AIM 

4/20/23

 

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Arrival Procedures

for both the LNAV and Circle resulted in the same MDA, but lower than the LNAV/VNAV DA. FIG 5

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4

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13

provides an illustration of this type of situation.

3. Vertical guidance (LNAV/VNAV).

 A line is drawn horizontal at obstacle height until reaching the

obstacle clearance surface (OCS). At the OCS, a vertical line is drawn until reaching the glide path. This is the
DA for the approach. This method places the offending obstacle in front of the LNAV/VNAV DA so it can be
seen and avoided. In some situations, this may result in the LNAV/VNAV DA being higher than the LNAV and/or
Circling MDA.

h. The

 

Visual Descent Point (VDP)

, identified by the symbol (V), is a defined point on the final approach

course of a nonprecision straight

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in approach procedure from which a stabilized visual descent from the MDA

to the runway touchdown point may be commenced. The pilot should not descend below the MDA prior to
reaching the VDP. The VDP will be identified by DME or RNAV along

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track distance to the MAP. The VDP

distance is based on the lowest MDA published on the IAP and harmonized with the angle of the visual glide
slope indicator (VGSI) (if installed) or the procedure VDA (if no VGSI is installed). A VDP may not be published
under certain circumstances which may result in a destabilized descent between the MDA and the runway
touchdown point. Such circumstances include an obstacle penetrating the visual surface between the MDA and
runway threshold, lack of distance measuring capability, or the procedure design prevents a VDP to be identified.

1.

VGSI systems may be used as a visual aid to the pilot to determine if the aircraft is in a position to make

a stabilized descent from the MDA. When the visibility is close to minimums, the VGSI may not be visible at
the VDP due to its location beyond the MAP.

2.

Pilots not equipped to receive the VDP should fly the approach procedure as though no VDP had been

provided.

3.

On a straight-in nonprecision IAP, descent below the MDA between the VDP and the MAP may be

inadvisable or impossible. Aircraft speed, height above the runway, descent rate, amount of turn, and runway
length are some of the factors which must be considered by the pilot to determine if a safe descent and landing
can be accomplished.

i.

A visual segment obstruction evaluation is accomplished during procedure design on all IAPs. Obstacles

(both lighted and unlighted) are allowed to penetrate the visual segment obstacle identification surfaces.
Identified obstacle penetrations may cause restrictions to instrument approach operations which may include an
increased approach visibility requirement, not publishing a VDP, and/or prohibiting night instrument operations
to the runway. There is no implicit obstacle protection from the MDA/DA to the touchdown point. Accordingly,
it is the responsibility of the pilot to visually acquire and avoid obstacles below the MDA/DA during transition
to landing.

1.

Unlighted obstacle penetrations may result in prohibiting night instrument operations to the runway. A

chart note will be published in the pilot briefing strip “Procedure NA at Night.”

2.

Use of a VGSI may be approved in lieu of obstruction lighting to restore night instrument operations to

the runway. A chart note will be published in the pilot briefing strip “ Straight-in Rwy XX at Night, operational
VGSI required, remain on or above VGSI glidepath until threshold.”

j.

The highest obstacle (man-made, terrain, or vegetation) will be charted on the planview of an IAP. Other

obstacles may be charted in either the planview or the airport sketch based on distance from the runway and
available chart space. The elevation of the charted obstacle will be shown to the nearest foot above mean sea level.
Obstacles without a verified accuracy are indicated by a 

±

 symbol following the elevation value.

k. Vertical Descent Angle (VDA).

 FAA policy is to publish a VDA/TCH on all nonprecision approaches

except those published in conjunction with vertically guided minimums (i.e., ILS or LOC RWY XX) or no-FAF
procedures without a step-down fix (i.e., on

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airport VOR or NDB). A VDA does not guarantee obstacle

protection below the MDA in the visual segment. The presence of a VDA does not change any nonprecision
approach requirements.

1.

Obstacles may penetrate the obstacle identification surface below the MDA in the visual segment of an

IAP that has a published VDA/TCH. When the VDA/TCH is not authorized due to an obstacle penetration that