(Georgia Institute of Technology, 1999-05)
Mavris, Dimitri N.; Baker, Andrew Paul; Schrage, Daniel P.
The methodology presented in this paper is concerned with the ability to make informed decisions early in the design time line in order to provide a feasible, viable and robust system to the customer. Increasingly, the issues of affordability, uncertainty in design and technology impact assessment are shaping the modern design environment. Current methodologies and techniques are not able to properly handle these issues. The research presented here builds on the authors?previous work which described an appropriate probabilistic design environment that allows for design in the presence of uncertainty as well as the infusion and assessment of new technologies. This environment is an essential part of a design methodology referred to as the Technology Identification, Evaluation and Selection (TIES) method. The objective of this research is to provide a comprehensive, structured, and robust methodology for decision making in the early phases of rotorcraft design. In this paper the authors will present a brief summary of the probabilistic design environment and introduce the steps that encompass the TIES methodology. The majority of the paper will be devoted to applying the Technology Impact Forecasting portion of this method to NASA? Short Haul Civil Tiltrotor.
(Georgia Institute of Technology, 1998-05)
Mavris, Dimitri N.; Baker, Andrew Paul; Schrage, Daniel P.
This paper describes a probabilistic design approach which has been formulated from an affordability viewpoint for the assessment of rotorcraft systems. This method places emphasis on the ability to rapidly examine the design space, identify constraint violations and provides insight as to how the feasible design space could be enlarged through the infusion of new technologies. The paper also provides a rationale as to why a probabilistic design approach is needed to properly examine and facilitate these assessments. The steps required to assess and provide for a technically feasible and viable design space are also outlined. Furthermore, thoughts as to how this technique could be used to investigate and account for tool fidelity modeling, technology readiness impact and benefit/risk/cost tradeoffs are also presented. Descriptions of candidate statistical and probabilistic techniques such as the Response Surface Method, Robust Design Simulation and Fast Probability Integration are provided as needed. Finally, the steps needed for the implementation of this methodology are presented for the design of a notional Civil Tiltrotor Transport.
(Georgia Institute of Technology, 1997-04)
Mavris, Dimitri N.; Baker, Andrew Paul; Schrage, Daniel P.
Beyond the Bell/Boeing 609, the next step in civil tiltrotor evolution will most likely be a larger capacity vehicle (~ 40 passenger class) similar to NASA? vision of a Short Haul Civil Tiltrotor (SHCT). This vehicle will be designed, built and operated in an era being shaped by today? increased emphasis on affordability. This paper discusses the authors?views on the subject and outlines the steps taken to develop a new methodology which will allow a true assessment of the affordability of such a SHCT. Affordability will not be defined by cost metrics alone. Instead, it will be based on the concept of value and tradeoffs between cost and mission effectiveness; measured by maintainability, reliability, safety, etc. In addition, the motivation for this shift in design philosophy and the resulting need for knowledge to be brought forward in the proposed methodology is reviewed. Furthermore, this shift in knowledge calls for a paradigm shift in the design evolution process based on the realization that decisions made during the early design phases are not deterministic in nature and should therefore be handled probabilistically. The approach taken acknowledges this need and defines a suitable probabilistic design environment. The fundamental building blocks of this method are also outlined and discussed including key concepts, tools, techniques, and the approach taken to implement this process.