Comments on “Effect of wet snow an the null-reference ILSsystem”

The subject paper (July 1993) has raised some issues regarding the probability of the Instrument Landing System (ILS) radiating out-of-tolerance vertical guidance signals. An independent study has substantiated the findings of that paper and adds further concern regarding some FAA ILS snow procedures. The principal conclusions of this paper are: 1) an analysis, based on Walton's discovery of rare snow conditions that cause the null-reference ILS antenna image to disappear, indicates that these conditions can cause out-of-tolerance guidance signals, 2) operation without a monitor of the image radiation can result in signal-in-space guidance signal errors that are significantly beyond the intended limit values, and 3) the integrity of image glide path equipment in snow environments does not satisfy the ILS integrity requirements     

Improvement of Automatic Landing Through the Use of a Space Diversity ILS Receiving System

A space diversity method of receiving and processing ILS localizer information has been developed and flight tested. Multiple lateral ly separated antennas are used which sense the ILS signal on and around the approach path. Combining these signals suppresses ILS beam distortion produced by multipath signal interference and provides much improved guidance information to the landing aircraft control system.     

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     

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.     

Synthetic vision for enhancing poor visibility flight operations

Visibility is important for the pilot controlling an aircraft in flight conditions close to the ground, particularly when landing. Therefore, poor visibility yields a great restriction for aircraft operations. Restrictions exist for landing sites which are equipped with facilities providing a landing approach aid like ILS since a minimum is required for visibility. For landing sites providing no approach aids, restrictions are much more severe. This holds even if aircraft are equipped with modern instrumentation and navigation devices. The natural view of the pilot is dependent on various meteorological conditions like darkness, dust, fog, rain etc. The degradation in view caused by these conditions can be compensated for partially or even completely by technical means providing artificial vision cues. Such technical means may be based on radar or optical sensor information. Concepts which employ these techniques are known as “Synthetic Visual Systems” or “Enhanced Visual Systems,” . The present paper is concerned with computer generated vision as a further technique providing visual cues for the pilot. Computer generated vision may be used in combination with the aforementioned sensor based techniques. Thus, it is possible to compensate for limitations which sensor based visual systems have in providing sufficient visibility range or in generating a normal looking image. In addition, computer generated imagery has the potential providing additional information to the pilot for controlling the flight path or for warning purposes. This potential can yield improved and/or more information as compared with the natural view when looking out of the cockpit window     

Autonomous Landing Guidance Systems

All weather tactical aircraft recovery and high sortie generation rates from forward, possibly battle damaged landing areas will reqire autonomous landing guidance systems which are independent of ground-based cooperative aids. A recently completed study has examined the operational requirements and assessed current and near term technology for an answer to this need. The Landing Systems Requirements/Synthesis Study has defined the Pilot/vehicle Interface and imaging sensor suite required, based on the concept of augmenting pilot forward vision with sensor imagery and guidance symbology on a HUD during low visibility landings. Image processing technology was also assessed for potential enhancement of the information presented to the pilot. This paper summarizes the final report of the Study, which is in publication.     

转子倾斜对交错式迷宫密封动静特性的影响

建立了交错式迷宫密封数值分析模型,并通过基于微元理论的密封动力特性系数理论识别方法研究了转子倾斜对密封动静特性的影响。结果表明：转子倾斜可降低交错式迷宫密封泄漏量,倾斜角为0.6°时泄漏量降低约2.5%,且进出口压比越大,效果越显著;转子倾斜带来的交错式密封腔室几何形状与齿径向间隙变化使得腔室在周向存在压力分布不均,且随倾斜角增加而增大;密封各腔室对系统稳定性影响规律不同,与交错式迷宫密封腔室的几何特性有关,密封腔室进口靠近转子、出口远离转子的腔室局部出现逆转动方向的速度场,能提高密封系统稳定性,而密封腔室进口远离转子、出口靠近转子的腔室则降低系统稳定性;整个密封段的有效阻尼随倾斜角增大而增大,转子在密封段中心倾斜不会降低交错式迷宫系统的稳定性。     

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     

A Geometrical Model for Glide Path Measurement and Site Evaluation

A geometrical model has been developed to permit accurate and detailed characterization of the instrument landing system (ILS) null reference glide path. The model utilizes a simplified CW measuring system operating at a frequency of 9.375 GHz, which corresponds to a wavelength scaling factor of approximately 30:1. An overall accuracy of 0.01° has been demonstrated for the model facility with an "ideal" ground surface, and satisfactory agreement has been obtained between model and flight test measurements for an existing nonflat glide path site. Geometrical modelling has potential advantages over other approaches in accuracy, economy, measuring convenience, and ability to assess proposed terrain modifications.     

A localizer design to improve missed approach guidance

A novel VHF localizer system has been designed, built and successfully tested to provide increased reliability and safety of commercial and general aviation air transportation. Additional benefits are more precise tracks for aircraft executing a missed approach, reduced volume of the airspace needed for missed approaches, and reduced sizes of areas affected by noise. The design uses contemporary instrument landing system (ILS) hardware to provide dual independent front and back course directional localizer operation with two carriers in the receiver passband offset 4 kHz from the nominal carrier frequency. An example is given of an application and solution to an ILS problem at Reno, NV. Relevant data are presented     

Hybridizing contemporary glide slopes to provide vertical guidancefor GPS approaches

Vertical guidance for an instrument approach to landing during conditions of reduced visibility is a crucial element with respect to safety of flight. It is noteworthy that this vertical component-to be most useful and safe-must desirably provide the pilot with no more than several feet of uncertainty. Unfortunately, with GPS the vertical portion of the position information supplied the pilot by GPS signals is the least precise because of geometries involved. Augmentation for enhancement of accuracy is quite important and the assertion is that it is necessary for totally safe vertical guidance. Evidence from approximately 60 years of experience with electronic landing systems serving the public is that there has been no aircraft accident due to a defective vertical guidance signal. Visibilities as low as 600 feet horizontally can exist at certain airports and landings can still be accomplished. These landings, while not common, are being accomplished flawlessly by contemporary aircraft and equipment. Many aspects of the contemporary UHF glide slope have been studied during its half-century of use. This paper reports on advances, some of them quite recent, that make it realistic to claim that a glide slope can be sited for Category I operation at any runway that meets the physical requirements for this type of operation. For the UHF glide slope, siting imperfections are accommodated by using one of five available types of contemporary glide slope systems or derivatives thereof. This paper reviews how accommodations are achieved in practical cases. Results from earlier tests are identified which show hybridizing of UHF glide slopes and GPS can be used to provide good approach guidance to aircraft making fully automatic approaches to touchdown     

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。     

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     

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。     

Applications of slotted cable antennas in the instrument landingsystem

The use of slotted waveguides in the instrument landing system (ILS) is discussed, and applications of slotted cable antennas to the ILS localizer and glide slope are described. Examples are given of both existing and prospective designs intended to provide solutions for specific siting problems. Important applications are to the end-fire glide slope and category-III localizers     

ILS下滑道结构改善思路及措施

通过对ILS下滑道形成的理论分析，阐述了各种因素对下滑道结构的影响．提出了改善下滑道结构的思路和方法，在近几年广汉机场ILS飞行校验中得到了验证．下滑道结构有了明显的改善。     

自由贸易试验区设立对试点城市高端服务业集聚的影响

使用我国2009-2017年286个地级市数据和双重差分模型,将设立自由贸易试验区视作一项准自然实验,评估其对试点城市高端服务业集聚的政策影响.结果显示:(1)自由贸易试验区的设立对高端服务业专业化集聚存在显著的正向影响,但对多样化集聚的作用并不明显;(2)自由贸易试验区的设立对高端服务业专业化集聚的促进作用,在短期内...     

军用飞机推行综合保障工程的研究

阐述了ILS的涵义及ILS在军用飞机形成战斗力中的重要作用,结合军用飞机实施ILS的现状,对大力推行军用飞机ILS的实施提出了几点建议。     

Image quality issues for an enhanced vision head up display

A part task simulation study was performed to determine the ability of pilots to land an aircraft using head up display (HUD) guidance symbology overlaying an emulated millimeter wave imagery. The task was to land in Category IIIa weather at a Category I facility. Three image parameters were varied: image update rate, image processing latency, and the luminance contrast ratio of the runway image to the background noise. ILS beam bending that was representative of a Category I facility was randomly varied across the experimental runs. Nine pilots completed the test matrix. The only variable that made a significant difference was the runway to background contrast ratio     

用于越肩发射的方位校正导引

当越肩发射攻击后方目标时 ,如果载机不能提供有关目标的完全信息 ,用普通的导引方法完成“越肩”火控过程是不可能的。针对这一问题 ,提出了非完全目标信息方位校正导引方案 ,它不依赖于载机的前视或后视雷达 ,只利用载机上的雷达传感系统提供的有限的目标方位信息 ,让导弹在攻击平面内载机测量到的目标方位线上搜索目标 ,实现越肩发射中的“越肩”。仿真结果表明 ,该方案是一种可行的导引方案