Design, Development and Flight Testing of the New EUROCOPTER EC145 Medium Twin Axel Humpert, Clive Schley EUROCOPTER Deutschland Gmbh Donauwoerth, Germany
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Design, Development and Flight Testing of the new EUROCOPTER EC145 Medium Twin Axel Humpert, Clive Schley EUROCOPTER Deutschland GmbH Donauwoerth, Germany Abstract Introduction The EC145 is EUROCOPTER’s new medium Beginning with the BO105 helicopter in 1971, and weight twin engined helicopter, successor of the followed a decade later with the BK117, MBB well proven BK117 model, and destined to match Helicopter Division - now EUROCOPTER Deutsch- latest market requirements by implementation of land - brought up two innovative products, which state-of-the-art technology into rugged and proven both revolutionized the market by advanced design design. features. Their characteristics included twin engine application, four-bladed hingeless rotor “System This paper focuses on design requirements and Bölkow”, redundant system layout, and rear loading objectives for the EC145, which lead to airframe capability together with a one-level cabin and enlargement and reshaping, introduction of most compartment floor for unobstructed cabin use. The modern technologies such as new main rotor BK117 was co-developed with Kawasaki Heavy airfoils, and fully integrated glass cockpit design as Industries of Japan, who was responsible mainly well as further system upgrades in order to satisfy for design and manufacturing of the center operational and economical customer demands. fuselage, main gear box and electrical system as well as fuel tank design. Market response and reaction promise highest In the 90’s, further improvements such as glass acceptance of the design, which is based on cockpit technology and aerodynamic optimized proven high technology items taken from EC135, fuselage shaping, along with the use of composite reliable design features of the former BK117 material and new production methods - not model, and new development applications, which mentioning other design features (for those see /4/ are all combined in this helicopter. and /5/) - lead to development of the light twin EC135 as successor to the BO105. As a logical Within this paper, also first test results will be step, the EC145 now follows to satisfy market shown, as well as the current development status demands of the new century by taking the best is given. technology available from EC135 and BK117, and providing customers a state-of-the-art-technology Fig. 1: EC145 Evolution EC135 BK117 C-1 Latest technologies Rugged and proven EC145 Modern and reliable 37.1 High performance/ Low DOC hub High TBO Redundant low noise blades “System Bölkow” main gear box hydraulic system Aerodynamically Powerful optimized fuselage reliable engines High visibility cockpit High tailrotor Low workload MMI optimized cockpit Swept endplates Energy absorbing skid Add. landing gear equipment compartment Rear and side Undivided compartment, straight Spacious cabin for 9 Pax, no door & loading capability single level floor design center post for excellent accessibility Fig. 2: EC145 Characteristics Main Helicopter Design Characteristica medium twin helicopter meeting their multi-mission Latest design tools allowed a straight forward, requirements for present and future operations. efficient and fast design process. Use of 3-D These include mainly rescue and EMS missions, CATIA allowed creating a Digital Mockup for first paramilitary/police missions, VIP/passenger trans- fuselage investigation on e.g. tank installation and port, cargo transfer, off-shore oil rig support, areal cabin shaping, and further on for “installation” of photographing and training. Balancing the various optional equipment in a very early design phase. operational requirements called for increase of Design commonality with the EC135 offered the payload, improved range, reduced noise signature, possibility for reduction of specific assembly eased cockpit crew workload, comfortable cabin tooling. Use of improved material allowed low access and size enhancement and flexibility, weight components and manufacturing cost system reliability and safety, as well as competitive reduction. operating costs. Last, and known from the BK117, The primary fuselage structure is mainly of sheet also performance Class 1 requirements were to be metal design, while other major parts such as the met to allow operation under JAR Ops 3 rule. cockpit frame, roof, floor, engine cowlings and doors are made of weight reducing composite Fig. 3: External Dimensions material. Figure 1 simplifies the 13.03 m 3.45 m 0.45 m 10.19 m 1.73 m Ø 11.00 m 3.20 m 37.2 Fig. 4: Cabin Dimensions and Versatility including primary systems are now routed through the windshield middle post, and have been realized evolution of the EC145: the cockpit structure for the first time by the use of flexball technique. design is taken from the EC135, while fuselage The aerodynamic optimized front area of the and empennage design are known from the BK117 cockpit structure contributes to the modern design. C-1. The tail boom and tail rotor were taken from the BK117 C-1, whereas some changes were applied Fuselage by sweeping back the horizontal stabilizer, changing its size and re-shaping the endplates. All The EC145 fuselage was lengthened by 200mm, this for improved helicopter dynamic response and and was widened by 180mm to accomodate two protection against inadvertent contact with the additional passengers in a third pax row. turning tail rotor. Alternatively, e.g. for casualty evacuation, the cabin Crash resistance was one of the mandatory layout offers space for max. two pilots plus two requirements, which have been incorporated in the litters plus three crew seats for doctor and fuselage design incl. fuel tank, landing gear as well attendant. The overall cabin volume increased from as pilot/pax seats. 5m3 to 5.85m3, see also Figure 4. The center post was removed, as well as the door Main Rotor Blade post could be renounced, both features improving access to the cabin and enhancing visibility, thus The main rotor blade design requirements included contributing to safety during certain flight a 150kg thrust increase at comparable power operations such as rescue winching. Flight controls versus BK117 C-1, noise reducing blade shape in 37.3 Nickel strip leading edge for erosion protection Slender blade tip Balance weight Integrated weights (for blade interchangeability) Carbon layer Fiberglas spar Foam filling Fig. 5: Advanced Technology Main Rotor Blade Cockpit particular of the slendered tip section, Nickel In order to allow the pilot concentrating on his leading edge design for erosion protection, mission tasks, the cockpit instrument panel has integration of balancing weights to allow blade been simplified, and has been ergonomically interchangeability, and the use of advanced adapted from the EC135. It offers the basic Central production methods, see Figure 5. Panel Display System (CPDS), as well as the optional MEGHAS Flight Control Display System The new main rotor was developed /1/ and flight (FCDS), both of LCD technology and developed by tested /3/ in the framework of the ATR (Advanced Thales. This glass cockpit is also common to Technology Rotor) research programme. The rotor further EUROCOPTER helicopters such as the layout was achieved as the result of an EC120, EC130 and EC155. evolutionary process. A newly developed series of The central warning unit gives visual as well as advanced blade airfoils with optimised distribution aural signals, which are triggered e.g. by engine over the blade radius was applied. The blade fire detection or out-of-normal-operation rotor RPM. planform with negative taper and the twist Besides of the back-up conventional instruments distribution were based on the experience gained clock, air speed indicator, stand-by-horizon, in former research programmes, see Figure 6. altimeter and triple tachometer, the central instrument panel includes the main switch panel for engine start, VARTOMS (Variable Rotor RPM and Torque Matching System) control panel and DC power control. The Central Panel Display System CPDS is composed of the VEMD (Vehicle and Engine Monitoring Display) and the CAD (Caution and Advisory Display ). The VEMD is a duplex indicator composed of two active matrix liquid crystal displays. The CAD is a simplex indicator of one active matrix liquid crystal display. The CPDS displays all necessary engine and vehicle parameters, such as: • The FLI (First Limit Indication) ∆N1, N1, TOT and TRQ • Fuel Indication • Display of Cautions and Advisories Fig. 6: ATR Blade Geometry and Twist • Vne • Pressure and Temperature of Engine Oil • Bleed Valve status • Pressure and Temperature of Main Gear Box Oil 37.4 • Mast Moment The compact, but clearly arranged and easy • Hydraulic Pressure understandable instruments, along with the large • Ouside Air Temperature OAT glazed cockpit window offer MMI optimized • Fuel Flow and remaining Flight Time operation with reduced workload and provide (optional, if installed) superior visibility to the outside terrain, thus • Electrical System parameters significantly increasing safety in particular at flight • Icing Rate (optional, if installed) near ground and in obstructed area. Maintenance functions included in the display • Hook Load / Rescue Hoist Cable system furthermore reduce operating costs. The Length (optional, if installed ) digital system allows easy transfer of air data • Flight Duration computer and attitude/heading reference signals to the AFCS and to other equipment such as digital maps. Displaying video pictures such as received and performs the following complementary from Weather Radar