RNAV & RNP
 

Can someone point about the difference between RNAV and RNP. How would you explain it to somebody if you had to? Thank you.

On the 737s the FMC RNP defaults to .3 and for an RNP approach the crews change them to a lower value making the the approach a little more accurate. You'll see RNP then / ANP. I.e. 0.30/0.04. RNP is required navigational performance and ANP is actual navigational performance.

Careful with the wording. Yes crew sets a lower value of RNP for an RNAV approach but this in itself does not make the approach more accurate. It simply reduces the margins by alerting you if you subsequently exceed that value during the approach. If the entered value is exceeded "NAV UNABLE RNP" will occur to warn the crew.

RNP requires a monitoring system to let you know when you've reached the limit of navigational accuracy, RNAV does not require a similar monitoring system.

If you get the term RNP on the chart ie RNAV(RNP) RWY XX, it would most likely also state 'Authorisation Required' or SAAAR (old FAA term). These approaches are typically curved, sometimes in high terrain environments. They require authorisation for airline, aircraft type and crew and as previously stated, a Required Nav Performance which has to be met.
An RNAV on the other hand could be RNAV(GPS) or RNAV(GNSS) is your standard RNAV.

In simple terms SuperFlyTNT,

RNP is a statement of navigational position accuracy that has to be maintained in a designated airspace.

RNAV is a method of navigation which involves flying directly point to point which Designated Operational Coverages of Ground-aids, without having the need to dog-leg all over the place wasting time and precious fuel.

Clear?

Area navigation (RNAV) - A navigation method that allows aircraft to operate on any desired flight path within the coverage of ground- or space-based navigation aids, or within the limits of the capability of self-contained aids, or a combination of both methods.


RNP is Rnav with addition of an onboard performance monitoring and alerting capability. A defining characteristic of RNP ops is the ability of the a/c navigation system to monitor the navigation performance it achieves and inform the crew if the requirement is not met during operation.


The difference is very simple RNAV being area navigation and RNP being the monitoring system to check whether you are achieving the required accuracy or not.

To start with...

RNP & RNAV have nothing in common (assume)

RNAV is a method of navigation..... RNP is part of a concept viz Performace Based Navigation

RNAV

A method of navigation which would allow the system to take any desired path/course within the coverage of nav beacons/or the navigation system

PBN-> method of navigation is dependent on the performance of the nav equipemnt
RNP -> The regulatory number (rnp .3 1 5 10) to be complied with to fly in the airspace/route/procedure with which it is associated.

Only when it is certain that my equipment has an ANP(actual nav performance) for at least 95% of the time equal to or better than RNP can i be allowed to fly any track/path/route that i may want to.

eg

DEL-MAA

Conventional route- vor to vor -> DPN BPL HIA MAA

RNAV route -> DPN abeam BPL abeam HIA maa
THe abeam points have been mathematically made (pseudo ranges/ghost stations) by the system, the end result would be a straight line b.w DEL and MAA

Systems such as DME DME can be used only when they remain within the coverage are of the beacons i.e DPN,BPL,HIA,MAA any 2 atleast at all times
same for VOR VOR

more morden systems such as gnss give me a wider coverage are such as north pole to south pole

so RNAV and RNP have nothing in common but are related .to be able to do RNAV ANP needs to be RNP or better that is what is common b/w them

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.