Finite Element Modeling Strategies for Dynamic Aircraft Seats 2008-01-2272

Dynamic aircraft seat regulations are identified in the Code of Federal Regulations (CFR), 14 CFR Parts § 23.562 [1] and § 25.562 [2] for crashworthy evaluation of a seat in dynamic environment. The regulations specify full-scale dynamic testing on production seats. The dynamic tests are designed to demonstrate the structural integrity of the seat to withstand an emergency landing event and occupant safety. SAE standard AS 8049 [3] supports detailed information on dynamic seat testing procedure and acceptance criteria. Full-scale dynamic testing in support of certification is expensive and repeated testing due to failure drastically increases the expense. Involvement of impact environment, flexibility in interior configuration and complicated nature of seat engineering design makes this problem quite complex, so that classical hand calculations are practically impossible. Efforts have been made to improve the occupant safety and to reduce the testing costs through substantiation via computer modeling analysis techniques.

The goal of the Finite Element Analysis (FEA) in product development is not only to design a seat but to substantiate the certification tests or possibly replace the certification tests. The case of a certification by substantiation tests increases the necessity of validation of the Finite Element (FE) model. Advisory Circular (AC) 20-146 [4] demonstrates the methodology for dynamic seat “Certification By Analysis” for use in Parts 23, 25, 27 and 29 airplanes and rotorcraft. This AC provides guidance on how to validate the computer model and under what conditions the model may be used in support of certification or Technical Standard Order (TSO) approval/ authorization.

In this study, best FE modeling practices for dynamic aircraft seats are presented using explicit nonlinear FE code such as LS-DYNA [5, 6] with a brief case study of an aircraft passenger seat. Comparison of FEA results and test results indicate reasonable correlations, establishing confidence in the Dynamic Finite Element Analysis (DFEA) methodology.

Development in DFEA methodology helps aircraft industry in designing and certifying dynamic seats and interior configurations more economically and confidently. Objective of this paper is to provide simple guidelines for the aircraft seating industry in developing simulation techniques for the dynamic environment.