Can someone please explain what the difference is between an RNAV (GNSS) approach and an RNAV (RNP)?
Well, personally I get the difference between an RNP approach and an RNP AR approach. But can someone please explain the difference between an RNAV (GPS) approach and an RNP approach? Because the FAA are clear as mud on it:
FAA factsheet "Required Navigation Performance Approaches" says...
This fact sheet will focus on the most common navigation specification called “RNP Approach (RNP APCH)” and titled Area Navigation (RNAV), “RNAV (GPS) Rwy XX”.
As of February 2016 there are over 3,600 LPV lines of minima serving 1,762 airports...there are over 3,500 LNAV/VNAV lines of minima serving 1,669 airports...and over 6,000 LNAV lines of minima at 2,747 airports.
Note: The other approach navigation specification, or set of aircraft and aircrew requirements needed to support a navigation application within a defined airspace, is reserved for complex airspace and called RNP Authorization Required Approach (RNP AR APCH). Authorized pilots of certified aircraft can fly IAP based on RNP AR APCH, which are titled “RNAV (RNP) Rwy XX”.
...but the FAA.gov also say on their webpage “Satellite Navigation - NAS Implementation”:
At present, there are no RNP Approach IAPs that are not of type AR. This may change in the future
...and I have seen that statement reproduced elsewhere (maybe it has just been parroted, I don't know). For instance, the experts on that Jeppesson webinar underfire linked to earlier say that GA pilots can't do RNP approaches - not just RNP AR but any RNP.
Whilst according to AC 120-38D 5-1a:
There have been questions on whether GNSS is an RNAV or RNP system. The answer is GNSS is both an RNAV and RNP system because RNP is a subset of RNAV that also includes a requirement to provide on-board navigation system accuracy performance monitoring and alerting. Therefore, an RNP system is also capable of RNAV. GNSS equipment provides accuracy performance monitoring and alerting which, by definition, makes it an RNP-capable system.
RNAV(GPS) approaches require GPS, which includes on-board performance monitoring and alerting. Therefore, an RNAV(GPS) approach is an RNP procedure where the initial, intermediate, and missed approach segments are RNP 1.0. The LNAV final approach segment is RNP 0.3.
(c) None of the preceding statements should be confused with RNP AR that requires special aircraft and aircrew approval.
So there we have it. According to the FAA, RNAV (GPS) approaches are RNP APCH procedures and there are thousands of them. Except that currently none of them are not of the type AR. Why would anybody be confused?