The problem with aviation COTS

Commercial Off the Shelf (COTS) has become a byword for acquisition reform, but there are significant risks associated with the use of COTS products in military systems. These risks are especially acute for aviation systems. This paper explains how COTS can negatively affect military acquisitions and gives ideas on how to plan and resolve COTS caused problems     

Fly-by-wire T & E challenge [aircraft test pilot handling compensation]

Systems developers and testers have always assumed that human compensation is measurable, or, at least, that a cognizant and trained tester is able to identify and detect compensation. More than one study conducted at the Wright-Patterson large amplitude multi-mode aerospace research simulator (LAMARS) facility indicates that this is not necessarily true. Test pilots were able to compensate sufficiently to fly and meet defined performance standards on intentionally crippled aircraft flight control designs. These flight control systems were designed to trigger pilot-induced oscillations, but, in most cases, test pilots could compensate sufficiently to prevent pilot-induced oscillations and to control the simulated aircraft. Anecdotally, this points to a colossal deficiency in the test of highly augmented aircraft systems that has been borne out by multiple aircraft accidents in actual aircraft designs: natural pilot compensation is sufficient to allow faulty designs to reach production and operational service while hiding critical handling qualities cliffs that can lead to loss of an aircraft. This observation, if applied across the gamut of human factors experimentation, has vast ramifications for test and evaluation and development of all human interface systems.     

A parallel computer architecture for continuous simulation

A parallel computer specifically designed for the solution of ordinary differential equations is described. The first version of the machine contains thirty-two processors, running in an asynchronous multiple-instruction/multiple-data mode, communicating with high-speed parallel busses. Synchronization is accomplished by a microprogrammable communication controller. A number of processors have been designed and built for the machine. The processor types offer a wide variation in solution speed and accuracy. To permit easy comparisons with analog and hybrid systems, performance is measured by finding the highest frequency sine wave which can be integrated in real time with an accuracy of 0.1% or higher. Using this performance measure the performance limit of the current machine is 2000 Hz. The structure is capable of solving systems described by differential equations up to order sixty-four at these performance limits     

重返巴厘岛

从吉隆坡一路飞来的国际航班终于在黄昏时分降落在了登巴萨（Denpasar）国际机场。在海关闸口前，从几个不同航班上下来的游客．迅速汇成了几条长龙。四年前那种门可罗雀的冷清场面恍如梦境，眼前这一切才是巴厘岛理所当然的热闹场景。在落日的余晖中走出机场．空气中依然弥散着一股特别的丁香烟气味——记忆中．只有巴厘岛才有的专属气息。     

The case for like-sensor predetection fusion

There has been a great deal of theoretical study into decentralized detection networks composed of similar (often identical), independent sensors, and this has produced a number of satisfying theoretical results. At this point it is perhaps worth asking whether or not there is a great deal of point to such study-certainly two sensors can provide twice the illumination of one, but what does this really translate to in terms of performance? We take as our metric the ground area covered with a specified Neyman-Pearson detection performance. To be fair, the comparison will be of a multisensor network to a single-sensor system where both have the same aggregate transmitter power. The situations examined are by no means exhaustive but are, we believe, representative. Is there a case? The answer, as might be expected, is “sometimes.” When the statistical situation is well behaved there is very little benefit to a fused system; however, when the environment is hostile the gains can be significant. We see, depending on the situation, gains from colocation, gains from separation, optimal gains from operation at a “fusion range,” and sometimes no gains at all     

Range and Bearing Estimation in Passive Sonar

Passive sonar systems are used for estimating the range and bearing of signal sources, such as ships or submarines. In this study, the Cramer-Rao bounds on estimation errors are used as measures of the accuracy of the estimates. The bounds show how parameters such as observation time, signal bandwidth, signal-to-noise ratio, and array geometry can be chosen to obtain maximum accuracy. When the array geometry satisfies certain conditions, the bound for range estimate is shown to be independent of the actual source bearing and the bound for bearing estimate independent of both the range and bearing of the source. It is also shown that the same conditions on array geometry ensure that the range or bearing estimation accuracy is not degraded when tne other pammeter is not known.     

Predetection fusion: resolution cell grid effects

If members of a suite of sensors from which fusion is to be carried out are not colocated, it is unreasonable to assume that they share a common resolution cell grid; this is generally ignored in the data fusion community. We explore the effects of such “noncoincidence”, and we find that what at first seems to be a problem can in fact be exploited. The idea is that a target is known to be confined to an intersection of overlapping resolution cells, and this overlap is generally small. We examine noncoincidence from two viewpoints: tracking and detection. With respect to tracking our analysis is first static, by which is meant that we establish the decrease in measurement error; and then dynamic, meaning that the overall effect in the tracking problem is quantified. The detection viewpoint considers noncoincidence as it has impact on a predetection fusion system. Specifically, the role of the fusion rule is examined, and the use of noncoincidence to improve detection performance (rather than that of tracking) is explored