Development of a Component Head Injury Criteria (HIC ... - FAA

In general, it appears that for simple geometries, such as panels, the NHCT device tends to
produce results that are close but slightly greater than the results from FSSTs. Thus, HIC for the
NHCT are conservative for the cases tested.
The effects causing descrepancies can be categorized into the following groups:
• Variations in the behavior of the test articles. These variations, such as unpredictable
inertia-induced flexing of tall divider panels or different failure modes of tray tables, are
unavoidable and difficult to correct.
• Variations caused by kinematic approximations in the NHCT. While the NHCT
approximates a kinematic copy of the 50 th percentile male Hybrid II ATD as closely as
possible, some differences are present, such as lack of a flexible neck, incompressible
spine, and a different lower torso friction properties. Simulations have shown that while
the contribution of a flexible neck to the HIC may not be a substantial contributing factor
in causing HIC values to vary from FSST values for simple target geometries, it could
have a more pronounced effect for more complex targets, such as seat backs with tray
tables. Designs for rectifying these limitations are available and can be implemented
with relative ease.
• Variations in FSST-NHCT test conditions. As noted previously, HIC in general is
extremely sensitive to test parameters, i.e., impact velocity and impact angle. This being
the case, one would expect that validation of the NHCT would be difficult using a one-toone
comparison of the FSST and NHCT test data.
11. REFERENCES.
1. Chandler, R.F., “Human Injury Criteria Relative to Civil Aircraft Seat and Restraint
Systems,” SAE Paper 851847, Society of Automotive Engineers, Warrendale, PA, 1985.
2. Lissner, H.R., Lebow, M., and Evans, F.G., “Experimental Studies on the Relation
Between Acceleration and Intracranial Pressure Changes in Man,” Surgery, Gynecology,
and Obstetrics, V. 111, 1960, pp 329-338.
3. Gadd, C.W., “Use of a Weighted Impulse Criterion for Estimating Injury Hazard,” SAE
Paper 660793, Proceedings of the Tenth Stapp Car Crash Conference, Society of
Automotive Engineers, Warrendale, Pennsylvania, 1966, pp. 16-174.
4. Versace, J., “A Review of the Severity Index,” SAE Paper 710881, Proceedings of the
Fifteenth Stapp Car Crash Conference, Society of Automotive Engineers, Warrendale,
Pennsylvania, 1971, pp. 771-796.
5. Gurdjian, E.S., Lissner, H.R., Latimer, F.R., Haddad, B.F., and Webster, J.E.,
“Quantitative Determination of Acceleration and Intercranial Pressure in Experimental
Head Injury,” Neurology 3,4, 1953, pp. 4223.
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