Parametric study of head paths and HIC data for aircraft seat and cabin interior certification
Head Injury is one of the main reasons causing fatalities in air crashes. In the year 2005, of the total 3448 accidents reported in U.S. general and civil aviation, 655 have been fatal with a total of 1150 on-board fatalities. Head Injury being the most important component contributing to these statistics. One of the main obstructions which causes head impacts are the bulkheads dividing the cabin interiors. Bulkheads in an aircraft or a ship are usually the partitions mounted using the seat tracks and upper mountings that divide different classes or sections of an aircraft. But the actual function of the Bulkhead is to provide structural stability to the aircraft or the ship. When installed by the aircraft door, it protects passengers against the cold winds blowing from the airfield. The passengers sitting on the first row behind the bulkhead in the aircraft are less than three feet away from the bulkhead. Hence in the event of an air crash or an emergency landing the front row passengers seated directly behind bulkheads or cabin class dividers have the tendency to have a head and upper torso impact with the bulkhead making it important to study this criteria in order to reduce the HIC value or the Head Injury Criteria. There are other obstructions in the head paths during a crash inside the cabin interiors of an aircraft. These may cause severe head injuries and in many cases can even cause fatalities. A comprehensive study of the head path can prevent these injuries. This thesis presents a parametric study conducted on the head paths and head trajectories during a crash using Federal Aviation Regulations Part 25 and Part 23. This thesis also presents a parametric study of the properties of the bulkhead, the seat belt, the friction and the seat pitch, and how its variation affects the HIC (Head Injury Criteria) value and the trajectory of the head paths. The attempt is to find the ideal set of properties so as to minimize the HIC value. For example the stiffness of the bulkhead directly affects the structural stability of the aircraft. The more stiff the bulkhead the more strength it imparts to the fuselage and vice versa. But as the bulkhead used gets more stiff the higher is the corresponding value of HIC. The attempt of this experiment is to arrive at the best possible stiffness so as to avoid human fatalities at the same time impart the highest structural stability to the aircraft fuselage. For this purpose, front facing impact tests are simulated using S2 50th percentile Hybrid II human dummy model with a regular two point restraint system as is common in aircraft seating systems. Tests are conducted for a single seated occupant. Sets of parametric studies are conducted by varying the stiffness of the bulkhead, the coefficient of friction between the human dummy and the seat pan & backrest, the seat belt elongation properties and the seat pitch, so as to find the best, most safe combination of material properties for the an allowable HIC value and maximum structural stability.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering