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[b]  Inflight:

[1]

Determine that the waypoints and transition names coincide with names
found on the

procedure chart. Do not use waypoints which do not exactly match the
spelling shown on published procedure

charts.

[2]

 Determine that the waypoints are logical in location, in the correct o
rder, and their

orientation to each other is as found on the procedure chart, both
laterally and vertically.

NOTE

-

There is no specific requirement to check each waypoint latitude and
longitude, type of waypoint and/or altitude constraint,

only the general relationship of waypoints in the procedure, or the
logic of an individual waypoint's location.

[3]

If the cursory check of procedure logic or individual waypoint
location, specified in [b]

above, indicates a potential error, do not use the retrieved procedure
or waypoint until a verification of latitude

and longitude, waypoint type, and altitude constraints indicate full
conformity with the published data.

(5)

Air carrier and commercial operators must meet the appropriate
provisions of their approved

operations specifications.

[a]

During domestic operations for commerce or for hire, operators must
have a second navigation

system capable of reversion or contingency operations.

[b]

Operators must have two independent navigation systems appropriate to
the route to be flown

or one system that is suitable and a second, independent backup system
that allows the operator to proceed safely

to a suitable airport, complete an instrument approach; and the
aircraft must have sufficient fuel (reference 14

CFR 121.349, 125.203, 129.17, and 135.165). These rules ensure the
safety of the operation by preventing a

single point of failure.

NOTE

-

An aircraft approved for multi-sensor navigation and equipped with a
single navigation system must maintain an ability to

navigate or proceed safely in the event that any one component of
the navigation system fails, including the flight

management system (FMS). Retaining an FMS-independent VOR capability
would satisfy this requirement.

[c]

The requirements for a second system apply to the entire set of
equipment needed to achieve the

navigation capability, not just the individual components of the system
such as the radio navigation receiver. For

example, to use two RNAV systems (e.g., GPS and DME/DME/IRU) to comply
with the requirements, the

aircraft must be equipped with two independent radio navigation
receivers and two independent navigation

computers (e.g., flight management systems (FMS)). Alternatively, to
comply with the requirements using a

single RNAV system with an installed and operable VOR capability, the
VOR capability must be independent

of the FMS.

[d]

Due to low risk of disruption or manipulation of GPS signals beyond 50
NM offshore, FAA

differentiates between extended and non

-

extended over-water operations. To satisfy the requirement for two

independent navigation systems:

[1]

For all extended over-water operations (defined in 14 CFR Part 1 as
greater than 50 NM from

the nearest shoreline), operators may consider dual GPS

-

based systems to meet the "independent" criteria

stipulated by regulation, e.g., 121.349, 135.165.

[2]

For all "non

-

extended overwater" operations, if the primary navigation system is

GPS-based, the second system must be independent of GPS (for example,
VOR or DME/DME/IRU). This allows

continued navigation in case of failure of the GPS or WAAS services.
Recognizing that GPS interference and

test events resulting in the loss of GPS services have become more
common, the FAA requires operators

conducting IFR operations under 14 CFR 121.349, 125.203, 129.17, and
135.65 to retain a non

-

GPS navigation

capability, for example, either DME/DME, IRU, or VOR for en route and
terminal operations and VOR and ILS

for final approach. Since this system is to be used as a reversionary
capability, single equipage is sufficient.

3.  Oceanic, Domestic, En Route, and Terminal Area Operations

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Navigation Aids