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AIM

10/12/17

1

−1−21

Navigation Aids

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
sufficient.

3. O c e a n i c,  D o m e s t i c ,  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

−1−5 and TBL 1−1−6.) Aircraft with a

single installation GPS, meeting the above specifica-
tions, are authorized to operate on short oceanic
routes requiring one means of long

−range navigation

(reference AC 20-138, Appendix 1).

(b)

Conduct GPS domestic, en route, and

terminal IFR operations only when approved
avionics systems are installed. Pilots may use GPS
via TSO

−C129() authorized for Class A1, B1, B3,

C1, or C3 operations GPS via TSO-C196(); or
GPS/WAAS with either TSO-C145() or
TSO-C146(). When using TSO-C129() or
TSO-C196() receivers, the avionics necessary to
receive all of the ground

−based facilities appropriate

for the route to the destination airport and any
required alternate airport must be installed and
operational. Ground

−based facilities necessary for

these routes must be operational.

(1)

GPS en route IFR operations may be

conducted in Alaska outside the operational service
volume of ground

−based navigation aids when a

TSO

−C145() or TSO−C146() GPS/wide area aug-

mentation system (WAAS) system is installed and
operating. WAAS is the U.S. version of a
satellite-based augmentation system (SBAS).

[a]

In Alaska, aircraft may operate on

GNSS Q-routes with GPS (TSO-C129 () or
TSO-C196 ()) equipment while the aircraft remains
in Air Traffic Control (ATC) radar surveillance or
with GPS/WAAS (TSO-C145 () or TSO-C146 ())
which does not require ATC radar surveillance.

[b]

In Alaska, aircraft may only operate

on GNSS T-routes with GPS/WAAS (TSO-C145 () or
TSO-C146 ()) equipment.

(2)

Ground

−based navigation equipment

is not required to be installed and operating for en
route IFR operations when using GPS/WAAS
navigation systems. All operators should ensure that
an alternate means of navigation is available in the
unlikely event the GPS/WAAS navigation system
becomes inoperative.

(3)

Q-routes and T-routes outside Alaska.

Q-routes require system performance currently met
by GPS, GPS/WAAS, or DME/DME/IRU RNAV
systems that satisfy the criteria discussed in AC
90

−100, U.S. Terminal and En Route Area

Navigation (RNAV) Operations. T-routes require
GPS or GPS/WAAS equipment.

REFERENCE

AIM, Paragraph 5

−3−4 , Airways and Route Systems

(c)

GPS IFR approach/departure operations

can be conducted when approved avionics systems
are installed and the following requirements are met:

(1)

The aircraft is TSO

−C145() or TSO−

C146() or TSO

−C196() or TSO−C129() in Class A1,

B1, B3, C1, or C3; and

(2)

The approach/departure must be re-

trievable from the current airborne navigation
database in the navigation computer. The system
must be able to retrieve the procedure by name from
the aircraft navigation database. Manual entry of
waypoints using latitude/longitude or place/bearing
is not permitted for approach procedures.

(3)

The authorization to fly instrument

approaches/departures with GPS is limited to U.S.
airspace.

(4)

The use of GPS in any other airspace

must be expressly authorized by the FAA Adminis-
trator.