Updates to AIM, Effective April 3, 2014

The FAA has published updates to the Aeronautical Information Manual, effective April 3, 2014. You can download the PDF version of the new AIM here. The Explanation of Changes section describes the updates to the AIM. The online version of the new edition will be available on the FAA website on the effective date, here.

Key changes for general aviation pilots include:

1−1−3. VHF Omni−directional Range (VOR)

The only positive method of identifying a VOR is by its Morse Code identification or by the recorded
automatic voice identification which is always indicated by use of the word “VOR” following the
range’s name…Some VOR receivers are capable of identifying the VOR and will display the identifier of the VOR if it has successfully done so. However, it is still the pilot’s responsibility to verify the identity of the VOR by conventional methods.

1−1−18. Global Positioning System (GPS)—j. 2. Computer Navigation Fix (CNF)

A Computer Navigation Fix (CNF) is also a point defined by a latitude/longitude coordinate and is required to support area navigation (RNAV) system operations. The GPS receiver uses CNFs in conjunction with waypoints to navigate from point to point. However, CNFs are not recognized by Air Traffic Control (ATC). ATC does not maintain CNFs in their database and they do not use CNFs for any air traffic control purpose. CNFs may or may not be charted on FAA aeronautical navigation products, are listed in the chart legends, and are for advisory purposes only. Pilots are not to use CNFs for point to point navigation (proceed direct), filing a flight plan, or in aircraft/ATC communications. CNFs that do appear on aeronautical charts allow pilots increased situational awareness by identifying points in the aircraft database route of flight with points on the aeronautical chart. CNFs are random five−letter identifiers, not pronounceable like waypoints, and placed in parenthesis. Eventually, all CNFs will begin with the letters “CF” followed by three consonants (for example, CFWBG). This five−letter identifier will be found next to an “x” on enroute charts and possibly on an approach chart. On instrument approach procedures(charts) in the terminal procedures publication, CNFs may represent unnamed DME fixes, beginning and ending points of DME arcs, and sensor (ground−based signal i.e., VOR, NDB ILS) final approach fixes on GPS overlay approaches. These CNFs provide the GPS with points on the procedure that allow the overlay approach to mirror the ground−based sensor approach. These points should only be used by the GPS system for navigation and should not be used by pilots for any other purpose on the approach. The CNF concept has not been adopted or recognized by the International Civil Aviation Organization (ICAO).

Here are examples of CNFs as shown on the plan view of the ILS Y RWY 27 at KYKM:


5−4−1. j. Waypoints

1. GPS receivers navigate from one defined point to another retrieved from the aircraft’s on board navigational database. These points are waypoints (5-letter pronounceable name), existing VHF intersections, DME fixes with 5-letter pronounceable names and 3-letter NAVAID IDs. Each waypoint is a geographical location defined by a latitude/longitude geographic coordinate. These 5-letter waypoints, VHF intersections, 5-letter pronounceable DME fixes, and 3-letter NAVAID IDs are published on various FAA aeronautical navigation products (IFR Enroute Charts, VFR Charts, Terminal Procedures Publications, etc.)…

3. GPS approaches use fly−over and fly−by waypoints to join route segments on an approach. Fly−by waypoints connect the two segments by allowing the aircraft to turn prior to the current waypoint in order to roll out on course to the next waypoint. This is known as turn anticipation and is compensated for in the airspace and terrain clearances. The MAWP and the missed approach
holding waypoint (MAHWP) are normally the only two waypoints on the approach that are not fly−by waypoints. Fly−over waypoints are used when the aircraft must overfly the waypoint prior to starting a turn to the new course. The symbol for a fly-over waypoint is a circled waypoint. Some waypoints may have dual use; for example, as a fly-by waypoint when used as an IF for a NoPT route and as a fly-over waypoint when the same waypoint is also used as an IAF/IF hold-in-lieu of PT. When this occurs, the less restrictive (fly-by) symbology will be charted. Overlay approach charts and some early stand-alone GPS approach charts may not reflect this convention.

4. Unnamed waypoints for each airport will be uniquely identified in the database. Although the identifier may be used at different airports (for example, RW36 will be the identifier at each airport with a runway 36), the actual point, at each airport, is defined by a specific latitude/longitude coordinate.

5. The runway threshold waypoint, normally the MAWP, may have a five−letter identifier (for example, SNEEZ) or be coded as RW## (for example, RW36, RW36L). MAWPs located at the runway threshold are being changed to the RW## identifier, while MAWPs not located at the threshold will have a five− letter identifier. This may cause the approach chart to differ from the aircraft database until all changes are complete. The runway threshold waypoint is also used as the center of the Minimum Safe Altitude (MSA) on most GPS approaches.

5−4−1. l. Impact of Magnetic Variation on RNAV Systems

1. Differences may exist between charted magnetic courses on ground-based navigational aid
(NAVAID) instrument flight procedures (IFP), area navigation (RNAV) procedures, and RNAV systems on enroute charts, approach charts, and Standard Instrument Departure/Standard Terminal Arrival (SID/STAR) charts. These differences are due to the magnetic variance used to calculate the magnetic course. Every leg of an instrument procedure is first computed along a desired ground track with reference to true north. A magnetic variation correction is then applied to the true course in order to calculate a magnetic course for publication. The type of procedure will determine what magnetic variation value is added to the true course. A ground-based NAVAID IFP applies the facility magnetic variation of record to the true course to get the charted magnetic course. Magnetic courses on RNAV procedures are calculated two different ways. SID/STAR procedures use the airport magnetic variation of record, while IFR enroute charts use magnetic reference bearing. RNAV systems make a correction to true north by adding a magnetic variation calculated with an algorithm based on aircraft position, or by adding the magnetic variation coded in their navigational database. This may result in the RNAV system and the procedure designer using a different magnetic variation, which causes the magnetic course displayed by the RNAV system and the magnetic course charted on the IFP plate to be different. It is important to understand, however, that RNAV systems (with the exception of VOR/DME RNAV equipment) navigate by reference to true north and display magnetic course only for pilot reference. As such, a properly functioning RNAV system, containing a current and accurate navigational database, should still fly the correct ground track for any loaded instrument procedure, despite any differences in magnetic course that may be attributed to magnetic variation application. Should significant differences between the approach chart and the RNAV system avionics’ application of the navigation database arise, the published approach chart, supplemented by NOTAMs, holds precedence.

2. The course into a waypoint may not always be 180 degrees different from the course leaving the previous waypoint, due to the RNAV system avionics’ computation of geodesic paths, distance between waypoints and differences in magnetic variation application. Variations in distances may also occur since RNAV system distance−to−waypoint values are along−track distances (ATD) computed to the next waypoint and the DME values published on underlying procedures are slant−range distances measured to the station. This difference increases with aircraft altitude and proximity to the NAVAID.

5−3−4. Airways and Route Systems

(b) Unpublished RNAV routes are direct routes, based on area navigation capability, between waypoints defined in terms of latitude/longitude coordinates, degree−distance fixes, or offsets from established routes/airways at a specified distance and direction. Radar monitoring by ATC is required on all unpublished RNAV routes, except for GNSS−equipped aircraft cleared via filed published waypoints recallable from the aircraft’s navigation database.

5−4−1. Standard Terminal Arrival(STAR), Area Navigation (RNAV) STAR, and Flight Management System Procedures (FMSP) for Arrivals

This change incorporates updated guidance on resumption of published altitude and speed restrictions, guidance on what is expected of aircrews when issued a “climb via” clearance, and clarifies the expectation that pilots will advise the receiving controller of the altitude being vacated and the altitude they are climbing to when changing frequencies.

For all the details, see this section in the update to the AIM.

i. 5−4−5. Instrument Approach Procedure Charts

This change updates guidance to reflect the fact that the initial approach fix (IAF) waypoint is not an IAF, but an intermediate fix (IF). This change also updates guidance on descent below the minimum descent altitude (MDA).

For all the details, see this section in the update to the AIM.

7−1−11. Flight Information Services (FIS)

This change updates information and guidance to modify outdated information, reflect policy and terminology changes, and address changing technologies.

For all the details, see this section in the update to the AIM.

7−1−14. ATC Inflight Weather Avoidance Assistance

This change was added to expand the meaning of the phrase “when able” when used in conjunction with a clearance to deviate around weather. The clearance to deviate is clarified to allow maneuvering within the lateral limits of the deviation clearance.

For all the details, see this section in the update to the AIM.


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