Apparatus

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sensors Mode-S transponder

4A2183

ICAO 24-bit transponder address · allocated to Romania

Currently assigned to YR-HLC · BOEING 737-800

Hex
4A2183
Octal
22420603
Decimal
4,858,243
Country
RO
Tail
YR-HLC
Type
B738
No current signal · last broadcast 13h ago
Flights observed
9
Distinct callsigns
2
Country
RO
Last broadcast
13h ago

Last known position

Most recent position reported by Mode-S 4A2183.

Country allocation

The ICAO 24-bit address 4A2183 falls within the block assigned to Romania (RO) by ICAO Annex 10, Volume III. Every aircraft registered in Romania 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 2 distinct

Callsign Airline Flights Last seen
HLJ2EY - 6 2026-04-14
HLJ2VV - 3 2026-04-13

Recent flights last 9

DateFlightRouteTakeoffLandingDuration
2026-04-14 HLJ2EY - Apr 14, 09:10 UTCApr 14, 10:10 UTC1h 0m
2026-04-14 HLJ2EY - Apr 14, 07:10 UTCApr 14, 09:05 UTC1h 55m
2026-04-14 HLJ2EY - Apr 14, 06:45 UTCApr 14, 07:10 UTC25m
2026-04-13 HLJ2VV - Apr 13, 16:15 UTCApr 13, 16:40 UTC25m
2026-04-13 HLJ2VV - Apr 13, 15:50 UTCApr 13, 16:40 UTC50m
2026-04-13 HLJ2VV - Apr 13, 13:20 UTCApr 13, 16:15 UTC2h 55m
2026-04-13 HLJ2EY - Apr 13, 08:20 UTCApr 13, 08:35 UTC15m
2026-04-13 HLJ2EY - Apr 13, 07:55 UTCApr 13, 08:35 UTC40m
2026-04-13 HLJ2EY - Apr 13, 05:10 UTCApr 13, 08:15 UTC3h 5m

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 YR-HLC page for operator, model, and routing details .

Mode-S 4A2183 frequently asked

What is Mode-S code 4A2183?
4A2183 is an ICAO 24-bit transponder address. Allocated to Romania. Assigned to YR-HLC.
Where is Mode-S 4A2183 registered?
Mode-S code 4A2183 is allocated to Romania (RO). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is 4A2183 broadcasting right now?
No active broadcast right now. Last signal was 13h ago.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex 4A2183, octal 22420603, decimal 4,858,243.
What flights does 4A2183 operate?
Mode-S 4A2183 has broadcast 2 distinct callsigns, including HLJ2EY, HLJ2VV.