seperation from RNP-AR approach

[rabindra]

We are introducing a RNP-AR approach, and in a need of developing a ATC procedure . We have Terminal Radar but because of the limitation of the existing Radar most of the time we won't be able to monitor the progress of the A/C on the approach and missed approach. We have lot of VFR traffics in all direction form/to the airport and we have class C airspace. What is the seperation standard we can apply Between those VFR flights and the RNP-AR approach. Further the missed approach segment is also longer and takes huge airspace to attain the required altitude on MA holding.We are worried that the introduction of this approach may delay traffic further. Any suggestions ?

[topdrop]

I am recently retired and from memory, in Australia, a nav tolerance of 3 times the approach standard was applied then the 1 NM separation requirement applied.
As the worst RNP-AR approach standard applied here is 0.3NM, the nav tolerance of the other aircraft has to be 1.9NM away from the RNP approach path.
We had RNP departure and approach paths designed so that they missed a parachuting area and a VFR corridor - worked great.

[reynoldsno1]

In NZ it is 2 x the primary nav protection area + 1NM. The primary protection are for RNP(AR) is 2 x RNP. ICAO requirements are that RNP0.3 minima are always published, even if lower RNP values are also used. So, for an RNP0.3 approach it would be 1.6NM ...
The RNP(AR) missed approach segment (using the ICAO criteria) is problematic, and needs refining - I'm afraid you will just have to put up with it for now! Under certain circumstances it can be operationally beneficial to use RNAV(GNSS) missed approach criteria (and is permissible).

[roulette]

@Rabindra

Your main problem is the constraint of having Radar that cannot be used to always monitor the aircraft on APCH or missed (and you haven't indicated whether this is related solely to the RNP AR procedure track, or also includes other approaching/departing/enrt acft).

Effectively this means that you would have to apply procedural sep standards in those locations!

What I mean is that the containment of the RNP AR approach - which in your location would be designed to provider better obstacle clearance through RNP containment, lower minima and probably better (guided) missed approach - does not necessarily allow you to tighten separation standards from other IFR (PA, RNAV, conventional) and VFR acft - unless your ATM environment has the appropriate means of monitoring and control.

Most of the issues of introducing RNP AR procedures into a conventional air traffic environment are nothing to do with separation! The largest aspect that requires careful consideration is the introduction of a new type of flight procedure with different operational paradigms into an operational environment (including ATM, ATCs AND other operators) that - without careful planning, briefing and coordination - know nothing about RNP AR and the particular procedure in question.

The ATC procedures (after education and knowledge attainment!) should in the very first implementations - I suggest - not include any tighter separations than you already have in place. You should also conduct a planned 'trial/monitoring' period with a follow-up review before considering reduction of sep standards (lateral, vertical, crossing) and even sequencing.

Some of the early problems experienced in early RNP AR implementations in other countries including inappropriate vectoring by ATCs, inappropriate altitude &/or speed assignments and sometimes even bungled timing & sequencing. Once cleared for an RNP AR APCH, inappropriate over-control of aircraft established on such an APCH can in some cases mean that the APCH cannot effectively be commenced/continued, and in some cases could actually increase risk to either the acft on the APCH or other aircraft in the close vicinity. So, education of ATCs of the RNP AR performance and operational requirements in general and those specific to the procedure and/or operator SOPS for that procedure are quite critical.

For practical advice and lesssons learned, suggest to you speak to regulators and ANSPs in those jurisdictions where RNP AR APCHs have been used for some time (eg, US/FAA, Australia - CASA & Airservices, NZ - CAA & Airways Corp) - rather than seeking such critical advice through fora such as this. It's probably also worth talking to major operators of such procedures for this feedback on issues they've suffered or benefited from in various jurisdictions/ATM environments. Suggest someone like Qantas, because they have this kind of experience (gained over several years) in at least 2 (or all 3?) of the countries mentioned above.

Info & guidance from the ICAO PBN material, including output from regional panel and workshops and seminars, is useful. Airline manufacturers (eg, Airbus, Boeing, Embraer, ATR, etc) also have material that may be useful to you.

In addition, whilst not a state-sponsored document, the following dissertation by a lady from Portugal appears to provide a nice overview of all issues related to RNP AR implementation, with a focus on what's actually required in doing a Flight Operational Safety Assessment (FOSA) - which includes ATM/ATC considerations. I've not read the whole thing - simply skimmed through it - but it looks to be pretty thorough.
https://dspace.ist.utl.pt/bitstream/2295/787856/1/Dissertacao%20de%20Mestrado%20-%20Claudia%20Cabaco.pdf
Finally, the info provided by @Reynolds01 & @topdrop are, from memory, correct in terms of the RNP containment multiplier (2x in NZ, 3x in Oz) + 1NM buffer. Both mentioned RNP0.3 (in NZ that's the min even if RNP0.1 used for final APCH - and ICAO recommend that even if <RNP0.3 used in Final, one should also publish minima for larger RNP, including RNP0.3) .... BUT, please also note:
!!! you need to look at the actual containments applicable to your RNP AR procedure.
For the arrival/initial and intermediate APCH segments, it is normally RNP1 by dflt (may be less). The Missed probably splays out to RNP1 also.

Good luck
Contact me privately if you have very specific questions or would like more direct assistance

[Chess Mate]

Hi, I'm currently involved in a similar project. You should consider the fleet environment, in other words if you have simultaneously in the same airspace acft flying RNP AR procedures and conventional NAV procedures you MUST use the more restrictive criteria that it would be to consider all acft flying conventional NAV means. For me to give you a more detailed answer I should have more info about your project. Keywords: airspace concept, ICAO PBN Manual, Fleet capabilities, etc.

ICAO states (DOC4444)

5.4.1.2.1.4 Lateral separation of aircraft on published adjacent instrument flight procedures for arrivals and departures

5.4.1.2.1.4.1 Lateral separation of departing and/or arriving aircraft, using instrument flight procedures, will exist:

a) where the distance between RNAV 1, Basic RNP 1, RNP APCH and/or RNP AR APCH tracks is not less than 13 km (7 NM); or

b) where the protected areas of tracks designed using obstacle clearance criteria do not overlap and provided operational error is considered.

Note 1.— The 13 km (7 NM) value was determined by collision risk analysis using multiple navigation specifications.
Information on this analysis is contained in Circular 324, Guidelines for Lateral Separation of Arriving and Departing Aircraft on Published Adjacent Instrument Flight Procedures.

Note 2.— Circular 324 also contains information on separation of arrival and departure tracks using non-overlapping protected areas based on obstacle clearance criteria, as provided for in the Procedures for Air Navigation Services — Aircraft Operations, Volume II — Construction of Visual and Instrument Flight Procedures
(PANS-OPS, Doc 8168).

Note 3.— Provisions concerning reductions in separation minima are contained in Chapter 2, ATS Safety
Management, and Chapter 5, Separation Methods and Minima, Section 5.11.

Note 4.— Guidance concerning the navigation specifications is contained in the Performance-based Navigation
(PBN) Manual (Doc 9613).

5.4.1.2.1.5 RNAV operations where RNP is specified on parallel tracks or ATS routes. Within designated airspace or on designated routes, where RNP is specified, lateral separation between RNAV-equipped aircraft may be obtained by requiring aircraft to be established on the centre lines of parallel tracks or ATS routes spaced at a distance which ensures that the protected airspace of the tracks or ATS routes does not overlap.

[rabindra]

thanks all for you quick response and valluable suggestions.

[FlightPathOBN]

Rabindra,

Are you developing an RNP procedure for Kathmandu? I had looked at this a few years ago, but never heard anything on it.

There are several ways to work out the RNP Approach, especially from the South, as well as the Missed Approach. The trick is not to use idle descent but to use an optimized descent...

Please review and contact me through my website

Operations Based Navigation (http://operationsbasednavigation.com/)
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