Apparatus

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sensors Mode-S transponder

A691F0

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N522SD · operated by SOUTH DAKOTA STATE UNIVERSITY

Hex
A691F0
Octal
51510760
Decimal
10,916,336
Country
US
Tail
N522SD
Type
C172
No current signal · last broadcast Jul 22, 21:15 UTC
Flights observed
300
Distinct callsigns
1
Country
US
Last broadcast
Jul 22, 21:15 UTC

Last known position

Most recent position reported by Mode-S A691F0.

Country allocation

The ICAO 24-bit address A691F0 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
N522SD - 300 2026-07-22

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-22 N522SD BKX → BKX Jul 22, 20:00 UTCJul 22, 21:10 UTC1h 10m
2026-07-22 N522SD BKX → BKX Jul 22, 14:35 UTCJul 22, 15:30 UTC55m
2026-07-21 N522SD BKX → BKX Jul 21, 00:15 UTCJul 21, 01:10 UTC55m
2026-07-20 N522SD BKX → BKX Jul 20, 21:25 UTCJul 20, 22:05 UTC40m
2026-07-20 N522SD BKX → BKX Jul 20, 16:35 UTCJul 20, 17:25 UTC50m
2026-07-20 N522SD - Jul 20, 14:55 UTCJul 20, 15:05 UTC10m
2026-07-20 N522SD - Jul 20, 13:40 UTCJul 20, 13:50 UTC10m
2026-07-20 N522SD BKX → BKX Jul 20, 00:15 UTCJul 20, 00:20 UTC5m
2026-07-19 N522SD BKX → BKX Jul 19, 22:25 UTCJul 20, 00:10 UTC1h 45m
2026-07-19 N522SD BKX → BKX Jul 19, 19:50 UTCJul 19, 19:55 UTC5m
2026-07-19 N522SD BKX → BKX Jul 19, 18:50 UTCJul 19, 19:45 UTC55m
2026-07-16 N522SD BKX → BKX Jul 16, 23:35 UTCJul 17, 00:45 UTC1h 10m
2026-07-16 N522SD BKX → BKX Jul 16, 21:45 UTCJul 16, 22:45 UTC1h 0m
2026-07-16 N522SD - Jul 16, 17:20 UTCJul 16, 17:40 UTC20m
2026-07-16 N522SD - Jul 16, 16:05 UTCJul 16, 16:15 UTC10m
2026-07-16 N522SD - Jul 16, 15:05 UTCJul 16, 15:14 UTC10m
2026-07-16 N522SD - Jul 16, 04:05 UTCJul 16, 04:10 UTC5m
2026-07-16 N522SD - Jul 16, 02:50 UTCJul 16, 03:00 UTC10m
2026-07-16 N522SD BKX → BKX Jul 16, 00:55 UTCJul 16, 01:45 UTC50m
2026-07-15 N522SD BKX → BKX Jul 15, 22:45 UTCJul 16, 00:15 UTC1h 30m
2026-07-15 N522SD BKX → BKX Jul 15, 19:30 UTCJul 15, 20:30 UTC1h 0m
2026-07-15 N522SD BKX → BKX Jul 15, 13:40 UTCJul 15, 14:50 UTC1h 10m
2026-07-14 N522SD BKX → BKX Jul 14, 17:50 UTCJul 14, 18:50 UTC1h 0m
2026-07-14 N522SD BKX → BKX Jul 14, 15:20 UTCJul 14, 16:40 UTC1h 20m
2026-07-13 N522SD - Jul 13, 20:40 UTCJul 13, 22:00 UTC1h 20m
2026-07-13 N522SD - Jul 13, 20:25 UTCJul 13, 20:35 UTC10m
2026-07-13 N522SD BKX → BKX Jul 13, 15:20 UTCJul 13, 16:15 UTC55m
2026-07-11 N522SD BKX → BKX Jul 11, 17:15 UTCJul 11, 17:25 UTC10m
2026-07-11 N522SD BKX → BKX Jul 11, 16:50 UTCJul 11, 17:00 UTC10m
2026-07-11 N522SD - Jul 11, 16:30 UTCJul 11, 16:35 UTC5m
2026-07-11 N522SD BKX → BKX Jul 11, 16:00 UTCJul 11, 16:05 UTC5m
2026-07-11 N522SD BKX → BKX Jul 11, 15:30 UTCJul 11, 15:40 UTC10m
2026-07-11 N522SD - Jul 11, 15:05 UTCJul 11, 15:15 UTC10m
2026-07-11 N522SD BKX → BKX Jul 11, 14:35 UTCJul 11, 14:40 UTC5m
2026-07-11 N522SD - Jul 11, 14:05 UTCJul 11, 14:15 UTC10m
2026-07-11 N522SD BKX → BKX Jul 11, 13:35 UTCJul 11, 13:45 UTC10m
2026-07-10 N522SD BKX → BKX Jul 10, 00:05 UTCJul 10, 01:00 UTC55m
2026-07-09 N522SD - Jul 9, 22:55 UTCJul 9, 23:20 UTC25m
2026-07-09 N522SD - Jul 9, 22:00 UTCJul 9, 22:15 UTC15m
2026-07-09 N522SD BKX → BKX Jul 9, 18:55 UTCJul 9, 21:10 UTC2h 15m
2026-07-09 N522SD - Jul 9, 17:10 UTCJul 9, 17:25 UTC15m
2026-07-09 N522SD - Jul 9, 15:50 UTCJul 9, 16:25 UTC35m
2026-07-08 N522SD BKX → BKX Jul 8, 14:30 UTCJul 8, 15:35 UTC1h 5m
2026-07-08 N522SD BKX → BKX Jul 8, 00:35 UTCJul 8, 01:25 UTC50m
2026-07-07 N522SD BKX → BKX Jul 7, 21:05 UTCJul 7, 22:20 UTC1h 15m
2026-07-07 N522SD BKX → BKX Jul 7, 19:10 UTCJul 7, 20:15 UTC1h 5m
2026-07-07 N522SD BKX → BKX Jul 7, 15:45 UTCJul 7, 17:05 UTC1h 20m
2026-07-07 N522SD BKX → BKX Jul 7, 13:25 UTCJul 7, 14:35 UTC1h 10m
2026-07-06 N522SD BKX → BKX Jul 6, 20:30 UTCJul 6, 22:05 UTC1h 35m
2026-07-06 N522SD BKX → BKX Jul 6, 19:30 UTCJul 6, 19:35 UTC5m

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 N522SD page for operator, model, and routing details .

Mode-S A691F0 frequently asked

What is Mode-S code A691F0?
A691F0 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N522SD.
Where is Mode-S A691F0 registered?
Mode-S code A691F0 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 A691F0 broadcasting right now?
No active broadcast right now. Last signal was Jul 22, 21:15 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex A691F0, octal 51510760, decimal 10,916,336.
What flights does A691F0 operate?
Mode-S A691F0 has broadcast 1 distinct callsign, including N522SD.