NOT FOR NAVIGATION
NW-1, 1
NW-1, 18 NOV 2010 to 16
V 2010 to 16 DEC 2010
Figure 4-6. Procedures with circling landing minima.
if any crewmember is off the flight deck, all ATC
instructions are written down until his or her return
and then passed to that crewmember upon return.
Similarly, if a crewmember is off ATC frequency when
making a precision approach (PA) announcement
or when talking on company frequency, all ATC
instructions are briefed upon his or her return.
• Company policy should address use of speakers,
headsets, boom microphone, and/or hand-held
microphone.
• SOPs should state the altitude awareness company
policy on confirming assigned altitude.
Example: The PM acknowledges ATC altitude clearance. If
the aircraft is on the autopilot, then the PF makes input into
the autopilot/altitude alerter. PF points to the input while
stating the assigned altitude as he or she understands it.
The PM then points to the input stating aloud what he or
she understands the ATC clearance to be confirming that
the input and clearance match. If the aircraft is being hand-
flown, then the PM makes the input into the altitude alerter/
autopilot, then points to the input and states clearance.
PF then points to the alerter stating aloud what he or she
understands the ATC clearance to be confirming that the
alerter and clearance match.
Example: If there is no altitude alerter in the aircraft, then
both pilots write down the clearance, confirm that they
have the same altitude, and then cross off the previously
assigned altitude.
Approach Control
Approach control is responsible for controlling all
instrument flights operating within its area of responsibility.
Approach control may serve one or more airports. Control
is exercised primarily through direct pilot and controller
communication and airport surveillance radar (ASR). Prior
to arriving at the initial approach fix (IAF), instructions will
be received from the air route traffic control center (ARTCC)
to contact approach control on a specified frequency.
Where radar is approved for approach control service, it is
used not only for radar approaches, but also for vectors in
conjunction with published non-radar approaches using
conventional NAVAIDs or RNAV/GPS.
When radar handoffs are initiated between the ARTCC
and approach control, or between two approach control
facilities, aircraft are cleared (with vertical separation) to
an outer fix most appropriate to the route being flown
and, if required, given holding instructions. Or, aircraft
are cleared to the airport or to a fix so located that the
handoff is completed prior to the time the aircraft reaches
the fix. When radar handoffs are used, successive arriving
flights may be handed off to approach control with radar
separation in lieu of vertical separation.
After release to approach control, aircraft are vectored
to the final approach course. ATC occasionally vectors
the aircraft across the final approach course for spacing
requirements. The pilot is not expected to turn inbound
on the final approach course unless an approach clearance
has been issued. This clearance is normally issued with the
final vector for interception of the final approach course,
and the vector enables the pilot to establish the aircraft on
the final approach course prior to reaching the FAF.
Air Route Traffic Control Center (ARTCC)
ARTCCs are approved for and may provide approach
control services to specific airports. The radar systems used
by these centers do not provide the same precision as an
ASR or precision approach radar (PAR) used by approach
control facilities and control towers, and the update rate
is not as fast. Therefore, pilots may be requested to report
established on the final approach course. Whether aircraft
are vectored to the appropriate final approach course or
provide their own navigation on published routes to it,
radar service is automatically terminated when the landing
is completed; or when instructed to change to advisory
frequency at airports without an operating ATC tower,
whichever occurs first. When arriving on an IFR flight plan
at an airport with an operating control tower, the flight
plan is closed automatically upon landing.
The extent of services provided by approach control varies
greatly from location to location. The majority of Part 121
operations in the NAS use airports that have radar service
and approach control facilities to assist in the safe arrival
and departure of large numbers of aircraft. Many airports
do not have approach control facilities. It is important for
pilots to understand the differences between approaches
with and without an approach control facility. For example,
Figure 4-7. Durango approach and low altitude en route excerpt.
consider the Durango, Colorado, ILS DME RWY 2 and low
altitude en route chart excerpt shown in Figure 4-7.
High or Lack of Minimum Vectoring Altitudes
(MVAs)
Considering the fact that most modern commercial and
corporate aircraft are capable of direct, point-to-point flight,
it is increasingly important for pilots to understand the
limitations of ARTCC capabilities with regard to minimum
altitudes. There are many airports that are below the
coverage area of Center radar, and; therefore, off-route
transitions into the approach environment may require
that the aircraft be flown at a higher altitude than would
be required for an on-route transition. In the Durango
example, an airplane approaching from the northeast on
a direct route to the Durango VOR may be restricted to
a minimum IFR altitude (MIA) of 17,000 feet MSL due to
unavailability of Center radar coverage in that area at lower
altitudes. An arrival on V95 from the northeast would be
able to descend to a minimum en route altitude (MEA) of
12,000 feet, allowing a shallower transition to the approach
environment. An off-route arrival may necessitate a descent
into holding in order to avoid an unstable approach to
Durango.
Lack of Approach Control Terrain Advisories
Flight crews must understand that terrain clearance cannot
be assured by ATC when aircraft are operating at altitudes
that are not served by Center or approach radar. Recent
National Transportation Safety Board (NTSB) investigations
have identified several accidents that involved controlled
flight into terrain (CFIT) by IFR rated and VFR pilots
operating under visual flight conditions at night in remote
areas. In many of these cases, the pilots were in contact with
ATC at the time of the accident and receiving radar service.
The pilots and controllers involved all appear to have been
unaware that the aircraft were in danger. Increased altitude
awareness and better preflight planning would likely have
prevented all of these accidents. How can pilots avoid
becoming involved in a CFIT accident?
CFIT accidents are best avoided through proper preflight
planning.
• Terrain familiarization is critical to safe visual
operations at night. Use sectional charts or other
topographic references to ensure that your altitude
safely clears terrain and obstructions all along your
route.
• In remote areas, especially in overcast or moonless
conditions, be aware that darkness may render visual
avoidance of high terrain nearly impossible and that
the absence of ground lights may result in loss of
horizon reference.
• When planning a nighttime VFR flight, follow IFR
practices, such as climbing on a known safe course,
until well above surrounding terrain. Choose a
cruising altitude that provides terrain separation
similar to IFR flights (2,000 feet AGL in mountainous
areas and 1,000 feet above the ground in other areas.)
• When receiving radar services, do not depend on ATC
to warn you of terrain hazards. Although controllers
try to warn pilots if they notice a hazardous situation,
they may not always be able to recognize that a
particular VFR aircraft is dangerously close to terrain.
• When issued a heading along with an instruction to
“maintain VFR, ” be aware that the heading may not
provide adequate terrain clearance. If you have any
doubt about your ability to visually avoid terrain and
obstacles, advise ATC immediately and take action to
reach a safe altitude if necessary.
• ATC radar software can provide limited prediction and
warning of terrain hazards, but the warning system
is configured to protect IFR flights and is normally
suppressed for VFR aircraft. Controllers can activate
the warning system for VFR flights upon pilot request,
but it may produce numerous false alarms for aircraft
operating below the MIA, especially in en route center
airspace.
• If you fly at night, especially in remote or unlit areas,
consider whether a GPS-based terrain awareness unit
would improve your safety of flight.
• Lack of approach control traffic advisories—if radar
service is not available for the approach, the ability
of ATC to give flight crews accurate traffic advisories
is greatly diminished. In some cases, the common
traffic advisory frequency (CTAF) may be the only tool
available to enhance an IFR flight’s awareness of traffic
at the destination airport. Additionally, ATC will not
clear an IFR flight for an approach until the preceding
aircraft on the approach has cancelled IFR, either on
the ground, or airborne once in visual meteorological
conditions (VMC).
Airports With an ATC Tower
Control towers are responsible for the safe, orderly, and
expeditious flow of all traffic that is landing, taking off,
operating on and in the vicinity of an airport and, when
the responsibility has been delegated, towers also provide
for the separation of IFR aircraft in terminal areas. Aircraft
that are departing IFR are integrated into the departure
sequence by the tower. Prior to takeoff, the tower controller
coordinates with departure control to assure adequate
aircraft spacing.
Airports Without A Control Tower
From a communications standpoint, executing an
instrument approach to an airport that is not served by an
ATC tower requires more attention and care than making
a visual approach to that airport. Pilots are expected to
self-announce their arrival into the vicinity of the airport
no later than 10 NM from the field. Depending on the
weather, as well as the amount and type of conflicting
traffic that exists in the area, an approach to an airport
without an operating ATC tower increases the difficulty of
the transition to visual flight.
In many cases, a flight arriving via an instrument approach
needs to mix in with VFR traffic operating in the vicinity
of the field. For this reason, many companies require that
flight crews make contact with the arrival airport CTAF or
company operations personnel via a secondary radio over
25 NM from the field in order to receive traffic advisories.
In addition, pilots should attempt to listen to the CTAF
well in advance of their arrival in order to determine the
VFR traffic situation.
NOT FOR NAVIGATION
Since separation cannot be provided by ATC between
IFR and VFR traffic when operating in areas where there
is no radar coverage, pilots are expected to make radio
announcements on the CTAF. These announcements
allow other aircraft operating in the vicinity to plan their
departures and arrivals with a minimum of conflicts.
In addition, it is very important for crews to maintain a
listening watch on the CTAF to increase their awareness
of the current traffic situation. Flights inbound on an
instrument approach to a field without a control tower
should make several self-announced radio calls during
the approach:
• Initial call within 4-10 minutes of the aircraft’s arrival
at the IAF. This call should give the aircraft’s location
as well as the crew’s approach intentions.
• Departing the IAF, stating the approach that is being
initiated.
• Procedure turn (or equivalent) inbound.
• FAF inbound, stating intended landing runway and
maneuvering direction if circling.
• Short final, giving traffic on the surface notification
of imminent landing.
When operating on an IFR flight plan at an airport without
a functioning control tower, pilots must initiate cancellation
of the IFR flight plan with ATC or an AFSS. Remote
communications outlets (RCOs) or ground communications
outlets (GCOs), if available, can be used to contact an ARTCC
or an AFSS after landing. If a frequency is not available on
NW-1, 18 NOV 2010 to 16 DEC 2010
NW-1, 18 NOV 2010 to 16 DEC 2010
Figure 4-8. Cheyenne Regional (KCYS), Cheyenne, Wyoming, ILS or LOC RWY 27.
the ground, the pilot has the option to cancel IFR while
in flight if VFR conditions can be maintained while in
contact with ARTCC, as long as those conditions can be
maintained until landing. Additionally, pilots can relay a
message through another aircraft or contact flight service
via telephone.
Primary NAVAID
Most conventional approach procedures are built around
a primary final approach NAVAID; others, such as RNAV
(GPS) approaches, are not. If a primary NAVAID exists for
an approach, it should be included in the IAP briefing, set
into the appropriate backup or active navigation radio, and
positively identified at some point prior to being used for
course guidance. Adequate thought should be given to the
appropriate transition point for changing from FMS or other
en route navigation over to the conventional navigation to
be used on the approach. Specific company standards and
procedures normally dictate when this changeover occurs;
some carriers are authorized to use FMS course guidance
throughout the approach, provided that an indication
of the conventional navigation guidance is available
and displayed. Many carriers, or specific carrier fleets,
are required to change over from RNAV to conventional
navigation prior to the FAF of an instrument approach.
Depending on the complexity of the approach procedure,
pilots may have to brief the transition from an initial NAVAID
to the primary and missed approach NAVAIDs. Figure 4-8
shows the Cheyenne, Wyoming, ILS Runway 27 approach
procedure, which requires additional consideration during
an IAP briefing.
If the 15 DME arc of the CYS VOR is to be used as the
transition to this ILS approach procedure, caution must
be paid to the transition from en route navigation to the
initial NAVAID and then to the primary NAVAID for the ILS
approach. Planning when the transition to each of these
NAVAIDs occurs may prevent the use of the incorrect
NAVAID for course guidance during approaches where
high pilot workloads already exist.
Equipment Requirements
The navigation equipment that is required to join and fly an
IAP is indicated by the title of the procedure and notes on
the chart. Straight-in IAPs are identified by the navigation
system by providing the final approach guidance and the
runway with which the approach is aligned (for example,
VOR RWY 13). Circling-only approaches are identified
by the navigation system by providing final approach
guidance and a letter (for example, VOR A). More than one
navigation system separated by a slant indicates that more
than one type of equipment must be used to execute the
final approach (for example, VOR/DME RWY 31). More than
one navigation system separated by the word“or”indicates
either type of equipment can be used to execute the final
approach (for example, VOR or GPS RWY 15).
In some cases, other types of navigation systems,
including radar, are required to execute other portions of
the approach or to navigate to the IAF (for example, an
NDB procedure turn to an ILS, or an NDB in the missed
approach, or radar required to join the procedure or identify
a fix). When ATC radar or other equipment is required for
procedure entry from the en route environment, a note is
charted in the plan view of the approach procedure chart
(for example, RADAR REQUIRED or AUTOMATIC DIRECTION
FINDER (ADF) REQUIRED). When radar or other equipment
is required on portions of the procedure outside the final
approach segment, including the missed approach, a note
is charted in the notes box of the pilot briefing portion
of the approach chart (for example, RADAR REQUIRED or
DISTANCE MEASURING EQUIPMENT (DME) REQUIRED).
Notes are not charted when VOR is required outside the
final approach segment. Pilots should ensure that the
aircraft is equipped with the required NAVAIDs to execute
the approach, including the missed approach. Refer to the
AIM paragraph 5-4-5 for additional options with regards to
equipment requirements for IAPs.
RNAV systems may be used as a Substitute Means of
Navigation when a very high frequency (VHF) Omni-
directional Range (VOR), Distance Measuring Equipment
(DME), Tactical Air Navigation (TACAN), VOR/TACAN
(VORTAC), VOR/DME, non-directional radio beacon (NDB),
or compass locator facility including locator outer marker
and locator middle marker is out-of-service, i.e., the
Navigation Aid (NAVAID) information is not available; an
aircraft is not equipped with an automatic direction finder
(ADF) or DME; or the installed ADF or DME on an aircraft is
not operational. For example, if equipped with a suitable
RNAV system, a pilot may hold over an out-of-service NDB.
Refer to Advisory Circular 90-108, Use of Suitable RNAV
System on Conventional Routes and Procedures, dated
March 3, 2011 for additional guidance on the proper times
and procedures for substituting a RNAV system for means
of navigation.
Courses
Traditional Courses
An aircraft that has been cleared to a holding fix and
subsequently “cleared…approach, ” normally does not
receive new routing. Even though clearance for the
approach may have been issued prior to the aircraft
reaching the holding fix, ATC would expect the pilot to
proceed via the holding fix that was the last assigned route,
and the feeder route associated with that fix, if a feeder
route is published on the approach chart, to the IAF to
commence the approach. When cleared for the approach,
the published off-airway (feeder) routes that lead from
the en route structure to the IAF are part of the approach
clearance.
If a feeder route to an IAF begins at a fix located along
the route of flight prior to reaching the holding fix,
and clearance for an approach is issued, a pilot should
commence the approach via the published feeder route.
For example, the aircraft would not be expected to overfly
the feeder route and return to it. The pilot is expected to
commence the approach in a similar manner at the IAF,
if the IAF for the procedure is located along the route of
flight to the holding fix.
If a route of flight directly to the IAF is desired, it should
be so stated by the controller with phraseology to include
the words “direct, ” “proceed direct, ” or a similar phrase
that the pilot can interpret without question. When a
pilot is uncertain of the clearance, ATC should be queried
immediately as to what route of flight is preferred.
The name of an instrument approach, as published, is
used to identify the approach, even if a component of the
approach aid is inoperative or unreliable. The controller
will use the name of the approach as published, but must
advise the aircraft at the time an approach clearance is
issued that the inoperative or unreliable approach aid
component is unusable. (Example: “Cleared ILS RWY 4,
glideslope unusable. ”)
Area Navigation Courses
RNAV (GPS) approach procedures introduce their own
tracking issues because they are flown using an onboard
navigation database. They may be flown as coupled
approaches or flown manually. In either case, navigation
system coding is based on procedure design, including
waypoint (WP) sequencing for an approach and missed
approach. The procedure design indicates whether the WP
is a fly-over (FO) or fly-by (FB), and provides appropriate
guidance for each. A FB WP requires the use of turn
anticipation to avoid overshooting the next flight segment.
A FO WP precludes any turn until the WP is over flown and
is followed by either an intercept maneuver of the next
flight segment or direct flight to the next WP .
Figure 4-9. Fly-by and fly-over waypoints.
Approach waypoints, except for the missed approach
waypoint (MAWP) and the missed approach holding
waypoint (MAHWP), are normally FB WPs. Notice that in the
plan view in Figure 4-9, there are four FB WPs, but only the
circled WP symbol at PRINO is a FO WP . If flying manually to
a selected RNAV WP , pilots should anticipate the turn at a FB
WP to ensure a smooth transition and avoid overshooting
the next flight segment. Alternatively, for a FO WP , no turn
is accomplished until the aircraft passes the WP .
There are circumstances when a WP may be coded into the
database as both a FB WP and a FO WP , depending on how
the WPs are sequenced during the approach procedure. For
example, a WP that serves as an IAF may be coded as a FB
WP for the approach and as a FO WP when it also serves
as the MAWP for the missed approach procedure (MAP).
This is just one reason why instrument approaches should
be loaded in their entirety from the FMS and not manually
built or modified.
Altitudes
Prescribed altitudes may be depicted in four different
configurations: minimum, maximum, recommended, and
mandatory. The U.S. Government distributes approach
charts produced by the FAA. Altitudes are depicted on
these charts in the profile view with an underscore or
overscore, or both to identify them as minimum, maximum,
or mandatory, respectively.
• Minimum altitudes are depicted with the altitude value
underscored. Aircraft are required to maintain altitude
at or above the depicted value (e.g., 3000).
• Maximum altitudes are depicted with the altitude value
overscored. Aircraft are required to maintain altitude
at or below the depicted value (e.g., 4800).
• Mandatory altitudes are depicted with the altitude value
both underscored and overscored. Aircraft are required
to maintain altitude at the depicted value (e.g., 5500).
• Recommended altitudes are depicted without an
underscore or overscore.
Note: Pilots are cautioned to adhere to altitudes as
prescribed because, in certain instances, they may be used
as the basis for vertical separation of aircraft by ATC. If a
depicted altitude is specified in the ATC clearance, that
altitude becomes mandatory as defined above.
Minimum Safe/Sector Altitude
Minimum Safe Altitudes are published for emergency use
on IAP charts. MSAs provide 1,000 feet of clearance over
all obstacles but do not necessarily assure acceptable
navigation signal coverage. The MSA depiction on the plan
view of an approach chart contains the identifier of the
center point of the MSA, the applicable radius of the MSA,
a depiction of the sector(s), and the minimum altitudes
above mean sea level which provide obstacle clearance.
For conventional navigation systems, the MSA is normally
based on the primary omnidirectional facility on which the
IAP is predicated, but may be based on the airport reference
point (ARP) if no suitable facility is available. For RNAV
approaches, the MSA is based on an RNAV waypoint. MSAs
normally have a 25 NM radius; however, for conventional
navigation systems, this radius may be expanded to 30 NM
if necessary to encompass the airport landing surfaces.
Depicted on the Plan View of approach charts, a single
sector altitude is normally established. However when it is
necessary to obtain obstacle clearance, an MSA area may
be further divided with up to four sectors.
Final Approach Fix Altitude
Another important altitude that should be briefed during
an IAP briefing is the FAF altitude, designated by the cross
on a non-precision approach, and the lightning bolt symbol
designating the glideslope/glidepath intercept altitude on
a precision approach. Adherence and cross-check of this
altitude can have a direct effect on the success and safety
of an approach.
Proper airspeed, altitude, and configuration, when crossing
the FAF of a non-precision approach, are extremely
important no matter what type of aircraft is being flown.
The stabilized approach concept, implemented by the
FAA within the SOPs of each air carrier, suggests that
crossing the FAF at the published altitude is often a critical
component of a successful non-precision approach,
especially in a large turbojet aircraft.
The glideslope intercept altitude of a precision approach
should also be included in the IAP briefing. Awareness of
this altitude when intercepting the glideslope can ensure
the flight crew that a “false glideslope” or other erroneous
indication is not inadvertently followed. Many air carriers
include a standard callout when the aircraft passes over the
FAF of the non-precision approach underlying the ILS. The
PM states the name of the fix and the charted glideslope
altitude, thus allowing both pilots to cross-check their
respective altimeters and verify the correct indications.
Minimum Descent Altitude (MDA), Decision
Altitude (DA), And Decision Height (DH)
MDA—the lowest altitude, expressed in feet MSL, to which
descent is authorized on final approach or during circle-to
land maneuvering in execution of a standard instrument
approach procedure (SIAP) where no electronic glideslope
is provided.
DA—a specified altitude in the precision approach at
which a missed approach must be initiated if the required
visual reference to continue the approach has not been
established.
DH—with respect to the operation of aircraft, means the
height at which a decision must be made during an ILS, MLS,
or PAR IAP to either continue the approach or to execute a
missed approach.
CAT II and III approach DHs are referenced to AGL and
measured with a radio altimeter.
The height above touchdown (HAT) for a CAT I precision
approach is normally 200 feet above touchdown zone
elevation (TDZE). When a HAT of 250 feet or higher is
published, it may be the result of the signal-in-space
coverage, or there may be penetrations of either the final
or missed approach obstacle clearance surfaces (OCSs).
If there are OCS penetrations, the pilot has no indication
on the approach chart where the obstacles are located. It
is important for pilots to brief the MDA, DA, or DH so that
there is no ambiguity as to what minimums are being used.
These altitudes can be restricted by many factors. Approach
category, inoperative equipment in the aircraft or on the
ground, crew qualifications, and company authorizations
are all examples of issues that may limit or change the
height of a published MDA, DA, or DH.
For many air carriers, OpSpecs may be the limiting factor
for some types of approaches. NDB and circling approaches
are two common examples where the OpSpecs minimum
listed altitudes may be more restrictive than the published
minimums. Many Part 121 and 135 operators are restricted
from conducting circling approaches below 1,000 feet
MDA and 3 SM visibility by Part C of their OpSpecs,
and many have specific visibility criteria listed for NDB
approaches that exceed visibilities published for the
approach (commonly 2 SM). In these cases, flight crews
must determine which is the more restrictive of the two
and comply with those minimums.
In some cases, flight crew qualifications can be the limiting
factor for the MDA, DA, or DH for an instrument approach.
There are many CAT II and III approach procedures
authorized at airports throughout the United States, but
RNP AR restricts their use to pilots who have received
specific training, and aircraft that are equipped and
authorized to conduct those approaches. Other rules
pertaining to flight crew qualifications can also determine
the lowest usable MDA, DA, or DH for a specific approach.
14 CFR Part 121, § 121.652, 14 CFR Part 125, § 125.379,
and 14 CFR Part 135, § 135.225 require that some PICs,
with limited experience in the aircraft they are operating,
increase the approach minimums and visibility by 100
feet and one-half mile respectively. Rules for these “high
minimums” pilots are usually derived from a combination
of federal regulations and the company’s OpSpecs. There
are many factors that can determine the actual minimums
that can be used for a specific approach. All of them must
be considered by pilots during the preflight and approach
planning phases, discussed, and briefed appropriately.
Pilots are cautioned to fully understand and abide by the
guidelines set forth in 14 CFR § 91.175(c) regarding proper
identification of the runway and runway environment when
electing to continue any approach beyond the published
DA/DH or MDA.
It is imperative to recognize that any delay in making a
decision to execute the Missed Approach Procedure at
the DA/DH or MDA/Missed Approach Point will put the
aircrew at risk of impacting any obstructions that may be
penetrating the visual obstacle clearance surface
The visual segment of an IAP begins at DA or MDA and
continues to the runway. There are two means of operating
in the visual segment, one is by using natural vision under
14 CFR Part 91, § 91.175 (c) and the other is by using an
Enhanced Flight Vision System under 14 CFR Part 91, §
91.176.
Figure 4-10A. View during an approach with EFVS (left) and
without
EFVS (right). (Images courtesy of NASA Langley
Research Center)
Enhanced Fligh t Vi sion Systems (EFVS) and
nstrument Approaches [Figure 4-10A]
n Enhanced Flight Vision System (EFVS) is an installed
aircraft system which uses a head up display (HUD), or an
equivalent display that is a head up presentation, to combine
air
craft flight information and flight symbology, navigation
guidanc
e, and a real-time image of the external scene to
the
pilot on a single display. Imaging sensors, which may
be based on forward-looking infrared ( FLIR), millimeter
wave radiometry, millimeter wave radar, low-level light
in
tensification, o r o ther real-time i maging technologies,
produce a real-time image of the outside scene. Combining
the flight information, navigation guidance, and sensor
imagery on a HUD or equivalent display allows the pilot to
continue looking forward along the flightpath throughout
the entire approach, landing, and rollout.
Sections 91.175(c) and 91.176 specify two means of operating
visually below DA/DH or MDA in the visual segment of an
IAP . One means is by using natural vision under § 91.175(c),
and the other is by using enhanced vision provided by an
EFVS under § 91.176. When the runway environment cannot
be visually acquired using natural vision, a pilot may use an
EFVS to continue descending below DA/DH or MDA under §
91.176. An EFVS operation is an operation in which visibility
conditions require an EFVS to be used in lieu of natural vision
to perform an approach or landing, determine enhanced
flight visibility, identify required visual references, or conduct
a rollout. There are two types of EFVS operations – EFVS
operations to touchdown and rollout and EFVS operations
to 100 feet above the touchdown zone elevation (TDZE). An
EFVS operation to touchdown and rollout is an operation in
which a pilot uses the enhanced vision imagery provided by
an EFVS in lieu of natural vision to descend below DA or DH to
touchdown and rollout [Figure 4-10B]. These operations may
be conducted on standard instrument approach procedures
(SIAPs) or special instrument approach procedures (IAPs) that
have a DA or DH (e.g., Precision or APV approach).
Figure 4-10B. EFVS Operation to Touchdown and Rollout.
An EFVS operation to 100 feet above the TDZE is an
operation in which the pilot uses the EFVS in lieu of natural
vision to descend below DA/DH or MDA down to 100 feet
above the TDZE [Figure 4-10C]. To descend below 100 feet
above the TDZE, however, natural vision must be used. EFVS
operations to 100 feet above the TDZE may be conducted
on SIAPs or special IAPs that have a DA/DH or MDA.
While the regulations do not prohibit EFVS from being used
during any phase of flight for situational awareness, EFVS
displays are not designed, installed, certified, or intended
as a sufficient visual system to conduct circling maneuvers.
EFVS may only be used during a circle-to-land maneuver
provided the visual references required throughout the
circling maneuver are distinctly visible to the pilot using
natural vision throughout the circling maneuver. Therefore,
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.
The visual information provided by an EFVS serves as
independent verification of the position information
provided by the aircraft’s displays and systems. An EFVS
also enables a pilot to assess the enhanced flight visibility
and identify required visual references, helps a pilot align
the aircraft with the runway, and provides position, roll, rate
of closure, and distance remaining information. Sections
91.176(a) and 91.176(b) permit a pilot to use an EFVS to
identify the required visual references and to determine
that the enhanced flight visibility provided by the EFVS is
not less than the visibility prescribed in the IAP to be flown.
Both the visual reference and enhanced flight visibility
requirements of the regulations must be met before the
pilot can descend below DA/DH during an EFVS operation
to touchdown and rollout or below DA/DH or MDA during
an EFVS operation to 100 feet above the TDZE. The aircraft
also must continuously be in a position from which a
descent to landing can be made on the intended runway at
a normal rate of descent using normal maneuvers. For EFVS
operations to touchdown, § 91.176(a)(2)(vi) requires that
the descent rate must allow touchdown to occur within the
touchdown zone of the runway of intended landing for all
operations. Section 91.176(b)(2)(v), operations conducted
to 100 feet above the TDZE, requires the descent rate to
allow touchdown to occur within the touchdown zone of
the runway of intended landing for operations conducted
under 14 CFR Parts 121 and 135.
Figure 4-10C. EFVS Operations to 100 Feet Above the TDZE.
t is important to understand that using an EFVS does not
esult in obtaining lower minima with respect to the visibility
or the DA/DH or MDA specified in the IA P . For example, a
pilot who is using an EFVS on a Category I ILS approach that
specifies
a DA of 200 feet and a required visibility of RVR 2400
eet must comply with a 200-foot DA and an enhanced flight
visibilit
y of 2400 feet, even though the pilot may not have
2400 feet of flight visibility using natural vision or a reported
o 16 DEC 2010
OV 20
visibility of RVR 2400 feet. The decision altitude is specified
by the IAP the pilot is flying, and it does not change whether
EFVS is used or not. Accordingly, the visibility specified in
the IAP does not change. The difference is whether the pilot
assesses the RVR 2400 feet visibility prescribed by the IAP
using natural vision or whether he or she assesses it using an
EFVS. An EFVS simply provides another means of operating
in the visual segment of an IAP . That is, it gives the pilot
another means to see the required visual references when
they might not be visible using natural vision, and it gives
the pilot a means to see forward along the flightpath the
distance required by the enhanced flight visibility – when
he or she might not be able to do so using natural vision.
During an EFVS operation, a pilot must initiate a go-around
at or below DA/DH or MDA whenever the requirements
of § 91.176 are not met. The published missed approach
procedure provides obstacle clearance only when the
missed approach is initiated from or above the DA/DH, or
at the MAP . It assumes a climb rate of 200 fT/NM unless a
higher climb gradient is identified on the procedure. If a
pilot initiates a go-around at a point below DA/DH or after
the MAP , obstacle clearance is not necessarily provided by
following the published missed approach procedure. Prior
planning is recommended and should include contingencies
between the published MAP and touchdown with reference
to obstacle clearance, aircraft performance, and alternate
escape plans. Additionally, pilots should be especially
knowledgeable of the approach conditions and approach
course alignment when considering whether to rely on
EFVS during an instrument approach with an offset final
approach course. Depending upon the combination of
crosswind correction, approach course offset, 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 upon reaching the MAP . AC
90-106 (current version) contains additional information
about visual segment obstacle clearance, missed approach
obstacle clearance, and considerations associated with offset
approaches.
Operators that have a specific approval from the FAA to
conduct special IAPs should evaluate those instrument
procedures to determine their compatibility with EFVS
operations. Special IAPs are frequently dependent on the
ability of the operator to meet certain requirements that
may include aircraft performance, equipage, airport facility
equipment, crew training, or other requirements. These
EC-2, 18 N
NOT FOR NAVIGATION
Figure 4-11A. VNAV information.
procedures also may have nonstandard features such as
nonstandard final approach course alignment, nonstandard
descent gradients, or other features that may or may not be
compatible with the conduct of EFVS operations.
Under § 91.176(a), operators who have been issued OpSpec
C073, MSpec MC073, or LOA C073, may conduct EFVS
operations to touchdown and rollout on certain vertical
navigation (VNAV) IAPs that use an MDA as a DA/DH in
accordance with C073. Additionally, §§ 91.176 and 91.189
permit an authorized EFVS operation to be conducted
during an authorized Category II or Category III operation.
Currently, EFVS operations in rotorcraft can be conducted
only on IAPs that are flown to a runway. Instrument approach
criteria, procedures, and appropriate visual references have
not yet been developed for straight-in landing operations
below DA/DH or MDA under IFR to heliports or platforms.
EFVS cannot be used in lieu of natural vision to descend
below published minimums on copter approaches to a
point-in-space (PinS) followed by a “proceed visual flight
rules (VFR)” visual segment, or on approaches designed
to a specific landing site using a “proceed visually” visual
segment.
Vertical Navigation
One of the advantages of some GPS and multi-sensor FMS
RNAV avionics is the advisory VNAV capability. Traditionally,
the only way to get vertical path information during an
approach was to use a ground-based precision NAVAID.
Modern RNAV avionics can display an electronic vertical
path that provides a constant-rate descent to minimums.
Since these systems are advisory and not primary guidance,
the pilot must continuously ensure the aircraft remains at
or above any published altitude constraint, including step
down fix altitudes, using the primary barometric altimeter.
The pilots, aircraft, and operator must be approved to use
advisory VNAV inside the FAF on an instrument approach.
VNAV information appears on selected conventional
nonprecision, GPS, and RNAV approaches (see “Types of
Approaches” later in this chapter). It normally consists of
two fixes (the FAF and the landing runway threshold), a
FAF crossing altitude, a vertical descent angle (VDA), and
may provide a visual descent point (VDP) [Figure 4-11A].
The VDA provides the pilot with advisory information
not previously available on nonprecision approaches. It
provides a means for the pilot to establish a stabilized
descent from the FAF or step-down fix to the MDA.
Stabilized descent is a key factor in the reduction of
controlled flight into terrain (CFIT) incidents. However,
pilots should be aware that the published angle is for
information only − it is strictly advisory in nature. There is
no implicit additional obstacle protection below the MDA.
Pilots must still respect any published stepdown fixes and
the published MDA unless the visual cues stated 14 CFR
§ 91.175 are present, and they can visually acquire and
avoid both lit and unlit obstacles once below the MDA. The
presence of a VDA does not guarantee obstacle protection
in the visual segment and does not change any of the
requirements for flying a nonprecision approach.
Pilots may use the published angle and estimated/actual
groundspeed to find a target rate of descent from the rate
of descent table published in the back of the U.S. Terminal
Procedures Publication. This rate of descent can be flown
with the Vertical Velocity Indicator (VVI) in order to use
the VDA as an aid to flying a stabilized descent. No special
equipment is required.
In rare cases, the LNAV minima may have a lower HAT
than minima with a glide path, due to the location of the
obstacles and the nonprecision MAP . This should serve as
a clear indication to the pilot that obstacles exist below
the MDA, which must be seen in order to ensure adequate
clearance. In those cases, the glide path may be treated
as a VDA and used to descend to the LNAV MDA, as long
as all of the rules for a nonprecision approach are applied
at the MDA.
When there are obstacles in the visual area that could
cause an aircraft to destabilize the approach between
the MDA and touchdown, the IAP will not show a vertical
descent angle in the profile view. The charts currently
include the following statement: “Descent Angle NA” or
“Descent Angle NA-Obstacles” [Figure 4-11B ].
Figure 4-11B. Descent Angle N/A..
Figure 4-12. RNAV GPS approach minima.