Implementation of a mass estimation method for the flight control system in conceptual aircraft design

Abstract

Te main goal of this thesis is to improve the present tool implemented in MICADO for calculating the weight of the flight control system, in order to get higher accuracy in the mass estimation during the preliminary aircraft design. To do so, Chapter 2 presented various methods available in the bibliography, including relevant information and details for all the equations to avoid ambiguity and error during implementation. In Chapter 3, different airplanes from which detailed flight controls weight data are available have been selected to apply and test the accuracy of the methods. The process revealed the im-portance of being accurate in every detail when applying the methods. Several sources have been required to obtain the parameters required to estimate the weight, and results have shown that it is increasing difficult to apply the methods as the sophistication of the methods increase. The Raymer method is characterized by its simplicity and produced overly optimistic results except for the CSR-01, whose estimation was accurate. The more sophisticated Torenbeek method proved very accurate for all the aircraft of the study except for the CSR-01, which calculated much higher results in comparison to the real weight values. The last method presented was the method developed in a NASA contractor report by Boeing. This method is the most complex and detailed, and it is based on statisti-cal data where Boeing aircraft are included, thus giving the most accurate results for the Boeing airplanes of the study, however, for the CSR-01 it returned a considerable overes-timation. In conclusion, the detailed methods available in the bibliography offer much better results for aircraft whose flight control system are driven mechanically than for the only aircraft of the study whose flight control system are driven by fly-by-wire. The high level of detail of the Boeing methods was a deciding factor for selection as the methods to be implemented in MICADO. A parameter sensitivity study was performed in Chapter 4 to understand the real nature of each method, and to understand which parame-ters are the most important in order to return accurate results. Later, in Chapter 5, MICADO was used to find the weight of the flight controls of the CSR-01. MICADO had already implemented the Boeing methods except for the high lift system, which already uses a very detailed method. The results obtained for the PFCS and the movable tailplane differed too much from the results obtained in Chapter 3 when using the same method for the same airplane, concluding that the methods were not implemented correctly. In any case, if the methods had been correctly implemented, the results would have still been inacceptable. Based on these results two tasks had to be performed: first, correctly imple-ment the Boeing methods and second, add additional reasonable considerations for fly-by-wire driven flight controls. Review of the code, proposed changes and new considerations suggested are highlighted throughout Chapter 5. Based on this study MICADO should keep the implemented method for the high-lift system, but with modifications. In Chapter 6, the results of the changes and suggestions made in Chapter 5 are presented and analyzed. It is shown that the current method implemented in MICADO calculates the weight according to the expected values for the Boeing methods, i.e. the methods are cor-rectly implemented after the modifications. Additionally, the weight obtained with the considerations related to the use of fly-by-wire are discussed and proved a reasonable and valid solution until more data of fly-by-wire driven flight controls weight is available.