Radiotelephony for General Aviation Pilots Study Notes

Radio Licensing and Approvals

  • Requirement for FRTOL: In most circumstances, operating an aeronautical radio requires a Flight Radiotelephony Operators Licence (FRTOL). This is issued by the CAA and can be a stand-alone licence or held in conjunction with a flight crew licence.

  • Exemptions: Glider pilots and student pilots under training are exempt from holding an FRTOL under Article 139 of the Air Navigation Order 2016, subject to certain conditions.

    • Limitation: Glider pilots without an FRTOL are prohibited from using the radio to communicate with an Air Traffic Service Unit (ATSU) or Air/Ground Communication Service (AGCS).

  • Radio Equipment Licencing:

    • An Aircraft Radio Licence is required for equipment installed in the aircraft.

    • A Transportable Radio Licence is required for hand-held VHF radio equipment featuring an integral antenna and power supply.

    • These licences are issued by Ofcom.

  • Equipment Approval: All aircraft radio equipment (installed or hand-held) must be approved by the CAA.

    • Many hand-held radios with 8.33 kHz8.33\,\text{kHz} channel spacing are covered under a general CAA Light Aircraft Class 3 Equipment Approval.

Radio Equipment and Frequency Selection

  • VHF Frequency Band: Aircraft VHF voice communication occurs in the aeronautical band between 117.975 MHz117.975\,\text{MHz} and 137.000 MHz137.000\,\text{MHz}.

  • Channel Spacing: Radios use 8.33 kHz8.33\,\text{kHz} channel spacing, providing a potential for 22802280 individual channels.

  • Aeronautical Radio Navigation Band: Some sets also cover 108.000 MHz108.000\,\text{MHz} to 117.975 MHz117.975\,\text{MHz}, used for facilities like VOR and ILS.

  • Radio Operation Specifics:

    • Adjusting smaller decimals may require a specific toggle switch, pulling out a rotary knob, or a touchscreen input on modern integrated systems (e.g., GNSS navigation devices).

    • Users must ensure the channel spacing is explicitly set to 8.33 kHz8.33\,\text{kHz} if required.

    • Caution: Familiarize yourself with avionics like VFR Moving Maps or Electronic Conspicuity before flight to avoid serious distraction.

Volume, Squelch, and Intercom Functions

  • Squelch Definition: An electronic switch that mutes receiver audio output when signal is very weak or absent to reduce operator fatigue.

  • Variable Squelch: Allows the operator to set the threshold of signal strength required to hear a transmission.

  • Manual Squelch Setting Procedure:

    1. Set volume control to approximately halfway (50%50\%).

    2. Turn squelch up until a "hiss" (background static) is heard.

    3. Turn squelch back until the hiss just stops abruptly.

    4. Leave the control in this position.

  • Automatic Squelch: Often features a "TEST" switch to remove the squelch, useful for assessing volume against background noise or receiving weak signals like a distant ATIS.

  • Volume Limits: Ideally, volume should not exceed 70%70\% of the range to avoid sound distortion. Squelch cannot be set correctly while a transmission is being received.

  • Intercom Guidance:

    • Intercoms allow dialogue between occupants wearing headsets.

    • Intercom and headset controls must be adjusted independently of the radio.

    • Balance is critical: if the intercom is too loud, radio calls may be missed during conversation.

    • Intercoms may have their own separate squelch function for activation threshold.

Transponders and SSR Codes

  • Secondary Surveillance Radar (SSR): Transmits a 44-digit "squawk" code to ATSU surveillance screens.

  • Conspicuity Codes:

    • VFR: 70007000

    • IFR: 20002000 (Note: check state AIP as this is not universal).

  • Emergency/Special Codes:

    • Unlawful Interference: 75007500

    • Radio Communication Failure: 76007600

    • Emergency: 77007700

    • Lost (UK specific procedure): 00300030

  • Mode C (Charlie): Transmits aircraft level relative to 1013.2 hPa1013.2\,hPa. Requires "Altitude" (ALT) to be selected. Pressure setting adjustments on the altimeter do not affect the data sent by Mode C.

  • Mode S (Sierra): Features enhanced identification and potential for more data display.

  • IDENT Button: Highlights the aircraft's return on ATC screens. Only use when instructed by ATC saying "squawk IDENT".

  • Frequency Monitoring Codes (FMC): Squawk codes for listening to an ATSU frequency without establishing communication.

    • Allows ATC to contact an aircraft if it appears to be infringing controlled airspace (CAS).

    • Users must revert to a conspicuity code or another FMC when leaving the frequency.

Making Radio Calls and Phraseology

  • General Principles: Use standard phrases; keep transmissions concise; listen before speaking to avoid simultaneous transmissions.

  • Initial Call Format: Address the station name first, followed by your callsign (e.g., "Gatwick Approach, G-ABCD").

  • Subsequent Calls: Use only your own callsign. Only use abbreviated callsigns if the ATSU addresses you as such first.

  • Responses: Give the response/instruction first, then end with your callsign (e.g., "Runway 06, cleared for take-off, G-CD").

  • Voice Clarity:

    • Microphone close to mouth; speak directly into it.

    • Press the PTT button firmly before speaking and do not release until finished.

    • Avoid filler words like "this is", "and", or "with you".

    • Avoid inflections to ask questions; use words like "Confirm".

Readbacks and Frequency Changes

  • Mandatory Readback Items:

    1. Taxi/towing instructions

    2. Level instructions

    3. Heading instructions

    4. Speed instructions

    5. Airway or enroute clearances

    6. Approach clearances

    7. Runway-in-use

    8. Clearance to take off or land

    9. Clearance to enter, backtrack, cross, or hold short of an active runway

    10. Transponder instructions (squawk codes and Ident)

    11. Altimeter settings (including units if below 1000 hPa1000\,hPa)

    12. VDF information

    13. Frequency changes

    14. Type of ATS service

    15. Transition Levels

  • Frequency Departure Procedure: Inform the current station of the move and subsequent intentions. Set the appropriate squawk code (conspicuity or FMC) with ALT selected.

Aerodrome Operations: Circuit Procedures

  • Standard Reports: High traffic areas require position reports at "Downwind" and "Final". "Base leg" or "Crosswind" may be used for situational awareness.

  • Overhead Joins: Clearly report "in the overhead" and descending "deadside".

  • The "Final" Report:

    • Final: Position between 4 NM4\,NM and the landing threshold.

    • Long Final: Position between 4 NM4\,NM and 8 NM8\,NM from the threshold.

    • Short Final: No official term; instead, specify distance (e.g., "half-mile final").

Air Traffic Service Units (ATSU) Types

  • Air Traffic Control (ATC): Provided by ATCOs. Can issue mandatory clearances/instructions in the air and on the ground.

    • Callsigns: "Approach", "Radar", "Tower", "Ground".

    • Arrival: Call 15 NM15\,NM or 5 minutes5\,\text{minutes} from the ATZ boundary. State intention on initial call and acknowledge ATIS.

    • Taxi: Instructions include a "clearance limit" (usually a runway holding point).

  • Aerodrome Flight Information Service (AFIS):

    • Callsign Suffix: "Information".

    • Authority: In the UK, can issue mandatory ground instructions up to the holding point. This is a UK difference from ICAO (where AFIS usually issues no instructions).

    • In the Air: Cannot issue instructions; reports are for situational awareness only.

    • Landing: Use the term "land at your discretion". This is NOT a clearance; the pilot must judge if the runway is clear and respond with "landing".

  • Air/Ground Communication Service (AGCS):

    • Callsign Suffix: "Radio".

    • Authority: No power to issue clearances or instructions. Information (weather/traffic) is advisory only.

    • Operation: Aircraft announce positions and separate themselves. Manoeuvres (taxi, land) should only be done if satisfied it is safe.

Unattended Aerodromes and SAFETYCOM

  • SAFETYCOM Frequency: 135.480 MHz135.480\,\text{MHz}. Used within 10 NM10\,NM and up to 1000 ft1000\,ft above circuit height at aerodromes with no assigned frequency.

  • Callsign: Use "[Aerodrome Name] Traffic" at the start and end of transmissions to avoid confusion with nearby fields.

  • Procedure: Announce taxiing, lining up, overhead join, deadside descent, downwind, and final.

UK Flight Information Services (UK FIS)

  • Service Levels:

    • Basic Service: Pilot is responsible for collision avoidance; ATCO/FISO provides information subject to workload.

    • Traffic Service: ATCO provides specific traffic information using radar; no deconfliction advice is provided.

    • Deconfliction Service: (IFR only) ATCO provides traffic information and deconfliction advice; pilot retains ultimate responsibility.

  • Service Providers: London Information, Scottish Information (FIS); specific ATSUs participate in Lower Airspace Radar Services (LARS) up to FL100FL100.

  • Requesting UK FIS ("Freecall"):

    1. Callsign

    2. Aircraft type

    3. Point of departure

    4. Destination

    5. Current position

    6. Current altitude and altimeter setting

    7. VFR or IFR

    8. Routing/intentions

Transit of Controlled Airspace and Special VFR

  • Controlled Airspace (CAS): Most UK CTR/CTAs are Class D (permits VFR subject to ATC clearance).

  • Transit Request: Call approximately 10 minutes10\,\text{minutes} from boundary. Include preferred entry/exit points.

  • Radar Control Service: Indicates the controller may give mandatory course/altitude instructions. If unable to maintain VMC, inform ATC immediately.

  • Special VFR (SVFR): Provision for flight in CTR when conditions are below VMC minima. Subject to ATC separation delays. Pilot must provide callsign, type, intentions, and ETA at entry point.

Military ATC and MATZ

  • Frequency Difference: Military ATC primarily uses UHF (225−380 MHz225-380\,\text{MHz}). VHF users may experience delay as controllers talk to military aircraft on UHF simultaneously.

  • Military Air Traffic Zone (MATZ): Not controlled airspace for civilian aircraft, but contacting the unit for a "MATZ penetration service" is strongly recommended.

Emergency Communications (Mayday and Pan Pan)

  • Levels of Emergency:

    1. Distress (MAYDAY): Serious/imminent danger, requires immediate assistance.

    2. Urgency (PAN PAN): Safety of aircraft/person concern, does not require immediate assistance.

  • Format of Call:

    1. MAYDAY/PAN PAN (x3)

    2. Station addressed

    3. Callsign

    4. Type of aircraft

    5. Nature of emergency

    6. Intentions

    7. Position (height and heading)

    8. Pilot qualification (e.g., student, no instrument rating)

    9. Other info (POB, endurance)

  • London Centre (121.5 MHz): The Distress and Diversion (D&D) cell for UK emergencies.

  • Protocol: Select 77007700 on the transponder. "Mayday out" signals no further reply needed. Other pilots must maintain radio silence until cancelled.

Radio Failure and Lost Procedures

  • Priorities: Fly the aircraft first. Maintain VMC and effective lookout. Stay clear of CAS.

  • Troubleshooting Checklist:

    • Check frequency and range.

    • Check Master Switch and Avionics switches.

    • Verify Audio Selector Panel, Volume, and Squelch.

    • Check PTT button, headset plugs, and Circuit Breakers (reset once).

    • Try alternative radio or the emergency frequency 121.5 MHz121.5\,\text{MHz}.

  • Failure Procedure:

    1. Set 76007600 on transponder.

    2. Transmit "blind" if receive function suspected failing.

    3. Observe signal square/circuit at aerodrome.

  • Lost Procedures:

    • Select 00300030 with ALT on transponder.

    • Contact a surveillance ATSU or "London Centre" on 121.5 MHz121.5\,\text{MHz}.

    • Request a "position fix" or VDF bearing/heading.

    • Note: Do not request "training fixes" in a real lost scenario.