Aeronautical Information Manual (AIM), page 394

Index   393 -- Page 394 -- 395

radiometry, millimeter wave radar, and/or low light
level image intensifying. The EFVS imagery is
displayed along with the additional flight information
and aircraft flight symbology required by 14 CFR
91.175 (m) on a head-up display (HUD), or an
equivalent display, in the same scale and alignment as
the external view and includes the display element,
sensors, computers and power supplies, indications,
and controls. The display is typically presented to the
pilot by means of an approved HUD.

a. Basic Strategy Using EFVS. When flying an
instrument approach procedure (IAP), if the runway
environment cannot be visually acquired at decision
altitude (DA) or minimum descent altitude (MDA)
using natural vision, then a pilot may use an EFVS to
continue descending down to 100 feet above the
Touchdown Zone Elevation (TDZE), provided all of
the visibility requirements of 14 CFR part 91.175 (l)
are met. The primary reference for maneuvering the
aircraft is based on what the pilot sees through the
EFVS. At 100 feet above the TDZE, a pilot can con-

tinue to descend only when the visual reference

requirements for descent below 100 feet can be seen

using natural vision (without the aid of the EFVS). In

other words, a pilot may not continue to rely on the

EFVS sensor image to identify the required visual

references below 100 feet above the TDZE. Support-

ing information is provided by the flight path vector

(FPV), flight path angle (FPA) reference cue, on-

board navigation system, and other imagery and

flight symbology displayed on the EFVS. The FPV

and FPA reference cue, along with the EFVS imagery

of the Touchdown Zone (TDZ), provide the primary

vertical path reference for the pilot when vertical

guidance from a precision approach or approach with

vertical guidance is not available.

1. Straight-In Instrument Approach
Procedures. An EFVS may be used to descend
below DA or MDA from any straight-in IAP, other
than Category II or Category III approaches,
provided all of the requirements of 14 CFR part

91.175 (l) are met. This includes straight-in precision

approaches, approaches with vertical guidance (for

example, LPV or LNAV/VNAV), and non-precision

approaches (for example, VOR, NDB, LOC, RNAV,

GPS, LDA, SDF, etc.).

2. Circling Approach Procedure. An IAP
with a circle-to-land maneuver or circle-to-land
minimums does not meet criteria for straight-in

landing minimums. While the regulations do not
prohibit EFVS from being used during any phase of
flight, they do prohibit it from being used for
operational credit on anything but a straight-in IAP
with straight-in landing minima. EFVS must only be
used during a circle-to-land maneuver provided the
visual references required throughout the circling
maneuver are distinctly visible using natural vision.
An EFVS cannot be used to satisfy the requirement
that an identifiable part of the airport be distinctly
visible to the pilot during a circling maneuver at or
above MDA or while descending below MDA from
a circling maneuver.

3. Enhanced Flight Visibility. Flight visibility
is determined by using natural vision, and enhanced
flight visibility (EFV) is determined by using an
EFVS. 14 CFR part 91.175 (l) requires that the EFV
observed by using an EFVS cannot be less than the
visibility prescribed in the IAP to be used in order to
continue to descend below the DA or MDA.

b. EFVS Operations At or Below DA or MDA

Down to 100 Feet Above the TDZE. The visual

segment of an IAP begins at DA or MDA and contin-

ues to the runway. There are two means of operating

in the visual segment--one is by using natural vision

and the other is by using an EFVS. If the pilot determ-

ines that the EFV observed by using the EFVS is not

less than the minimum visibility prescribed in the IAP

being flown, and the pilot acquires the required visual

references prescribed in 14 CFR part 91.175 (l)(3) us-

ing the EFVS, then the pilot can continue the

approach to 100 feet above the TDZE. To continue

the approach, the pilot uses the EFVS image to visu-

ally acquire the runway environment (the approach

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:

5-4-58 Arrival Procedures

Page 394 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   393 -- Page 394 -- 395