AIM

8/15/19

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24

Arrival Procedures

established. Obstacle clearance is provided to allow
a momentary descent 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. CIR-
CLING 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 per-

formed 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

 

FIG 5

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6).

(d) Waypoints.

All RNAV or GPS stand

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alone IAPs are flown using data pertaining to the
particular IAP obtained from an onboard database,
including the sequence of all WPs used for the