Communications

Definitions & Abbreviations

Aeronautical Mobile Service: A mobile radio service between aeronautical (ground) stations and aircraft stations, or between aircraft stations.

Transmission of Letters — ICAO Phonetic Alphabet

A Alpha, B Bravo, C Charlie, D Delta, E Echo, F Foxtrot, G Golf, H Hotel, I India, J Juliett, K Kilo, L Lima, M Mike, N November, O Oscar, P Papa, Q Quebec, R Romeo, S Sierra, T Tango, U Uniform, V Victor, W Whiskey, X X-ray, Y Yankee, Z Zulu.

Transmission of Numbers

Numbers are normally transmitted digit by digit. Pronunciation: ZE-RO, WUN, TOO, TREE, FOW-er, FIFE, SIX, SEV-en, AIT, NIN-er. Decimal point = "DECIMAL"; thousand = "TOU-SAND".

VHF Frequencies & Channel Spacing

Standard channel spacing is 25 kHz; in busy airspace it is reduced to 8.33 kHz (one third of 25 kHz), creating more channels.

25 kHz channels need 5 digits; 8.33 kHz channels need 6 digits.

ICAO standard: pass all 6 digits of a VHF frequency regardless of spacing — except where the final two digits are both zero, when only the first four need be transmitted.

Categories of Messages (priority order)

1. Distress (MAYDAY) — highest priority.

2. Urgency (PAN PAN).

3. Direction-finding messages.

4. Flight-safety messages.

5. Meteorological messages.

6. Flight-regularity messages — lowest priority.

Distress (MAYDAY): A condition of being threatened by serious and/or imminent danger and requiring immediate assistance.

Urgency (PAN PAN): A condition concerning the safety of an aircraft or person but not requiring immediate assistance.

Abbreviations: Some abbreviations understood by common use need not be spelled out, e.g. ILS, VOR, NDB, TACAN, GPS, SELCAL, and the Q-codes (QFE, QNH, QDM).