Apparatus

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sensors Mode-S transponder

A4AF91

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N4004M · operated by ROBINSON HELICOPTER COMPANY

Hex
A4AF91
Octal
51127621
Decimal
10,792,849
Country
US
Tail
N4004M
No current signal · last broadcast 5h ago
Flights observed
51
Distinct callsigns
1
Country
US
Last broadcast
5h ago

Last known position

Most recent position reported by Mode-S A4AF91.

Country allocation

The ICAO 24-bit address A4AF91 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
N4004M - 51 2026-07-24

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-24 N4004M - Jul 24, 15:00 UTCJul 24, 15:10 UTC10m
2026-07-24 N4004M - Jul 24, 14:15 UTCJul 24, 14:30 UTC15m
2026-07-23 N4004M - Jul 23, 20:25 UTCJul 23, 21:30 UTC1h 5m
2026-07-22 N4004M ISM → ISM Jul 22, 18:00 UTCJul 22, 18:55 UTC55m
2026-07-20 N4004M - Jul 20, 14:50 UTCJul 20, 18:15 UTC3h 25m
2026-07-18 N4004M - Jul 18, 13:55 UTCJul 18, 14:45 UTC50m
2026-07-17 N4004M CLW → ISM Jul 17, 23:25 UTCJul 18, 00:04 UTC40m
2026-07-17 N4004M - Jul 17, 22:15 UTCJul 17, 22:55 UTC40m
2026-07-17 N4004M - Jul 17, 14:10 UTCJul 17, 15:00 UTC50m
2026-07-12 N4004M - Jul 12, 20:35 UTCJul 12, 20:50 UTC15m
2026-07-12 N4004M - Jul 12, 18:10 UTCJul 12, 19:05 UTC55m
2026-07-12 N4004M - Jul 12, 13:45 UTCJul 12, 14:40 UTC55m
2026-07-11 N4004M - Jul 11, 16:20 UTCJul 11, 17:00 UTC40m
2026-07-11 N4004M - Jul 11, 13:40 UTCJul 11, 14:25 UTC45m
2026-07-10 N4004M - Jul 10, 15:10 UTCJul 10, 15:25 UTC15m
2026-07-10 N4004M - Jul 10, 13:50 UTCJul 10, 14:05 UTC15m
2026-07-08 N4004M - Jul 8, 14:05 UTCJul 8, 14:25 UTC20m
2026-07-07 N4004M - Jul 7, 17:15 UTCJul 7, 17:35 UTC20m
2026-07-07 N4004M - Jul 7, 11:25 UTCJul 7, 12:05 UTC40m
2026-07-06 N4004M - Jul 6, 16:40 UTCJul 6, 18:30 UTC1h 50m
2026-07-06 N4004M - Jul 6, 14:10 UTCJul 6, 15:40 UTC1h 30m
2026-07-05 N4004M - Jul 5, 21:50 UTCJul 5, 22:40 UTC50m
2026-07-05 N4004M - Jul 5, 17:05 UTCJul 5, 17:15 UTC10m
2026-07-05 N4004M - Jul 5, 15:45 UTCJul 5, 16:00 UTC15m
2026-07-03 N4004M - Jul 3, 16:15 UTCJul 3, 16:55 UTC40m
2026-07-02 N4004M ISM → ISM Jul 2, 19:10 UTCJul 2, 19:45 UTC35m
2026-06-29 N4004M - Jun 29, 18:10 UTCJun 29, 18:44 UTC35m
2026-06-26 N4004M - Jun 26, 16:14 UTCJun 26, 17:04 UTC50m
2026-06-24 N4004M - Jun 24, 00:55 UTCJun 24, 01:44 UTC50m
2026-06-23 N4004M - Jun 23, 16:29 UTCJun 23, 16:50 UTC20m
2026-06-19 N4004M - Jun 19, 14:44 UTCJun 19, 18:09 UTC3h 25m
2026-06-17 N4004M - Jun 17, 18:00 UTCJun 17, 19:55 UTC1h 55m
2026-06-17 N4004M - Jun 17, 16:25 UTCJun 17, 16:40 UTC15m
2026-06-17 N4004M - Jun 17, 14:10 UTCJun 17, 14:20 UTC10m
2026-06-16 N4004M - Jun 16, 15:45 UTCJun 16, 16:30 UTC45m
2026-06-16 N4004M - Jun 16, 14:15 UTCJun 16, 14:25 UTC10m
2026-06-16 N4004M - Jun 16, 13:09 UTCJun 16, 13:19 UTC10m
2026-06-15 N4004M - Jun 15, 17:10 UTCJun 15, 17:45 UTC35m
2026-06-14 N4004M - Jun 14, 17:50 UTCJun 14, 18:15 UTC25m
2026-06-14 N4004M - Jun 14, 16:30 UTCJun 14, 16:45 UTC15m
2026-06-14 N4004M - Jun 14, 14:25 UTCJun 14, 14:40 UTC15m
2026-06-13 N4004M - Jun 13, 22:05 UTCJun 13, 23:00 UTC55m
2026-06-13 N4004M - Jun 13, 20:20 UTCJun 13, 20:40 UTC20m
2026-06-13 N4004M - Jun 13, 17:05 UTCJun 13, 17:35 UTC30m
2026-06-13 N4004M - Jun 13, 16:00 UTCJun 13, 16:20 UTC20m
2026-06-12 N4004M - Jun 12, 22:45 UTCJun 13, 00:20 UTC1h 35m
2026-06-08 N4004M - Jun 8, 20:55 UTCJun 8, 21:10 UTC15m
2026-05-14 N4004M SPQ → TOA May 14, 15:35 UTCMay 14, 16:00 UTC25m
2026-05-11 N4004M TOA → TOA May 11, 21:30 UTCMay 11, 22:00 UTC30m
2026-05-11 N4004M TOA → TOA May 11, 20:10 UTCMay 11, 20:45 UTC35m

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 N4004M page for operator, model, and routing details .

Mode-S A4AF91 frequently asked

What is Mode-S code A4AF91?
A4AF91 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N4004M.
Where is Mode-S A4AF91 registered?
Mode-S code A4AF91 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 A4AF91 broadcasting right now?
No active broadcast right now. Last signal was 5h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A4AF91, octal 51127621, decimal 10,792,849.
What flights does A4AF91 operate?
Mode-S A4AF91 has broadcast 1 distinct callsign, including N4004M.