Katharina Franz

An Integrated Environment for Preliminary Aircraft Design and Optimization

This paper presents the Multidisciplinary Integrated Conceptual Aircraft Design and Optimization (MICADO) environment that has been developed during the last years at the Institute of Aeronautics and Astronautics (ILR) of RWTH Aachen University. The MICADO environment allows for automated aircraft design and assessment with a minimum of user input, i.e. a set of top-level requirements and specications. The homogeneous software environment allows for fast parameter studies and optimizations in a wide parameter space and with low computational eort. Due to the integrated design and assessment approach, variations of top-level requirements, local parameter changes as well as integration of new technologies or systems are captured into overall aircraft evaluation parameters such as block fuel or costs. The MICADO software architecture in terms of control and data ow, program structure and parameterization principles is presented. Further, the aircraft design and assessment methodology including the underlying models are discussed, as well as applications of MICADO for aircraft design studies and operational studies. Finally, functionalities and strengths of the proposed methodology are demonstrated by a case study, in which MICADO is used for the design and optimization of a conventional short-range aircraft. For the designed aircraft, variations of initial sizing parameters as well of Mach number and wing sweep angle are performed and overall aircraft design results are discussed.

Influence of Off-Design Performance on the Design of Aircraft with Laminar Flow Technology

Laminar ow is among the most discussed technologies towards satisfying the ambitious goals for more fuel e cient aviation. Both passive as well as active laminar ow control systems are sensitive to external in uences and system failures. A sudden degradation of laminar ow immediately results in loss of ight performance. Such o -design cases have to be considered already in preliminary design synthesis for correct sizing of the aircraft. In the scope of this paper, an approach is presented that incorporates o -design cases of laminar aircraft into preliminary design synthesis. The authors chose to use the extended-range twin-engine performance standards (ETOPS) as framework for deriving operational standards for aircraft with laminar technology. Di erent requirements for minimum o -design performance are derived that directly impact overall aircraft design synthesis. In a case study, the sensitivities of the overall design synthesis towards these o design requirements are discussed. Design parameters such as maximum take-o weight, block fuel, as well as the aircraft economics are used for evaluation of the di erent concepts.

Life Cycle Engineering in Preliminary Aircraft Design

In preliminary aircraft design, the assessment of aircraft life cycle is mainly focused either on life cycle costs, or on economic and environmental analysis of certain life cycle phases. This paper presents an interdisciplinary approach for life cycle engineering during preliminary aircraft design enabling the evaluation of costs and environmental impact of the entire aircraft life cycle. The developed sustainability analysis modules are integrated in a platform together with an aircraft design suite. This allows for feeding back economic, ecological and social impact into the aircraft design synthesis, hence enabling future optimization of aircraft designs for sustainability.

Aircraft Cost Model for Preliminary Design Synthesis

in preliminary aircraft design is presented. The proposed model allows for estimating aircraft list price, unit costs, as well as non-recurring and recurring costs for development and production. Further, the targeted aircraft units during life cycle and for break-even are estimated. Focus is put on civil jet transport aircraft and on applicability of the proposed model in early preliminary design. Although the proposed model is tailored for early design, it shows the required sensitivities to important design parameters, so that design trade-os can be assessed in terms of costs. The dierent cost items are derived from a combined top-down and bottom-up approach. The model is based on list price data of current transport aircraft in combination with semiempirical analyses that are published in literature. The proposed methodology is directly integrated into the ILR Preliminary Aircraft Design Suite for fast assessment of new aircraft concepts and was veried against current aircraft cost data. In the scope of this paper, sensitivity studies are presented to show the inuences of dierent design parameters on costs. In a case study, the proposed model is applied to an existing aircraft program. In another case study, the proposed model is fully integrated into preliminary design synthesis and the resulting inuence of costs on multi-disciplinary design optimization are discussed.

Framework for Sustainability-Driven Aircraft Design

For sustainable development of air transport future aircraft designs play a crucial role. New technologies as well as new design strategies could lead to aircraft designs with higher economic efficiency without impact negatively environment and society. Therefore, sustainability aspects have to be addressed well-balanced already in the design process. Currently the main objectives in aircraft design are economic and environmental aspects with focus on block fuel, operating costs, noise, and emissions. This paper deals with the question, how overall sustainability can be measured and an indicator set for aircraft design purposes is defined. For sustainability assessment of aircraft designs at conceptual design stage quantification models for each indicator are presented. All models are integrated into the Multidisciplinary Integrated Conceptual Aircraft Design and Optimization (MICADO) environment of the Institute of Aerospace Systems (ILR) of RWTH Aachen University. Furthermore, for the use of multiple sustainability criteria two multi criteria decision analysis (MCDA) methods have been selected and integrated. This design and assessment framework enables sustainability-driven aircraft design already at conceptual design stage. Two case studies are presented to show the applicability of the framework. For a designed aircraft a parameter study varying Mach number and flight level is performed and the pareto optimal operating points for the optimization criteria climate change and operating costs are determined. The results show possibilities how to operate existing aircraft designs for lower climate impact without economic disadvantages. To show the impact on overall aircraft level, the same parameter study is performed for the design mission within the design loop. The aircraft designs optimal for single sustainability indicators and, using MCDA methods, for overall sustainability are presented and discussed.

Gains in Fuel Efficiency: Mulit-Stop Missions vs. Laminar Aircraft

Improvements in aircraft operations as well as application of innovative technologies are amongst the most discussed paths towards greener and more fuel ecient aviation. Especially on long-haul routes the payload factor is low due to large fuel weights; this decreases the aircraft eciency signicantly. Intermediate stops for refueling is one possible solution for increasing eciency on long-haul routes. This paper presents a comparison between multi-stop refueling operations with current aircraft technology, and an innovative aircraft concept that features laminar ow technology for decreasing drag. The presented results are based on preliminary aircraft designs and analysis with detailed ight performance simulations of the associated missions. The potential of gains in fuel eciency for the two dierent approaches is compared. Additionally, the impact on transport productivity and direct operating costs for the two concepts is presented in the scope of this paper.

Assessment of Potential Benefit of Formation Flight at Preliminary Aircraft Design Level

In order to close the gap between formation induced drag calculation and the estimation of formation flight benefit at preliminary aircraft design level, a framework for fast assessment of formation aircraft performance has been developed at the Institute of Aerospace Systems (ILR) of RWTH Aachen University. By integrating the aerodynamic methodology into the in-house preliminary aircraft design platform, the framework can estimate the potential induced drag reduction for arbitrary aircraft configurations in formation. For specific flight missions, the block fuel reduction can be determined. As a result, formation flight impact on fuel consumption related emissions and direct operating costs (DOC) can be quantified. The presented results show that a block fuel reduction up to 16% can be expected with two short range commercial aircraft in formation, which corresponds to a cruise flight CO2 reduction around 20% and a DOC savings of more than 6%. For the case of two long range aircraft in formation, the results show slightly more benefit when compared with the short range aircraft. At the very end, this paper briefly investigates the operational considerations of formation flight.

Economic assessment of morphing leading edge systems in conceptual aircraft design

This paper presents an economic assessment of an aircraft design incorporating a morphing leading edge (MLE) device and electrical anti icing (EAI) as necessary technology for its operation. For a representative comparison to other designs direct operating costs (DOC) are chosen as a parameter to capture the multiple impacts of the change from a conventional turbulent design to a natural laminar ow (NLF) and further to the incorporation of the MLE technology. The process of integration of the technologies neccessary to operate a MLE device are described. For a better understanding of the propagation of changes, technical parameters i.e. block fuel (BF) are analyzed as well and compared between the di erent design steps. The designs compared are derived from the mission of a regional aircraft with a maximum capacity of 185 passengers. The software tool applied incorporates empirical and analytical methods that have been validated for the conceptual design phase. The results of the presented process give an indication for decision making towards the potential of innovative technologies.

Assessment of an Innovative Morphing Leading Edge Considering Uncertainties in Conceptual Design

ow technology is its incompatibility with conventional leading edge high-lift systems. Current research that is funded within the EC 7th Framework Program Collaborative project SADE concentrates on the development of an innovative morphing leading edge system. The project recently concluded in conceptual design, feasibility studies as well as in hardware and wind tunnel testing of the technology. For integration and technology assessment on overall aircraft-level, the concept lacks the required maturity in important design parameters such as estimated system mass or high-lift performance. In the scope of this paper, a framework is presented that allows for integrating and assessing innovative technology already in the conceptual design phase on overall aircraft-level by considering the most important design uncertainties with a probabilistic approach. Further, the proposed framework concludes in denition of minimum performance margins for the innovative technology, which are directly fed back into the systems development process as direct performance requirements. In a case study, the proposed framework is applied to technology assessment of an innovative morphing leading edge for a commercial transport aircraft with natural laminar ow technology. The assessment is based on technical parameters such as fuel eciency and specic hourly productivity.