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3. Required Navigation Performance (RNP)
(a) Pilots are advised to refer to the
“TERMS/LANDING MINIMUMS DATA” (Section
A) of the U.S. Government Terminal Procedures
books for aircraft approach eligibility requirements
by specific RNP level requirements.
(b) Some aircraft have RNP approval in their
AFM without a GPS sensor. The lowest level of
sensors that the FAA will support for RNP service is
DME/DME. However, necessary DME signal may
not be available at the airport of intended operations.
2/19/04 AIM
Arrival Procedures 5−4−21
For those locations having an RNAV chart published
with LNAV/VNAV minimums, a procedure note may
be provided such as “DME/DME RNP−0.3 NA.”
This means that RNP aircraft dependent on
DME/DME to achieve RNP−0.3 are not authorized to
conduct this approach. Where DME facility
availability is a factor, the note may read “DME/DME
RNP−0.3 Authorized; ABC and XYZ Required.”
This means that ABC and XYZ facilities have been
determined by flight inspection to be required in the
navigation solution to assure RNP−0.3. VOR/DME
updating must not be used for approach procedures.
4. Chart Terminology
(a) Decision Altitude (DA) replaces the
familiar term Decision Height (DH). DA conforms to
the international convention where altitudes relate to
MSL and heights relate to AGL. DA will eventually
be published for other types of instrument approach
procedures with vertical guidance, as well. DA
indicates to the pilot that the published descent profile
is flown to the DA (MSL), where a missed approach
will be initiated if visual references for landing are not
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.
5. 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, 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 where the
minima line was designed to support aircraft with
only lateral guidance available, such as LNAV.
Descent below the MDA, including during the missed
approach, is not authorized unless the visual
conditions stated in 14 CFR Section 91.175 exist.
(3) Where two or more systems, such as
LPV and LNAV/VNAV, share the same minima, each
line of minima will be displayed separately.
6. 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
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