RNP 101
To understand RNP we need to first talk about basic instrument flight. Since the 50s the standard instrument navigation, that is navigation by reference to instruments only has been conducted using ground based radio beacons called VOR, VORTAC, TACAN and NDB. Instrument approaches to airports were also conducted using these navaids and one additional navaid call the ILS. If you don't know what they are; well it’s not important for this discussion. Extended overwater navigation was conducted with LORAN and believe it or not up until the 70s with celestial navigation. In the 70s INS (Inertial Navigation System) navigation came into wide use. An INS is a navigation aid that uses a computer and motion sensors (accelerometers) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references. So for you pilots it’s a gyroscope or a combonation of 2 or 3 of them hooked to a computer commonly called a FMS or flight mangement system. INS navigation ushered in the age of RNAV or Area Navigation by use of onboard computer systems. Initially it was accomplished with INS. RNAV brought important capabilities to aviation navigation. RNAV aircraft can fly directly between waypoints rather than flying to/from ground-based radio beacons or relying on vectors from air traffic control. Maneuvering directly to distant waypoints rather than zigzagging over a scattered course of ground-based radio beacons significantly improves efficiency. So eventually this technology moved from oceanic navigation to navigation over the land as well.
RNP can be seen as the evolution of RNAV. It increases the precision of aircraft position using GPS. Now in addition to the INS feeding information to the FMS you have a GPS unit feeding position updates to the computer. It allows aircraft to stay on track using direct legs from even longer point to point legs and calculates turn radius from point to point for detailed flight navigation. Rather than having to monitor radio aids to see if they go off the air this combination of computer, gyro, and GPS monitors actual navigation performance and alerts the crew if tolerances are exceeded.
Now as I said RNP was originally developed for use by aircraft flying transoceanic routes where ground-based navigation aids are not available. Without radar or radio beacons, aircraft flying over oceans are required to meet specific navigation performance (ergo the name Required Navigation Performance, RNP) criteria to ensure that they do not conflict with one another. For example, operating RNP-10 requires that an aircraft establish with a high degree of certainty its location within 10 nautical miles.
Steve Fulton, a pilot at Alaska Airlines who used to work for Honeywell, realized that the airline could solve operational difficulties it was having in Juneau, Alaska using a more precise form of RNP. It was not uncommon for 10% of the airline's flights there to be diverted due to the mountainous terrain and poor weather. Fulton developed a procedure that began with Alaska aircraft using multiple GPS units in the same aircraft to establish their location with a high degree of accuracy. It also included the addition of enhanced GPWS (Ground Proximity Warning System) installation on all of our aircraft. EGPWS loaded a ground map of the entire globe into the aircraft’s computer. With certainty of location, the Alaska aircraft could follow narrow, pre-programmed paths between mountains in good weather or bad. In addition to guiding planes toward the runway, RNP procedures included terrain-avoiding directions away from the airport in case of a missed approach or for departures. Alaska's first landing using RNP occurred in 1996 at Juneau, Alaska. Alaska was the first airline to be certified to use RNP for approaches and departures, the first to train all there pilots to use the system and is using the system more widely than any other airline.
OK now I forgot the question. I’ll post this basic RNP 101 and use it to answer the rest of the questions.