RNAV(RNP) approaches

[RobertE]

I'm starting to see these approaches appear.  From what I've read ( source is Wikipedia!) WAAS provides a sufficiently accurate signal but it sounds as if special training and, maybe, special software is necessary to fly curved paths.  Does anyone have a better understanding of this?  Will I ever get assigned such an approach?

the airport where I first noticed this is Oakland.

[Marauder]

I'm starting to see these approaches appear.  From what I've read ( source is Wikipedia!) WAAS provides a sufficiently accurate signal but it sounds as if special training and, maybe, special software is necessary to fly curved paths.  Does anyone have a better understanding of this?  Will I ever get assigned such an approach?

the airport where I first noticed this is Oakland.

I'd like to think we would be eligible for these AR approaches. The reality is that the special training and equipment validation will probably never make it down to our level. That may change if they remove the "AR" requirement.

[Dave Colangelo]

This may be of some use or this power power point from the FAA and here is some more info on RNP approaches.

[PaulM]

https://bruceair.wordpress.com/2016/03/18/garmin-gtn-avionics-and-rf-legs/

Software is #1, the support of all of the leg types Including RF. 

But, looking at the approaches they are designed for the limitations of transport category aircraft, flow control, noise abatement, large radius turns and the pre LPV hardware.   Get the big iron down without manually vectoring them to the ILS which reduces controller workload.  

For example KOAK GPS RNP 12 Z has a DA of 299'  Where the KOAK GPS 12 Y has a LPV DA of 209'.  We are going to get vectors to final for the LPV.   we are never going to fly un-vectored multi legged approaches in a radar environment. 

http://www.ifr-magazine.com/issues/1_12/features/The-GPSILS-Approach_121-1.html

[Jeff_S]

For a flavor of this type of approach, check out the RNAV (GPS) 34 into Panama City, KECP. It's not an RNP approach and technically the segments aren't curved, but they sorta feel that way when you're flying them. And the vertical nav calls for some pretty quick descents along the path. The first time I flew that was quite challenging, much more so than your basic T-configuration RNAV approach.

 

edited: the approaches "aren't" curved, not "are" curved.

[Greg252AY]

RNP approaches take special air crew training and aircraft operator has to have approval to perform these approaches. I use RNP approaches at work. Kind of a pain to go thru the approval process but the RNP let you shoot low approaches into mountain airports for example. 

[Hank]

57 minutes ago, Jeff_S said:

For a flavor of this type of approach, check out the RNAV (GPS) 34 into Panama City, KECP. It's not an RNP approach and technically the segments are curved, but they sorta feel that way when you're flying them. And the vertical nav calls for some pretty quick descents along the path. The first time I flew that was quite challenging, much more so than your basic T-configuration RNAV approach.

Yeah, that one was difficult my first time, too. I was concentrating so hard on everything I forgot to drop gear and had a real hard time descending while maintaining my desired speed. finally realized my mistake about 1200-1300 agl, kind of late, but was able to land anyway. At least now I've been warned about these things . . .

[kris_adams]

That's a pretty cool approach Jeff.  I'd like to fly it sometime.  Seems like I'm always landing on 16 there.

[kortopates]

Curved approach paths

There is more than one type of Approach with Curved Approach path - although the curved approach path segment is referred to an RF - or radius to fix leg.

These are:

1. RNAV RNP approaches. Currently all RNP approaches are AR or Authorization Required. Currently these are all RNP 0.15 and RNP 0.3 approaches which we can not do. However we are capable of RNP 1.0, but its doesn't make any sense to add RNP 1.0 approaches because WAAS approaches are essentially equivalent to RNP 0.3 - so I doubt we'll see RNP approaches we can do with our WAAS GPS since an LPV will provide lower minimums anyway). So currently we can only fly RNP terminal departure and arrival procedures (RNP 1.0 & higher).
2. RNAV GPS approaches - We're beginning to see RF legs used in RNAV GPS approaches. These are not AR or Authorization Required (for us Part 91 operators) and thus we can fly them if we have the equipment to do so (as cited in the navigators AFMS). I have one locally at KCRQ RNAV GPS X 24 which is an LPV approach with a RF leg. 

Support for these RNAV GPS approaches with RF legs began with the Garmin GTN Navigators with the recent 6.x s/w release. As far as I know, that's the only navigator & s/w capable of flying them. Its also the only approach capability the GTN has over the GNS boxes. 

So with GNS boxes were limited ti flying the KCRQ RNAV GPS Y 24 which has the same LPV minimums as the Xray version of the approach. The Zulu version which is an RNP AR approach with RF leg has higher minimums than our Xray and Yankee approaches - so our WAAS approaches without AR win anyway!

As for there practicality, the few I have seen thus far don't add any yet - at least not to us as pilots. But I expect that over time they will provide tangible benefits for us  to airports with significant terrain or obstacle concerns. As for getting vectored past the RF leg to final anyway, we already know the term "never" has no use in aviation  I routinely fly multi-leg approaches in my area of SOCAL. I'd say it varies based on the traffic demands of each approach and the controllers needs. It will even vary on the same approach at different times.  Plus we can typically ask to fly the full approach for training and we often do with it being granted when traffic allows.    

 

Edited May 24, 2016 by kortopates

[Loogie]

Pull up the RNAV (RNP) 19 at DCA, we shoot it all the time, lots of criteria to meet. Special training required.  Not a lot of room to get it wrong...