Apparatus

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sensors Mode-S transponder

D51DDB

ICAO 24-bit transponder address

Hex
D51DDB
Octal
65216733
Decimal
13,966,811
No current signal · last broadcast 3d ago
Flights observed
3
Distinct callsigns
0
Country
-
Last broadcast
3d ago

Last known position

Most recent position reported by Mode-S D51DDB.

Recent flights last 3

DateFlightRouteTakeoffLandingDuration
2026-05-26 - LDJ → LDJ May 26, 19:30 UTCMay 26, 20:09 UTC40m
2026-05-26 - LDJ → LDJ May 26, 18:55 UTCMay 26, 19:25 UTC30m
2026-05-26 - - May 26, 18:40 UTCMay 26, 18:50 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.

Mode-S D51DDB frequently asked

What is Mode-S code D51DDB?
D51DDB is an ICAO 24-bit transponder address.
Is D51DDB broadcasting right now?
No active broadcast right now. Last signal was 3d ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex D51DDB, octal 65216733, decimal 13,966,811.