Research for Failures

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MC 2M/ATE MOS Study: Final Report
September 1, 1999
This briefing summarizes the findings and conclusions resulting from the CNA Marine Corps Microminiature/Automatic Test Equipment Military Occupational Specialty Code (2M/ATE MOS) study. The purpose of the study was to analyze a number of alternative Circuit Card Assemblies (CCA) repair strategies for MC ground systems. The alternatives considered ranged from evacuating all CCA functions to repairing them all. We also considered varying the repairer workforce composition and repair location. We found that the current repair practices, assuming that the MC assigns the number of repairer man-years we estimate are needed, saves about $75 million a year over what it would cost of evacuate and replenish failed CCAs. More money could be saved if all CCAs were repaired at a central location (Electronic Maintenance Companies). The report also finds that 2M workload does not appear to warrant a primary MOS.
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Modeling Failures of Intermittently Used Machines
July 1, 1987
Many machines are used intermittently, that is, repeatedly turned on and off during normal operation. Eventually the machine fails. This research memorandum presents methodology for analyzing failures of machines that are repeatedly turned on and off. Because a machine can fail both when it is on and off, different parametric models for failure are used for each of these periods. An important issue addressed for such machines is how the intermittent use itself affects failure. Because the models can predict the chance of failure under different usage patterns, less harmful usage patterns can be recommended. As an example, the models are applied to a radar system, and both the immediate and cumulative effects of on-off cycling are demonstrated.
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An Analysis of 4855 Data: Combat System Availability Estimates and the Effect of Usage on Failure
October 1, 1986
Using the Navy's 4855 data, estimates of selected combat systems' availability rates are computed and the effect on reliability of turning the systems on and off is determined by analyzing the system's history of being on, off, and broken. Two models are used that describe the time until failure when a system is in either a 'secure' or an 'up' state.
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The Relationship Between Material Failures and Flight Hours: Statistical Considerations
January 1, 1985
This paper attempts to clarify the relationships among the following four hypotheses: (1) the number of material failures across intervals of calendar time containing equal accumulated flight hours follows a Poisson distribution; (2) the number of elapsed flight hours between successive independent material failures follows an expotential distribution; (3) the expected number of monthly material failures is exactly proportional to monthly flight hours; and (4) the observed number of monthly material failures is strongly correlated with monthly flight hours.
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ESTIMATION OF THE EFFECTS OF A SHIP'S STEAMING ON THE FAILURE RATE OF ITS EQUIPMENT: AN APPLICATION OF ECONOMETRIC ANALYSIS
February 1, 1981
Regression analysis is used to estimate the effects of a ship's steaming on the failure rate of its equipment, holding constant the effects of other factors such as a ship's class, fleet, time since overhaul, and point in the deployment cycle. Equipment failures are measured with data on 14,000 CASREPs for destroyer-type ships in 1970-75. It is widely thought that steaming would increase the number of equipment failures due to wearout. However, this report found that the failure rate of equipment seemed to decrease with steaming in the long run.
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