Tuesday, May 15, 2018

Goodbye /DME, Hello Equipment Requirements Notes!

(This article is a companion post to episode 178 of the Stuck Mic AvCast)

Big news on the instrument approach charting front! In the near future you will not be seeing any more VOR/DME or LOC/DME or anything /DME procedures in the U.S. In fact, it's already started, but beginning with the 5/24/18 chart cycle, even more changes will take place. These changes could all be grouped under the heading "Equipment Requirements Notes".

Let's take it one thing at a time.


For as long as I can remember, if you had a VOR/DME or LOC/DME procedure, the /DME in the name signified that you needed to have a DME receiver in order to identify the Final Approach Fix, as in this example.  We may or may not need it elsewhere, but we knew we needed it to identify the FAF, in this case, NUCIK, CNU 12.9 DME.

FAA Order 8260.19H no longer provides for the "/DME" (or /anything else) in the procedure name, so these are being gradually removed. This means that the example VOR/DME RWY 17 above will eventually be simply the VOR RWY 17. But how will we know it requires DME, if it's not in the name? Simply, this removal of /DME from the name is part of a larger move to consolidate all the various equipment requirements notes into one location on the chart, as I'll discuss below.

Other equipment notes

We are also used to notes showing up in either the notes box or in the plan view.

Sometimes this would lead to confusing situations, like this:

Wait, do I need to have ATC radar coverage, or DME, or both?

These notes have always been a bit confusing, as the positioning of the notes affected its meaning. A note such as "DME Required" in the notes box meant that DME was required on the missed approach. If that same note was positioned in the planview, however, it meant that it applied to procedure entry from an IAF. From the AIM 5-4-5a3(b):

This placement criteria is more than a little confusing, however, so the best rule is to always review each approach to determine how you will identify each fix, starting at the appropriate IAF. We're getting out of practice on that with the prevalence of GPS substitution, so it's extra important to take some time to chair-fly the approach when we don't have an IFR GPS on board.

However, that is all changing (gradually).

Equipment Requirements Notes

The FAA Order 8260.19H, which is the FAA document guiding the documentation of procedures, adds a new box to the approach charts - the "Equipment Requirements Notes" box. This box, located near the top of the chart, will spell out what additional equipment is required to the fly the approach, but more importantly, where that additional equipment is needed.

Some examples from the 19H are:

"DME required for procedure entry"

"DME required for LOC only"

"DME or RADAR required to define GIGGS"

Procedures with this new box are showing up starting in the 5/24/18 publication cycle. However, like any change of this nature, it will take years for the updates to make it through all the approach charts in the U.S. inventory.

Here are some actual examples of 5/24/18 charts with those new notes.

First, a VOR/DME that is now going to be a VOR approach with DME required:



More examples:

On this one, there is no valid fix makeup for DACCA (no DME source, and the angle for the FKL VOR radial would be too obtuse), so RADAR is required. Once you get past DACCA, though, no special equipment or RADAR is required.

Here you need either an ADF to fly the procedure turn based on the VEELS LOM, or a DME receiver to fly the arcs. Once you're established on that 131 course, though, normal ILS, VOR and marker beacon receivers can get you all the way to the missed approach holding fix:

Of course, if you have an IFR-certified GPS receiver, you can usually use it to substitute for these equipment requirements (following the appropriate AIM and AC 90-108 guidance). But putting "or GPS" in every single one of these notes would be a bit redundant...

PBN Equipment Notes

So far I've discussed only conventional, non-RNAV approaches. But don't worry, RNAV approaches get similar changes as well, there just aren't as many different possibilities. However, the changes introduce some terms that will be new to many people.

Very simply, there is a broad concept called "Performance-Based Navigation", or "PBN". PBN systems not only have an accuracy requirement, but among other things also have an alerting requirement for when it calculates it's not able to provide that accuracy. 

Think about a VOR - it has an accuracy requirement (30-day VOR checks), but if the accuracy right at the moment you're using it is degraded for any reason (signal problems, internal equipment errors, who knows), it has no way of determining it and telling you. A "NAV" flag on the VOR will indicate that the VOR transmitter itself is not working, but there's no way for the unit to check itself or the accuracy of the transmitter.

A PBN system, however, has to be able to tell you if the accuracy is degraded. The most popular type of PBN system in GA is, of course, an IFR-approved GPS receiver. But there are other systems - DME/DME/IRU being one of them. The new PBN requirements introduce levels of performance specifications that the aircraft equipment must meet to fly various procedures.

Different types of procedures require different levels of performance. The Required Navigation Performance specification is abbreviated "RNP". Rather than go into too much more discussion here, the AIM paragraph 1-2-2 has the details.

While PBN and RNP concepts can be very confusing, allow me to simplify - most light GA aircraft with a IFR-approach approved GPS receiver meet the "RNP APCH" NavSpec.

The term RNP has actually been around longer than we realize. We're all familiar with the DME/DME RNP-0.3 NA note, it has been on every RNAV (GPS) approach chart for a long time:

Most of us have been glossing over it during an approach briefing because it doesn't mean anything to the majority of light-airplane GA pilots whose airplanes have never had a DME/DME RNAV system. This note is going away. 

What will be replacing it is a note saying "RNP APCH":

This makes effectively no difference to the vast majority of GA pilots because as mentioned above, most popular IFR GPS installations in light GA aircraft meet the requirements for "RNP APCH". But seeing it on the chart could confuse some to think it's talking about RNAV (RNP) approaches, which are still only for airplanes that have a higher level of equipment and for aircrews that have received special training.

These will still be named RNAV (RNP) in the title, but will have the equipment note "RNP AR APCH" (AR for Authorization Required), as in the example below. (Note that this example has the additional requirement that the equipment has to be capable of flying Radius-to-Fix legs (RF required), since all routes into the procedure require such a leg type.) 


Hopefully, these new notes and placement will make the charts a bit easier to understand, although there is always a learning curve with anything like this.

Garmin has published a list of their equipment and RNP levels each one meets:
(Near the bottom, titled Garmin Flight Plan Information Excel file)

I could not find such a document from the other GA IFR GPS manufacturers, but will link to it if someone can point it out to me.

All of the above chart samples were obtained at the FAA's website, where you can download the actual charts 19 days before each pub day. Also, you can get advanced notice and draft versions of upcoming approaches, obstacle departures, SIDs and STARs from their IFP Information Gateway.

Actual charts obtained from: 

IFP Information Gateway: