Z, Y, X in Approach Titles

I’ve recently noticed questions popping up about the letters Z, Y, X appearing in the titles of instrument approach procedures. Titles that include “-A,” “-B,” or “-C” are familiar–they designate procedures that have only circle-to-land minimums, such as the VOR-A at Olympia, WA (KOLM). But letters from the other end of the alphabet puzzle many pilots.


For example:

The most detailed explanation of this naming convention is in “Straight-In Procedures” in Chapter 4 of the Instrument Procedures Handbook (updated in October 2017):

When two or more straight-in approaches with the same type of guidance exist for a runway, a letter suffix is added to the title of the approach so that it can be more easily identified. These approach charts start with the letter Z and continue in reverse alphabetical order. For example, consider the (RNAV) (GPS) Z RWY 13C and RNAV (RNP) Y RWY 13C approaches at Chicago Midway International Airport…Although these two approaches can be flown with a global positioning system (GPS) to the same runway, they are significantly different (e.g., one is a Required Navigation Performance (RNP) Authorization Required (AR) … one has circling minimums and the other does not; the minimums are different; and the missed approaches are not the same). The approach procedure labeled Z has lower landing minimums than Y…

In this example, the LNAV MDA for the RNAV (GPS) Z RWY 13C has the lowest minimums of either approach due to the differences in the final approach required obstacle clearance (ROC) evaluation. This convention also eliminates any confusion with approach procedures labeled A and B, where only circling minimums are published. The designation of two area navigation (RNAV) procedures to the same runway can occur when it is desirable to accommodate panel mounted GPS receivers and flight management systems (FMSs), both with and without vertical navigation (VNAV). It is also important to note that only one of each type of approach for a runway, including ILS, VHF omnidirectional range (VOR), and non-directional beacon (NDB) can be coded into a database. (4-9)

FAA Order 8260.3C (i.e., TERPS) includes additional information:

Alphabetical suffix. When more than one procedure to the same runway uses the same type of navigation system for lateral guidance within the final approach segment, differentiate each procedure by adding a non-repeating alphabetical suffix using the letters “S” through “Z.” Suffixes are normally assigned in reverse order starting with “Z,” but may be assigned as needed to meet operational needs [for example, all RNAV (RNP) approaches at an airport assigned “Z” suffix, all RNAV (GPS) approaches assigned “Y” suffix, etc.]. (1-9)

As noted above, approaches to the same runway can be labeled Z, Y, or X… for several reasons.

For example, consider the ILS RWY 27 at KYKM, which is published as both the ILS Y RWY 27 and ILS Z RWY 27.

The Z version requires a non-standard climb gradient of 250 ft/nm on the missed approach procedure (see the note in the plan view), but it provides a DA of 1268 (200 AGL) with RVR 2400.



The DA on the Y version of the approach is 1725 (657 AGL) with visibility of 2 sm. So you can go much lower and to the equivalent of 1/2 sm visibility if you can achieve the steeper climb gradient on the miss.

There are two versions of the ILS RWY 16R–but for a different reason–at Snohomish County–Paine Field (KPAE) north of Seattle.

Both procedures offer the same basic DA and visibility minimums (although the Z version allows a reduction to RVR 1800 with a flight director, autopilot or HUD). But the FAF (ITIPE) for the Y edition is 4.4 nm from the PAE VOR.


The Z version, which also has published minimums for category C and D aircraft, has a FAF (JUGBA) at 7.6 nm from the VOR.


If you’re flying a typical light GA aircraft, the Y version is much more efficient, while the Z version is better suited to jets (like the shiny new Boeings emerging from the factory at KPAE) that need more room to get established on final.

As pointed out earlier, Z, Y, and X versions of the same basic procedure may require different equipment or missed approach segments. For example, using your favorite chart-viewing app, compare the ILS Y or LOC RWY 20 and the ILS Z or LOC/DME RWY 20 at Walla Walla, WA (KALW).

The key to flying such approaches is a careful review of the entire procedure, including notes lurking on the chart. When you contact ATC, it’s also important to request the specific procedure–including the letter–that you want to fly.

And, if you’re using an IFR-approved GPS–even for situational awareness or to act as a substitute for DME or ADF  when flying a ground-based approach– ensure that you load the correct procedure and verify the key fixes before you begin flying the approach.


RVR 1800 with AP, FD, or HUD

On May 30, 2017, FAA updated Order 8400.13D to allow “CAT I approaches with a DH of 200 feet and visibility minimums of RVR 1800 [a reduction from the typical 2400 RVR value] at runways with reduced lighting, using an aircraft flight director (FD) or autopilot (AP) with an approach coupler or head-up display (HUD) to DA.”

This change applies to ILS and RNAV (GPS) approaches with LPV minimums. (GBAS approaches are also included, but those procedures are, at present, rare.)

The policy update was announced in the summer 2017 edition of SatNav News.

Here’s an example of the RVR 1800 minimums on the chart for the ILS or LOC Rwy 20 at KALW (Walla Walla, WA).

KALW-ILS-RWY 20-full

This typical category 1 ILS approach has an RVR of 2400 and a DA of 200 ft (1394 MSL).

KALW-ILS-RWY 20-mins
But as the notes for the procedure explain, the # symbol next to the S-ILS 20 minimums means that RVR 1800 is authorized with use of a flight director (FD) or autopilot (AP) or HUD to the DA.

KALW-ILS-RWY 20-notes
FAA Order 8400.13D adds the following information about reducing CAT 1 minimums to RVR 1800:

  • To be eligible for CAT I approaches to RVR 1800, runways must have or be qualified for a Title 14 of the Code of Federal Regulations (14 CFR) part 97 Standard Instrument Approach Procedure (SIAP).
  • Runways must have or be qualified for CAT I DH of 200 feet or less and visibility minimum of not more than 2400 RVR.
  • The runway must have a declared landing distance of 5000 feet or greater.
  • The runway also must have a simplified short approach lighting system with runway alignment indicator lights (SSALR), medium intensity approach lighting system with runway alignment indicator lights (MALSR), or approach lighting with sequenced flashing lights (ALSF-1/ALSF-2)
  • HIRL
  • TDZ sensor of an RVR reporting system.

The order adds that:

Any existing part 97 CAT I SIAP which did not qualify for 1800 RVR due to the absence of TDZ or RCL lighting can be amended to include 1800 RVR visibility.

When 1800 RVR operations are authorized, FAA will update the approach chart. If RVR 1800 minimums are authorized before a chart is updated, a NOTAM will be issued which authorizes RVR 1800. CAT I operations to RVR 1800 will be added to existing CAT I SIAPS in accordance with a schedule established by the Regional Airspace and Procedures Team.

The ILS OR LOC/DME RWY 21R at KPSC (Pasco, WA) is another example of RVR 1800 minimums authorized for an ILS.


The S-ILS 21R minimums line includes two asterisks that point to the notes section, which authorizes RVR 1800 with use of a FD, or AP, or HUD to DA.

The RNAV (GPS) Y RWY 21R at KPSC, updated in August 2017, shows the RVR 1800 minimums applied to an RNAV approach with LPV minimums. On this chart, the # note reference appears next to DA.


New Edition of Instrument Procedures Handbook

FAA has published a new edition of the Instrument Procedures Handbook (FAA-H-8083-16B). You can download a PDF of the IPH at the FAA website here.

The IPH is a complement to the Instrument Flying Handbook (FAA-H-8081-15B), available for download here.

A summary of changes in the new edition of the IPH is available as a PDF in my Aviation Documents folder, here.


An ILS that Requires GPS

You can still fly IFR in the U.S. without an IFR-approved GNSS (i.e., GPS), but being “slant G” (/G in the soon-to-be obsolete FAA domestic flight plan format) increasingly offers advantages, even if you fly only conventional procedures based on ground navaids. And sometimes an IFR-approved GNSS is required to fly even an ILS.

Consider the ILS Z OR LOC Z RWY 16R approach at Reno/Tahoe International Airport (KRNO). This procedure is not an Authorization Required approach–RNP doesn’t appear in the title, and you won’t find that restrictive note on the chart. (For more information about RNP procedures, see RNP Procedures and Typical Part 91 Pilots.)


But the equipment required notes for this ILS approach include “RNAV-1 GPS required.”

A review of the plan view and missed approach track show why GPS is necessary to fly this procedure.


First, you need GPS to fly transitions from most of initial fixes, which are RNAV waypoints marked by a star symbol.


Only LIBGE, directly north of the runway, is a non-RNAV IAF.

For example, HOBOA, KLOCK, BELBE, and WINRZ are all RNAV waypoints that serve as IAFs or IFs. Now, NORCAL Approach might provide vectors to the final approach course, but if you want to fly this procedure you should be prepared for a clearance direct to one of those fixes (see Avoiding the Vectors-to-Final Scramble).

Note also that entire missed approach track requires use of GNSS.

Two of the transitions are of special note. The “arcs” that begin at ZONBI and SLABS are radius-to-fix (RF) legs that are part of the transitions that begin at HOBOA and KLOCK. Each of those fixes is distinguished by the notes “RNP-1 GPS REQD” and “RF REQD.”

The first note means that your GPS must meet the RNP 1 standard, which is used for terminal procedures such as SIDs and STARs, the initial phases of approaches, and missed-approach segments. (For more information about RNP, see RNP Procedures and Typical Part 91 Pilots.)

Until recently, RF legs were included only in Authorization Required (AR) procedures. But as I explained in Garmin GTN Avionics and RF Legs, certain RF legs are now available if you have an appropriate GNSS navigator, updated system software, an electronic HSI, and other equipment. Some limitations on flying such RFs also apply, as described in that earlier post.

Suppose that you choose the less intimidating ILS X or LOC X RWY 16R to the same runway. A review of the notes and the plan view shows that even this conventional-looking ILS also requires RNAV 1 GPS, both to fly the transition from WINRZ and the missed approach track.



Clearances to GNSS Equipped Aircraft Below the MEA

FAA recently updated Air Traffic Control (JO 7110.65W) to allow IFR clearances to GNSS (i.e., GPS) equipped aircraft on airways below the published minimum en route altitude.

N JO 7110.741, published on September 25, 2017 (now incorporated in Air Traffic Control paragraph 4-5-6), explained that:

This notice…allow[s] IFR certified Global Navigation Satellite System (GNSS) equipped aircraft to be cleared below published Minimum En Route Altitudes (MEA)…

The notice explained that:

MEAs are based in part on ground-based navigational aid reception. The advent of satellite technology provides the opportunity for lower minimum altitudes along certain airways, allowing more altitudes to be usable for more aircraft. This change will facilitate IFR certified GNSS equipped aircraft to fly below published MEAs, but no lower than Minimum Obstruction Clearance Altitudes, Minimum IFR Altitudes, or Minimum Vectoring Altitudes, regardless of radar coverage. This would apply to all applicable airways, rather than being limited to those published with GNSS MEA minimums.

Note that the rule (in 14 CFR §91.177 Minimum altitudes for IFR operations) about flying at the MOCA  when you are using VORs still applies:

For aircraft using VOR, VORTAC or TACAN for navigation, this [i.e., flying at the MOCA] applies only within 22 miles of that NAVAID.

The low-altitude en route chart below points out examples of MEAs and MOCAs. (Click here to see the chart at SkyVector.com.)


For example, along a segment of V187 between MOG and MSO, the MEA is 13000. The MOCA is 9900. There is no published GPS MEA (which would appear in blue with a G appended to the altitude). But if you are flying with an IFR-approved GPS, ATC could clear you to 9900, if, for example, you encountered ice.

Similarly, along V120 east of MLP, the MEA is 13000 and the MOCA is 9600, potentially giving you more than 3000 feet to work with if necessary.

Note, however, that not all airway segments have published MOCAs. For example, the only published IFR altitude between PUW and MLP is the MEA of 9100. You still might be cleared below that MEA if ATC has a lower minimum IFR altitudes or minimum vectoring altitudes available in that area, but those altitudes are not typically published on charts that pilots use.* You would just ask for a lower altitude, and the controller could clear you to the appropriate MVA or MIA.

The updated FAA handbook specifically notes that controllers may clear you to an MVA or MIA, but they must also issue lost communications instructions:

(a) In the absence of a published MOCA, assign altitudes at or above the MVA or MIA along the route of flight, and

(b) Lost communications instructions are issued.

*You can download MVA and MIA charts as PDFs from the FAA website, here. But at present, these charts are not available in a format that allows for easy integration with apps that pilots typically use or straightforward comparison with other aviation charts.

FAA Proposes Cuts to Circling Approach Minimums

The FAA has announced the early stages of plan to evaluate and then cut the number of circling minimums published for instrument approaches. According to a notice in the Federal Register on October 6, 2017:

In early 2015, the FAA requested the RTCA’s Tactical Operations Committee (TOC) with providing feedback and recommendations on criteria and processes for cancelling instrument flight procedures. Among the many recommendations provided by the TOC were criteria on how to identify circling procedures that would qualify as candidates for cancellation. As of the beginning of 2017, there are approximately 12,000 IAPs in publication, and there were nearly 10,600 circling lines of minima. Circling procedures account for approximately one-third of all lines of minima in the NAS.

In its continued effort to right-size the NAS through optimization and elimination of redundant and unnecessary IAPs, the FAA proposes the following criteria to guide the identification and selection of appropriate circling procedures to be considered for cancellation…

Proposed Policy

All circling procedures will continue to be reviewed through the established IAP periodic review process.As part of that review process, the FAA is proposing that each circling procedure would be evaluated against the following questions:

—Is this the only IAP at the airport?

—Is this procedure a designated MON airport procedure?

—If multiple IAPs serve a single runway end, is this the lowest circling minima for that runway? Note: If the RNAV circling minima is not the lowest, but is within 50′ of the lowest, the FAA would give the RNAV preference.

—Would cancellation result in removal of circling minima from all conventional NAVAID procedures at an airport? Note: If circling minima exists for multiple Conventional NAVAID procedures, preference would be to retain ILS circling minima.

—Would cancellation result in all circling minima being removed from all airports within 20 NMs?

—Will removal eliminate lowest landing minima to an individual runway?

The following questions are applicable only to circling-only procedures:

—Does this circling-only procedure exist because of high terrain or an obstacle that makes a straight-in procedure unfeasible or which would result in the straight-in minimums being higher than the circling minima?

—Is this circling-only procedure (1) at an airport where not all runway ends have a straight-in IAP, and (2) does it have a Final Approach Course not aligned within 45 degrees of a runway which has a straight-in IAP?

Further consideration for cancellation under this policy would be terminated if any of the aforementioned questions are answered in the affirmative. If all questions are answered in the negative, the procedure would be processed as described in the following paragraph.

FAA Changing Notes on Instrument Charts

The FAA is gradually changing notes on instrument procedure charts (SIDs, STARs, and approaches) to consolidate and clarify equipment required and PBN-related information.

AOPA has published a detailed summary with background on the changes here.

The AOPA summary also includes tables that can help pilots who use Garmin equipment understand the capabilities of the avionics installed in their aircraft.