- Email: [email protected]
Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA
CJA 809 17 March 2017 Chinese Journal of Aeronautics, (2017), xxx(xx): xxx–xxx
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Chinese Society of Aeronautics and Astronautics & Beihang University
Chinese Journal of Aeronautics [email protected] www.sciencedirect.com
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Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA Bo-Young Bae a, Sangho Kim a,*, Jae-Woo Lee a, Nhu Van Nguyen b, Bong-Cheul Chung b a b
Department of Aerospace Information Engineering, Konkuk University, Seoul 143-701, Republic of Korea Konkuk Aerospace Design, Airworthiness Research Institute, Konkuk University, Seoul 143-701, Republic of Korea
Received 18 January 2016; revised 1 August 2016; accepted 27 October 2016
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KEYWORDS
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Aircraft configuration; Conceptional design: design requirements; Requirement analysis; Very light aircraft (VLA)
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Abstract In this study, a process for establishing design requirements and selecting alternative configurations for the conceptual phase of aircraft design has been proposed. The proposed process uses system-engineering-based requirement-analysis techniques such as objective tree, analytic hierarchy process, and quality function deployment to establish logical and quantitative standards. Moreover, in order to perform a logical selection of alternative aircraft configurations, it uses advanced decision-making methods such as morphological matrix and technique for order preference by similarity to the ideal solution. In addition, a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight performance of the selected configurations. The present process has been applied for a two-seater very light aircraft (VLA), resulting in a set of tentative design requirements and two families of VLA configurations: a high-wing configuration and a low-wing configuration. The resulting set of design requirements consists of three categories: customer requirements, certification requirements, and performance requirements. The performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer requirements. The flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA. Ó 2017 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
* Corresponding author. E-mail address: [email protected] (S. Kim). Peer review under responsibility of Editorial Committee of CJA.
Production and hosting by Elsevier
1. Introduction
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The life-cycle of an aircraft is divided into the following phases: concept studies on customer requirements, conceptual design, preliminary design, detailed design and development, production, operation and maintenance, decommissioning,
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http://dx.doi.org/10.1016/j.cja.2017.02.018 1000-9361 Ó 2017 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Bae B-Y et al. Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA, Chin J Aeronaut (2017), http://dx.doi.org/10.1016/j.cja.2017.02.018
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and recycling. The conceptual design phase includes several important tasks such as the design requirement analysis, the feasibility study of development, the demand forecasting and market analysis, the conceptual aircraft configuration design and subsystem definition, and the establishment of initial planning for aircraft development. Accordingly the conceptual design phase is most influential in the aircraft life-cycle. Although relatively small investments are necessary during the conceptual design phase, large efforts should be made since 70–90% of a design is defined in this phase. Therefore, development of a logical and efficient conceptual design method will be of great importance. In the conventional conceptual design approaches, the process of selecting the best configuration typically employs a trial and error method based on the experience of a designer. This increases the development time and cost due to the large number of design iterations. Efficient conceptual design requires a series of wellorganized processes that enable designers to make logical and objective decisions on an aircraft design. Many methodologies that can be applied to such processes have been presented in the field of industrial engineering, but there have been very few developments and applications of the methodologies in the conceptual design phase of aerospace engineering. Mavris et al.1,2 successfully established an objective and efficient design process. They excluded a designer’s subjective judgment from their proposed aircraft conceptual design process, which includes concept establishment, selection of alternative configurations, and an assessment process. Park3 improved Mavris’ design process for optimum alternative configurations that reflect user requirements. Yoon4 presented an optimum baseline aircraft configuration selection process using a decision-making model that considers both airworthiness certification regulations and user requirements during the concept design phase. In this study, a systematic design requirement analysis, which is an early stage of the aircraft conceptual design phase, is conducted to produce the design requirements considering user requirements, marketability, and certification regulations. Moreover, a baseline configuration design process is established to suggest objective and reasonable baseline configurations that satisfy the resulting design requirements. For aircraft design purposes, we have strived to make a logical flow in order to select the design requirements and baseline configurations. In addition, the internal data of the process were consistently managed to reflect the design requirements properly. A two-seater very light aircraft (VLA) was selected for the present study because it is anticipated that two-seater VLAs will be in demand as aero leisure sports are becoming popular domestically and globally.
Fig. 1
For the requirement analysis, the voices of users, designers, and clients were collected through a survey of various groups of people including VLA pilots, students and faculty in aerospace engineering, and aviation company engineers. The proposed process of selecting baseline configurations used the quantitative requirements analysis methods (see Fig. 1). It also used initial sizing and a performance analysis respectively to generate the baseline aircraft configurations and to evaluate whether they satisfy the mission and performance requirements.
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2. Building model
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2.1. Brainstorming
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The systematic method proposed in this paper uses a series of decision-making models to address the design requirements and the design alternatives in a more logical, objective, and quantitative manner.5 In this section, the decision-making models used in the present method are briefly described.
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2.2. Affinity diagram
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This method is a long-term human intellectual activity to organize data by grouping the data into groups based on natural relationships. The term ‘‘affinity diagram” was devised by Jiro Kawakita in the 1960s and has been used as a business tool to organize ideas and data.6,7 The method allows a large number of ideas stemming from brainstorming to be sorted into groups for review and analysis.
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2.3. Tree diagram
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The tree diagram8 is a graphical method that lays out a hierarchical structure of objectives and measures systematically to find the most appropriate measures in order to achieve the goals. In general, this method is used for spreading out the subordinate goals of the primary goal or for breaking down a large-scale project into progressively smaller feasible tasks.
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2.4. Analytic hierarchy process
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A psychology and mathematics based method, the analytic hierarchy process (AHP), is a multi-criteria decision-making (MCDM) method for making decisions about complicated problems rationally and efficiently. The AHP was developed by Satty in the 1970s based on the fact that the brain uses a
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Quantitative requirements analysis methods.
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phased or hierarchical analytic process when a human makes a decision.9 During the AHP, the entire decision-making process is divided into several phases and each phase is analyzed to make a final decision. Users firstly decompose their decision problem into a hierarchy of more easily comprehended sub-problems. Once the hierarchy is built, the decision makers systematically rank the order of importance of the elements in the same hierarchical level by performing pairwise comparisons with respect to their impacts on an element above them in the hierarchy. Since the AHP converts these evaluations into numerical values that can be processed until numerical priorities are calculated for each of the decision alternatives, it has been widely used for MCDM problems. Fig. 2
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Quality function deployment (QFD)10 was originally developed as a quality assurance method by Mizuno and Akao in 199411 and has been used in a wide variety of services and consumer products. QFD is described as a method to transform user demands into design quality, to deploy the functions forming quality, to deploy methods for achieving the design quality into subsystems and component parts, and ultimately to specific elements of the manufacturing process. Quality methods prior to QFD focused on reducing internal defects, but QFD focuses on transforming customer needs into engineering characteristics of a service or product. The house of quality (HOQ) tool is used to materialize QFD (see Fig. 2). 2.6. Morphological matrix 12
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2.7. Technique for order preference by similarity to ideal solution
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The technique for order preference by similarity to the ideal solution (TOPSIS)14 was firstly developed and introduced by Hwang and Yoon in 1987. It is based upon the concept that the chosen alternative should have the shortest distance from the positive ideal solution (PIS) and the farthest from the negative ideal solution (NIS). Using this method, the alternatives presented as the solutions to a multi-criteria decision-making problem may be the closest to the PIS; that is, the most beneficial alternative solutions are to be selected. As the design requirements are determined in more detail, brainstorming, the affinity diagram, the tree diagram, the AHP, and QFD are used sequentially based on the characteristics of the decision-making models. Similarly, as the design alternative configurations are defined in more detail, QFD, the morphological matrix, and the TOPSIS are used systematically. A detailed description of how the decision-making models are used in the design requirement analysis and the design
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House of quality (HOQ).10
2.5. Quality function deployment
Morphological analysis is a structured or systematic method developed by Fritz Zwicky (1967, 1969) for exploring all the possible solutions to a multi-dimensional, non-quantified complex problem.13 The method uses a morphological matrix to analyze and list the major components of a system and to generate and identify alternative configurations of the system by exploring possible combinations of the components listed. A designer can determine some possible alternatives, eliminating the illogical solution combinations.
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baseline configuration selection process can be found in Sections 3 and 4.
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3. Systematic process
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In this study, a systematic process of establishing a quantitative standard for the design requirement analysis and the baseline configuration selection in the conceptual aircraft design phase was developed by applying the quality design technique and the decision-making technique. The whole process can be divided into the design requirements analysis process in the initial conceptual design phase and the baseline configuration selection process. The two processes can be schematized into one process using the decision-making model as shown in Fig. 3. For the design requirements analysis process, the requirement categories are divided into user requirements, competition-based requirements, and certification regulation requirements for analysis. The requirement analysis results of the three requirement categories are used to establish temporary design requirements and mission profile of the aircraft. Based on those temporary design requirements and mission profile, design alternatives are selected and then primary design requirements are suggested through the verification process composed of both initial sizing and performance analysis. The process of selecting baseline configurations among the alternatives is also performed using the resulting primary design requirements as the decision standards. During this process, the selected alternative configurations and baseline configurations are used as necessary input parameters for the sizing analysis tool. Finally, the best baseline configuration is selected for the rest of the conceptual design. The key concept of this study, the decision-making process, can be carried out by aggregating information on the alternatives and preferences of the decision makers. There is a need to quantify the standard elements to conduct a quantified evaluation of the design candidates since there is a risk of contradictions among the standard elements in simple comparison. The user requirements analysis process uses an affinity diagram and tree diagram in order to organize the user requirements collected through the survey and brainstorming as shown in Fig. 4. The MCDM methods, AHP and QFD, are used in grasping and laying down the priorities of the organized design elements. The results of the AHP and QFD are then used for set-
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Fig. 3
Quantitative requirement analysis process for baseline configuration selection.
Fig. 4
User requirements analysis process.
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ting the range of the design requirements and evaluating the baseline configuration. The function that determines the scope of design requirements is built through survey and analysis of the competing models. In addition, the certification regulations, which are a social restriction, are investigated and applied to the requirements setting. Through this process, temporary design requirements and mission profiles can be developed and verified using a simple sizing analysis tool. Finally, the primary design requirements are generated as a result of the initial conceptual design and may be revised and supplemented during the rest of the conceptual design phase.15 As shown in Fig. 4, the baseline configuration decision process uses the morphological matrix to generate alternative configurations. The multi-attribute decision-making method, TOPSIS, is used to obtain an optimal alternative. The AHP and QFD results presented above are used as weighting factors for the evaluation of alternatives. Two or more families of baseline configurations can be selected for design. The enhanced in-house sizing methodology and tool were developed and validated for various type of aircraft such as unmanned aerial vehicles (UAVs), unmanned combat aerial vehicles (UCAVs), regional jet aircraft, and electric powered light aircraft from the given set of requirements including users and airworthiness regulations.16 The sizing tool is composed of the integration of a simplified aerodynamics, corrective weight fraction from recent aircraft database and a simplified mission and performance analysis module to perform the inverse performance design by the support of an optimization loop to ensure the satisfaction of users and airworthiness regulation requirements. In addition, the proposed sizing tool reduces the assumptions at the preliminary sizing stage by introducing a rough estimation from a similar aircraft database collection. The in-house sizing tool yields relatively good and quick results at the maximum error of 15.23% compared to the existing MQ-1 Predator wing area data in the sizing stage, while the existing sizing tool provides many assumptions for aerodynamics analysis and an over-predicted empty to gross weight ratio based on meta aircraft regression data. Therefore, the in-house sizing tool is developed and used for selecting the alternative configuration for the conceptual design of VLAs. This sizing tool with the AHP, QFD, and mission analysis results will be used to constitute the optimization problem. The
Fig. 5
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sizing analysis is carried out for each family of baseline configurations. Then a final baseline configuration can be selected through the TOPSIS analysis using the sizing and the user requirements analysis results. This process can be applied to two-seater VLAs as well as to diverse aerospace systems including other fixed-wing aircraft and rotary-wing aircraft.
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4. Implementation and results for a two-seater VLA
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4.1. Introduction to two-seater VLA and purpose of development
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A two-seater VLA is an aircraft classified under the Certification Specifications for Very Light Aircraft (CS-VLA) by the European Aviation Safety Agency (EASA). It has two or fewer seats. Its maximum take-off weight is 750 kg or less and its stall speed is 83 km/h (45 kn) or less. It is a single-engine plane that is only allowed to fly during the day, and the engine must have an ignition plug or be a compressed ignition type engine.6 It is predicted that two-seater VLAs will account for over 50% of global sales in the next ten years, and the demand for VLAs is on the rise. The US government has supported the aviation industry with the law of the American Society for Testing and Materials (ASTM) for light sports aircraft (LSA), newly enacted in 2004, to fulfill the desires of the American people for flying. Currently, more than 230,000 light aircraft are in operation, and light aircraft for leisure will be in great demand globally in the near future. The advantages of the competing aircraft models presented as part of a sales strategy by other companies were examined to establish a development goal of the two-seater VLA in this study. The resulting advantages were flight attributes (speed, flight range, fuel consumption rate, stability, etc.), comfort on long flights (interior, pilot seat size, passenger seats, etc.), visibility (front, sides, openable windows during flight, etc.), aircraft with stylish exterior, safety (fuel tank location, material, safety devices, etc.), smooth landing (landing gear, seats, etc.), doors for comfortable entrance and easy loading, and electrical equipment for easy and stable piloting (Garmin products, various cockpit forms, electrical piloting, etc.). Based on this information, the development goal was established as shown in Fig. 5.
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Development goal.
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4.2. Analysis of competing models
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The CS-VLA is the certification regulation applied to the twoseater VLA. This class of aircraft has a maximum take-off weight (MTOW) of 750 kg but the target MTOW was set as a maximum of 650 kg in order for the VLA to have stronger competitiveness so that it can also enter the LSA market, with simple modification if necessary. An LSA is defined as an aircraft that is a heavier-than-aircraft or a lighter-than-aircraft, other than a helicopter, with a maximum gross take-off weight of no more than 560 kg for a lighter-than-aircraft, or 600 kg for a heavier-than-aircraft not intended for operation on water or 650 kg for an aircraft intended for operation on water. For these reasons, both VLA class and LSA class aircraft need to be considered as competitors. The authors have conducted research on the exterior features, performance, materials, and engines of the selected VLA models that were available for sale and the best-selling LSA models based on the market share data provided by the Federal Aviation Administration (FAA) as of December 2010 (Fig. 6).
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4.3. Analysis of user requirements
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In order to analyze the user requirements for the two-seater aircraft in a quantitative and systematic way, we have conducted an analysis of the user requirements by applying the decision-making model.17 User requirements have been determined through a survey and brainstorming in which undergraduates, aircraft developers, and VLA pilots participated. Then, an affinity diagram and a tree diagram were completed based on the user requirements investigated. Using the affinity
Fig. 6
diagram (see Fig. 7), the top-level user requirements were classified into marketability, environmental friendly, safety, and performance as shown in the figure. Fig. 8 below shows the results of the analysis using the tree diagram. Here, the Level 1 user requirements are the voice of customer (VOC), namely, what customers need with regard to aircraft quality. The Level 3 user requirements are the voice of engineer (VOE), namely, what engineers consider in aircraft design to satisfy the customer needs with regard to aircraft quality. The AHP18 and QFD were conducted through a survey based on the resulting tree. A total of 31 personnel including VLA developers, VLA pilots, and foreign advisors participated in the survey. Every pair of the top-level user requirements, namely marketability, performance, environmental friendly and safety, were compared using the AHP technique in order to estimate the relative importance of the top-level user requirements. Only data with a consistency index of less than 20% were used to ensure a reliable estimation. The results are shown in Fig. 9. The AHP and the primary QFD are linked, and the primary QFD and the secondary QFD are linked. The primary and secondary QFD results for Levels 1, 2, and 3 of the tree diagram are shown in Figs. 10 and 11. The values of the importance are normalized so that the sum of the importance becomes 1. The Level 2 categories of the tree diagram and the results of the primary QFD are used as the evaluation categories and weights when the baseline configuration is selected. The categories from the results of the secondary QFD that are directly related to the design requirements affect the design requirement settings so they are used for the competing model-based requirement analysis and the mission analysis
Analysis of competing models.
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Fig. 9
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Affinity diagram.
Fig. 10
Fig. 11 Fig. 8
4.4. Analysis of competing model based requirements
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Data gained by examining the competing models were used to analyze the trends in weight and performance. The importance figures related to performance among the user requirement analysis results are presented in Table 1. Performance functions for the maximum take-off weight were extracted from the performance trends investigated. Trends of stall speed (for landing configuration), speed limit, service ceiling, maximum cruising speed, take-off distance (including ground roll), landing distance (including ground roll), flight range, and
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Primary QFD results.
Secondary QFD results.
Tree diagram.
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AHP results.
endurance were formulated as functions. As the development goals previously presented, a 10% improvement in the design requirement values for performance compared to those of the competing models was suggested using the performance functions. These suggested design requirements for performance were tentative and will be refined after a feasibility study using the initial sizing and the performance analysis.
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4.5. Analysis of certification regulation requirements
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Two-seater light aircraft need to satisfy the CS-VLA as the VLA class certification regulations to acquire the VLA type certification. In addition, the ASTM standard was analyzed,
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Analysis of certification regulations requirement.19
Design specification
KAS-VLA
ASTM for LSA
Regulation
Content
Basic characteristics
Number of seat
KAS-VLA 1
1 or 2
Power plant
Type of engine
KAS-VLA 1
Single engine, ignition plug of compressed ignition type engine
KAS-VLA 1
Less than 750 kg
Weight
Power Maximum take-off weight Useful load
Structure
Target of g limit
Performance
Maximum cruise speed Stall speed (VS0)
(1) pilot, 1 passenger (each 86 kg), full oil, minimum 1 h fuel for full throttle (2) pilot (86 kg), full oil, full fuel
Regulation
Content
4.2.1 Minimum useful load requirement FAA
1 or 2
FAA
Less than 600 kg (ground), less than 650 kg (water) Wu = 1690_3P, (N) P = rated engine power, (kWSO), Wu = 195 kg 2n4
KAS-VLA 65 Climb
1.5 n 3.8
The maximum structural cruising speed VNO must be 0.89VNE established, not less than the minimum value of VC and not more than the lesser of VC May not exceed 83 km/h (45 kn)
Minimum 2 m/s
5.2.5 Limit maneuvering load factors
Flight condition
Single engine, ignition plug of compressed ignition type engine
(FAA) Maximum speed
220 km/h (120 kn)
(1) Level flight
(1) Power condition set forth in Subparagraph (c) (2) Propeller in the take-off position (3) Landing gear extended (4) Wing flaps in the landing position (5) Cowl flaps closed (6) CG in the most unfavourable position within the allowable range (7) Maximum weight
4.2.1 Stalling speeds
Not exceed 83 km/ h (45 kn)
(a) Not more than take-off power (b) Landing gear retracted (c) Wing flaps in take-off position (d) Cowl flaps in the position used in the cooling tests
4.3.3 Climb
Over 95 m/min (321 ft/m, 1.6 m/s)
(1) MTOW (2) Landing configuration (3) Throttle closed (4) Most unfavorable CG (5) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS air speed (1) MTOW (2) Climb flap angle (3) Full throttle (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS air speed
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(1) Cruise speed: EAS * Vemin: Function of positive load factor and W/S
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Maximum rate of climb
Flight condition
4.2.1 Minimum useful load requirement KAS-VLA 337 Limit maneuvering load factors KAS-VLA 1505 Airspeed limitation KAS VLA 49 Stall speed
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Table 1
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4.4.2 Takeoff
Notes: VC Design cruising speed; Wu Minimum useful load; kWso kW (unit revised); n Load factor; VNE Never exceed speed; VNC Maximum structural cruising speed; CG Centre of gravity; ICAO International Civil Aviation Organization; S.L. Sea level; IAS Indicated air speed; CAS Calibrated air speed; VS1 Stalling speed; MTOW Maximum take-off weight.
(1) MTOW (2) Full throttle (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS air speed (4) At least 1.3VS1, 15 m obstacle
Regulation Flight condition
(a) The distance required to take-off from a dry, level hard surface and climb over a 15 m obstacle must be determined and must not exceed 500 m (b) This must be determined, in a rational and conservative manner
Content
Less than 500 m (15 m obstacle) KAS-VLA 51 Takeoff
Regulation
KAS-VLA Design specification
Table 1 (continued)
Take-off distance
ASTM for LSA
Content
Flight condition
Process of establishing design requirements and selecting alternative configurations
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as shown in Table 1, to secure the competitiveness against LSA class aircraft.
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4.6. Analysis of temporary design requirements
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The design requirements in the initial conceptual design phase for aircraft were classified into the user requirements, competing model-based requirements, and certification regulation requirements for analysis. Mission profiles for two-seater VLAs comprising warm up, taxiing, take off, climb, cruise, descent, reserve, landing and taxiing&shutdown were set up, as shown in Fig. 12. The missions for flight range and cruising time for the analysis of user requirements are suggested in Table 2. The results of the temporary design requirement set are shown in Table 3 and a sizing interpretation tool was used to provide feasible values of the flight range and endurance under the given mission conditions.
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4.7. Selection of baseline configurations
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The decision-making model was employed to quantitatively and systematically determine a baseline configuration for
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Fig. 12
Mission profile.
Table 2
Mission conditions.
Mission
Base condition
Flight condition
1
Maximum range 6 h flight range
2 pilots, maximum fuel, best cruise speed 2 pilots, maximum fuel, maximum cruise speed
2
Table 3 phase.
Design requirements in initial conceptual design
Parameter Weight
Structure Performance
Value MTOW (kg) Useful load (kg) Baggage (kg) Target of g limit Maximum cruise speed (km/h) Stall speed VS0 (km/h) Never exceed speed VNE (km/h) Maximum climb speed (m/s) Service ceiling (m) Take-off distance (m) Landing distance (m) Range (nmile) Endurance (h)
<620 >250 >70 2217 >74 272 >5 >4500 <140 <150 >722 >6
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two-seater VLAs as shown in Fig. 13. The vertical location of the main wings, tail wing configuration type, use of fuselage strut, and engine location were used as the baseline configuration elements in the initial conceptual design phase as shown in Table 4. A total of 16 different combinations could be made using the configuration elements, and the realizable configurations were then chosen as alternative configurations, as shown in Table 5. Table 6 shows the result of the TOPSIS20 analysis conducted on each alternative configuration based on the objective categories in Level 2 of the tree diagram used in the analysis of customer requirements. Two families were selected as the resulting baseline configurations of the TOPSIS analysis. A high wing, a conventional tail wing, a fuselage strut, and a tractor-type engine were selected for the first baseline configuration, while a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were selected for the second baseline configuration. The two selected baseline configurations, Family1 and Family 2, were generated and their performances were analyzed in the conceptual design. This selection method for baseline configurations is more systematic, quantitative, and time-effective than the experiencebased baseline configuration selection process, which forms various types of families through an initial conceptual sketch and reduces the number of families throughout the design process. In this phase, the configuration design elements must be well determined. Quantitative measures for decision-making
Fig. 13
Table 4
Baseline configuration elements.
Content
Configuration design elements
Wing location
High wing
Low wing
Tail wing configuration Fuselage strut (yes/not) Engine location
T-tail Yes Tractor
Conventional tail Not Pusher
can be suggested through the TOPSIS analysis using the determined configuration design elements. For example, the TOPSIS analysis results in Table 6 indicate that, in light of the facts that the ‘safety’ category of the user requirements has received the highest score and that airplanes with high wings hold a high rank, the quantitative analysis of the user requirements and the selection of the baseline configurations have promoted awareness of the safety of airplanes with high wings. On the other hand, since the safety of VLAs can be confirmed by obtaining the type certification, the Family 2 configuration could also be a strong alternative for VLAs based on the ‘marketability’ and ‘performance’ categories of the user requirements.
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4.8. Verification and suggestion for design requirements
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The temporary design requirements including the two missions, maximum flight range, and endurance are verified using
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Process of selecting baseline configurations.
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Possible alternative configurations.
Alternative configuration
Main wing
Tail wing
Strut
Engine
Feasibility
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
High wing High wing High wing High wing High wing High wing High wing High wing Low wing Low wing Low wing Low wing Low wing Low wing Low wing Low wing
T T T T C C C C T T T T C C C C
Yes Yes No No Yes Yes No No Yes Yes No No Yes Yes No No
Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher
Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No No Yes Yes
Table 6
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Results of Pugh concept selection and TOPSIS.
Alternative configuration
Main wing
Tail wing
Strut
Engine
Pugh concept selection Result
Rank
Result
Rank
Baseline 1 2 3 4 5 6 7 8 9 10 11
High wing High wing High wing High wing High wing High wing High wing High wing Low wing Low wing Low wing Low wing
C T T T T C C C T T C C
Yes Yes Yes No No Yes No No No No No No
Tractor Tractor Pusher Tractor Pusher Pusher Tractor Pusher Tractor Pusher Tractor Pusher
0
3 6 8 2 7 8 1 7 5 7 4 7
0.7200 0.3782 0.2071 0.4814 0.2340 0.2071 0.5595 0.2340 0.4828 0.2340 0.5338 0.2340
1 6 11 5 7 11 2 7 4 7 3 7
a simple sizing tool and a performance interpretation tool. As a result, the primary design requirements are presented in Table 7. Six-hour endurance and a flight range of 1400 km are also presented as the mission goals. 4.9. Analysis result for conceptual designs in two baseline configurations Through the analysis of the user requirements and the selection of baseline configurations using the TOPSIS, a high wing, a conventional tail wing with a fuselage strut, and a tractortype engine were selected for the first baseline configuration, while a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were selected for the second baseline configuration. The first iteration of the conceptual design was executed with these two baseline configurations, Family 1 and Family 2. As a result, we were able to develop the configurations shown in Fig. 14, and the performance results were obtained as summarized in Table 8. A comparison of the design requirements and performance analysis results shows that the results for take-off distance and endurance do not fulfill the design requirements. Therefore,
0.2487 0.5167 0.001111 0.42 0.5166 0.1280 0.4198 0.07080 0.4198 0.011112 0.04198
TOPSIS
there is a need to alter the sizing to gain improved performance and satisfy the design requirements. Moreover, the current concept analysis tool used is not sensitive to configuration changes in terms of maximum cruising speed, actual climb limit, and endurance. Thus, there is a need to provide more sophisticated analysis tools. These were left as problems to be resolved as the development of VLAs was carried out henceforth. In order to select a suitable configuration that meets the user requirements between Family 1 and Family 2, the conceptual design results corresponding to the evaluation categories in Level 2 in the user requirements analysis were quantitatively compared. In other words, the weight and the performance as well as the stability coefficient values computed through the conceptual designs of Family 1 and Family 2 were used for the TOPSIS analysis to extract the final baseline configuration. The TOPSIS analysis was conducted considering the following: the lighter the empty weight, the less it costs; the larger the internal space, the more it improves the comfort; the lighter the maximum take-off weight, the more it satisfies the weight requirements; the lower the fuel consumption rate, the more it reduces fuel consumption; and the more the stability coeffi-
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B.-Y. Bae et al. Primary design requirements.
Design Specification Basic characteristics
Power plant Weight
Cabin comfort level
Structure
Performance
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Flight Condition Model No Type of aircraft Number of seat Type of engine Power (hp) Maximum take-off weight (kg)
V02 KAS-VLA 2 Four-cylinder, four-stroke 100 <620
Useful load (kg) Cabin maximum height (m) Cabin maximum width (m) Down vision angle (°) Structure type pressurization Target of g limit Maximum cruise speed (km/h)
>275 >1.15 >1.2 >10 Composite semi monocoque None 2 < g < +4 >217
Stall speed VS0 (km/h)
<74
Never exceed speed VNE (km/h)
272
Maximum rate of climb (m/s)
>5
Service ceiling (m)
>4500
Take-off distance (m)
<140
Landing distance (m)
<150
Maximum range (km)
>1400
Endurance (h)
>6
cient values satisfy the design requirements, the more they satisfy the basic characteristics of the aircraft. As a result, Family 2 received a higher score than that of Family 1. For that rea-
Including 1 pilot
(1) pilot, 1 passenger (each 86 kg), full oil, at least 1 h fuel for full throttle (2) 1 pilot (86 kg), full oil, full fuel Useful load=MTOW Empty weight Maximum IML dimension of cross section
(1) Maximum cruise power (2) Level flight (3) 1pilot + 50%fuel (4) FL50 (5) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) Landing configuration (3) Throttle closed (4) Most unfavorable CG (5) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) Full throttle (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) climb flap angle (3) Throttle below climb throttle (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) 1pilot+50%fuel (2) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) Full throttle (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) Closed throttle (2) Extended flaps (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) 1 pilot, 1 passenger (2) Full fuel (3) Best fuel speed, with 30 min VFR fuel reserve (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) 1 pilot, 1 passenger (2) Full fuel (3) Maximum endurance speed, with 30 min VFR fuel reserve (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed
son, a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were selected as an optimal baseline configuration.
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Process of establishing design requirements and selecting alternative configurations
Fig. 14
Table 8
Baseline configurations Family 1 and Family 2.9
Performance results for Family1 and Family 2.
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Parameter
Requirement
Family 1
Family 2
MTOW (kg) Empty weight (kg) Maximum cruise speed (km/ h) Stall speed (VS0) Never exceed speed (VNE) Maximum climb speed (m/s) Service ceiling (ft) Take-off distance (m) Landing distance (M) Range (nmile) Endurance (h) Coefficient of stability (Cma ) Coefficient of stability (Cnb )
620 350 >217
618.4 354.8 241.2
612.5 317.5 241.2
>74 272 >5 >15,000 <140 <150 >722 >6 Negative Positive
72.72 5.18 15,180 160.8 138.1 1464 5.49 0.45 1.0403 0.09699
71.89 5.34 15,180 144 136.8 1487 5.49 0.40 1.0004 0.07870
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5. Conclusions
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This study has devised a method of establishing logical and quantitative standards by applying the decision-making method. This study also proposed a process of evaluating and selecting various alternative configurations based on the devised standards in the initial conceptual design phase for aircraft development. A baseline configuration selection process using a quantitative requirements analysis method was established, and it was applied to a two-seater VLA, resulting in design requirements and baseline configurations at the initial conceptual design phase of the VLA development project. For the requirement analysis, the voices of users, designers, and clients were collected through a survey from various VLA experts and the survey data were efficiently reflected in the decision-making process. The user requirements, marketability, and certification regulations were taken into consideration for the analysis of the design requirements. In addition, measures to evaluate whether the current design technology
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can satisfy the user requirements in the early development stage were sought. A tree diagram up to Level 3 was made through the user requirements analysis, and the AHP analysis results showed that safety was the most important element. The order of priority and the figures of importance for each category were obtained through the primary and secondary QFD, which were linked to the design requirement settings and baseline configuration settings. Functions for computing the performance with respect to aircraft weights were formulated through the marketability analysis, that is, the analysis of the competing model-based requirements. The computed performance outputs were provided as the performance standard values for the design requirements. The results of the certification requirements analysis given by the CS-VLA and ASTM were set as constraints on the design requirements. As a result, the temporary design requirements including two mission profiles were suggested. By applying the TOPSIS to the alternative configurations developed as combinations of configuration design elements in the conceptual design phase, the baseline configurations were set in two families. A high wing, a conventional tail wing, a fuselage strut, and a tractor-type engine were set for Family 1, while a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were set for Family 2. For the two family configurations, the conceptual design and analysis were used in conducting the TOPSIS based on the quantitatively measured user requirements. In conclusion, Family 2 was selected as the optimal baseline configuration. The proposed requirement analysis and alternative configuration selection process provided improved objectivity and quantitation by systematic composition of the decision-making tools, QFD and TOPSIS. In particular, the present process introduced the initial sizing analysis tool to enforce the quantitative assessment in cooperation with the TOPSIS analysis. The efficiency of the process has been validated by applying it to the VLA development.
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Acknowledgements
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The authors are grateful for the support provided for this research by a grant (No. 1615001723) from the Light Aircraft Development Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government, and also the support from the National Research Foundation of Korea (Grant No. NRF-2014R1A2A2A01003833) funded by the Korean government (MSIP).
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References
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1. Marvis DN, Baker AP, Schrage DP. Development of methodology for the determination of technical feasibility and viability of affordable rotorcraft systemsThe 54th annual forum of the American Helicopter Society; 1998 May 20–22. Washington D.C. Fairfax (VA): American Helicopter Society; 1998. 2. Kirby MR, Marvis DN. Forecasting technology uncertainty in preliminary aircraft designThe 4th world aviation congress and exposition; 1999 October 19–21. San Francisco (CA), Warrendale (PA): SAE International; 1999. 3. Park HU. Study on the robust aerospace system design optimization process [dissertation]. Seoul: Konkuk University; 2007. p. 29–41 [Korean]. 4. Yoon JW, Nguyen N, Choi SM, Lee JW, Kim S, Byun YH. Multidisciplinary general aviation aircraft design optimizations incorporating airworthiness constraints10th AIAA aviation tech-
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B.-Y. Bae et al. nology integration and operation conference; 2010 September 3– 15. Fort Worth (TX), Reston: AIAA. Lee SJ, Chung WJ, Kim KJ. A study on optimal design an piece removing automation system using ARIZ and brainstorming based on DMADOV of 6sigmaKSMTE spring conference. Seoul: KSMTE; 2008. p. 6–7 [Korean]. Baek BS, Won YD. Quality management theory. Seoul: Trade Management Publishing Company; 2001. p. 114–50 [Korean]. Lee SB, Shin DS. Theory of QFD and example. Seoul: I-Tech Publishing Company; 2008. p. 188–200 [Korean]. Park YT. Single PPM quality innovation division of public administration. Seoul: Single PPM Quality Innovation Division; 2000. p. 78–96 [Korean]. Lee JW. Light aircraft system requirement review. Seoul: Light Aircraft Development Center, Konkuk University; 2011. p. 7–13 [Korean]. Lee JW. Research & planning report of light aircraft for sport class. Seoul: Light Aircraft Development Center, Konkuk University; 2011. p. 36–44 [Korean]. Mizuno S, Akao Y. QFD: the customer driven approach to quality planning and deployment. Tokyo: Asian Productivity Organization; 1994. p. 339. Chang DY. Application of the extent analysis method on fuzzy AHP. Eur J Oper Res 1996;95(3):649–55. Tom R. Problem structuring using computer-aided morphological analysis. J Oper Res Soc 2006;57(7):792–801. Shon KY, Yang JW, Kang CS. Assimilation of public opinions in nuclear decision-making using risk perception. Ann Nucl Energy 2001;28(6):553–63.
15. Lee JW. Aircraft conceptual design. Seoul: Kyungmun Publishing Company; 2001. p. 25–36 [Korean]. 16. Nguyen NV, Tyan M, Lee JW. A modified variable complexity modeling for efficient multi-disciplinary aircraft conceptual design. Optimiz Eng 2015;16(2):483–505. 17. Park HU, Park MY, Lee SJ, Lee JW, Byun YH. Development of requirement driven design concept selection process in aerospace system. Computational science and its applications—ICCSA 2006; 2006 May 8–11, vol. 3984. Glasgow, New York: Springer-Verlag; 2006. p. 512–21. 18. Satty TL. The analytic hierarchy process. Boston: Klumer-Nijhoff Publishing; 1982. p. 192–213. 19. Chakldar ND, Charaborty S. A combined TOPSIS-AHP method based approach for non-traditional machining process selection. Proc Inst Mech Eng Part B: J Eng Manuf 2008;222(12):1613–23. 20. Ministry of Land, Infrastructure and Transport. Korean airworthiness standards. Korea [updated 2010 May12; cited 2016 Jan 20]. [Korean]. Sangho Kim received his B.S. degree in Astronautics and Space Science from Kyunghee University in 1992, and his M.S. and Ph.D. degrees in Astronautics and Aeronautics from Stanford University in 1996 and 2001, respectively, where he then became a post-doctoral researcher. He returned to Korea, worked for Agency for Defense Development, and then became a professor in Aeronautical Engineering at Konkuk University. His main research interests are computational fluid dynamics, aerodynamic shape optimization, and multi-disciplinary optimization.
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Chinese Society of Aeronautics and Astronautics & Beihang University
Chinese Journal of Aeronautics [email protected] www.sciencedirect.com
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Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA Bo-Young Bae a, Sangho Kim a,*, Jae-Woo Lee a, Nhu Van Nguyen b, Bong-Cheul Chung b a b
Department of Aerospace Information Engineering, Konkuk University, Seoul 143-701, Republic of Korea Konkuk Aerospace Design, Airworthiness Research Institute, Konkuk University, Seoul 143-701, Republic of Korea
Received 18 January 2016; revised 1 August 2016; accepted 27 October 2016
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KEYWORDS
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Aircraft configuration; Conceptional design: design requirements; Requirement analysis; Very light aircraft (VLA)
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Abstract In this study, a process for establishing design requirements and selecting alternative configurations for the conceptual phase of aircraft design has been proposed. The proposed process uses system-engineering-based requirement-analysis techniques such as objective tree, analytic hierarchy process, and quality function deployment to establish logical and quantitative standards. Moreover, in order to perform a logical selection of alternative aircraft configurations, it uses advanced decision-making methods such as morphological matrix and technique for order preference by similarity to the ideal solution. In addition, a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight performance of the selected configurations. The present process has been applied for a two-seater very light aircraft (VLA), resulting in a set of tentative design requirements and two families of VLA configurations: a high-wing configuration and a low-wing configuration. The resulting set of design requirements consists of three categories: customer requirements, certification requirements, and performance requirements. The performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer requirements. The flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA. Ó 2017 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
* Corresponding author. E-mail address: [email protected] (S. Kim). Peer review under responsibility of Editorial Committee of CJA.
Production and hosting by Elsevier
1. Introduction
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The life-cycle of an aircraft is divided into the following phases: concept studies on customer requirements, conceptual design, preliminary design, detailed design and development, production, operation and maintenance, decommissioning,
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http://dx.doi.org/10.1016/j.cja.2017.02.018 1000-9361 Ó 2017 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Bae B-Y et al. Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA, Chin J Aeronaut (2017), http://dx.doi.org/10.1016/j.cja.2017.02.018
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and recycling. The conceptual design phase includes several important tasks such as the design requirement analysis, the feasibility study of development, the demand forecasting and market analysis, the conceptual aircraft configuration design and subsystem definition, and the establishment of initial planning for aircraft development. Accordingly the conceptual design phase is most influential in the aircraft life-cycle. Although relatively small investments are necessary during the conceptual design phase, large efforts should be made since 70–90% of a design is defined in this phase. Therefore, development of a logical and efficient conceptual design method will be of great importance. In the conventional conceptual design approaches, the process of selecting the best configuration typically employs a trial and error method based on the experience of a designer. This increases the development time and cost due to the large number of design iterations. Efficient conceptual design requires a series of wellorganized processes that enable designers to make logical and objective decisions on an aircraft design. Many methodologies that can be applied to such processes have been presented in the field of industrial engineering, but there have been very few developments and applications of the methodologies in the conceptual design phase of aerospace engineering. Mavris et al.1,2 successfully established an objective and efficient design process. They excluded a designer’s subjective judgment from their proposed aircraft conceptual design process, which includes concept establishment, selection of alternative configurations, and an assessment process. Park3 improved Mavris’ design process for optimum alternative configurations that reflect user requirements. Yoon4 presented an optimum baseline aircraft configuration selection process using a decision-making model that considers both airworthiness certification regulations and user requirements during the concept design phase. In this study, a systematic design requirement analysis, which is an early stage of the aircraft conceptual design phase, is conducted to produce the design requirements considering user requirements, marketability, and certification regulations. Moreover, a baseline configuration design process is established to suggest objective and reasonable baseline configurations that satisfy the resulting design requirements. For aircraft design purposes, we have strived to make a logical flow in order to select the design requirements and baseline configurations. In addition, the internal data of the process were consistently managed to reflect the design requirements properly. A two-seater very light aircraft (VLA) was selected for the present study because it is anticipated that two-seater VLAs will be in demand as aero leisure sports are becoming popular domestically and globally.
Fig. 1
For the requirement analysis, the voices of users, designers, and clients were collected through a survey of various groups of people including VLA pilots, students and faculty in aerospace engineering, and aviation company engineers. The proposed process of selecting baseline configurations used the quantitative requirements analysis methods (see Fig. 1). It also used initial sizing and a performance analysis respectively to generate the baseline aircraft configurations and to evaluate whether they satisfy the mission and performance requirements.
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2. Building model
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2.1. Brainstorming
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The systematic method proposed in this paper uses a series of decision-making models to address the design requirements and the design alternatives in a more logical, objective, and quantitative manner.5 In this section, the decision-making models used in the present method are briefly described.
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2.2. Affinity diagram
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This method is a long-term human intellectual activity to organize data by grouping the data into groups based on natural relationships. The term ‘‘affinity diagram” was devised by Jiro Kawakita in the 1960s and has been used as a business tool to organize ideas and data.6,7 The method allows a large number of ideas stemming from brainstorming to be sorted into groups for review and analysis.
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2.3. Tree diagram
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The tree diagram8 is a graphical method that lays out a hierarchical structure of objectives and measures systematically to find the most appropriate measures in order to achieve the goals. In general, this method is used for spreading out the subordinate goals of the primary goal or for breaking down a large-scale project into progressively smaller feasible tasks.
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2.4. Analytic hierarchy process
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A psychology and mathematics based method, the analytic hierarchy process (AHP), is a multi-criteria decision-making (MCDM) method for making decisions about complicated problems rationally and efficiently. The AHP was developed by Satty in the 1970s based on the fact that the brain uses a
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Quantitative requirements analysis methods.
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phased or hierarchical analytic process when a human makes a decision.9 During the AHP, the entire decision-making process is divided into several phases and each phase is analyzed to make a final decision. Users firstly decompose their decision problem into a hierarchy of more easily comprehended sub-problems. Once the hierarchy is built, the decision makers systematically rank the order of importance of the elements in the same hierarchical level by performing pairwise comparisons with respect to their impacts on an element above them in the hierarchy. Since the AHP converts these evaluations into numerical values that can be processed until numerical priorities are calculated for each of the decision alternatives, it has been widely used for MCDM problems. Fig. 2
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Quality function deployment (QFD)10 was originally developed as a quality assurance method by Mizuno and Akao in 199411 and has been used in a wide variety of services and consumer products. QFD is described as a method to transform user demands into design quality, to deploy the functions forming quality, to deploy methods for achieving the design quality into subsystems and component parts, and ultimately to specific elements of the manufacturing process. Quality methods prior to QFD focused on reducing internal defects, but QFD focuses on transforming customer needs into engineering characteristics of a service or product. The house of quality (HOQ) tool is used to materialize QFD (see Fig. 2). 2.6. Morphological matrix 12
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2.7. Technique for order preference by similarity to ideal solution
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The technique for order preference by similarity to the ideal solution (TOPSIS)14 was firstly developed and introduced by Hwang and Yoon in 1987. It is based upon the concept that the chosen alternative should have the shortest distance from the positive ideal solution (PIS) and the farthest from the negative ideal solution (NIS). Using this method, the alternatives presented as the solutions to a multi-criteria decision-making problem may be the closest to the PIS; that is, the most beneficial alternative solutions are to be selected. As the design requirements are determined in more detail, brainstorming, the affinity diagram, the tree diagram, the AHP, and QFD are used sequentially based on the characteristics of the decision-making models. Similarly, as the design alternative configurations are defined in more detail, QFD, the morphological matrix, and the TOPSIS are used systematically. A detailed description of how the decision-making models are used in the design requirement analysis and the design
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House of quality (HOQ).10
2.5. Quality function deployment
Morphological analysis is a structured or systematic method developed by Fritz Zwicky (1967, 1969) for exploring all the possible solutions to a multi-dimensional, non-quantified complex problem.13 The method uses a morphological matrix to analyze and list the major components of a system and to generate and identify alternative configurations of the system by exploring possible combinations of the components listed. A designer can determine some possible alternatives, eliminating the illogical solution combinations.
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baseline configuration selection process can be found in Sections 3 and 4.
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3. Systematic process
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In this study, a systematic process of establishing a quantitative standard for the design requirement analysis and the baseline configuration selection in the conceptual aircraft design phase was developed by applying the quality design technique and the decision-making technique. The whole process can be divided into the design requirements analysis process in the initial conceptual design phase and the baseline configuration selection process. The two processes can be schematized into one process using the decision-making model as shown in Fig. 3. For the design requirements analysis process, the requirement categories are divided into user requirements, competition-based requirements, and certification regulation requirements for analysis. The requirement analysis results of the three requirement categories are used to establish temporary design requirements and mission profile of the aircraft. Based on those temporary design requirements and mission profile, design alternatives are selected and then primary design requirements are suggested through the verification process composed of both initial sizing and performance analysis. The process of selecting baseline configurations among the alternatives is also performed using the resulting primary design requirements as the decision standards. During this process, the selected alternative configurations and baseline configurations are used as necessary input parameters for the sizing analysis tool. Finally, the best baseline configuration is selected for the rest of the conceptual design. The key concept of this study, the decision-making process, can be carried out by aggregating information on the alternatives and preferences of the decision makers. There is a need to quantify the standard elements to conduct a quantified evaluation of the design candidates since there is a risk of contradictions among the standard elements in simple comparison. The user requirements analysis process uses an affinity diagram and tree diagram in order to organize the user requirements collected through the survey and brainstorming as shown in Fig. 4. The MCDM methods, AHP and QFD, are used in grasping and laying down the priorities of the organized design elements. The results of the AHP and QFD are then used for set-
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Fig. 3
Quantitative requirement analysis process for baseline configuration selection.
Fig. 4
User requirements analysis process.
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ting the range of the design requirements and evaluating the baseline configuration. The function that determines the scope of design requirements is built through survey and analysis of the competing models. In addition, the certification regulations, which are a social restriction, are investigated and applied to the requirements setting. Through this process, temporary design requirements and mission profiles can be developed and verified using a simple sizing analysis tool. Finally, the primary design requirements are generated as a result of the initial conceptual design and may be revised and supplemented during the rest of the conceptual design phase.15 As shown in Fig. 4, the baseline configuration decision process uses the morphological matrix to generate alternative configurations. The multi-attribute decision-making method, TOPSIS, is used to obtain an optimal alternative. The AHP and QFD results presented above are used as weighting factors for the evaluation of alternatives. Two or more families of baseline configurations can be selected for design. The enhanced in-house sizing methodology and tool were developed and validated for various type of aircraft such as unmanned aerial vehicles (UAVs), unmanned combat aerial vehicles (UCAVs), regional jet aircraft, and electric powered light aircraft from the given set of requirements including users and airworthiness regulations.16 The sizing tool is composed of the integration of a simplified aerodynamics, corrective weight fraction from recent aircraft database and a simplified mission and performance analysis module to perform the inverse performance design by the support of an optimization loop to ensure the satisfaction of users and airworthiness regulation requirements. In addition, the proposed sizing tool reduces the assumptions at the preliminary sizing stage by introducing a rough estimation from a similar aircraft database collection. The in-house sizing tool yields relatively good and quick results at the maximum error of 15.23% compared to the existing MQ-1 Predator wing area data in the sizing stage, while the existing sizing tool provides many assumptions for aerodynamics analysis and an over-predicted empty to gross weight ratio based on meta aircraft regression data. Therefore, the in-house sizing tool is developed and used for selecting the alternative configuration for the conceptual design of VLAs. This sizing tool with the AHP, QFD, and mission analysis results will be used to constitute the optimization problem. The
Fig. 5
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sizing analysis is carried out for each family of baseline configurations. Then a final baseline configuration can be selected through the TOPSIS analysis using the sizing and the user requirements analysis results. This process can be applied to two-seater VLAs as well as to diverse aerospace systems including other fixed-wing aircraft and rotary-wing aircraft.
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4. Implementation and results for a two-seater VLA
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4.1. Introduction to two-seater VLA and purpose of development
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A two-seater VLA is an aircraft classified under the Certification Specifications for Very Light Aircraft (CS-VLA) by the European Aviation Safety Agency (EASA). It has two or fewer seats. Its maximum take-off weight is 750 kg or less and its stall speed is 83 km/h (45 kn) or less. It is a single-engine plane that is only allowed to fly during the day, and the engine must have an ignition plug or be a compressed ignition type engine.6 It is predicted that two-seater VLAs will account for over 50% of global sales in the next ten years, and the demand for VLAs is on the rise. The US government has supported the aviation industry with the law of the American Society for Testing and Materials (ASTM) for light sports aircraft (LSA), newly enacted in 2004, to fulfill the desires of the American people for flying. Currently, more than 230,000 light aircraft are in operation, and light aircraft for leisure will be in great demand globally in the near future. The advantages of the competing aircraft models presented as part of a sales strategy by other companies were examined to establish a development goal of the two-seater VLA in this study. The resulting advantages were flight attributes (speed, flight range, fuel consumption rate, stability, etc.), comfort on long flights (interior, pilot seat size, passenger seats, etc.), visibility (front, sides, openable windows during flight, etc.), aircraft with stylish exterior, safety (fuel tank location, material, safety devices, etc.), smooth landing (landing gear, seats, etc.), doors for comfortable entrance and easy loading, and electrical equipment for easy and stable piloting (Garmin products, various cockpit forms, electrical piloting, etc.). Based on this information, the development goal was established as shown in Fig. 5.
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Development goal.
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4.2. Analysis of competing models
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The CS-VLA is the certification regulation applied to the twoseater VLA. This class of aircraft has a maximum take-off weight (MTOW) of 750 kg but the target MTOW was set as a maximum of 650 kg in order for the VLA to have stronger competitiveness so that it can also enter the LSA market, with simple modification if necessary. An LSA is defined as an aircraft that is a heavier-than-aircraft or a lighter-than-aircraft, other than a helicopter, with a maximum gross take-off weight of no more than 560 kg for a lighter-than-aircraft, or 600 kg for a heavier-than-aircraft not intended for operation on water or 650 kg for an aircraft intended for operation on water. For these reasons, both VLA class and LSA class aircraft need to be considered as competitors. The authors have conducted research on the exterior features, performance, materials, and engines of the selected VLA models that were available for sale and the best-selling LSA models based on the market share data provided by the Federal Aviation Administration (FAA) as of December 2010 (Fig. 6).
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4.3. Analysis of user requirements
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In order to analyze the user requirements for the two-seater aircraft in a quantitative and systematic way, we have conducted an analysis of the user requirements by applying the decision-making model.17 User requirements have been determined through a survey and brainstorming in which undergraduates, aircraft developers, and VLA pilots participated. Then, an affinity diagram and a tree diagram were completed based on the user requirements investigated. Using the affinity
Fig. 6
diagram (see Fig. 7), the top-level user requirements were classified into marketability, environmental friendly, safety, and performance as shown in the figure. Fig. 8 below shows the results of the analysis using the tree diagram. Here, the Level 1 user requirements are the voice of customer (VOC), namely, what customers need with regard to aircraft quality. The Level 3 user requirements are the voice of engineer (VOE), namely, what engineers consider in aircraft design to satisfy the customer needs with regard to aircraft quality. The AHP18 and QFD were conducted through a survey based on the resulting tree. A total of 31 personnel including VLA developers, VLA pilots, and foreign advisors participated in the survey. Every pair of the top-level user requirements, namely marketability, performance, environmental friendly and safety, were compared using the AHP technique in order to estimate the relative importance of the top-level user requirements. Only data with a consistency index of less than 20% were used to ensure a reliable estimation. The results are shown in Fig. 9. The AHP and the primary QFD are linked, and the primary QFD and the secondary QFD are linked. The primary and secondary QFD results for Levels 1, 2, and 3 of the tree diagram are shown in Figs. 10 and 11. The values of the importance are normalized so that the sum of the importance becomes 1. The Level 2 categories of the tree diagram and the results of the primary QFD are used as the evaluation categories and weights when the baseline configuration is selected. The categories from the results of the secondary QFD that are directly related to the design requirements affect the design requirement settings so they are used for the competing model-based requirement analysis and the mission analysis
Analysis of competing models.
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Fig. 9
Fig. 7
Affinity diagram.
Fig. 10
Fig. 11 Fig. 8
4.4. Analysis of competing model based requirements
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Data gained by examining the competing models were used to analyze the trends in weight and performance. The importance figures related to performance among the user requirement analysis results are presented in Table 1. Performance functions for the maximum take-off weight were extracted from the performance trends investigated. Trends of stall speed (for landing configuration), speed limit, service ceiling, maximum cruising speed, take-off distance (including ground roll), landing distance (including ground roll), flight range, and
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Primary QFD results.
Secondary QFD results.
Tree diagram.
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354
AHP results.
endurance were formulated as functions. As the development goals previously presented, a 10% improvement in the design requirement values for performance compared to those of the competing models was suggested using the performance functions. These suggested design requirements for performance were tentative and will be refined after a feasibility study using the initial sizing and the performance analysis.
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4.5. Analysis of certification regulation requirements
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Two-seater light aircraft need to satisfy the CS-VLA as the VLA class certification regulations to acquire the VLA type certification. In addition, the ASTM standard was analyzed,
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Analysis of certification regulations requirement.19
Design specification
KAS-VLA
ASTM for LSA
Regulation
Content
Basic characteristics
Number of seat
KAS-VLA 1
1 or 2
Power plant
Type of engine
KAS-VLA 1
Single engine, ignition plug of compressed ignition type engine
KAS-VLA 1
Less than 750 kg
Weight
Power Maximum take-off weight Useful load
Structure
Target of g limit
Performance
Maximum cruise speed Stall speed (VS0)
(1) pilot, 1 passenger (each 86 kg), full oil, minimum 1 h fuel for full throttle (2) pilot (86 kg), full oil, full fuel
Regulation
Content
4.2.1 Minimum useful load requirement FAA
1 or 2
FAA
Less than 600 kg (ground), less than 650 kg (water) Wu = 1690_3P, (N) P = rated engine power, (kWSO), Wu = 195 kg 2n4
KAS-VLA 65 Climb
1.5 n 3.8
The maximum structural cruising speed VNO must be 0.89VNE established, not less than the minimum value of VC and not more than the lesser of VC May not exceed 83 km/h (45 kn)
Minimum 2 m/s
5.2.5 Limit maneuvering load factors
Flight condition
Single engine, ignition plug of compressed ignition type engine
(FAA) Maximum speed
220 km/h (120 kn)
(1) Level flight
(1) Power condition set forth in Subparagraph (c) (2) Propeller in the take-off position (3) Landing gear extended (4) Wing flaps in the landing position (5) Cowl flaps closed (6) CG in the most unfavourable position within the allowable range (7) Maximum weight
4.2.1 Stalling speeds
Not exceed 83 km/ h (45 kn)
(a) Not more than take-off power (b) Landing gear retracted (c) Wing flaps in take-off position (d) Cowl flaps in the position used in the cooling tests
4.3.3 Climb
Over 95 m/min (321 ft/m, 1.6 m/s)
(1) MTOW (2) Landing configuration (3) Throttle closed (4) Most unfavorable CG (5) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS air speed (1) MTOW (2) Climb flap angle (3) Full throttle (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS air speed
B.-Y. Bae et al.
(1) Cruise speed: EAS * Vemin: Function of positive load factor and W/S
No. of Pages 14
Maximum rate of climb
Flight condition
4.2.1 Minimum useful load requirement KAS-VLA 337 Limit maneuvering load factors KAS-VLA 1505 Airspeed limitation KAS VLA 49 Stall speed
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Table 1
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4.4.2 Takeoff
Notes: VC Design cruising speed; Wu Minimum useful load; kWso kW (unit revised); n Load factor; VNE Never exceed speed; VNC Maximum structural cruising speed; CG Centre of gravity; ICAO International Civil Aviation Organization; S.L. Sea level; IAS Indicated air speed; CAS Calibrated air speed; VS1 Stalling speed; MTOW Maximum take-off weight.
(1) MTOW (2) Full throttle (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS air speed (4) At least 1.3VS1, 15 m obstacle
Regulation Flight condition
(a) The distance required to take-off from a dry, level hard surface and climb over a 15 m obstacle must be determined and must not exceed 500 m (b) This must be determined, in a rational and conservative manner
Content
Less than 500 m (15 m obstacle) KAS-VLA 51 Takeoff
Regulation
KAS-VLA Design specification
Table 1 (continued)
Take-off distance
ASTM for LSA
Content
Flight condition
Process of establishing design requirements and selecting alternative configurations
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as shown in Table 1, to secure the competitiveness against LSA class aircraft.
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4.6. Analysis of temporary design requirements
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The design requirements in the initial conceptual design phase for aircraft were classified into the user requirements, competing model-based requirements, and certification regulation requirements for analysis. Mission profiles for two-seater VLAs comprising warm up, taxiing, take off, climb, cruise, descent, reserve, landing and taxiing&shutdown were set up, as shown in Fig. 12. The missions for flight range and cruising time for the analysis of user requirements are suggested in Table 2. The results of the temporary design requirement set are shown in Table 3 and a sizing interpretation tool was used to provide feasible values of the flight range and endurance under the given mission conditions.
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4.7. Selection of baseline configurations
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The decision-making model was employed to quantitatively and systematically determine a baseline configuration for
389
Fig. 12
Mission profile.
Table 2
Mission conditions.
Mission
Base condition
Flight condition
1
Maximum range 6 h flight range
2 pilots, maximum fuel, best cruise speed 2 pilots, maximum fuel, maximum cruise speed
2
Table 3 phase.
Design requirements in initial conceptual design
Parameter Weight
Structure Performance
Value MTOW (kg) Useful load (kg) Baggage (kg) Target of g limit Maximum cruise speed (km/h) Stall speed VS0 (km/h) Never exceed speed VNE (km/h) Maximum climb speed (m/s) Service ceiling (m) Take-off distance (m) Landing distance (m) Range (nmile) Endurance (h)
<620 >250 >70 2
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two-seater VLAs as shown in Fig. 13. The vertical location of the main wings, tail wing configuration type, use of fuselage strut, and engine location were used as the baseline configuration elements in the initial conceptual design phase as shown in Table 4. A total of 16 different combinations could be made using the configuration elements, and the realizable configurations were then chosen as alternative configurations, as shown in Table 5. Table 6 shows the result of the TOPSIS20 analysis conducted on each alternative configuration based on the objective categories in Level 2 of the tree diagram used in the analysis of customer requirements. Two families were selected as the resulting baseline configurations of the TOPSIS analysis. A high wing, a conventional tail wing, a fuselage strut, and a tractor-type engine were selected for the first baseline configuration, while a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were selected for the second baseline configuration. The two selected baseline configurations, Family1 and Family 2, were generated and their performances were analyzed in the conceptual design. This selection method for baseline configurations is more systematic, quantitative, and time-effective than the experiencebased baseline configuration selection process, which forms various types of families through an initial conceptual sketch and reduces the number of families throughout the design process. In this phase, the configuration design elements must be well determined. Quantitative measures for decision-making
Fig. 13
Table 4
Baseline configuration elements.
Content
Configuration design elements
Wing location
High wing
Low wing
Tail wing configuration Fuselage strut (yes/not) Engine location
T-tail Yes Tractor
Conventional tail Not Pusher
can be suggested through the TOPSIS analysis using the determined configuration design elements. For example, the TOPSIS analysis results in Table 6 indicate that, in light of the facts that the ‘safety’ category of the user requirements has received the highest score and that airplanes with high wings hold a high rank, the quantitative analysis of the user requirements and the selection of the baseline configurations have promoted awareness of the safety of airplanes with high wings. On the other hand, since the safety of VLAs can be confirmed by obtaining the type certification, the Family 2 configuration could also be a strong alternative for VLAs based on the ‘marketability’ and ‘performance’ categories of the user requirements.
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4.8. Verification and suggestion for design requirements
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The temporary design requirements including the two missions, maximum flight range, and endurance are verified using
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Process of selecting baseline configurations.
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438 439
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Possible alternative configurations.
Alternative configuration
Main wing
Tail wing
Strut
Engine
Feasibility
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
High wing High wing High wing High wing High wing High wing High wing High wing Low wing Low wing Low wing Low wing Low wing Low wing Low wing Low wing
T T T T C C C C T T T T C C C C
Yes Yes No No Yes Yes No No Yes Yes No No Yes Yes No No
Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher Tractor Pusher
Yes Yes Yes Yes Yes Yes Yes Yes No No Yes Yes No No Yes Yes
Table 6
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Results of Pugh concept selection and TOPSIS.
Alternative configuration
Main wing
Tail wing
Strut
Engine
Pugh concept selection Result
Rank
Result
Rank
Baseline 1 2 3 4 5 6 7 8 9 10 11
High wing High wing High wing High wing High wing High wing High wing High wing Low wing Low wing Low wing Low wing
C T T T T C C C T T C C
Yes Yes Yes No No Yes No No No No No No
Tractor Tractor Pusher Tractor Pusher Pusher Tractor Pusher Tractor Pusher Tractor Pusher
0
3 6 8 2 7 8 1 7 5 7 4 7
0.7200 0.3782 0.2071 0.4814 0.2340 0.2071 0.5595 0.2340 0.4828 0.2340 0.5338 0.2340
1 6 11 5 7 11 2 7 4 7 3 7
a simple sizing tool and a performance interpretation tool. As a result, the primary design requirements are presented in Table 7. Six-hour endurance and a flight range of 1400 km are also presented as the mission goals. 4.9. Analysis result for conceptual designs in two baseline configurations Through the analysis of the user requirements and the selection of baseline configurations using the TOPSIS, a high wing, a conventional tail wing with a fuselage strut, and a tractortype engine were selected for the first baseline configuration, while a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were selected for the second baseline configuration. The first iteration of the conceptual design was executed with these two baseline configurations, Family 1 and Family 2. As a result, we were able to develop the configurations shown in Fig. 14, and the performance results were obtained as summarized in Table 8. A comparison of the design requirements and performance analysis results shows that the results for take-off distance and endurance do not fulfill the design requirements. Therefore,
0.2487 0.5167 0.001111 0.42 0.5166 0.1280 0.4198 0.07080 0.4198 0.011112 0.04198
TOPSIS
there is a need to alter the sizing to gain improved performance and satisfy the design requirements. Moreover, the current concept analysis tool used is not sensitive to configuration changes in terms of maximum cruising speed, actual climb limit, and endurance. Thus, there is a need to provide more sophisticated analysis tools. These were left as problems to be resolved as the development of VLAs was carried out henceforth. In order to select a suitable configuration that meets the user requirements between Family 1 and Family 2, the conceptual design results corresponding to the evaluation categories in Level 2 in the user requirements analysis were quantitatively compared. In other words, the weight and the performance as well as the stability coefficient values computed through the conceptual designs of Family 1 and Family 2 were used for the TOPSIS analysis to extract the final baseline configuration. The TOPSIS analysis was conducted considering the following: the lighter the empty weight, the less it costs; the larger the internal space, the more it improves the comfort; the lighter the maximum take-off weight, the more it satisfies the weight requirements; the lower the fuel consumption rate, the more it reduces fuel consumption; and the more the stability coeffi-
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B.-Y. Bae et al. Primary design requirements.
Design Specification Basic characteristics
Power plant Weight
Cabin comfort level
Structure
Performance
476 477 478
Flight Condition Model No Type of aircraft Number of seat Type of engine Power (hp) Maximum take-off weight (kg)
V02 KAS-VLA 2 Four-cylinder, four-stroke 100 <620
Useful load (kg) Cabin maximum height (m) Cabin maximum width (m) Down vision angle (°) Structure type pressurization Target of g limit Maximum cruise speed (km/h)
>275 >1.15 >1.2 >10 Composite semi monocoque None 2 < g < +4 >217
Stall speed VS0 (km/h)
<74
Never exceed speed VNE (km/h)
272
Maximum rate of climb (m/s)
>5
Service ceiling (m)
>4500
Take-off distance (m)
<140
Landing distance (m)
<150
Maximum range (km)
>1400
Endurance (h)
>6
cient values satisfy the design requirements, the more they satisfy the basic characteristics of the aircraft. As a result, Family 2 received a higher score than that of Family 1. For that rea-
Including 1 pilot
(1) pilot, 1 passenger (each 86 kg), full oil, at least 1 h fuel for full throttle (2) 1 pilot (86 kg), full oil, full fuel Useful load=MTOW Empty weight Maximum IML dimension of cross section
(1) Maximum cruise power (2) Level flight (3) 1pilot + 50%fuel (4) FL50 (5) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) Landing configuration (3) Throttle closed (4) Most unfavorable CG (5) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) Full throttle (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) climb flap angle (3) Throttle below climb throttle (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) 1pilot+50%fuel (2) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) MTOW (2) Full throttle (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) Closed throttle (2) Extended flaps (3) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) 1 pilot, 1 passenger (2) Full fuel (3) Best fuel speed, with 30 min VFR fuel reserve (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed (1) 1 pilot, 1 passenger (2) Full fuel (3) Maximum endurance speed, with 30 min VFR fuel reserve (4) Still air condition, standard ICAO atmosphere, S.L., IAS or CAS airspeed
son, a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were selected as an optimal baseline configuration.
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Fig. 14
Table 8
Baseline configurations Family 1 and Family 2.9
Performance results for Family1 and Family 2.
9
Parameter
Requirement
Family 1
Family 2
MTOW (kg) Empty weight (kg) Maximum cruise speed (km/ h) Stall speed (VS0) Never exceed speed (VNE) Maximum climb speed (m/s) Service ceiling (ft) Take-off distance (m) Landing distance (M) Range (nmile) Endurance (h) Coefficient of stability (Cma ) Coefficient of stability (Cnb )
620 350 >217
618.4 354.8 241.2
612.5 317.5 241.2
>74 272 >5 >15,000 <140 <150 >722 >6 Negative Positive
72.72 5.18 15,180 160.8 138.1 1464 5.49 0.45 1.0403 0.09699
71.89 5.34 15,180 144 136.8 1487 5.49 0.40 1.0004 0.07870
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5. Conclusions
483
This study has devised a method of establishing logical and quantitative standards by applying the decision-making method. This study also proposed a process of evaluating and selecting various alternative configurations based on the devised standards in the initial conceptual design phase for aircraft development. A baseline configuration selection process using a quantitative requirements analysis method was established, and it was applied to a two-seater VLA, resulting in design requirements and baseline configurations at the initial conceptual design phase of the VLA development project. For the requirement analysis, the voices of users, designers, and clients were collected through a survey from various VLA experts and the survey data were efficiently reflected in the decision-making process. The user requirements, marketability, and certification regulations were taken into consideration for the analysis of the design requirements. In addition, measures to evaluate whether the current design technology
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13
can satisfy the user requirements in the early development stage were sought. A tree diagram up to Level 3 was made through the user requirements analysis, and the AHP analysis results showed that safety was the most important element. The order of priority and the figures of importance for each category were obtained through the primary and secondary QFD, which were linked to the design requirement settings and baseline configuration settings. Functions for computing the performance with respect to aircraft weights were formulated through the marketability analysis, that is, the analysis of the competing model-based requirements. The computed performance outputs were provided as the performance standard values for the design requirements. The results of the certification requirements analysis given by the CS-VLA and ASTM were set as constraints on the design requirements. As a result, the temporary design requirements including two mission profiles were suggested. By applying the TOPSIS to the alternative configurations developed as combinations of configuration design elements in the conceptual design phase, the baseline configurations were set in two families. A high wing, a conventional tail wing, a fuselage strut, and a tractor-type engine were set for Family 1, while a low wing, a conventional tail wing, no fuselage strut, and a tractor-type engine were set for Family 2. For the two family configurations, the conceptual design and analysis were used in conducting the TOPSIS based on the quantitatively measured user requirements. In conclusion, Family 2 was selected as the optimal baseline configuration. The proposed requirement analysis and alternative configuration selection process provided improved objectivity and quantitation by systematic composition of the decision-making tools, QFD and TOPSIS. In particular, the present process introduced the initial sizing analysis tool to enforce the quantitative assessment in cooperation with the TOPSIS analysis. The efficiency of the process has been validated by applying it to the VLA development.
500
Acknowledgements
535
The authors are grateful for the support provided for this research by a grant (No. 1615001723) from the Light Aircraft Development Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government, and also the support from the National Research Foundation of Korea (Grant No. NRF-2014R1A2A2A01003833) funded by the Korean government (MSIP).
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References
543
1. Marvis DN, Baker AP, Schrage DP. Development of methodology for the determination of technical feasibility and viability of affordable rotorcraft systemsThe 54th annual forum of the American Helicopter Society; 1998 May 20–22. Washington D.C. Fairfax (VA): American Helicopter Society; 1998. 2. Kirby MR, Marvis DN. Forecasting technology uncertainty in preliminary aircraft designThe 4th world aviation congress and exposition; 1999 October 19–21. San Francisco (CA), Warrendale (PA): SAE International; 1999. 3. Park HU. Study on the robust aerospace system design optimization process [dissertation]. Seoul: Konkuk University; 2007. p. 29–41 [Korean]. 4. Yoon JW, Nguyen N, Choi SM, Lee JW, Kim S, Byun YH. Multidisciplinary general aviation aircraft design optimizations incorporating airworthiness constraints10th AIAA aviation tech-
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501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534
537 538 539 540 541 542
544 545 546 547 548 549 550 551 552 553 554 555 556 557 558
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14 559 560 561
5.
562 563 564 565
6.
566 567
7.
568 569
8.
570 571 572
9.
573 574 575
10.
576 577 578
11.
579 580 581
12.
582 583
13.
584 585 586 587
14.
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B.-Y. Bae et al. nology integration and operation conference; 2010 September 3– 15. Fort Worth (TX), Reston: AIAA. Lee SJ, Chung WJ, Kim KJ. A study on optimal design an piece removing automation system using ARIZ and brainstorming based on DMADOV of 6sigmaKSMTE spring conference. Seoul: KSMTE; 2008. p. 6–7 [Korean]. Baek BS, Won YD. Quality management theory. Seoul: Trade Management Publishing Company; 2001. p. 114–50 [Korean]. Lee SB, Shin DS. Theory of QFD and example. Seoul: I-Tech Publishing Company; 2008. p. 188–200 [Korean]. Park YT. Single PPM quality innovation division of public administration. Seoul: Single PPM Quality Innovation Division; 2000. p. 78–96 [Korean]. Lee JW. Light aircraft system requirement review. Seoul: Light Aircraft Development Center, Konkuk University; 2011. p. 7–13 [Korean]. Lee JW. Research & planning report of light aircraft for sport class. Seoul: Light Aircraft Development Center, Konkuk University; 2011. p. 36–44 [Korean]. Mizuno S, Akao Y. QFD: the customer driven approach to quality planning and deployment. Tokyo: Asian Productivity Organization; 1994. p. 339. Chang DY. Application of the extent analysis method on fuzzy AHP. Eur J Oper Res 1996;95(3):649–55. Tom R. Problem structuring using computer-aided morphological analysis. J Oper Res Soc 2006;57(7):792–801. Shon KY, Yang JW, Kang CS. Assimilation of public opinions in nuclear decision-making using risk perception. Ann Nucl Energy 2001;28(6):553–63.
15. Lee JW. Aircraft conceptual design. Seoul: Kyungmun Publishing Company; 2001. p. 25–36 [Korean]. 16. Nguyen NV, Tyan M, Lee JW. A modified variable complexity modeling for efficient multi-disciplinary aircraft conceptual design. Optimiz Eng 2015;16(2):483–505. 17. Park HU, Park MY, Lee SJ, Lee JW, Byun YH. Development of requirement driven design concept selection process in aerospace system. Computational science and its applications—ICCSA 2006; 2006 May 8–11, vol. 3984. Glasgow, New York: Springer-Verlag; 2006. p. 512–21. 18. Satty TL. The analytic hierarchy process. Boston: Klumer-Nijhoff Publishing; 1982. p. 192–213. 19. Chakldar ND, Charaborty S. A combined TOPSIS-AHP method based approach for non-traditional machining process selection. Proc Inst Mech Eng Part B: J Eng Manuf 2008;222(12):1613–23. 20. Ministry of Land, Infrastructure and Transport. Korean airworthiness standards. Korea [updated 2010 May12; cited 2016 Jan 20]. [Korean]. Sangho Kim received his B.S. degree in Astronautics and Space Science from Kyunghee University in 1992, and his M.S. and Ph.D. degrees in Astronautics and Aeronautics from Stanford University in 1996 and 2001, respectively, where he then became a post-doctoral researcher. He returned to Korea, worked for Agency for Defense Development, and then became a professor in Aeronautical Engineering at Konkuk University. His main research interests are computational fluid dynamics, aerodynamic shape optimization, and multi-disciplinary optimization.
Please cite this article in press as: Bae B-Y et al. Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA, Chin J Aeronaut (2017), http://dx.doi.org/10.1016/j.cja.2017.02.018
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