Performance-based navigation (PBN)

PBN defines navigation performance requirements for aircraft flying on an ATS route, terminal procedure, or approach procedure. These routes and procedures are composed of waypoints which are expressed by WGS 84 coordinates rather than fixes expressed by radial/bearing and distance from ground navigation aids and permit the flexibility of point-to-point operations.

Since 2009, New Zealand has been in the process of implementing Performance Based Navigation (PBN) across the aviation system.

Since the 1920s, aircraft have navigated at night and in bad weather (known as Instrument Flight Rules) by flying in a series of straight lines between radio beacons located on the ground. As these beacons have limited range, a flight between two points will often need to plot an indirect and inefficient zig-zag course using several different ground-based navigation aids (GBNA).

This type of navigation requires commercial aircraft to use large airspace separation buffers, because of both the inaccuracies of ground-based navigation methods and the need to protect against operational errors.

PBN moves aircraft navigation away from this methodology to a system primarily reliant on satellite-based technologies, utilising Global Navigation Satellite Systems (GNSS) such as the USA’s Global Positioning System (GPS). This enables aircraft to fly routes directly between virtual waypoints at set geographical coordinates, rather than between physical beacons. As the number of possible virtual waypoints is effectively infinite, routes using them can be much more direct than those using GBNA.

There are two types of PBN: Area Navigation (RNAV) and Required Navigational Performance (RNP).

RNAV is simple straight-line waypoint-to-waypoint navigation, whereas RNP is more advanced and can enable curved routing.

Conventional vs PBN route structure (source: Boeing)

PBN delivers a range of benefits in New Zealand.

• Improved safety of departure, en-route, terminal and approach operations brought about by improved navigational accuracy. Increased accuracy means that there is more reliable separation from terrain and other traffic, and hence a lower risk of collision with either.
• Improved operational efficiency achieved by more direct routes with more flexibility (e.g. avoiding inclement weather). PBN enables shorter, more efficient approaches to landing and improving flight schedule reliability.
• Reduced infrastructure costs as fewer GBNAs are needed to enable day-to-day operations by PBN equipped aircraft (although there is a need to maintain a minimum GBNA network for contingency purposes).
• Increased airspace and airport capacity, due to more efficient design of routes in controlled airspace. More efficient approach and departure procedures means that more aircraft can take off and land per hour.

• Reduced environmental impact and fuel costs due to reduced fuel burn from shorter routes and more efficient climb and descent paths.

• Reduced community exposure to noise in some cases, where the design of routes can be tailored to minimise the frequency and proximity of aircraft flights over communities. However, this does not necessarily mean that the noise impact will be reduced for all communities, and noise impacts may be exacerbated in some cases where new routes are created.