Application of Endfire Arrays at Contemporary Glide-Slope Problem Sites

The application of the endfire-type, compatible instrument landing system (ILS) glide slope is discussed in the context of providing increased capability to install facilities without requirements for extensive terrain modification. Costs of preparing a site for glide-slope operation can be reduced many times by eliminating the requirement for the usual image-forming ground plane. An example is given where the first endfire glide slope has been installed at an airdrome on a mesa giving a high quality path in space in spite of the limited real estate. Recent flight data from this glide slope are presented.     

ILS-past and present

Insight is provided into the evolution of VHF/UHF instrument landing system (ILS) equipment and the role of the US Civil Aeronautics and Federal Aviation Administrations in its development. The discussion covers the ILS localizer, glide slope (image arrays and nonimage arrays), marker beacon, reliability, and avionics     

ILS-a safe bet for your future landings

An argument is presented in favor of the ILS (instrument landing system), the principal components of which are the localizer, which provides lateral guidance to the pilot, and the glide slope, which gives the vertical guidance. A pilot flying these signals precisely will end up over the hard surface runway with the ILS receiving antenna, wherever it is mounted on the aircraft, being about 20 ft above the touchdown point. The safety record and evolution of the ILS are examined, and a pilot's view of ILS (that of the author, an engineer who has worked with ILS since 1957 and a pilot who has used ILS safely for over 30 years) is given. System availability is discussed, and comments concerning future use are offered     

Design of an image radiation monitor for ILS glide slope

The design of a monitor that measures changes in ground reflected image radiation is presented. This monitor is shown to be theoretically capable of determining the effects of snow cover and standing water in the vicinity of an Instrument Landing System (ILS) image-type glide slope, thereby reducing the number and length of outages. A discussion of errors and calibration are presented, along with an example of a practical design     

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。     

RF航段衔接ILS进近程序的最大下降角设计方法

RNP 程序的RF 航段与传统ILS 精密进近程序相结合能充分利用两类程序的优势,但两种程序的过渡阶段需要考虑最大下降角度的设计。本文分析过渡阶段程序的平面与剖面几何设计参数限制条件,以及从星基导航方式转为陆基无线电导航方式需要稳定截获航向信号与下滑台信号的运行限制条件;结合两种限制条件,设计一种可以从不同最后进近定位点（FAP）高度计算下滑道的偏离量与到最后航向截获点（FACF）的弧距离关系进行判断,从而确定最大下降角度的方法,并进行仿真验证。结果表明：该方法可以在不同过渡航渡长度与不同最后进近下降角度的限制下,根据给定最高程序假设温度计算得到符合两种限制条件的最大下降角,为RNP 程序与ILS 程序衔接过渡的下降剖面设计提供了一种基于理论基础且具有可行性的设计方法。     

GTD Terrain Reflection Model Applied to ILS Glide Scope

The capability of calculating the reflection of electromagnetic signals from uneven terrain has many applications. One of these is the determination of instrument landing system (ILS) glide slope performance. For this application the wavelength is approximately 1 m, incidence angles are usually near grazing, and the fields are horizontally polarized, so that gross irregularities such as dropoffs and hills are more important than surface roughness. Past approaches used to calculate the ground reflections for this application have been three-dimensional physical optics models which were very cumbersome and time consuming and which neglected important diffraction and shadowing phenomenon; a two-dimensional physical optics model which was faster than the three-dimensional models but ignored many shadowing and transverse terrain variation effects; and a half-plane diffraction model which is applicable only to a specified type of terrain geometry. In this paper a terrain reflection model based on the geometrical theory of diffraction (GTD) is described which can accommodate any piecewise linear terrain profile, requires less computer time than the physical optics models, is capable of including transverse terrain effects, and determines the reflected fields with all important diffraction and blockage effects included.     

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     

Vertical Path Guidance Computer

A low-cost airborne computer which provides a multiangular glide path for the landing problem is independent of ILS or GCA methods. A barometric altitude signal is divided by slant-range information from a DME interrogator. The resulting ground-based angle is subtracted from the selected approach angle to provide the displayed departure from the glide path. Angular and lineal outputs are available. DME station position may be electrically offset to serve all airdrome runways. Theoretical and experimental results are presented     

Calculating the Effect of Uneven Terrain on Glide Path Signals

A method for calculating the bends in the glide slope due to uneven terrain is presented. A computer program written for the purpose enables the calculation of the difference in depth of modulation (DDM) at any point, taking into account the effect of uneven terrain. Results are presented for a hypothetical case of a hill in front of the runway. The program enables us to predict the glide slope bends due to irregular terrain, so that proper selection of glide slope antenna location can be made.     

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.     

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     

Evaluation of image-type glide slope performance in the presence ofsnow cover

A formulation for the effects that the ground-reflected signal has on the far-field performance of image-type glide slope is developed using geometrical optics. The effects of snow cover are then related to the formulation and analyzed. Results indicate that it is possible for certain types of dry snow to cause glide slope system performance to exceed U.S. Flight Inspection Manual (USFIM) tolerances at depths below existing Federal Aviation Administration (FAA) plowing criteria     

F/A-18E/F全自动着舰飞行特性分析

以F/A-18E/F舰载机为对象,针对航迹精确控制和安全性要求,分析了舰载机全自动着舰飞行特性。首先,基于自动着舰控制系统,建立了全自动着舰飞行控制系统的动力学模型;然后,对下滑轨迹纠偏与控制能力、控制器指令响应特性、变换下滑道机动特性进行了仿真分析。仿真结果表明,在全自动着舰安全边界范围内,舰载机能在较短时间内将航迹控制在理想下滑线附近;控制器具有良好的高度变化率、俯仰角、俯仰角速度等状态指令响应特性及控制面指令响应特性;F/A-18E/F变换下滑道机动则需要配合油门完成,说明仅通过平尾控制实现该机动并非安全着舰的必要条件。     

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。     

仪表着陆系统下滑信标台的场地保护——兼论《国家标准GB6364-86》的严密性

做好航空导航台站的电磁环境保护,是确保导航设备正常运行的一个重要手段,本文以仪表着陆系统的下滑信标台为例,论述了辐射信号的反射区、保护区场地平整及要求等。     

ILS精密进近程序设计中对障碍物的自动处理和评价

本文主要阐述了在 ILS 精密进近程序设计过程中,利用微机自动处理和评价障碍物的一些问题,介绍了计算机程序设计框图及应用实例。     

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.     

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。     

Computed Performance of Glide Slope Arrays on Sites with Limited Ground Plane

The computed performance of four different types of glide slope transmitting arrays sited over idealized ground planes consisting of one-dimensional perfectly conducting strips of various lengths in free space is presented. The idealized ground plane approximates the practical case of a site consisting of an expanse of relatively flat ground plane ending in a precipitous dropoff or in rough diffusely reflecting terrain. The computed results show several phenomena which have repeatedly been observed.