Flight safety performance of the microwave landing system

The microwave landing system (MLS), which is scheduled to be implemented progressively over the next 10 years, is intended to supply the instrument landing system (ILS) as the international standard landing aid. MLS has been demonstrated to be superior to ILS from both performance and reliability standpoints, yet considerable debate persists on its relative merits. Although tolerance criteria for flight safety are embedded in these comparisons, flight safety has not been a major component of these discussions. The reasons why flight safety has not been an issue are addressed, and observations on the flight safety of MLS are related from a systems point of view. The effect of MLS on airport capacity is identified as a central issue. Observations are derived from a review of available documentation and operational results to date as well as discussions with the participants     

飞机着陆系统的现状与发展

论述了仪表着陆系统(ILS)、微波着陆系统(MLS)的作用及应用前景和主要优缺点。提出在未来MLS系统逐步取代ILS系统的过程中,ILS／MLS组合着陆系统导航设备的应用与发展。     

Microwave Landing System

The National Microwave Landing Systems (MLS) program is a joint DOT/DOD/NASA effort to implement a common civil/military precision landing system to replace the current Instrument Landing System (ILS). The MLS will be capable of providing precision landing guidance down to Category III minimum while allowing for complex approach paths in both the horizontal and vertical planes. The system is based on the Time Reference Scanning Beam (TRSB) technique which was selected by the International Civil Aviation Organization (ICAO) in April 1978 as the new international landing system standard. MLS is less susceptible to interference from the surrounding area and provides a greater signal coverage area than ILS.     

MLS: a total system approach

A typical approach and landing operation is described. The microwave landing system (MLS) is then examined, its design characteristics and how it works are shown, and how the MLS design fulfils the user's operational requirements by protecting the guidance signal from reflected signal interference is highlighted. MLS angle system accuracy is discussed in great detail, and its reliability, integrity, and coverage volume are briefly considered. MLS availability at any runway to all aircraft types and their landing scenarios, which is accomplished using narrow scanning beam antennas, is examined     

Microwave Landing System Area Navigation

The International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPS) states that the Time Reference Scanning Beam (TRSB) Microwave Landing System will supplant the existing Instrument Landing System (ILS) as the recognized international standard as early as 1995. The MLS provides the ability to determine the aircraft's position in three dimensional space over a large coverage volume in the airport terminal area. This affords the capability to navigate and execute approaches throughout this volume of coverage. This technique is known as Microwave Landing System Area Navigation (MLS RNAV). In order to assess and further develop the potential capabilities of MLS RNAV, the FAA Technical Center has undertaken the tasks of performing analytical studies, as well as the development of a prototype MLS RNAV system.     

MLS: keeping pace with the future

It is argued that the instrument landing system (ILS) is now at its operational limit in terms of radio frequency availability, approach flexibility, and technology. The operational requirements for a microwave landing system (MLS), which will overcome key limitations of the ILS and provide growth to meet future requirements of precision landing systems, are discussed, John F. Kennedy (JFK) International Airport and LaGuardia Airport in New York City are discussed as examples to demonstrate the capabilities of MLS     

航空发动机部件特性修正技术研究

针对传统部件特性修正方法未考虑发动机多状态导致修正精度不高的问题,提出了1种基于粒子群优化和滑动最小二乘法的某型发动机部件特性修正方法。该方法利用粒子群优化算法分别求得在发动机不同状态下的修正系数,并以这些系数为基础,采用滑动最小二乘方法拟合修正系数曲面,从系数曲面上获取原有部件特性图上各点对应的修正系数,从而得到修正特性。试验结果表明:该方法克服了传统方法的不足,提高了特性修正精度,为开展单机监控和视情维修提供准确的部件数据基础。     

MLS system error model identification and synthesis

Signal-in-space modeling of approach and landing guidance systems such as the microwave landing system (MLS), which is necessary for aircraft certification, is addressed. A technique which can, in principle, identify the error sources in navigation systems and can also perform the inverse operation of synthesizing an error generator whose output is statistically equivalent to the original error data is described. The technique can also be used to validate equipment error budget assumptions. The identification and synthesis technique applies not only to MLS but to all navigation systems     

民用飞机着陆系统安全性评估的故障树分析

飞机着陆系统是保障飞机安全进近着陆的关键系统,如何评估着陆系统满足安全性设计要求是系统设计的重要环节之一。阐述民用飞机安全性评估的基本流程,以微波着陆系统为例,针对给定的微波着陆系统框图,通过故障树分析方法,对完全丧失两侧微波着陆信息的失效状态进行定量评估,重点详述建树过程和建树方法。结果表明:故障树分析对系统架构的设计具有重要的指导作用,二者紧密结合、相互反馈;特别是当失效状态所对应的概率要求无法满足时,借助故障树分析产生的割集报告,能找出系统架构存在的薄弱之处和关键部位,从而采取有效的应对措施,完成对系统架构的优化设计。     

微波着陆地面设备维护计算机软件系统研究

维护计算机是微波着陆系统（MIS）地面设备的重要附属设备。针对微波着陆系统地面设备维护计算机的具体需求,详细分析了微波着陆系统地面设备维护计算机与相关台站的信息交互关系,介绍了维护计算机软件模块组成、通信协议、实现流程及实现的主要关键技术。该软件已成功运行于某微波着陆系统中。     

Trajectory Estimation with Uncertain and Nonassociated Data

The local behavior of a maximum likelihood estimator that adaptively weights data of uncertain origin to make a probabilistic measurement-to-track assignment is examined. The results are placed in the framework of the classic estimation theory of Fisher and Cramer. The Cramer-Rao bound is derived and the MLS error level is compared with this lower bound and the level achieved with known data association. Deterioration in performance was found to depend solely on the false-detection to valid-contact ratio, and the actual (measured) covariance matrix is a scalar multiple of the covariance matrix computed for associated data.     

Microwave landing system: a pilots point of view

The author describes the MLS installation on runway 19L at Mid-Continent Airport, Wichita, Kansas, which has been operational since mid-1987. He describes the MLS equipment installation in his aircraft, which is one of a number of aircraft in the Wichita area that have been equipped with MLS equipment and routinely utilize the system. He summarizes his operational experience with the system. He reports complete satisfaction and increased versatility as a result of the guidance information provided     

Demonstration of MLS advanced approach techniques

Instrument approach designs and flight-test results using the microwave landing system (MLS) are presented. A general-aviation aircraft was flown on linear computed centerline and curved approach paths with MLS guidance displayed on basic course-deviation indicator and horizontal situation indicator instruments. Approach performance was documented using a ground tracker system, recording three-dimensional position information. These tests demonstrated the flyability of such advanced paths with basic cockpit instrumentation     

飞行管理计算机的ML SRNAV算法及运行结果

为了配合即将使用的微波着陆系统 MLS,飞行管理计算机必须扩增其区域导航 RNAV 的功能。本文采用平面汇交法和角锥汇交法及其组合,针对方位台,仰角台、测距台非共点发射的一般情况,编制了适应多种情况的MLS RNAV 通用软件,并进行了试算。为今后编制飞机上使用的实时运行软件做好准备。     

微波着陆系统（MLS）场地模型

本文讨论建立微波南系统场地模型的基本原则和方法，并进行了计算机仿真，场地模型在微波着陆系统场地设计和运行验证中是很重要的。     

基于成本效益分析的ILS/MLS过渡决策

本文在对民航几个具有代表性的机场和航空公司进行调研基础上，提出了ＩＬＳ／ＭＬＳ成本计算和未来机队预测方法，从我国目前应用ＩＬＳ现状出发，列举了由ＭＬＳ可能获得的效益。根据成本计算结果的比较和分析，提出了我国ＩＬＳ／ＭＬＳ过渡方案参考的结论和建议，供领导机关作决策选择。     

System Considerations for the New DME/P International Standard

The International Civil Aviation Organization (ICAO) has completed technical standards for the precision distance measuring equipment (DME/P). The DME/P is an integral element of the microwave landing system (MLS) and will provide the precision ranging function to complement the already standardized azimuth and elevation guidance functions of the system. In 1978 an ICAO meeting concluded that the DME/P should be integrated into the existing standards for the conventional DME (DME/N) as a compatible service. The motivation for this was economic. It was reasoned that a single L-band airborne unit could satisfy the need for both existing enroute and the new precision approach and landing services, thereby avoiding unnecessary duplication of on-board ranging equipment. Furthermore, this approach would permit existing conventional airborne equipment to obtain service from the new DME/P ground facilities at least during the initial stages of MLS implementation. These compatibility requirements were later incorporated into the DME/P statement of operational requirements which was accepted at an ICAO meeting in April 1981. Further, they have been a primary focus in the DME/P standardization effort which has been actively pursued since late 1980. The conceptual design of the DME/P that evolved from the ICAO process is discussed here. The comptability issues are highlighted, and it is shown how they are accommodated in the system synthesis which also treats the obvious need for a guidance function of high integrity and robust performance in the severe multipath environment encountered in approach and landing operations.     

A high-order SPH method by introducing inverse kernels

The smoothed particle hydrodynamics (SPH) method is usually expected to be an effi-cient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by intro-ducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square (LS) and Moving-Least-Square (MLS) methods. Then detailed analysis in spectral space is presented for people to better under-stand this method. Finally we show three test examples to verify the method behavior.     

基于网格测力数据的多体分离轨迹预测方法研究

将基于风洞网格测力试验数据建立的气动力模型与刚体运动方程进行耦合求解得到多体分离轨迹-时间特性，建立了一种多体分离的离线轨迹预测方法。为了提高气动力模型的预测精度，针对移动最小二乘法（MLS）模型提出一种新的权函数形式，针对Kriging气动力数学模型通过加入样点预处理提出了Kriging-Pre数学模型。研究方法应用于来流马赫数6条件下，某并联两级入轨飞行器标模的分离特性研究。研究表明采用改进的两种气动力数学模型均可有效提高分离轨迹预测精度，得到与CFD以及风洞试验定性一致的结论。验证了本文提出的离线轨迹预测方法可以满足当前多体分离特性定性分析需求，具有较高时效性。     

The case for ILS

In response to the interest and activity in microwave landing systems (MLSs), the capability of instrument landing systems (ILSs) is examined and a case for their continued implementation is made. The changes that have been made with respect to electronic hardware, monitoring, and antenna systems in response to more stringent demands are reviewed. It is argued that there is no technical impediment to the installation of additional and upgraded ILS installations over the 1990s and that these installations would be cost effective and pay back the investments before being displaced by MLS