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AIM 

4/20/23

 

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Navigation Aids

[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 order, 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 capability that allows the operator to proceed
safely and land at a different airport, 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 a 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]

To satisfy the requirement for two independent navigation systems, 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 consisting of 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

(a)

Conduct GPS IFR operations in oceanic areas only when approved avionics systems are installed.

TSO

C196() users and TSO

C129() GPS users authorized for Class A1, A2, B1, B2, C1, or C2 operations may

use GPS in place of another approved means of long

range navigation, such as dual INS. (See TBL 1

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and TBL 1

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6.) Aircraft with a single installation GPS, meeting the above specifications, are authorized to

operate on short oceanic routes requiring one means of long

range navigation (reference AC 20-138, Appendix

1).