Apparatus

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sensors Mode-S transponder

A4AD54

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N400HD · ROBINSON R-44 Raven · operated by SPITZER HELICOPTER LLC

Hex
A4AD54
Octal
51126524
Decimal
10,792,276
Country
US
Tail
N400HD
Type
R44
No current signal · last broadcast 1h ago
Flights observed
163
Distinct callsigns
1
Country
US
Last broadcast
1h ago

Last known position

Most recent position reported by Mode-S A4AD54.

Country allocation

The ICAO 24-bit address A4AD54 falls within the block assigned to United States (US) by ICAO Annex 10, Volume III. Every aircraft registered in United States 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
N400HD - 163 2026-07-15

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-15 N400HD - Jul 15, 00:40 UTCJul 15, 01:50 UTC1h 10m
2026-07-14 N400HD - Jul 14, 23:45 UTCJul 14, 23:55 UTC10m
2026-07-14 N400HD - Jul 14, 19:25 UTCJul 14, 20:00 UTC35m
2026-07-14 N400HD - Jul 14, 17:20 UTCJul 14, 17:50 UTC30m
2026-07-14 N400HD - Jul 14, 01:30 UTCJul 14, 01:45 UTC15m
2026-07-13 N400HD - Jul 13, 01:01 UTCJul 13, 01:10 UTC10m
2026-07-13 N400HD - Jul 13, 00:15 UTCJul 13, 00:25 UTC10m
2026-07-12 N400HD - Jul 12, 22:45 UTCJul 12, 23:00 UTC15m
2026-07-12 N400HD - Jul 12, 19:55 UTCJul 12, 20:15 UTC20m
2026-07-12 N400HD - Jul 12, 17:10 UTCJul 12, 17:20 UTC10m
2026-07-12 N400HD - Jul 12, 01:50 UTCJul 12, 02:25 UTC35m
2026-07-12 N400HD - Jul 12, 00:05 UTCJul 12, 01:05 UTC1h 0m
2026-07-11 N400HD - Jul 11, 21:55 UTCJul 11, 22:10 UTC15m
2026-07-11 N400HD - Jul 11, 20:10 UTCJul 11, 20:30 UTC20m
2026-07-11 N400HD - Jul 11, 19:10 UTCJul 11, 19:25 UTC15m
2026-07-11 N400HD - Jul 11, 16:55 UTCJul 11, 18:10 UTC1h 15m
2026-07-11 N400HD - Jul 11, 00:35 UTCJul 11, 02:35 UTC2h 0m
2026-07-10 N400HD - Jul 10, 18:35 UTCJul 10, 19:05 UTC30m
2026-07-10 N400HD - Jul 10, 00:45 UTCJul 10, 01:25 UTC40m
2026-07-10 N400HD - Jul 10, 00:00 UTCJul 10, 00:10 UTC10m
2026-07-09 N400HD - Jul 9, 20:35 UTCJul 9, 21:10 UTC35m
2026-07-09 N400HD - Jul 9, 15:55 UTCJul 9, 16:05 UTC10m
2026-07-08 N400HD - Jul 8, 16:45 UTCJul 8, 16:55 UTC10m
2026-07-08 N400HD - Jul 8, 15:35 UTCJul 8, 15:45 UTC10m
2026-07-08 N400HD - Jul 8, 01:15 UTCJul 8, 01:25 UTC10m
2026-07-07 N400HD - Jul 7, 19:15 UTCJul 7, 19:25 UTC10m
2026-07-07 N400HD - Jul 7, 00:45 UTCJul 7, 01:15 UTC30m
2026-07-05 N400HD - Jul 5, 02:05 UTCJul 5, 03:00 UTC55m
2026-07-04 N400HD - Jul 4, 18:05 UTCJul 4, 18:30 UTC25m
2026-07-02 N400HD - Jul 2, 02:00 UTCJul 2, 02:10 UTC10m
2026-07-01 N400HD - Jul 1, 23:05 UTCJul 1, 23:40 UTC35m
2026-06-22 N400HD - Jun 22, 00:24 UTCJun 22, 01:49 UTC1h 25m
2026-06-21 N400HD - Jun 21, 22:44 UTCJun 21, 22:54 UTC10m
2026-06-21 N400HD - Jun 21, 21:39 UTCJun 21, 21:49 UTC10m
2026-06-21 N400HD - Jun 21, 19:00 UTCJun 21, 20:40 UTC1h 40m
2026-06-21 N400HD - Jun 21, 00:19 UTCJun 21, 03:05 UTC2h 45m
2026-06-20 N400HD - Jun 20, 18:19 UTCJun 20, 18:49 UTC30m
2026-06-20 N400HD - Jun 20, 15:39 UTCJun 20, 16:59 UTC1h 20m
2026-06-20 N400HD - Jun 20, 00:09 UTCJun 20, 02:54 UTC2h 45m
2026-06-19 N400HD - Jun 19, 02:19 UTCJun 19, 02:29 UTC10m
2026-06-18 N400HD - Jun 18, 18:20 UTCJun 18, 18:30 UTC10m
2026-06-18 N400HD - Jun 18, 15:05 UTCJun 18, 16:15 UTC1h 10m
2026-06-18 N400HD - Jun 18, 02:25 UTCJun 18, 02:35 UTC10m
2026-06-18 N400HD - Jun 18, 01:10 UTCJun 18, 01:25 UTC15m
2026-06-17 N400HD - Jun 17, 22:15 UTCJun 18, 00:00 UTC1h 45m
2026-06-17 N400HD - Jun 17, 18:35 UTCJun 17, 18:45 UTC10m
2026-06-17 N400HD - Jun 17, 15:10 UTCJun 17, 15:30 UTC20m
2026-06-15 N400HD - Jun 15, 01:50 UTCJun 15, 02:10 UTC20m
2026-06-15 N400HD - Jun 15, 00:10 UTCJun 15, 01:15 UTC1h 5m
2026-06-14 N400HD - Jun 14, 23:29 UTCJun 14, 23:39 UTC10m

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 N400HD page for operator, model, and routing details .

Mode-S A4AD54 frequently asked

What is Mode-S code A4AD54?
A4AD54 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N400HD.
Where is Mode-S A4AD54 registered?
Mode-S code A4AD54 is allocated to United States (US). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is A4AD54 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 A4AD54, octal 51126524, decimal 10,792,276.
What flights does A4AD54 operate?
Mode-S A4AD54 has broadcast 1 distinct callsign, including N400HD.