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AIM

10/12/17

5−4−23

Arrival Procedures

NOTE−

RNAV and Baro−VNAV systems must have a manufacturer

supplied electronic database which must include the

waypoints, altitudes, and vertical data for the procedure to

be flown. The system must be able to retrieve the procedure

by name from the aircraft navigation database, not just as

a manually entered series of waypoints.

3. ILS or RNAV (GPS) charts.

(a) Some RNAV (GPS) charts will also

contain an ILS line of minima to make use of the ILS

precision final in conjunction with the RNAV GPS

capabilities for the portions of the procedure prior to

the final approach segment and for the missed

approach. Obstacle clearance for the portions of the

procedure other than the final approach segment is

still based on GPS criteria.

NOTE−

Some GPS receiver installations inhibit GPS navigation

whenever ANY ILS frequency is tuned. Pilots flying

aircraft with receivers installed in this manner must wait

until they are on the intermediate segment of the procedure

prior to the PFAF (PFAF is the active waypoint) to tune the

ILS frequency and must tune the ILS back to a VOR

frequency in order to fly the GPS based missed approach.

(b) Charting. There are charting differences

between ILS, RNAV (GPS), and GLS approaches.

(1) The LAAS procedure is titled “GLS

RWY XX” on the approach chart.

(2) The VDB provides information to the

airborne receiver where the guidance is synthesized.

(3) The LAAS procedure is identified by a

four alpha−numeric character field referred to as the

RPI or approach ID and is similar to the IDENT

feature of the ILS.

(4) The RPI is charted.

(5) Most RNAV(GPS) approach charts

have had the GLS (NA) minima line replaced by an

LPV line of minima.

(6) Since the concepts for LAAS and

WAAS procedure publication have evolved, GLS

will now be used only for LAAS minima, which will

be on a separate approach chart.

4. Required Navigation Performance (RNP).

(a) Pilots are advised to refer to the

“TERMS/LANDING MINIMUMS DATA” (Sec-

tion 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.

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.

5. 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.