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Turlad

ANP/RNP Capability

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Really enjoying the 747 gents - it is without a doubt the best thing PMDG have done. Anyone mentioned the gorgeous contrails yet.....

 

Question though -

 

Does the 747 have an ANP/RNP capability? There doesn't seem to be a calculation/indication of ANP - Actual Navigational Performance, so I'm guessing the 747 isn't certified for RNP / GPS approaches. Is this a limitation of just our sim rendered version or does the 747 lack this ability in the RW too.

 

I know that many airlines have only just (last couple years) been certified for GPS approaches, including the one I fly for, so I take it the 747 hasn't been updated yet. I would guess the jumbo would always never fly into somewhere without at least a CAT 1 ILS, so maybe it's at the bottom of the list for update?

 

Anyone know for sure?

 

Adam.

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Adam (might want to add your surname as per rules) thats a good question. It must be RNP capable, as it plies the NAT tracks that require RVSM, but it is an earlier version of the software on the NGX, which is probably about 9-10 years ahead of the 744 (Real world)

 

I did immediately notice the VNAV seems a bit more "sloppy" than the NGX or 777, possibly because it is much bigger, but it just does not seem quite as accurate (Not saying PMDG got it wrong) I am sure this is the case for the real airplane.

 

You are right though, I don't see a 747 doing and RNP GPS type approach like into Innsbruck or Queenstown.

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RVSM isn't directly related to RNP. There are two kinds of navigation performance specification: area navigation (RNAV) and Required Navigation Performance (RNP). These specifications are similar. The difference is that navigation specification that includes a requirement to have an on board performance monitoring and alerting system is referred to as RNP specification. An RNAV specification has no such requirement. The monitoring and alerting system alerts the crew in the requirement is not met (in the 777 there's an indication at the bottom of the ND and on the PFD if you've got the NPS enabled). You'll also get FMC messages. The 747, our one at least, doesn't have this.

 

You can have specifications like: RNAV 10, RNAV 5, RNAV1 (PRNAV) and also RNP APCH 0.3 etc

 

The numbers indicate the TSE - Total System Error - the deviation of the desired position from the true position in nm. RNAV 10 would be for oceanic, RNAV 5 for en-route, RNAV 1 for the arrival (until final approach at which point you navigate by ground based nav aids).

 

Basically RNP 0.3 allows pure LNAV / VNAV navigation right down to minimums.

 

Personally I find VNAV on the new 747 to be really good. It seems to behave similar to the 777 version. The NGX VNAV is actually better - both in fsx and in the real world. I guess it's a slightly newer software.

 

Adam Turley   

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I assume that prior to an RNP approach, you'd go to the appropriate POS page and put in the required number. For example if a procedure requires RNP 1.0, then you would insert 1.0 in LSK3L (currently shows 2.00), whereas ANP is your "actual navigation performance". So if the ANP number exceeds the RNP number then you'd have to abort the procedure. (turlad I'm sure you're familiar with all this stuff, I'm just trying to figure it all out in context of the 747).

 

cbd75b9ad4.jpg

 

http://www.boeing.com/commercial/aeromagazine/articles/2011_q4/5/

 

Though this link says that operators have to have their aircraft specifically equipped to do these approaches? That's what confuses me a bit, since there clearly is an RNP/ANP indication in the FMC. Couldn't you just enter your required RNP value and monitor the ANP throughout the approach? I'm not quite sure how this works, certification-wise in something older like the 747.

 

Michael H

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I drew the picture a while back to try and organise RNAV specs and make them understandable.

 

It's a very complex subject, but basically, you will need certification for each spec. With each spec you get certified for, the better the yield for the operator with regard to airspace utilisation.

 

I don't know if the Boeing offer the RNP-AR spec to 747-400's. If they did, hypothetically, it would probably mean system enhancements to greatly improve the 747-400's position "monitoring" and "alerting". This would probably mean upgrading the FMCS and the IDS. In addition to this, personnel training would be undertaken and a flight performance and maintenance trend monitoring program would need to be set up, at a guess.

 

The Queen has a very basic position "monitoring" and "alerting" system. I don't know how extensive it's "alerting" has been modelled. In the Queen, you can probably get "virtual certification" for all the specs shown except: A-RNP, RNP-AR and probably RNP 0.3.

 

This document spells it out - go to Chapter 7.

http://www.icao.int/APAC/Documents/edocs/COSCAP_PBNOPS_HANDBOOK%20Version%202_4.pdf

 

 

2ajcldh.jpg

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There is no ANP/RNP page in the 747-400 nor any PFD pointers like the 777. The 747-8 has those.

 

However, the beats is equipped with 2 GPS units and not relying solely on IRS triple mix for position updates. Hence RNP compliance (not in polar regions) is available.

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