Our senior year is broken into two semester-long courses: Preliminary and Detail Aircraft Design being the latter the culmination of the Bachelor’s program. This course is focused on the integration and application of all the skills and learning that the students have accrued. The semester is dedicated to the detailed design of aircraft components specified by industry. In particular, we partner with Gulfstream Aircraft Corporation who provides the requirements for a project which is of interest to them and they follow the development through virtual meetings and in person for the final presentation. Recent projects have consisted in the design of the wing boxes for a specific type of business jet. The students are responsible for loads calculation, development of efficient structural concepts, structural dimensioning and stress proofing, location and integration of systems, material selection, etc. This course is inspired by the principles of CDIO. However, by its very nature (a large, expensive aircraft component), the last two letters of CDIO cannot be put into practice directly. One way to address this problem would be to simplify the project to something that can be designed and tested in the university labs in one semester. But this solution would strip the students from the real world experience and the challenges that a real industrial problem entails. However, the alternative of having the students only perform a paper exercise, renders their education somewhat incomplete. Indeed, experience has shown that students become good at solving “canned” problems, at reproducing--sometimes uncritically--problem solving algorithms without the understanding of the underlying principles and, when confronted with open-ended design problems, these approaches are not sufficient or result in completely wrong answers. For example, when asked to design a structure to carry certain loads, the great majority of students automatically tries to apply Von Mises’ or Tresca’s criteria without first stopping to reflect whether those are really the failure modes for that type of structure under those loads and with that type of fixity. In many cases, localized buckling will happen much earlier than yielding but the students would be completely satisfied that their structure will carry the loads because they have produced positive “margins of safety” albeit based on the wrong failure criterion. To deal with this, at ERAU, we have introduced a two week mini-project at the beginning of the term in which the students design, build and test a cantilevered “wing box” (110x14x5cm), using only kitchen aluminum foil and glue, loaded with distributed sand bags. They have to design the box (trial and error is not acceptable) and submit a written technical report before they start any construction and then their designs are tested, thus demonstrating (or not) whether their assumptions and analyses were appropriate. An extra challenge constitutes a weight-not-to-exceed and the fact of being in competition with the other classmates. Thus it is perfect practice and complement for the big term-long project making Ae421 a well-rounded capstone course.
Proceedings of the 10th International CDIO Conference, Barcelona, Spain, June 15-19 2014