AIM Updates 28 February 2019

FAA has published changes to the AIM effective 28 February 2019. You can download the PDF that lists the changes and includes all of the updated text. The updates of most interest to general aviation pilots focus on the following sections.

1−2−1. General

1−2−2. Required Navigation Performance (RNP)

5−2−9. Instrument Departure Procedures (DP) − Obstacle Departure Procedures (ODP), Standard Instrument Departures (SID), and Diverse Vector Areas (DVA)

5−4−1. Standard Terminal Arrival (STAR) Procedures

5−4−5. Instrument Approach Procedure (IAP) Charts

There was not enough adequate information concerning Performance−Based Navigation (PBN) and Advanced Required Navigational Performance (A−RNP) available to flight crews and operators in the AIM. This expansion in the description and advantages of these navigation specifications (NavSpecs) will provide better guidance as to what A−RNP is, how it will be applied, and its applicability in the PBN NAS. Additional information is being added to better clarify NavSpecs, RNP, and PBN understanding in AIM Chapter 1. Associated paragraph changes are necessary to ensure harmonization between all the paragraphs in the AIM.

5−1−8. Flight Plan (FAA Form 7233−1) − Domestic IFR Flights

This change updates pilot guidance to incorporate air traffic control (ATC) procedures for GNSS−equipped aircraft operating on area navigation (RNAV) air traffic service (ATS) routes and on random point−to−point and random impromptu routes in airspace in which ATC procedures are applied, excluding oceanic airspace. This change also incorporates the use of the term GNSS in place of RNAV for space−based positioning and navigation systems.

Area Navigation, RNAV, RNP, and A-RNP

AIM 1−2−1 includes new explanations of RNAV and performance-based navigation (PBN). Before reviewing the new information in this section of the AIM, it’s important to remember that AIM 1−1−17. Global Positioning System (GPS) notes that:

(5) Aircraft navigating by IFR−approved GPS are considered to be performance−based navigation (PBN) aircraft and have special equipment suffixes.

The specific capabilities of the GNSS (GPS) in your panel are described in the AFM Supplement and operating handbooks for the equipment (as updated when new system software is installed). You can find more information about RNAV and RNP specs in AC 90-105 and at RNP Procedures and Typical Part 91 Pilots here at BruceAir.

With that in mind, it’s important to understand that if your airplane is equipped with, say, a Garmin GNS530W/GNS530W or GTN 750/650 (with an appropriate AFM supplement), you can fly RNAV SIDs and STARs based on RNP-1 criteria. And you can also fly en route segments that require RNP-2 accuracy. No special authorization is required at these RNP levels.

For more information about RNP levels, see “Required Navigation Performance” in the Instrument Procedures Handbook (2-34).

IPH-RNP Levels

Figure 9-41 in the Instrument Flying Handbook is also helpful.

IFH-Fig9-41

Update to AIM 1−2−1. General

Here’s the new language in AIM 1-2-1, the introduction to PBN. Note that RAIM, used to validate the accuracy and reliablity of non-WAAS GPS for use under IFR, qualifies as “onboard performance monitoring and alerting capability” for purposes of PBN and basic RNP. WAAS, which incorporates its own performance and accuracy checking system, also provides onboard performance monitoring and alerting capability.

a. Introduction to PBN. As air travel has evolved, methods of navigation have improved to give operators more flexibility. PBN exists under the umbrella of area navigation (RNAV). The term RNAV in this context, as in procedure titles, just means “area navigation,” regardless of the equipment capability of the aircraft…Many operators have upgraded their systems to obtain the benefits of PBN. Within PBN there are two main categories of navigation methods or specifications: area navigation (RNAV) and required navigation performance (RNP). In this context, the term RNAV x means a specific navigation specification with a specified lateral accuracy value. For an aircraft to meet the requirements of PBN, a specified RNAV or RNP accuracy must be met 95 percent of the flight time. RNP is a PBN system that includes onboard performance monitoring and alerting capability (for example, Receiver Autonomous Integrity Monitoring (RAIM)). PBN also introduces the concept of navigation specifications (NavSpecs) which are a set of aircraft and aircrew requirements needed to support a navigation application within a defined airspace concept. For both RNP and RNAV NavSpecs, the numerical designation refers to the lateral navigation accuracy in nautical miles which is expected to be achieved at least 95 percent of the flight time by the population of aircraft operating within the airspace, route, or procedure. This information is detailed in International Civil Aviation Organization’s (ICAO) Doc 9613, Performance−based Navigation (PBN) Manual and the latest FAA AC 90−105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Remote and Oceanic Airspace.

Required Navigation Performance (RNP)

Here’s the new language in AIM 1−2−2.

a. General. While both RNAV navigation specifications (NavSpecs) and RNP NavSpecs contain specific performance requirements, RNP is RNAV with the added requirement for onboard performance monitoring and alerting (OBPMA). RNP is also a statement of navigation performance necessary for operation within a defined airspace. A critical component of RNP is the ability of the aircraft navigation system to monitor its achieved navigation performance, and to identify for the pilot whether the operational requirement is, or is not, being met during an operation. OBPMA capability therefore allows a lessened reliance on air traffic control intervention and/or procedural separation to achieve the overall safety of the operation. RNP capability of the aircraft is a major component in determining the separation criteria to ensure that the overall containment of the operation is met. The RNP capability of an aircraft will vary depending upon the aircraft equipment and the navigation infrastructure. For example, an aircraft may be eligible for RNP 1, but may not be capable of RNP 1 operations due to limited NAVAID coverage or avionics failure. The Aircraft Flight Manual (AFM) or avionics documents for your aircraft should specifically state the aircraft’s RNP eligibilities. Contact the manufacturer of the avionics or the aircraft if this information is missing or incomplete. NavSpecs should be considered different from one another, not “better” or “worse” based on the described lateral navigation accuracy. It is this concept that requires each NavSpec eligbility to be listed separately in the avionics documents or AFM. For example, RNP 1 is different from RNAV 1, and an RNP 1 eligibility does NOT mean automatic RNP 2 or RNAV 1 eligibility. As a safeguard, the FAA requires that aircraft navigation databases hold only those procedures that the aircraft maintains eligibility for. If you look for a specific instrument procedure in your aircraft’s navigation database and cannot find it, it’s likely that procedure contains PBN elements your aircraft is ineligible for or cannot compute and fly. Further, optional capabilities such as Radius−to−fix (RF) turns or scalability should be described in the AFM or avionics documents. Use the capabilities of your avionics suite to verify the appropriate waypoint and track data after loading the procedure from your database.

RNP Approach (RNP APCH) and RNP AR APCH

The new language in this section of the AIM intends to address confusion about RNP and approaches. Unfortunately, because FAA continues to use RNAV in procedure titles, many pilots remain puzzled about the differences between the terms RNAV, RNP APCH, and RNP AR APCH. As this part of the revised AIM 1−2−2 notes:

In the U.S., RNP APCH procedures are titled RNAV (GPS) and offer several lines of minima to accommodate varying levels of aircraft equipage: either lateral navigation (LNAV), LNAV/vertical navigation (LNAV/VNAV), Localizer Performance with Vertical Guidance (LPV), and Localizer Performance (LP).

A helpful guide from FAA, Required Navigation Performance (RNP) Approaches (APCH), succinctly explains the different lines of minimums and provides helpful links to ACs, the AIM, and other sources.

Here’s the detailed language in the updated AIM:

(1) RNP Approach (RNP APCH). In the U.S., RNP APCH procedures are titled RNAV (GPS) and offer several lines of minima to accommodate varying levels of aircraft equipage: either lateral navigation (LNAV), LNAV/vertical navigation (LNAV/VNAV), Localizer Performance with Vertical Guidance (LPV), and Localizer Performance (LP). GPS with or without Space−Based Augmentation System (SBAS) (for example, WAAS) can provide the lateral information to support LNAV minima. LNAV/VNAV incorporates LNAV lateral with vertical path guidance for systems and operators capable of either barometric or SBAS vertical. Pilots are required to use SBAS to fly to the LPV or LP minima. RF turn capability is optional in RNP APCH eligibility. This means that your aircraft may be eligible for RNP APCH operations, but you may not fly an RF turn unless RF turns are also specifically listed as a feature of your avionics suite. GBAS Landing System (GLS) procedures are also constructed using RNP APCH NavSpecs and provide precision approach capability. RNP APCH has a lateral accuracy value of 1 in the terminal and missed approach segments and essentially scales to RNP 0.3 (or 40 meters with SBAS) in the final approach. (See Paragraph 5−4−18, RNP AR Instrument Approach Procedures.)

(2) RNP Authorization Required Approach (RNP AR APCH). In the U.S., RNP AR APCH procedures are titled RNAV (RNP). These approaches have stringent equipage and pilot training standards and require special FAA authorization to fly. Scalability and RF turn capabilities are mandatory in RNP AR APCH eligibility. RNP AR APCH vertical navigation performance is based upon barometric VNAV or SBAS. RNP AR is intended to provide specific benefits at specific locations. It is not intended for every operator or aircraft. RNP AR capability requires specific aircraft performance, design, operational processes, training, and specific procedure design criteria to achieve the required target level of safety. RNP AR APCH has lateral accuracy values that can range below 1 in the terminal and missed approach segments and essentially scale to RNP 0.3 or lower in the final approach. Before conducting these procedures, operators should refer to the latest AC 90−101, Approval Guidance for RNP Procedures with AR. (See paragraph 5−4−18.)

Advanced RNP (A−RNP)

If you’re keeping up so far, the new language in AIM 1−2−2 provides more details about Advanced RNP (A-RNP), not to be confused with RNP (AR). Some features of A-RNP, such as the ability to fly some RF legs, are available if you have the current system software installed in a Garmin GTN navigator. For more information, see Garmin GTN Avionics and RF Legs here at BruceAir.

(4) Advanced RNP (A−RNP). Advanced RNP is a NavSpec with a minimum set of mandatory functions enabled in the aircraft’s avionics suite. In the U.S., these minimum functions include capability to calculate and perform RF turns, scalable RNP, and parallel offset flight path generation. Higher continuity (such as dual systems) may be required for certain oceanic and remote continental airspace. Other “advanced” options for use in the en route environment (such as fixed radius transitions and Time of Arrival Control) are optional in the U.S. Typically, an aircraft eligible for A−RNP will also be eligible for operations comprising: RNP APCH, RNP/RNAV 1, RNP/RNAV 2, RNP 4, and RNP/RNAV 10. A−RNP allows for scalable RNP lateral navigation values (either 1.0 or 0.3) in the terminal environment. Use of these reduced lateral accuracies will normally require use of the aircraft’s autopilot and/or flight director. See the latest AC 90−105 for more information on A−RNP, including NavSpec bundling options, eligibility determinations, and operations approvals.

NOTE−
A−RNP eligible aircraft are NOT automatically eligible for RNP AR APCH or RNP AR DP operations, as RNP AR eligibility requires a separate determination process and special FAA authorization.

(5) RNP 1. RNP 1 requires a lateral accuracy value of 1 for arrival and departure in the terminal area, and the initial and intermediate approach phase when used on conventional procedures with PBN segments (for example, an ILS with a PBN feeder, IAF, or missed approach). RF turn capability is optional in RNP 1 eligibility. This means that your aircraft may be eligible for RNP 1 operations, but you may not fly an RF turn unless RF turns are also specifically listed as a feature of your avionics suite.

(6) RNP 2. RNP 2 will apply to both domestic and oceanic/remote operations with a lateral accuracy value of 2.

PBN Requirement Boxes

AIM 1−2−2 now includes language about equipment requirement boxes on procedures that include PBN elements. For more information, see New Equipment Required Notes and An ILS that Requires GPS here at BruceAir.

(c) Depiction of PBN Requirements. In the U.S., PBN requirements like Lateral Accuracy Values or NavSpecs applicable to a procedure will be depicted on affected charts and procedures. In the U.S., a specific procedure’s Performance−Based Navigation (PBN) requirements will be prominently displayed in separate, standardized notes boxes. For procedures with PBN elements, the “PBN box” will contain the procedure’s NavSpec(s); and, if required: specific sensors or infrastructure needed for the navigation solution, any additional or advanced functional requirements, the minimum RNP value, and any amplifying remarks. Items listed in this PBN box are REQUIRED to fly the procedure’s PBN elements. For example, an ILS with an RNAV missed approach would require a specific capability to fly the missed approach portion of the procedure. That required capability will be listed in the PBN box. The separate Equipment Requirements box will list ground−based equipment and/or airport specific requirements. On procedures with both PBN elements and ground−based equipment requirements, the PBN requirements box will be listed first.

Flying and Flying Direct with GNSS (GPS)

AIM 5−1−8 now provides more details for pilots flying under IFR with GNSS about filing direct route or requesting direct clearances from ATC. The new text focuses on direct routes that include legs that exceed navaid service volumes and provides more details about filing direct routes.

In particular, if you plan a direct flight you should:

  • File and fly point-to-point using published waypoint names (airports, navaids, intersections, and RNAV waypoints) to define the route of flight.
  • Include at least one named waypoint within each ARTCC through which the flight will pass.

4. Increasing use of self−contained airborne navigational systems which do not rely on the VOR/VORTAC/TACAN system has resulted in pilot requests for direct routes that exceed NAVAID service volume limits. With the exception of GNSS−equipped aircraft, these direct route requests will be approved only in a radar environment, with approval based on pilot responsibility for navigation on the authorized direct route. Radar flight following will be provided by ATC for ATC purposes. For GNSS−equipped aircraft, ATC may approve a direct route that exceeds ground based NAVAID service volume limits; however, in a non−radar environment, the routing must be “point−to−point,” defined as navigation from a published point to a published point, and navigational assistance will not be available. (See subparagraph 5−1−8d below.)

5. At times, ATC will initiate a direct route in a radar environment that exceeds NAVAID service volume limits. In such cases ATC will provide radar monitoring and navigational assistance as necessary. For GNSS−equipped aircraft, if the route is point−to−point, radar monitoring and navigational assistance is not required. (See subparagraph 5−1−8d below.)

d. Area Navigation (RNAV)/Global Navigation Satellite System (GNSS) 1. Except for GNSS−equipped aircraft, random impromptu routes can only be approved in a radar environment. A random impromptu route is a direct course initiated by ATC or requested by the pilot during flight. Aircraft are cleared from their present position to a NAVAID, waypoint, fix, or airport. Factors that will be considered by ATC in approving random impromptu routes include the capability to provide radar monitoring and compatibility with traffic volume and flow. ATC will radar monitor each flight; however, navigation on the random impromptu route is the responsibility of the pilot. GNSS−equipped aircraft are allowed to operate in a non−radar environment when the aircraft is cleared via, or is reported to be established on, a point−to−point route. The points must be published NAVAIDs, waypoints, fixes, or airports recallable from the aircraft’s database. The distance between the points cannot exceed 500 miles and navigational assistance will not be provided…

(f) File a minimum of one route description waypoint for each ARTCC through whose area the random route will be flown.

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New Equipment Required Notes

FAA has published a charting notice (PDF) that describes how equipment requirements will be noted on terminal procedure charts. This change is based on a long discussion at the Aeronautical Charting Forum (see 13-02-312: Equipment Requirement Notes on Instrument Approach Procedure).

For procedures with PBN elements, the PBN box will contain the procedure’s navigation specification(s); and, if required: specific sensors or infrastructure needed for the navigation solution; any additional or advanced functional requirements; the minimum Required Navigation Performance (RNP) value and any amplifying remarks. Items listed in this PBN box are REQUIRED. The separate Equipment Requirements Box will list ground-based equipment requirements. On procedures with both PBN elements and ground-based equipment requirements, the PBN requirements box will be listed first.

The publication of the new notes will continue incrementally until all charts have been amended to comply with the new standard.

A sample of the new notes boxes is below.

PBN Requirements Notes

Here’s an example of the requirements box on the recently updated chart for the ILS RWY 28R approach at Billings, MT (KBIL):

KBIL-ILS-PlanView

Fall 2017 Update on VOR Decommissioning

At the October 2017 meeting of the Aeronautical Charting Forum, the FAA provided an update on the program gradually to decommission about 309 VORs by 2025 as part of the switch to GNSS-based performance based navigation (PBN).

To see the full list of VORs that FAA plans to decommission, visit this post at BruceAir.

VORandMON-Overview

According to the minutes of that meeting and a presentation from an FAA representative, the switch to the mininimum operational network (MON) of about 587 VORs includes the following highlights:

Discontinued 16 VORs to date:
– [EDS] Edisto, in Orangeburg, SC – February 4, 2016
– [BUA] Buffalo, in Buffalo, SD – July 21, 2016
– [PNN] Princeton, in Princeton ME – July 21, 2016
– [PLB] Plattsburgh, in Plattsburgh, NY – September 15, 2016
– [AOH] Allen County , in Lima, OH – September 15, 2016
– [ABB] Nabb, in Nabb Indiana – January 5, 2017
– [SYO] Sayre, in Sayre Oklahoma – April 27, 2017
– [ENW] Kenosha, in Kenosha Wisconsin – June 22, 2017
– [BTL] Battle Creek, in Battle Creek, Michigan – June 22,2017
– [HRK] Horlick, in Horlick Wisconsin – June 22, 2017
– [HUW] West Plains, Missouri – August 17, 2017
– [RIS] Kansas City, Missouri – September 14, 2017
– [DDD] Port City, in Muscatine, IA – October 12, 2017
– [JKS] Jacks Creek, TN – October 12, 2017
– [MXW] Maxwell, CA – October 12, 2017
– [STE] Stevens Point, WI – October 12, 2017

Over the next six months, the following  seven VORs are scheduled to be shut down:

– [AOO] Altoona, PA
– [BRD] Brainerd, MN
– [DKK] Dunkirk, NY
– [HVN] New Haven, CT
– [PNE] North Philadelphia, PA
– [RNL] Rainelle, WV
– [RUT] Rutland, VT

You can follow the links in the list above to see the VORs on a VFR chart. Note that these navaids are not the only VORs in the vicinity. In fact, in most cases, at least one VOR is within just a few miles of the facility slated for shutdown.

HVN-VOR

Part of the switch to the MON is establishing new VOR service volumes. The FAA representative noted that upgrading and flight checking remaining VORs is one the next steps in the VOR MON program. The upgraded service volume values will be 70 nm at or above 5000 ft and 130 nm above 18,000 ft for high VORs. When the flight checks are complete, new information about VOR service volumes will be published in the Chart Supplement and the AIM.

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.

 

Updated AC 90-105A

FAA has published AC 90-105A – Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace (PDF available at the link).

AC90-105A

 

This update to the previous edition (published in 2009) contains many important changes for pilots who use GPS to navigate under IFR.

FAA is gradually adopting the concept of performance based navigation (PBN), which includes the old systems of area navigation (RNAV) and refines details of required navigation performance (RNP). For more details about these standards, see AIM Section 2. Performance−Based Navigation (PBN) and Area Navigation (RNAV).

How FAA Hopes to Change the Airway Structure

FAA has outlined a concept for overhauling the current network of low- and high-altitude airways. The plan is part of the FAA’s initiative to move toward performance-based navigation (PBN). At present, the proposal is just that—it isn’t a formal program with full funding.

The presentation, given at the FAA’s Aeronautical Charting Forum meeting on October 28-30, is available as a PDF in my  Aviation Documents folder at OneDrive.

The guiding principles of the proposal are:

  • “Structure where structure is necessary and point-to-point where it is not.”
  • Route structure requirements will be based on factors such as traffic demand, airspace utilization, ATC task complexity, airspace access, and user operational efficiencies.
  • Ground based airways will be retained in areas of with poor radar coverage and in mountainous terrain.

Pilots of light aircraft are most concerned about low-altitude airways and routings, including the venerable victor airways and newer T-routes.

image

Regarding T-routes, FAA hopes to publish low-altitude PBN ATS routes “precisely where needed to”:

  • Access rather than circumvent Class B/C airspace
  • Lower minimum altitudes in areas of high terrain to improve access and avoid icing
  • Circumvent Special Use Airspace in safe and optimal manner

The presentation includes an interesting slide that shows daily utilization of victor airways. The average for the top 81-100 low-altitude airways was just 3 operations (in FY2013).

The graphic below shows how V2, which runs east-west across the northern part of the US, was used in the last two fiscal years. Very few aircraft flew most segments of the airway.

image

Note that the segment that crosses the Cascades east of Seattle (SEA-ELN) gets regular traffic. Other segments, such as MINNY-MKG across Lake Michigan, and legs near BUF, are also well-used, probably due to ATC requirements in these high-traffic areas.

The FAA notes that 80-90% of the aircraft flying the 20 most-used victor airways are already equipped to fly T-routes, which require an IFR-approved GPS.

image

Given that so many aircraft are RNAV-capable, FAA notes that “Users file any combination of route segments, NAVAIDs, and  waypoints when not route restricted by ATC and automation.”

The proposal advocates retiring existing point-to-point navigation programs to give pilots more flexibility in planning and filing direct routes. FAA says it will work with users to create a network of optimally placed waypoints. When specific routes are required, the plan would expand the network of ATC IFR preferred routes, which would not necessarily follow existing airways. Point-to-point navigation would available elsewhere.

The new routes outlines in the plan would also:

  • Increase the number of parallel route options through high density airspace
  • Reduce separation between centerlines of published routes to 8 nm
  • Circumnavigate Special Activity Airspace

For example, the program noted that T-319 passes directly over KATL, giving controllers a straightforward way to route aircraft through the Atlanta Class B airspace.

image

Update on VOR Decommissioning

The Aeronautical Charting Forum, a forum sponsored by FAA, met on April 29, 2014 outside Washington, DC. Among the items on the agenda was an update on FAA’s plans to reduce the number of VORs to a minimum operational network (MON). You can download and review a PDF version of the FAA’s PowerPoint presentation here. (Minutes from the full two-day meeting are available here.)

Key points:

  • FAA now plans to transition from a legacy network of 967 VORs to a MON of  approximately 500 VORs by FY2025. That’s a slip of five years from the previous goal of establishing the MON by 2020. For more background, see the FAA’s VOR Minimum Operational Network (MON) Information Paper (PDF).
  • The number of VORs comprising the MON may increase or decrease depending on the requirements for the Department of Defense and the Tactical Operations Committee.

You can find additional details about the FAA’s program to decommission VORs here at BruceAir’s blog: