9. Control of Traffic On and In the Vicinity of an Airport

(a) General. Towers shall maintain a continuous guard on all airport traffic under their supervision, and shall control such traffic in accordance with the standards outlined herein.

(b) Determining Proper Runway or Direction To Use for Landings and Take-Offs. The tower shall designate the runway or direction to be used under existing conditions, taking into consideration wind conditions, taxi distances, aircraft characteristics, and other relevant factors.

(c) Control of Airport Traffic

(1) Aircraft in flight shall be individually instructed so as to avoid collision with other airport traffic.

(2) When practicable, taxiing aircraft shall be warned of parked aircraft or other obstructions along or near the taxiing route, and shall be individually instructed to taxi in such manner as will avoid interference with aircraft landing or taking off.

(3) The tower may, pursuant to special local arrangements, omit individual instructions and clearances to aircraft operating under such arrangement. However, individual instructions shall be issued as necessary in the interests of safety or the expeditious movement of air traffic.

(d) Control of Persons and Vehicles on the Airport. The movement of persons or vehicles on the airport shall be controlled by the tower as necessary to avoid hazard to aircraft landing, taxiing, or taking off. (e) Patrol of Water Airports. The tower at a water airport shall include within its functions responsibility for the patrol and policing of the usable surface, and the contracting States shall undertake to insure that the tower has the facilities and authority to discharge this responsibility.

10. Light Signal Procedures. An adequate directional traffic control light shall be used to control the movement of aircraft not equipped with radio, and personnel and vehicles, on the airport as follows:

(a) To Aircraft in Flight

(1) A steady green light from a directional traffic control light shall be used to mean "CLEARED TO LAND”.

(2) A steady red light from a directional traffic control light shall be used to mean "GIVE WAY TO OTHER AIRCRAFT AND CONTINUE CIRCLING”.

(3) A series of red flashes from a directional traffic control light shall be used as a recall signal to indicate to aircraft that it is desired that it return and land. (Light signal to indicate clearance to land must also be given when aircraft is in proper position.)

(4) A series of alternating red and green flashes from a directional traffic control light shall be used as a general warning signal to advise an aircraft to be on the alert for hazardous or unusual conditions.

(b) To Aircraft on the Airport

(1) A steady red light from a directional traffic control light shall be used to mean "STOP".

(2) A series of red flashes from a directional traffic control light shall be used to mean that the aircraft is to be taxied back to the hangar line.

(3) A series of green flashes from a directional traffic control light shall be used to mean "CLEARED TO CONTINUE TAXIING".

(c) To Aircraft in Take-Off Position

(1) A steady red light from a directional traffic control light shall be used to mean "CLEAR THE RUNWAY IMMEDIATELY AND WAIT".

(2) A steady green light from a directional traffic control light shall be used to mean "CLEARED FOR TAKE-OFF".

(d) General Warning Signal. A series of alternating red and green flashes from a directional traffic control light shall be used as a general warning signal to advise persons in command of aircraft, drivers of vehicles, or personnel on the airport to be on the alert for hazardous or unusual conditions. In controlling airport traffic by means of visual signals, the general warning signal shall be directed to the aircraft concerned in accordance with the following:

(1) When aircraft are on converging courses and there is a possibility of collision.

(2) When hazardous conditions are present and the person in command of an aircraft must be unusually alert in order to complete the operation safely. Such conditions include obstructions, soft fields, ice on runway, and similar hazards.

(3) When mechanical trouble is apparent to the tower and there is reason to believe that the person in command of the aircraft may not be aware of such trouble.

(4) When deemed necessary by the tower in the interests of safety.

11. Radiotelephone Communications Procedure and Technique. The operation of the radio facilities of a tower shall be accomplished in accordance with the procedures outlined in Annex B, "Communications Procedures and Systems".

12. Standard Traffic Clearances and Phraseologies

(a) Standard Airport Traffic Clearances. Traffic clearances issued by towers shall conform to the standards which follow. At the discretion of the tower, individual items in the standard clearance form may be omitted if previously given or if not necessary to the proper control of individual aircraft. In transmission of these clearances, standard radio communication procedure and phraseology as prescribed in Annex B, "Communications Procedures and Systems", shall be used.

(1) Clearance To Enter Traffic Pattern. Clearance authorizing an aircraft to enter the traffic pattern at the airport shall be in the following form:

a. Reporting point.

b. Time-minutes only.

c. Altitude in thousands and hundreds of feet.

d. Altimeter setting.

(Above items as reported by the person in command of the aircraft to be repeated by tower.)

e. Clearance to enter the traffic pattern.
f. Specified altitude if necessary.

g. Wind direction and velocity.

Direction or number of runway to be used.

i. Any special instructions or traffic information.

(2) Clearance To Land. Clearance to land shall be in the following form:

a. Position of aircraft.

b. Altitude of aircraft.
c. Altimeter setting.
d. Clearance to land.

e. Direction of landing traffic.

f. Direction or number of runway to be used.

g. Any special instructions or traffic information.

(3) Clearance To Taxi. Clearance to taxi shall be in the following form:

Inbound aircraft.

a. Clearance to specified point (gate, loading ramp, hangar, parking space, et cetera).

b. Any special instructions relative to the use of taxi strips and intersecting runways, or any information relative to obstructions, maintenance operations, or other airport activity or condition.

Outbound aircraft.

a. Altimeter setting and time check.

b. Direction of take-off.

c. Clearance to runway to be used.

d. Any special instructions relative to use of taxi strips and intersecting runways, or any information relative to obstructions, maintenance operations, or other airport activity or field condition.

(4) Clearance for Take-Off. Clearance for take-off shall be in the following form:

a. Any special instructions or information.

b. Clearance for take-off.

The take-off clearance described above shall not be issued to aircraft operating under Instrument Flight Rules until the center's traffic clearance has been transmitted to and acknowledged by the aircraft concerned.

(b) Radio Control of Aircraft Having a Receiver Only. Broadcasts of instructions or information which require acknowledgment from an aircraft which is equipped with a radio receiver only, shall contain provision for such acknowledgment in the following manner:

(1) When the aircraft is on the ground within the range of vision of the tower, instructions shall be included which will require acknowledgment of the broadcast by movement of the ailerons or rudder, whichever action may be observed more readily.

(2) When the aircraft is in the air the same purpose will be achieved by including instructions to acknowledge receipt of the broadcast by rocking the wings.

(3) When the aircraft is either in the air or on the ground, during the hours of darkness, the same purpose will be achieved by requiring the display of landing lights or signal light, as requested by the tower.

(c) Traffic Information. Information concerning the movement of other aircraft shall be issued to aircraft under the supervision of the tower as necessary or as requested to assist the aircraft in avoiding collision.

13. Information on Airport Conditions

(a) General. Information regarding the condition of an airport and associated facilities shall be issued to aircraft as necessary or desirable in the interests of safety.

(b) Types of Information. The following airport conditions shall be included by a tower as essential airport information:

(1) Construction work along or near the runway in use.

(2) Rough or soft portions of the usable surface of the airport, whether marked or not.

(3) Any maintenance apparatus or workmen on or near any portion of the usable surface of an airport which the person in command of an aircraft might elect to use.

(4) Slippery condition of runways or taxiways.

(5) Snow piled or drifted on or adjacent to the usable surface of the airport.

(6) Failure or irregular functioning of any portion of the airport lighting system.

(7) Aircraft parked close to runways or the usable surface of the airport.

(8) Floating objects, buoys, or other obstructions which may be a hazard to aircraft alighting on water.

14. Special Authority of Towers. A tower may invoke the requirements of the Instrument Flight Rules for flight in the airport control sector whenever safety requires such action. Whenever a tower in a control area invokes the requirements of the Instrument Flight Rules, the center for such area shall be notified of the action taken.

SECTION IV

Standards for the Control of Instrument Flight Rules Traffic

15. Application

(a) General. These standards govern the control of aircraft operating in accordance with the Instrument Flight Rules in control areas and airport control sectors.

(b) Special. As determined by one or more States concerned, aircraft flown between sunset and sunrise within specified areas may be controlled in accordance with these standards, regardless of weather conditions.

(c) Authorizing General Flight Rules. When traffic conditions permit, a tower or center shall authorize operation of aircraft in the airport control sector or control area under General Flight Rules when Instrument Flight Rule conditions prevail. Prior to such authorization by a tower located within a control area, the center for such area shall be notified of such intended action.

16. Traffic Clearances. Centers and towers shall issue traffic clearances as follows:

(a) General. Traffic clearances shall be issued to all aircraft flying on instrument flight plans within a control area or airport control sector.

(b) Standard Clearance Form. Traffic clearances shall be issued in accordance with standard phraseologies as set forth in Annex B, "Communications Procedures and Systems". Traffic clearances shall contain the following elements:

(1) Flight or aircraft identification.

(2) Clearance specifying route and clearance limit.
(3) Altitude, approach or departure instructions.
(4) Any special instructions or information.

(5) Message delivery information and/or cancelation time if necessary.

(c) Clearance Limits. A traffic clearance shall cover a specified portion of the control area or airport control sector of the center or tower issuing the clearance, depending upon existing traffic and weather conditions. The point to which an aircraft is granted such a clearance shall be termed a clearance limit, and shall be specifically defined in the clearance. A clearance limit normally shall be either a point of intended landing, a reporting point, or a control boundary. By coordination between centers and towers, clearances shall be combined when practicable.

(d) Altitude Instructions. The altitude instructions in a traffic clearance shall consist of the following:

(1) The cruising altitude or altitudes to be maintained.

(2) Altitudes over those reporting points which are to be crossed at other than cruising altitude.

(3) The place or time for starting climb or descent, and the rate of vertical speed, when necessary for proper control.

(4) Detailed departure or approach altitudes when necessary. (e) Time of Clearance Delivery. A traffic clearance shall be forwarded to the proper agency in sufficient time for transmission to an aircraft before it departs from within or enters a control area or airport control sector. When a traffic clearance has been issued to an aircraft for flight within a portion of a control area or airport control sector and further clearance is required, such further clearance shall be issued before aircraft arrives at the clearance limit.

(f) Cancelation of Clearance. When it is desired to limit the effective time of a traffic clearance, such as one issued for a proposed departure, the clearance shall contain provision for its cancelation at a specified time.