The Runway Environment in the RNAV Era

As of January 30, 2020, the FAA had published 4,048 RNAV (GPS) approaches with LPV (localizer performance with vertical guidance) minimums at 1,954 airports; 1,186 of those airports are not served by an ILS. The number of LPV-capable procedures is almost three times the 1,550 approaches with Category I ILS minimums, and 2,838 of the procedures with LPV minimums serve runways without an ILS,

For the latest totals, visit the Instrument Flight Procedures (IFP) Inventory Summary and Satellite Navigation — GPS/WAAS Approaches pages at the the FAA website.

FAA.gov

This capability to fly ILS-like procedures to thousands of runways at small-town and rural airports is a boon to IFR pilots. But you must carefully prepare to fly approaches to runways that don’t have the ground infrastructure associated with an ILS–most importantly an approach lighting system and accessories such centerline and touchdown zone lighting. And keep in mind that a non-ILS runway may not be as a long as you’re accustomed to–the minimum length for a runway served by an approach with LPV minimums is just 3200 ft. (more details here).

For more information about GPS-based approaches, see Required Navigation Performance (RNP) Approaches (APCH) .

FAA.gov

For example, here’s video of the final approach segment of the RNAV (GPS) RWY 16 procedure at Chehalis, WA (KCLS) during a night approach.

As the video shows, the runway can be hard to spot. It has REILs and a PAPI, but it’s in a dark area near a river. And you must remember to activate the lights by clicking the transmit button on the CTAF as you approach the airport. (The camera makes the scene look a little darker than it really was to human eyes–but you get the idea.)

Chehalis (KCLS) airport

That approach has an LPV decision altitude of 476 ft MSL (300 ft. AGL). The visibility requirement is 1 sm. That’s not much greater than the 200 ft DA and 1/2 sm visibility for a typical Category 1 ILS. But the environment is vastly different than that presented by an ILS runway with its bright lights and other big-city features.

Here’s an overview of the approach lighting systems associated with ILS procedures.

Instrument Procedures Handbook:
Figure 9-36. Precision and nonprecision ALS configuration.

Contrast the view at KCLS with the scene at Boeing Field (KBFI) in Seattle during the final stages of an ILS approach.

ILS RWY 14R at Boeing Field (KBFI)

Here’s an approach to runway 20 at Bremerton, WA (KPWT). KPWT is a non-towered airport, but runway 20 is served by an ILS approach, which includes an ALS.

KPWT
RNAV RWY 20 approach at KPWT

So, regardless of the type of approach you’re flying, make sure you review and prepare for the runway environment that you’ll encounter when you break out of the clouds and go visual. It’s especially important to know which of the visual cues described by 14 CFR §91.175 Takeoff and landing under IFR will be available.

4 Responses to The Runway Environment in the RNAV Era

  1. Chris Bowman says:

    Hi Bruce — I have not been able to find an answer to a GTN 750 LPV approach question from Garmin. I also showed this to the folks at Pacific Coast Avionics at the KUAO (stopped by in my car), and they were unaware of it and had no idea. So I thought I would run it by you. Hopefully you can refer me to a previous post of yours.

    Using the GTN 750, what is the altitude waypoint on a loaded approach on the flight plan page that is the first waypoint after the “RWxx map” waypoint on an LPV approach?

    For example: For KFWQ RNAV 26 it is at or above 1500 FT which corresponds to the DA. For KAFJ RNAV 27 it is at or above 1700 FT which corresponds to the first leg of the missed approach. For KMGW RNAV Z 18 it is at or above 1644 FT which is 400 FT above the airport elevation.

    Garmin indicated that this was info supplied by Jeppesen and I should contact them. I have not contacted Jeppesen yet. It is disconcerting to not know what a waypoint is and what the flight director uses it for.

    I just bought your GTN 750 manual from Pilot Workshops and subscribed to that site. Looking forward to some good info from them.

    Thanks — Chris Bowman

    On Thu, Jan 23, 2020 at 5:04 PM BruceAir, LLC (bruceair.com) wrote:

    > bruceair posted: ” At the end of 2019, the FAA had published 4,503 RNAV > (GPS) approaches with LPV (localizer performance with vertical guidance) > minimums. That is almost three times the 1,550 approaches with Category I > ILS minimums, and 2,838 of the procedures with LPV min” >

    • bruceair says:

      These altitudes are the beginning of “course to altitude legs” (CA legs). For more details about leg types coded in databases, see Chapter 6 of the Instrument Procedures Handbook. The fixes are in the ARINC 424 specification and are intended to help ensure that you don’t turn early when flying a missed approach segment. The fixes aren’t charted, but the Garmin GTN series supports these legs; older units from Garmin and other manufacturers may not use or display these data. If a missed approach includes a turn, the altitude shown in the flight plan list in, say, a GTN, will be at least 400 AGL. That corresponds to the requirement for no turns below 400 AGL on an instrument departure procedure (again, see the IPH, AIM, and other references). The altitude is just another reminder not to turn too soon when you go missed, and you won’t see course guidance on a CDI connected to a GTN (or similar box) that has an altitude input until you reach at least the altitude shown at the fix.

      For more information about leg types, see also Avoiding Confusion when Flying GPS Legs: https://bruceair.wordpress.com/2016/03/06/avoiding-confusion-when-flying-gps-legs/

      • Chris Bowman says:

        Thank you for clearing this up for me. Had to think about it for awhile but the fixes that I’ve been looking at all seem to be consistent with the turn vs straight out criteria. Some are lower than 400′ AGL but they are each part of an approach with a straight out first leg of the missed. In this case I guess the flight directer will allow gps steering by the autopilot on the straight out leg at lower altitudes depending on the runway environment (say even down to the 200′ minimum missed approach AP engage altitude). This altitude fix on the GTN 750 is 1500′ for KFWQ which corresponds to 272′ AGL. The first missed leg is climb 3000′ direct to DESCA which happens to be a fix that is straight out on the runway heading/final approach heading. I assume the position of DESCA was chosen, in part, to be straight out and at a distance to allow a reasonable climb rate to 3000′ since the surrounding terrain would allow for a straight out initial missed leg.

  2. Chris Bowman says:

    Just reviewed your scenario at “Pilot Workshops” …”Exception out of Fullerton”. Very informative and touches on this topic of “course to altitude legs” for the Fullerton HAWWC THREE SID.

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