http://hdl.handle.net/10057/23 http://soar.wichita.edu:8080/dspace/retrieve/32 http://hdl.handle.net/10057/23 Search the Channel s http://soar.wichita.edu:8080/dspace/simple-search http://hdl.handle.net/10057/2074 title: An integrated system for transport aircraft cabin interior design and certification by analysis authors: Nagarajan, Harishanker <br>abstract: Every cabin configuration, in all types of aircraft (Transport, General Aviation and Rotorcraft), need to be certified as per the existing Code of Federal Regulation governing that particular type of aircraft. The current practice used to comply with Federal Aviation Regulations (FAR’s) related to aircraft seats and cabin interiors is to conduct full-scale system sled tests. This approach can be expensive and the test results are sensitive to changes in test conditions, such as the sled pulse, dummy calibration, seat belt elongation, etc., resulting in scatter in the results. With the development of the more robust codes for the analytical tools, it should be possible to successfully capture the test conditions by one of these tools and to obtain results which compare favorably with the actual tests results. For Part 25 category of transport aircrafts, 14CFR 25.562 states: “Each seat type design which approved for crew or passenger occupancy during takeoff and landing must successfully complete dynamic tests or be demonstrated by rational analysis based on dynamic tests of a similar type seat, in accordance with each of the following emergency landing conditions” and then the conditions are stated. When these federal regulations were enacted, the ability of analytical tools was limited and there did not exist enough data to show that certification could be performed using analysis. The objectives of this research are to identify the conditions under which a Part 25 type aircraft could be certified by analysis for compliance with the 14 CFR 25.562 regulation, and also to identify the validation criteria when using analytical tools. The validation criteria for the analytical model have been developed based on the scatter that is seen in actual testing. The underlying premise is that the analytical modeling of the testing should be allowed to predict the injury criteria within the same band of scatter as the actual tests. The study develops a validated model and this model is shown to be robust in predicting the protection/injury criteria that the tested configurations offer. Using these validated models, a full factorial design of experiment (DOE) analysis was performed to determine the effect the factors have on the dynamic response of the seat-dummy-restraint-cabin systems. In this study, the factors chosen were the seat cushion type, thickness of the cushion and the rigidity of the seat for the 14 CFR 25.562 Test -1 condition (up test) and the studied response was the resulting lumbar load. For 14 CFR 25.562 Test -2 condition (down test), the studied factors were the seat set back distance, seat belt type, type of bulkhead and the coefficient of friction of the impact surface, while the studied response was the resulting Head injury criteria (HIC) based on the impact of the dummy head with the frontal structure. Guidelines were developed in this study pertaining to the circumstance under which analytical tools could be considered as a valid replacement for the certification testing. Based on the sensitivity study, a new integrated analytical system methodology has been developed that would help the aerospace cabin interior designers in developing crashworthy cabin interiors. A graphical user interface was developed which would help the cabin interior designers to optimize their design by selecting component that would help in minimizing the injury criteria studied. This would reduce the time it takes to design these configurations and would reduce the cost of certification while improving the safety of the flying public. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical engineering <br> Fri, 28 Nov 2008 22:58:59 GMT http://hdl.handle.net/10057/2074 title: An integrated system for transport aircraft cabin interior design and certification by analysis authors: Nagarajan, Harishanker <br>abstract: Every cabin configuration, in all types of aircraft (Transport, General Aviation and Rotorcraft), need to be certified as per the existing Code of Federal Regulation governing that particular type of aircraft. The current practice used to comply with Federal Aviation Regulations (FAR’s) related to aircraft seats and cabin interiors is to conduct full-scale system sled tests. This approach can be expensive and the test results are sensitive to changes in test conditions, such as the sled pulse, dummy calibration, seat belt elongation, etc., resulting in scatter in the results. With the development of the more robust codes for the analytical tools, it should be possible to successfully capture the test conditions by one of these tools and to obtain results which compare favorably with the actual tests results. For Part 25 category of transport aircrafts, 14CFR 25.562 states: “Each seat type design which approved for crew or passenger occupancy during takeoff and landing must successfully complete dynamic tests or be demonstrated by rational analysis based on dynamic tests of a similar type seat, in accordance with each of the following emergency landing conditions” and then the conditions are stated. When these federal regulations were enacted, the ability of analytical tools was limited and there did not exist enough data to show that certification could be performed using analysis. The objectives of this research are to identify the conditions under which a Part 25 type aircraft could be certified by analysis for compliance with the 14 CFR 25.562 regulation, and also to identify the validation criteria when using analytical tools. The validation criteria for the analytical model have been developed based on the scatter that is seen in actual testing. The underlying premise is that the analytical modeling of the testing should be allowed to predict the injury criteria within the same band of scatter as the actual tests. The study develops a validated model and this model is shown to be robust in predicting the protection/injury criteria that the tested configurations offer. Using these validated models, a full factorial design of experiment (DOE) analysis was performed to determine the effect the factors have on the dynamic response of the seat-dummy-restraint-cabin systems. In this study, the factors chosen were the seat cushion type, thickness of the cushion and the rigidity of the seat for the 14 CFR 25.562 Test -1 condition (up test) and the studied response was the resulting lumbar load. For 14 CFR 25.562 Test -2 condition (down test), the studied factors were the seat set back distance, seat belt type, type of bulkhead and the coefficient of friction of the impact surface, while the studied response was the resulting Head injury criteria (HIC) based on the impact of the dummy head with the frontal structure. Guidelines were developed in this study pertaining to the circumstance under which analytical tools could be considered as a valid replacement for the certification testing. Based on the sensitivity study, a new integrated analytical system methodology has been developed that would help the aerospace cabin interior designers in developing crashworthy cabin interiors. A graphical user interface was developed which would help the cabin interior designers to optimize their design by selecting component that would help in minimizing the injury criteria studied. This would reduce the time it takes to design these configurations and would reduce the cost of certification while improving the safety of the flying public. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical engineering <br> Fri, 28 Nov 2008 22:58:59 GMT http://hdl.handle.net/10057/2069 title: A methodology for aircraft seat certification by dynamic finite element analysis. authors: Bhonge, Prasannakumar <br>abstract: Dynamic aircraft seat regulations are identified in the Code of Federal Regulations 1(CFR), 14 CFR Parts 23.562 and 25.562 for crashworthy evaluation of a seat in a 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. The Society of Automotive Engineers (SAE) standard, AS8049, supports detailed information on dynamic seat testing procedures and acceptance criteria. Full-scale dynamic testing in support of certification is expensive and repeated testing due to failures drastically increases the expense. Involvement of impact environments, flexibility in interior configurations and complexity of seat engineering designs make analysis of these problems 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. Development in Dynamic Finite Element Analysis (DFEA) methodology helps the aircraft industry in designing and certifying seats and other interiors more economically and confidently. The objective of this study is to provide a methodology for aircraft seat certification by using DFEA techniques. The goal of the Finite Element Analysis (FEA) in product development is not only to design a seat but also to substantiate the certification tests or replace the certification tests. The case of a certification by substantiation tests increases the necessity of validation of the Finite Element model. The US government Advisory Circular (AC) 20-146 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 and same validation process utilizes in this research work. In the methodology of this dissertation, the seat certification process for business jet aircraft is defined in 3 stages: 1. Evaluation of seat critical options by using a simple FE – one-dimensional (1D) seat model, 2. Non linear FE analysis of seat worst loading condition and validation with the test results, 3. Substantiation of certification test or tests by using validated FE model and updation of the certification plan. Best FE modeling practices for dynamic aircraft seats, material testing procedures and component validation are presented here using nonlinear FE codes such as the LS-DYNA, with two case studies of aircraft passenger seats. Case 1 - Combined Vertical / Longitudinal velocity change dynamic test condition (15g side facing passenger seat – Part 23). Case 2 - Longitudinal velocity change dynamic test condition, (16g forward facing business jet passenger seat – Part 25). Comparisons of the DFEA and test results indicate reasonable correlations, establishing confidence in the DFEA methodology. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical Engineering <br> Fri, 28 Nov 2008 22:58:59 GMT http://hdl.handle.net/10057/2069 title: A methodology for aircraft seat certification by dynamic finite element analysis. authors: Bhonge, Prasannakumar <br>abstract: Dynamic aircraft seat regulations are identified in the Code of Federal Regulations 1(CFR), 14 CFR Parts 23.562 and 25.562 for crashworthy evaluation of a seat in a 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. The Society of Automotive Engineers (SAE) standard, AS8049, supports detailed information on dynamic seat testing procedures and acceptance criteria. Full-scale dynamic testing in support of certification is expensive and repeated testing due to failures drastically increases the expense. Involvement of impact environments, flexibility in interior configurations and complexity of seat engineering designs make analysis of these problems 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. Development in Dynamic Finite Element Analysis (DFEA) methodology helps the aircraft industry in designing and certifying seats and other interiors more economically and confidently. The objective of this study is to provide a methodology for aircraft seat certification by using DFEA techniques. The goal of the Finite Element Analysis (FEA) in product development is not only to design a seat but also to substantiate the certification tests or replace the certification tests. The case of a certification by substantiation tests increases the necessity of validation of the Finite Element model. The US government Advisory Circular (AC) 20-146 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 and same validation process utilizes in this research work. In the methodology of this dissertation, the seat certification process for business jet aircraft is defined in 3 stages: 1. Evaluation of seat critical options by using a simple FE – one-dimensional (1D) seat model, 2. Non linear FE analysis of seat worst loading condition and validation with the test results, 3. Substantiation of certification test or tests by using validated FE model and updation of the certification plan. Best FE modeling practices for dynamic aircraft seats, material testing procedures and component validation are presented here using nonlinear FE codes such as the LS-DYNA, with two case studies of aircraft passenger seats. Case 1 - Combined Vertical / Longitudinal velocity change dynamic test condition (15g side facing passenger seat – Part 23). Case 2 - Longitudinal velocity change dynamic test condition, (16g forward facing business jet passenger seat – Part 25). Comparisons of the DFEA and test results indicate reasonable correlations, establishing confidence in the DFEA methodology. <br>description: Wichita State University, College of Engineering, Dept. of Mechanical Engineering <br> Fri, 28 Nov 2008 22:58:59 GMT