Statistics, Testing, and Defense Acquisition New Approaches and Methodological Improvements (1998) / Chapter Skim
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Appendix A Case Studies and System Descriptions
Appendix A Case Studies and System Descriptions
Pages 165-190
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From page 167... ...
LONGBOW APACHE HELICOPTER The Longbow Apache (AH-64D) is a modified version of the Army's existing attack helicopter, the Apache (AH-64A)
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From page 168... ...
Because the Longbow is an ACAT I Programs its operational testing and evaluation is subject to oversight by DOT&E, in the Department of Defense. Operational testing of the Longbow comprised a series of gunnery tests with live ammunition at the Naval Air Warfare Center (in China Lake, California)
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From page 169... ...
Firings occurred under three distinct conditions: day mission with smoke obscuration, night mission with clear visibility, and night mission with smoke obscuration. The test and evaluation plan listed the required number of missile shots in each of the three scenarios as 12, 8, and 4, respectively, for the Longbow team and 5, 3, and 3, respectively, for the Apache baseline team.
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From page 170... ...
The primary data sources for measuring the reliability, availability, and maintainability performance of the Longbow system were the gunnery and force-onforce tests conducted as part of the initial operational test and evaluation plan. Secondary data sources included development testing, logistical demonstrations, and force development test and experimentation.
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From page 171... ...
, and MTBEMA denotes the mean time between essential maintenance actions. The sample values of these constituent parts observed during the initial operational testing and evaluation are described in the Longbow Apache operational evaluation report.
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From page 172... ...
An operational readiness assessment was mandated by Congress to determine whether the B-1B can achieve and sustain a desired readiness rate of 75 percent over a 6month period. In the 2 years preceding the assessment, mission capable rates in the B- 1 fleet averaged approximately 57 percent, primarily because of inadequate funding for repair of parts through interim contractor support and for stocking of repairable and new spare parts.
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From page 173... ...
The five availability measures were the mission capable rate; the total not mission capable rate; two submeasures intended to isolate maintenance and supply problems; and the utilization rate, expressed as the average number of hours flown per aircraft per month. With improved reliability, availability, and maintainability support, the 28th Bomb Wing achieved a readiness rate of 75 percent by the start of the operational readiness assessment and demonstrated a cumulative readiness rate of 84.3 percent during the 6-month evaluation period.
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From page 174... ...
THE ATACMS/BAT SYSTEM In the Army Tactical Missile System/Brilliant Anti-Tank (ATACMS/BAT) System, the Army Operational Test and Evaluation Command proposes to use a relatively novel test design in which a simulation model, when calibrated by a small number of operational field tests, will provide an overall assessment of the effectiveness of the system under test.
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From page 175... ...
Possible countermeasures must also be considered: for example, the tanks may disperse at some point, instead of advancing in a straight-line formation or may try to use decoys or smoke obscuration. The operational test design, or shot matrix, in the Test and Evaluation Master Plan lists eight test events that vary according to such factors as range of engagement, target location error, logic of targeting software, type of tank formation, aimpoint, time of day, tank speed and spacing, and threat environment; see Table
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From page 176... ...
Assuming that the aimpoint factors are inactive, a complete factorial experiment for the ATACMS/BAT system would require 23 x 32 = 72 design points. However, fractional factorial designs with two- and three-level factors could provide much information while using substantially fewer replications than a complete factorial design.
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From page 177... ...
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From page 178... ...
However, there is no requirement that the test provide statistical confidence for assertions about the performance of the system at the threat- or scenario-level. During test planning of the CMWS, it was initially assumed that the key factors related to warning time were altitude of the aircraft, horizontal distance (range)
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From page 179... ...
Additional information indicated that missile warning time was likely to be linearly related to altitude, and at most quadratically related to range and aspect angle. Therefore, missile warning time was measured at two different altitudes (low and high)
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From page 180... ...
SOURCE: "Common Missile Warning System Sample Size Strategy," 2-1196 presentation, Air Force Operational Test and Evaluation Center design of 5 shots per scenario and threat combination. (Assuming an extremely successful performance by the CMWS, this design would have had marginally acceptable power with respect to the assumption that the CMWS did not meet its required level of performance.)
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From page 181... ...
Finally, these models could be used to provide predictions and associated confidence intervals for additional scenarios that were within the test domain for each threat. Test Sample Size Argument The remaining question was whether one missile shot per scenario - threat combination would be sufficient to produce an estimate of average missile warning time across scenarios and threats that would pass a significance test at typical levels with high probability, thereby supporting that the CMWS satisfied its required level of performance.
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From page 182... ...
Therefore, this approach has the advantage of being a quantifiable answer to an important and related question. Note that although there is no user requirement for estimates of average warning time at the threat level at typical levels of statistical confidence, this test design can produce estimates with reasonable levels of statistical confidence at that level.
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From page 183... ...
An open question is whether the test size could be reduced by making use of preliminary versions of the regression models that will be developed, since these models will produce estimated average warning times that, with some reasonable assumptions, will have lower variances than one could get through direct measurement for an individual threat. Or, one could instead maintain the variance of the estimated average warning time while reducing the number of required test shots, through use of a design that would have permitted estimation of the four regression models.
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From page 184... ...
It was designed to perform reconnaissance, target acquisition, artillery fire adjustment, and target designation for laser-guided munitions such as Copperhead artillery rounds and HELLFIRE missiles. The concept of operations was for the RPV to penetrate enemy territory 20 to 30 kilometers, where it might be acquired and engaged, or countered, by enemy systems such as air defense units or enemy radio-frequency Jammers.
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From page 185... ...
Its design is intended to allow delivery of outsize combat cargo and equipment directly into austere airfields. The C-17 will deliver passengers and cargo over intercontinental distances, provide theater and strategic airlift in both airland and airdrop modes, and augment aeromedical evacuation and special operations .
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From page 186... ...
are 2.5-ton payload capacity models consisting of cargo, air drop cargo, and van variants. The medium tactical vehicles (MTV)
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From page 187... ...
M1 Abrams Tank Bernard Kempinski, Institute for Defense Analyses M1, MlA1 and M1A2 are versions of the Army's Abrams main battle tank. The Abrams is [a]
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From page 188... ...
The projectile' s sensor detects a vehicle' s infrared signature, and an explosively formed penetrator fires at the heat source. Sergeant York Elliot Parkin, Institute for Defense Analyses The Sergeant York, a radar controlled twin 40 mm air defense gun for defense of armored forces, was evaluated by the Army during an April 1985 operational test at Fort Hunter Liggett, California.
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From page 189... ...
, Bradley Fighting Vehicle, and Cobra Attack Helicopters. Through continuous modification it has been kept up to date against current threat main battle tanks.
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From page 190... ...
The Black Hawk is the primary helicopter for air assault, general support, and aeromedical evacuation units. In addition, modified Black Hawks operate as command and control, electronic warfare, and special operations platforms.
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