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     

微波着陆信息处理系统研究

微波着陆信息处理系统是MLS机载设备在研制、生产和维修过程中必不可少的一种专用测试设备,文中论述了研究微波着陆信息处理系统的必要性,并从硬件结构上说明了微波着陆信息处理系统的工作原理。     

舰载机着舰侧向轨迹增量控制

针对舰载机着舰侧向控制难度较大的问题,借鉴美国海军的“魔毯”(MAGIC CARPET)着舰的先进理念,提出了 1种新的着舰控制方法,即侧向轨迹增量控制。首先,分别从理论上分析了侧向常规控制、侧向轨迹增量控制的控制结构和着舰性能;然后,对 HUD显示符号进行改进;最后,通过实时仿真,比较了这 2种方法的着舰控制效果。结果显示,着舰侧向轨迹增量控制具有 3个优点:1)简易,降低了飞行员的操纵频次和负担;2)直观,着舰侧向操纵更直观,侧向杆量与飞机侧偏修正速率成正比例,而且当横杆回中时飞机能自动跟踪跑道中心线的横向漂移;3)鲁棒,显著提高了对侧风和舰尾流的抑制能力,即使在飞行员不操纵的情况下,飞机也能迅速反应和抑制风干扰。因此,建议在着舰工程中采用侧向轨迹增量控制。     

飞机自动进近和自动着陆的分析研究

本文首先概述了当前民航客机的自动导航、进近、着陆的全过程。随着重点分析了波音737飞机利用SP-77自动飞行控制系统与仪表着陆系然的航向信标仪和下滑仪及机载无线电高度表等设备实现向跑道自动进近和自动着陆的工作过程,并系统介绍了在实现上述过程中,SP-77自动飞行控制系统的自动驾驶仪横滚通道和俯仰通道控制逻辑的建立,系统工作电路的转换,系统的控制规律和工作特点。     

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     

Locating forward opportune landing sites using spectral images fromsatellites

The ability of future combat airlifters to deliver cargo into short, austere opportune landing sites which are very close to operating field units is expected to greatly improve the effectiveness of the US warfighter. But how do we find and select those sites in a quickly-changing battle scenario? The use of spectral image data from satellites such as EarthWatch as the medium for identifying opportune landing sites is the concept of interest and is described. A study was performed to explore the feasibility and data requirements for this concept. The study's objectives were two-fold: (1) evaluate and demonstrate airlifter value; and (2) evaluate and demonstrate opportune landing site selection concept feasibility. Spectral data was collected in several image resolutions for selected areas within the US. Potential opportune landing sites were selected across large areas and the selection was refined based on higher resolution spectral images. Site surveys were used to grade the accuracy of selection. The number of opportune landing sites (as short as 600 feet) relative to traditional runway lengths was determined and compared     

起落架有限元梁模型建立及其静力学分析

为了获得起落架载荷传递以及评估几何非线性和静不定对起落架载荷传递的影响,同时探索起落架结构有限元梁模型的建模方法,应用HyperMesh和Ansys联合仿真的方法搭建某型具有局部静不定特征的前起落架、主起落架有限元梁模型;使用此模型进行三种载荷工况的静力学计算,获得考虑静不定和几何非线性的起落架接头和截面载荷,以及在单位载荷作用下起落架的航向、侧向和扭转刚度,并与传统方法计算结果进行对比.结果表明:有限元方法和传统方法获得的接头载荷有差异,部分差异超过了±10％,最大差异达到30％;计算前起落架外筒横梁、斜梁截面内力的传统方法及其简化具有合理性,对起落架支柱设计具有指导意义.     

基于LS-DYNA的气垫式起落系统落震性能仿真

缓冲性能是气垫式起落系统的一个重要功能,基于以某型地效飞行器为背景的气垫式起落系统方案设计,建立了气垫式起落系统落震仿真模型.利用有限元理论和LS-DYNA仿真平台对气垫式起落系统缓冲性能进行仿真分析.结果表明气垫式起落系统在落震过程中未出现反弹,气囊最大压缩位移为1.015 m,小于允许最大压缩位移1.502 m;整个落震过程出现的最大过载为2.87 g,小于允许最大过载3 g.验证了气垫式起落系统在落震过程中缓冲行程及缓冲性能满足要求.     

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     

一种多径条件下的MLS接收机测角误差分析新方法

为了准确分析多径环境条件下微波着陆系统接收机测角误差,在深入分析微波着陆系统(MLS)测角原理的基础上,提出了一种基于扫描波束主瓣等效替代的误差分析方法。该方法通过把往返波束脉冲主瓣用高斯钟形替代,准确计算了接收的扫描脉冲-3dB门限前后沿误差,建立了多路径条件下统一实用的接收脉冲包络波峰位置偏移误差模型和锁住闸门测量误差模型。为验证模型准确性,以特定的多径环境条件为例,计算MLS接收机的测角误差,将计算结果与利用Mathias经典模型的计算结果进行对比,并通过计算机仿真进行验证。结果表明,采用主瓣替代方法能够较好地克服经典模型精确分析误差方面的使用不足和缺陷,且对多径条件下接收机测角精度的准确评定具有一定的实用价值。     

模型直升机自主返回系统的设计与实现

设计了一架具有自主返回模块和增稳模块的模型直升机。该直升机硬件电路以C8051F020单片机作为机载部分控制器,使用MEMS陀螺仪和MEMS~JI速度计测量姿态信息,运用无线收发模块实现和地面站的通信。文章介绍了模型直升机系统的软件流程和实现,用系统辨识法分通道建立了直升机模型,设计了直升机的增稳控制模块。设计的模型直升机可完成悬停、返回、着陆等简单的自主飞行任务,为后续舰载小型模型直升机自主起降开发与验证平台的研制奠定了基础。     

考虑杆臂效应与挠曲变形的全自动着舰技术

联合精确进近和着陆系统（JPALS）舰载组件旨在为最终进近阶段的舰载机提供自动着舰能力。针对由于舰船杆臂效应与挠曲变形的存在导致舰载机着舰定位精度下降的问题,开发了一种基于卫星引导的全自动着舰非线性化参数误差模型,结合舰船甲板运动及舰载机纵向飞行控制模型,评估舰船结构挠曲和姿态不确定性对着舰落点精度的影响。结果表明,杆臂效应与挠曲变形对着舰落点精度有显著影响,利用建立的误差模型以及飞行控制模型,能够将着舰落点精度有效控制在着舰标准之内。     

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     

High accuracy navigation and landing system using GPS/IMU systemintegration

In this paper, the accuracy, integrity and continuity of function requirements for automatic landing systems using satellite navigation systems are discussed. Such a landing system is the integrated navigation and landing system (INLS) developed by Deutsche Aerospace (DASA/Ulm, Germany). The system concepts of the INLS are presented. It is shown how an INLS, based on system integration of a satellite navigation system (e.g., GPS) in realtime differential mode with an inertial measurement unit (IMU) in the accuracy class of an attitude and heading reference system (AHRS), can meet the requirements: the results given are mainly devoted to the accuracy issues. Using Kalman filter techniques, an in-flight calibration of the IMU is performed. The advantage of system integration, especially in dynamic flight conditions and during phases of flight with satellite masking, is explained. The accuracy, integrity and continuity of function of the INLS were proven by means of flight tests in a commuter aircraft using a laser tracker as a reference. These flight tests have shown that the short-term accuracy (<60 seconds) of the AHRS used within the INLS has been improved from low cost sensor quality to the accuracy of a high quality laser inertial navigation system (LNIS). With the presented INLS, a landing at any airfield, not equipped with conventional Instrument Landing System (ILS) or Microwave Landing System (MLS), is possible by using a very cost effective system. The INLS is a high accuracy navigation and landing system designed to be used instead of conventional landing systems at small airfields and to fill operational gaps of conventional navigation and landing systems in cruise and approach on large airports     

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.     

Aerodynamic optimization and mechanism design of flexible variable camber trailing-edge flap

Trailing-edge flap is traditionally used to improve the takeoff and landing aerodynamic performance of aircraft.In order to improve flight efficiency during takeoff,cruise and landing states,the flexible variable camber trailing-edge flap is introduced,capable of changing its shape smoothly from 50% flap chord to the rear of the flap.Using a numerical simulation method for the case of the GA(W)-2 airfoil,the multi-objective optimization of the overlap,gap,deflection angle,and bending angle of the flap under takeoff and landing configurations is studied.The optimization results show that under takeoff configuration,the variable camber trailing-edge flap can increase lift coefficient by about 8% and lift-to-drag ratio by about 7% compared with the traditional flap at a takeoff angle of 8°.Under landing configuration,the flap can improve the lift coefficient at a stall angle of attack about 1.3%.Under cruise state,the flap helps to improve the lift-todrag ratio over a wide range of lift coefficients,and the maximum increment is about 30%.Finally,a corrugated structure–eccentric beam combination bending mechanism is introduced in this paper to bend the flap by rotating the eccentric beam.     

机载前视式低空风切变探测数值模拟研究

使用二维面对称微下击暴流数值模式,对“湿”微下击暴流风切变进行了模拟,并通过工作在Ｘ－波段的微波多普勒雷达,对飞机着陆下滑航迹前方的微下击暴流风切变进行探测。结果表明：通过单元－单元自动增益控制、杂波滤波和天线仰角控制,可提前８０ｓ（６ｋｍ）探测到“湿”微下击暴流风切变,符合ＦＡＡ提出的适航要求     

支柱式前起落架系统刚度与摆振稳定性研究

系统刚度（航向、侧向和扭转刚度）是支柱式前起落架设计的重要指标,探明系统刚度对摆振稳定性的影响规律,对起落架的防摆设计具有重要意义。采用改变缓冲器初始气体压力的方式,分析缓冲器行程对系统刚度的影响规律,研究系统刚度对支柱式前起落架摆振的初始扭转角、收敛时间、收敛比例和稳定区域的影响。结果表明：增大支柱式前起落架系统刚度,可提升防摆性能,但同时会造成初始扭转角和摆振收敛时间的增加,这会降低起落架抵御外界干扰的能力,因此,不能过度增加支柱式前起落架系统刚度。     

Effect of selective laser treatment on initiation of fatigue crack in the main part of an undercarriage drag strut

This paper presents the results of material characterization and a fatigue test conducted for a laser-re-melted drag strut used in an aircraft landing gear. The drag strut was re-melted with a CO_2 laser beam. Eight re-melted paths were made in the form of spiral lines along the axis of the drag strut. Next, the drag strut was subjected to variable loads on a testing machine simulating loads occurring when an aircraft lands. The fatigue test showed that the laser-treated drag strut was able to withstand 1700 simulated cycles of landing. This result was 70% better than that obtained for a drag strut with no laser treatment. In order to find the reason for the increase in the number of cycles of simulated landings, tests were carried out using transmission and scanning electron microscopes, a computer microtomograph, an X-ray diffractometer, and a nanoindenter,respectively. Results of the conducted research indicated that the reasons for the increased fatigue life of the laser-treated undercarriage drag strut were both an ultra-fine cellular martensitic microstructure and compressing residual stresses generated during the laser re-melting of the surface layer of the material.     

GPS autoland considerations

It is pointed out that fully automatic hands-off landing (autoland) capability for commercial aircraft, using the Global Positioning System (GPS), has not been demonstrated, and that ground multipath errors limit vertical positioning accuracy. An evolving integrated-sensor-based architecture for approach and landing, called the tunnel concept, is examined. The precise velocity information available could substantially reduce the vertical accuracy requirement for autoland