Area Navigation (R-Nav) – Ibex Aviation Academy

Area Navigation System

Area Navigation is a system which permits aircraft to fly on any desired track using VOR-DME or self-contained navigational aids like INS or both
Phantom Stations generated by RNav as a bearing and distance from VOR-DME station assists in flying tracks without checking overhead a VOR
Required Navigation Performance (RNP) is the standard of accuracy required while flying RNav routes
Accuracy is defined on the basis of 95 % probability in both lateral as well as longitudinal directions
For example, RNP 5 means that 95% of aircrafts in that route would be within 5 NM radius of their stated position
RNP 5 also means that an aircraft would be within 5 NM of its stated position 95 % of the time

Required Navigational Performance could be specified for a route, a set of routes, an area or a volume of airspace of defined dimensions
RNav systems use a combination of VOR, DME, GPS, ILS, MLS, INS, IRS, ADC and Time information for position accuracy
The system processes these information and provides the Track Made Good, and Estimated Time of Arrival

RNav routes improve operational efficiency and cost for airliners by flying direct routes, reducing Flying time and Fuel
Air route capacity increases due to increased number of routes and reduction in horizontal and vertical separation
Area navigation provide choice of routes like ATC prepared RNav routes, By pass routes and Contingency routes
Ground based navigational facilities and holding locations can be reduced and optimised in area navigation system

Basic RNav System provides a position accuracy of 5 NM on 95 % probability
Precision RNav equipment provides a position accuracy of 1 NM on 95 % probability
2D RNav guides in horizontal plane, 3D RNav guides in both horizontal and vertical and 4D RNav includes a timing function

Waypoints can be fed in the RNav system as either Way Point Number or Beacon Frequency or as Radial and Distance From Beacon
Horizontal Situation Indicator can be used to display the output of R Nav System
Full scale deflection of HSI indicates 5 NM deviation from airway centre-line during en-route segment
HSI indicates full deflection when aircraft is 1.5 NM deviation in approach segment and 10 Deg deviation while tracking in or out using VOR-DME

2D RNav system works uses inputs from VOR-DME in its line of sight within the Designated Operational Coverage
Since DME provides Slant Range, DME inputs may induce errors when the aircraft is close to DME

4D RNav system receives inputs from INS, IRS and GPS and compares the position with that obtained from VOR-DME
Flight Management Computer automatically calculates the final accurate position using the best set of navaids called as FMC Position
DME-DME fix is the preferred choice for position fixing due to its higher accuracy levels
VOR–DME fix is the second choice since VOR accuracy is limited to 5°
VOR-VOR fix is considered as the third choice since the accuracy is limited to 35 NM

FMC calculates Wind Velocity in 4D RNav by an advanced form of Deduced Reckoning using TAS from ADC and Heading from RIC
Outside VOR-DME coverage, 4D RNav system uses IRS or INS for Deduced Reckoning using Last Known Position, Heading and TAS
RNav system automatically applies the required convergency values and provide headings to steer for flying Great Circle Routes