Unlawful Interference
3.4.11 The pilot of an aircraft which is being subjected to unlawful interference, or the threat of unlawful interference, must endeavour to advise ATS of the fact, together with details of any subsequent deviation from the current flight plan and any other significant factors affecting the operation. This enables ATS to give priority to the aircraft and to alert organisations likely to be involved. The following procedures should be followed:
(a)
squawk CODE 7500 MODE A;
(b)
advise ATS of details in plain language if possible;
(c)
if unrestricted use of the radio is not possible, insert the phrase “CHANNEL SEVEN FIVE ZERO ZERO” into any RTF transmission after the aircraft’s callsign if it is safe and practicable to do so.
3.4.12 Whenever it has been established that an aircraft is transponding on code 7500 the controller will attempt to verify by RTF with the aircraft concerned that the code selection is intentional:
“ ... (CALL SIGN) ... CONFIRM SQUAWKING SEVEN FIVE ZERO ZERO”.
3.4.13 If the aircraft is not being subjected to unlawful interference, the pilot should respond to the query by broadcasting that the aircraft is not being subjected to unlawful interference.
3.4.14 If the reply is in the affirmative or if no reply received, this will indicate the aircraft is subjected to unlawful interference.
3.4.15 ATS personnel recognising any indication of unlawful interference to an aircraft will attend promptly to its request. Information pertinent to the safe conduct of the flight will continue to be transmitted and action will be taken to facilitate the conduct of all phases of flight.
Transponder Setting Procedure
3.4.16 ATC radar units are equipped with alarm systems that activate when the aircraft is within radar coverage and the pilot selects the unlawful interference (code 7500), communication failure (code 7600), or emergency transponder code (code 7700).
3.4.17 It is possible to unintentionally select these codes momentarily when changing the transponder from one code to another. To prevent unnecessary activation of the alarm, pilots should set transponders to “STANDBY” while changing transponder codes.
Use of Standby/On/Off
3.4.18 Pilots should set transponders to “STANDBY” while taxiing; then “ON” as late as practicable before take-off; and to “STANDBY” or “OFF” as soon as practicable after landing. In practice, transponders should be turned on only upon entering the active runway for departure and turned off as soon as the aircraft exits the runway after landing.
3.4.19 When turning the transponder on, ensure that the altitude (ALT) selection is made allowing transmission of Mode A (selected code) and Mode C (altitude) data.
3.4.20 Pilots of aircraft operating in the circuit of a controlled aerodrome should only set transponders to “STANDBY” when instructed by ATC, or when such an instruction is included on the aerodrome chart.
3.4.21 Special procedures apply at Auckland INTL; refer Auckland Ground Movements (2) — ALL RWY page.
Use of Mode C for Vertical Separation
3.4.22 When reporting levels under routine procedures or when requested by ATC, pilots must state the current altimeter reading to the nearest 100ft. This enables the verification of Mode C data transmitted by the aircraft.
3.4.23 If there is a difference of more than 200ft between the transponder level readout and the reported level, the pilot will be advised to check the altimeter setting. If the difference continues the pilot will be instructed to switch off Mode C.
3.4.24 After verification, Mode C may be used by ATC to ascertain:
(a)
that aircraft are maintaining assigned levels; or
(b)
that aircraft have vacated, passed, or reached a level.
