使用者:YFdyh000/區域導航

傳統導航與RNAV方法的主要區別

區域導航（英語：Area navigation）是一種儀器飛行規則（IFR）導航方法。這種方法允許飛機選擇導航信標網絡內的任何航線，而不是必須自導航信標飛至另一導航信標。這樣可以節省飛行距離、減少擁堵，並允許飛往沒有信標的機場。區域導航以前被稱為「隨機導航（random navigation）」，因此其縮寫為RNAV。

RNAV可以被定義為一種導航方法，它准許飛機在以航點為參考的導航信號覆蓋範圍內、獨立系統能力內或兩者組合的能力下在任何期望航路上運行。

在美國，RNAV在20世紀60年代得到發展，20世紀70年代公布了第一條這樣的航路。1983年1月，由於飛機使用慣性導航系統而非地面信標，因而成本效益分析顯示不利於維護RNAV航路系統，美國聯邦航空總署撤銷了所有美國本土的RNAV航路。RNAV在大規模引入衛星導航系統後被重新採用。

背景

隨著航空業的持續增長，對領空容量的需求也日益增加，因此強調優化利用現有空域。因應用「區域導航」技術能提高運行效率，故而導致了全世界各地區和各個飛行階段的導航應用發展。這些應用還可能擴展為為地面移動提供導航。

特定航線或特定空域內的導航應用必須以清楚、簡潔的方式定義，從而確保機組人員和航空管制員了解機載RNAV系統的能力，確定RNAV系統是否適合特定空域的要求。

RNAV系統的演變方式類似傳統的陸上航線和程序。特定RNAV系統通過組合分析和飛行測試來確定和評估其性能。對陸上運行來說，最早的系統使用甚高頻全向信標（VOR）和測距儀（DME）來估計位置；海上運行則使用慣性導航系統。領空和空中無障礙標準會跟進現有設備的性能而制定，規範基於目前可用的能力。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 所需導航性能 (RNP).

RNAV和RNP系統本身很是相似。兩者的關鍵差異是對機載性能監控和警報的要求。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.

許多RNAV系統能提供非常高的精度，並有RNP系統提供的許多功能，但不可能提供對其性能的品質保證。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.

不過，RNP系統的存在改善了運行完整性，允許更接近的航路間隔，並可提供足夠的完整性來允許只使用RNP系統在特定空域內導航。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規範包括對特定導航功能的要求。功能要求包括：

1. 飛機相對於航跡位置的連續指示，顯示在機師主視野中的導航顯示器上；
2. 顯示距離活動航點的距離和方位；
3. 顯示地速或距離活動航點的時間；
4. 導航數據存儲功能；
5. 適當的RNAV系統故障指示（包括其傳感器）。

導航錯誤組件和警報

側嚮導航

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.

縱嚮導航

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規範的表示法為RNAV X，例如RNAV 1。其中的「X」是指海上航行時的橫嚮導航精度，預期在空域、航路或程序內運行的航空器有95%以上的飛行時間達到此要求。

目前沒有RNAV方法的規範。

飛航計畫

飛機沿空中交通服務（ATS）航路、特定程序和特定空域的運行資格的手動或自動通知會通過飛航計畫提供給空管員。飛航計畫程序在相關的國際民用航空組織文檔有所表述。

參見

• VNAV
• LNAV
• 垂直導航的定位器性能

外部連結

• RNAV Tutorial – 佛羅里達國際大學
• Getting To Grips with Modern Navigation – 空中巴士公司

[[Category:航空儀表]] [[Category:無線電導航]]