Aeronautical Information Manual (AIM)

AIM

4/3/14

1−1−17

Navigation Aids

NOTE

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DO NOT attempt to fly a procedure that is NOTAMed out
of service even if the identification is present. In certain
cases, the identification may be transmitted for short
periods as part of the testing.

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13. NAVAIDs with Voice

Voice equipped en route radio navigational aids

are under the operational control of either a Flight

Service Station (FSS) or an approach control facility.

The voice communication is available on some

facilities. Hazardous Inflight Weather Advisory

Service (HIWAS) broadcast capability is available on

selected VOR sites throughout the conterminous U.S.

and does not provide two-way voice communication.

The availability of two-way voice communication

and HIWAS is indicated in the A/FD and aeronautical

charts.

Unless otherwise noted on the chart, all radio

navigation aids operate continuously except during

shutdowns for maintenance. Hours of operation of

facilities not operating continuously are annotated on

charts and in the A/FD.

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14. User Reports Requested on

NAVAID or Global Navigation Satellite
System (GNSS) Performance or
Interference

Users of the National Airspace System (NAS)

can render valuable assistance in the early correction

of NAVAID malfunctions or GNSS problems and are

encouraged to report their observations of undesir-

able performance. Although NAVAIDs are

monitored by electronic detectors, adverse effects of

electronic interference, new obstructions or changes

in terrain near the NAVAID can exist without

detection by the ground monitors. Some of the

characteristics of malfunction or deteriorating

performance which should be reported are: erratic

course or bearing indications; intermittent, or full,

flag alarm; garbled, missing or obviously improper

coded identification; poor quality communications

reception; or, in the case of frequency interference, an

audible hum or tone accompanying radio communic-

ations or NAVAID identification. GNSS problems are

often characterized by navigation degradation or

service loss indications.

Reporters should identify the NAVAID (for

example, VOR) malfunction or GNSS problem,

location of the aircraft (i.e., latitude, longitude or

bearing/distance from a NAVAID), altitude, date and

time of the observation, type of aircraft and

description of the condition observed, and the type of

receivers in use (i.e., make/model/software revision).

Reports can be made in any of the following ways:

Immediately, by radio communication to the

controlling Air Route Traffic Control Center

(ARTCC), Control Tower, or FSS.

By telephone to the nearest FAA facility.

By FAA Form 8740−5, Safety Improvement

Report, a postage−paid card designed for this

purpose. These cards may be obtained at FAA FSSs,

Flight Standards District Offices, and General

Aviation Fixed Base Operations.

In aircraft that have more than one receiver,

there are many combinations of possible interference

between units. This can cause either erroneous

navigation indications or, complete or partial

blanking out of the communications. Pilots should be

familiar enough with the radio installation of the

particular airplanes they fly to recognize this type of

interference.

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15. LORAN

NOTE

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In accordance with the 2010 DHS Appropriations Act, the
U.S. Coast Guard (USCG) terminated the transmission of
all U.S. LORAN

−C signals on 08 Feb 2010. The USCG also

terminated the transmission of the Russian American
signals on 01 Aug 2010, and the Canadian LORAN

−C

signals on 03 Aug 2010. For more information, visit
http://www.navcen.uscg.gov. Operators should also note
that TSO

−C60b, AIRBORNE AREA NAVIGATION

EQUIPMENT USING LORAN

−C INPUTS, has been

canceled by the FAA.

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16. Inertial Reference Unit (IRU),

Inertial Navigation System (INS), and
Attitude Heading Reference System (AHRS)

IRUs are self−contained systems comprised of

gyros and accelerometers that provide aircraft

attitude (pitch, roll, and heading), position, and

velocity information in response to signals resulting

from inertial effects on system components. Once

aligned with a known position, IRUs continuously

calculate position and velocity. IRU position

accuracy decays with time. This degradation is

known as “drift.”