ATC Basics

Introduction

ATC is not as complicated (or intimidating) as many pilots might think. If you join an online ATC system you may find it very similar to the default ATC in FS (which is really quite good within its limitations) but there are one or two rules that you should learn to make your flights acceptable in the ATC world.

With VFR flights ATC involvement is mostly confined to the airfields and in integrating traffic within the circuit and on the ground. In this respect online ATC will be very similar to the default ATC in FS and provide correct joining instructions, taxy instructions and En route it can be much quieter because VFR pilots are responsible for terrain clearance and avoiding other traffic. ATC may provide traffic alerts if a pilot has requested a Traffic Service. Pilots should (as in real life) request clearance through any military or civil controlled airspace that is active.

IFR flights are conducted almost completely under ATC control and pilots can expect vectors, reroutes, clearances and radar or ILS approaches. This is not dissimilar to the ATC provided in FS2002/4 when you have filed an IFR flight plan.

Basic Height Rules

For MP sessions in the UK pilots should follow the height rule table shown below. This is good air sense, is identical to real world operations and will not confuse controllers when you appear on radar. It will also ensure you don't hit any other aircraft if you are flying in an area which is not under active ATC.

VFR Flights
Flying Below 3000ft	No mandatory height - but note your minimum safety altitude.

Flying Above 3000ft	Aircraft Track (Mag)	Flight Level
	000 to 089	ODD Levels	FL50, FL70, FL90, FL110 etc
	090 to 179	ODD +500ft	FL55, FL75, FL95, FL115 etc
	180 to 269	EVEN Levels	FL40, FL60, FL80, FL100, FL120 etc
	270 to 359	EVEN +500ft	FL45, FL65, FL85, FL105, FL125 etc

IFR Flights
	Flight Direction	Flight Level
	Eastbound (000 to 179)	ODD LEVELS	FL50, FL70, FL90, FL110 etc
	Westbound (180 to 359)	EVEN LEVELS	FL40, FL60, FL80, FL100, FL120 etc

So, for flights below 3000ft, pilots can fly at any height they wish regardless of their track - as long as they stay above the minima for low flying. Above 3000ft they should fly according to the tables above - or at a height specified by ATC if this is different.

The 3000ft height for this changeover is known as the Transition Altitude and is generic within the UK outside controlled airspace. To make life slightly more difficult each control zone can specify a different TA. In the London and Manchester CTR's the TA is raised to 6000ft to tie in with SID/STAR procedures. In other countries the TA may be even higher - in the USA it is up at 18000ft.

Height calls follow quite exact terminology. If flying on the QNH (which gives you height above sea level) pilots should refer to their height as ALTITUDE and call "passing 1500ft" or "maintaining 3000ft" - they should never use "Flight Level". Above 3000ft the correct term is FLIGHT LEVEL and you should call "passing Flight Level 45" or "maintaining Flight Level 250". However this assumes you have reset your altimeter to 29.92" or 1013.2mb when climbing through the Transition Altitude as is done in real life.

The other subtle use of terminology is when using the words Altitude and Height. Altitude is recognised as meaning height above sea level - flying on the QNH. Height is used when flying on QFE - height above airfield level. QFE is being used much less in aviation these days and could possibly fade away.

ATC Procedures

Who's Responsibility is it?

It is prudent here to specify just who is responsible for what when you fly in an ATC environment. This is more important for VFR pilots because ATC does not necessarily mean they are in charge of your flight.

IFR traffic

In controlled airspace this is directed by ATC for the duration of the flight and pilots will be required to follow headings, speeds or altitudes assigned by the controller. In return the controller is responsible for your terrain clearance and for separation from other aircraft.

Outside controlled airspace IFR traffic is responsible for its own separation and terrain clearance unless the pilot is being provided with an ATC service such as ATSOCAS (Air Traffic Service outside Controlled Airspace).

VFR traffic

VFR aircraft are responsible for their own terrain clearance and separation from other aircraft.

If VFR traffic outside controlled airspace is being provided with an ATC service (such as ATSOCAS) then ATC will offer one of the following options to the pilot:

Deconfliction Service - With DS pilots will be given ATC instructions to avoid other aircraft and they must comply with these. (ATC is responsible for separation)

Traffic Service - With TS pilots will be warned by ATC of any conflicting traffic but it is then up to the pilot to decide what action should be taken. (Pilot is responsible for separation).

Basic Service - With BS no information on other traffic is provided by ATC but they can supply weather or airfield information on request. This is typical for units without a radar service.

Inside controlled airspace VFR aircraft will be given traffic information on other aircraft. They may also be given heading instructions on the understanding that the pilot must remain VFR (and should decline a heading if it is likely to take the aircraft into IMC conditions). Alternatively ATC may ask a pilot to route to a VRP (Visual Reporting Point) and leave navigation to the pilot.

Typical R/T procedure

The examples below are typical of exchanges between aircraft and ATC for a normal flight. I have not embellished the example with specifics like parking locations, ATIS, SID's or STAR's that may be required at larger or busier airfields.

Note that I have omitted the mandatory readback by aircraft required for specific instructions. Pilots do not have to read back everything the controller says (like the weather) but they should always read back the following:

Instructions - headings, altitudes, speeds.
Clearances - taxi, take off, landing and airways.
Weather - only pressure values.

You will notice that R/T is always kept to a minimum with calls being limited to essential information only. As ATC has your flight details already only items that are changing (heading or height for example) will feature in an R/T call. Note also that I am using typical R/T examples rather than those found in the "book" (CAP413)

VFR		IFR
Aircraft	ATC	Aircraft	ATC
Bagby Tower this is G-ODLY, ready to taxi.	G-LY taxi to A1 hold for runway 26 via taxiway Alpha, QNH 1014	Bagby Tower this is Airflo 597 ready for start.	Airflo 597 start approved, temp +15
Bagby Twr, G-LY ready for line up on 26.	Roger. G-LY your clearance is to leave the zone on track, maintain VFR. Line up rwy 26.	Bagby Twr, Airflo 597 ready for taxi	Airflo 597 taxi to A1 hold runway 26 via Alpha, QNH 1014
Bagby Twr, G-LY ready for take off.	G-LY is cleared for take off. Wind 250/12kts	Bagby Twr, Airflo 597 ready for clearance.	Airflo 597 is cleared to Gattow via B1 and C3. Climb to FL130, Squawk 5265
Bagby Twr, G-LY on course, climbing to 2500ft.	Roger G-LY, call approach on 125.3	Roger, Airflo 597 is cleared B1 C3 to Gattow, climbing to FL130. Squawk 5265	Airflo 597 clearance correct. After the landing B737 line up rwy 26
Bagby Approach, GODLY, level at 2500ft	G-LY you are clear of my zone, call Winton Radar on 132.5.	After the landing 737 line up, Airflo 597	Airflo 597 is cleared for take off. Wind 250 at 15.
Winton Radar, G-LY with you at 2500ft.	Roger G-LY, squawk 3441.	Airflo 597 is cleared for take off.	Airflo 597 call Bagby Radar on 124.75
Squawking 3441, G-LY	G-LY is identified 7nm W of Bing, report if you leave 2500ft.	Bagby Radar, Airflo 597 with you, passing FL55 for FL130	Thank you Airflo 597, maintain your present heading and continue climb to FL250
G-LY wilco	G-LY traffic at ten o clock at 5nm is a C177 at 3000ft. Report in sight.	Roger, on heading 135 continue climb to FL250, Airflo 597	Airflo 597 contact London Centre on 134.3
G-LY, traffic in sight.	G-LY is clear of my airspace, squawk 7000	London Centre, Airflo 597 with you, heading 135 and out of FL140 for 230	Thank you Airflo 597, turn right heading 160
Squawking 7000, G-LY.	(If clear of any airspace R/T is not mandatory with any ATC unit and pilots may simply call their destination airport about ten minutes away from landing - as will be shown here)	Right onto 160, Airflo 597	(Time passes) Airflo 597 resume your own navigation direct to OWL VOR
Stanfield Approach this is GODLY	GODLY this is Stanfield Approach, pass your message.	Airflo 597 level at FL230 routing direct to OWL	Airflo 597 roger. Contact Shannon Centre on 133.1 g'day.
GODLY is a PA28 inbound from Bagby, overhead Cranberry this time, VFR at 2500ft and estimating your field at 1255	Roger G-LY, continue to the field VFR, report the airfield in sight.	Shannon this is Airflo 597, level FL230.	Airflo 597 this is Shannon, turn left heading 110, descend to FL110
G-LY, field in sight.	Roger G-LY, join downwind left hand for runway 34, QNH 1024	Airflo 597 is turning left onto 110 and leaving 230 for 110.	Airflo 597 expedite your descent.
G-LY join downwind left for 34, QNH 1024	G-LY contact Stanfield Twr on 119.4	Airflo 597 wilco	Airflo 597 turn left heading 080 and call Mayo Approach on 120.15
Stanfield Twr, GODLY with you, downwind left for 34	G-LY thank you report final for 34, you are No1 to land.	Left onto 080 and changing to Mayo on 120.15 Airflo 597
G-LY is finals for 34	G-LY is cleared to land. Wind is 330 at 15	Mayo, this is Airflo 597 heading 080 and passing 130 for 110	Airflo 597 continue descent to 5000ft on QNH 1019, radar vectoring for ILS approach runway 34 with no delay
G-LY, cleared to land.	G-LY, take the next taxiway on your right and turn left at the end for the apron. Follow the marshallers instructions.	Continuing descent to 5000ft on QNH 1019, to expect ILS approach 34 Airflo 597	Airflo 597 turn left heading 010, descend to 3500ft on new QNH 1018
		Turn left heading 010 and descend to 3500ft. QNH now 1018 Airflo 597.	Airflo 597 12nm to run, closing the localiser from the left, report established.
		Airflo 597 is localiser established	Airflo 597 descend on the ILS. Contact Mayo Twr on 114.8
		Mayo Twr, Airflo 597 descending on the ILS for 34	Airflo 597 is cleared to land on 34. Wind is 330 at 12kt
		Cleared to land, Airflo 597	--- Airflo 597 vacate right via Charlie and Echo, parking Stand 14
		Charlie and Echo for Stand 14, Airflo 597

CAA Documents

Rather than take up several pages with further descriptions and examples of R/T procedures it would be better to suggest you read the real R/T Phraseology document. Don't be put off by this statement - the book is written for private pilots and is therefore easy to follow!

The good news is that all civil aviation publications (CAP's) are now available free from the CAA web site. You will find their library section at http://www.caa.co.uk/publications/search.asp. Look for CAP413 Radio Telephony Manual. You can download this as a PDF file.

The Cap's cover everything to do with aeronautical regulation in the UK. This ranges from CAP393 (Air Navigation: The Order and Regulations) which is our "legal Bible" right down to CAP680 (Aerodrome Bird Control). Those that may be of interest to FS users include:

CAP413 Radio telephony Manual	A guide to R/T procedures. Lots of examples of VFR as well as IFR radio calls.
CAP168 Licensing of Aerodromes	An excellent source book for airfield designers. Illustrations of airfield, runway and taxiways markings with correct dimensions. Also covers lighting and airfield signs. It is extremely detailed!
CAP393 Air Navigation: The Order and Regulations	The legal side to UK Aviation - but there is much here of interest. Rule 5 on Low Flying, Rule 21 airspace. How many hostesses and aircraft needs and what must be carried on a flight over the North Pole (at least one ice axe if you really want to know).
CAP637 Visual Aids Handbook	Marshalling signs, apron signs and all that stuff in a small handy booklet.
GASIL General Aviation Safety Information Leaflet	An excellent quarterly magazine that studies accidents and incidents to UK aircraft. A very good read.

There are many more but I'll leave the browsing to you!