RNP Approaches at GA Airports

Palmpilot

Palmpilot

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I have read relevant section in the AIM, IPH, and Aeronautical Chart User's Guide on this, but I'm not sure that I'm correctly understanding what I'm reading. My question is this:

Lately I've been seeing the note "RNP APCH" appearing on RNAV (GPS) approach plates at general aviation airports. This has been done for all of the RNAV (GPS) approaches at the few non-airline airports I've checked so far. Attached are some example approaches. What does this mean, and what are the implications for the average renter of spam cans?
 

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It's all part of Precision Based Navigation (PBN). Within PBN there are two main categories of navigation methods or specifications: area navigation (RNAV) and required navigation performance (RNP). In this context, the term RNAV x means a specific navigation specification with a specified lateral accuracy value. For an aircraft to meet the requirements of PBN, a specified RNAV or RNP accuracy must be met 95 percent of the flight time. RNP is a PBN system that includes onboard performance monitoring and alerting capability (for example, Receiver Autonomous Integrity Monitoring (RAIM)).



RNP:
•Total system error (TSE) allowed in lateral/longitudinal dimensions within an airspace for 95 % of the flight time on any part of any single flight.
•Max distances from flightpath centerline that must be maintained
•Aircraft Capability + Level of Service = Access

•ICAO RNP Types:
•RNP-1.0
•RNP-4.0
•RNP-5.0
•RNP-10.0​
•US RNP levels:
•RNP 0.3 – Approach,
•RNP 1.0 – Departure, Terminal,
•RNP 2.0 – En route​


Required Navigation Performance (RNP) is similar to Area Navigation (RNAV); but, RNP requires on-board navigation performance monitoring and alerting capability to ensure that the aircraft stays within a specific containment area.

RNP APCH has a lateral accuracy value of 1 in the terminal and missed approach segments and essentially scales to RNP 0.3 (or 40 meters with SBAS) in the final approach.

Advanced RNP (A-RNP), not to be confused with RNP (AR). Some features of A-RNP, such as the ability to fly some RF legs, are available if you have the current system software installed in a Garmin GTN navigator. Advanced RNP is a NavSpec with a minimum set of mandatory functions enabled in the aircraft’s avionics suite. In the U.S., these minimum functions include capability to calculate and perform RF turns, scalable RNP, and parallel offset flight path generation.

RNP Authorization Required (AR) Approach IAPs require authorization analogous to the Special Aircraft Authorization Required (SAAR) for Category II or III Instrument Landing System (ILS) procedures. Authorization Required (AR) procedures may only be conducted by aircrews meeting special training requirements in aircraft that meet the specified performance and functional requirements.

FAA has started publishing some approaches with RF legs that are not designated as RNP AR procedures. And, with some limitations, pilots who fly aircraft equipped with GTN-series avionics should be able to fly the RF legs used as transitions/feeder routes on those approaches.

If your airplane is equipped with, say, a Garmin GNS530W/GNS530W or GTN 750/650 (with an appropriate AFM supplement), you can fly RNAV SIDs and STARs based on RNP-1 criteria. And you can also fly en route segments that require RNP-2 accuracy. No special authorization is required at these RNP levels. Most, IFR certified GPS units are RNP capable.
 
It means “GPS Approach” for the most part. ;)

The FAA is in process of changing terminology on that, so you can expect a lot of confusion over the next 10 years or so.

What used to be “RNP”-something, “Authoruzarion required” now just says “authorization Required “.
 
To make it more confusing, this will also likely be adopted in the US...

https://www.icao.int/MID/Documents/2016/PBN SG2/2.PBN Charting - ICAO.pdf

As a transition, until 30 November 2022, approach charts depicting procedures that meet the RNP APCH navigation specification criteria must include either the term RNP or RNAV (GNSS) in the identification (e.g. RNP RWY 23 or RNAV (GNSS) RWY 23). However, from 1 December 2022, only the term RNP will be permitted.

Until 30 November 2022, approach charts depicting procedures that meet the RNP AR APCH navigation specification criteria must include either the term RNP (AR) or RNAV (RNP) in the identification (e.g. RNAV (RNP) RWY 23). However, from 1 December 2022, only the term RNP (AR) will be permitted.
 
MauleSkinner said:
It means “GPS Approach” for the most part. ;)

The FAA is in process of changing terminology on that, so you can expect a lot of confusion over the next 10 years or so.

What used to be “RNP”-something, “Authoruzarion required” now just says “authorization Required “.
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Thanks. One thing I'm wondering is whether a non-WAAS GPS can be used (with the LNAV minimums) to fly the RNP approaches that I posted. AIM 5-1-16f seems to imply that it can, because it says, in part, "During the pre−flight planning phase RAIM prediction must be performed if TSO−C129() equipment is used to solely satisfy the RNAV and RNP requirement."
 
There is no change to the approach or the criteria for flying it. It’s simply a terminology change.
 
With the FAA, the more things change, the more they stay the same...or the reverse. I'm still trying to remember my ICAO PBN string...:confused:
 
Palmpilot said:
Thanks. One thing I'm wondering is whether a non-WAAS GPS can be used (with the LNAV minimums) to fly the RNP approaches that I posted. AIM 5-1-16f seems to imply that it can, because it says, in part, "During the pre−flight planning phase RAIM prediction must be performed if TSO−C129() equipment is used to solely satisfy the RNAV and RNP requirement."
Click to expand...

Yes, you can. As long the GPS is IFR certified, you can retrieve it up from the database that's current, etc. You'll likely only get to fly to LNAV minimums.
 
The military helicopter I work with achieved RNP certification with a non-WAAS Embedded GPS/INS.

It was fun to fly the RNP 0.3 approaches into Fairbanks, AK when they first switched over...
 
Craigd31 said:
Yes, you can. As long the GPS is IFR certified, you can retrieve it up from the database that's current, etc. You'll likely only get to fly to LNAV minimums.
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Not likely. LNAV minimums are it for a non-WAAS, but IFR approach certified navigator. Also, unlike WAAS, a RAIM check has to be made before departure if an RNAV IAP is to be flown at the destination.
 
aterpster said:
Not likely. LNAV minimums are it for a non-WAAS, but IFR approach certified navigator. Also, unlike WAAS, a RAIM check has to be made before departure if an RNAV IAP is to be flown at the destination.
Click to expand...

Yep. Besides the containment area, there is a PRAIM requirement for the certification, based on the route and approach to be flown.
 
I know what RAIM is, but what's PRAIM?
 
Palmpilot said:
Thanks. One thing I'm wondering is whether a non-WAAS GPS can be used (with the LNAV minimums) to fly the RNP approaches that I posted. AIM 5-1-16f seems to imply that it can, because it says, in part, "During the pre−flight planning phase RAIM prediction must be performed if TSO−C129() equipment is used to solely satisfy the RNAV and RNP requirement."
Click to expand...

As you likely learned during your instrument training, you have to do a RAIM check if you have a non-WAAS GPS. Nothing changing there. You only get LNAV minimums.
 
N1120A said:
As you likely learned during your instrument training, you have to do a RAIM check if you have a non-WAAS GPS. Nothing changing there. You only get LNAV minimums.
Click to expand...
I'm not sure that GPS approaches had even been developed when I did my instrument training in 1992.
 
N1120A said:
Ah, so we shall make old jokes now :p
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I wasn't joking. I learned about RAIM through reading. It was not part of my instrument training, nor was it covered on my knowledge test for the instrument rating.
 
Palmpilot said:
I wasn't joking. I learned about RAIM through reading. It was not part of my instrument training, nor was it covered on my knowledge test for the instrument rating.
Click to expand...

I know. I was joking about making an old guy joke. I appreciate that you're always learning.
 
I am certainly fair game for old-guy jokes!
 
The only new approaches when I got my instrument rating/CFI-I were those new fangled MLS curved approaches that some FAA weenie dreamed up...

There weren't even four GPS vehicles then.
 
aterpster said:
Not likely. LNAV minimums are it for a non-WAAS, but IFR approach certified navigator. Also, unlike WAAS, a RAIM check has to be made before departure if an RNAV IAP is to be flown at the destination.
Click to expand...

OP indicated it was a non-WAAS gps, so LNAV min's are likely it. In theory, someone could have a non-WAAS gps and fly to LNAV/VNAV minimums, if they have the older baro-VNAV (barometric Vertical NAVigation). However, the LNAV/VNAV min's might actually be higher than LNAV min's, as is the case with RNAV (GPS) RWY 1 KGEU that he posted.
 
I fly rental planes both with and without WAAS. There are still a lot of KLN-94s in use, as a example of the latter, so I was glad to learn that there is still an option available for them to fly IFR into these airports.
 
AC No: 90-105A

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.
 
Okay, heres a new one (for me anyway): why would there be a designation "RNP APCH - GPS" on an ILS approach chart? It's a straight ILS/VOR approach with a hold at a DME fix on the missed. Is this simply saying that you can fly the approach using GPS (for all intents and purposes) to identify the DME fix? That doesn't really make sense to me because you can do that anyway (use GPS for DME distances).

I can't figure out what else they may be trying to say here. And I'm flying this approach with a WAAS GPS if that makes a difference.
 

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mryan75 said:
Okay, heres a new one (for me anyway): why would there be a designation "RNP APCH - GPS" on an ILS approach chart? It's a straight ILS/VOR approach with a hold at a DME fix on the missed. Is this simply saying that you can fly the approach using GPS (for all intents and purposes) to identify the DME fix? That doesn't really make sense to me because you can do that anyway (use GPS for DME distances).

I can't figure out what else they may be trying to say here. And I'm flying this approach with a WAAS GPS if that makes a difference.
Click to expand...
The Missed Approach Fix is also an Intersection. The Approach has no connection to the Enroute Structure. BOLTZ is not on an Airway and there are no Terminal Routes. You often see Radar Required on Approaches like this. It's needed to get 'established' on the Approach. In this case, GPS is used to get established.
 
luvflyin said:
The Missed Approach Fix is also an Intersection. The Approach has no connection to the Enroute Structure. BOLTZ is not on an Airway and there are no Terminal Routes. You often see Radar Required on Approaches like this. It's needed to get 'established' on the Approach. In this case, GPS is used to get established.
Click to expand...
Makes perfect sense, many thanks for the explanation!
 
Craigd31 said:
FAA has started publishing some approaches with RF legs that are not designated as RNP AR procedures. And, with some limitations, pilots who fly aircraft equipped with GTN-series avionics should be able to fly the RF legs used as transitions/feeder routes on those approaches.
Click to expand...
3 to be exact. And, that was several years ago.
 
luvflyin said:
The Missed Approach Fix is also an Intersection. The Approach has no connection to the Enroute Structure. BOLTZ is not on an Airway and there are no Terminal Routes. You often see Radar Required on Approaches like this. It's needed to get 'established' on the Approach. In this case, GPS is used to get established.
Click to expand...

Also note the TAA on an ILS plate!
 
Small correction, non-WAAS IFR GPS is 5 (not 2) ->1->0.3 etc. for (enroute, terminal, and approach mode).
 
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luvflyin said:
The Missed Approach Fix is also an Intersection. The Approach has no connection to the Enroute Structure. BOLTZ is not on an Airway and there are no Terminal Routes. You often see Radar Required on Approaches like this. It's needed to get 'established' on the Approach. In this case, GPS is used to get established.
Click to expand...

Correct. I will add that this situation has been happening more often recently due to the reduction in the VOR network. Many times, there just isn't an appropriate connection available to the enroute structure any more for non-GPS aircraft. Specifically here, if you look at the Low Enroute chart, there are no V-airways that run nearby, they're all T's. There is the UTICA TACAN, which I assume used to be a VOR, which was probably used in the past - but now that the VOR portion has been decommissioned, that doesn't leave any real options for getting into this procedure without using GPS. So a TAA was established.

Remember that approach charts only tell half the story. The other half is how you get TO the approach, and that is told on the enroute charts.

Also, the wording on how this information is presented (the "RNP APCH - GPS" on this chart) has been in flux for the last few years. Several different methods have been tried. It's all pretty new and growing pains are being resolved.

Now, you may ask, "but if I have to have a GPS to fly the ILS procedure, why don't I just fly the RNAV (GPS) approach, which has identical minimums with LPV". And that's a reasonable question. But there are operators out there that are not equipped or approved for LPV minimums, though they have enroute GPS.
 
Yes, BOLTZ used to be defined by the intersection of a radial from the nearby UCA VOR and the localizer course. And UCA was on defined airways. The VOR was very recently decommisioned. In the NE US, IFR navigation via VOR and the Victor airways system is getting more and more sparse. Several other regional VORs have been decommissioned (e.g., ITH, UCA), out of service permanently (ULW) or will be shortly shut down (GGT). I see GGT has a GPS waypoint, GTOWN already placed in anticipation.
 
RussR said:
Correct. I will add that this situation has been happening more often recently due to the reduction in the VOR network. Many times, there just isn't an appropriate connection available to the enroute structure any more for non-GPS aircraft. Specifically here, if you look at the Low Enroute chart, there are no V-airways that run nearby, they're all T's. There is the UTICA TACAN, which I assume used to be a VOR, which was probably used in the past - but now that the VOR portion has been decommissioned, that doesn't leave any real options for getting into this procedure without using GPS. So a TAA was established.

Remember that approach charts only tell half the story. The other half is how you get TO the approach, and that is told on the enroute charts.

Also, the wording on how this information is presented (the "RNP APCH - GPS" on this chart) has been in flux for the last few years. Several different methods have been tried. It's all pretty new and growing pains are being resolved.

Now, you may ask, "but if I have to have a GPS to fly the ILS procedure, why don't I just fly the RNAV (GPS) approach, which has identical minimums with LPV". And that's a reasonable question. But there are operators out there that are not equipped or approved for LPV minimums, though they have enroute GPS.
Click to expand...
Any specific reason it doesn’t say GPS or Radar? Is Radar required being phased out as a means to get established?
 
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chemgeek said:
Yes, BOLTZ used to be defined by the intersection of a radial from the nearby UCA VOR and the localizer course. And UCA was on defined airways. The VOR was very recently decommisioned. In the NE US, IFR navigation via VOR and the Victor airways system is getting more and more sparse. Several other regional VORs have been decommissioned (e.g., ITH, UCA), out of service permanently (ULW) or will be shortly shut down (GGT). I see GGT has a GPS waypoint, GTOWN already placed in anticipation.
Click to expand...
ITH is already a stand-alone DME. Some of those others may become so also.
 
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