Performance Based Navigation (PBN) is a concept developed and standardised by ICAO.
In a nearly 300-page manual, ICAO explains in gory detail the following principle: the aircraft navigation system (i.e. the GPS) must meet increasing levels of performance in order to navigate increasingly complex situations.
PBN standards were not developed with UAS in mind, but we can agree the general concept does apply. Different levels of performance are used to accomplish different objectives. For example, if using GPS to navigate across the ocean, the requirements are different than if using GPS to conduct an airport approach.
So, how does this relate to UAS and, specifically, UAS operations at the higher end of the risk spectrum?
Regulators have been pursuing a “risk based” approach to UAS integration. Sometimes it’s called “Risk Based Compliance”, sometimes “Risk Based Approvals”, sometimes it is referred to as the “Safety Case.” The idea is the same – start with what you want to accomplish, identify the hazards, and design your operation, aircraft, and equipment to mitigate those hazards. Sound familiar? It’s the same concept as PBN, except PBN is more narrowly defined with respect to the GPS system.
What do we want from our autopilot GPS in high risk (i.e. BVLOS) operations?
We want positional accuracy so we can accomplish the mission.
We want it to be consistently reliable, monitoring itself so it can tell us how confident we can be in what it tells us (i.e. “integrity”).
According to the European Space Agency Navipedia: “Integrity is the measure of trust that can be placed in the correctness of the information supplied by the navigation system. Integrity includes the ability of the system to provide timely warnings to users when the system should not be used for navigation.” Integrity tells you when things are good, and it tells you when things are not so good. Accuracy deals with precision. Ideally you want both, but they don’t always go hand in hand. In aviation it’s essential to know when they don’t.
truFYX, uAvionix’s new GPS receiver, is a navigation source for BVLOS or other high-risk autopilot mission.
In Q2 2019 it will be certified as a TSO-C145e Class Beta-1 GPS receiver, capable of providing position and integrity to an integrated navigation system.
It is the first GPS to be approved under a new paradigm pioneered by uAvionix’s skyBeacon product, one which provides a method for obtaining Design Assurance Level (DAL) C for Complex Commercial-Off-The-Shelf (COTS)devices.
For the first time ever, an aviation GPS can leverage the cost and quality basis of the commercial market and still provide aviation-grade integrity.
A market solution now exists that can be used by regulators to drive standards, policy, or guidance for gaining CAA approval for high risk operations. Obtaining a waiver or platform type certification just got a little bit easier.