RNP 1 vs. RNP 10 - Which is more restrictive?

[SubsonicMortal]

As in the subject line, it only seems logical that RNP 1 is more restrictive but someone I had a chat with recently tried to convince me that RNP 10 was more restrictive. Have I got it all wrong or is it logical that a Required Navigational Performance factor of 1nm is means tighter tolerances than 10nm... After 5min I started to zone out of the discussion but his argument had something to do with "out of radio contact".

[TopBunk]

As I understand it, from a basic point of view:

1. the closer you are to the ground (whether on departure or arrival) the lower the RNP value required.

2. the further you are from an airport (and land) the higher numerical value of RNP required. In other words, Oceanic sectors (with no radio position updating) maybe ok with RNP10.

3.Carrying out an approach to the FAF or even lower, will require an RNP of better (lower) than 1, probably 0.3 or better.

Hope that helps

[gas path]

I can see where your collegue is coming from, in as much that 10nm when you are in the middle of the ocean is quite restrictive! Having said that 1nm when in crowded airspace is probably on the generous side

[divinehover]

It's not that simple. You can be RNP-1 capable but not RNP-10 capable. This is because RNP-10 is used in the oceanic enviroment and the requirement is not so much for accuracy but for Nav without the assistance of groung based nav aids (VOR/DME).

The following is from the ICAO PBN Manual Vol 2

RNP-10:
Requires that aircraft operating in oceanic and remote areas be equipped with two independent Long Range Navigation Systems (LRNS) comprising an Inertial Navigation System (INS), an Inertial Reference System IRS/ Flight Mangement System (FMS) or a Global Navigation Satellite System (GNSS) with an integrity such that the navigation system does not provide an unacceptable probability of misleading information

RNP-1:
The following systems meet the accuracy, integrity and continuity requirements of these criteria.

a) Aircraft with E/TSO-C129a sensor (Class B or C), E/TSO-C145() and the requirements of E/TSOC115b FMS, installed for IFR use in accordance with FAA AC 20-130A.

b) Aircraft with E/TSO-C129a Class A1 or E/TSO-C146() equipment installed for IFR use in accordance with FAA AC 20-138 or AC 20-138A.

c) Aircraft with RNP capability certified or approved to equivalent standards

Volume II, Part C C-3-5 WORKING DRAFT 5.1 - FINAL


Anyone wanting a copy of the ICAO PBN (Performance Based Navigation) Manual which has all this info in it can PM their e-mail address and I'll pass it on in electronic format. It's a 1.28MB file

[IO540]

Surely, in the GPS age, you fly the whole time with something like RNP 0.01 so all this old ICAO stuff is barely relevant.

[Nocti]

I0540,
Sorry to break the news to you, but all this "old ICAO stuff" is quite new - the ICAO PBN manual being published just two years ago.

Sure, a GPS receiver can, under certain circumstances give an EPE of single metre accuracy, but RNP is about how a total system works; it's intergrity, redundancy and operational procedures. The technical standards have as much to do with rejecting reflected signals along with continuity of performance with terrrain and structure masking.

Bit more to it than meets the eye.

[ALK A343]

When it comes to keeping navigation accuracy RNP-1 is logically more restrictive than RNP-10. The requirement is to be able to meet a Nav. accuracy of 1NM or better for 95% of the flight-time in RNP-1 airspace, whereas in RNP-10 airspace it is 10NM or better. What your friend probably meant by RNP-10 being more restrictive is the equipment required to continue flight in RNP-10 airspace. Since it is mostly in use over oceanic airspace, you need two independent long range navigation systems. On the A320 it would be two FMGCs, two MCDUs and two IRSs at least, without GPS you would have a timelimit of 6.2 hrs since IRS alignment and 5.7 hrs since last FM radio update. Beyond this time your estimated position error is expected to exceed 10NM. If GPS is installed there is no time limit.
In RNP-5 or B-RNAV (european airspace) you can continue flight with one FMGC, one MCDU, one IRS, one VOR/DME or one GPS receiver for FM navigation update. The above systems requirements are from FCOM 2.04.51.

[SubsonicMortal]

ALK A343, Thanks for that write-up and the FCOM reference. It's a lot clearer to me now. I do remember now my colleague talking about the equipment required to meat a certain RNP - which, in the case of RNP-10, would be more restrictive in terms of a compliance point of view. Thanks for clearing that up!

[divinehover]

The info I put forward is from the March 2007 Final draft version. The Manual was given to me by ICAO at the PBN seminar in Nairobi in Dec 08'

I say again. Just because you are RNP-1 capable doesn't mean you automatically have RNP-10 capability. RNP-10 is an Oceanic requirement and the equipment spec is for remote oceanic navigation.

[NEWYEAR]

Looking for RNP...

My answer is that both RNP 1 and RNP 10 are using in different areas of operation and for that reason they can´t be compared between each other.

Areas of operation:

Oceanic and remote continental
Oceanic and remote continental airspace is currently served by two navigation applications, RNAV 10 and RNP 4. Both rely primarily on GNSS to support the navigation element of the airspace. In the case of RNAV 10, no form of ATS surveillance is required. In the case of RNP 4, ADS contract (ADS-C) is used.

Continental en-route
Continental en-route airspace is currently supported by RNAV applications. RNAV 5 is used in the Middle East (MID) and European (EUR) regions, but as of 2008, it is designated as B-RNAV (Basic RNAV in Europe and RNP 5 in the Middle East). In the United States, RNAV 2 supports en-route continental airspace. At present, continental RNAV applications support airspace specifications which include radar surveillance and direct controller-to-pilot voice communications.

Terminal airspace: arrival and departure
Existing terminal airspace concepts, which include arrival and departure, are supported by RNAV applications. These are currently used in the European (EUR) Region and the United States. The European terminal airspace RNAV application is known as P-RNAV (Precision RNAV). Although the RNAV 1 specification shares a common navigation accuracy with P-RNAV, this regional navigation specification does not satisfy the full requirements of the RNAV 1 specification. As of 2008, the United States terminal airspace application formerly known as US RNAV Type B has been aligned with the PBN concept and is now called RNAV 1. Basic RNP 1 has been developed primarily for application in non-radar, low density terminal airspace. In future, more RNP applications are expected to be developed for both en-route and terminal airspace.

Approach
Approach concepts cover all segments of the instrument approach, i.e. initial, intermediate final and missed approach. They will increasingly call for RNP specifications requiring a navigation accuracy of 0.3 NM to 0.1 NM or lower. Typically, three sorts of RNP applications are characteristic of this phase of flight: new procedures to runways never served by an instrument procedure, procedures either replacing or serving as backup to existing instrument procedures based on different technologies, and procedures developed to enhance airport access in demanding environments (RNP APCH and RNP AR APCH).
RNP approaches to 0.3 NM and 0.1 NM at Queenstown Airport in New Zealand are the primary approaches used by Qantas and Air New Zealand for both international and domestic services. Due to terrain restrictions, ILS approaches are not possible, and conventional VOR/DME approaches have descent restrictions more than 2,000 ft above the airport level. The RNP approaches and departures follow curved paths below terrain level.

And, do not forget: Special Aircraft and Aircrew Authorization Required

[CJ Driver]

RNP isn't just position input

IO540 - the concept of RNP is relatively recent, and it is worth remembering that it stands for Required Navigation Performance. The lower numbers of RNP in many legacy aircraft are limited not by the sensor performance (as you say, many modern FMS systems know where they are to better than a tenth of a mile) but by the performance of the rest of the system, including flight directors, autopilots, and so on. For example, older autopilots with limited steering authority from the navigation kit often can't meet the requirements for accurate tracking at RNP 0.3.

[FE Hoppy]

You may want to take a few hours out and complete the ICAO PBN training here:Enjoy!

[aterpster]

This RNP AR IAP just became effective this past Thursday. Note the vast improvement in both safety and minimums over the other RNAV IAP aligned with Runway 24.

Where possible an RNP AR approach is supposed to have a line of minimums of RNP 0.30 with a non-RNP missed approach. Then, if necessary other lines of lower minimums using smaller RNP values. Because of the close-in terrain issues at this runway end, only RNP 0.10 would fit.

As good as these concepts are, I believe the equipment bar is set far higher than necessary. The standards were established on airline equippage when the standards were implemented and fail to take into account other methods of compliance; particulary SBAS.

[aterpster]

divinehover:

I say again. Just because you are RNP-1 capable doesn't mean you automatically have RNP-10 capability. RNP-10 is an Oceanic requirement and the equipment spec is for remote oceanic navigation.

Picking at nits: most oceanic is remote. OTOH, some land masses are areas of remote navigation as specified by ICAO.

[NEWYEAR]

Hi Everybody,

An aircraft having approval for RNP 5 requiring input from ground based navigation facilities such as VOR/DME may not be operated in RNP 10 airspace where such facilities are not available.

Areas of operation are different.
BR.

[DFC]

Isn't there also a time factor in all of this. The required performance must have the aircraft contained within the required constraints for 95% of the time.

My underdstanding is that the time factor is very important. Fly a 60 mile series of legs at RNP 1 and (say 180Kt average speed and the required accuracy must be maintained for 15 minutes).

Fly a 3200nm RNP 10 leg at 480Kt and the required accuracy has to me maintained for 400 minutes.

The requirement is 10 times less accurate but the time it has to be held for is more than 20 times as long.

Therefore the probability of an error exceeding the limits is greather on oceanic routes and this has to be acccounted for.

I know that there are many other factors however that is my very simplistic view that RNP 10 is harder to do that RNP 1 - even before one takes the other factors into account - naviads, communications, surveilance.

[Capn Bloggs]

Surely, in the GPS age, you fly the whole time with something like RNP 0.01 so all this old ICAO stuff is barely relevant.

If the AP can track that accurately. My 717 wanders around like a chook with it's head cut off. The FMS knows where it is but the AP doesn't put it there.

[aterpster]

IO540:

Surely, in the GPS age, you fly the whole time with something like RNP 0.01 so all this old ICAO stuff is barely relevant.

You're speaking of accuracy, not RNP. Accuracy is just one component of RNP.

[Denti]

My aircraft usually tells me its ANP is 0.02NM. Certified down to CAT I autoland/autorollout GLS approaches, in the works to certify it to CAT IIIb status in same which has allready been demonstrated. 60 year old design too, cant be all that bad

[aterpster]

Denti:

My aircraft usually tells me its ANP is 0.02NM. Certified down to CAT I autoland/autorollout GLS approaches, in the works to certify it to CAT IIIb status in same which has allready been demonstrated. 60 year old design too, cant be all that bad

RNP "apples and oranges."

I flew 2 CATIII autoland birds. The L-1011 didn't even know what ANP was. The pre-GPS 767 sort of knew....

Wonders have been done with good ILS ground equipment for some 40 years now. The numbers within the last mile or so prior to the runway exceed any sense of RNP and ANP, but it is a different system.

LPV and GLS resemble ILS, not RNP.