4.20 Radar and Radio Failure Procedures
4.20.1 In the event of radar failure or loss of radar identification, the radar controller will issue instructions to restore non-radar separation between those aircraft operating with radar separation. As an emergency measure, use of levels spaced by half the applicable separation minimum may be resorted to until standard separation can be restored.
4.20.2 If two-way communication is lost with an identified aircraft, the radar controller will first determine whether or not the aircraft’s receiver is functioning by instructing the aircraft on the frequency in use (and via data link if so equipped) to acknowledge by:
(a)  squawking ident 
(b)  changing transponder code 
(c)  keying the transmitter or 
(d)  making a specific turn 

If the aircraft is observed to make any of the above actions the pilot will be advised that radar control is being continued.
4.20.3 If the above action is unsuccessful, the instructions will be repeated on any available frequencies on which it is believed the aircraft might be listening.
4.20.4 Aircraft on initial/intermediate approach being vectored for the final of a pilot interpreted approach should continue with the approach whilst maintaining the last assigned level until established on the final approach track, and then commence approach.
4.20.5 If two-way communication is lost with an aircraft that has not been identified, the aircraft will, if possible, be identified by requesting the pilot to:
(a)
squawk ident

(b)
change transponder code

(c)
key the transmitter or

(d)
make a turn followed by instructions to regain track

4.20.6 If the aircraft is observed to make any of the above actions the pilot will be advised that the flight has been identified and the pilot will be requested to make a further action to indicate whether or not radar assistance is required. If the pilot confirms by making the agreed action that radar assistance is required, radar control will be continued.
4.20.7 If the aircraft is not observed to make any of the above actions, the instruction will be repeated on any available frequencies on which it is believed the aircraft might be listening, or via data link if equipped.

4.20.8 When it is determined that an aircraft has experienced a complete communications failure, the radar controller will provide radar separation between that aircraft and any other aircraft under radar control unless it is known that non-radar separation exists.
4.20.9 If the aircraft experiencing the communications failure is not identified, radar separation will be applied by the radar controller between aircraft under radar control and any unidentified aircraft observed along the expected route of the aircraft with the communications failure until such time as it is known, or can safely be assumed, that the aircraft with radio failure has passed through the airspace concerned or has landed.
5 AREA OF RADAR COVERAGE
5.1 Radar Coverage
5.1.1 The area of theoretical PSR coverage is provided in Figure ENR 1.6-1.
5.1.2 The area of theoretical SSR coverage is provided in Figure ENR 1.6-2.

Figure ENR 1.6-1
Area of Theoretical PSR Coverage

Effective: 12 APR 07
Figure ENR 1.6-2
Area of Theoretical SSR Coverage

Effective: 12 APR 07