CERTIFICATION BY ANALYSIS FOR AIRCRAFT SEATS UNDER CFR PARTS 23 AND 25 CATEGORIES

This paper addresses the experimental, mathematical modeling, using MADYMO (Mathematical Dynamic Model) software, and hybrid dynamic modeling of aircraft seat cushions for different deceleration pulses which are representing for various aircraft categories. Occupant lumbar load under CFR Part 23 and 25 is being obtained by using different methodologies including running full scale sled tests, employing quasi-static testing to measure material properties and using them in MADYMO and hybrid dynamic models. A crashworthy structure is designed such that in the event of crash, it absorbs impact energy in a controlled manner. All energy absorption materials such as honeycombs, polyurethane foams, polymer foams, metallic foams and so on are being used to make a safe and survivable trip for passengers and even sensitive instruments, equipments and computers in packaging applications. The main subsystems of an aircraft involved in crashworthiness are seat cushion, which is part of seat structure, restraints, fuselage and landing gear. Polyurethane foams are being used as acoustic purposes, as padding in the finished interior panels of the aircraft, and seat cushions. Their main application is mostly in seating purposes to provide comfort for occupant. Due to the fact that there is a direct interaction between the occupant body and the seat cushion, it has to be ergonomically comfortable as well as providing safety for passengers on board. All the seat cushions have to pass Federal Aviation Administration (FAA) Regulations before being installed on the seats. These regulations require a dynamic sled test of the entire seat system for certifying the seat cushions. This traditional dynamic testing is also required for replacing the deteriorated cushions with new buildup cushions which is time consuming and costly.

Keywords:

Aircraft crashworthiness , Seat cushion , Sled testing , Hybrid dynamic modeling , MADYMO , Lumbar load , Polyurethane foams