Peter Henley/SAO JOSE
EMBRAER, IT SEEMS, could not be launching its EMB-145 50-seater at the world's commuter-airline market at a better time. Delays to the programme arising from its privatisation and the search for risk-sharing partners since the announcement of the EMB-145 at the June 1989 Paris air show, have been a frustration to the Brazilian manufacturer, but will now probably work to its advantage.
During these years, the configuration has evolved from the original aircraft, based on the company's successful EMB-120 Brasilia 30-seat regional airliner, to the final design, using a swept wing and tail-mounted engines. Throughout, the philosophy has been to incorporate as much structure as possible from the earlier aircraft to contain development costs. To this end, the EMB-145 uses the EMB-120 nose and cabin cross-section - about 30% of the aeroplane's structure. Embraer is marketing the -145 under the twin slogans of "Back to Basics" and "Everything you need. Nothing you don't".
The thinking behind these catch-phrases is that a regional aircraft should be relatively basic in its design, manufacture, operation and maintenance and, while having no frills, should be equipped to a level which will allow it to be reliable, safe and functional, able to cope with adverse weather, have passenger appeal and earn its owner money.
"Back to Basics" means that the EMB-145 is not an innovative aeroplane: the basic structure is built from chemically etched aluminium with machined wing spars and skin and stretched aluminium-sheet fuselage skin. The ailerons, spoilers and flaps are of carbon-reinforced plastic, as are the landing-gear doors: the fin fillet, leading-edge and cap are of Kevlar composite. There is a tail- mounted auxiliary power unit (APU) providing air and electrical power on the ground and in the air. The engines are Allison AE3007s, rated at 33.2kN (7,475lb) maximum take-off thrust, with a 980mm-diameter fan giving a bypass ratio of 5:1 and, consequently, reduced noise and fuel consumption. (A full technical description of the EMB-145 appeared in Flight International, 18-24 October, 1995.)
Cost advantage
Embraer claims that development costs have not exceeded $300 million, and that the basic EMB-145 will sell for about $15 million, thus making it similarly priced to the Saab 2000 (its most obvious turboprop rival) and cheaper than the Canadair Regional Jet. Lower operating costs than those of both rival aircraft are predicted for the EMB-145 by its manufacturer. For a 50-seat aircraft with a maximum take-off weight (MTOW) of 20,600kg, the EMB-145's fuselage looks remarkably slim to eyes more accustomed to today's widebodies and its bespoke, Embraer-designed, super-critical-sectioned, swept wing looks paradoxically small.
The elegant, tall and slender T-tail provokes reflections about behaviour at and near the stall, as do the vortillons beneath the wing leading-edges ahead of the ailerons to re-energise the airflow over them at high angles of attack (AoA). Also, with a rear-engined configuration, there are the well-known possibilities that disturbed air from the wing root could impede airflow to the rear-mounted engines in the slow-speed, high-AOA, high-engine-power corner of the flight envelope, while the position of the engines well behind the undercarriage wheels could make them vulnerable to water-spray ingestion on a wet runway during take-off or landing.
Embraer's director of commercial programmes and contracts, Satoshi Yokota, says that extensive use of computer-aided design techniques has led to excellent "producibility" of the aircraft, leading to lower building costs than predicted and snag-free compatability between the components made by the different partners. For example, when the first wing (from Gamesa in Spain) was brought up to the fuselage (from Embraer), the 100 precision jig-drilled fixing holes matched exactly. Although, Yokota says, test results from development trials have yet to be verified, early results indicate that the -145 is likely to show about 10% better direct operating costs than those of its rivals under comparable conditions and, for example, speed and fuel consumption is going to be better than design predictions. To date, 22 firm orders, 30 options and nearly 200 letters of intent have been received. Director of engineering Luis Carlos Affonso says that certification is targeted for October 1996 (the Brazilian civil-transport authority, US Federal Aviation Administration and European Joint Aviation Authorities). The first delivery is planned for late November. The proposed production rate is 29 aircraft in 1997, 38 in 1998 and at least 48 a year thereafter.
Affonso also says that market research has shown that more customers would like the Enhanced Range version. (The standard version with a 19,200kg MTOW is not capable of operation with full fuel and full payload, but the Enhanced Range version can operate with full fuel and payload at a MTOW of 20,600kg.)
The -145 has been designed for easy "turn-arounds" at intermediate airport stops and has the servicing and payload points placed about the airframe so that refuelling (through a single point in the forward right-hand wing root), catering, baggage-handling and lavatory servicing can all be accomplished simultaneously without entanglement. Passenger loading is through a single door with rugged built-in steps. Embraer is designing a portable adaptor unit to connect the -145 to a standard airport jet-way. Flight International's visit to Embraer gave the chance not only to test-fly a prototype -145, but also to fly as a passenger on the first fully equipped -145 (see panel, P32). Before the flight, chief test pilot Gilberto Schittini chaired an informal discussion which included Luis Rodrigues, the test pilot with whom I was to fly, and a flight-test engineer. On the aircraft used for the stalling trials, a tail-chute was installed (where the APU would normally live), but all stalls, including the dynamic ones, have been successfully completed without incident other than occasional random wing-drops at the static stall. The presence of the vortillons was also explained: during windtunnel testing in the early stages of design, the need to regenerate airflow over the ailerons at very high angles of attack (high alpha) was identified. The plan had been to verify the need for vortillons by flight-test and to discard them if they proved to be unnecessary. The intensity of the programme to date, however, has made these trials impossible and the decision has therefore been made to retain the vortillons on production -145s. (Vortillons can be a liability because they are of the ideal profile to attract ice, and therefore need anti-ice protection - in the -145 by directing leading-edge anti-icing bleed air over them - and on the ground they can stick into people.) Airframe and engine ice-trials are scheduled for August. Similarly, full water-splash trials are also outstanding. My concerns about the engines ingesting water could therefore not be met with any assurances until after these trials. I noticed that the nosewheels are, meanwhile, fitted with "chined" tyres as a sensible precaution. The row of vortex generators immediately in front of each aileron in the upper wing surface was added after side-slip trials showed adverse yaw, with full aileron deflection being reached significantly before full rudder deflection. Schittini also says that trials have shown undisturbed airflow to the engines at high alpha.
Neat cockpit
The style and ambience of the cockpit are those of a business jet rather than the traditional regional airliner, the compactness giving the occupants that snug-fitting feeling enjoyed by many pilots. This compactness does not, however, mean a cramped cockpit - far from it.
Access to the seats is excellent, room having been found to allow each seat to move fore and aft and, at the rearmost extent of its travel, to slide outwards, in the same way as the seats move about the vastness of a Boeing 747 flightdeck. The seat has adjustments for back angle, lumbar support, thigh support and (electrically) for height. Initial eye position can be established with the usual three balls mounted atop the windscreen centre pillar. Rudder pedal adjustment is by a small switch at the bottom of the instrument panel and an electric motor. Outboard of each seat is a storage bin to hold a standard size flight bag, forward of which are storage for a head set and the crew emergency oxygen mask.
The field of view is good, although, the windscreen pillars are rather wide. Each pilot can see the wing tip on his side of the aircraft - but only by leaning forward and peering aft. Sideways vision becomes impaired by the relatively low curved top edge of the side windows at more than about 30° of bank - not a shortcoming in a regional airliner. Each pilot has a sun visor which can be moved to any position. The large side windows have handles to unlock them and slide them rearwards, but only by about 200mm. In emergency, these side windows can be unlatched using a red knob and withdrawn inwards leaving a reassuringly capacious escape route, survival being enhanced by a rope neatly stowed behind a small panel above the window.
The planned and briefed profile was a climb to 30,000ft, handling, three stalls, a V2 climb at take-off power at 5,000ft QNH, during which an engine would be shut down, an airborne engine relight and, finally, a manually flown instrument-landing-system (ILS) approach for a touch-and-go followed by two visual circuits and a final maximum brake landing without the use of reverse thrust.
The clean, neat but conventional layout of the cockpit is dominated by the five Honeywell Primus 1000 cathode ray tubes (CRTs). The control columns are articulated at about knee level and have "ram's horn" grips. Control of the aircraft's systems is exercised through neat and simple overhead panels beneath the serried ranks of circuit-breakers in the roof panel. The check-list directs attention first to start the APU, which then provides electrical power and air conditioning. Relevant parameters are displayed on the centre 200x180mm CRT which is normally used by the engine instrument and crew-alerting system (EICAS), although displays can be switched between CRTs, particularly to compensate for tube failure.
Aircraft 801 (PT-ZJA) was equipped with racked test equipment, two flight-test engineer or observer stations and 14 interconnected water tanks (for centre-of-gravity adjustment and ballasting), with only the front two being filled. The fuel tanks were full (4,000kg) and the resultant MTOW of 15,450kg (against a maximum of 20,600kg) gave a light, forward-centre-of-gravity configuration. Other flight conditions were airfield altitude 2,000ft (600m), altimeter QNH code 1022, temperature 23°C, surface wind calm and good visibility.
The APU start is initiated by pulling and turning the START knob. Acceleration and temperature are monitored by the EICAS, and any abnormality countered by automatic shut down. The crew-alert system has not yet been finalised, but the hardware is in place: two square, lighted buttons (one red and one amber) are set before each pilot on the glare shield panel - the red signals major failures, the amber minor system faults. Pressing the button cancels the audio warning.
Simultaneously with the alert, a fault legend appears in amber or red letters on the EICAS panel. Assuming that the APU has started successfully, the checklist moves attention to the adjacent engine-start panel and the engines can be started in a similar way - by pulling and turning the start button. All went according to plan, and the EICAS showed the ignition functioning during start and peak start temperatures of 637°C and 634°C inter-turbine temperature against a permitted maximum of 800°C. For development work, a paper checklist is being used, but a customer option will be for checklist display on a CRT. While the EICAS displays current critical information such as engine-oil pressure and temperature, overall system status can be selected for display on the multi-function display (MFD) CRT.
For example, a diagram of the fuselage showing the status of the cabin and baggage doors (locked or unlocked) before engine start and taxi, or the hydraulic, fuel or electrical systems, can be displayed. Selection is made through buttons along the lower edge of the MFD - the CRT inboard of each pilot's primary flight display (PFD). Each PFD presents the pilot with attitude, horizontal situation, airspeed, altitude, vertical speed and traffic-alert and collision-avoidance system (TCAS) warnings.
Taxiing the -145 is easy and pleasant. Releasing the parking brake through the pull-on, push-off T-handle on the captain's side of the centre console allowed the aircraft to roll forward at idle RPM. There is only one nosewheel steering control, and that is entrusted to the captain - on the side panel where it comes readily to hand. Because the steering is designed only for ground manoeuvring, the system has to be activated by pressing down and forward on the small circular control wheel - release it and the nosewheel returns to castoring mode. The wheel brakes are operated by rocking the rudder pedals forward; the system is electrically activated - or "brake-by-wire". The brakes are smooth, progressive and powerful; the nosewheel steering both high-geared and precise. The -145 is designed on the "dark cockpit" principle - if a system is satisfactory, all legends will be out, if it is not satisfactory a crew-alert indication will appear. This principle also allows for a minimum number of check-list items. The pre-take-off checklist, including the configuration check, was completed ready for the departure from Sao Jose. Engine control on the -145 is by full-authority digital engine-control (FADEC), the primary cockpit controls being the throttles (obviously, more properly the thrust levers), and control-mode buttons for engine start/stop and take-off data setting.
The choice of condition for take-off is maximum take-off (full power rating) or alternate take-off (92% of full power). For maximum engine life, the alternate mode would normally be used, if possible. With this mode selected, an engine failure after V1 would be accompanied by an automatic uprating of the live engine to full power. Alternate mode was selected for the take-off from Sao Jose; the flaps were set for take-off at 9° and the relevant speeds were: V1, 121kt (225km/h); VR, 121kt; V2, 129kt. The throttles were set against the brakes, to a detent just short of maximum forward travel, triggering the FADEC to accelerate the engines to 92% full-power. On brake release, the -145 accelerated briskly and was easy to keep straight in the still air conditions using slight applications of rudder, airspeed building rapidly on the PFD speed tape. Any malfunction on take-off below 80kt would have been countered by an abort, while a "no-go" failure between 80kt and V1 would be dealt with similarly. On this occasion, all went impeccably, the aircraft being rotated at 121kt and, once airborne, to 8° nose-up, requiring more control force than I had expected. Time from brakes-off to rotate was 28s. Acceleration through gear and flap retraction to the climb speed of 220kt was smooth: once at climb speed the rate of climb settled at just under 3,000ft/min (15.24m/s) with both engine N1s at 86%.
The cockpit was impressively quiet with little aerodynamic noise and none discernible from systems. Throughout, the conditioning system kept the cockpit at a pleasant working temperature. The -145 was climbed directly to 30,000ft which took 14min and used 440kg of fuel. During the climb, turns in both directions at 30¡ and 40¡ of bank were carried out.
Stable in all axes
At the totally arbitrary condition of just over 15,000kg, forward centre-of-gravity, clean, 200kt, the -145 appears to be statically stable longitudinally, directionally, and laterally, as expected. At 30,000ft, two turns, left and right, were flown at 40° bank and sustained 1.5G. By now, it was clear that the EMB-145's hydraulically operated ailerons make the aircraft a delight in roll, but the mechanically operated elevators are less endearing, requiring stick forces (both at rotate speeds, and at higher indicated airspeed) a little too high for ideal harmonisation with the ailerons.
The pitch control (via the customary twin switches on the outboard grips of the ram's horns, and electronically driven screw jacks to the adjustable tail plane) was easy to use and I liked the gearing. Very little use of the rudder is needed in normal manoeuvring; it is hydraulically operated and requires light foot forces, harmonising it nicely with the aileron control forces. The -145 descends well at 250kt, power off (an airspeed limit of 250kt below 8,000ft is now imposed because the bird impact tests to the windscreens and leading edges have not yet been done). The speed brake, selected by a lift-up-move-rearwards T-handle on the captain's side of the centre console provokes barely discernible pitch change and no buffeting, but slows the aerodynamically clean -145 effectively, and is equally benign when selected in. At 15,000ft, three stalls were carried out to see the operation of the stick-shaker and stick-pusher (see table). The handling of the aeroplane was as it should have been throughout, with no trace of any tendency for a wing to drop.
A further descent to 5,000ft was made, and the -145 set up for a V2 climb with 9° flap. The weight was now 14,700kg, the V2 120kt and the alternate take-off N1 89% on both engines. Once I had the aircraft on-condition for the test, Rodrigues shut down the left-hand engine using the appropriate red T-handle in the overhead panel. A small sharp yaw resulted, which was readily corrected with a little opposite rudder, easily held by modest foot force, untrimmed, for the ensuing climb. Lowering the nose by about 5° enabled 120kt to be maintained and the -145 continued on its way almost as if nothing had occurred. Engine relighting at 5,000ft and 130kt was easily accomplished. We then made our way back to Sao Jose to intercept the ILS localiser.
Embraer has designed the -145 to give the best possible flexibility when marshalling for the approach and during the approach to the outer marker. The maximum speed for the undercarriage (operating or extended) is a very useful 250kt, the same figure being the limit for approach flap (9°) and 200kt for approach flap (22°). Maximum lift (CL Max) is with 22° landing flap (45° - limiting speed 145kt) maintains that lift, but also brings considerable drag. Final recommended use of flaps for landing has yet to be defined; to date no cross-limit landing trials have been done. For this flight, the briefed arrangement was to use 45°. The aircraft is pleasant to manoeuvre when positioning for an approach or within the visual circuit. Extension and retraction of undercarriage and flap results in little pitch change and response to power changes is good; it is stable on an instrument approach. Flap was set to 45° at about 400ft above ground level on each of the three approaches. Rodrigues' advice was willingly accepted for handling the -145 between setting full flap and the flare. He recommended establishing a nose-up attitude of 5° and using power against the flap drag to control rate of descent. About 62% of normal power was needed to maintain 140kt before allowing the speed to bleed off towards the reference speed (Vat) of 122kt. The attitude remains high into the flare where further rotation of the aircraft leads to a smooth touch down by the main wheels, the nose-wheel then being lowered on to the runway before the elevators lost their authority as speed decreased. As soon as the nosehweels touched, full wheel braking was applied and the aircraft brought to rest in an impressively short distance, the operation of the Maxaret anti-skid units being discernible, but not in the least dramatic. (Reverse thrust for the -145 is a customer option and, if fitted, consists of a clam-shell door on the underside of each engine tail cone: selection is through small subsidiary levers on the throttle lever stems.) None of the state-of-the-art technology blended together by Embraer and Honeywell for the benefit of -145 pilots is seen as running counter to the published philosophy of "back to basics". The Primus 1000 is less sophisticated than Honeywell's Primus 2000, but nevertheless brings the level of integration to cockpit management which Embraer sees as essential for a regional jet operating well into the twenty-first century. In addition to the more obvious systems directly affecting the safe and efficient operation of the -145 such as EICAS and TCAS, the Primus 660 colour weather-radar system and the integrated radio system, the Primus 1000 already has full integration to use global-positioning system information and Honeywell's worldwide navigation database.
The result is an impressively competent package of airframe, engine and flight-management systems, convincingly combined to make the -145 economical to build, economical to operate, safe to fly and attractive to passengers. Embraer has had the acumen to design and build the -145, and the nerve to introduce it to a market already well served. I would say that Embraer's strengths in design, engineering and marketing flair stand an excellent chance of success.
Source: Flight International
