Apparatus

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sensors Mode-S transponder

C81C31

ICAO 24-bit transponder address · allocated to New Zealand

Currently assigned to ZK-SDF · PACIFIC AEROSPACE P-750 XStol

Hex
C81C31
Octal
62016061
Decimal
13,114,417
Country
NZ
Tail
ZK-SDF
Type
P750
No current signal · last broadcast 1h ago
Flights observed
23
Distinct callsigns
1
Country
NZ
Last broadcast
1h ago

Last known position

Most recent position reported by Mode-S C81C31.

Country allocation

The ICAO 24-bit address C81C31 falls within the block assigned to New Zealand (NZ) by ICAO Annex 10, Volume III. Every aircraft registered in New Zealand receives a permanent address from this block at the time of registration; the address stays with the airframe even if the aircraft is re-registered to a different operator within the country.

Callsign history 1 distinct

Callsign Airline Flights Last seen
ZKSDF - 23 2026-04-25

Recent flights last 23

DateFlightRouteTakeoffLandingDuration
2026-04-25 ZKSDF - Apr 25, 01:55 UTCApr 25, 02:50 UTC55m
2026-04-24 ZKSDF - Apr 24, 21:30 UTCApr 25, 01:10 UTC3h 40m
2026-04-23 ZKSDF - Apr 23, 03:00 UTCApr 23, 03:20 UTC20m
2026-04-23 ZKSDF - Apr 23, 01:15 UTCApr 23, 02:20 UTC1h 5m
2026-04-23 ZKSDF - Apr 23, 00:15 UTCApr 23, 00:40 UTC25m
2026-04-22 ZKSDF - Apr 22, 22:40 UTCApr 22, 23:30 UTC50m
2026-04-22 ZKSDF - Apr 22, 21:30 UTCApr 22, 21:50 UTC20m
2026-04-22 ZKSDF - Apr 22, 02:15 UTCApr 22, 02:35 UTC20m
2026-04-21 ZKSDF - Apr 21, 22:35 UTCApr 22, 01:35 UTC3h 0m
2026-04-21 ZKSDF - Apr 21, 02:15 UTCApr 21, 02:35 UTC20m
2026-04-21 ZKSDF - Apr 21, 01:00 UTCApr 21, 01:20 UTC20m
2026-04-20 ZKSDF - Apr 20, 21:40 UTCApr 21, 00:05 UTC2h 25m
2026-04-20 ZKSDF - Apr 20, 00:20 UTCApr 20, 00:35 UTC15m
2026-04-19 ZKSDF - Apr 19, 21:20 UTCApr 19, 23:40 UTC2h 20m
2026-04-18 ZKSDF - Apr 18, 22:25 UTCApr 19, 01:35 UTC3h 10m
2026-04-17 ZKSDF - Apr 17, 23:25 UTCApr 17, 23:45 UTC20m
2026-04-17 ZKSDF - Apr 17, 22:10 UTCApr 17, 23:05 UTC55m
2026-04-17 ZKSDF - Apr 17, 02:30 UTCApr 17, 02:50 UTC20m
2026-04-17 ZKSDF - Apr 17, 01:25 UTCApr 17, 01:50 UTC25m
2026-04-16 ZKSDF - Apr 16, 23:35 UTCApr 17, 01:10 UTC1h 35m
2026-04-16 ZKSDF - Apr 16, 22:20 UTCApr 16, 23:10 UTC50m
2026-04-16 ZKSDF - Apr 16, 21:30 UTCApr 16, 21:50 UTC20m
2026-04-13 ZKSDF - Apr 13, 21:50 UTCApr 13, 22:45 UTC55m

About Mode-S

A Mode-S transponder code (also called an "ICAO 24-bit address" or "hex code") is a 6-character hexadecimal identifier permanently assigned to an aircraft when it's first registered. Unlike callsigns (which change with each flight) or registrations (which can change if an aircraft is sold internationally), the Mode-S address stays with the airframe for the life of the aircraft in that country.

Every ADS-B transmission from an aircraft includes its Mode-S address, making it the most reliable way to identify a specific airframe. Flight-tracking services like Apparatus use the Mode-S address as the primary key for tying position broadcasts, callsigns, and ownership records together.

Prefer a tail-number view? See the ZK-SDF page for operator, model, and routing details .

Mode-S C81C31 frequently asked

What is Mode-S code C81C31?
C81C31 is an ICAO 24-bit transponder address. Allocated to New Zealand. Assigned to ZK-SDF.
Where is Mode-S C81C31 registered?
Mode-S code C81C31 is allocated to New Zealand (NZ). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is C81C31 broadcasting right now?
No active broadcast right now. Last signal was 1h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex C81C31, octal 62016061, decimal 13,114,417.
What flights does C81C31 operate?
Mode-S C81C31 has broadcast 1 distinct callsign, including ZKSDF.