Aeronautical Information Manual (AIM), page 73

Index   72 -- Page 73 -- 74

manually entered series of waypoints. Manual entry
of waypoints using latitude/longitude or place/bear-
ing is not permitted for approach procedures.

(4) Prior to using a procedure or waypoint
retrieved from the airborne navigation database, the
pilot should verify the validity of the database. This
verification should include the following preflight
and inflight steps:
[a] Preflight:

[1] Determine the date of database
issuance, and verify that the date/time of proposed
use is before the expiration date/time.

[2] Verify that the database provider
has not published a notice limiting the use of the

specific waypoint or procedure.

[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.

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

[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 com-
merce or for hire, operators must have a second
navigation system capable of reversion or contin-
gency operations.

[b] Operators must have two independ-
ent 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.
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-inde-
pendent 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 conduct-

ing 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

3. Oceanic, Domestic, En Route, and
Terminal Area Operations
(a) Conduct GPS IFR operations in oceanic
areas only when approved avionics systems are

Navigation Aids 1-1-19

Page 73 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   72 -- Page 73 -- 74