ON L759, FL400, HDG 135, TURNING RIGHT TO LATERAL TRACK 15 NM, THEN DESCENDING TO FL290
11.11 CPDLC
Controller Pilot Datalink Communications (CPDLC) is an application which provides a means of communication between the controller and pilot by the use of datalink, instead of voice RTF communication.
When CPDLC is established, the aircraft communicates with the controller through datalink. Outside the TMA, CPDLC will be the primary means of communication and position reporting. VHF/HF will be back up for communication and position reporting.
In India, CPDLC is operational within Chennai, Kolkata and Mumbai FIRs. Aircraft equipped with datalink, departing from aerodromes within Chennai, Kolkata and Mumbai FIRs have to request and LOGON to VOMF or VECF or VABF prior to leaving the controlled airspace.
When CPDLC is established, aircraft will be instructed to transfer from voice to CPDLC. Phraseology used is
TRANSFER TO CHENNAI OCEANIC CONTROL ON DATALINK (POSITION), MONITOR 126.15 ALTERNATE PRIMARY 17907 SECONDARY 6655
11.12 Interception by Military Aircraft
There are occasions when an aircraft may lose direction and the pilot is unsure of his position. He is supposed to use the PAN PAN signal and contact the controller for directions.
There are also occasions when an aircraft may stray from its planned flight path and if it is not in contact with the controller, it may be considered as an unidentified aircraft. Also, there are possibilities of the strayed aircraft flying into prohibited, restricted or military exercise areas. During such situations, military aircraft may intercept the civil aircraft.
11.12.1 Action by the Intercepting Aircraft
When an aircraft is intercepted, the Interceptor (intercepting aircraft) places itself to the port (left) and slightly above and ahead of the Intercepted aircraft within the field of view of the intercepted aircraft. In the second phase of interception, the Interceptor closes in to the intercepted aircraft for identification. In the third phase, upon identification, the Interceptor will fly away from the intercepted aircraft by a shallow dive.
11.12.2 Action by the Intercepted Aircraft
When an aircraft is intercepted by an Interceptor, it shall immediately
(a) interpret and respond to the visual signals, follow the instructions given by the intercepting aircraft
(b) if possible, immediately notify the appropriate air traffic services unit
(c) attempt to establish radio communication with the intercepting aircraft or with the appropriate intercept control unit, by making a general call on the emergency frequency 121.5 MHz, giving the identity of the intercepted aircraft and the nature of the flight; and if no contact has been established and if practicable, repeating this call on the emergency frequency 243 MHz
(d) if equipped with SSR transponder, select Mode A, Code 7700, unless otherwise instructed by the appropriate air traffic services unit
(e) if any instructions are received from any other source, and these instructions are in conflict to the instructions issued by the intercepting aircraft, ask for clarification but continue to comply with the instructions issued by the intercepting aircraft
11.12.3 Radio Communication between the Intercept Control Unit/Intercepting Aircraft and the Intercepted Aircraft
When an interception is being made, the intercept control unit and the Interceptor shall try to establish two way communications with the intercepted aircraft using the call signs INTERCEPT CONTROL, INTERCEPTOR (call sign) and INTERCEPTED AIRCRAFT on the frequency 121.5 MHz. If this attempt fails, attempts shall be made to communicate with the intercepted aircraft on other frequencies prescribed by the ATS authority or to establish contact through appropriate ATS units.
11.12.4 Phraseology to be Used
The following phraseology shall be used by the Intercepting and Intercepted aircraft:
Table 11.3 Phraseology for use during interception
Intercepting aircraft Intercepted aircraft
Phrase Pronunciation Meaning Phrase Pronunciation Meanin
CALL SIGN KOL SA-IN What is your call sign? CALL SIGN (call sign) KOL SA-IN (call sign) My call sign is (call sign)
FOLLOW FOLLO Follow me WILCO VILL-KO
Understood and will comply DESCEND DEE-SEND Descend for
landing CAN NOT KANN NOTT
Unable to comply YOU LAND YOU LAAND Land at this
aerodrome REPEAT REE PEET
Repeat your instruction PROCEED PRO SEED You may
proceed AM LOST AM LOSST
Position unknown MAY DAY MAY DAY I am in distress
HIJACK HI-JACK I have been hijacked
LAND (place name) LAAND (place name) I request to land at (place name)
DESCEND DEE-SEND I require descent
11.12.5 Visual Signals by Interceptor and Intercepted aircraft
When an Interceptor intercepts a civil aircraft, the Interceptor draws the attention of the intercepted aircraft and passes instructions by visual means if there is no common language over the
RT or the intercepted aircraft is experiencing RT failure. The visual signals to be resorted to by both the Interceptor and the intercepted aircraft are given in the tables below:
Table 11.4 Signals initiated by the Interceptor
Series Intercepting aircraftsignals Meaning Intercepted aircraftsignals Meaning
1 DAY or NIGHT — Rocking aircraft and
flashing navigational lights at irregular intervals (and landing lights in the case of a helicopter) from a position slightly above and ahead of, and normally to the left of, the intercepted aircraft (or to the right if the intercepted aircraft is a helicopter) and, after acknowledgement, a slow level turn, normally to the left, (or to the right in the case of a helicopter) on the desired heading. You have been intercepted. Follow me. DAY or NIGHT — Rocking aircraft, flashing navigational lights at irregular intervals and following.
Understood, will comply.
2 DAY or NIGHT — An abrupt break-away manoeuvre from the intercepted aircraft
consisting of a climbing turn of 90 degrees or more without crossing the line of flight of the intercepted aircraft.
You may proceed.
DAY or NIGHT — Rocking the aircraft.
Understood, will comply.
3 DAY or NIGHT — Lowering landing gear (if fitted), showing steady landing lights and overflying runway in use or, if the intercepted aircraft is a helicopter, overflying the helicopter landing area. In the case of helicopters, the intercepting helicopter makes a landing approach, coming to hover near to the landing area.
Land at this aerodrome.
DAY or NIGHT — Lowering landing gear, (if fitted), showing steady landing lights and
following the
intercepting aircraft and, if, after overflying the runway in use or helicopter landing area, landing is considered safe, proceeding to land.
Understood, will comply.
Table 11.5 Signals initiated by the Intercepted aircraft Series Intercepting aircraft
signals Meaning
Intercepted aircraft
signals Meaning
4 DAY or NIGHT — Raising landing gear (if fitted) and flashing landing lights while
Aerodrome you have designated
DAY or NIGHT — If it is desired that the
intercepted aircraft
Understood, follow me.
passing over runway in use or helicopter landing area at a height exceeding 300 m (1 000 ft) but not exceeding 600 m (2 000 ft) (in the case of a helicopter, at a height exceeding 50 m (170 ft) but not exceeding 100 m (330 ft)) above the aerodrome level, and continuing to circle runway in use or helicopter landing area. If unable to flash landing lights, flash any other lights available.
is
inadequate.
follow the intercepting aircraft to an alternate aerodrome, the
intercepting aircraft raises its landing gear (if fitted) and uses the Series 1 signals prescribed for intercepting aircraft.
If it is decided to release the intercepted
aircraft, the intercepting aircraft uses the
Series 2 signals prescribed for intercepting aircraft. Understood, you may proceed.
5 DAY or NIGHT — Regular switching on and off of all available lights but in such a manner as to be distinct from flashing lights.
Cannot comply.
DAY or NIGHT — Use Series 2 signals
prescribed for intercepting aircraft.
Understood
6
DAY or NIGHT — Irregular flashing of all available lights.
In distress.
DAY or NIGHT — Use Series 2 signals
prescribed for intercepting aircraft.
Understood.
11.12.6 Example of RT Communication between Interceptor and Intercepted aircraft
During interception, it may not be possible to maintain the whole RT conversation in standard phraseology as there are no standard RT phrases for every situation during interception. It is recommended to use available standard ICAO and any supplementary RT phraseology and plain English language.
THIS IS INTERCEPTOR