91.249 New Zealand registered aircraft must use one of the following radiotelephony call signs:

(1) The telephony designator of the aircraft operating agency as
approved by the Director(CAA), followed by the flight 
identification; e.g: CHATHAM 84

(2) The telephony designator of the aircraft operating agency as
approved by the Director(CAA) followed by the last 3 letters of the
aircraft registration marking; e.g: CHATHAM DELTA ALPHA MIKE 

(3) The name of the aircraft manufacturer, or the aircraft model, 
and the last 3 letters of the aircraft registration marking.
e.g: CESSNA 152 MIKE DELTA SIERRA

Except for(2)above, the pilot-in-command may, after
establishing two-way communication with an appropriate ATS 
unit, use an abbreviated call sign consisting of the last 3 letters of 
the aircraft registration marking. e.g: MIKE DELTA SIERRA

Section 2.10 (i) Radiotelephony aircraft call signs; 
4.6.2 Aircraft Callsigns
4.6.2.1 Information on aircraft callsigns for operations within New Zealand are contained in RulePart 91.
4.6.2.2 An aircraft callsign does not change during flight except for a temporary period on the instruction of ATC in the interests of safety.

ATC: FASTAIR 345 CHANGE YOUR CALLSIGN TO FASTAIR ALFA TANGO MIKE
A/C: FASTAIR ALFA TANGO MIKE WILCO
ATC: FASTAIR ALFA TANGO MIKE REVERT TO YOUR FLIGHT PLAN CALLSIGN AT (TIME/REP)
A/C: FASTAIR ALFA TANGO MIKE WILCO

The Director may only approve the call signs prescribed in 
paragraphs
(1) and (2) above 
(1) the holder of an air operator certificate issued under Part 119 or 129 conducting

(i) A regular air transport service; or
(ii) A search and rescue flight; or
(iii) A medical transfer or medical emergency flight; and

(2) Aircraft being flown on a police operation that is authorised by
the Commissioner of Police.

An applicant for the approval of a telephony designator must submit to the Director in writing the name of the aircraft operating agency and a payment of the appropriate application fee prescribed by regulations made under the Act.

4.6 Callsigns
4.6.1 Ground Station Callsigns
4.6.1.1 Ground stations are identified by the name of the location followed by the service available
as follows:

CONTROL	Area and approach control, including area and approach radar
APPROACH	Approach control where provided as a separate function
ARRIVAL	Approach control radar arrivals
DEPARTURE	Approach control radar departures
TOWER	Aerodrome control or aerodrome and approach/area control where these services are provided from an aerodrome control tower
GROUND	Surface movement control including clearance delivery
RADAR	Area or approach control radar on a discrete frequency
FLIGHT SERVICE	Aerodrome flight information service (AFIS)
INFORMATION	Area flight information service
DELIVERY	Clearance delivery
RADIO	Air – ground service
UNICOM	UNICOM service

4.6.1.2 The name of the location or the service may be omitted provided that satisfactory
communication has been established.

Use of SSR transponder and altitude reporting equipment

a) PIC must use a transponder in transponder mandatory airspace in mode A, C or S.
Use code assigned by ATC or according to VFR transponder code table 2 below or in an emergency the allocated emergency code.

b) To operate an aircraft with Mode S transponder State of registry must have assigned the aircraft a unique Mode S address code.

c) To operate in transponder mandatory controlled airspace with inoperative transponder you must have a clearance from the ATC to entry with inoperative transponder (negative transponder)

d) In the event of any failure or partial failure of the transponder equipment in transponder mandatory airspace you must immediately advise the ATC 

e) Unless otherwise required by ATC, only 1 of the aircraft in a
formation flight is required to operate a transponder in accordance with
paragraph (a).

Table 2.

Flight rules	Type of aircraft operation	SSR Code
VFR	For aircraft involved in fire fighting and reconnaissance duties	0111
IFR VFR	All All – in Auckland Oceanic FIR only	2000 2000
VFR	All – when operating in the aerodrome traffic circuit at a controlled aerodrome	2200
VFR	Aeroplanes other than Defence aeroplanes	1200
VFR	Gliders or balloons	1300
VFR	Powered aircraft in designated general aviation areas	1400
VFR	Helicopters other then Defence helicopters	1500
VFR	Defence aeroplanes	6000
VFR	Defence helicopters	6500

(a) Except as provided in paragraph (e), a pilot-in-command of an
aircraft operating in transponder-mandatory airspace designated under Part
71 must, unless otherwise authorised or instructed by ATC:

(1) operate the transponder
(i) in Mode A and Mode C; or
(ii) in Mode S if the aircraft is equipped with Mode S
equipment and allocated a unique Mode S code referred
to in paragraph (b); and

(2) Except if paragraph (3) applies or if operating Mode S
equipment, set the transponder SSR code
(i) to the code assigned by ATC for the flight; or
(ii) if not assigned a code by ATC, in accordance with Table
2; and

(3) In the event of an in-flight emergency, loss of radio
communications, or an act of unlawful interference, set the
transponder to the appropriate code in accordance with Table 3.

(b) A person must not operate an aircraft with Mode S transponder
equipment installed unless the State of registry has assigned the aircraft a
unique Mode S address code.

(c) A pilot-in-command of an aircraft intending to operate the aircraft
without an operable transponder in transponder mandatory airspace that is
within controlled airspace must obtain specific authorisation from the ATC
unit having jurisdiction over the relevant airspace as part of the ATC
clearance to enter that airspace.

(d) A pilot-in-command of an aircraft operating in transponder
mandatory airspace must immediately advise the ATC unit having
jurisdiction over the relevant airspace of any failure or partial failure of the
transponder equipment.

(e) Unless otherwise required by ATC, only 1 of the aircraft in a
formation flight is required to operate a transponder in accordance with
paragraph (a).