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AIM

10/12/17

5−4−19

Arrival Procedures

2. Circling MDA. The circling MDA will

provide 300 foot obstacle clearance within the area

considered for obstacle clearance and may be lower

than the LNAV/VNAV DA, but never lower than the

straight in LNAV MDA. This may occur when

different controlling obstacles are used or when other

controlling factors force the LNAV MDA to be higher

than 250 feet above the LNAV OCS. In FIG 5−4−12,

the required obstacle clearance for both the LNAV

and Circle resulted in the same MDA, but lower than

the LNAV/VNAV DA. FIG 5−4−13 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−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−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 prohibit-

ing 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 VDAs on all nonprecision approaches

except those published in conjunction with vertically

guided minimums or no-FAF procedures without

step-down fixes. A VDA does not guarantee obstacle

protection below the MDA in the visual segment. The