This video picks up after Seattle Approach cleared me to HOOME, an IAF for the RNAV (GPS) RWY 23 approach.
My avionics are capable of flying this procedure to LPV (localizer performance with vertical guidance) minimums. In other words, this RNAV (GPS) procedure offers approved vertical guidance–a GPS-derived glidepath. Flying to LPV minimums effectively uses the same techniques as flying an ILS.
Note, however, that this procedure includes two lines of LPV minimums. The decision altitude (DA) for the first line is 523 ft with a visibility requirement of 3/4 sm.
The second LPV line has higher minimums: 667 ft and 1-1/4 sm.
Why the difference? Note the # next to the DA in the first line. It leads you to a note in the description near the top of the chart:
#LPV missed approach requires minimum climb of 244 feet per NM to 1700.
To use the minimums of DA of 523 and 3/4 sm visibility, you must be able to climb at 244 feet per NM during the initial stages of the missed approach. That’s a slightly higher climb gradient than the standard 200 feet per NM.
Note that the climb requirement is for a climb gradient in feet per NM, not a rate of climb in feet per minute. To determine if your aicraft is capable of achieving the required climb gradient, you must check the Climb/Descent Table in the supplement to the Terminal Procedures Publication or calculate the climb gradient that corresponds to your groundspeed and rate of climb when you fly the missed approach portion of the procedure.
In my A36, climbing out at 110 KIAS, with a groundspeed of about 100 KIAS given the headwind component, and an initial (conservative) climb rate of about 600 fpm, my climb gradient is about 300 ft/nm, so I can use the lower DA and visibility when flying this approach.
You can find more videos from this IFR flight at my YouTube channel, BruceAirFlying.
The FAA continues to publish more GPS-based instrument procedures. The latest inventory shows that as of February 6, 2014, there are 13,134 RNAV (GPS) approaches available for general use in the U.S. National Airspace System. (That number doesn’t include the RNP authorization-required procedures available only to pilots and aircraft that meet the requirements of AC 90-101A. More about RNP and AR procedures here.)
By comparison, there are 5,794 ILS, LOC, NDB, and VOR approaches (again, not counting CAT II, CAT III, and other procedures that require special training, equipment, and authorizations).
RNAV (GPS) Procedures
GPS (Stand – Alone)
Here’s a pie chart that shows the relative shares of different types of instrument approach procedures in the U.S.
Perhaps more important to general-aviation pilots is the fact that so many of the RNAV (GPS) procedures—especially those with LPV minimums—are at smaller airports that don’t have an ILS:
3,364 LPVs serving 1,661 airports
2,262 LPVs to non-ILS runways
1,535 LPVs to non-ILS airports
1,102 LPVs to ILS runways
2,020 LPVs to non-Part 139 airports (airports not approved for airline operations)
The agency intends to publish another 2,500 procedures by 2016, which will allow every runway in the nation that qualifies for an LPV to have one.
The latest data available from FAA, as of September 20, 2012, show the total number of approaches with LPV minimums has reached 2,989. By comparison, there were 1,281 category 1 ILS approaches in the inventory as of that date. More than 50 percent of the so-called LPV approaches serve airports that have no approaches that rely on ground-based navigation aids (i.e., ILS, localizer, VOR, or NDB). LPV procedures truly are expanding the options for instrument-rated pilots who fly aircraft equipped with IFR-approved, WAAS-capable GPS navigators.
LPV approaches can serve runways that may not meet the requirements for an ILS–indeed, many of those runways are suitable only for small general aviation aircraft. To learn about some of the criteria, see Table K-1. Criteria to Support Instrument Flight Procedure Development and the associated notes (from AC 150/5300). For example, the minimum runway length for an LPV approach is usually 3200 feet; the comparable number for an ILS is 4200 feet.
Now, the minimums for an LPV approach to a 3200-ft runway are at least 1 statute mile visibility and a DA of 350-400 feet. If an LPV procedure is to match the best minimums for a typical ILS (1/2 statute mile visibility and a DA of 200 feet), the LPV procedure must be to a runway that meets criteria for a conventional precision approach, including runway length, lighting, parallel taxiways, and markings.
For more details about the runway requirements for non-precision and precision approaches, see sections 220.127.116.11, 18.104.22.168, and 22.214.171.124 in AC 150/3500.
126.96.36.199 Non-Precision Approach (NPA).
An NPA is an instrument approach based on a navigation system that provides course deviation information, but no glidepath deviation information. NPA runways: 1. Support IFR approach operations to visibilities of ½ statute mile (0.8 km) or greater and have a HAT no lower than 250 feet (76 m). 2. Rely on NAVAIDs providing lateral only guidance for instrument approaches such as Very High Frequency Omnidirectional Range (VOR), non-directional beacon (NDB), Area Navigation (RNAV) Lateral Navigation (LNAV), localizer performance (LP), and localizer (LOC). 3. Generally, have lengths at least 3,200 feet (975 m) long, with a minimum width based on RDC. 4. Have runway edge lights using LIRL or MIRL. 5. Have non-precision runway markings, as defined in AC 150/5340-1.
188.8.131.52 Approach Procedure with Vertical Guidance (APV).
APV is an instrument approach based on a navigation system that is not required to meet the PA standards of the ICAO Annex 10, but that provides course and glidepath deviation information. Runways classified as APV handle instrument approach operations where the navigation system provides vertical guidance down to 200 feet (61 m) HAT and visibilities to as low as ½ statute mile (0.8 km). APV runways: 1. May apply to the following approach types: Vertical Navigation (VNAV), Localizer Performance with Vertical Guidance (LPV), or RNAV/Required Navigation Performance (RNP). 2. Typically have a length of at least 3,200 feet (975 m) in length and a typical width of at least 60 feet (18.3 m).
184.108.40.206 Precision Approach (PA).
A PA is an instrument approach based on a navigation system that provides course and glidepath deviation information. Runways classified as precision, handle instrument approach operations supporting an instrument approach with a HAT lower than 250 feet (76 m) and visibility lower than ¾ statute mile (1.2 km), down to and including Category (CAT) III. Precision Instrument Runways (PIRs): 1. Support IFR operations with visibilities down to and including CAT-III with the appropriate infrastructure. 2. Have navigational systems capable of supporting precision operations that include instrument landing system (ILS) and Ground Based Augmentation System (GBAS) Landing System (GLS). (FAA Order JO 6850.2 contains descriptions of various approach lighting systems.) 3. Have runway lengths of at least 4,200 feet (1280 m). 4. Have minimum runway width of at least 75 feet (22.9 m) with the typical width being 100 feet (30.5 m). 5. Have High Intensity Runway Lights (HIRL). 6. Have precision runway markings, as defined in AC 150/5340-1.
Of course, an LPV procedure is essentially just data in a GPS navigator. To establish an LPV procedures, the owners of an airport don’t have to invest in or maintain ILS transmitters. Once the FAA has the required obstacle surveys and gathered related information, publishing LPV procedures to both ends of an eligible runway (indeed, to the ends of all eligible runways at an airport) requires little incremental investment (for example, to cover the costs of designing and flight-testing each additional procedure). That’s the main reason that the FAA can publish so many new LPV procedures and plan to meet the goal, in four years, of making LPV approaches available to all eligible runways.