View Full Version : Rnp/ Rnav

1st Apr 2008, 13:09

Do all RNAV departures have to be flown with GPS RNP equipped planes? or they can be flown with DME/DME RNP also ? Does RNAV SID require RNP-1 or B-RNAV planes can follw them ?

Lots of questions I know, but..........:p

1st Apr 2008, 13:48
no need of GPS.
If the SID requires more than RNP5 accuracy, it will be on the plate.

1st Apr 2008, 14:38
No need for GPS at all. Have been doing RNAV departures and arrivals for quite some time now in classic 737s. They can work quite nicely even down to RNP 0.5 if you have sufficient DME coverage for rapid updating. If ANP becomes worse than RNP (for example with NAV radios switched to manual) the plane tells you in big amber letters right across the Navigation Display that you're on your own now.

1st Apr 2008, 14:43
Hi, nice resume here..>>


1st Apr 2008, 14:47
AFAIK, all RNAV SIDs in the US (FAA AIM Chapter 5-2-7.f) and Europe, plus numerous other places, require RNP-1. If you know of any exceptions (US/Europe), please post them.

Also, an airplane must be certified to RNP-1 to operate on SIDs/STARs that require RNP-1. If any of its systems are degraded or inoperable, the DDPG must be consulted to ensure the RNP-1 certification remains valid. For example, the 744 requires 2 IRUs and 2 FMS/CDUs operational for RNP-5.

1st Apr 2008, 15:29
GPS (or GNSS) not mandatory, DME-DME can be used. If the RNAV requires GPS equipment, Jeppesens state it in the notes on the relevant page i.e. "GNSS required".

1st Apr 2008, 19:17
Intruder, you are right!

FE Hoppy
1st Apr 2008, 19:26
The whole point of RNP is that it's not navaid specific. However the RNP concept has not been adopted the same way in all countries so for example my Aussie studes have to have GNSS to fly rnav arrivals and approaches because it's specified on the plate as RNAV(GNSS). It would be great if we could have just one set of rules worldwide. Perhaps we should create an International Civil Aviation Organisation to set regs that we all stick to.:ugh:

2nd Apr 2008, 23:07
If your systems best is DME/DME, don't forget that at beginning of T/O roll, often your equipment will make a runway position update - the accuracy that follows from that update normally satisfies SID requirements.

3rd Apr 2008, 20:52
Reading the following link will answer a lot of questions for this thread I think.

I need to read it again in more detail, but in effect it is saying as long as your nav system is meeting the nav accuracy required for that phase of flight (SID/STAR, MTAP) at the time, then your good to go ! Irrespective of you nav suite. Please lets read it in more detail and correct me if I missed the boat.

It also has the reference also about runway updating.

GOOGLE 'RNP certification' and its the 3red one down.

The A320 FCOM limitations section states ;
FMGS lateral and vertical navigation has been certified for after take-off, en route and terminal area operations, for instrument approach procedures (except ILS, LOC, LOC-BC, LDA, SDF, and MLS), and for missed approach procedures.

Then it goes on to say what nav accuracies it has been demonstrated to with GPS primary, with or without warious combinations of; AP,FD and NAV MODE.

Then the most interesting bit;
Without GPS PRIMARY the accuracy has been demonstrated, provided the appropriate RNP value is checked, OR entered on the MCDU, and HIGH ACCURACY is displayed.

For the non-bus drivers 'HIGH ACCURACY' is just a function of the MCDU that 'checks for you' the difference between the required and actual nav accuracy. Then tells you if you have HIGH or LOW ACCURACY. i.e. so you don't have to check it your self constantly during the STAR. Its all automatic for normal operations using the database anyway.

5th Apr 2008, 17:32
Thanks guys,

I Fly the Boeing NGs in Asia. Just as a matter of fact, I happened to notice that the local authority had approved the airplanes as RNP5. Now, since RNAV departures require P-RNAV or RNP1, I was wondering if we are authorised for RNAV departures. I've put the question up to the employer but awaiting a credible response. So........................:O

5th Apr 2008, 18:40
If your systems best is DME/DME, don't forget that at beginning of T/O roll, often your equipment will make a runway position update - the accuracy that follows from that update normally satisfies SID requirements.
However, if your system is not CERTIFIED for RNP-1 (FAA AIM Chap 1, Sec 2, par 1-2-2), you cannot LEGALLY fly an RNP-1 procedure, despite the fact that the equipment may [temporarily] have the required accuracy. On-board monitoring capability is an integral part of RNP certification. Also, FAA Advisory Circular 90-100A is very explicit that aircraft certified under earlier AC 90-45A RNAV criteria (prior to 2005) may not be compliant with the standards required for current RNP-1 procedures.

the local authority had approved the airplanes as RNP5. Now, since RNAV departures require P-RNAV or RNP1, I was wondering if we are authorised for RNAV departures.
You cannot legally fly an RNP-1 RNAV departure with only RNP-5 certification. There may be airports outside the US and Europe that do not require better than RNP-5 for SIDs, but I don't know them off hand.

5th Apr 2008, 19:31

If you are B-RNAV approved (RNP-5) you can fly published RNAV departures.

If you P-RNAV approved (RNP-1), you can fly published P-RNAV departures.

BRNAV departures either use a Navaid or RWY track to climb you above MSA, from where you can navigate using B-RNAV without having to monitor track accuracy with raw data. P-RNAV departures have no such requirements below MSA.

Typically, RNAV SIDS will be overlays of existing conventional SIDs.

Good idea to check with your company before you use them though!


6th Apr 2008, 07:10
This link to an ICAO document shows where all the various international RNAV and RNP standards should be coming together in 2008. It clarifies the naming conventions, and requirement for on-board performance monitoring and alerting.

As FE Hoppy said its all over the shop, and is very much equipment and state specific at this stage until everyone gets on the same page. Sorry I cant help with your specific questions re your operations.


6th Apr 2008, 08:27
Thanks very much ATPL :ok:,

A very crisp and clear post.
I would also now request you for the basis of your very important info which can be produced incase of any ambiguity.


6th Apr 2008, 08:55
I agree with ATPL.

Most European SID & STARS are B-RNAV (exc. Stockholm Arlanda, Copenhagen and AMS STAR during night). Nav aid or rwy track is provided bellow MSA and sophisticated ATC radar is used as back-up should single RNAV source (as req for both B-RNAV and P-RNAV) should fail after takeoff.

Somewhere on Eurocontrol or ECAC (not shure at this point) web pages there are country per country RNAV status (P- or B-RNAV)

There is a miscocnception between a lot of people that P-RNAV is same as RNP1. Only required precision is the same but other aspects are not like P-RNAV requires only 1 RNAV system (ref. JAA TGL 10), while any RNP is a standalone system so there have to be double FMS (or GPS) for back-up

6th Apr 2008, 12:28
Another question:
When I fly a conventional SID with the FMS, do I have to check the position with raw data information? Even when the position accuracy is 0.3NM or more?

FE Hoppy
6th Apr 2008, 13:16
If you are using LNAV to fly a non RNAV procedure of any kind then legaly you must monitor the prescribed nav aids on which the procedure is based.

Be very careful accepting advice on what you can or cannot do, as these regs are very different in different parts of the world. What is legal in EU may not apply in the mid or far east or other areas.

As I said in an earlier post, there is no standard method of implementation so beware!!!!!

6th Apr 2008, 17:50
Hoppy is right.
For example, one of the very first RNAV departure procedules in the USA was at KLAS, and the navigation accuracy stated was, RNP 0.3

6th Apr 2008, 20:46
That may well be true, but FAA AC 90-100A of March 2007 has "harmonized" RNAV and PRNAV requirements, standards, and procedures with ICAO standards. AFAIK, ALL RNAV SIDs and STARs in the US require RNP-1 or RNP-2, and that the aircraft systems and/or operators be certified for them. All current RNAV SIDs that I can find at LAS are RNAV1.

While GPS may not be required for RNP-1 certification and operation, in the US a pilot still cannot legally fly an RNP-1 / PRNAV procedure unless the aircraft is certified and the equipment is operating in a mode that is still certified for it. From par. 10.a.(4) and 10.b of AC 90-100A:

(4) If not equipped with GPS/GNSS, aircraft must be capable of navigation system updating using DME/DME/IRU for RNAV 2 or RNAV 1 routes, as well as RNAV 1 Departure Procedures (DPs) and Standard Terminal Arrivals (STARs). As stated in paragraph 8.b.(1), if the navigation system does not automatically alert the flight crew of a loss of GPS/GNSS, the operator must develop procedures to verify correct GPS/GNSS operation.

b. General Operating Procedures. Operators and pilots should not request or file U.S. RNAV routes or procedures unless satisfying the criteria in this AC. If an aircraft not meeting these criteria receives a clearance from ATC to conduct an RNAV procedure, the pilot must advise ATC that he/she is unable to accept the clearance and request alternate instructions.

If you read further, you will find that for DME/DME only updating, manual runway position updates on takeoff are permitted, but auto-tuning of DMEs for updating is required. So, again, you have to look into your Flight Handbook, DDPG, and OpSpecs (or equivalent) to ensure you retain the required certification for a degraded system.

While "737incognito" is correct that many European SIDs and STARs are BRNAV only, that is because they are overlay procedures that can be flown with radio NavAids in the terminal area and require BRNAV for transitions and enroute.

6th Apr 2008, 20:54
Fair point to all, I should not have linked P-RNAV and RNP-1 since it's not that simple. I was just trying to keep it basic for capt.topgun since he seemed new to it all.

capt.topgun, you'll need to find references for you part of the world and your company I'm afraid. Like FE Hoppy said, there is no standard method of implementation. But hopefully you're now clear on the basic difference between flying overlay departures to B-RNAV transitions and P-RNAV departures.


7th Apr 2008, 14:57
ICAO is currently introducing the Performance Based Navigation (PBN) concept http://www.icao.int/pbn/ - it is supported by a draft manual which contains a number of navigation specifications for RNAV 10, RNAV 5, RNAV 2, RNAV 1, Basic RNP 1, RNP ACH and RNP AR APCH. (These nav specs provide detailed guidance on the airworthiness and operational approval requirements although they are not in themselves regulatory documents - it is up to the State to publish the requirements)

RNAV 10 = current RNP 10



RNAV 1 = US RNAV Type B and P-RNAV (as long as you can engage LNAV by 500ft agl and you don't use VOR/DME RNAV)

Basic RNP 1 = RNAV 1 for GNSS only.

RNP APCH = RNAV Approach with GNSS


In Europe B-RNAV should only be used on very simple SIDs/STARs above MSA. P-RNAV is being introduced in many States http://www.ecacnav.com/Future_Applications/RNAV_Interactive_Map. P-RNAV may be based on GNSS and/or DME/DME