AIM

4/3/14

5−4−58

Arrival Procedures

light system (ALS), if installed, or both the runway

threshold and the TDZ), confirm lateral alignment,

maneuver to the extended runway centerline earlier

than would otherwise be possible, and continue a nor-

mal descent from the DA or MDA to 100 feet above

the TDZE.

1. Required Visual References.

In order to

descend below DA or MDA, the following visual

references (specified in 14 CFR part 91.175 (l)(3)) for

the runway of intended landing must be distinctly

visible and identifiable to the pilot using the EFVS:

(a)

The ALS (if installed), or

(b)

The following visual references in both

(b)(1) and (b)(2) below:

(1)

The runway threshold, identified by at

least one of the following: the beginning of the run-

way landing surface, the threshold lights, or the

runway end identifier lights (REIL).

(2)

The TDZ, identified by at least one of

the following: the runway TDZ landing surface, the

TDZ lights, the TDZ markings, or the runway lights.

2. Comparison of Visual Reference Require-

ments for EFVS and Natural Vision.

The EFVS

visual reference requirements of 14 CFR part 91.175

(l)(3) comprise a more stringent standard than the

visual reference requirements prescribed under 14

CFR part 91.175 (c)(3) when using natural vision.

The more stringent standard is needed because an

EFVS might not display the color of the lights used

to identify specific portions of the runway or might

not be able to consistently display the runway mark-

ings. The main differences for EFVS operations are

that the visual glide slope indicator (VGSI) lights

cannot be used as a visual reference, and specific

visual references from both the threshold and TDZ

must be distinctly visible and identifiable. However,

when using natural vision, only one of the specified

visual references must be visible and identifiable.

3. Visual References and Offset

Approaches.

Pilots must be especially knowledge-

able of the approach conditions and approach course

alignment when considering whether to rely on EFVS

during a non−precision approach with an offset final

approach course. Depending upon the combination of

crosswind correction and the lateral field of view

provided by a particular EFVS, the required visual

references may or may not be within the pilot’s view

looking through the EFVS display. Pilots conducting

any non−precision approach must verify lateral align-

ment with the runway centerline when determining

when to descend from MDA.

4. When to Go Around.

Any pilot operating

an aircraft with an EFVS installed should be aware

that the requirements of 14 CFR part 91.175 (c) for

using natural vision and the requirements of 14 CFR

part 91.175 (l) for using an EFVS are different. A

pilot would, therefore, first have to determine

whether an approach will be commenced using

natural vision or using an EFVS. While these two sets

of requirements provide a parallel decisionmaking

process, the requirements for when a missed

approach must be executed differ. Using EFVS, a

missed approach must be initiated at or below DA or

MDA down to 100 feet above TDZE whenever the

pilot determines that:

(a)

The EFV is less than the visibility minima

prescribed for the IAP being used;

(b)

The required visual references for the run-

way of intended landing are no longer distinctly

visible and identifiable to the pilot using the EFVS

imagery;

(c)

The aircraft is not continuously in a posi-

tion from which a descent to a landing can be made

on the intended runway, at a normal rate of descent,

using normal maneuvers; or

(d)

For operations under 14 CFR parts 121

and 135, the descent rate of the aircraft would not

allow touchdown to occur within the TDZ of the

runway of intended landing.

5. Missed Approach Considerations.

It

should be noted that a missed approach after passing

the DA, or beyond the missed approach point (MAP),

involves additional risk until established on the pub-

lished missed approach segment. Initiating a

go−around after passing the published MAP may res-

ult in loss of obstacle clearance. As with any

approach, pilot planning should include contingen-

cies between the published MAP and touchdown with

reference to obstacle clearance, aircraft performance,

and alternate escape plans.

c. EFVS Operations At and Below 100 Feet

Above the TDZE.

At and below 100 feet above the

TDZE, the regulations do not require the EFVS to be

turned off or the display to be stowed in order to con-

tinue to a landing. A pilot may continue the approach