A Challenging Approach

The RNAV (GPS) RWY 15 approach at Kingston-Ulster-Airport, NY (20N) is a great exercise for IFR pilots to practice in an ATD or flight simulation. And it’s a terrific starting point for scenarios that instrument instructors and evaluators can review with students and IFR candidates. (Thanks to Doug Stewart, one my colleagues in the IFR Mastery series at Pilot Workshops, for pointing me to this procedure.)

Flying this procedure requires preparation. It’s not a basic ILS or straight-in RNAV approach where the only significant deviations from “standard” are the altitudes and tracks along the final approach course. In fact, flying this approach in IMC or at night also requires study of the Chart Supplement, not just the procedure chart. Comparing the approach chart with the sectional and low-altitude IFR charts for the area also helps you understand some of the challenges associated with this procedure.

Planning for and flying an approach like this highlights an advantage of using EFB app like ForeFlight, Garmin Pilot, or FlyQ. Those tools make it easy to switch between IFR and VFR charts, review the Chart Supplement, and look up other important information, but only if you study those resources before takeoff.

For more information about planning for and flying IFR procedures, see Annotating IFR Charts, Briefing IFR Procedures, and An IFR Scenario for Practice in an ATD.

This RNAV approach has a bit everything to challenge an IFR pilot, including:

  • A series of (sometimes short) segments from the IAF to the missed approach point, each with a change of track.
  • LP and LNAV minimums to MDAs (and LP+V advisory vertical guidance if you have a WAAS navigator with the appropriate system software).
  • A steeper-than-normal (3.45 degrees) descent angle from the FAF to the MAP, if you follow advisory vertical guidance. That descent path is shown on Jeppesen charts, but not on the FAA chart.
  • Two crossing restrictions inside the FAF that you must observe even if you do follow advisory guidance.
  • Obstacles in the visual segment.
  • A 29.15-degree offset from the final approach to the threshold (barely inside the 30-degree limit for straight-in minimums).
  • A short runway at 3100 ft., but with a displaced threshold that leaves only 2775 ft. available for landing.
  • An arrival holding pattern anchored at ILGEZ , not to be confused with the missed-approach hold shown at JOEYL (see AIM 5-4-9, cited in part below) or with a holding pattern used as a course reversal (i.e., a HILPT).
  • Other subtleties such as an off-airport altimeter source (no AWOS) and one frequency for the CTAF, another for activating the runway lights and PAPIs.
  • Important information related to this approach that is available in the Chart Supplement entry for N20, but which isn’t published on the chart.

Kingston-Ulster-Airport lies along the Hudson River in upstate New York, with rising terrain west of the runway. The sectional chart shows why bends are required to get you to the runway from the north and why the final approach segment isn’t lined up with the pavement.

The low-altitude IFR en route chart for the area also offers puzzles to ponder, such as an airway segment that is unusable, but only if you’re flying V292 using VORs, not T295, the overlapping T-route that runs east-west, north of the airport. In fact, the area around 20N is crisscrossed by T-routes, which in many cases have replaced or supplanted VOR-based airways, especially where VORs have been decommissioned.

A Detailed Review

Let’s take a closer at this interesting approach, preferably during preflight planning, not while descending from cruise.

The procedure title indicates that this approach offers straight-in minimums (the title includes the runway number; it isn’t RNAV (GPS) – A or – B). But as we’ve seen, this approach barely meets the alignment criterion for straight-in minimums.

The notes at the top of the chart, which often include information that isn’t relevant to pilots of light, piston-powered airplanes, warrant special attention here. For example, the runway length available for landing–2775 ft.–doesn’t match the the 3100 ft. shown on the inset airport diagram, a detail that’s easy to miss if you don’t notice the displaced threshold symbols.

You need to consider how that short runway might affect the speed you’ll fly on final. For example, I fly most approaches in my A36 Bonanza at 110 KIAS, but when approaching a runway less than 4000-5000 feet long, I plan to fly final at 90 KIAS, which is just 10 knots above the 80 knot minimum speed for engaging the GFC 600 autopilot in my panel, should I choose to use it.

The minimum runway lengths associated with various approach types are described in AC 150/5300; more information at Update on WAAS Approaches from FAA.

The notes also reveal that the airport has non-standard takeoff minimums, often a hint about nearby terrain, and that 20N can’t be filed as an alternate, probably because it doesn’t have on-site weather reporting.

Another important note specifies that the primary source for setting the altimeter is Hudson (KPOU), 22 nm south. That detail requires additional attention when you set up and then brief the approach.

The frequency blocks include an oddity: 122.8 for the CTAF, but a different frequency, 123.3, to activate the pilot controlled lighting at this nontowered airport.

The plan view shows an arrival hold at ILGEZ, depicted with thin lines. Arrival holds aren’t common. When reviewing holds on charts, it’s important to distinguish between arrival holds and their cousins: holds in lieu of a procedure turn (HILPT), missed approach holds, and holds shown at alternate missed approach holding points.

Note: Some approach charts have an arrival holding pattern depicted at the IAF using a “thin line” holding symbol. It is charted where holding is frequently required prior to starting the approach procedure so that detailed holding instructions are not required. The arrival holding pattern is not authorized unless assigned by Air Traffic Control. Holding at the same fix may also be depicted on the en route chart…. (AIM 5−4−9. Procedure Turn and Hold−in−lieu of Procedure Turn)

As the AIM notes, flying an arrival hold requires ATC clearance. Unlike a HILPT, the hold at ILGEZ isn’t shown when you load the procedure in a GPS navigator such as a GTN 750. If ATC clears you fly the hold, perhaps to lose altitude before you begin the approach, you must build the hold in the box or use OBS mode.

The plan view shows four segments from the IAF at ILGEZ to the MAP at NEWMN, which is 0.7 nm from the threshold. The last segment, from FRLDI to NEWMN, is just 1.8 nm long. Flying these “final” segments involves 3 course changes. Landing requires another turn of almost 30 degrees at NEWMN to align with the runway centerline.

The profile view hints at more challenges, including a steep descent angle from IMIBE to FRLDI, which you must cross at or above 1080 ft. The FAA chart for this approach doesn’t show a visual descent angle (VDA), because, as a note points out, the visual segment isn’t clear of obstacles.

If there are obstacles in the visual segment that could cause an aircraft to destabilize the approach between MDA and touchdown, the profile will not show a VDA and will instead show a note that states “Visual Segment-Obstacles”. (Aeronautical Chart Users Guide)

Notice also that the heavy black line levels off before NEWMN, and that this approach does not include a visual descent point (VDP). These details are more clues that obstacles loom close to the runway. Fortunately, a check of the inset airport diagram reveals a PAPI available on the left side of the runway, definitely something to look for when (if) you break out.

For more information about VDP, see “Arrival Procedures” in the AIM:

The Visual Descent Point (VDP), identified by the symbol (V), is a defined point on the final approach course of a nonprecision straight−in approach procedure from which a stabilized visual descent from the MDA to the runway touchdown point may be commenced. The pilot should not descend below the MDA prior to reaching the VDP. The VDP will be identified by DME or RNAV along−track distance to the MAP. The VDP distance is based on the lowest MDA published on the IAP and harmonized with the angle of the visual glide slope indicator (VGSI) (if installed) or the procedure VDA (if no VGSI is installed). A VDP may not be published under certain circumstances which may result in a destabilized descent between the MDA and the runway touchdown point. Such circumstances include an obstacle penetrating the visual surface between the MDA and runway threshold, lack of distance measuring capability, or the procedure design prevents a VDP to be identified. (AIM

The leg from WOBVU to IMIBE is 7.5 nm long, allowing a comfortable descent from 3200 ft. to 1600 ft. But if you continue from IMIBE and level off at 1080 ft. to observe the restriction at FRLDI (which applies even if you’re following advisory vertical guidance), you have another 360 ft. to descend to the LP MDA of 720 ft. (280 ft. if you use the LNAV MDA of 800 ft.). And you have just 1.8 nm to make that last step-down descent.

As we’ve seen, the MAP is at NEWMN, located 0.7 nm from the threshold. That offset may be a surprise if you’re accustomed to RNAV approaches where the MAP coincides with the threshold. Moreover, the minimum visibility required for this approach is 1 sm. The runway doesn’t have approach lights, just the PAPI noted earlier, so you need to pick up the required visual references (see 14 CFR 91.175) before you reach NEWMN.

The PAPI is set at a 4.5 degree descent angle to cross the threshold at 50 ft. That important detail, by the way, is in the Chart Supplement entry for 20N, not on the approach chart.

The Chart Supplement also reveals that the PCL on 123.3 activates the PAPIs at both runway ends, and the runway lights, which are available from dusk to dawn. In addition, the PAPI serving runway 15 is unusable more than 5 degrees left and 8 degrees right of the final approach course. In other words, you won’t see–or shouldn’t follow–the PAPI visual guidance until you turn toward the runway at NEWMN. And another note–on the procedure chart–prohibits night landings on runway 15. Again, those close-in obstacles, probably unlit, loom.

All of the preceding details should make you consider carefully how you’ll configure the airplane and use an autopilot and flight director when you fly this approach. When will you extend the landing gear and flaps? What power settings will you use as the approach progresses through the various segments?

An autopilot could be a great help as you track all the course changes, but managing the descent, even if the autopilot offers VNAV and can follow glidepaths, requires a plan and close monitoring.

An approach like this also highlights the advantages of an electronic PFD and moving map. The following images, captured with the free Garmin PC Trainer Suite, show some of the key details discussed above.

When you load the approach in a WAAS navigator, LP+V minimums may be available. Note that LP+V indicates LP minimums to an MDA with advisory vertical guidance. LP+V is not the same as LPV, which provides approved vertical guidance to a DA. For more information, see Handy WAAS and RNAV (GPS) Approach Fact Sheets.

Note that the GTN 750 map doesn’t show the arrival hold at ILGEZ. If ATC clears you to fly that hold, you must set it up in your navigator. If you’re prepared, that’s easy to do in a GTN navigator. If you have an older GPS, you may have to use OBS mode to fly the arrival hold.

If you fly the arrival hold, you must manually resume sequencing (unsuspend/cancel OBS mode) to continue flying the approach.

At this point, your PFD should show LP+V if advisory vertical guidance is available.

As you continue inbound, you (or the autopilot) can follow the advisory vertical guidance to the MDA. But make sure you observe the crossing restrictions as you continue toward the missed approach point.

A PFD with a map also helps you anticipate the last turn to align with the runway.

I hope this approach helps you appreciate the need for thorough preflight planning, even if you use an EFB and have a panel that features advanced avionics. Those tools are terrific aids, especially when flying single-pilot IFR. But using them effectively requires preparation.

For more information about planning for and flying IFR procedures, see Annotating IFR Charts, Briefing IFR Procedures, and An IFR Scenario for Practice in an ATD.

3 thoughts on “A Challenging Approach”

  1. I’m always learning from your articles. Has there been a revision to the order in which types of approach minimums are listed, eg. LPV at the top then LMAV/ VNAV then LNAV. I was just reviewing a new revision of the RNAV(GPS) 35 approach at KCWC. The LNAV/VNAV with lower minimums is listed first followed by the LPV minimums. A good example of an approach where LPV minimums are not always the lowest.
    A similar situation exists at F49 (LNAV mins are less than LPV mins).

    Thanks for your writing.
    Stan

    1. The 8260-3 form for this procedure includes the following notes under Changes:

      5. UPDATED LPV HAT/DA ALL CATS FROM “250/1250” TO “299/1299” – NEW CONTROLLING OBSTACLE.
      6. UPDATED LPV VISIBILITY ALL CATS FROM “7/8” TO “1” – FAAO 8260.3D, TABLE 3-3-1

      12. UPDATED MINIMUMS, LISTED LNAV/VNAV WITH THE LOWEST HAT AS THE FIRST LINE OF MINIMA AND LPV AS A SECOND LINE OF MINIMA. – PER 8219H PARA 8-6-11C.

      Click to access TX_WICHITA%20FALLS_RG35_CWC.pdf

      The reference above to FAA Order 8219H appears to be a typo. The relevant citation seems to be from Order 8260I, paragraph 8-6-11 Minimums.:

      c. Minimums boxes. Enter straight-in minimums starting with the lowest HAT as the first (top) line of minima followed by the next lowest HAT as the second line of minima and so forth in sequential order followed by circling minimums. A maximum of six lines (maximum five lines where dual minimums are published) of any combination of authorized minima may be published on a single chart. Enter “NA” in the applicable box(s) when a specific aircraft category(s) is not authorized, except as noted in paragraph 8-6-11.h. Make no entry in the minima blocks when minimums are not authorized for all aircraft categories. Do not deny or cancel straight-in minimums in order to circumvent grant agreements that have been established under airport development programs. If criteria do not permit straight-in minimums, publish circling minimums only.

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