Standard radiotelephony (RT) phraseology exists so messages are understood first time, even with poor signal, accents or high workload. UK RT follows CAP 413. Say exact words in the right order - do not paraphrase.
Certain items must always be read back in full: runway-in-use instructions, level (altitude/height/flight level) instructions, heading instructions, altimeter settings (QNH/QFE), transponder codes, airways/route clearances, and any instruction to hold, cross, enter, backtrack, or line up on a runway.
At an uncontrolled (unattended or A/G) aerodrome you are talking to a Flight Information Service Officer (FISO) or an AFIS operator who gives information, not instructions - or nobody at all if it is a pure air-ground radio. At a controlled aerodrome the tower issues instructions you must comply with. Knowing which service you have changes both your phraseology and your legal obligations.
A typical VFR circuit sequence at a UK aerodrome runs:
The classic UK join is via the overhead: cross at a safe height (commonly 2,000 ft above aerodrome level, but always check the height given), descend on the dead side, and join crosswind or downwind having identified the circuit direction and runway in use from the wind indicator or ATIS/AFIS information.
Circuit height is aerodrome-specific - commonly 1,000 ft QFE for light singles - but you must use the published or broadcast figure, not a memorised default. Circuit direction (left-hand or right-hand) is also aerodrome-specific and must be confirmed; flying the wrong-hand circuit is a classic exam trap and a real-world hazard.
An ATC clearance authorises you to proceed within specific conditions - it is not an instruction that overrides the rules of the air, and it does not guarantee separation from terrain or obstacles (you still fly the aircraft safely). A clearance can be for taxi, take-off, route, level, or approach.
UK CAA (via CAP 413) requires full readback of the safety-critical items:
Partial readback with your own callsign is fine for non-critical items (e.g. frequency changes), but the items above must always be read back in full, using your full callsign, and in the same order ATC gave them.
Readback lets the controller catch a mishear before it becomes a mistake. If you read back a clearance incorrectly, ATC MUST correct you immediately - silence after a readback does not mean agreement, but a controller not intervening after a correct readback does confirm it.
If ATC issues a clearance 'to hold short of' or 'not above' a level, that condition is binding until amended. If you cannot comply (weather, performance), you must say so immediately rather than accept and hope.
Use 'say again' to have the whole or part of a transmission repeated, or 'confirm' to check your understanding of a specific item. Never guess a clearance - an incorrect assumption is a major cause of airspace infringements and runway incursions.
Always: callsign first or last (UK convention favours callsign at the end of the readback, though beginning is also acceptable and commonly taught), clearance details read back in the order given, using standard phraseology and numbers pronounced individually (e.g. 'two five zero zero' for 2500).
Radio (COM) failure means you can no longer transmit and/or receive on the frequency in use. It is different from a full electrical failure, though the same drill often applies if you cannot isolate the fault. Always suspect the simple things first: wrong frequency selected, volume too low, headset unplugged, squelch set wrong, or a stuck transmit button on someone else's aircraft blocking the frequency.
If VMC, the standard advice is to remain in VMC, continue on your flight plan and land at the nearest suitable aerodrome, then telephone ATC as soon as possible after landing. If you are in a control zone, leave it by the most direct route if this can be done without prejudicing safety.
Watch for a light signal from the visual control room - a steady green means cleared to land, a steady red means give way and continue circling, flashing red means the aerodrome is unsafe, land elsewhere. Fly a standard overhead join or conform to the visual circuit pattern already in use, watching carefully for other traffic and for signals square (a marker showing right-hand circuits in force).
Squawk 7600 and follow the last ATC clearance received - level, heading and route. If holding, expect further clearance at the last acknowledged time, or leave the hold at the expected approach time. Maintain the last assigned level, or the minimum safe altitude if higher, and proceed to the appropriate navigation aid or clearance limit for an approach, aiming to arrive as close as possible to your original ETA.
Distress means you're threatened by grave and imminent danger and need immediate help - engine failure, fire, structural damage. Urgency means you have a safety concern that isn't yet life-threatening - you're unsure of position, running low on fuel, or a passenger is ill. The two calls use different key words and different priorities, and mixing them up is a common exam trap.
Say the word MAYDAY three times to open the transmission - this is what separates it from routine RT and grabs everyone's attention on frequency. The structure to remember is MAYDAY DDD: Mayday x3, station addressed, aircraft callsign, then nature of emergency, intentions, present position, heading, altitude, and souls on board (often remembered as the mnemonic 'Mayday Mayday Mayday, [station], [callsign], Nature, Intention, Position, Level/Heading, Souls, other useful info'). Keep it as short and clear as possible - controllers need the key facts fast, not a long story.
Say PAN PAN three times (pronounced 'pan pan', from the French panne, meaning breakdown). The message content follows the same broad shape as a Mayday - identification, nature of the problem, intentions and position - but the urgency is one notch below distress. A PAN call still gets priority handling from ATC over normal traffic.
Transmit on the frequency you're currently using if practical - don't waste time searching for a different one first. If you get no response, or you're not on a frequency being monitored, use the emergency frequency 121.5 MHz, which is guarded by ATC units and many other aircraft. Squawk 7700 on the transponder for distress if instructed or appropriate - this alerts radar controllers even before you speak.
Any station (including another aircraft) that hears a distress call and believes the aircraft needing help cannot communicate directly may relay the message - this is called a MAYDAY RELAY. Any station may also acknowledge a distress message if ATC doesn't respond immediately, so silence isn't a rule - someone should always answer.
Once the emergency is over, the pilot (or on their behalf, the controlling station) must broadcast a cancellation message, typically 'MAYDAY CANCEL' or 'PAN PAN CANCEL' with details, so the frequency and other traffic return to normal and search/rescue resources aren't tied up unnecessarily.
A transponder is a box that replies automatically to radar interrogations from ground secondary surveillance radar (SSR). It sends back a squawk code (four digits, each 0-7) and, if fitted, altitude data. This lets controllers see your identity and level on their screen, not just a blip.
These three emergency codes (7500/7600/7700) are internationally recognised, so never dial through them casually when changing squawks - always route around, for example 7000 to 2000 to 4000 rather than passing through 7500, 7600 or 7700.
Always select the assigned squawk and Altitude (ALT) or the correct mode before flight, and squawk standby only on the ground or when told to. Confirm 'IDENT' only when asked by ATC - it highlights your return on the controller's screen for a few seconds.
Outside controlled airspace a pilot can request one of these from a radar unit: