Originally Posted by
SuperflyTNT
Thanks to everyone for getting in and replying. Much appreciated.
So, RNAV and RNP are both Performance Based Navigation(PBN) and work around the same principle - use nav aids/radio beacons around them to fly from point A to point B rather than flying over each nav aid/beacon. The difference between the two being, RNP requires on board monitoring and alerting system and will alert the pilot if he happens to pass the minimums for that particular RNP route.
Do correct me if my understanding to this is wrong.
Also is the RNAV coupled with the INS/IRS for navigation purposes ?
I would say yes, they are coupled with INS/IRS because it's the basic RNAV route structure requirement. In modern days, most RNAV routes require GPS onboard; when GPS is lost, Navigation is allowed to revert back to IRS/INS.
As a background, there are 3 basic systems in navigation:
1. GPS
2. IRS
3. NAVAIDs such as VOR, DME, etc.
In the beginning when RNAV is introduced, aircraft requires only FMS and IRS/INS to satisfy flying from point to point. With updates from ground navaids periodically to ensure positions.
In modern aircraft, FMS/FMC has a feature of monitoring and alerting if the a/c exceeding certain accuracy and integrity (such as GPS PRIMARY LOST, NAV ACCUR DOWNGRAD displayed on airbus MCDU). The crew can monitor the accuracy from PROG page of airbus MCDU.
Therefore, in modern a/c like Boeing and Airbus, they perform RNAV routes as RNP due to its monitoring and alerting capability as default system onboard (Reference: "Airbus Getting to Grips with PBN).
That's I reckon.