(2) By printed notice using an international prescribed standard form.

(b) If the navigation information promulgated by radio is of a permanent nature as well as urgent, a printed notice will be issued as soon as possible to confirm the radio message or broadcast.

(c) It is desirable that a standard method of collecting and coordinating all Notices to Airmen likely to remain in force for some time into a convenient permanent document shall be introduced.

(d) It will also be the responsibility of contracting States where possible to publish detailed information concerning air navigational radio aids, appropriately supplemented by maps and diagrams. In this connection use will be made of Notices to Airmen in order to keep such documents up to date.

8. Deviation From Assigned Frequencies. Procedures are covered in General Radio Regulations (Cairo Revision).

9. Types of Emission and Frequencies. In the radio service of air navigation the types of emission are as specified in General Radio Regulations (Cairo Revision).

(a) The frequencies used shall be fixed by regional arrangements between the countries concerned and within the framework of the international conventions and the regulations in force.

SECTION III

Categories of Messages of the International Communications Service of Air Navigation

10. Distress Messages. General procedures are covered in General Radio Regulations (Čairo Revision).

(a) Distress Action by the Communications Control Station. Upon receipt of a distress message from an aircraft, the communications control station shall forward the information immediately to the air traffic control center and shall take immediate action as follows:

(1) Continue guarding the aircraft frequency last used and as far as possible all other frequencies which may be used by that particular aircraft on the route it is flying. Under no circumstances shall the distress frequency be left unguarded.

(2) Handle any emergency traffic necessary to or from the aircraft. (3) When the distress traffic has ceased and silence is no longer necessary, a message shall be transmitted on the distress frequency to all stations in accordance with procedures outlined in General Radio Regulations (Cairo Revision).

(4) The speed of radiotelegraph transmission of distress communications shall not normally exceed 16 words per minute.

(5) Should facilities for transmission on the international distress frequency not be available at the communications control station, the rescue service, or other agency having the frequency available, shall be requested to transmit the message relative to cessation of distress traffic.

(6) If the communications station is not in an air traffic control area, the communications station shall immediately take action to

place in operation established rescue procedure and shall make full use of available facilities in rendering any possible assistance.

(b) Assistance by Other Aircraft. Any aircraft intercepting a distress call shall repeat it to the communications control station to which it is addressed, if possible, or to another aeronautical ground station, and thereafter shall stand by to act as a relay station if required. Aircraft shall take care not to interfere with distress calls while they are being made, repeated, or answered.

11. Urgency Messages. General procedures are outlined in General Radio Regulations (Cairo Revision).

12. Safety Messages. Procedures are outlined in General Radio Regulations (Cairo Revision).

13. Operational Messages. Operational messages are messages the exchange of which is indispensable for insuring the regularity of air traffic.

(a) They shall contain information or orders relating to the personnel, material, or movements of aircraft (changes of pilots, dispatch of spare parts, an aircraft in regard to its timetable, supplementary landing to be made by an aircraft, reservation messages, et cetera).

14. Urgent Messages. Urgent messages are messages containing important information to be transmitted without delay. This priority classification shall not be used except by authorization of competent authority.

15. Aircraft Movement Messages. The following types of messages shall, in principle, be transmitted in codes:*

(a) Pre-Flight

(1) Warning Message. At least 8 hours before the estimated time of departure of a special or non-scheduled flight, unless it has been agreed a lesser time will suffice, the operating agency shall furnish to the initial control center the relevant items of information, and the control center shall file this information with the aeronautical ground station for transmission to the other control centers serving the route of flight. Control centers shall also notify the responsible meteorological offices.

(2) Flight Plan Message. Prior to departure from an airport within its control area, a proposed flight plan shall be submitted, unless otherwise agreed upon between the operating agency and the control center, to the initial control center for approval.

(3) Delay Message. If the departure of a scheduled flight or a flight for which a warning message has been transmitted is postponed or appreciably delayed with reference to the ETD, the operating agency shall notify the initial control center of the delay in the flight as planned (or previously delayed), furnishing the relevant items of information. The initial control center shall transmit this information to the other control centers in the specified form. Control centers shall also notify the responsible meteorological offices.

(4) Cancelation Message. If a scheduled, non-scheduled or special flight is canceled, the operating agency shall notify the initial control center, furnishing the relevant items of information. The

*In these procedures, the word "codes" refers to authorized word and phrase contractions, authorized identifications, and appropriate digits.

initial control center shall file this information, in the specified form, for transmission to the other control centers concerned with the flight. Control centers shall also notify the responsible meteorological offices and operations officers.

(b) During Flight

(1) Flight Plan Message. Immediately after the departure of an aircraft, the airport traffic control tower, if one is in operation at the point of departure, or the operating agency shall advise the initial control center of the time of departure. The initial control center shall then transmit the approved flight plan, including the departure time, to the other control centers serving the route of flight.

(c) At Intermediate Airports

(1) Arrival Message. As soon as possible after landing, the airport traffic control tower or operating agency at intermediate landing areas shall file an arrival message for transmission to the control centers which previously received the flight plan.

(2) Flight Plans. Flight plans shall be approved prior to departure by the air traffic control center in the immediate control area.

(3) Departure Message. As soon as possible after departure, the operating agency shall notify the control center, and file a departure message with the communications control station for transmission to other control centers serving the route of the flight.

(4) Delay Message. If the departure of an aircraft is postponed or appreciably delayed from ETD as scheduled or as indicated in the warning message, the operating agency shall notify the control center and file a delay message in the specified form with the aeronautical ground station for transmission to other control centers serving the route of the flight. Control centers shall also notify the responsible meteorological offices.

(d) Post Flight

(1) Arrival Message. At the conclusion of each flight, the airport traffic control tower, or the operations officer if there is no tower at the airport, shall file an arrival message in the specified form for transmission to the control centers previously concerned with the flight, which shall pass the information to the operating and service agencies concerned in their control areas.

(e) Request Information Message. An operations officer or control center shall file for transmission to appropriate control centers a "Request Information" message, in the form specified, to secure information concerning the position or progress of an aircraft.

(f) Aircraft Movement Message Forms. The authorized aircraft movement message forms are included in Appendix 1.

16. Reservation Messages. Reservation messages are intended to enable the services of operating agencies to provide the seats or space they will need in aircraft for their passengers or consignors of goods. Reservation messages shall be prepared according to the codes in Appendix 1.

17. Messages Giving Position of Aircraft. Position reports shall be transmitted to the appropriate communications control station in the form specified in Appendix 1, at the scheduled times agreed upon for each flight.

18. Tests. Tests shall be allowed only in so far as they do not disturb the service of other stations,

(a) The test and adjustment signals shall be of such a kind that no confusion can be produced with a signal, abbreviation, et cetera, of special meaning.

(b) Any station making emissions for tests or adjustments shall transmit its call sign at short intervals during the course of these emissions.

SECTION IV

Procedure for the Transmission of Messages

19. Establishing Communication. All stations shall be bound to exchange traffic with the minimum of radiated energy necessary to insure good communication.

(a) Before proceeding with any transmission, the sending station shall make sure that it will not cause excessive interference with other authorized communications in progress within its range on the frequency to be used; if it is likely that such interference will be caused, the station shall await the first break in the transmission with which it might interfere.

(b) If, in spite of this precaution, a radio transmission in progress is impeded by the call, the latter shall cease at the first request from a land station open to the international service of public correspondence or from any aeronautical station. The station which requests this cessation shall indicate the approximate duration of the wait imposed on the station whose call it has stopped.

20. Calling. General procedures are outlined in General Radio Regulations (Cairo Revision).

21. Transmission of Messages by Radiotelegraphy. General procedures are outlined in General Radio Regulations (Cairo Revision). 22. Transmission of Messages by Radiotelephony. General procedures are outlined in General Radio Regulations (Cairo Revision). 23. Change of Frequency or Type of Emission. If the station calling. has indicated that it is going to use for transmission a type of emission and/or a frequency other than those with which it made the call, the station called, in the reply, shall give before the signal. the abbreviations indicating that from that moment onward it will listen on the type of emission and/or the frequency announced.

24. Traffic Codes. Plain language in radiotelegraph transmissions shall be avoided when it can be replaced by codes.

(a) In the exchange of communications all signals and words which are not strictly necessary for the radio service of aeronautics shall be omitted (forms of politeness, et cetera).

25. Service of Direction-Finding Stations for Aeronautics. The aircraft station may request either its D/F bearing or its position. (a) Aircraft Requests Bearing

(1) Bearings given by ground direction-finding stations shall indicate the direction of the aircraft with respect to the ground direction-finding station. The pilot shall specify the type of bearing that is

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desired by the use of the proper "Q" signal. The three operating signals to which reference usually shall be made follow:

a. QDM. What is the magnetic course to steer, with zero wind, to reach you (or

-)?

b. QUJ. What is the true course to steer, with zero wind, to reach you (or

-)?

c. QTE. What is my true bearing in relation to you (or (This is bearing from station to aircraft.)

-)?

(2) The quality and accuracy of D/F bearings may vary under certain circumstances; when such is the case, they shall be qualified by the addition of the class to the operating signal transmitted in reply to a request for a bearing. Classes of bearings shall be as follows:

CLASS 1. Bearings within an accuracy of a plus or minus 3 degrees. CLASS 2. degrees.

Bearings within an accuracy of a plus or minus 5

CLASS 3. Bearings within an accuracy of over a plus or minus 5 degrees.

(b) Aircraft Requests Position

(1) Accurate positions by direction finding can only be determined by two or more stations cooperating with each other as a direction-finding network.

(2) Procedure for requesting a position shall be as follows:

a. The aircraft station shall call the direction-finding station of control on its listening frequency. It shall then transmit "QTF?" which means:

"What is my position by direction finding?”

and shall conclude by indicating, if necessary, the auxiliary frequency which it can use to enable its position to be taken. It shall then await instructions.

b. The direction-finding station called shall request if necessary the direction-finding stations of its group to prepare to take the bearings of the aircraft station, by transmitting QTE, followed by the call sign of the aircraft.

c. As soon as the direction-finding stations are ready, the direction-finding station originally called by the aircraft shall send to the latter QTN, which means:

"Send your call sign followed by a twenty (20) second dash,
repeated
times."

The aircraft shall comply with request in order that bearings
may be taken.
may

d. The direction-finding station or stations which are satisfied with the operation shall transmit to the control station QTE, preceded by the time of the operation and followed by the call sign of the aircraft and by a group of three figures (000 to 359), indicating the bearing obtained, and the indication of quality and accuracy of position by class.

e. If a direction-finding station is not satisfied with the operation, it shall request the aircraft station to repeat the trans