Readback

What is readback

The readback is the exact repetition by the pilot of ATC instructions received. It's a two-way verification:

1. The controller has confirmation you received correctly.
2. The controller can correct you immediately if you misunderstood.
3. You have an active reminder of values to set.

Without readback, an ATC clearance isn't considered "closed". If you misread a readback (e.g. repeat "QNH 1008" when the controller said "1018") and the controller doesn't catch the error, legally what you repeated is what counts. That's why it's also called "hearback": the controller must listen to your readback and correct if needed.

What must always be repeated (mandatory)

ICAO Annex 10 lists instructions that mandatorily require readback. They're all direct operational instructions:

• ATC clearance (clearances for IFR and special VFR)
• Taxi instructions (taxi instructions, holding points)
• Runway authorizations (cleared for take-off, cleared to land, line up and wait)
• Altimeter settings (QNH and Standard)
• Altitudes, flight levels, headings, speeds assigned
• Transponder squawk codes
• Frequency changes assigned
• Approach type assigned
• Runway in use
• Restrictions (e.g. "report passing 3000 feet")

What does NOT need to be repeated

Some things don't require readback, and repeating them only wastes radio time:

• Weather information ("Wind 220 degrees 5 knots") — just acknowledgement
• Traffic information ("Traffic 12 o'clock 3 miles") — "Traffic in sight" or "Looking out"
• NOTAM or informational messages
• Action confirmation ("Confirm you copied?") — just "Affirm" or "Negative"

Correct readback structure

Readback has three golden rules:

1. Same order

Repeat elements in the same order the controller said them. Don't reorganize, don't summarize.

2. End with your callsign

The callsign always closes the readback. It tells the controller who confirmed.

3. Literal, not paraphrased

Quantities are said with the same words. If the controller says "climb to flight level one two zero", you repeat "climb to flight level one two zero" — not "FL120" or "climbing twelve thousand".

What happens if you mess up the readback

The controller must correct you immediately. Standard phraseology:

"NEGATIVE, [callsign], I say again..." followed by the correct instruction. You then make a new correct readback.

If you notice the error yourself (you realize a second after releasing PTT), correct immediately:

"Correction, HB-PMR, descend 4000 feet QNH 1018."

Readback and controller corrections

When the controller corrects you, your new readback must include the explicit correction:

Readback in different languages

Readback is done in the same language as the instruction. If the controller speaks Italian, you reply in Italian. If they speak English, reply in English. Mixing languages is incorrect and creates ambiguity.

In Switzerland Skyguide adapts to the pilot: if you feel safer in English, start in English. If you start in Italian, continue in Italian. Linguistic consistency is almost as important as phraseology.

Summary — to remember

1. Readback = operational confirmation, not politeness.
2. Mandatory for clearances, taxi, take-off/landing, QNH, altitudes, headings, speeds, squawk, frequencies.
3. Not mandatory for weather, traffic, NOTAM, general info.
4. Same order, literal, callsign at the end.
5. "Roger" isn't enough for operational instructions.
6. Consistent language throughout the conversation.

Sources

• ICAO Annex 10 — Aeronautical Telecommunications, Volume II, Chapter 5
• ICAO Doc 9432 — Manual of Radiotelephony, Chapter 4
• ICAO Doc 4444 — PANS-ATM, Chapter 12 (Phraseologies)
• Aero Locarno · Subject 090 — VFR Communications (EASA syllabus)