FAA Draft AC 90-119 to make RNAV LPV Approaches classified as 'Precision Approach'!

[tony]

1 hour ago, Mooney Dog said:

 

Here's a page out of the garmin AFMS for the GPS 175 and GNC 355/375 systems. They can be installed in class 2 aircraft which absolutely meet the requirement for PBN. 

 

I was under the assumption this was largely due to the fact GPS was never considered a precision approach. This document making a change where the FAA now say it IS a precision approach could very well change that rule on alternate airports. 

Ok Doug, I was trying to help you understand PBN, but you know better.  Does your Garmin have a message that says unable RNP?

[Ragsf15e]

21 minutes ago, tony said:

Ok Doug, I was trying to help you understand PBN, but you know better.  Does your Garmin have a message that says unable RNP?

Isn’t PBN the overall concept of Performance Based Navigation and RNP the Required Navigation Performance for each specific segment of the flight or type of approach?  According to the referenced AC90-105a, our ifr waas gps meets the standards (appendix a).  Obviously we cannot fly the Authorization Required approaches.  The AC specifically calls out differences for Part 91 vs 91k, 135, 121, etc.  From appendix A:

A.2.1 Approval for RNAV (GPS) or GPS Approaches. Aircraft with approval to conduct RNAV (GPS) or GPS approaches meet the performance and functional requirements in this AC for RNP APCH instrument approaches without RF legs.

The alphabet stew has changed it’s meaning several times and is almost unusable.

[tony]

1 hour ago, Ragsf15e said:

Isn’t PBN the overall concept of Performance Based Navigation and RNP the Required Navigation Performance for each specific segment of the flight or type of approach?  According to the referenced AC90-105a, our ifr waas gps meets the standards (appendix a).  Obviously we cannot fly the Authorization Required approaches.  The AC specifically calls out differences for Part 91 vs 91k, 135, 121, etc.  From appendix A:

A.2.1 Approval for RNAV (GPS) or GPS Approaches. Aircraft with approval to conduct RNAV (GPS) or GPS approaches meet the performance and functional requirements in this AC for RNP APCH instrument approaches without RF legs.

The alphabet stew has changed it’s meaning several times and is almost unusable.

Rags there is a couple of issues.  A single GPS Navigator can not meet the availability requirement  of 1x10-5 nor does it have a solution an independent solution to compare it to do determine containment..  Those are system level requirements for a NAV system.  A WAAS GPS certainly has the accuracy.  But that's not Performance-Based Navigation Operations which was the subject of the draft advisory circular.  

[midlifeflyer]

As far as I can tell, the only big deal - and it is a big deal - in this is the collection of GPS rules which appear in a number of different ACs and consolidating them into one.  I don't really see a change in the definition of "precision approach" in the draft and no mention of the only place I think it really maters - choice of alternate airports. The draft actually punts on that:

Yet operators of both GPS and WAAS do face some requirements and limitations when evaluating potential alternate airfields. The AIM, chapters 1 and 5, describe these requirements and limitations in detail. Operators should refer to the AIM to understand FAA policy regarding use of GPS and WAAS to meet part 91 alternate airport weather minima. Commercial operators need to follow the provisions and limitations contained in their applicable OpSpecs.

When I see that I can use a  600-2 forecast rather than 800-2 when selecting an alternate airport based on an RNAV (GPS) approach with LPV miima, I'll be more impressed.

[Mooney Dog]

6 hours ago, tony said:

Ok Doug, I was trying to help you understand PBN, but you know better.  Does your Garmin have a message that says unable RNP?

Actually yes, they do. It talks about that in the pilots guide for them. They're known as LOI annunciations as well. Im curious as to why this would be in my pilots guide if it does not apply to my unit or if my unit could not do it?

 

Again ill ask. If i am unable to use PBN, Why does ICAO ask that i file R / B2, c2 ,d2 ? Schools such as ATP flight school even advice their students to file R / b2, c2 ,d2 ,s1 for their G500 / 430W equip aircraft. 

5 hours ago, Ragsf15e said:

Isn’t PBN the overall concept of Performance Based Navigation and RNP the Required Navigation Performance for each specific segment of the flight or type of approach?

Yes. Its why the change from the FAA to ICAO filing system was a big deal. Some aircraft are able to navigate fine with GPS units, but unable to use them for accuracy on approaches. 

 

Foreflight even has basic guidance on how to file for RNP PBN

[Ragsf15e]

7 hours ago, tony said:

Rags there is a couple of issues.  A single GPS Navigator can not meet the availability requirement  of 1x10-5 nor does it have a solution an independent solution to compare it to do determine containment..  Those are system level requirements for a NAV system.  A WAAS GPS certainly has the accuracy.  But that's not Performance-Based Navigation Operations which was the subject of the draft advisory circular.  

I read the whole section 4 of the AC90-105a that talks about the 10^-5 integrity checking but I didn’t see anything that said a single gps can’t do that.  In appendix A I found this under the applicability which specifies the IFR gps types approved under this AC… these are the TSO that our ifr and ifr waas gps are approved under aren’t they?

A.2.4 Qualified Avionics Equipment and Airworthiness Approval. Aircraft with the following avionics equipment and an appropriate airworthiness approval automatically qualify for RNP APCH to LNAV minima capability without further documentation by virtue of the avionics Technical Standard Order (TSO) and airworthiness approval:
1. GPS stand-alone systems approved in accordance with TSO-C129( ), Class A1, or TSO-C146 operational Class 1, 2, or 3 and installed in accordance with AC 20-138( ).
        
Im just trying to understand what we’re all disagreeing about.  I think standard gps approaches are RNP, which falls under the PBN umbrella.  We can clearly fly some of these, however we can’t fly the AR ones, and some of our equipment is more capable than other (RF legs, LPV vs LNAV, etc), but I think most of that is covered in the Two authorized TSO system types for our ifr GPSs.

[MikeOH]

I have a GNS430W and have always believed that I can fly RNP approaches with it.  The problem is that nearly all RNP approaches are labelled "AR" so I can't fly those.  Perhaps that scarcity is responsible for the belief that you can't fly them with a lowly GNS430W.

Here's a chart that seems to provide back up (sorry, it already had the non-WAAS models highlighted. You need to look at the GNS4xxW/5xxW line):

 

 

[PT20J]

This stuff is so confusing that I just check that an approach is in the GPS database and, if so, I figure I can fly it. 
 

[RobertGary1]

The faa is migrating to performance based navigation away from gps since gps is specific to the United states and other countries have argued they should  be able to use theirs. So this clarifies it’s the performance not the technology that’s import. So the Europeans can use Galileo the Russians can use  GLONASS Chinese airlines can use BeiDou Etc. It’s not limited to gps. 

[carusoam]

gents…

I think there may be confusion looking backwards…

 

1) When GPS first came out… they got approved for enroute navigation only…. No approaches.

2) Next step included approaches with manual RAIM checks… No vertical guidance.

3) WAAS was invented… RAIM became automated… vertical guidance came in multiple flavors.

4) Looks like it is now time for the FAA to clean-up all the history, and wash out the old confusion…

5) If you don’t have WAAS… you don’t have precision for precision approaches…

6) Some old portable GPSi have waas and are 20 years old…. Portables are not precision approach allowed…

7) Many analog approaches took into account how analog signals bend and echo… and straightened out how scallop shaped the victor highways actually are…  these differences compared to GPS straight lines are probably getting reviewed for any real errors that may be found using a GPS to follow an old VOR approach… 

 

Does that help any?

Best regards,

-a-