User:YFdyh000/区域导航

传统导航与RNAV方法的主要区别

区域导航（英語：Area navigation）是一种仪器飞行规则（IFR）导航方法。这种方法允许飞机选择导航信标网络内的任何航线，而不是必须自导航信标飞至另一导航信标。这样可以节省飞行距离、减少拥堵，并允许飞往没有信标的机场。区域导航以前被称为“随机导航（random navigation）”，因此其缩写为RNAV。

RNAV可以被定义为一种导航方法，它准许飞机在以航点为参考的导航信号覆盖范围内、独立系统能力内或两者组合的能力下在任何期望航路上运行。

在美国，RNAV在20世纪60年代得到发展，20世纪70年代公布了第一条这样的航路。1983年1月，由于飞机使用惯性导航系统而非地面信标，因而成本效益分析显示不利于维护RNAV航路系统，美国联邦航空管理局撤销了所有美國本土的RNAV航路。RNAV在大规模引入卫星导航系统后被重新采用。

背景

随着航空业的持续增长，对领空容量的需求也日益增加，因此强调优化利用现有空域。因应用“区域导航”技术能提高运行效率，故而导致了全世界各地区和各个飞行阶段的导航应用发展。这些应用还可能扩展为为地面移动提供导航。

特定航线或特定空域内的导航应用必须以清楚、简洁的方式定义，从而确保机组人员和航空管制員了解机载RNAV系统的能力，确定RNAV系统是否适合特定空域的要求。

RNAV系统的演变方式类似传统的陆上航线和程序。特定RNAV系统通过组合分析和飞行测试来确定和评估其性能。对陆上运行来说，最早的系统使用甚高频全向信标（VOR）和测距仪（DME）来估计位置；海上运行则使用惯性导航系统。领空和空中无障碍标准会跟进现有设备的性能而制定，规范基于目前可用的能力。Such prescriptive requirements resulted in delays to the introduction of new RNAV system capabilities and higher costs for maintaining appropriate certification. To avoid such prescriptive specifications of requirements, an alternative method for defining equipment requirements has been introduced. This enables the specification of performance requirements, independent of available equipment capabilities, and is termed performance-based navigation (PBN). Thus, RNAV is now one of the navigation techniques of PBN; currently the only other is 所需导航性能 (RNP).

RNAV和RNP系统本身很是相似。两者的关键差异是对机载性能监控和警报的要求。A navigation specification that includes a requirement for on-board navigation performance monitoring and alerting is referred to as an RNP specification. One not having such requirements is referred to as an RNAV specification. An area navigation system capable of achieving the performance requirement of an RNP specification is referred to as an RNP system.

As a result of decisions made in the industry in the 1990s, most modern RNAV systems provide on-board performance monitoring and alerting, therefore the navigation specifications developed for use by these systems can be designated as RNP.

许多RNAV系统能提供非常高的精度，并有RNP系统提供的许多功能，但不可能提供对其性能的品質保證。Recognising this, and to avoid operators incurring unnecessary expense, where the airspace requirement does not necessitate the use of an RNP system, many new as well as existing navigation requirements will continue to specify RNAV rather than RNP systems. It is therefore expected that RNAV and RNP operations will co-exist for many years.

不过，RNP系统的存在改善了运行完整性，允许更接近的航路间隔，并可提供足够的完整性来允许只使用RNP系统在特定空域内导航。The use of RNP systems may therefore offer significant safety, operational and efficiency benefits. While RNAV and RNP applications will co-exist for a number of years, it is expected that there will be a gradual transition to RNP applications as the proportion of aircraft equipped with RNP systems increases and the cost of transition reduces.

功能要求

RNAV规范包括对特定导航功能的要求。功能要求包括：

1. 飞机相对于航迹位置的连续指示，显示在飞行员主視野中的导航显示器上；
2. 显示距离活动航点的距离和方位；
3. 显示地速或距离活动航点的时间；
4. 导航数据存储功能；
5. 适当的RNAV系统故障指示（包括其传感器）。

导航错误组件和警报

侧向导航

The inability to achieve the required lateral navigation accuracy may be due to navigation errors related to aircraft tracking and positioning. The three main errors are path definition error (PDE), flight technical error (FTE) and navigation system error (NSE). The distribution of these errors is assumed to be independent, zero-mean and Gaussian. Therefore, the distribution of total system error (TSE) is also Gaussian with a 標準差 equal to the root sum square (RSS) of the standard deviations of these three errors.

PDE occurs when the path defined in the RNAV system does not correspond to the desired path, i.e. the path expected to be flown over the ground. Use of an RNAV system for navigation presupposes that a defined path representing the intended track is loaded into the navigation database. A consistent, repeatable path cannot be defined for a turn that allows for a fly-by turn at a waypoint (because nearness to waypoint and wind vector may not be repeatable), requires a fly-over of a waypoint (because wind vector may not be repeatable), or occurs when the aircraft reaches a target altitude (because target altitude is dependent on engine 推力 and aircraft weight). In these cases, the navigation database contains a point-to-point desired flight path, but cannot account for the RNAV system defining a fly-by or fly-over path and performing a maneuver. A meaningful PDE and FTE cannot be established without a defining path, resulting in variability in the turn. Also, a deterministic, repeatable path cannot be defined for paths based on heading and the resulting path variability is accommodated in the route design.

FTE relates to the air crew or 自動駕駛's ability to follow the defined path or track, including any display error (e.g. Course Deviation Indicator (CDI) centering error). FTE can be monitored by the autopilot or air crew procedures and the extent to which these procedures need to be supported by other means depends, for example, on the phase of flight (i.e. take-off, climb, cruise, descent, 著陸) and the type of operations. Such monitoring support could be provided by a map display.

NSE refers to the difference between the aircraft's estimated position and actual position.

纵向导航

Longitudinal performance implies navigation against a position along a track (e.g. 4-D control). However, at the present time, there are no navigation specifications requiring 4-D control, and there is no FTE in the longitudinal dimension. The current navigation specifications define requirements for along-track accuracy, which includes NSE and PDE. PDE is considered negligible. The along-track accuracy affects position reporting (e.g. "10 NM to ABC") and procedure design (e.g. minimum segment altitudes where the aircraft can begin descent once crossing a fix).

定名

RNAV规范的表示法为RNAV X，例如RNAV 1。其中的“X”是指海上航行时的横向导航精度，预期在空域、航路或程序内运行的航空器有95%以上的飞行时间达到此要求。

目前没有RNAV方法的规范。

飞行计划

飞机沿空中交通服务（ATS）航路、特定程序和特定空域的运行资格的手动或自动通知会通过飞行计划提供给空管员。飞行计划程序在相关的国际民用航空组织文档有所表述。

参见

• VNAV
• LNAV
• 垂直导航的定位器性能

外部链接

• RNAV Tutorial – 佛罗里达国际大学
• Getting To Grips with Modern Navigation – 空中客车公司

[[Category:航空儀表]] [[Category:無線電導航]]