 400 EMB-145s. Its break-even point is between 200 and 250 aircraft, which the company expects to reach between 2001 and 2003, he says.
Source: Flight International
