PBN

PBN, or Performance Based Navigation, is a new concept for RNAV (area navigation). The ability to navigate through an area without going to specific ground station points. Hence, we won’t have to fly to a station and then track outbound as RNAV allows us to fly pretty much anywhere.

In the 90s the GPS came out and was certified for aircraft. GPS revolutionised the NAS — national airspace system. Initially backups were required, but eventually the system evolved into our modern GPS based system.

• GPS satellites tell us our position.
• SBAS, whose satellites provide information and make our position even more accurate.
• GBAS has ground based transmitters that make the position ultra accurate.
• Eventually came PBN, which allows an aircraft to fly a 3D Path through the NAS, and allows aircraft for varying performance capabilities to fly varying path requirements.

Hence, there are certain procedures and paths we can fly and others that we can’t. Think of PBN as an umbrella for everything thats RNAV.

RNAV is not only GPS. There is DME/DME RNAV, when 2 or more DMEs are used to triangulate your position.

IRS that starts with a known ground position and then tracks the aircraft acceleration as it flies. This way it predicts its position.

RNAV is not just GPS. It is GPS + ALL of the other technology we have developed over time to help us figure out where we are, without going directly to a ground based navigation system.

RNP — Required Navigation Performance

RNP is a PBN system which includes onboard performance monitoring and crew alerting capability. For an aircraft to meet the requirements of PBN a specified RNAV/RNP, accuracy must be met 95% of the flight time.

RNP includes two very important parts;

1. The ability to autonomously monitor the systems performance, knowing whether it is as accurate as it needs to be.
2. If it can’t guarantee the accuracy, then it needs to be able to alert the crew, so the crew can find alternate navigation procedures through the NAS.

It works because the receivers have got extra satellites then constantly double check its position, and RAIM which allow for crew alerting. If RAIM detects a bad position, or if it doesn’t know if the position is bad, it is no longer meeting PBN requirements and it is able to alert you.