Current percentiles used by regulatory bodies to gauge passenger size and test the safety of aircraft seats are significantly out of date and not representative of a growing population.
In his paper, An Anthropometric Comparison of Current ATDs with the US Adult Population, Dr. Matthew P. Reed, Ph.D., indicates that the size of ATDs (crash test dummies) vary greatly from the body types of the actual population.
These dummies were configured based on population size data from the 1970s. The weight standard for the mid-sized male model intended to represent 50% of the population only represents 29% of the male population (based on CDC data from 2008). The female mid-size model only represents the weight of 33% of the female population according to the same 2008 data from the CDC.
Dr. Reed, who serves as Research Professor and Head of the Biosciences Group at the University of Michigan Transportation Research Institute (UMRI), tells us that it is widely recognized that the size of the median population in markets like the US, UK, and EU have increased and are expected to continue to increase. The figures used to validate ATDs are below the current population measures in height as well, but weight has the highest rate of discrepancy by far.
The size of the test subject affects the test results significantly, Dr. Reed tells us. Without the proper ATDs, data gathered on HIC (head impact criterion), and other potential risks like organ damage caused by abdominal injury and paralysis caused by lumbar or lower extremity injury cannot be adequately determined during aircraft seat testing.
The way aviation dynamic tests are configured, he said, are designed more as an evaluation of the structural integrity of the seat rather than providing any significant analysis of potential injury to passengers.
There is active dialogue in the transportation community about changes required to update the various ATD models more in keeping with current population measures, but until the transportation industry updates the dimensions of the ATDs, aviation testing parameters are unlikely to change.
Meanwhile, it may surprise passengers to learn that placing aircraft seats closer to bulkheads can actually decrease the risk of head injuries. This is because the velocity of impact is actually lower the closer you are to the bulkhead. It’s unrealistic to think that there will be no head impact, Dr. Reed tells us. The uncontrollable crash conditions make it likely passengers heads hit the structure in front of them, but injury can be significantly reduced when seats are placed closer to the bulkhead so long as those structures are properly padded. He refers us to the FMVSF Test Procedure 201 standards established in the automotive field and specifies that adequate padding is very effective in reducing the risk of head injury.
Bulkheads in aircraft have been padded before, as a decorative feature, but properly padded bulkhead panels may actually be a better injury prevention measure than proposed bulkhead mounted airbags. When we asked Dr. Reed to look at images recently supplied to the Runway Girl Network of proposed bulkhead mounted airbags, he commented that the airbag shown in the picture seemed inadequate. There is no controlled forward movement of the body during an actual crash, he explained, so there is no guarantee that the passenger’s head would impact the bulkhead in the area which the airbags cover. Seat belt-based airbags currently installed on select aircraft seats provide better coverage, because they are larger and wrap around the passenger’s body.
Dr. Reed suggested that aviation could easily incorporate an automotive standard test for HIC which involves a “free-flying head form” test model. The free-flying head model is cast at the hard surface at random, which better reflects crash conditions and evaluates the effectiveness of padding.