Aircraft Seat Design Indicators for Eliminating Economy Class Syndrome

Abstract

One of the serious risks for the passengers in the airplane cabin is the so-called economy class syndrome (ECS). It is caused by the combination of "deep vein thrombosis," in which a blood clot forms in a vein of the lower extremity due to poor blood flow caused by prolonged seating, and "pulmonary thromboembolism," in which a blood clot forms in a vein and flows into a pulmonary artery, causing an embolus in the pulmonary artery. Its main cause is thought to be a compression of the popliteal and femoral veins, which are deep veins in the lower extremities, due to the narrow seating environment over a long period. In past studies, experimental investigations have shown that a pressure reduction on the buttocks and thighs is desirable. Experiments have focused on the cushion materials used in aircraft seats. However, they have not been conducted on subjects with the physique of patients diagnosed with ECS or with a similar physique to them because it is often difficult to find such subjects. This study aims to develop a human body model based on the physique of a patient who suffered from ECS to conduct seating simulations using non-linear finite element analyses. Then, we aim to quantitatively identify the causes of ECS and to create a design index for an ideal shape and stiffness of a seat cushion based on the numerical simulations. In the numerical analyses, we verify the seat cushion model and the human body model created by structural analysis software with experimental data. It is important that two human body models: one of a patient diagnosed with ECS (elderly, female, obese body type) and the other of a normal person (male) are analyzed to drive the design index for an ideal seat.