Navigation Aids General 1

Many types of air navigation aids are used
these days, each serving a special purpose. Many of these aids have
varied owners not to mention operators, namely: the particular Federal
Aviation Administration (FAA), the military services,
private organizations, individual states not to mention
foreign governments. The FAA has the actual statutory
authority to establish, operate, maintain air navigation
facilities and also in order to prescribe practices for the
operation of any of these aids that happen to be employed for
instrument flight within federally controlled airspace.
These aids are generally tabulated within the Airport/Facility
Directory (A/FD).
Pilots will need to be aware of the actual possibility of
momentary erroneous indications on cockpit displays
when the actual primary signal generator for a ground−
based navigational transmitter (for illustration, a
glideslope, VOR, or nondirectional beacon) typically is
inoperative. Pilots will need to disregard any kind of navigation
indication, regardless of its apparent validity, generally if the
particular transmitter was diagnosed by NOTAM and / or
otherwise as unusable or inoperative.

Nondirectional Radio Beacon (NDB)
a. A low or perhaps medium frequency radio beacon
transmits nondirectional signals whereby the actual pilot of
an aircraft correctly prepared can easily determine bearings
as well as “home on the station. These facilities normally
operate in a frequency band of 190 to be able to 535 kilohertz
(kHz), according to ICAO Annex 10 the frequency
range for NDBs is actually between 190 not to mention 1750 kHz, and
transmit a continuous carrier with either 400 or perhaps
1020 hertz (Hz) modulation. All radio beacons
except the particular compass locators transmit a continuous
three?letter identification inside code except throughout voice
transmissions.
b. When a radio beacon is actually used inside conjunction with
the Instrument Landing System markers, it happens to be generally known as
a Compass Locator.
c. Voice transmissions happen to be prepared on radio beacons
unless the actual letter “W” (without voice) is included inside
the particular class designator (HW).
d. Radio beacons usually are case in order to disturbances which
might result with regard to erroneous bearing information and facts. Such
disturbances result from such factors because lightning,
precipitation static, etc. At night, radio beacons are really
vulnerable to be able to interference from distant stations.
Nearly all disturbances which affect the Automatic
Direction Finder (ADF) bearing also affect the actual
facility s identification. Noisy identification generally
occurs when the particular ADF needle is actually erratic. Voice, music
or erroneous identification might be heard when a
steady false bearing can be being displayed. Since ADF
receivers never currently have a “flag” with warn the particular pilot when
erroneous bearing info typically is being displayed, the
pilot need to continuously monitor the actual NDB’s
identification.
VHF Omni−directional Range (VOR)
VORs operate within the 108.0 to be able to 117.95 MHz
frequency band and also currently have a power output required to be able to
provide coverage within their assigned operational
service volume. They tend to be case with line−of−sight
restrictions, not to mention the range varies proportionally in order to the particular
altitude of the getting equipment.
The particular capability of the particular VOR depends upon
proper employ and also adjustment of both ground and also
airborne equipment.
1. Accuracy. The actual accuracy of course alignment
of the VOR is excellent, being usually plus or
minus 1 degree.
2. Roughness. On several VORs, minor course
roughness will be observed, evidenced by course
needle or perhaps brief flag alarm activity (some receivers are generally
more susceptible in order to many of these irregularities than others).
At a few stations, generally inside mountainous terrain, the actual
pilot may occasionally observe a brief course needle
oscillation, similar to be able to the indication of “approaching
station.” Pilots flying over unfamiliar routes usually are
cautioned in order to be found on the alert for many of these vagaries, as well as inside
particular, to be able to use the actual “to/from” indicator to be able to determine
positive station passage.
VOR Receiver Check
 The FAA VOR test center (VOT) transmits a
test signal that provides users an advantageous means
in order to determine the operational status not to mention accuracy of a
VOR receiver while on the ground where a VOT typically is
found. The actual airborne employ of VOT can be permitted;
but, its employ is actually strictly limited to be able to all those
areas/altitudes specifically authorized with regard to the A/FD or
appropriate supplement.
Tactical Air Navigation (TACAN)
For reasons peculiar to be able to military or alternatively naval
operations (unusual siting conditions, the pitching
plus rolling of a naval vessel, etc.) the civil
VOR/Distance Measuring Equipment (DME) system
of air navigation was considered unsuitable for
military or simply naval use. A modern navigational system,
TACAN, was consequently developed by the particular military plus
naval forces with more readily lend itself with military and
naval requirements. Because a result, the particular FAA has
integrated TACAN facilities with all the civil VOR/
DME program. Even though the particular theoretical, or technical
principles of operation of TACAN equipment usually are
quite different from all those of VOR/DME facilities, the particular
end result, as far as the actual navigating pilot is worried,
is actually the actual same. These integrated facilities tend to be generally known as
VORTACs.
VHF Omni−directional Range/Tactical Air Navigation (VORTAC)
A VORTAC typically is a facility consisting of 2
components, VOR plus TACAN, which delivers
3 individual services: VOR azimuth, TACAN
azimuth and even TACAN distance (DME) at you web site.
Although consisting of more than specific component,
incorporating more than it operating frequency,
and using more than one antenna system, a VORTAC
is actually considered to be a unified navigational aid. Both
components of a VORTAC happen to be envisioned as
operating simultaneously and providing the actual three
services at all the instances.
Distance Measuring Equipment (DME)
Within the operation of DME, paired pulses at a
specific spacing happen to be delivered out within the aircraft (this is actually
the interrogation) as well as are received at the particular ground
station. The ground station (transponder) then
transmits paired pulses back with the aircraft at the particular same
pulse spacing but yet on a different frequency. The time
required for the round trip of this particular signal exchange can be
measured with regard to the airborne DME unit and in addition is actually translated
into distance (nautical miles) within the aircraft with the
ground station.
Due to the particular limited number of for sale
frequencies, assignment of paired frequencies is
needed for certain military noncollocated VOR and even
TACAN facilities that serve the same area however,
that could be separated by distances up to a few
miles.
Navigational Aid (NAVAID) Service Volumes
Most air navigation radio aids that provide
positive course guidance have a designated standard
service volume (SSV). The particular SSV defines the actual reception
limits of unrestricted NAVAIDs that happen to be usable for
random/unpublished route navigation.