CONTEXT AND TASKING
In 2007, the Secretary of Defense asked the Director of Operational Test and Evaluation (DOT&E) to take over the responsibility to prescribe policy and procedures for the conduct of live-fire test and evaluation of body armor and helmets. A 2009 report by the Department of Defense’s (DoD) Inspector General recommended that the DOT&E “develop for Department-wide implementation a standard test operations procedure for body armor inserts” that includes “statistical specification of probability of performance and associated confidence in that performance” (DoD IG, 2009). As a result of this recommendation, DOT&E developed and published statistically based test protocols for body armor and for combat helmets, in April and December, 2010, respectively.
In June 2012, Rep. Louise Slaughter (D-NY) sent a (Slaughter, 2012)1 to Secretary of Defense Leon Panetta expressing concerns that the new protocol2 for ballistic testing for the Advanced Combat Helmet (ACH) posed “an unacceptably high risk” for such protective equipment. Dr. Michael Gilmore, DOT&E, responded to Rep. Slaughter’s letter (Gilmore, 2012)3 on July 13, 2012. As part of this response, he noted that DOT&E would request the assistance of the National Academies’ National Research Council (NRC) to determine the adequacy of the ballistic helmet testing methodology.
The NRC set up the Committee on Review of Test Protocols Used by the DoD to Test Combat Helmets to consider the technical issues relating to test protocols for military combat helmets and prepare a report. The statement of task for the committee is as follows:
• Evaluate the adequacy of the Advanced Combat Helmet test protocol for both first article testing and lot acceptance testing, including its use of the metrics of probability of no penetration and the upper tolerance limit (used to evaluate backface deformation).
• Evaluate the appropriate use of statistical techniques (e.g., rounding numbers, choosing sample sizes, or test designs) in gathering the data.
• Evaluate the adequacy of the current helmet testing procedure to determine the level of protection provided by current helmet performance specifications.
• Evaluate procedures for the conduct of additional analysis of penetration and backface deformation data to determine whether differences in performance exist.
• Evaluate the scope of characterization testing relative to the benefit of the information obtained.
This report is the result of the committee’s deliberations.
The ACH was introduced by the Army in 2002 and continues to be produced. The advance production order was for 1.08 million helmets, and these are in sustainment. When a manufacturer proposes to produce ACHs for the Army, it submits a sample for first article testing (FAT). If the helmet design passes the FAT, the manufacturer will start production. The produced helmets must be subjected to a lot acceptance test (LAT) for a quality check before the lot is accepted.
The FAT process involves a suite of ballistic shots, with the primary one being 9-mm shots at a specified velocity and at specified helmet locations. Two measures are used to assess the performance of helmets during the test process:
1The full text of Rep. Slaughter’s letter to Secretary Panetta is in Appendix A.
2The December 7, 2010, protocol for first article testing is superseded by the September 20, 2011, protocol for first article testing. This protocol, including the May 4, 2012, protocol for lot acceptance testing, is found in Appendix B.
3The full text of Director Gilmore’s response to Rep. Slaughter is in Appendix A.
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Summary CONTEXT AND TASKING combat helmets and prepare a report. The statement of task for the committee is as follows: In 2007, the Secretary of Defense asked the Director of Operational Test and Evaluation (DOT&E) to take over the • Evaluate the adequacy of the Advanced Combat Hel- responsibility to prescribe policy and procedures for the met test protocol for both first article testing and lot conduct of live-fire test and evaluation of body armor and acceptance testing, including its use of the metrics of helmets. A 2009 report by the Department of Defense’s probability of no penetration and the upper tolerance (DoD) Inspector General recommended that the DOT&E limit (used to evaluate backface deformation). “develop for Department-wide implementation a standard • Evaluate the appropriate use of statistical techniques test operations procedure for body armor inserts” that (e.g., rounding numbers, choosing sample sizes, or includes “statistical specification of probability of perfor- test designs) in gathering the data. mance and associated confidence in that performance” (DoD • Evaluate the adequacy of the current helmet testing IG, 2009). As a result of this recommendation, DOT&E procedure to determine the level of protection pro- developed and published statistically based test protocols for vided by current helmet performance specifications. body armor and for combat helmets, in April and December, • Evaluate procedures for the conduct of additional 2010, respectively. analysis of penetration and backface deformation In June 2012, Rep. Louise Slaughter (D-NY) sent a etter l data to determine whether differences in performance (Slaughter, 2012)1 to Secretary of Defense Leon Panetta exist. expressing concerns that the new protocol 2 for ballistic • Evaluate the scope of characterization testing relative testing for the Advanced Combat Helmet (ACH) posed to the benefit of the information obtained. “an unacceptably high risk” for such protective equip- ment. Dr. Michael Gilmore, DOT&E, responded to Rep. This report is the result of the committee’s deliberations. Slaughter’s letter (Gilmore, 2012)3 on July 13, 2012. As part of this response, he noted that DOT&E would request the assistance of the National Academies’ National Research CURRENT PROTOCOLS Council (NRC) to determine the adequacy of the ballistic The ACH was introduced by the Army in 2002 and helmet testing methodology. continues to be produced. The advance production order The NRC set up the Committee on Review of Test Proto- was for 1.08 million helmets, and these are in sustainment. cols Used by the DoD to Test Combat Helmets to consider When a manufacturer proposes to produce ACHs for the the technical issues relating to test protocols for military Army, it submits a sample for first article testing (FAT). If the helmet design passes the FAT, the manufacturer will 1The start production. The produced helmets must be subjected full text of Rep. Slaughter’s letter to Secretary Panetta is in Ap- pendix A. to a lot acceptance test (LAT) for a quality check before the 2The December 7, 2010, protocol for first article testing is superseded lot is accepted. by the September 20, 2011, protocol for first article testing. This protocol, The FAT process involves a suite of ballistic shots, with including the May 4, 2012, protocol for lot acceptance testing, is found in the primary one being 9-mm shots at a specified velocity Appendix B. and at specified helmet locations. Two measures are used to 3The full text of Director Gilmore’s response to Rep. Slaughter is in Appendix A. assess the performance of helmets during the test process: 1
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2 REVIEW OF DEPARTMENT OF DEFENSE TEST PROTOCOLS FOR COMBAT HELMETS n c 1.0 20 0 240 17 n sample size 0.8 c acceptance number Probability of Acceptance 0.6 0.4 0.2 0.0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 Probability of Penetration FIGURE S-1 Operating characteristic curves for the Army’s and the Director of Operational Test and Evaluation’s first article testing pro- tocols for penetration. The blue lines show the probabilities of acceptance for the two plans when the true probability of penetration is 0.1. resistance to penetration (RTP) and backface deformation 90/90 standard in Director Gilmore’s letter and elsewhere (BFD).4 by DOT&E: If the probability of non-penetration is 0.9 or The original Army FAT protocol consisted of 20 9-mm less, then the helmet design has at least a 90 percent chance shots (four helmets and shots at five specified locations on a of failing the FAT. helmet). The helmets were all the same size, and one helmet In developing its protocol, DOT&E decided to increase each was exposed to one of four environmental conditions. the number of helmets tested from 4 to 48. Five shots were A manufacturer’s helmet design was deemed to pass FAT taken at five different locations on a helmet (as was the case for penetration if there were zero penetrations out of the 20 with the Army’s protocol), leading to a total of n = 240 shots. shots. This is an example of a c-out-of-n test plan in the sta- DOT&E applied the same 90/90 standard to get the number tistical quality control literature; in this case, c = 0 and n = 20. of acceptable penetrations as c = 17. In other words, the The properties of a test plan can be obtained from its helmet design passes FAT if there are17 or fewer penetra- operating characteristic (OC) curve, which is a plot of the tions in 240 shots and fails otherwise. The dashed red curve probability of passing the test (y-axis) as a function of the in Figure S-1 shows the OC curve for this plan developed penetration probability of a single shot (x-axis). The solid by DOT&E. It can be seen that, if the true probability of black curve in Figure S-1 gives the OC curve for the Army’s penetration is 0.10, the probability of acceptance equals 0.10 0-out-of-20 plan. The blue line shows that, if the true prob- (satisfying the 90/90 standard). ability of penetration is 0.10, the probability of passing the It is this change in the protocol, from zero penetrations test is about5 0.10. This property has been referred to as the (out of 20 shots) to allowing as many as 17 penetrations (out of 240 shots), that resulted in Rep. Slaughter’s concern with 4RTP is a binary outcome indicating whether or not there is a complete the safety of Army combat helmets. In his response, Direc- penetration of the helmet shell. BFD is measured by the maximum depth of tor Gilmore noted that DOT&E’s plan had (essentially6) the the deformation that is imprinted by the helmet on the clay surface of the same 90/90 property as the Army’s legacy plan. Further, it headform. (Formal definitions are given in Chapter 5.) 5The actual probability of acceptance for the 0-out-of-20 plan is slightly had better statistical properties because a larger number of higher than 0.10. The 0-out-of-22 plan is closer to the 90/90 standard. This was noted in Dr. Gilmore’s response to Rep. Slaughter. 6See footnote 5.
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SUMMARY 3 n c 1.0 20 0 240 17 n sample size 0.8 c acceptance number Probability of Acceptance 0.6 0.4 0.2 0.0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 Probability of Penetration FIGURE S-2 Further comparisons of the operating characteristic curves for the Army’s and the Director of Operational Test and Evaluation’s first article testing protocols for penetration. The blue lines show the probabilities of acceptance for the two plans when the true probability of penetration is 0.1; the purple and green lines show the corresponding acceptance probabilities when the true penetration probabilities are, respectively, 0.005 and 0.05. helmets and multiple helmet sizes were tested under different letter, there are indeed advantages associated with increasing environmental conditions, and, therefore, the new protocol the number of helmets tested. was an improvement. However, a key issue is whether the 90/90 standard, which was used to develop the protocol, is appropriate. In addition, that standard specifies only one point on the OC curve in Comparison of FAT Protocols for Penetration developing the test plan, but, in fact, the whole curve and the The committee first considers FAT protocols for RTP plan’s incentives and risks need to be considered. Figure S-2 because these were the focus of the correspondence between provides a re-examination of the OC curves for the Army’s Rep. Slaughter and Director Gilmore. FAT protocols involv- and DOT&E’s protocols. As in Figure S-1, the black curve ing BFD are discussed in Chapter 7. LAT protocols for both is for the Army’s 0-out-of-20 plan, and the red curve is for RTP and BFD are considered in Chapter 8. DOT&E’s 17-out-of-240 plan. Each curve shows how the The committee emphasizes an obvious point: The Army’s probability of accepting a helmet design (y-axis) varies as legacy protocol allowed zero penetrations in 20 shots, but the underlying probability of penetration (x-axis) varies. As that did not imply that a helmet design that passes FAT has noted in Figure S-1, the two curves cross at a point close zero probability of penetration. to penetration probability of 0.10 (blue line). To the left of Further, there are good statistical reasons to justify this curve, DOT&E’s plan (in red) has higher probabilities DOT&E’s increase in the number of helmets tested to 48 of acceptance (passing FAT); to the right it has lower prob- helmets from the Army’s 5. One gets more precise estimates abilities. In other words, the DOT&E’s plan is less stringent of the penetration probability from 240 shots than 20 shots. (easier to pass) than the original 0-out-of-20 plan if the actual In addition, DOT&E’s plan allows better statistical com- penetration probability is less than 0.10 and more difficult parison of possible differences between helmet sizes and to pass if the penetration probability is higher than 0.10. environmental conditions. So, as pointed out in Dr. Gilmore’s However, as we will see below, there are more pertinent pen- etration probabilities at which the plans should be compared.
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4 REVIEW OF DEPARTMENT OF DEFENSE TEST PROTOCOLS FOR COMBAT HELMETS Data made available to the committee show that manu- Operational Test and Evaluation (DOT&E), should use this facturers are currently producing ACHs with penetration information to set the appropriate standard for performance probabilities around 0.005 or less (overall, there were 7 pen- metrics in the test protocols. In the absence of such a sci- etrations in 12,147 shots; see Chapter 5). This corresponds to entific basis, DOT&E should develop a plan that provides the purple line in Figure S-2. At this penetration probability assurance that it leads to the production of helmets that are of 0.005, the probability of passing the FAT is close to 1.0 for at least as penetration resistant as currently fielded helmets. DOT&E’s protocol (red curve), while it is about 0.9 for the Army’s legacy protocol (black curve). So the manufacturer’s Director Gilmore’s response to Rep. Slaughter notes that risks (probabilities of not passing the FAT) at a penetration the “Services and the U.S. Special Operations Command probability of 0.005 are zero and 0.1 respectively. These are have endorsed the 90/90 standard for no perforation.”7 relatively small values, as they should be. Despite this assurance, the committee is concerned that Consider the green line in Figure S-2 that corresponds to a DOT&E’s protocol may have unintended consequences. penetration probability of 0.05, an order of magnitude higher As noted earlier, under the new DOT&E protocol, there is than the current penetration level of 0.005. For this value, the a high probability of passing the test even if the penetration DOT&E’s plan (red curve), has an acceptance probability of probability is an order of magnitude higher than the current about 0.95, while the Army’s legacy plan (black curve) has levels. Therefore manufacturers may not have an incentive to a probability of about 0.38. In other words, if manufacturers sustain the current levels of penetration resistance. produce helmets with a penetration probability of 0.05 (as Of course, future designs of helmets may involve other noted, an order of magnitude higher than the current level), considerations such as lower weight and added mobility. It they have a 95 percent chance of passing the FAT under the is possible that manufacturers and the government have to current DOT&E protocol; that is, the government’s risk is compromise on the penetration probability levels in order to 0.95. In comparison, the government’s risk under the Army’s produce lighter helmets. However, the added benefits of such legacy plan is 0.38. design changes would have to be studied and demonstrated So the question comes down to the following: What is the before one accepts higher levels of penetration. In the case appropriate level of penetration probability at which the gov- of the ACH, there have been no such design changes. ernment’s risk should be controlled? By selecting the 90/90 standard, DOT&E has set this penetration probability at 0.10, The Army’s Modified Protocol a value that is roughly two orders of magnitude greater than where the manufacturers are currently operating. In 2012, with DOT&E’s approval, the Army modified the Now, for business reasons, the manufacturers would want 17-out-of-240 plan to a two-stage protocol. The two stages to design a helmet that has a high chance of passing the test involve conducting a 0-out-of-22 plan in the first stage, and, while meeting the other helmet criteria such as weight. If if the helmet design passes this test, then a second 17-out- there is a high probability of passing the test, even if the of-218 plan is used, for a total of 240 shots and a combined penetration probability is an order of magnitude higher than acceptable number of penetrations of 17. The first stage, the the current levels, manufacturers may not have an incentive 0-out-of-22 plan, is slightly more stringent than the Army’s to sustain the current levels of penetration-resistance, and, 0-out-of-20 legacy plan, so this modified plan provides an hence, helmet safety could possibly be degraded. incentive for manufacturers to achieve a penetration prob- As noted in Chapters 3, 6, and 10, there is currently no ability of 0.005 or less. scientific basis for linking performance metrics to brain injuries. The report notes, in Chapter 3 and elsewhere, that Finding 6-4. The Army’s modified plan satisfies the criterion there is a need to initiate research that connects performance that it provides an incentive for manufacturers to produce metrics to brain injuries. helmets that are at least as penetration-resistant as current helmets. Recommendation 3-4. The Department of Defense should vigorously pursue efforts to provide a biomedical basis for The second stage of this plan allows 17 penetrations assessing the risk of helmet backface injuries. out of 218 shots, or equivalently, a penetration probability level of 17/218 = 0.08. However, a helmet design with 0.08 While these links are being developed, it is important penetration probability has a very small chance of being that the performance of new helmet systems is at least as good as previous helmet systems, as measured by current 7Director Gilmore’s letter, reprinted in Appendix A, also noted, “The performance metrics. N ational Research Council (NRC), in its recent independent technical review of the Department’s testing of body armor, indicated that this approach to Recommendation 6-2. If there is a scientific basis to link testing is scientifically defensible.” It should be emphasized, however, that the brain injury with performance metrics (such as penetra- Committee on Testing of Body Armor Materials for Use by the U.S. Army— Phase III did not explicitly endorse the 90/90 standard. Further, the standards tion frequency and backface deformation), the Director of for helmets should be determined independently of those for body armor.
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SUMMARY 5 accepted in the first stage, so the two-stage plan will reject such a helmet design. Recommendation 7-1. The Director of Operational Test and Evaluation should revert to the more transparent and robust analysis of backface deformation data based on pass/fail CONSIDERATIONS IN DEVELOPING NEW PROTOCOLS scoring of each measurement. Although the Army’s modified protocol can be a short- term solution, the committee encourages DOT&E to consider However, it is important to conduct post-test analysis of the the various findings and recommendations in the report and continuous BFD measurements and monitor them over time. develop a better alternative to its current protocols. These findings and recommendations are described in Chapters 5 Recommendation 7-3. The Office of the Director, Opera- through 9 of the report. Some of the important considerations tional Test and Evaluation, and the Services should analyze identified in the report include the following: the continuous backface deformation measurements, com- pute the margins, and track them over time to assess any • What is the appropriate level at which government’s changes over time. risk should be controlled? The 90/90 standard implies that it should be controlled at a penetration probability • The different-sized helmets are intrinsically different of 0.10. However, manufacturers are currently produc- products with different shells, molds, and manufac- ing ACHs with a penetration probability of around turing settings, and consideration should be given to 0.005 or less, which is substantially lower than 0.10. testing them separately. Further, separating by helmet sizes will simplify some of the complexities associ- Recommendation 6-3. The government’s risk should be ated with current test processes. controlled at much lower penetration levels than the 0.10 value specified by the 90/90 standard. Recommendation 5-5. Current Office of the Director, Operational Test and Evaluation, protocols should be revised • When DoD adopts new helmets with changes to the and implemented separately by helmet size. design (such as lighter weight and added mobility), it will be necessary to reevaluate the protocols. For • Data made available to the committee indicate that example, it may not be possible for manufactur- there may be considerable differences in the distribu- ers to produce lighter helmets at current levels of tions of the BFD data across helmet sizes and shot penetration. locations. DOT&E is considering the use of prelimi- nary hypothesis tests on BFD data and pooling the Recommendation 9-1. When combat helmets with new data across the different settings if the hypotheses are designs are introduced, the Department of Defense should not rejected. The committee has reservations about conduct appropriate characterization studies and cost-benefit the use of such procedures. The changes to binary analyses to evaluate the design changes before making deci- data for BFD test plans and the implementation of sions. It is not advisable to automatically apply the same protocols by helmet size will mediate the effect of standard (such as the 90/90 rule or others) when these tests heterogeneity among shot locations. could potentially be across different protective equipment (body armor, helmets, etc.), different numbers of tests (e.g., It was not part of the committee’s charge to offer specific 96 tests for the Enhanced Combat Helmet, 240 tests for the alternative test protocols. However, several alternative plans Advanced Combat Helmet), or over time. and their properties are discussed in this report to assist in DOT&E’s efforts to develop an appropriate plan. • The current BFD protocols use upper tolerance limits DOT&E has indicated that as data are obtained its proto- based on the assumption that the data are normally col will be updated and modified. The committee’s findings distributed. One has to be cautious in using protocols are in that spirit: Available data indicate that penetrations are that are sensitive to such parametric assumptions. rare events (penetration probability of 0.005 or less). There- Further, the use of pretests to check on assumptions fore, an alternative protocol has to be developed such that of homogeneity, as has been proposed by DOT&E, ACH manufacturers have an incentive to maintain that level would lead to complexity in the analysis and, more of penetration-resistance. The 17-out-of-240 FAT protocol importantly, the properties of the BFD protocols. does not provide such incentive. When the test sample size is large (as is the case with The report compares the performance of DOT&E’s DOT&E’s proposed plan of 240 shots), it is prefer- 17-out-of-240 with the Army’s legacy plan of 0-out-of-20 able to use protocols that do not rely on parametric at various places. The main reason for such comparisons, assumptions, are more transparent, and are easier to as discussed earlier, is that any new plan should lead to the interpret. production of helmets that are at least as penetration-resistant
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6 REVIEW OF DEPARTMENT OF DEFENSE TEST PROTOCOLS FOR COMBAT HELMETS as currently fielded helmets. However, the committee reiter- • Brain injury tolerances determined in the past, and ates that there are important advantages to the increased test continuing to be developed for vehicle and sports size in DOT&E’s plan compared to the Army’s legacy plan. collisions, are based on stresses and stress rates that Any modification to DOT&E’s plan should retain the benefits are significantly different from those for ballistic and obtained from the increased test size, although the report blast stresses. does not make any specific recommendation on test size. Most of the findings are recommendations in Chapters 3 and 10 are in response to the third point in the commit- ORGANIZATION OF THE REPORT tee’s statement of task: Evaluate the adequacy of current This report includes 10 chapters and several appendixes. testing to determine the level of protection provided by Chapter 1 provides an introduction and overview. Chapter 2 the ACH. describes the history and evolution of the combat helmet as Chapters 4-9 deal primarily with statistical issues. Chap- well as recent advances in design, materials, and manufac- ter 4 describes the testing and measurement processes for turing processes. combat helmets, including the test threats and the different Chapter 3 describes historical wounding patterns and sources of variation. The Phase II report on body armor test- recent and emerging threats as well as the biomechanical ing noted the need to conduct a formal gauge repeatability basis for penetration and blunt trauma. The latter topic is and reproducibility (R&R) study to determine the sources taken up in more detail in Chapter 10, which presents the of variation in the test process (NRC, 2012). It appears that gaps in medical knowledge of brain injury tolerances relative such a study has not been done. In view of the costs involved to current standards of helmet protection. The key findings in testing and the benefits to be gained from an R&R study, and recommendations from these two chapters include the the committee reiterates the importance of carrying out such following: a study. • Wounding from an explosive source (including Recommendation 4-1. The Department of Defense should fragmentation from bombs, mines, and artillery) conduct a formal gauge repeatability and reproducibility has dominated injuries in all major modern conflicts study to determine the magnitudes of the sources of test since World War II. Blast and blunt trauma are variation, particularly the relative contributions of the vari- increasingly becoming a major source of injuries. ous sources from the testing methodology versus the varia- tion inherent in the helmets. The Army and the Office of the Recommendation 3-1. The Department of Defense should Director, Operational Test and Evaluation, should use the ensure that appropriate threats, in particular fragmentation results of the gauge repeatability and reproducibility study to threats, from current and emerging threat profiles are used make informed decisions about whether and how to improve in testing. the testing process. Recommendation 3-3. The Department of Defense should Chapter 5 provides a formal definition of the performance reassess helmet requirements for current and potential measures—resistance to penetration (RTP) and backface future fragmentation threats, especially for fragments ener- deformation (BFD)—and discusses their limitations. The gized by blast and for ballistic threats. The reassessment results from analyses of FAT and LAT data made available should examine redundancy among design threats, such as to the committee are also described here. These data showed the 2-grain versus the 4-grain and the 16-grain versus the considerable heterogeneity among helmet sizes and shot 17-grain. Elimination of tests found to be redundant may locations. allow resources to be directed at a wider diversity of realistic Chapters 6 and 7 are concerned with the evaluation and ballistic threats, including larger mass artillery fragments, comparison of FAT protocols for RTP and BFD, respectively. bullets other than the 9-mm, and improvised explosive device Most of the key findings and recommendations from these fragments. This effort should also examine the effects of chapters are summarized above. shape, mass, and other parameters of current fragmentation Chapter 8 deals with LAT, with major findings and recom- threats and differentiate these from important characteristics mendations that mirror those for FAT. In addition, Chapter 8 of design ballistic threats. describes how the current LAT protocols can be modified to conform to American National Standards Institute standard. • Unlike body armor, there is not any indirect biome- Chapter 9 responds to the committee’s charge to evaluate chanical connection between the backface deforma- the scope of current characterization testing and recommend tion assessment in the current test methodology and additional studies. A number of additional characterization brain injuries from behind-helmet deformation. studies for new helmet designs as part of a broader program on characterization are suggested.
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SUMMARY 7 CONCLUDING REMARKS nology capability and the needs of the soldier on the battlefield. Further, it is important that the design of The committee commends the Director of Operational test plans focus on that region of the OC curve at Test and Evaluation and his office for their efforts to bring which the helmet is expected to perform. scientific rigor to the testing of combat helmets. These efforts are of critical importance to the safety and morale of the men Throughout the course of the committee’s research and and women of the U.S. armed services. The committee also deliberations, it became quite clear that DOT&E’s and the applauds Rep. Slaughter for her active oversight in this area. Army’s goal is to ensure that combat helmets (and all per- The overarching messages in this report are: sonal protective equipment) are manufactured and tested to the highest possible standards. It is the committee’s hope • There is an urgent need for the Department of that this report helps DOT&E and DoD in their continued Defense to establish a research program to develop pursuit of this goal. helmet test metrics that have a clear scientific link to the modes of human injury from ballistic impact, blast, and blunt trauma. REFERENCES • It is critical that test profiles for combat helmets be DoD IG (Department of Defense Inspector General). 2009. D-2009-047. modified to include appropriate threats from current DoD Testing Requirements for Body Armor. Washington, D.C.: Depart- and emerging threats. ment of Defense. • The development of test protocols must be based on Gilmore, J.M. 2012. Letter from J. Michael Gilmore, Director, Operational Test and Evaluation, to Representative Louise M. Slaughter, July 13. appropriately derived OC curves, where such curves NRC (National Research Council). 2012. Phase III Report on Review of the will likely be unique to each helmet type and design, Testing of Body Armor Materials for Use by the U.S. Army. Washington, which is intentionally chosen to match current tech- D.C.: The National Academies Press. Slaughter, L.M. 2012. Letter from Representative Louise M. Slaughter to Secretary of Defense Leon Panetta, June 26, 2012.