AIM
4/20/23
below DA while transitioning from the final approach to the missed approach. The aircraft is expected to follow
the missed instructions while continuing along the published final approach course to at least the published
runway threshold waypoint or MAP (if not at the threshold) before executing any turns.
(b)
Minimum Descent Altitude (MDA) has been in use for many years, and will continue to be used for
the LNAV only and circling procedures.
(c)
Threshold Crossing Height (TCH) has been traditionally used in “precision” approaches as the height
of the glide slope above threshold. With publication of LNAV/VNAV minimums and RNAV descent angles,
including graphically depicted descent profiles, TCH also applies to the height of the “descent angle,” or
glidepath, at the threshold. Unless otherwise required for larger type aircraft which may be using the IAP, the
typical TCH is 30 to 50 feet.
6.
The MINIMA FORMAT will also change slightly.
(a)
Each line of minima on the RNAV IAP is titled to reflect the level of service available; e.g., GLS, LPV,
LNAV/VNAV, LP, and LNAV. CIRCLING minima will also be provided.
(b)
The minima title box indicates the nature of the minimum altitude for the IAP. For example:
(1)
DA will be published next to the minima line title for minimums supporting vertical guidance such
as for GLS, LPV or LNAV/VNAV.
(2)
MDA will be published as the minima line on approaches with lateral guidance only, LNAV, or LP.
Descent below the MDA must meet the conditions stated in 14 CFR Section 91.175.
(3)
Where two or more systems, such as LPV and LNAV/VNAV, share the same minima, each line of
minima will be displayed separately.
7.
Chart Symbology changed slightly to include:
(a) Descent Profile.
The published descent profile and a graphical depiction of the vertical path to the
runway will be shown. Graphical depiction of the RNAV vertical guidance will differ from the traditional
depiction of an ILS glide slope (feather) through the use of a shorter vertical track beginning at the decision
altitude.
(1)
It is FAA policy to design IAPs with minimum altitudes established at fixes/waypoints to achieve
optimum stabilized (constant rate) descents within each procedure segment. This design can enhance the safety
of the operations and contribute toward reduction in the occurrence of controlled flight into terrain (CFIT)
accidents. Additionally, the National Transportation Safety Board (NTSB) recently emphasized that pilots could
benefit from publication of the appropriate IAP descent angle for a stabilized descent on final approach. The
RNAV IAP format includes the descent angle to the hundredth of a degree; e.g., 3.00 degrees. The angle will be
provided in the graphically depicted descent profile.
(2)
The stabilized approach may be performed by reference to vertical navigation information
provided by WAAS or LNAV/VNAV systems; or for LNAV
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only systems, by the pilot determining the
appropriate aircraft attitude/groundspeed combination to attain a constant rate descent which best emulates the
published angle. To aid the pilot, U.S. Government Terminal Procedures Publication charts publish an expanded
Rate of Descent Table on the inside of the back hard cover for use in planning and executing precision descents
under known or approximate groundspeed conditions.
(b) Visual Descent Point (VDP).
A VDP will be published on most RNAV IAPs. VDPs apply only to
aircraft utilizing LP or LNAV minima, not LPV or LNAV/VNAV minimums.
(c) Missed Approach Symbology.
In order to make missed approach guidance more readily
understood, a method has been developed to display missed approach guidance in the profile view through the
use of quick reference icons. Due to limited space in the profile area, only four or fewer icons can be shown.
However, the icons may not provide representation of the entire missed approach procedure. The entire set of
textual missed approach instructions are provided at the top of the approach chart in the pilot briefing. (See
6).
Arrival Procedures
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