resource R_TWR and I_TWR - Demystified

[Dale Stainrod]

Introduction

Imagine you've just loaded up at a small aerodrome in the UK and connected to VATSIM. This time though, you aren't calling to UNICOM as you've just spotted an I_TWR with a corresponding ICAO in your controller list... how do you deal with it? This post is here to explain.

Callsign Conventions, in order of Control Authority

• _TWR (e.g. "Gatwick Tower") - Full air traffic control service is provided here. You will be given taxi instructions, ATC and runway clearances.
• _I_TWR (e.g. "Goodwood Information") - Taxi instructions only, traffic and other information available within the ATZ and surrounding area (basic service).
  • Often referred to as AFIS (Aerodrome Flight Information Service).
• _R_TWR (e.g. "Gamston Radio") - Not classified as an air traffic service, has no control authority. Passes airfield information and (typically) traffic information when manned.
  • Often referred to as AGCS (Air/Ground Communication Service)

A _TWR position won't be covered in this topic and is listed only for clarity as to the distinguishment.

Initial Call (Departing)

Adopt the WWWR Mnemonic:

• Who you are (your callsign);
• What you are (your aircraft type);
• Where you are (your position on the airfield);
• Request (what you need).

e.g. "Goodwood Information, G-PTDA, Cessna 172 on the Light Aircraft Parking, request Airfield Information, VFR departure to the South"

You can also combine your airfield information request with a request for taxi, if you're ready.

And you can expect back:

• Runway in use;
• Circuit direction;
• Pressure setting (usually QFE).

e.g. "G-PTDA, Goodwood Information, Runway 24, Right Hand Circuit, QFE 1021"

Taxi (_I_TWR)

When you're at an Air/Ground (_R_TWR) facility, you shouldn't request taxi, just announce your intentions! However, for AFIS, you will need to request taxi just like at an aerodrome with full air traffic control services.

e.g. "G-DA, request taxi"

And you can expect back:

"G-DA, taxi holding point runway 24"

... in this case the holding point is short of runway 24, as there are no established holding points.

Departure

e.g. "G-DA, holding point runway 24, ready for departure"

And you can expect back (AFIS):

"G-DA, no reported traffic, runway 24, surface wind 210 degrees 4 knots, take-off at your discretion"

OR:

"G-DA, traffic is a Cessna 152 left base, runway 24, surface wind 210 degrees 4 knots, take-off at your discretion"

And you can expect back (AGCS):

"G-DA, roger, surface wind 210 degrees 4 knots"

OR:

"G-DA, traffic is a Cessna 152 left base, surface wind 210 degrees 4 knots"

After Departure

Upon leaving the ATZ, you can report changing frequency. At an AFISO-manned aerodrome where there is no surrounding radar services, it may be advisable to remain on the frequency for a short while. Some AFISOs may advise you that you're under a basic service, although this is a 'given' until you report changing. However, at AGCS aerodromes, you are not under any sort of ATS, and they likely have no further information useful to you.

e.g. "G-DA, now leaving the ATZ, changing to Gatwick Director 126.825"

And you can expect back:

"G-DA, roger."

Joining to Land

You should aim to call an AFIS or AGCS unit 10 nautical miles or 10 minutes before landing, whichever is sooner.

e.g. "Goodwood Information, G-PTDA, request join"

And you can expect back:

"G-PTDA, Goodwood Information, pass your message"

... then, you reply with the WWWR Mnemonic:

e.g. "G-PTDA, Cessna 172, 8 Miles South, request Airfield Information"

And you can expect back (no prizes for guessing!):

"G-DA, Runway 24, Right Hand Circuit, QFE 1021"

... you should then read back this information and report your joining intentions. An AFISO will ask you to report that leg, e.g. "report downwind", whereas an AGRO (Air/Ground Radio Operator) will not - you should do it anyway.

In Conclusion

Thank you for reading this topic! I hope you found it useful in some way or another. Here are some additional resources which you can use to see the more practical application of these RT extracts:

• AFIS Video
• AGCS Video

Happy flying!

Edited November 26, 2022 by Dale Stainrod