Study Guide:Tower

Introduction

This Study Guide has been designed to give you all the information needed to start controlling as a Tower controller on the VATSIM network.

Radio Communication - Basics

Because Communication is crucially important for Air Traffic Control a fixed format and syntax us used, in order to minimize the risk of misunderstandings and to keep messages short. Worldwide English is the primary language in use, however in most countries you are also allowed to use the local language. In Austria VFR flights can choose their language whereas IFR flights are mostly conducted in English. Link: Buchstabiertabelle

Basic Rules

In order to achieve the goals set above the following rules important:

1. Listen before you talk

   It's impossible for two radio stations to transmit on the same frequency at the same time. If this is done, the radio signal will be blocked and this will result in a nasty noise on the frequency. Therefore it's important that every station monitors the frequency for about 5 seconds before transmitting, to make sure there’s no ongoing radio traffic. If you hear an ongoing conversation, wait until the conversation is over before you begin to transmit. Don’t start your communication if there is a read-back expected on the last transmission even if there is a short pause.

2. Think before you talk

   The radio traffic flow should be as smooth as possible. To achieve this it's vital to "think first" before transmitting so that a clear, concise and uninterrupted message can be sent.

3. As far as possible use standard phraseology and syntax

   To prevent misunderstandings and to maintain the radio traffic as effective as possible, stick to standardized phraseology and skip slang and of course private messages.

Callsigns and Initial Contact

Every participant on the network has his own Callsign. Controller Positions are identified by their location and their Function (e.g. Wien Radar, Graz Tower), Aircraft either by their Registration (e.g. OE-ALB) or an Airline Callsign followed by a combination of numbers and letters (e.g. AUA25LM, SWR387). To pronounce these letters and digits the ICAO-Alphabet is used. To initiate the contact between two stations an initial call has to be made. This call has the following structure:

Station 1: Station 2, Station 1, Message 
Station 2: Station 1, Station 2, Message

Example - Austrian 251 is calling Wien Tower:

AUA251: Wien Tower, Austrian 251, established ILS 34 
LOWW_TWR: Austrian 251, Wien Tower, continue approach

In Subsequent calls the calling station part can be ommited.
When a controller (or aircraft) transmits a message to a station it is very important that the receiving station acknowledge the message and reads back any required parts.. If the receiving station does not acknowledge, the transmitted message is considered as a lost transmission and the sender should resend the message or check if the receiving station got the message. Items that must always be read back in full are all clearances (including altitudes, heaings, speeds, radials etc), runway in use, altimeter setting (QNH or QFE) and transition level, and all frequencies. For a controller, this is extremely important to remember, since if a pilot's readback is incorrect, the controller has to ask for confirmation, i.e a new readback. There are also items that should not be read back to reduce unnesessary radio transmissions. In short, this includes everything not mentioned above, but a few examples are: wind, temperature and other weather information (except altimeter settings) and traffic information in detail. When giving an instruction the Callsign is stated at the beginning, when reading back you usually add it at the end of your transmission (although you are allowed to do it at the beginning too).

Examples:

LOWW_APP: AUA251, turn left heading 290, descend to Altitude 5000 feet, QNH 1019.
AUA251: Turn left heading 290, descending to altitude 5000 feet QNH 1019, AUA251 

LOWW_GND: OE-DLT, taxi to Holding Point Runway 29 via Exit 12, M and A1, give way to Speedbird Airbus A320 crossing you right to left on M.
OE-DLT: Taxiing to H/P Rwy 29 via Exit 12, M and A1, giving way to Speedbird Airbus A320 on M, OE-DLT.

LOWW_TWR: NLY2678, wind 330 degrees at 6 knots, Rwy 29, cleared for takeoff.
NLY2678: Rwy 29, cleared for takeoff, NLY2678.

METAR and TAF

References for detailed information: METAR, TAF

How is an Aerodrome Organized?

Der TWR (Flugplatzkontrollstelle) ist zuständig für den :

Flugplatzverkehr
Personen und Fahrzeugverkehr auf Manövrierflächen

Nachdem Follow-Me Fahrzeuge nicht mehr eingesetzt werden dürfen entfällt hier der zweite Punkt.
Die Flugplatzkontrollstelle kann nun auch weiter untergliedert werden in die Positionen Delivery (DEL), Ground/Rollkontrolle (GND) sowie Tower/Turm (TWR).

Die nächst höher gelegene "Instanz" ist die APP (Anflugkontrollstelle)

Kontrollierte An- und Abflüge

Die Anflugkontrollstelle in Wien ist für An- und Abflüge zuständig und kann bei Bedarf sektorisiert werden. So kann man den LOWW_APP in jeweils einen Nord-Süd Sektor teilen, oder aber in einen Upper-Lower Sektor aufteilen. Zu Spitzenzeiten werden die Sektoren nach beiden Verfahren geteilt, noch dazu wird eine Director-Position eingerichtet, die LFZ vom Lower Approach auf das ILS führen.

Darüber befindet sich die ACC (CTR) Bezirkskontrollstelle

Für alle übrigen kontrollierten Flüge

Bei VATSIM bearbeitet der LOVV_CTR das gesamte Bundesgebiet und übernimmt auch die Tätigkeit des TWR & APP auf allen österreichischen Flughäfen, sollten diese nicht online sein. Das Gebiet Tirol & Vorarlberg über FL165 wird nicht von LOVV kontrolliert, sondern im Auftrag der ACG von der deutschen Flugsicherung mitbetreut (EDMM).
>br> Alle drei Kontrollstellen üben den Kontrolldienst gemäß §68 Abs.1 LVR aus und erfüllen folgende Aufgaben:

Sicherheit gewährleisten durch
 Vermeidung von Zusammenstößen zwischen Luftfahrzeugen
 Vermeidung von Zusammenstößen zwischen Luftfahrzeugen und Hindernissen auf den Manövrierflächen
Wirtschaftlichkeit gewährleisten durch raschen, flüssigen und geordneten Ablauf des Verkehrs

Diese Aufgaben gelten auch für den Controller in VATSIM, wenn auch aus anderen Beweggründen. In dem Wunsch so nahe an die Realität wie möglich zu kommen, sind diese Leitfäden unerlässlich.

Working Delivery Positions

Clearence Delivery is responsible for checking and correcting flightplans of departing aircraft and issue routing clearances to them.

Flightplan Structure

Flight plans are documents filed by pilots with the local Civil Aviation Authority prior to departure. They generally include basic information such as departure and arrival points, estimated time en route, alternate airports in case of bad weather, type of flight (whether instrument flight rules or visual flight rules), pilot's name and number of people on board.
For IFR flights, flight plans are used by air traffic control to initiate tracking and routing services. For VFR flights, their only purpose is to provide needed information should search and rescue operations be required.

Aircraft routing types used in flight planning are: Airway, Navaid and Direct. A route may be composed of segments of different routing types.

• Airway: Airway routing occurs along pre-defined pathways called Airways. Mostly aircraft are required to fly airways between the departure and destination airports. The rules cover altitude, airspeed, and requirements for entering and leaving the airway (SIDs and STARs).
• Navaid: Navaid routing occurs between Navaids (short for Navigational Aids) which are not always connected by airways. Navaid routing is typically only allowed in the continental U.S. If a flight plan specifies Navaid routing between two Navaids which are connected via an airway, the rules for that particular airway must be followed as if the aircraft was flying Airway routing between those two Navaids. Allowable altitudes are covered in Flight Levels.
• Direct: Direct routing occurs when one or both of the route segment endpoints are at a latitude/longitude which is not located at a Navaid. This is a routing from Vienna

Issuing IFR Routing Clearances

DEL gives routing clearances to all departing aircraft with the following information:

Destination of aircraft
SID (= Standard instrument departure) Normally the filed SID is given
Initial climb altitude after departure (5000ft)
Squawk (Squawk assignments for LOWW are 4600 to 4620)
QNH (Local QNH of airport according to latest METAR)
CTOT (= Calculated take-off time) Slot time (Normally not used on the VATSIM network)

The bold marked points are mandatory, all other points are optional.

Normal construction of a routing clearence:

Callsign, cleared to XXXX via XXXXX XX departure, (climb initially 5000ft), Squawk 46XX, QNH XXXX

Example:

Austrian 125, cleared to Frankfurt via LUGIM 1C departure, climb initially 5000ft, Squawk 4601, QNH 1020.

Some Aircraft are not able to follow SIDs for various reasons, most of the time due to missing equipment. In these cases you should issue a so called vectored departure. A vectored departure clearance includes the same components as a normal clearance but instead of the SID you issue instructions to be carried out after departure. In this case the initial climb altitude is mandatory.

Callsign,cleared to XXXX, after departure rwy XX, XXXXXXX, climb initially 5000ft, Squawk 46XX, QNH XXXX 

Example:

Austrian 125, cleared to Frankfurt, after departure Runway 29, turn left heading 240expect vectors to LUGIM, initially climb to 5000 ft, Squawk 4601, QNH 1020.

You can find the instructions for each Airport within the Study Guide:Airport Details If the pilot responds with a correct readback you should answer with the following phrase:

Callsign, readback correct.

Afterwards you either hand the pilot over to GND or wait for his startup request, depending on local procedures.

Special Situations (High Traffic, Slots, ...)

Slots

Um auch bei hohen Verkehrsaufkommen einen geordneten Verkehrsfluss zu gewährleisten und um Verspätungen in der Luft nach Möglichkeit gering zu halten, werden sogenannte Slots eingesetzt. Ein Slot ist der Zeitraum von fünf Minuten vor bis 10 Minuten nach der oben erwähnten CTOT. Innerhalb dieses Zeitfensters soll der Start des Flugzeugs von seinem Startflughafen erfolgen. Im VATSIM Netzwerk wird dieses System nur in Ausnahmefällen, meistens bei Events eingesetzt.

Verhalten in Situationen mit erhöhtem Verkehrsaufkommen

Mitunter kommt es vor, dass eine der übergeordneten Positionen mit dem Verkehrsaufkommen nicht mehr zurecht kommt und keine neuen Flugzeuge mehr annehmen kann. In solchen Fällen sollte man den Start-Up der betroffenen Flugzeuge verzögern.

Piloten am Boden kann man mit Hinweisen auf die zu erwartende Verzögerung das Leben leichter machen:

Austrian 125, readback correct, expect startup in 10 minutes.
Austrian 125, startup approved, expect departure in 10 minutes.

Working Ground Positions

Ground is responsible for all movements of aircraft on ground, except the movements on the runway. Ground takes over responsibility for Delivery if he is not online.

Start-up clearence
Start-up clearence can be given if no other aircraft is taxiing behind the starting-up aircraft and if the take-off is expected in 20 minutes or less.

Austrian 125, start-up approved, (Temperature Minus 3)

Push-back clearence
Push-back clearence can be given if no other aircraft is passing behind and the parking position requires push-back (i.e. position at the gate, … [refer to charts])

Austrian 125, push-back approved”

Combination of both phrases
During low traffic you can use these two phrases together

Austrian 125, start(-up) and push(-back) approved

Taxi Instructions

The easiest way giving taxi instructions to aircraft is to:

Taxi outgoing aircraft on taxiway MIKE (former OSCAR) ASAP.
Taxi incoming aircraft on taxiway LIMA (former INDIA) ASAP.

In this way, collision of aircraft should be avoided. Incoming aircraft on runway 16/34 vacating via B3 to B10 should use taxiway DELTA and LIMA (former INDIA).

Ground Traffic Management

In case of a landing on runway 29 no aircraft is allowed to be in the extended runway centreline of runway 29 while landing aircraft is passing above. In this case aircraft should hold at ROMEO, FOXTROTT, SIERRA and GOLF and wait until the incoming aircraft touched down.
You can also advise aircraft to follow behind another aircraft or give way to other taxiing aircraft.

Austrian 125, follow Airbus 320 to holding-point runway 29
Austrian 125, give way to taxiing Airbus 320 passing from left to right

When an aircraft is approaching its assigned holding-point (and clear of possible traffic-conflict) a hand-off to next higher position (i.e. TWR) shall be initiated as soon as possible.

Austrian 125, contact Tower on 119.40

Intersection take-off
Intersection takeoffs can be granted by GND in coordination with TWR and in accordance or on pilot’s request.

Special Situations (High Traffic, Slots, ...)

Um zügigen Verkehrsfluß bei starkem Verkehr aufrecht zu erhalten, gilt es dem ankommenden Verkehr höhere Priorität als dem abfliegenden Verkehr zu gewährleisten. Hier sollte vor allem die Vergabe von Slots oder die Errichtung von Abflugintervallen eine große Rolle spielen. Ein Slot ist ein gewisser Zeitraum in dem ein Pilot seinen Start-Up, Taxi und Abflug durchführen sollte. Ein Slot folgt also dem anderen. Abflugintervalle dienen dazu, eine relativ große Anzahl von Abflügen in einem gewissen Zeitraum zwischen zwei Wellen vieler ankommender Flüge abzufertigen. Um genug Freiraum für Abflüge zu haben, ist die Koordination mit den Approach Positionen unumgämglich.

Phrasenzusätze in Situationen mit erhöhtem Verkehrsaufkommen

Um den Piloten eine Anweisung mit Nachdruck bekannt zu machen sollen folgende Phrasen angehängt werden. Dies ist vor allem bei der Runway Separation anzuwenden.

Austrian 125, ready for immediate departure?
Austrian 125, wind xxx/xx - runway 29 cleared for immediate takleoff

Traffic im Anflug kann man auch bitten die Runway rasch zu verlassen:

Austrian 125, wind xxx/xx runway 34 cleared to land, vacate as soon as practicable

Abfliegenden VFR Verkehr kann man darauf hinweisen den Abflugsektor rasch frei zu machen:

OE-ABC, wind xxx/xx runway 29 cleared for takeoff, after departure right turn as soon as practicable

Working Tower Positions

Tower is responsible for all movements on the runways as well as for all movements within the control zone (CTR), (10NM radius, GND to 2500ft MSL). Tower is also responsible for ground and delivery if they are not online. He also decides which runways are in use.

ATIS

Bei der ATIS (Automatic Terminal Information Service) handelt es sich um eine automatisch generierte Informationsdurchsage für den Flugverkehr an größeren Flughäfen. Sie wird auf einer eigenen Frequenz in einer Endlosschleife gesendet und soll die aktiven Funkstationen am Flughafen entlasten. Piloten, die unter IFR an- oder abfliegen, sind verpflichtet, vor dem Erstkontakt mit der zuständigen Flugverkehrskontrollstelle zunächst das ATIS abzuhören. Beim Erstkontakt nennt der Pilot den ATIS-Kennbuchbuchstaben, um dem Controller zu bestätigen, dass er die aktuelle Version abgehört hat.

Bestandteile einer ATIS Meldung:

• Name des Flughafens
• Laufender ATIS-Kennbuchstabe
• Zeit der Beobachtung des Flugplatzwetters
• Aktive Landebahn
• Übergangshöhe
• Windrichtung und -geschwindigkeit
• Flugsichten
• besondere Wetterlagen (z.B. Regen)
• Hauptwolkenuntergrenze
• Temperatur und Taupunkt
• QNH
• Änderungstrend

Die ATIS wird alle 30 Minuten oder bei signifikanten Wetteränderungen erneuert.

Determination of active Runways

Pilots normally prefer to takeoff and land the aircraft with the nose into the wind because it shortens the Rwy length required to safely operate the aircraft. The wind direction given in the METAR is the direction the wind is coming from, so it is easy to compare this wind to your given runways.
Example:

You are the Tower controller at Salzburg Airport. The only runway at Salzburg is runway 16-34 so you have two directions available (roughly 160° and 340°.) The wind is coming from 180° at 5 knots. So the usual Runway in use would be rwy 16 for takeoff and landing.

However, at most airports a preferred runway configuration is defined (Find them here: Study Guide:Airport Details) which should be used if traffic situation and weather permits. Aircraft have certain limitations they can operate in, so normally the tailwind component should not exceed 5-10 knots (again depending on airport). Also the allowed crosswind is limited (This depends very much on the aircraft).
Be aware that it is the pilots responsibility to accept a certain wind component and that this decision is often based on performance issues, so one pilot might accept the next one refuses to take a certain runway.

So back to our example above:

At Salzburg, due to the terrain in the vicinity and city of Salzburg around the airport, runway 34 is preferred for departures and rwy 16 for landing. So the indicated configuration would be DEP 34, ARR 16.

Transition Altitude/Transition Level

Die Transition Altitude (TA) beträgt in Wien immer 5000 ft. Der Transition Level (TL) ergibt sich in Abhängigkeit zum aktuellen Luftdruck (QNH):

QNH      < 0977: TA + 3000 ft.
QNH 0978 - 1013: TA + 2000 ft.
QNH 1014 - 1050: TA + 1000 ft.
QNH 1051 >     : TA = TL

Zwischen der TA und dem TL befindet sich der Transition Layer, der einen Sicherheitsabstand von mindestens 1000 ft. zwischen dem "unteren Bereich" (Airport Elevation bis A5000 ft.) und dem "oberen Bereich" (Standard Luftdruck 1013 hPa bis Untergrenze TL) gewährleistet. Dadurch werden gefährliche Überschneidungen zwischen dem an- und abfliegenden Verkehr vermieden.

Runway Separation

The runways are one of the most dangerous spots on an airport because aircraft are travelling at high speed with little room to maneuver and most of the time no ability to stop at a reasonable distance. Because of this the general rule is that only one aircaft may be cleared to use a runway at the same time. What this means practically and exceptions from this rule are explained in the following chapters.

Departing Traffic

So now we are at the point where the pilot reaches the Holding Point of his departure runway and reports ready for departure. What are the things you should check before issuing the takeoff clearance?

• Have a look at the flightplan. Take note of the type of aircraft and the Departure Route.
• Check the traffic approaching the runway.

To give him the takeoff clearance the following phrase should be used:

 e.g.: TWR: AUA2CM, wind 320 degerees at 7 knots, Runway 29, cleared for takeoff.
 AUA2CM: Cleared for takeoff Runway 29, AUA2CM

The pilot lines up on the runway, advances the throttle and takes off. When he is well established in climb check he is squawking Mode C and the right Code. Afterwards he is handed off to the next Controller, in this case a radar position:

 TWR: AUA2CM, contact Wien Radar on frequency 128.20, bye bye!
 AUA2CM: Contacting Wien Radar on frequency 128.20, AUA2CM.

The next aircraft reports ready for departure. Again check the points above, but this time we cannot give the takeoff clearance straight away because the preceeding aircraft is still occupying the runway. Now you get to know the first exception to the Runway Seperation rule above. To speed things up you can instruct the next aircraft to line up behind the first one while this one is still in the takeoff roll occupying the runway:

 TWR: AZA639, behind departing Austrian Airbus A319, line-up rwy 29 behind and wait.
 AZA639: behind departing Airbus lining up runway 29 and waiting behind, AZA639.
 Note: The two times behind in this instruction is not a typing error but was implemented to emphasize that part of the clearance.

This type of clearance is called a conditional clearance.

The earliest possible point where you can issue the next takeoff clearance is, when the preceeding aircraft has overflown the opposite runway end or has clearly turned onto either side of it.
However in some cases this could be very close which leads us to the next chapter.

Departure Seperation - Based on Type of Aircraft and departure route

One of the main tasks of air traffic control is to keep aircraft at a safe distance to each other. So imagine the following situation:

Two aircraft are departing right after each other. The first aircraft is a relatively slow Cessna 208 (~around 70 knots in climb), the second one a fast Boeing 767 (140-180 knots on the initial climb). Both follow the same departure route.

Obviously it would not take long until the B767 catches up with the Cessna, a potentially very dangerous situation! You can see, that it is very important to check the flightplan of the aircraft you are about to clear for takeoff.
The minimum radar seperation in the area around an airport is 3 nm or 1000 feet. These are the limits radar stations have to obey. Tower Controllers should aim to achieve the following seperation for departing aircraft following departure routes which share a common part:

Fast followed by slow	3 nm
Matching Types	5 nm
Slow followed by fast	10 nm

In extreme examples like the one above it is often more advisable to coordinate with APP to find another solution. Often this involves clearing the aircraft to a non standard altitude or departure route:

 TWR: DLH2441, after departure maintain runway heading, climb initially to 3000 ft
 DLH2441: After departure maintaining runway heading, climbing to 3000 ft, DLH2441 
 TWR: DLH2441, wind 320 degrees at 9 knots, runway 29, cleared for takeoff
 DLH2441: Cleared for takeoff runway 29, DLH2441

The other main task of ATC is to expedite the flow of traffic. Situation:

You have numerous aircraft departing from the same runway, following different departure routes. Some of them involve immediate right turns other SIDs immediate left turns. There are two holdingpoints available.

It would benificial to use the gaps that arise between the aircraft using similar Departure Routes, so in close coordination with ground you should try to distribute aircraft over the holding points in a way to be able to fill those gaps.

Departure Seperation - Based on Wake Turbulence Category

There are two ways aircraft influence the air around them when passing through it:

Jetwash produced by the engines Turbulence created at the wings and especially at the wingtips

This turbulence can cause severe problems or even loss of control for following aircraft. The wake turbulence categories are based on the Maximum Takeoff weight (MTOW) of the aircraft:

Light Aircraft (L)	< 7 000 kg
Medium Aircraft (M)	7 000 – 136 000 kg
Heavy Aircraft (H)	>136 000 kg

For departing aircraft, 2 minutes separation (3 minutes if the succeeding aircraft departs from an intersection) is applied when an aircraft in wake turbulence category LIGHT or MEDIUM departs behind an aircraft in wake turbulence category HEAVY, or when a LIGHT category aircraft departs behind a MEDIUM category aircraft.
You may issue a take-off clearance to an aircraft that has waived wake turbulence separation, except, if it's a light or medium aircraft departing as follows:

Behind a heavy a/c and takeoff is started from an interception or along the runway in the direction of take-off. Behind a heavy a/c that is taking off or making a low or missed approach in the opposite direction on the same runway. Behind a heavy a/c that is making a low or missed approach in the same direction of the runway.

To point out this hazard to a pilot the following phrase should be used:

 TWR:ESK32C, behind departing heavy B777 line up runway 16 behind and wait, caution wake turbulence.
 ESK32C: behind departing B777 lining up rwy 29 and waiting, ESK32C.

Use of the word takeoff

The word take-off shall only be used in combination with the take-off clearence (cleared for take-off). For other phrases use the word departure (ready for departure – NOT ready for take-off!).

Arriving Traffic

Arriving Aircraft call you when they are established on an approach to a runway. Most of the time this is an ILS Approach but also other kinds are possible.

 MAH224:Linz Tower, MAH224 established ILS Approach rwy 27.

Again you are not allowed to clear more than one aircraft onto the same runway at the same time.

In order to issue a landing clearance preceeding departing traffic must have overflown the opposite runway threshold or clearly turned onto either side of the runway. preceeding landing traffic must have left the runway safety strip with all parts. traffic crossing the runway must have left the runway safety strip with all parts.

If these conditions are met use the following phrase to clear the aircraft:

 TWR:MAH224, Linz Tower, wind 300 degerees at 16 knots, runway 27, cleared to land.
 MAH224:cleared to land runway 27, MAH224.

During periods of high traffic it is likely that you have more than one aircraft approaching the same runway at the same time. Approach has to ensure the minimum radar seperation of 3 nm and additionally increased seperation due to wake turbulence.

 AUA26T:Linz Tower, AUA26T established ILS 27.
 TWR:AUA26T, Linz Tower, continue approach, wind 300 degrees at 16 knots.
 AUA26T:continuing approach, AUA26T.

Meanwhile MAH224 has left the runway.

 TWR:AUA26T wind 310 degrees at 14 knots, runway 27 cleared to land.
 AUA26T:Runway 27, cleared to land, MAH224.

Often it is useful to give pilots additional information, such as traffic information or wind:

CSA276 is following NLY7751 (A320):

 CSA276: Wien Tower, CSA276 established ILS 34.
 TWR:CSA276, Wien Tower, preceeding traffic is a NLY Airbus A320 3,5 nm ahead of you, continue approach runway 34, wind 010 degrees at 4 knots.
 CSA276:We have the airbus in sight continuing approach, CSA276.

AUA81 is approaching runway 16, OE-AGA is on left base runway 16 and there is a rescue helicopter operating in the area around Freudenau.

 AUA81:Wien Tower, AUA81 established ILS 16
 TWR:AUA81, Wien Tower, VFR traffic is on left base rwy 16, continue approach, wind 140 degrees at 7 knots.
 AUA81:continuing approach, AUA81.
 TWR:AUA81, There is an helicopter operating west of the extended centerline, presently at your one o'clock position, 5 nm, 1400 ft.
 AUA81: Thank you, looking out, AUA81.
 AUA81: traffic in sight, AUA81.

To give you an idea how dense traffic can get in real life consider that during peak times and good weather the seperation is reduced to 2,5 nm. This equals to one landing every 75 seconds. However on VATSIM the minimum seperation is 3 nm which already requires good cooperation from all the pilots involved.

Merging Departing and Arriving Traffic

And now to the most fun part of being a Tower Controller. Sometimes you get into the situation that you use the same runway for departures and arrivals. Either your airport has only one runway or weather demand this configuration.

Still the above rule of only one aircraft at the same time applies, however we also use conditional clearances which look very similar to those above in the departing traffic section.

LOWW_TWR: AUA123, Traffic short final RWY 29, C750, report in sight
AUA123: Traffic in sight, AUA123
LOWW_TWR: AUA123, behind landing C750 line up RWY 29 behind and wait
AUA123: Behind landing C750 lining up RWY 29 behdind and waiting, AUA123

To avoid misunderstandings, this time we make sure that the Pilot has the the landing aircraft in sight. You don't have to worry about wake turbulence seperation between landing and departing aircraft since they never cross through each others wake.

To depart an aircraft in front of an approaching aircraft at the time of the departure clearance given the arriving aircraft should not be closer than 4 nm to touchdown. To squeeze a departing aircraft between two arrivals you normally need a minimum of 6 nm between them. It is important for you to check carefully if you have the necessary gap, so have a close look at the distance between the arrivals and their speed. If the second one comes in faster than normal consider this in your calculation. Also you should make sure, that the pilot will be ready for departure when you need him to depart. To check this use the following phrase:

Callsign, are you ready for immediate departure?

Again it is a good idea to give the pilot an idea of the traffic situation around him.

Example:

You are the Tower Controller at Vienna airport. Runway 29 is active for departures and arrivals. One aircraft is on a 5 nm final, one at 12 nm out. Additionally you have two departures waiting at the holding point of ruwnay 29.

TWR:CAL275, are you ready for immediate departure?
CAL275:Affirmitive, ready for immediate departure, CAL275
TWR:Traffic is now at a 4 nm final, wind 300 degrees at 7 knots, runway 29 cleared for immediate takeoff.
CAL275:cleared for immediate takeoff runway 29, CAL275

After the CAL B747 has taken off.

TWR:AUA289, wind 300 degrees at 7 knots, runway 29, cleared to land.
AUA289:Runway 29, cleared to land, AUA289.
TWR:AUA2LT, traffic is an AUA Airbus A320 on a 2 nm final rwy 29, do you have traffic in sight?
AUA2LT:Traffic in sight, AUA2LT.
TWR:AUA2LT, behind landing traffic line up runway 29 behind and wait.
AUA2LT:Behind the landing Airbus, lining up runway 29 behind and waiting, AUA2LT.

AUA289 has vacated the runway.

TWR:AUA2LT, wind 300 degrees at 8 knots, runway 29 cleared for takeoff, landing traffic is now on a 3,5 nm final.
AUA2LT:cleread for takeoff runway 29, AUA2LT.

Merging IFR and VFR Traffic

• Traffic Information
• Visual Identification

- LOWW_TWR: OE-ANX, traffic at your 3 o´clock position, moving right to left, B767, distance 2.5 miles, report mentioned traffic in sight
- OE-ANX: Traffic in sight, OE-ANX
- LOWW_TWR: OE-ANX, behind B767 traffic, enter final RWY **, caution wake turbulence
- OE-ANX: Behind B767, enter final RWY ** behind, caution wake turbulence, OE-ANX

VFR Traffic - Differences

VFR traffic can enter/leave the control zone (CTR) via sector SIERRA (to the south), sector ECHO (to the east) and along the Danube river on the route Klosterneuburg – Freudenau. Maximum altitude in these sectors is 1500ft or according to the VFR charts published online at www.vacc-sag.org.

VFR flights should be guided into downwind, base and final leg for landing.

Used phrases:

OE-AGA, enter control zone via VFR route Klosterneuburg – Freudenau, 1500ft or below,
QNH 1020, Squawk 4604, report XXXX (i.e. Freudenau)
OE-AGA hold (orbit) overhead XXXX (i.e. Freudenau) in XXXX (i.e. 2500ft)

OE-AGA, enter downwind for runway 29, report on downwind
OE-AGA, enter base for runway 29, report on base

VFR Flights get their Clearance from Delivery . After startup, they will contact Tower for taxi. A possible VFR Clearance could be:

OE-AGA, verlassen Sie die Kontrollzone über Sichtflugstrecke Klosterneuburg, 1500 Fuß oder darunter,
QNH 1014, Squawk 4607, Rechtskurve nach dem Abheben so bald als möglich.
OE-AGA, leave controlzone via VFR-route Klosterneuburg, 1500 feet or below, QNH 1014, Squawk 4607,
right turn after departure as soon as possible.

OE-AGA, steigen sie auf 3500 Fuß, melden Sie Donauturm.
OE-AGA, climb 3500 feet, report Donauturm.

Note: Wien Tower/Turm can also be contacted in German.

Information Positions

• Traffic Information
• Weather Information
• Special Requests

LOWW_I_APP (118.520) and LOVV_I_CTR (124.400) are the 2 FIS Positions within Austrian airspace. They are responsible for the VFR Flights. They allocate Squawks, provide Traffic Information and offer Weather Information (worldwide) and coordinate with other controllers requests from pilots.

Special Situations (High Traffic, Slots, ...)

Um zügigen Verkehrsfluß bei starkem Verkehr aufrecht zu erhalten, gilt es dem ankommenden Verkehr höhere Priorität als dem abfliegenden Verkehr zu gewährleisten. Hier sollte vor allem die Vergabe von Slots oder die Errichtung von Abflugintervallen eine große Rolle spielen. Ein Slot ist ein gewisser Zeitraum in dem ein Pilot seinen Start-Up, Taxi und Abflug durchführen sollte. Ein Slot folgt also dem anderen. Abflugintervalle dienen dazu, eine relativ große Anzahl von Abflügen in einem gewissen Zeitraum zwischen zwei Wellen vieler ankommender Flüge abzufertigen. Um genug Freiraum für Abflüge zu haben, ist die Koordination mit den Approach Positionen unumgämglich

You should assign top priority to inbound traffic not to outbound traffic to keep fluent traffic in rush-hour situations. In case of high traffic the use of slots and departure intervals are recommended. A slot is a period of time in which a pilot should be airborne. One slot is followed by another, continuously. Departure intervals are a certain period of time between two high traffic inbound waves. These departure intervals are used to get rid of outbound traffic. Coordination with approach positions to ensure more spacing between inbounds is necessary.

Phrasenzusätze in Situationen mit erhöhtem Verkehrsaufkommen

Um den Piloten eine Anweisung mit Nachdruck bekannt zu machen sollen folgende Phrasen angehängt werden. Dies ist vor allem bei der Runway Sseparation anzuwenden.

Austrian 125, are you ready for immediate departure?

Austrian 125, wind is xxx/xx runway 29 cleared for takeoff, expedite

Für Traffic im Anflug, eine Möglichkeit die Runway schneller frei zu bekommen:

Austrian 125, wind is xxx/xx runway 34 cleared to land, vacate runway as soon as practicable

Um VFR Traffic rasch aus dem Abflugsektor zu bekommen gibt es folgende Möglichkeit:

OE-ABC, wind xxx/xx, runway 29 cleared for takeoff, after departure right turn as soon as practicable

Ressourcen

• VATEUD-TD: Radio Communication
• Wikipedia: Buchstabentafel