Aerospace engineering is one of the most challenging engineering subjects in the world and probably tops the list. Any engineer reading this article may be familiar with the common design cycles involved in developing a product. But it's the level of complexity that makes aviation so challenging.
Modern aircraft designs face major operational, environmental and financial challenges. There is a huge paradigm shift being observed in the way complex systems are designed and how design errors can be avoided, as in the case of the latest Boeing 737 Max. In this article we discuss the flow of a modern aircraft design cycle and the cases on what. Using the services of a prototype maker for large-scale testing can save the day.
Discover more details about prototyping in industrial design here.
Design cycle of a modern aircraft
Any designer reading this article should be familiar with the three basic phases of design, namely Conceptual, Preliminary and Detailed Design. However, fierce competition among market players and high customer expectations mean that a company must produce notable innovations in the design stages to satisfy various criteria. Let's discuss the design cycle of an aircraft in terms of life cycle cost using the following diagram.
As you can see, the first three phases before the manufacturing phase represent 95% of the total cost. Of the first three phases, phase 1, planning and conception, is the most important. Therefore, we will focus in detail on the first phase, followed by the other two.
Planning and conception
The first step is a feasibility study that determines whether or not a requirement can be met with existing technology. Furthermore, the feasibility study also helps in optimizing the path of a project, that is, a complete redesign, which entails greater risk and cost, or adoption/modification of the existing project. The design phase then begins. Every aircraft designer is very familiar with the Raymer and Roskam models and, as they explain, the design phase involves answering the following fundamental questions:
- Will it work?
- What does it look like?
- What are the requirements?
- How can appointments be optimized?
- How can weight and costs be optimized?
The ultimate goal of the ideation phase is to identify and prepare a viable and ideal design concept for further refinement. This phase therefore involves the elaboration, study and investigation of various design concepts, with minimal knowledge of experimental results and limited data on the practicality of the design. The graph below this paragraph shows the greater uncertainty during the ideation phase compared to the advanced phases. What's more, a staggering 65% of lifecycle costs occur during this phase, meaning any subsequent changes to the basic design represent a reduction in overall revenue and an extension of deadlines.
The dilemma often faced in the design phase is starting a design program without a clear outline of the requirements to be met. It is very important to outline market needs and make customers explicit about their expectations. Refining requirements at a later stage is an uneconomical and inefficient approach and such a design cycle has a serious impact on the life cycle costs incurred. When designing an aircraft, there are multiple, often conflicting, customer requirements and expectations. A diverse and complex set of aircraft systems based on different parts of an aircraft, e.g. B. wings, engine, fuselage, landing gear, tail and canard represent numerous challenges.
Dealing with this is an art in itself and that is why such decisions are facilitated through techniques like Multiple Attribute Decision Making (MADM). Using such techniques, implicit considerations are brought into play and decision-making moves from a deterministic and centralized approach to a dynamic and parametric approach. Furthermore, techniques such as Multidisciplinary Analysis and Design Optimization are essential to deal with entangled constraints in such an environment. This technique is illustrated in the following diagram, which shows the interactions between different aviation disciplines.
Regarding uncertainty in the design phase, the established methods, as already mentioned, are based on probability theories and design methods. These methods include the use of Probability Density Functions (PDFs) and Cumulative Distribution Functions (CDFs) for each design constraint. Data for multiple design constraints are then presented and analyzed together. This cumulative data gives the designer a clear view of the design space and indicates whether he or she needs to relax a constraint or introduce a technology to improve the overall design cycle.
In short, the designer creates a relationship between input and output variables, taking into account the variability of input factors.
Initial draft
This phase is crucial to measure the various design factors of the concept established in the first phase. This requires in-depth study and analysis of the interdisciplinary interactions between the various systems and subsystems of an aircraft. For example, the concept of aeroelasticity is the combination of structural mechanics and aerodynamics.
In modern engineering, aspects such as reliability, maintainability, stability, control, safety and economy are also taken into consideration in the preliminary design phase. We will now discuss in more detail the challenges of this design phase and the ideal approach to overcome these challenges.
Sophisticated, complex and accurate modeling requires the use of sophisticated numerical algorithms, e.g. B. Computational fluid dynamics and finite element analysis. However, exceptionally high computing costs pose another challenge for developers. The following diagram visually shows the compromise that must be made when choosing high-precision tools over using simple simulations.
The move to complex, high-precision tools not only means higher computational costs, but also the challenge of considering multiple variables (often hundreds) and their interdependence. Therefore, a lot of time is spent identifying and mapping the simulation environment. (The story isn't over yet!!!)
If you are still interested in the content, read “Aircraft Design (Part 2): Expanded Horizons”. Thanks.
