Subpart E
The aeronautical fixed service shall comprise the following systems and
applications that are used for ground i.e. point-to-point and/or point-to-multi
unit communications in the international aeronautical telecommunication service.
(a) ATS direct
speech circuits and networks;
(b) Meteorological
operational circuits, networks and broadcast systems;
(c) The
aeronautical fixed telecommunications network AFTN;
(d) The common
ICAO data interchange network (CIDIN);
(e) The air
traffic services (ATS) message handling services; and
(f) Inter – centre
communications (ICC)
174.303 Material permitted in AFS
messages
The following characters are
allowed in text:
Letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Figures: 1234567890
Other signs :
- (hyphen)
?
(Question mark)
:
(colon)
(
(Open bracket)
)
(close bracket)
.
(Full stop, period, or decimal point)
,
(comma)
‘(Apostrophe)
= (double hyphen or equal sign)
/ (oblique)
+ (plus sign)
Characters other than those listed above
shall not be used in messages unless absolutely necessary for under standing of
the text. When used, they shall be spelled
out in full.
174.305 Messages using the ITA-2 code
They shall not contain
any uninterrupted sequence of:
(a) Signals number and
(letter case and figure case) in this order, other than the one in the
heading; or
(b) Four times signal
numbers (letter case and figure case)
other than the one in the ending.
Shall not contain:
(a) Character 0/1 (SOH) other
than the one in the heading;
(b) Character 0/2 (STX) other
than the one in the origin line;
(c) Character 0/3 (ETX) other
than the one in the ending;
(d) Any uninterrupted
sequence of characters (ZCZC);
(e) Any uninterrupted
sequence of characters (+:+:);
(f) Any uninterrupted
sequence of four times character (NNNN); or
(g) Any uninterrupted
sequence of four times character (,,,,)
Shall be drafted in plain language or in abbreviations and codes. The originator shall avoid the use of plain
language when reduction in the length of the text by appropriate abbreviations
and codes is practicable words and phrases which are not essential, such as
expressions of politeness shall not be used.
174.311 Wishing of alignment functions
If the originator of a message wishes alignment functions (<=) to be
transmitted at specific places in the text part of such message, the sequence
[<º] shall be written on each of those places.
174.313 Meteorological
operational channels and meteorological operational Telecommunication networks
Meteorological operational channels procedures and meteorological
operational Communication network procedures shall be compatible with
aeronautical fixed Telecommunication network (AFTN) procedures.
The aeronautical fixed telecommunication network shall handle the
following categories of message:
Distress messages;
Urgency messages;
Flight safety messages;
Meteorological messages;
Flight regularity messages;
Aeronautical information
services (AIS) message;
Aeronautical administrative messages;
and
Service messages;
Procedures acceptable to the E.C.A.A. Distress messages (priority
indicator SS). These messages shall comprise those messages sent by mobile
stations reporting that they are threatened by grave and imminent danger and
all other messages relative to the
immediate assistance required by the mobile station in distress .
Urgency messages (priority
indicator DD). This category shall comprise messages concerning the safety of a
ship, aircraft or other vehicles, or of some person on board or within sight.
174.321 Flight safety messages
Procedures acceptable to the
E.C.A.A. Flight safety messages
(priority indicator FF shall comprise).
Movement and control
messages;
Messages originated by an
aircraft operating agency of immediate concern to aircraft in flight or
preparing to depart;
Meteorological messages
restricted to SIGMET information, special air-reports, AIRMET messages, and volcanic ash and
tropical cyclone advisory information and amended forecasts;
174.323 Meteorological messages
Meteorological messages (priority indicator GG shall comprise:
Messages concerning
forecasts, e.g. terminal aerodrome forecasts (TAFS), area and route forecasts;
and,
Messages concerning observations and reports,
e.g. METAR,SPECI
174.325 Flight regularity messages
Flight regularity messages (priority indicator GG shall comprise:
Aircraft load messages
required for weight and balance computation;
Messages concerning changes
in aircraft operating schedules;
Messages concerning aircraft
servicing;
Messages concerning changes
in collective requirements for passengers, crew and cargo covered by deviation
from normal operating schedules.
Messages concerning
non-routine landings;
Messages concerning
pre-flight arrangements for air navigation services and operational servicing
for non-scheduled aircraft operations, e.g. over flight clearance requests;
Messages originated by
aircraft operating agencies reporting an aircraft arrival or departure;
Messages concerning parts
and materials urgently required for the operation of aircraft;
174.327 Aeronautical information services
Aeronautical information
services (AIS messages (priority indicator GG) shall comprise:
Messages concerning NOTAM’S;
and
Messages concerning SNOTAMS.
174.329
Aeronautical administrative messages
Aeronautical administrative
messages (priority indicator KK) shall comprise:
Messages regarding the
operation or maintenance of facilities provided for the safety or regularity of
aircraft operations;
Messages concerning the
functioning of aeronautical telecommunication service; and Messages exchanged
between civil aviation authorities relating to aeronautical services.
174.331 The
selection of priority
Messages requesting information shall take the same priority indicator as
the category of message being requested except where a higher priority is
warranted for flight safety.
Service messages (priority indicator as appropriate). This category shall
comprise messages originated by aeronautical fixed station to obtain
information or verification concerning other messages which appear to have been
transmitted incorrectly by the aeronautical fixed service, confirming channel
sequence numbers, etc.
174.335
Service messages preparation
Service messages shall be prepared in the format of service messages
addressed to an aeronautical fixed station identified only be a location
indicator, this Indicator shall be immediately followed by the ICAO three letters designator YFY, followed by an
appropriate 8th letter.
174.337
Priority of service messages
Service messages shall be assigned the appropriate priority indicator.
174.339
Service message previously transmitted
When service messages refer to messages previously transmitted , the
priority Indicator assigned should be that used for the message (s) to which
they refer.
Service messages correcting errors in transmission shall be addressed to
all addresses that will have received the incorrect transmission.
174.343
Reply to a service message
Reply to a service messages shall be addressed to the station which
originated the initial service message.
174.345 Text
of a service message
The text of all service messages
should be as concise as possible
A service message, other than one acknowledging the receipt of SS
messages, shall further identified by the use of abbreviation SVC as the first
item in the text.
When a service message refers to a
message previously handled , reference to the previous message shall be made by
use of appropriate transmission identification.
The order of priority for the transmission of messages in the
aeronautical fixed telecommunication network may be as follows:
Transmission priority.
Priority indicator.
SS.
DD FF.
GG KK.
174.353 Messages having the same
priority indicator
Messages having the same priority
indicator shall be transmit in the order which they are received for
transmission.
All communications shall be routed by the most expeditious route
available to effect delivery to the addressee.
174.357 Predetermined
diversion routing.
Predetermined diversion routing arrangements shall be made, when
necessary, to expedite the movement of communication traffics. Each
communication center shall have the appropriate diversion routing lists, agreed
by the Administrations operating the communication centers affected and shall
use them when necessary.
Diversion routing should be initiated:
(a) In a fully
automatic communication center; Immediately after detection of the circuit
outage when the traffic is to be diverted via a fully automatic communication
center;
(b) Within a
10-minutes period after detection of the circuit outage, when the traffic is
to be diverted via a non-fully automatic
communication center. In a non-fully automatic communication center within 10
minutes period after diction of the circuit outage. Service message
notification of the diversion requirement should be provided where no bilateral
or multilateral prearranged agreements exist.
174.361 Disposing traffic over the
aeronautical fixed service
As soon as it is apparent that it will be impossible to dispose of
traffic over the aeronautical fixed service within a reasonable period, and
when the traffic is held at the station where it was filed, the originator
shall be consulted regarded further action to be taken unless otherwise agreed
between the station concerned and the originator, or arrangement exist whereby
delayed traffic automatically diverted to commercial Telecommunication services
without reference to the originator.
174.363 Supervision of message traffic.
Continuity of message traffic: The receiving station shall check the
transmission identification of incoming transmissions to ensure the correct
sequence of channel sequence numbers received over that channel
174.365 Missing channel-sequence numbers
When the receiving station detects that one or more channel-sequence
numbers are missing, it shall send a complete service message, to the previous
station rejecting receipt of any message that may have been transmitted with
such missing number (s). The text of this service message shall comprise the
signal QTA, the procedure signal MIS followed by one or more missing
transmission identification and the end of text signal.
174.367 Responsibility for transmission
of the message
The station notified of the Missing message (s) condition by the service
message shall reassume its responsibility for transmission of the message or
messages that it had previously transmitted with the transmission
identification concerned, and shall re-transmit that message or those messages
with a new correct in sequence transmission identification concerned. The
receiving station shall synchronize such that the next expected channel –
sequence number is last received channel – sequence number plus one.
174.369 If the channel sequence less
than that expected
When the receiving detects that a message has a channel sequence number
less than that expected it should advise the previous station using a service
message with a text comprising the:
Abbreviation SVC;
Procedure signal LR followed
by the transmission identification of the received message;
Procedure signal EXP
followed by the transmission identification expected; and
End of test signal.
174.371 Correcting the channel sequence
number
The station receiving out of
sequence message should synchronize such that the expected channel sequence
number is the last received channel sequence number plus one. The previous
station checks its outgoing channel sequence numbers and, if necessary,
corrects the sequence.
When the receiving station detects that a
message has been misrouted to it, it shall either:
(a) Send a service
message to the previous station rejecting receipt of the misrouted message; or
(b) Itself assume
responsibility for transmission of the message to all addressee indicators.
174.375 Receiving a misrouted message
The text of the service message shall comprise the abbreviation SVC, the
signal QTA, the procedure signal MSR followed by the transmission
identification
When the sending station is notified of the misrouted message condition
by service message, it shall reassume its responsibility for the message and
shall re-transmit as necessary on the correct outgoing channel or channels.
When a circuit becomes interrupted and alternative facilities exist, the
last channel sequence numbers sent and received shall be exchanged between the
stations concerned. Such exchanges shall take the form of complete service
messages with the text comprising the abbreviation SVC, the procedure signals
LS and LS followed by the transmission identification of the relevant messages
and the end – of – text signal
174.381. Failure of communications
Should communication on ant fixed service fail, the station concerned
attempt to re-establish contact as soon as possible.
If contact cannot be re-established within a reasonable period on the
normal fixed service circuit, an appropriate alternative circuits should be
used . If possible, attempts should be made to establish communication on any
authorized fixed service circuit available.
If attempts fail, use of any available air-ground frequency is permitted
only as an exceptional and temporally measure when no interference to aircraft
in flight is ensured.
174.387 Failing of radio circuits due to
propagation conditions
Where a radio circuit fails due to signal fade- out or adverse
propagation conditions, a receiving watch shall be maintained on the regular
fixed service frequency normally in use. In order to re-establish contact on
this frequency as soon as possible the following shall be transmitted:
(a) The procedure
signal DE;
(b) The
identification of the transmitting station transmitted three times;
(c) The alignment
function (<=);
(d) The letters RY
repeated without separation for three lines of page copy;
(e) The alignment
function (<=); and
(f) End of message
signal (NNNN) the forgoing sequence shall be repeated as required.
174.389 Action be taken in case of radio
communication failure
A station experiencing a circuit or equipment failure shall promptly
notify other stations with which it is in direct communication if the failure
will affect routing by those stations restoration to normal shall also be
notified to the same stations.
Where diverted traffic will not be accepted automatically or where a
predetermined diversion routing has not been agreed, a temporary diversion
routing shall be established by the exchange of service messages. The text of
such service messages shall comprise:
(a) The
abbreviation SVC;
(b) The procedure
signal QSP; and
(c) If required,
the procedure signals RQ, NO or CNL to request, refuse or cancel a diversion.
Copies of all messages, in their entirety, transmitted by an AFTN origin
station shall be retained for a period of at least 30 days.
174.395 AFTN destination stations
AFTN destination stations shall retain, for a period of at least 30 days,
a record containing the information necessary to identify all messages received
and the action taken thereon.
174.397 Period of retention of traffic
at the AFTN radio station
AFTN communication centers should retain, for a period of at least 30
days, a record Containing the information necessary to identify all messages
relayed or re-transmitted and the action taken thereon.
174.399 Period of retention of traffic
at the AFTN radio station
AFTN communication centers shall retain, for a period of at least one
hour, a copy of all messages, in their
entirety. re-transmitted or relayed by that the communication center
In cases where acknowledgement is made between AFTN communication
centers, a relay center shall be considered as having no further responsibility
for retransmission or repetition of a message for which it has received
positive acknowledgement and it may be deleted from its records.
Test messages transmitted on AFTN channels for the purpose of testing and
repairing lines should consist of the following:
(a) The
start-of-message signal;
(b) The procedure
signal QJH1;
(c) The originator
indicator;
(d) Three
page-copy lines of the sequence of characters RY. In ITA-2 or U (5/5)* (2/10)
in IA-5; and
(e) The
end-of-message signal.
174.405 Messages using (ITA-2)
All messages, other than those prescribed in 174.403 and 173.495, shall
comprise the components specified in 174.497 to 174.485 inclusive.
The heading shall comprise:
(a) Start-of-message
signal, the characters ZCZC.
(b) Transmission
identification comprising:
(1) Circuit
identification; and
(2) Channel
sequence number.
(c) Additional
service information if necessary comprising:
(1) One SPACE;
(2) Not more than
ten characters; and
(3) Spacing
signal.
174.409 Contents of the circuit
identification
The circuit identification shall consists of three letters selected and assigned
by the transmitting station, the first letter identifying the transmitting, the
second letter the receiving end of the circuit and the third letter to identify
the channel, where there is only one channel between the transmitting and the
receiving station. Channels letter A shall be assigned, where more than one
channel between Stations is provide, the channels shall be identified as A,V,C
etc. in respective Order.
174.411 Three digits channel- sequence
numbers
Three digits channel- sequence numbers from 001 to 000 ( representing
1000) shall be assigned sequentially by the telecommunication stations to all
messages Transmitted directly from one station to another. A separate series of
these Numbers shall be assigns for each channel and a new series shall be
started at 0000 hours.
174.413 The use of four digit channel
sequence number
The use of four digit channel sequence number, to preclude duplication of
the same numbers during the 42 hour period, is permitted subject to agreement
between the authorities responsible for the operation of the circuit.
174.415 The transmission identification
The transmission identification shall be sent over the circuit in the
following sequence:
(a) Space;
(b) Transmitting
terminal letter;
(c) Receiving
terminal letter;
(d) Channel
identification letter;
(e) Figure shift;
and
(f) Channel
sequence number (3 digits)
174.417 Teletypewriter operation
In teletypewriter
operation, the spacing signal, consisting of 5 SPACES
[→→→→→] followed by 1 LETTER SHIFT [↓],
shall be transmitted immediately following the transmission identification Tape
Page-copy →GLB↑039→→→→→↓ GLB039
(This indicates the 39th message of the day transmitted on Channel B of the
circuit from Station G to Station L.)
174.419
Optional service information
Optional service
information can be inserted following the transmission identification subject
to agreement between the authorities responsible for the operation of the
circuit. Such additional service information shall be preceded by a SPACE
followed by not more than ten characters and shall not contain any alignment
functions.
To avoid any
misinterpretation of the diversion indicator specially when considering the
possibility of a partly mutilated heading, the sequence of two consecutive
signal NO 22 in the letter case or in the figure case should not appear in any
other component of the heading.
The address
shall comprise:
(a) Alignment function;
(b) Priority
indicator;
(c) Addressee
indicator; and
(d) Alignment
function.
Priority indicator shall
consist of the appropriate two-letter group assigned by the originator in
accordance with the following priorities:
(a)
Message category indicator;
(b)
Distress messages SS;
(c)
Urgency messages DD;
(d)
Flight safety messages FF;
(e)
Meteorological messages GG;
(f)
Flight regularity messages GG;
(g)
Aeronautical information services messages GG; and
(h)
Aeronautical administrative messages KK.
174.427 An addressee indicators
Addressee indicators, which
shall be immediately preceded by a SPACE, except when it is the first address
indicator of the second or third line of address, shall comprise:
(a) The
four-letter location indicator of he place of destination; and
(b) The
three-letter designator identifying the organization/function (authority,
service or aircraft operating agency) addressed and an additional letter, which
shall represent a department, division or process within the
organization/function addressed. The letter X shall be used to complete the
address when explicit identification is not required.
174.429 Address has not been allocated
an ICAO
Where a message is to be addressed to an organization that has not been
allocated an ICAO three letters designator of the type prescribed in 4.4.3.1.2,
the location indicator of the place of destination shall be followed by the
ICAO three letters designator YYY (or the ICAO three letter designator YXY in
the case of a military service or organization). The name of the addressee
organization shall then be included in the first item of the text of the
message the 8th position letter following the ICAO three letters designator YYY
or YXY shall be filler letter X.
174.431 Message addressed to an aircraft
in flight
Where a message is to be addressed to an aircraft in flight and ,
therefore, requires handling over the AFTN for part of its routing before
transmission over the aeronautical mobile service, the location indicator of
the aeronautical station which is to relay the message to the aircraft shall be
followed by the ICAO three designator ZZZ the identification of the aircraft
shall then be included in the first item of the text of the message. The its
position letter following the ICAO three designator ZZZ shall be the filler
letter.
The complete address the be restricted to three lines of page printing
copy and comma except as provided in 4.4.14, a separate addressee indicator
shall be used for each addressee whether at the same or at different location.
174.435 Messages offered in page copy
Where messages offered in page copy form for transmission and contain
more addressee indicator than can be accommodated on three lines of a page
copy, such message shall be converted, before transmission into two or more
messages, each of which shall conform with the provisions of 174.435 and .437,
during such conversion, the addressee indicator shall, in so far as practicable
be positioned in the sequence which will ensure that the minimum number
re-transmissions will be required at subsequent communication center.
174.437 Completion of each line of addressee
On
teletypewriter circuits, the completion of each line of addressee indicator
groups in the address of a message shall be immediately followed by the
alignment function [<≡].
The origin shall comprise:
(a) Filing time;
(b) Originator
indicator;
(c) Priority alarm
(when necessary);
(d) Optional
heading field; and
(e) Alignment
function.
The filing time shall
comprise the 6-digit date time group indicating the date and time of filing the
message for transmission in Teletype write operation, the filling time shall
followed by one letter shift.
An originator indicator,
which shall immediately preceded by a space shall comprise:
(a) The
four-letter location indicator of the place at which the message is originated;
(b) The
three-letter designator identifying the organization function (aeronautical
authority, service or aircraft operating agency) which originated the message;
and
(c) An additional
letter which shall represent a department, division or process within the
organization/function of the originator. The letter X shall be used to complete
the address when explicit identification is not required.
174.445 Organization has not been
allocated an ICAO
Where a message is originated by an organization that has not been
allocated and ICAO three letter designator of the type the location Indicator
of the place at which the message is originated shall be followed Immediately
be the ICAO three letter designator YYY followed by the filler Letter X (or the
ICAO three letter designator YXY followed by the filler X In the case a
military service or organization). The name of the organization (or Military
service) shall then be included in the first item in the text of the message.
174.447 Message originated by an
aircraft in flight
Where a message originated by an aircraft in flight requires handling on
the AFTN for part of its routing before delivery, the originator shall comprise
the location indicator of the aeronautical station responsible for transferring
the message to the AFTN, followed immediately by the ICAO three letters
designator ZZZ followed The filler letter X. the identification of the aircraft
shall then be included in the First item in the text of the message.
174.449 Messages relayed over AFTN
Messages relayed over the AFTN that have been originated in other
networks shall a valid AFTN originator that has been agreed for use by the
relay or gateway function linking the AFTN with the external network.
The priority alarm shall be used only for distress messages. When used it
shall consist of the following, in the order stated;
(a) FIGURE SHIFT [ ];
(b) FIVE
transmissions of signal no. 10 (figure
case); and
(c) LETTER SHIFT [¯].
174.453 The inclusion of optional
data
The inclusion of optional data in the origin line shall be permitted
provided a total of 96 characters is not exceeded and subject to agreement
between the authorities concerned.
174.455 The presence of the optional
data
The presence of the optional data field should be indicated by one
occurrence of the space character and terminated by the alignment function.
174.457 Additional addressing
information in a message
When additional addressing information in a message needs to be exchanged between source and destination addresses, it should
be conveyed in the optional data field (ODF), using the specific format characters one and full stop to indicate the parameter
code for the additional address function three
modifier characters followed by an equal sign (=) and the assigned 8-
characters ICAO address, and the character (-) to terminate the additional
address parameter field.
174.459 Separate address for service
messages
When a separate address for service messages or inquiries is different
from the originator indicator, the modifier SVC should be used.
The origin line shall be concluded by and alignment function.
The text of messages shall be drafted in accordance with ICAO message
format
When an originator’s reference is used, it shall appear at the beginning
of the text
174.467
ICAO three letter designator
When the ICAO three letter designator YXY, YYY or ZZZ comprise the second
element of addressee indicator and it therefore, becomes necessary identify in the text the specific addressee
of the message, such identification group will precede the originator's (if
used) and become the first item of the text
174.469 ICAO three letter designator
YXY, YYY or ZZZ
When the ICAO three letter designator YXY, YYY or ZZZ comprise the second
element of the originator indicator and it thus, becomes necessary to identify in the text the name of organization or (military
service) or the aircraft, which originated the message, such identification
shall be inserted in the first item of the text of the message.
174.471 ICAO three letters designator
(s) YXY, YYY or ZZZ
When applying the provisions of messages where the ICAO three letters
designator (s) YXY, YYY or ZZZ is (are) used to refer to two or
more different organizations or ( military services), the sequence of further
identification in the text shall correspond to the complete sequence used in
the address and origin of the message. In such instance, used in the address
each addressee identification shall be followed immediately by an alignment
function. Message shall The name of the (YXY, YYY or ZZZ) organization originating
the function. Message shall then be preceded with (FROM) (STOP) followed
by an alignment function shall then be
included in the text at the end of these
identification to proceed the remainder of the text wording.
An alignment function (<=) shall be transmitted at the end of each
printed line of the text.
174 475 Teletypewriter operation
When it is desired to confirm a portion of the text of a message in
teletypewriter operation, such confirmation shall be separated from the last
text group by an alignment function [<ß], and shall be indicated
by the abbreviation CFM followed by the portion being confirmed.
When
it is discovered that an error has been made in the text, the correction shall
be separated from the last text group or confirmation, if any, by an alignment
function [<ß] in the case of teletypewriter circuits. This shall
be followed by the abbreviation COR and the correction.
174.479 Action be taken before the local delivery
Stations shall make all indicated correction on the page copy prior to
local delivery.
At the end of the text the following end- of – text signal shall be
transmitted one letter shift, alignment function (< =).
The text of the messages entered by the AFTN origin station shall not
exceed 1800 characters in length.
The ending shall comprise: the page – feed sequence consisting of seven
line feed the end of message signal consisting
of the letter N (letter case of signal NO140 appearing four times in undivided
sequence the message separation signal
consisting of a letter shift transmitter 12 times in uninterrupted sequence.
AFTN messages entered by the AFTN origin station shall not exceed 2100
characters in length.
Stripped address when an AFTN communication center shall omit from the
address or the addressee indicators not required
for :onward transmission by the AFTN communication center to which the message
is transmitted. local delivery to the addressee (s) by the
AFTN destination station onward
transmission or local delivery by the aggregate of stations on a multi- point
circuit.
A single line of page-copy shall not contain more than a total of 69
characters and/or spaces.
174.493 Line of the text of a message.
One CARIAGE RETURN (<) and one LINE FEED IMPULSES (=) shall be
transmitted between each printed page – line of the text of a message.
174.495 Channel-check transmissions
Channel-check transmissions, the following periodic transmissions shall
be sent on teletypewriter circuits:
(a) Heading;
(b) Alignment
function;
(c) The procedure
signal CH;
(d) Alignment
function;
(e) End-of-message
signal [NNNN]; and
(f) Message-separation
signal, (if required): The receiving station shall then check the transmission
identification of this incoming transmission to ensure its correct sequence in
respect of all messages received over that incoming channel.
Where a circuit is unoccupied, the transmission should be at H+00, H+20,
and H+ 40.
174.499 In case of periodical check not
received
If a periodic channel check
transmission is not received within a tolerant agreed for that channel a station
shall send a service message to the station from which the transmission was
expected, the text of this service message shall comprise:
(a) The
abbreviation SVC;
(b) The procedure
signal MIS;
(c) The procedure
signal CH;
(d) (Optionally)
the time at which transmission was expected;
(e) The procedure
signal LR;
(f) The
transmission identification of the last message received; and
(g) The end of
text signal
174.501 Channel check transmission
When
a teletypewriter channel is equipped with a system of controlled circuit
protocol and following agreement between the Administrations responsible, the
periodic Transmission shall be sent on teletypewriter circuits.
174.503 Channel check transmission
Channel-check transmissions and station radio identifications. In order
to satisfy the requirements of ITU regarding periodic transmission of the
station radio identification, those AFTN stations using radio teletypewriter
channels may combine the station radio identification transmission with the
channel-check transmission shall be sent as follows:
(a) Heading;
(b) Alignment
function [<ß];
(c) The procedure
signal CH;
(d) Alignment
function [<ß];
(e) The procedure
signal de followed by one space [¨]and the assigned ITU radio call sign;
(f) Alignment
function [<ß];
(g) End-of-message
signal [NNNN]; and
(h) Message-separation
signal
[««««««««««««]
(if required).
174.505 Action be taken in case of multichannel
circuits
When multichannel radio teletypewriter
circuits are used (E.g. MET and AFTN) the station radio call sign transmission
should be sent on only one channel of the circuit. The channel chosen should be
the one which is the most convenient for this purpose with the identification
transmission being sent in conformance with the format used on that channel.
When an AFTN channel is chosen the identification transmission should be
combined with the channel-check transmission.
174.507 Automatic error correction
When a teletypewriter circuit is associated with Automatic Error
Correction equipment, and following agreement between the Administrations responsible,
the transmissions need not be made; however stations employing radio
teletypewriter channels on the AFTN for which the station radio identification
is required.
174.509 Periodical responsibility
Messages shall be transmitted in accordance with
predetermined responsibility for onward relay as agreed between the
Administrations responsible for the operation of directly connected stations.
174.511 Predetermined responsibility list
Arising from the responsibility agreements established under the
predetermined responsibility, each station of the AFTN shall employ and, adhere
to a Routing Directory which consists of the Routing list.
174.513 In case of containing identical location
indicator in the address
When an incoming message contains only identical
location indictor in the lines following the heading the receiving station
shall accept responsibility for further relay. If possible such relay shall be
affected on the normal outgoing circuit to the place of destination of the
message if it is not possible to use the normal circuit; an appropriate
alternative outgoing circuit shall be used. When neither of these facilities is
in operation, the message shall not be re-transmitted over the circuit from
which it was received without prior service notification of this action being
given to the station that had made the previous transmission.
174.515 AFTN message originator not capable of
handling service messages
An AFTN message originator not capable of handling service messages
should agree with the AFTN center it is connected to on a method of exchanging
service message.
Form of transmission -
teletypewriter operation: All transmission shall comprise the following order
starting pulse:
(a) Heading;
(b) Address;
(c) Origin; and
(d) Ending.
Message format all messages shall be prepared in accordance with: (ITA-2
format) or (IA-5 format)
The heading line with the exception of the SOH character, should omitted
on circuits employing one of the data link control procedure.
174.523 Re-processing procedures
A message requiring
re-transmission shall have its previous heading deleted by the station which
received such message for relay. The re-transmission shall commence with the
new heading using the transmission identification for the outgoing channel.
174.525
Transmission of address
The transmission of address part of the message shall commence at some
point during the 5 spaces, 1 letter shift immediately preceding the first
alignment function.
174.527 Acknowledgement of receipt
Acknowledgement of receipt of messages: In teletypewriter operation a
receiving station shall not transmit acknowledgement of receipt of incoming messages.
174.529 The receipt of distress messages
The receipt of distress
messages (priority indicator SS.) shall be individually acknowledged by the
AFTN destination station by sending a service message to the AFTN origin
station. Such acknowledgement of receipt shall take the format of a complete
message addressed to the AFTN origin station, shall be assigned priority
indicator SS and the associated priority alarm and shall have a text
comprising:
(a) The procedure
signal R;
(b) The origin
without priority alarm, or optional heading information of the message being
acknowledged; and
(c) The end of
text signal.
174.531 Repetition of multi-address message
In cases where an addressee of a
multi- address message request repetition from the origin station, the origin
station shall address the repeat of the message procedure only to the addressee
requesting the repeat. Under this condition the signal DUPE shall not be
included.
174.533 During the
re-transmission of a message
Before retransmission is commenced, a relay station detects that one or
more messages have been mutilated at some point ahead of the end-of-message
signal, and it has reason to believe that this mutilation had occurred during
or subsequent to its transmission from the previous station, it shall send a
service message to the previous station rejecting the mutilated transmission
and requesting a repetition of the incorrectly received message (or messages).
174.535 Receiving service Message for mutilated
message
The station receiving the service
message shall re-assume the responsibility for the referenced message. It shall
then re-transmit the un mutilated copy of the referenced message with a new
transmission identification. If that station is not possession of an mutilated
copy of the original message, it shall take the action required.
174.537 Before re-transmission is commenced
If before re-transmission is commenced a relay station detects that a
received message has a recognizable but mutilated end-of-message signal. It
shall where necessary repair this mutilation before re-transmission.
174.539 After a message has been transmitted
If after a message has been transmitted into, a station detects that the
text or the origin of the message was mutilated or incomplete, it shall
transmit to all addresses concerned a service message with the following text,
if an unmutilated copy of the message is available in the station:
SVC CORRECTION (THE ORIGIN INCORRECT MESSAGE) STOP
(FOLLOWED BY THE
CORRECT TEXT)
174.541
If after transmission of the text
After
transmission of the message text, if a relay station detects that the message
has an obviously mutilated end-of-message signal; it shall insert a proper end
of-message signal into the channel.
174.543
Incomplete end of message signal
After
transmission of the text material of a message, if a relay station can detect
that there is no complete end-of-message signal, but has no practicable means
of discovering whether the irregularity has affected only the end of- message
signal or whether it may have also caused part of the original text to have
been lost, it shall insert into the channel the following:
(a) ¯<ºCHECKºTEXTº
NEW®ENDING®ADDED®;
(b)Its own station
identification;
(c) ¯<º; and
(d)A proper ending as
described in 174.485.
Relay
stations applying the procedural should, if practicable, ensure that the
appropriate material therein prescribed is inserted prior to the transmission
of a complete start-of-message signal associated with any following message.
174.547 Receiving completely mutilated
address line
If a relay station detects that a message was received with a completely
mutilated address line, it shall send a service message to the previous station
rejecting the mutilated transmission.
174.549 The text of this service message
The text of this service message shall comprise:
(a) The abbreviation SVC
(b) The procedure signal QTA
(c) The procedure signal ADS
(d) The transmission
identification of the message rejected
(e) The indication corrupt
(f) The end of text signal
174.551 Resuming the responsibility
The station receiving such a service message shall re-assume
responsibility for the referenced message and shall re-transmit the message
with a corrected address line, and a new transmission identification.
174.553 Length of messages other than 8 letters
If
a relay station detects a received message with an invalid (i.e. length other
than 8 letters) or unknown addressee indicator, it shall relay the message to
those valid addresses for which it has relay responsibility using the stripped
address procedure.
174.555
Service requesting correction in errors
The
station shall send a service message to the previous station requesting
correction of the error. The text of this service message shall comprise:
(a) The abbreviation
SVC;
(b) The procedure
signal ADS;
(c) The
transmission identification of the message in error;
(d) An alignment
function;
(e) The first
address line of the message as received;
(f) An alignment
function; and
(g) Either:
(1) For an
invalid addressee indicator: the indication CHECK;
(2) For an
unknown addressee indicator: the indication UNKNOWN;
(3) The
invalid or unknown addressee indicator(s); or
(4) The
end-of-text signal.
174.557
Station receiving a service message
A station receiving a service message shall,
if a Correct addressee indicator is available, repeat the message to that
addressee only using the stripped
address procedure or, if a correct
addressee indicator is not available,
the shall send a service message
to the previous station requesting
correction of the error.
174.559
Unknown addressee indicator
In
the case of an unknown addressee indicator, and if the origin of the message is
without fault, the station shall send a service message to the originator. The
text of this service message shall comprise:
(a) The
abbreviation SVC;
(b) The procedure
signal ADS;
(c) The origin of
the message in error;
(d) An alignment
function;
(e) The first
address line of the message as received;
(f) An alignment
function;
(g) The indication UNKNOWN;
(h) The unknown
addressee indicator(s); and
(j) The end-of-text
signal.
174.561 Correct addressee indicator
The
station receiving a message described in 174.561 shall obtain a correct
addressee indicator and shall repeat the message to the addressee using the
stripped address procedure.
174.563
The first relay station
When
the first relay station detects that a message was received with a mutilated
origin line or without any origin, it shall:
(a) Stop
processing the message; and
(b) Send a
service message to the station from which the station from which the message
was received.
174.565
The text of this service message
The
text of this service message shall comprise:
(a) The
abbreviation SVC;
(b) The procedure
signal QTA;
(c) The procedure
signal OGN;
(d) The
transmission identification of the message rejected;
(e) The indication
CORRUPT; and
(f) The end-of-text
signal.
174.567
Action be taken on a service message
The
station receiving a service message shall reassume responsibility for the
referenced message and shall retransmit the message with a correct origin line
and a new transmission identification.
174.569
Receiving incorrect originator indicator
When
the first relay station detects that a message was received with an incorrect
originator indicator, it shall:
(a) Stop processing the message; and
(b) Send a service message to the station from which the message was
received.
174.571
Text of the service message
The
text of the service message shall comprise:
(a) The abbreviation SVC;
(b) The procedure signal QTA;
(c) The procedure signal OGN;
(d) The transmission identification of the message rejected;
(e) The indicator INCORRECT; and
(f) The end-of-text signal.
174.573
The station receiving a service message
The
station receiving a service message shall resume responsibility for the
referenced message and shall retransmit the message with a correct originator
indicator and if applicable, a new transmission identification.
The
ending must be typed without error.
174.577
Predetermined distribution system
When
it has been agreed between the Administrations concerned to make use of a
predetermined distribution system for AFTN messages.
174.579
Predetermined distribution addressee indicator (PDAI)
The
predetermined distribution addressee indicator shall be constructed as follows:
(a) The first
and second letters: The first two letters
of the Location Indicator of the communications centre of the State which has
agreed to implement the system and which receives
messages over a circuit for which it has a predetermined routing
responsibility;
(b) The third
and fourth letters: The letters ZZ, indicating a requirement for special
distribution;
(c) The fifth,
sixth and seventh letters:
(1) The
fifth, sixth and seventh letters taken from the series A to Z and denoting the
national and/or international distribution list(s) to be used by the receiving
AFTN centre;
(2) “N” and
“S”, as the fifth letter, are reserved for NOTAM and SNOWTAM respectively (see
Appendix 5 to Annex 15);
(d) The eighth
letter: Either the filler letter “X” or a
letter taken from the series A to Z to further define the national and/ or
international
distribution list(s) to be used by the
receiving AFTN centre.
174.581.
AFTN messages carrying predetermined addressee indicator
Distribution addressee indicators allocated by the State receiving the
message shall be routed to the addressees listed on the associated list of addressee
indicators described in 173.583.
174.583 States shall send their list of selected
predetermined list
States
shall send their list of selected Predetermined Distribution Addressee
Indicators together with the associated lists of Addressee Indicators to:
(a) The States
from which they will receive AFTN messages for predetermined distribution, to
assure correct routing; and
(b) The States
which will originate AFTN messages for predetermined distribution to facilitate
the treatment of requests for retransmission and to assist originators in using
the predetermined distribution addressee indicators correctly.
174585
The list of addressee indicator of (PDAI)
The
list of Addressee Indicators associated with a predetermined distribution
addressee indicator shall include either:
(a) Addressee
Indicators for national distribution;
(b) Addressee
Indicators for international distribution;
(c) Predetermined
Distribution Addressee Indicators for international distribution; or
(d) Any combination
of (a), (b) and (c).
174.587
Message format
Message format — International Alphabet No. 5 (IA-5): When it has been
agreed between the. When it has been agreed between the Administrations format
shall be used. It concerned to use International Alphabet No. 5 (IA-5) the
shall be the responsibility of Administrations using IA-5 to accommodate
adjacent AFTN stations employing ITA-2 code.
The heading shall comprise:
(a) Start-of-heading (SOH)
character 0/1;
(b) Transmission
identification comprising:
(c) circuit or link
identification;
(d) channel-sequence number;
(e) Additional service
information (if necessary) comprising:
(f) One SPACE; and
(g) No more than 10
characters.
174.591
On point-to-point circuits
On point-to-point circuits or links, the identification shall consist of
three letters selected and assigned by the transmitting station; the first
letter identifying the transmitting, the second letter the receiving end of the
circuit, and the third letter the channel. Where only one channel exists, the
letter A shall be assigned. Where more than one channel between stations is
provided, the channels shall be identified Alphabet No. 5 (IA-5) as A, B, C,
etc., in respective order. On multipoint channels, the identification shall
consist of three letters selected and assigned by the circuit control or master
station.
174.593
Channel sequence numbers
Three-digit
channel-sequence numbers from 001 to 000
(representing 1 000) shall be assigned sequentially by telecommunication
stations to all messages transmitted directly from one station to of these
numbers shall be assigned another A separate series for each channel and a new
series shall be started daily at 0000 hour.
174.595 The expansion of the channel-sequence
number
The expansion of the channel-sequence number to preclude duplication of
the same numbers during the 24-hour period should be permitted subject to
agreement between the authorities responsible for the operation of the circuit.
174.597 The transmission identification
The transmission identification
shall be sent over the circuit in the following sequence:
(a) Transmitting-terminal letter;
(b) Receiving-terminal
letter;
(c) Channel-identification letter; and
(d) Channel-sequence number.
174.599
Additional service information
Additional
service information shall be permitted to be inserted following the
transmission identification subject to agreement between the Authorities responsible for the operation of the circuit.
Such additional service information shall be preceded by a SPACE (→)
followed by not more than 10 characters inserted into the heading of message
immediately following the last digit of the
channel-sequence number and shall not contain any alignment functions.
When no such additional service information is added of transmission
identification shall be followed immediately by address.
The address shall comprise:
(a) Alignment function
[<≡];
(b) Priority indicator;
(c) Addressee indicator(s);
and
(d) Alignment function
[<≡].
174.603
The priority indicator
The priority indicator shall consist of the
appropriate two-letter group assigned by the originator in accordance with the
following:
(a) SS distress messages;
(b) DD urgency messages;
(c) FF flight safety
messages;
(d) GG meteorological
messages;
(e) GG flight regularity
messages;
(f) GG aeronautical
information services messages;
(g) KK aeronautical
administrative messages; and
(h) As appropriate service
messages.
The
order of priority shall be the same as specified in previous item.
An
addressee indicator, which shall be immediately preceded by a SPACE, except
when it is the first address indicator of the second or third line of
addresses, shall comprise:
(a) The four-letter location
indicator of the place of destination;
(b) The three-letter
designator identifying the organization/function (aeronautical authority,
service or aircraft operating agency) addressed; and
(c) An additional letter,
which shall represent a department, division or process within the organization/function
addressed. The letter X shall be used to complete the address when explicit
identification is not required.
174.609
Message be addressed to an organization
Where a message is to be addressed to an organization that has not been
allocated an ICAO three-letter designator; the location indicator of the place
of destination shall be followed d by the ICAO three-letter Designator YYY (or
the ICAO three-letter designator YXY in the case of a military service or
organization). The name of the addressee organization shall then be included in
the first item in the text of the message. The eighth position letter following
the ICAO three-letter designator YYY or YXY shall be the filler letter.
174.611
Message be addressed to an aircraft in flight
Where a message is to be addressed to an aircraft in
flight and, therefore, requires handling over the AFTN for part of its routing
before retransmission over the Aeronautical Mobile Service, the location
indicator of the aeronautical station
which is to relay the message to the aircraft shall be followed by the ICAO
three-letter designator ZZZ. The identification of
the aircraft shall then be included in the first item of the text of the
message. The eighth position
letter following the ICAO three-letter designator ZZZ shall be the filler
letter
The complete address shall be restricted to three lines of page-printing
copy, as provided in a separate addressee indicator shall be used for each
addressee whether at the same or different locations.
174.615
The completion of the addressee indicator
The completion of the addressee indicator group(s) in the address of a
message shall be immediately followed by the alignment function.
174.617
Messages offered on page copy
Where
messages are offered in page-copy form for transmission and contain more
addressee indicators than can be accommodated on three lines of a page copy,
such messages shall be converted, before transmission, into two or more
messages, each of which shall conform to the provisions as 174.615. During such
conversion, the addressee indicators shall, in so far as practicable, be
positioned in the sequence which will ensure that the minimum number of
retransmissions will be required at subsequent communication centres.
The
origin shall comprise:
(a) Filing time;
(b) Originator indicator;
(c) Priority alarm (when necessary);
(d) Optional heading information;
(e) Alignment function [<≡]; and
(f) start-of-text character, character 0/2
(STX).
The
filing time shall comprise the 6-digit date-time group indicating the date and
time of filing the message for transmission.
174.623
The originator indicator
The
originator indicator, which shall be immediately preceded by a SPACE, shall
comprise:
(a)
The eighth position letter following the ICAO three-letter;
(b) The four-letter location
indicator of the place at which the message is originated;
(c)
The three-letter designator identifying the organization/ function
(aeronautical authority, service or aircraft operating agency) which originated
the message; division or process within the organization/function of the
originator. The letter X shall be used to complete the address when explicit
identification is not required; and
(d) An additional letter
which shall represent a department, organization/function of the originator.
The letter X shall be used to complete the address when explicit identification
is not required.
174.625 Message originated by an organization
Where
a message is originated by an organization that has not been allocated an ICAO
three-letter designator, the location indicator of the place at which the
message is originated shall be followed immediately by the ICAO three-letter
designator YYY followed by the filler letter X (or the ICAO three-letter
designator YXY followed by the filler letter X the case of a military service or organization). The name
of the organization (or military service) shall then be included in the first
item in the text of the message.
174.627 Messages relayed
over the AFTN
Messages
relayed over the AFTN that have been originator indicator that has been agreed
for use by the relay or gateway function linking the AFTN with the external
network.
174.529 Message originated by an aircraft in flight
and requesting handling over AFTN
Where
a message originated by an aircraft in flight requires handling on the AFTN for
part of its routing before delivery, the originator indicator shall comprise
the location indicator of the aeronautical station responsible for transferring
the message to the AFTN, followed immediately by the ICAO three-letter
designator ZZZ followed by the filler letter X. The identification of the
aircraft shall then be included in the first item in the text of the message.
The
priority alarm shall be used only for distress messages. When used it shall
consist of five successive BEL (0/7) characters.
174.633
The inclusion of optional data
The
inclusion of optional data in the origin line shall be permitted provided a
total of 69 characters is not exceeded and subject to agreement between the
administrations concerned.
174.635
The presence of the optional data
The
presence of the optional data field should be indicated by one occurrence of
the space character and terminated by the alignment function.
174.637
Exchanging of additional addressing information
When
additional addressing information in a message needs to be exchanged between
source and destination addresses, it should be conveyed in the optional data
field (ODF), using the following specific format:
(a) Characters one and full
stop (1.) to indicate the parameter code
for the additional address function;
(b) Three modifier
characters, followed by an equal sign (=)and the assigned 8-character ICAO
address; and
(c) The character hyphen (-)
to terminate the additional address parameter field
.
When
a separate address for service messages or inquiries is different from the
originator indicator, the modifier SVC should be used.
The
origin line shall be concluded by an alignment function [<≡] and the
start-of-text (STX) (0/2) character.
The text of messages shall be drafted in accordance with 174.303 and
shall consist of all data between STX and ETX.
174.645
Originator’s reference
When
an originator’s reference is used, it shall appear at the beginning of the
text.
174.647
ICAO three-letter designators
When
the ICAO three-letter designators YXY, YYY or ZZZ comprise the second element
of the addressee indicator and it, therefore, becomes necessary to
identify in the text the specific addressee of the message, such identification
group shall precede the originator’s reference (if used) and become the first
item of the text.
174.649
ICAO three-letter designators
When
the ICAO three-letter designators YXY, YYY or ZZZ comprise the second element
of the originator indicator and it thus becomes necessary to identify in the
text the name of the organization (or military service) or the aircraft which
originated the message, such identification shall be inserted in the first item
of the text of the message.
174.651
ICAO three-letter designator(s)
Where
the ICAO three-letter designator(s) YXY,
YYY, ZZZ refer to two or more different organizations (or military services),
the sequence of further identification in the text shall correspond to the
complete sequence used in the address and originator indicator of the message.
In such instance, each addressee identification shall be followed immediately
by an alignment function. The name of the (YXY, YYY or ZZZ) organization
originating the message shall then be preceded with “FROM”. “STOP” followed by
an alignment function shall then be included in the text at the end of this
identification and preceding the remainder of text.
An
alignment function shall be transmitted at the end of each printed line of the
text. When it is desired to confirm a portion of the text of a message in
teletypewriter operation, such confirmation shall be separated from the last
text group by an alignment function [<≡], and shall be indicated by
the abbreviation CFM followed by the portion being confirmed.
174.655
Corrections on page copy
Stations
shall make all indicated corrections on the page-copy prior to local delivery
or a transfer to a manually operated circuit.
The
text of messages entered by the AFTN origin station shall not exceed 1 800
characters in length. AFTN messages exceeding 1 800 characters shall be entered
by the AFTN origin station in the form of separate messages.
When messages or data are
transmitted only on medium or high speed circuits the text may be increased to
a length that exceeds 1 800 characters as long as performance characteristics
of the network or link are not diminished and subject to agreement between the
Administrations concerned.
The
ending of a message shall comprise the following in the order stated : An
alignment [<ß] function following the last line of text page-feed character, character 0/11 (VT); end-of-text character 0/3 (ETX).
174.661
Station terminal equipment (page printers)
Station
terminal equipment (page printers) on the International Alphabet Number 5
(IA-5) shall be provided with a capability to generate sufficient line feed
functions for local station use upon the reception of a VERTICAL TAB character
(0/11).
174.663
Message does not transit ITA-2
When
the message does not transit ITA-2 portions of the AFTN, or where
Administrations have made provisions to add automatically and shall have a text
comprising:
Messages
entered by the AFTN origin station shall not exceed 2 100 characters in length.
174.667
Procedures for messages using IA5 cod
Except
as provided in 174.669, .673 and .675 the procedure of 174.489 and .491 shall
be used for messages IA5 code.
174.669 Through 174.677 Reserved
174.679
Transfer of AFTN messages
Transfer
of AFTN messages over code and byte independent circuits and networks When AFTN
messages are transferred across code and byte independent circuits and networks
of the AFS, the following shall apply.
174.681
Starting of the messages
The
heading line of the message shall be omitted. The message shall start with an
alignment function followed by the address.
174.683
The end of the messages
The message shall end with a complete ending.
174.685
The purposes of technical supervision
For
the purposes of technical supervision, entry centres should be permitted to
insert additional data preceding the first alignment function and/or following
the ending of the message. Such data may be disregarded by the receiving
station.
When
the provisions of 174.685 are applied, the data added shall not include either
carriage return or line feed characters or any of the combinations listed in
Roman numerals
174.689
The ATS message handling service
The
ATS message service of the ATS (air traffic services) when it is implemented it
will be according to message handling service (ATSMHS) application shall be
used to exchange ATS messages between users over the aeronautical
telecommunication network (ATN)
internet.
174.691
Inter-Centre Communications (ICC)
When
it is implemented it will be according to The inter-centre communications (ICC)
applications set shall be used to exchange ATS messages between air traffic
service messages between air traffic
service users over the ATN internet.
Note 1: The ICC
applications set enables the exchange of information in support of the
Following operational
services:
(a) Flight notification;
(b) Flight coordination;
(c) Transfer of control and communications;
(d) Flight planning;
(e) Airspace management; and
(f) Air traffic flow management.
174.693
The highest standard of discipline
In
all communications the highest standard of discipline shall be observed at all
times.
174.695
ICAO standardized phraseology
ICAO standardized phraseology shall be used in all situations for which
it has been specified. Only when standardized phraseology cannot serve an
intended transmission, plain language shall be used.
174.697 The transmission of
messages
The
transmission of messages, on aeronautical mobile frequencies when the
aeronautical fixed services are able to serve the intended purpose, shall be avoided.
In
all communications, the consequences of human performance which could affect
the accurate reception and comprehension of messages should be taken into
consideration.
174.701Test signals
Where it is necessary for an aircraft station to send signals for testing
or adjustment which are liable to interfere with the working of a neighbouring
aeronautical station the consent of the station shall be obtained before such
signals are sent. Such transmissions shall be kept to a minimum.
When
it is necessary for a station in the aeronautical mobile service to make test
signals, either for the adjustment of a transmitter before making a call or for
the adjustment of a receiver, such signals shall not continue for more than 10
seconds and shall be composed of spoken numerals (ONE, TWO, THREE, etc.) in
radiotelephony, followed by the radio call sign of the station transmitting the
test signals. Such transmissions shall be kept to a minimum
Except
as otherwise provided, the responsibility of establishing communication shall
rest with the station having traffic to transmit.
After
a call has been made to the aeronautical station, a period of at least 10
seconds should elapse before a second call is made. This should eliminate
unnecessary transmissions while the aeronautical station is getting ready to
reply to the initial call.
174.709 When an aeronautical station is called
simultaneously by several aircraft stations
When
an aeronautical station is called simultaneously by several aircraft stations,
the aeronautical station shall decide the order in which aircraft shall
communicate.
174.711
Communications between aircraft stations
In
communications between aircraft stations, the duration of communication shall
be controlled by the aircraft station which is receiving, subject to the
intervention of an aeronautical station. If such communications take place on
an ATS frequency, prior permission of the aeronautical station shall be
obtained. Such requests for permission are required for brief exchanges.
174.713 The categories of messages handled by the
aeronautical mobile service
The
categories of messages handled by the aeronautical mobile service and the order of priority in the establishment of communications
and the transmission of messages shall be in accordance with the following
table. Message category and Radiotelephony order
of priority signal
(a) Distress calls, distress messages and
distress traffic MAYDAY;
(b) Urgency messages, including PAN, PAN messages
preceded by the or PAN, PAN;
(c) Medical transports signal MEDICAL
(d) Communications relating to direction
finding;
(e) Flight safety messages;
(f) Meteorological messages; and
(g) Flight regularity messages.
Distress messages
and distress traffic be handled in accordance with ECAR Part 173.
Urgency messages and urgency traffic,
including messages preceded by the medical transports signal, be handled in
accordance with ECAR Part 173.
174.719
Flight safety messages
Flight safety messages shall comprise the
following:
(a) Movement and control
messages
(b) Messages originated by an
aircraft operating agency or by an aircraft, of immediate concern to an
aircraft in flight;
(c) Meteorological advice of immediate concern to an
aircraft in flight or about to depart (individually communicated or for
broadcast);
(d) Other
messages concerning aircraft in flight or about to depart.
174.721
Meteorological messages
Meteorological
messages shall comprise meteorological information to or from aircraft
174.723
Flight regularity messages
Flight
regularity messages shall comprise the following:
(a) Messages
regarding the operation or maintenance of facilities essential for the safety
or regularity of aircraft operation;
(b) Messages concerning the servicing of
aircraft;
(c) Instructions to aircraft operating agency
representatives concerning changes in
requirements for passengers and crew caused by unavoidable deviations
from normal operating schedules. Individual requirements of passengers or crew
shall not be admissible in this type of
message
(d) Messages
concerning non-routine landings to be made by the aircraft;
(e) Messages
concerning aircraft parts and materials urgently required; and
(f) Messages
concerning changes in aircraft operating schedule.
174.725
messages having the same priority
Messages
having the same priority should, in general, be transmitted in the order in
which they are received for transmission.
174.727
Incomplete transmissions
If
a message has not been completely transmitted when instructions to cancel are
received, the station transmitting the message shall instruct the receiving
station to disregard the incomplete transmission. This shall be effected in
radiotelephony by use of an appropriate phrase.
174.729
Held pending correction
When
a completed message transmission is being held pending correction and the
receiving station is to be informed to take no forwarding action, or when
delivery or onward relay cannot be accomplished, transmission should be
cancelled. This should be affected in radiotelephony by the use of an
appropriate phrase.
The
station cancelling a transmission shall be responsible for any further action
required.
The
air-ground radiotelephony communications shall be conducted in the language
normally used by the station on the ground or in the English language.
The
English language shall be available, on request from any aircraft station, at
all stations on the ground serving designated airports and routes used by
international a
services. Publications
and other published aeronautical information concerning such facilities.
The
languages available at a given station on the ground shall form part of the
Aeronautical Information
Word
spelling in radiotelephony: When proper names, service abbreviations and words
of which the spelling is doubtful are spelled out in radiotelephony the
alphabet in Figure
All
numbers shall be transmitted by pronouncing each digit separately.
All
numbers used in the transmission of altitude, cloud height, visibility and
runway visual range RVR) information, which contain whole hundreds and whole
(thousands, shall be transmitted by pronouncing each digit in the number of
hundreds or thousands followed by the
word HUNDRED or THOUSAND as appropriate. Combinations of thousands and whole hundreds shall be transmitted by
pronouncing each digit in the number of thousands followed by the word THOUSAND followed by the
number of hundreds followed by the word
HUNDRED.
Numbers
containing a decimal point shall be transmitted as with the decimal point in
appropriate sequence being indicated by the word DECIMAL.
When
it is desired to verify the accurate reception of numbers the person
transmitting the message shall request the person receiving the message to read
back the numbers.
174.749
Transmission of numbers
When
the language used for communication is English, numbers shall be transmitted
using the following pronunciation: Numeral or numeral element Pronunciation:
0 ZE-RO
1 WUN
2 TOO
3 TREE
4 FOW-er
5
6 SIX
7 SEV-en
8 AIT
9 NIN-er
Decimal DAY-SEE-MAL
Hundred HUN-DRED
Thousand TOU-SAND
Transmissions
shall be conducted concisely in a normal conversational tone.
174.753
Speech transmitting technique
Speech
transmitting technique should be adapted to the prevailing communications
conditions.
The
following words and phrases shall be used in radiotelephony communications as
appropriate and shall have the meaning ascribed hereunder:
174.759Messages
handled entirely by the aeronautical mobile service
Messages
handled entirely by the aeronautical mobile service shall comprise the
following parts in the order stated:
(a) Call indicating
the addressee and the originator
(b) Text
174.759
Messages requiring handling by the AFTN
Messages
requiring handling by the AFTN for part of their routing and similarly messages
which are not handled in accordance with predetermined distribution
arrangements.
174.761
Messages originated in an aircraft
When
originated in an aircraft:
(a) Call
(b) The word FOR;
(c) The name of the
organization addressed;
(d) The name of the
station of destination;
(e) The text.
174.763
Specification of the text
The
text shall be as short as practicable to convey the necessary information; full
use shall be made of ICAO phraseologies
174.765 Message to be
addressed to an aircraft in flight
When
a message, prepared in accordance with ICAO message format is retransmitted by
an aeronautical station to an aircraft in flight, the heading and address of
the AFTN message format shall be omitted during the retransmission on the
aeronautical mobile service.
174.767
The aeronautical mobile service transmission
The aeronautical mobile service message transmission shall comprise:
(a)
The text [incorporating any corrections (COR) contained in
the AFTN message];
(b)
The word FROM;
(c)
The name of the originating organization and its location (taken from the
origin section of the AFTN message).
174.769 Call sign of the aeronautical mobile service
Aeronautical
stations in the aeronautical mobile service shall be identified by:
(a) The name of the
location; and
(b) The unit or
service available.
The
unit of service shall be identified in accordance with the table below except that the
name of the location or the unit/service may be omitted provided location or
the unit/service may be omitted provided
Satisfactory communication has been establish. Unit/service
available Call sign suffix
area control centre
CONTROL
approach control APPROACH
approach control radar
arrivals ARRIVAL
approach control radar
departures DEPARTURE
operating agency,
followed by at least the last
aerodrome control TOWER
surface movement control
GROUND
radar (in general) RADAR
precision approach radar
PRECISION
direction-finding station
HOMER
flight information
service INFORMATION
clearance delivery
DELIVERY
apron control APRON
company dispatch DISPATCH
aeronautical station
RADIO
174.773
Types of aircraft identification
An aircraft radiotelephony call sign shall be
one of the following types:
Type a) the characters
corresponding to the registration marking of the aircraft; or
Type b) the telephony
designator of the aircraft operating agency, followed by the last four
characters of the registration marking of the aircraft;
Type c) the telephony
designator of the aircraft operating agency, followed by the flight
Identification.
174.775 Abbreviated call
signs
The aircraft radiotelephony call signs shown
with the in exception of Type c may be abbreviated in the circumstances
.Abbreviated call signs shall be in the following form:
Type a) the first
character of the registration and at least the last two
characters of the call sign;
Type b) the telephony designator
of the aircraft operating agency, followed by at least
the last two characters of the call sign;
Type c) no abbreviated
form.
174.777
Radiotelephony procedures
An aircraft shall not change the type of its
radiotelephony call sign during flight, except temporarily on the instruction
of an air traffic control unit in the interests of safety.
174.779
Precautions for the safety
Except for reasons of safety no transmission shall
be directed to an aircraft during take-off, during the last part of the final
approach or during the landing roll.
174.781
Intervals of using full radio call sign
Full radiotelephony call signs shall always be
used when establishing communication. The calling procedure of an aircraft
establishing communication shall be in accordance with radiotelephony
calling procedure
Type a) Type b)
Type c) Designation of the station called NEW YORK
RADIO NEW YORK RADIO NEW YORK RADIO Designation of the
station calling GABCD** SPEEDBIRD ABCD**
AEROFLOT 321**
* In certain cases
where the call is initiated by the aeronautical station, the call may be
effected by transmission of coded tone signals. ** With the exception of the telephony
designators and the type of aircraft, each character
in the call sign shall be spoken separately. When individual letters are
spelled out, the radiotelephony spelling
alphabet.
174.783
The replay for the calls
The reply to the above calls shall be in
accordance with mentioned above
Type a) Type b) Type c) Designation of the station called GABCD* SPEEDBIRD
ABCD* AEROFLOT 321*
Designation of the
answering station NEW YORK RADIO NEW YORK RADIO NEW YORK RADIO
Invitation to proceed
with Transmission GO AHEAD GO AHEAD GO AHEAD
* With the exception of
the telephony designators and the type of aircraft, each character in the call
sign shall be spoken separately. When individual letters
are spelled out, the radiotelephony spelling alphabet shall be used. Numbers
are to be spoken.
Communications
shall commence with a call and a reply when it is desired to establish contact, except that, when it is certain that the
station called will receive the call, the calling station may transmit the
message, without waiting for a reply from the station called.
174.787
Abbreviated radiotelephony call signs communication
Abbreviated
radiotelephony call signs shall be used only after satisfactory communication
has been established and provided that no confusion is likely to
arise. An aircraft station shall use its abbreviated call sign only after it
has been addressed in this manner by the aeronautical station.
174.789
After contact has been established
After
contact has been established, continuous two-way communication shall be permitted without further identification or call
until termination of the contact.
174.791 In order to avoid
confusion
In
order to avoid any possible confusion, when issuing ATC clearances and reading
back such clearances, controllers and pilots shall always add the call sign of
the aircraft to which the clearance applies.
174.793
Exchange of communications
Communications
shall be concise and unambiguous, using standard phraseology whenever
available.
174.795
Abbreviated procedures
Should
only be used after initial contact has been established and where no confusion
is likely to arise.
174.797
Acknowledgement of receipt.
The
receiving operator shall make certain that the message has been received
correctly before acknowledging receipt.
174.799
contents of acknowledgement
When
transmitted by an aircraft station, the acknowledgement of receipt of a message shall comprise the call sign of that aircraft.
174.801 Acknowledgement of
receipt.
When acknowledgement of receipt is transmitted by an aeronautical
station:
(a) To an aircraft station: it shall comprise
the call sign of the aircraft, followed if considered
necessary by the call sign of the aeronautical station;
(b) To another aeronautical station: it shall
comprise the call sign of the aeronautical station
that is acknowledging receipt.
End
of conversation. A radiotelephone conversation shall be terminated by the
receiving station using its own call sign.
When
an error has been made in transmission, the word “CORRECTION” shall be spoken,
the last correct group or phrase repeated, and then the correct version
transmitted.
If
a correction can best be made by repeating the entire message, the operator
shall use the phrase CORRECTION, I SAY AGAIN” before transmitting the message a
second time.
When
an operator transmitting a message considers that reception is likely to be difficult, he should transmit the important elements
of the message twice.
If
the receiving operator is in doubt as to the correctness of the message
received, he shall request repetition either in full or
in part.
If
repetition of an entire message is required, the words “SAY AGAIN” shall be spoken. If repetition of a portion of a message is
required, the operator shall state: “SAY AGAIN
ALL BEFORE...(first word satisfactorily received)”; or “SAY AGAIN (word before
missing portion) TO...(word after missing portion)”; or “SAY AGAIN ALL AFTER... (last
word satisfactorily received)”.
Specific
items should be requested, as appropriate, such as “SAY AGAIN ALTIMETER”,
“SAY AGAIN WIND”.
If,
in checking the correctness of a Read back, an operator notices incorrect
items, he shall transmit the words “NEGATIVE I SAY
AGAIN” at the conclusion of the read back followed by
the correct version of the items concerned.
174.819 Communications watch/ Hours of service during flight
Communications watch/ Hours of service During flight, aircraft stations shall maintain watch as required by the appropriate Authority and
shall not cease watch, except for reasons of safety,
without informing the aeronautical station(s) concerned.
174.821 Watching hours service
Aeronautical
stations shall maintain watch as required by the appropriate Authority.
174.823
Suspension of operation
When
it is necessary for an aircraft station or aeronautical station to suspend
operation for any reason, it shall, if possible, so inform other stations
concerned, giving the time at which it
is expected that operation will be resumed. When operation is resumed, other
stations concerned shall be so informed.
174.825
Suspension of operation
When it is necessary to suspend operation
beyond the time specified in the original notice, a revised time of resumption
of operation shall, if possible, be transmitted at or near the time first
specified.
174.827
Operational frequency for an aircraft
Aircraft
stations shall operate on the appropriate radio frequencies.
174.829
Operation frequency for the aeronautical radio station
The
air-ground control radio station shall designate the frequency(ies) to be used
under normal conditions by aircraft
stations operating under its control.
174.831
The consideration for designating radio frequency
An
aeronautical station, when designating frequencies should take into account the
appropriate propagation data and distance over which communications are
required.
174.833
Action be taken if the designated frequency proves unsuitable
If a
frequency designated by an aeronautical station proves to be unsuitable,
the aircraft station should suggest an
alternative frequency.
174.835
Establishment of communications
Aircraft stations shall, if possible,
communicate directly with the air-ground control radio station appropriate to
the area in which the aircraft are flying. If unable to do so, appropriate
aircraft stations shall use any relay means available and to transmit messages
to the air-ground control radio station
174.837 In case of communication from aeronautical
station cannot be established
When
normal communications from an aeronautical station to an aircraft station
cannot be established, the aeronautical station shall use any relay means
available and appropriate to transmit
messages to the aircraft station. If these efforts fail, the originator shall
be advised in accordance with procedures prescribed by the appropriate
Authority.
174.839
Transferred communication
An
aircraft station which has transferred communications watch from one radio
frequency to another shall, when so required by the appropriate ATS Authority,
inform the aeronautical station concerned that communications watch has been
established on the new frequency.
174.841
Transferred communication
An
aircraft shall be advised by the appropriate aeronautical station to transfer
from one radio frequency to another in accordance with agreed procedures. In
the absence of such advice, the aircraft station shall notify the appropriate
aeronautical station before such a transfer takes place.
174.843
After establishing initial call
When
establishing initial contact on, or when leaving, a VHF frequency, an aircraft
station shall transmit such information as may be prescribed by the appropriate
Authority.
174.845
Communications failure (Air-ground)
When an
aircraft station fails to establish contact with the aeronautical station on
the designated frequency, it shall attempt to establish contact on another
frequency appropriate to the route. If this attempt fails, the aircraft station
shall attempt to establish communication with other aircraft or other
aeronautical stations on frequencies appropriate to the route. In addition, an
aircraft operating within a network shall monitor the appropriate VHF frequency
for calls from nearby aircraft.
174.847 Communications
failure -Air-ground
If the
attempts specified under ECAR845 fail, the aircraft station shall transmit its
message twice on the designated frequency (ies), proceeded by the phrase
“TRANSMITTING BLIND” and, if necessary, include the addressee(s) for which the
message is intended.
174.849 Action be taken in case of an aircraft
station unable to establish communication
When an
aircraft station is unable to establish communication due to receiver
failure, it shall transmit reports at
the scheduled times, or positions, on the frequency in use, preceded by the phrase “TRANSMITTING BLIND
DUE TO RECEIVER FAILURE”. The aircraft station shall transmit the intended
message, following this by a complete repetition During this procedure, the
aircraft shall also advise the time of its next intended transmission.
174.851
Action be taken by the pilot in command
An aircraft which
is provided with air traffic control or advisory service shall, transmit
information regarding the intention of the pilot-in-command with respect to the
continuation of the flight of the aircraft.
174.853
Aircraft unable to establish communication
When an
aircraft is unable to establish communication due to airborne equipment failure
it shall, when so equipped, select the appropriate SSR code to indicate radio
failure.
174.855Ground-to-air
communication
When
an aeronautical station has been unable to establish contact with an aircraft
station after calls on the frequencies on which the aircraft is believed to be
listening, it shall
(a) Request other
aeronautical stations to render assistance by calling the aircraft and relaying
traffic, if necessary;
(b) Request
aircraft on the route to attempt to establish communication with the aircraft
and relay traffic, if necessary.
174.857 Action be taken by
the aeronautical station
The
provisions 174.855 shall also be applied:
(a) On request of
the air traffic services unit concerned;
(b) When an
expected communication from an aircraft has not been received within a time
period such that the occurrence of a communication failure is suspected.
If
the attempts specified in 174.859 fail, the aeronautical station should
transmit messages addressed to the aircraft, other than messages containing air
traffic control clearances, by blind transmission on the frequency(ies) on
which the aircraft is believed to be
listening.
Blind
transmission of air traffic control clearances shall not be made to aircraft,
except at the specific request of the originator.
174.863
Radio communication failure
The
air-ground control radio station shall notify the appropriate air traffic
services unit and the aircraft operating agency, as soon as possible, of any
failure in air-ground communication.
174.865
Distribution of air reports
The
aeronautical station receiving an air report or a message containing
meteorological information transmitted by an aircraft in flight shall forward
the message without delay:
(a)
To the air traffic services unit and meteorological offices associated with the
station;
(b)
To the aircraft operating agency concerned or its representative when that
agency has made a specific request to receive such messages.
174.867 Forwarding messages
to an aircraft in flight
When a message addressed to an aircraft in
flight is received by the aeronautical station included in the address, and
when that station is not able to establish communication with the aircraft to
which the message is addressed, the message should be forwarded to those
aeronautical stations on the route which may be able to establish communication
with the aircraft.
174.869
Unable to dispose the messages
If
the aeronautical station to which the message is addressed is unable to dispose
of the message and the station of origin should be advised.
174.871
The aeronautical station forwarding the message
The
aeronautical station forwarding the message shall amend the address thereof, by substituting for its own location indicator the
location indicator of the aeronautical station to
which the message is being forwarded.
174.873
Distress and urgency messages
Distress
and urgency traffic shall comprise all radiotelephony messages relative to the distress
and urgency conditions respectively. Distress and urgency conditions are defined as:
(a) Distress: a
condition of being threatened by serious and/or imminent
danger and of requiring immediate assistance.
(b) Urgency: a
condition concerning the safety of an aircraft or
other vehicle, or of some person on board or within sight,
but which does not require immediate assistance.
174.875
Distress and urgency signals
The radiotelephony distress signal MAYDAY and
the radiotelephony urgency the radiotelephony urgency Signal PAN PAN shall be
used at the commencement of the first distress and
urgency communication respectively.
174.877
Distress and urgency signals
At the commencement of any subsequent
communication in distress and urgency traffic, it shall be permissible to use
the radiotelephony distress and urgency signals.
174
The originator of messages addressed to an
aircraft in distress or urgency condition shall restrict to the minimum the
number and volume and content of such messages as required by the condition.
If no acknowledgement of the distress or
urgency message is made by the station addressed by the
aircraft, other stations shall render assistance.
174.883
Distress and urgency frequencies
Distress and urgency traffic shall normally be
maintained on the frequency on which such traffic was
initiated until it is considered that better assistance can be provided by
transferring that traffic to another frequency.
174.885
Rate of speed for distress and urgency
messages
In cases of distress and urgency
communications, in general, the transmissions by radiotelephony
shall be made slowly and distinctly, each word being clearly pronounced to
facilitate transcription.
174.887
Action by the aircraft in distress
In addition to being preceded by the
radiotelephony distress signal MAYDAY preferably spoken three
times, the distress message to be sent by an aircraft in distress shall:
(a)
Be on the air-ground frequency in use at the time;
(b)
Consist of as many as possible of the following elements Spoken distinctly and, if possible, in the
following order:
(1) Name of the station addressed (time and
Circumstances permitting);
(2) The identification of the aircraft;
(3) The nature of the distress condition;
(4) Intention of the person in command;
(5)
Present position, level (i.e. flight level, altitude, etc., as appropriate) and
heading.
174.889 First
station acknowledging the distress
The station addressed by aircraft in distress,
or first station acknowledging the distress message,
shall:
(a)
Immediately acknowledge the distress message;
(b)
Take control of the communications or specifically and clearly
transfer that responsibility, advising the aircraft if
(c)
Transfer is made;
(d)
Take immediate action to ensure that all necessary information
is made available, as soon as
possible, to:
(1)
The ATS unit concerned;
(2)
The aircraft operating agency concerned, or its representative, in accordance
with
pre-established arrangements.
The station in distress,
or the station in control of distress traffic, shall be permitted to impose silence, either on all stations of the mobile
service in the area or on any station which interferes with the distress
traffic. It shall address these instructions “to all stations”, or to one
station only, according to circumstances. In either case, it shall use:
-STOP TRANSMITTI
-the radiotelephony
distress signal MAYDAY
174.893 Station using the
distress and urgency signals
The use of the signals MAY DAY or PAN PAN
shall be reserved for the aircraft station in
distress and for the station controlling the distress traffic.
Action by all other stations The distress
communications have absolute priority over all other communications, and a
station aware of them shall not transmit on the frequency
concerned, unless:
(a) The distress is
cancelled or the distress traffic is terminated;
(b) All distress
traffic has been transferred to other frequencies;
(c) The station
controlling communications gives permission;
(d) It has itself
to render assistance.
174.897
Station acknowledging the distress
Any station which has knowledge of distress is
being provided. traffic, and which cannot itself assist the
station in distress, shall nevertheless continue listening to such traffic until it is evident that assistance.
174.899
Termination of distress communications
Termination of distress communications and of
silence: When an aircraft is no longer in .distress, it shall transmit a
message cancelling the distress condition.
174.901
Station controlled the distress communication
When the station which has controlled the
distress communication traffic becomes aware that the distress
condition is ended, it shall take immediate action to ensure that this
information is made available, as soon as possible, to:
(a) The ATS unit concerned;
(b)
The aircraft operating agency concerned, or its representative, in accordance
with pre-established arrangements.
The distress communication and silence
conditions shall be terminated by transmitting a
message, including the words “DISTRESS TRAFFIC ENDED”, on the frequency or frequencies being used for the distress traffic.
This message shall be originated only by the station
controlling the communications when, after the reception of the message it is
authorized to do so by the appropriate authority.
174.905
Aircraft reporting the urgency condition
In addition to being preceded by the
radiotelephony urgency signal PAN PAN preferably spoken three times and each
word of the group pronounced as the French word “panne”, the
urgency message to be sent by an aircraft reporting an urgency condition shall:
(a) Be on the air-ground frequency in use at the time; terminated;
(b) Consist of as many as required of the
following elements spoken distinctly and, if possible, in
the following order:
(1) The name of the
station addressed;
(2) The
identification of the aircraft;
(3) The nature of
the urgency condition;
(4) The intention
of the person in command;
(5) Present
position, level (i.e. flight level, altitude, etc., as appropriate) and
heading; and
(6) Any other
useful information.
174.907 Action by the
station addressed or first station acknowledging the urgency message
The
station addressed by an aircraft reporting an urgency condition, or first
station Acknowledging the urgency message, shall:
(a)
Acknowledge the urgency message;
(b)
Take immediate action to ensure that all necessary information is made
available, as soon as possible, to:
)1)
The ATS unit concerned;
)2)
The aircraft operating agency concerned, or its representative, in accordance with
pre-established arrangements;
(c)
If necessary, exercise control of communications.
174.909 Action by all other stations
The urgency
communications have priority overall other communications, except distress, and
all stations shall take care not to interfere with
the transmission of urgency traffic.
174.911 Action by an aircraft used for medical
transport
The use of the signal
shall indicate that the message which follows concerns a protected medical transport pursuant to the 1949 Geneva
Conventions and Additional Protocols.
174.913 Announcing and identifying the medical
transport
For the purpose of
announcing and identifying aircraft used for medical transports, a transmission
of the radiotelephony urgency signal PAN PAN, preferably spoken three times, and each
word of the group pronounced as the French word “panne”, shall be followed by
the radiotelephony signal for medical transports MAY-DEE-CAL,
pronounced as in the French “medical”. The use of the signals described above
indicates that the message which follows concerns a protected medical
transport. The message shall convey the following data:
(a)
The call sign or other recognized means of identification of the medical
transports;
(b)
Position of the medical transports;
(c)
Number and type of medical transports;
(d)
Intended route.
(e)
Estimated time en route and of departure and arrival, as appropriate; and
(f)
Any other information such as flight altitude, radio frequencies guarded,
languages used, and secondary surveillance radar modes and codes.
174.915 Action by the
station addressed or by other stations receiving medical transport
Action by the station
addressed or by other stations receiving a medical transports message shall
apply as appropriate to stations receiving a medical transports message
174.917 Communications related to acts of unlawful
interference
The station addressed by an
aircraft being subjected to an act of unlawful interference, or first station
acknowledging a call from such aircraft, shall render all possible assistance,
including notification of appropriate ATS units as
well as any other station, agency or person in a position to facilitate the
flight.
The text of broadcast
material shall be prepared by the originator in the form desired for transmission.
174.921 Frequencies and schedules
Broadcasts shall be made
on specified frequencies and at specified times.
174.923 Schedules and frequencies of all broadcasts
Schedules and frequencies
of all broadcasts shall be publicized in appropriate documents. Any change in frequencies or times shall be
publicized by NOTAM at least two weeks in advance of the
change.* Additionally, any such change shall, if practicable, be announced on all regular broadcasts for 48 hours
preceding the change and shall be
transmitted once at the beginning and once at the end
of each broadcast.
174.925 Scheduled
broadcasts
Scheduled broadcasts (other than sequential
collective type broadcasts), shall be started at the scheduled
time by the general call. If a broadcast must be delayed, a short notice shall
be transmitted at the scheduled time advising recipients to “stand by” and
stating the approximate number of minutes of
delay
After definite advice has been given to stand by for
a certain period, the broadcast shall not be started
until the end of the standby period.
174.929
Where broadcasts are conducted on a time allotment basis
Where broadcasts
are conducted on a time allotment basis, transmission shall be terminated
by each station promptly at the end of the allotted time period whether or not transmission of all material has been
completed.
174.931
In sequential collective type broadcasts
In sequential
collective type broadcasts: Each station
shall be ready to commence its broadcasts at the
designated time. If for any reason a station does commence its broadcast at the
designated time, the station immediately following in sequence shall wait then
and commence its broadcast at its own designated time.
174.933
Interruption of service
In the event of
interruption of service at the station responsible for a broadcast, the
broadcast shall, if possible, be made by another
station until normal service is resumed. If this is not possible, and the
broadcast is of the type intended for interception by fixed stations, the
stations which are required to copy the broadcasts shall continue to listen on
the specified frequencies until normal service is
resumed.
174.935
Radiotelephone broadcast
Transmissions by
radiotelephone shall be as natural, short and concise as practicable consistent
with clarity.
174.937
Rate of speech on radiotelephone broadcasts
Rate of speech on
radiotelephone broadcasts shall not exceed 100 words per minute.
174.939 Preamble
of the general call
The preamble of
each radiotelephone broadcast shall consist of the general call, station name,
and optionally the time of broadcast (UTC).
Note. — The following
example illustrates the application of this procedure:
(General call) ALL
STATIONS
(The words THIS IS) THIS
IS
(Station name)
(Time of broadcast) TIME,
ZERO ZERO FOUR FIVE