ENR 1.12 INTERCEPTION OF CIVIL AIRCRAFT

1 Interception Procedures

1.1 
The following procedures and visual signals apply over the territory and territorial waters of the Socialist Republic of Viet Nam in the event of interception of an aircraft. An aircraft which is intercepted by another aircraft shall immediately:
  1. Follow the instructions given by the intercepting aircraft, interpreting and responding to visual signals listed in Appendix 2 of Annex 2;
  2. Notify, if possible, the appropriate air traffic services unit;
  3. 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, repeating this call on the emergency frequency 243 MHz, if practicable;
  4. If equipped with SSR transponder, select Mode A, Code 7700, unless otherwise instructed by the appropriate air traffic services unit.
Note:
The word "interception" in this context does not include intercept and escort service provided, on request, to an aircraft in distress, in accordance with the Search and Rescue Manual (Doc 7333 - ICAO).
1.2 
If radio contact is established during interception but communication in a common language is not possible, attempts shall be made to convey instructions, acknowledgement of instructions and essential information by using the phrases and pronunciations in the following table, transmitting each phrase twice:
Phrase
Pronunciation(1)
Meaning
CALL SIGN
(call sign) (2)		KOL SA-IN
(call sign)
My call sign is (call sign)
WILCOVILL-KO
Understood. Will comply
CAN NOTKANN NOTT
Unable to comply
REPEATREE-PEET
Repeat your instruction
AM LOSTAM LOSST
Position unknown
MAYDAYMAYDAY
I am in distress
HIJACK(3)HI-JACK
I have been hijacked
LAND
(Place name)		LAAND
I request to land at
(place name)
DESCENDDEE-SEND
I require descent
Note:
(1) Syllables to be emphasized are printed in bold letter;
(2) The call sign required to be given is that used in radiotelephony communications with air traffic services units and corresponding to the aircraft identification in the flight plan;
(3) Circumstances may not always permit, nor make desirable, the use of the phrase "HIJACK".
1.3 
The phrases shown in the table below shall be used by the intercepting aircraft and transmitted twice in the circumstances described in the preceding paragraph.
Phrase
Pronunciation(1)
Meaning
CALL SIGNKOL SA-IN
What is your call sign?
FOLLOWFOL-LO
Follow me
DESCENDDEE-SEND
Descend for landing
YOU LANDYOU LAAND
Land at this aerodrome
PROCEEDPRO-SEED
You may proceed
(1) Syllables to be emphasized are printed in bold letter.
1.4 
If any instruction received by radio from any sources conflict with those given by the intercepting aircraft by visual signals, the intercepted aircraft shall request immediate clarification while continuing to comply with the visual instructions given by the intercepting aircraft.
1.5 
If instructions received by radio from any sources conflict with those given by the intercepting aircraft by radio, the intercepted aircraft shall request immediate clarification while continuing to comply with the radio instructions given by the intercepting aircraft.
1.6 
The visual signals for use in the event of interception are detailed on page ENR 1.12-3.

2 Signals for use in the event of interception

Signals initiated by intercepting aircraft and responses by intercepted aircraft
Series
INTERCEPTING Aircraft Signals
Meaning
INTERCEPTED Aircraft Responds
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)
After acknowledgement, a slow level turn, normally to the left, (or to the right in the case of a helicopter) on the desired heading.
Note:1.Meteorological conditions or terrain may require the intercepting aircraft to reverse the positions and direction of turn given above in Series1.
Note: 2. If the intercepted aircraft is not able to keep pace with the intercepting aircraft, the latter is expected to fly a series of race‐track patterns and to rock the aircraft each time it passes the intercepted aircraft.
You have been intercepted. Follow me.
DAY or NIGHT– Rocking aircraft, flashing navigational lights at irregular intervals and following.
Note: Additional action required to be taken by intercepted aircraft is prescribed in Annex 2, Chapter 3, 3.8.
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.
Signals initiated by intercepted aircraft and responses by intercepting aircraft
Series
INTERCEPTED Aircraft Signals
Meaning
INTERCEPTING Aircraft Responds
Meaning
4
DAY or NIGHT – Raising landing gear (if fitted) and flashing landing lights while passing over runway in use or helicopter landing area at a height exceeding 300 m (1000 ft) but not exceeding 600 m (2000ft) (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 the runway in use or helicopter landing area. If unable to flash landing lights, flash any other lights available.
Aerodrome you have designated is inadequate.
DAY or NIGHT – If it is desired that the intercepted aircraft 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.
Understood, follow me.
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.