The Aviation Phonetic Alphabet and Numbers

01The Phonetic Alphabet, A to Z

When a single letter has to go over the radio, you say a word instead, so B can't be heard as D or P. The UK uses the same ICAO spelling alphabet as the rest of the world. CAP 413 lists each word with a guide to how it should sound.

CAP 413 marks the stressed syllable of each word in bold. Two details catch people out: the official spelling is Juliett, with two t's (you'll often see Juliet), and Quebec is said "KEH BECK". A few abbreviations that are part of everyday aviation language, such as QNH, QFE, ILS and RVR, are said as plain letters rather than spelt out phonetically.

02Numbers 0 to 9

Several digits have their own radio pronunciation, so they survive a weak signal and listeners whose first language isn't English. The outlined ones are the ones that differ from normal speech.

• Niner is the standard pronunciation. A common explanation is that it stops a nine being confused with a five.
• Tree drops the "th", a sound many speakers find hard and which is easily lost in static.
• Fower is two syllables, "FOE-wer", so it can't be heard as "for".
• Fife ends in a hard f, so it can't be mistaken for nine.
• Zero, never "oh". The point in a number is decimal (CAP 413 spells it DAYSEEMAL), and the two multipliers are hundred and thousand (TOUSAND).

In real UK flying you'll hear plenty of plain "three" and "five", but niner is almost universal. In your FRTOL practical test, the CAP 413 forms are never wrong.

03Callsigns and Abbreviated Callsigns

A UK registration is said letter by letter. G-JJER (a made-up registration) is "Golf Juliett Juliett Echo Romeo". The hyphen isn't spoken.

On first contact you use the full callsign of both stations. Once two-way contact is working, the ground station may shorten your callsign. For a registration, the short form is the first character and at least the last two, so G-JJER becomes "Golf Echo Romeo".

In the UK you may put the aircraft manufacturer, model or category in front of the callsign, for example "Piper Golf Echo Romeo" or "Helicopter Golf Echo Romeo". Solo students put "Student" before the callsign on first contact with each air traffic unit, and in any Mayday or Pan call. The initial call guide shows where the callsign goes in each call.

04Said Digit by Digit

The default rule is simple: every digit is spoken separately. That covers callsigns, pressure settings, flight levels, headings, wind direction and speed, airspeeds and frequencies.

• Pressure settings. QNH 1013 is "one zero one tree", never "ten thirteen". Below 1000 hPa, add "hectopascals", and include the units in your read-back too. Altimeter settings are on the read-back list. See what to read back.
• Headings are always three digits. Add "degrees" when the heading ends in zero, and never use "hundred" for a heading: 100° is "one zero zero degrees".
• Flight levels are digit by digit, except whole hundreds. The UK says FL100 as "flight level one hundred" rather than ICAO's "one zero zero", to avoid confusion with adjacent levels: "one zero zero" can be misheard as "one one zero". Don't put "to" in front of a flight level: "climb flight level six five".

05When to Say "Hundred" and "Thousand"

Altitudes, heights, cloud heights, visibility and runway visual range in whole hundreds or whole thousands use the words hundred and thousand. Pressure settings and squawks use them only for whole thousands (QNH 1000, squawk 7000).

Altitude, height or flight level. Which word you use depends on the altimeter setting. On the regional or aerodrome QNH you report an altitude (above mean sea level). On QFE you report a height (above the aerodrome). On the standard setting of 1013 hPa you report a flight level. When climbing or descending to an altitude or height, the instruction uses "to" before the word altitude or height, and the first message includes the pressure setting: "descend to altitude two thousand feet, QNH one zero one tree".

Squawks. 7000, the UK VFR conspicuity code, is "seven thousand". The emergency code 7700 isn't a whole thousand, so it's "seven seven zero zero". Practise switching between the two in the CAP 413 number trainer on our homepage.

06Frequencies, Including 8.33 kHz

Frequencies are said digit by digit, with "decimal" for the point. In the UK, all six figures are spoken whether the frequency uses 25 kHz or 8.33 kHz spacing.

• The only shortcut: if the last two figures are both zero, you can stop after the first four. So 129.700 is "one two niner decimal seven", but 121.025 needs all six.
• An 8.33 kHz frequency is technically a "channel", but the word "channel" isn't used on the radio. Just say the six figures.
• If a controller asks "confirm eight point three three", they want to know whether your radio can tune 8.33 kHz frequencies. Answer "affirm eight point three three" or "negative eight point three three".
• Frequency changes must be read back. "Gloster Tower one two two decimal niner, Golf Echo Romeo" is a typical reply.

07Time, Wind, Distance and Visibility

• Time is always UTC, and normally just the minutes. Add the hour if there's any chance of confusion.
• Wind is direction in degrees then speed in knots, each digit separately.
• Visibility in whole hundreds or thousands of metres uses hundred and thousand. In kilometres, the digits are said one by one.

08Cheat Sheet

One page to keep in your kneeboard or by your desk. Print this page and only this section comes out.

09Frequently Asked Questions

Next, learn the standard words that go around these numbers in our CAP 413 phraseology guide, and the radio theory in the FRTOL written exam guide.