Since the foundations of modern commercial aviation were established following the Second World War, aircraft have typically navigated from A to B using a system of terrestrial navigational aids (referred to as ‘Navaids’ or ‘Beacons’). These are connected by a series of airways that act like highways. To put it simply, an aircraft departs an airport, joins the airways system, and follows the most appropriate routing to its destination. Whilst this approach has served the aviation industry well for decades, it has numerous limitations such as the limited range of terrestrial systems. The challenges of increasingly crowded skies, advancements in technology and a renewed focus on sustainability have driven the creation of a more innovative system – Area Navigation. 

What is Area Navigation (RNAV)?

The Area Navigation System, or ‘RNAV’, is a concept that allows the navigation of an aircraft along any desired flight path. That makes for a more direct, faster, and ultimately cheaper route to your destination. Air traffic control centers have established RNAV routes which are more direct than the old airways system, and allow aircraft to safely fly closer together.

How does it work?

Area Navigation is made possible by Global Navigation Satellite Systems (GNSS). GNSS is a broad term describing any satellite constellation that provides navigation, positioning, navigation, and timing services. There are five such constellations powered by different countries and regions. 

• GPS – United States
• QZSS – Japan 
• BEIDOU – China
• Galileo – Europe 
• Glonas – Russia

These derive highly accurate position data for an aircraft in two and three dimensions, referred to as ‘Lateral Navigation’ or ‘LNAV’ and ‘Vertical Navigation’ or ‘VNAV’. This position data is so accurate because it is not impacted by the range and position limitations of conventional navaids. 

What are the benefits of Area Navigation?

There are three key benefits of Area Navigation compared to traditional navigation. 

1. Time and fuel savings.
2. Reduced dependence on radar vectoring, altitude, and speed assignments allowing a reduction in required ATC radio transmissions, and
3. More efficient use of airspace.

Thanks to the proliferation of satellite navigation systems globally, the uses and accuracy of RNAV are vast. Depending on the equipment they have on board, pilots can use it for everything from supporting daytime navigation in a Cessna to flying highly accurate instrument approach procedures in an A350. As such it is categorized by accuracy, and there are three types of RNAV.

1. Basic RNAV – This is required to give a position of within 5 nautical miles, 95% of the time. All aircraft carrying over 30 passengers in European airspace are required to have this capability. 
2. Precision RNAV – This must be able to accurately identify an aircraft’s position within one nautical mile, 95% of the time.  
3. Required Navigation Performance ‘RNP RNAV’ – This combines lateral and vertical navigation to derive a position with an accuracy of less than one nautical mile. For lateral navigation, this can be expected to be accurate down to 0.1 to 0.3 nautical miles. 

The most accurate step – Performance Based Navigation

Performance Based Navigation (PBN) is an initiative that aims to standardize RNAV and RNP specifications around the world. PBN adds more specific guidelines on the accuracy required to use Area Navigation at different stages of flight. Essentially, this combines lateral and vertical navigation to provide a performance below RNP 1, which is less than one mile of accuracy. Location reporting for lateral navigation is expected to be between 0.3 and 0.1 nautical miles, bringing an incredible level of accuracy that allows aircraft to fly accurate approaches using GPS systems. An example of a PBN-based approach being implemented can be seen at Riga (RIX). We experienced this on the flight deck of an AirBaltic A220 first hand.