Certification by Analysis of a Typical Aircraft Seat

Advancements in computer hardware in recent years have made it possible to solve complex real world problems using finite element methods (FEM). Full scale dynamic certification testing of aircraft seats is a very complex, expensive and time consuming process. A high acceleration pulse is applied on the seat structure in a short duration of period, and the seat structure has to pass stringent FAA certification criteria. FAA and the aircraft industry are working together to reduce the cost and time required for certification of the seat while improving occupant safety. This is being achieved by using a process known as Certification by Analysis or CBA where the seat is certified using finite element methods. The process and guidelines for CBA are described in advisory circular AC 20-146 developed by the FAA. As per the AC 20-146, FE models can replace the actual dynamic testing scenarios such as: 1) demonstrating compliance to standard test requirements for changes to a baseline seat design, 2) establishing the critical seat installation/configuration in preparation for dynamic testing. This paper describes in detail different techniques that can be used for the validation of a FE model of typical aircraft seat using the finite explicit code LS DYNA. As an example, the FE model of an aircraft seat is validated against the full scale dynamic test conducted as per AC 25.562.