IDENT
IDENT is a special function on the transponder that briefly highlights the aircraft on radar to simplify identification for ATC.
Source: ICAO Annex 10 Volume IV; EUROCONTROL Specifications.
How it works
When the pilot presses the IDENT button:
- Transponder sends a special signal in addition to the normal squawk code.
- ATC sees the aircraft flash on the radar (typically illuminated green) for 15-20 seconds.
- Confirms unambiguously the identification of the aircraft.
When to use?
On ATC request
Standard phraseology:
- ATC: "DEMRA, squawk ident."
- Pilot: presses IDENT button.
- ATC: "DEMRA, identified" or "DEMRA, radar contact".
Pilot-initiated
Not without prompt — avoid loading radar unnecessarily:
- Only when pilot believes ATC has wrong identification.
- "DEMRA, identifying" → pilot presses IDENT.
What IDENT does NOT do
- No transmission is made.
- No altitude info is changed.
- No other data is modified.
- Just a brief highlight on the radar.
IDENT in specific procedures
First radar pickup
ATC takes a new traffic into radar:
- ATC: "DEMRA, squawk ident for radar identification."
- Pilot presses IDENT.
- ATC confirms: "Radar contact, position 5 NM north of Munich."
Loss of radar contact
On temporary loss:
- ATC: "DEMRA, radar contact lost, squawk ident."
- Pilot presses IDENT.
- ATC: "Radar contact" (re-acquired).
Verification in conflict situation
With two aircraft of similar callsign:
- ATC: "DEMRA, squawk ident to confirm identity."
- Pilot presses IDENT.
Cockpit operation
IDENT button location
Various designs:
- Large red button on the transponder.
- Press for ~1 second.
- Light illuminates briefly during transmission.
Touchscreen / glass cockpit
Multi-function display:
- IDENT as soft key or menu entry.
- Pressing activates the function.
Common errors
- IDENT multiple times in quick succession: ATC sees repeated flashes — unprofessional.
- IDENT without prompt: pilot signals "help or confirmation needed" → can confuse ATC.
- IDENT instead of squawk-code change: IDENT does not change codes, only highlights.
IDENT vs. squawk
Confusion possible:
- Squawk [code]: pilot sets a specific code.
- Squawk ident: pilot presses the IDENT button.
ATC distinguishes clearly:
- "Squawk 4221" = code change.
- "Squawk ident" = press IDENT button.
- "Squawk standby" = transponder to STBY.
Special case: VFR flight without ATC service
In uncontrolled airspace without ATC service:
- IDENT button has no direct effect (no radar in reception range).
- However: traffic with ADS-B In sees the aircraft entry via IDENT in their traffic display (modern, rare in PPL trainers).
Cross-reference
- Subject 090 Lesson "Modes": transponder theory.
- Subject 090 Lesson "Standard codes": squawk codes.