Hello All, This post is an extension of the Post raised by Flyer767 on 1.9.11. I am interested in using RNP but some simmers are using it for Approaches. I was under the impression that the use of RNP, having watched a DVD of Westjet, that RNP was used at airports where there were difficult terrain and the landing airport had NO radio navigation facilities and the airline companies had installed routing in the aircraft FMC to accommodate these airports and that the crew used VFR for landing. I havethe PMDG Flight Crew Training Manual which mentions RNP but does not give instruction on its use. I have also searched the Net for a Tutorial but without any real success. Is there anyone in this Forum who has the necessary knowledge. Much obliged. richard welsh.

RNP approaches are published. You can find an example at KEWR. Select the approach in the CDU and fly using VNAV and LNAV, It has been a while since I tried a RNP approach and I am not sure what to do with the altitude window. After selecting APR, my guess is that you set the altitude window to the missed approach altitude. I am sure other will add their comments. Thanks,

Richard- RNP is actually pretty simple. It simply states the Required Navagation Preformance in a designated area. It is not specific for diffucult approaches or anything like that.Matter of fact you will find that many US airports have begun or already implemented these procedures. ( KSFO, KORD etc. ) It basically sets the plane on a specific course, point by point with ALT constraints as required. This allows for a better understanding of a procedure , reduced workload by ATC and the pilots, and fuel savings in some cases. To fly an RNP approach, simply load in as published. You MUST use LNAV/VNAV for the approach. Most pilots use the AP, but if your willing you can fly manually so long as LNAV/Vnav are engaged and use the FD. However, the AP should be disengaged no later than 50 ft AGL

RNP approaches can/do exist at airports with radio navigation aids. However due to terrain, it might not be possible to have a conventional ILS/VOR/NDB approach for all runways as these require a straight approach course. For example, an airport might have an ILS approach for RWY 26, but it might not be possible for RWY 08. An RNP approach may therefore allow a curved approach to get you into RWY 08 with lower minimums than a circling approach. As for flying the RNP approach, the FCOM is probably of more use. The general principle isn't too complex though; just fly the approach in VNAV/LNAV.

For the record, Kelowna (CYLW, Which ya saw in the westjet vid) has a full ILS approach. Don't know when the video was taken but way back in the day they did have an offset LOC. Havn't seen the westjet video, but I don't think they were flying an IAP thing with the FMS providing vertical guidance. I have no experience with RNP stuff outside of the NGX, but I sorta thought of it as a standard GPS/RNAV approach with just some lower minimums.

...but I sorta thought of it as a standard GPS/RNAV approach with just some lower minimums.

Not quite. The final approach segment for a GPS/RNAV approach still has to be straight, in which case you might as well install an ILS. Not practical if there's a mountain in the way. RNP allows not only lower minimums, but allows radius to fix (curved approach) segments to avoid the terrain you otherwise wouldn't be able to.

Hi, Thanks guys for your replies, varied as they are. richard welsh.

RNP approaches are published. You can find an example at KEWR. Select the approach in the CDU and fly using VNAV and LNAV, It has been a while since I tried a RNP approach and I am not sure what to do with the altitude window. After selecting APR, my guess is that you set the altitude window to the missed approach altitude. I am sure other will add their comments. Thanks,

My company's procedure is to select field elevation in the MCP when CLOP:Cleared for the approachLNAV/VNAV engagedOn a published portion of the approachPrior to G/P leg If we go missed, that alt is set on gear retraction. I think in reality you could select the missed approach altitude when 300' below that altitude.

Sounds like you do not arm the approach?

My company's procedure is to select field elevation in the MCP when CLOP:Cleared for the approachLNAV/VNAV engagedOn a published portion of the approachPrior to G/P leg If we go missed, that alt is set on gear retraction. I think in reality you could select the missed approach altitude when 300' below that altitude.

You can set missed alt in the MCP when you're in approach mode i.e. within 2 miles, 2000ft AAL or past the FAF can't you? IIRC....

Sorry to hijack the thread but here goes something that leaves me nonplussed and since we're on topic maybe someone will be able to enlighten me: I personally find that the way precision approaches are being labeled nowadays leaves a lot of room for confusion. In my opinion, they should leave the name RNP out of the approach. There is a lot of overlapping... in the case of airliners equipped with an FMC, a GPS approach will be flown with Lnav or Lnav+Vnav. And that still is an RNP approach in the sense that the acft must satisfy an RNP with it's GPS as primary means of updating the FMC position. BTW, the GPS will probably be the only means of satisfying an RNP of 0.3, since the IRS will have drifted beyond that by the time you get to your destinaiton (I don't know about radio updating though, perhaps in areas with lots of VORs/DMEs you can satisfy an RNP of 0.3) And since RNP approaches have an RNP of 0.3 or 0.15, they are essentially the same as GPS approaches flown with Lnav/Vnav. Let's take for example the published Rnav approaches for KEWR 4R: 1. Rnav (RNP) Z RWY 04R2. Rnav (GPS) Y RWY 04R They are, for all intents and purposes, one and the same! The RNP plate clearly states GPS required, which needless to say is also required for flying the GPS plate. They have the same fixes, same vertical profile, and same missed approach! So why not forgo the publication of the RNP plate and simply publish one RNAV (GPS) plate listing the minima for Lnav/Vnav 0.3 RNP and 0.15 RNP alongside the other minima published (LPV, Lnav, circling)? And then there's the whole issue of some countries calling it GPS others calling it GNSS... it took a long time to figure this stuff out by myself and I think things could be simpler.

Sounds like you do not arm the approach?

Nope. LNAV/VNAV for us. We don't have IAN, and I don't know if you would arm APR for that equipment or no.

And one final question: you will notice that the LPV DA is even lower than that of the RNP 0.15 (Lanv/Vnav)). In other words, you could say that WAAS+GPS satisfies even the most stringent required navigation performance, resembling an ILS approach. My point is: if the minima for Lnav/Vnav are so close to that of LPV, and Lnav /Vnav are being fed GPS data, then airliners' GPS closely match general aviation's WAAS-enhanced GPS receivers correct? Here's what I had never thought about: does that mean that the DoD offer a more precise GPS signal to airliners than GA? It would seem so, since GPS approaches flown worldwide (i.e., no WAAS) have similar minima to those those in the US. Sorry if this seems confusing, but that's how confused I am now that I stopped to consider these things.

I think a major difference with a published RNP approach (RNP on plate header) is the "radius to fix" arcs that leave a fix on a specifac heading. Additionally, RNP approaches usually includes decents during turns on the approach as close as 2.5 miles from the runway.

Ok Brad, that makes sense when RNP is used to fly around otherwise inpenetrable terrain... but what about in KEWR's case. There's no terrain and the RNP approach is as straight as the Empire State!