Study Guide:Tower

This study guide is still work in progress. Stay tuned for further chapters.

Prev: Study Guide:Ground - Overview: Study Guide - Next: Study Guide: Approach

Introduction

This Study Guide is designed to give you all the information you need to become a Tower Controller within VACC Austria. We assume that you have already read the Study Guide:OBS, Study Guide:Delivery and Study Guide:Ground and that you have some experience controlling on VATSIM.

When you reach tower, you will handle aircraft in the air for the first time. So we will discuss some basic principles of flying before actually talking about procedures. Also we'll have to talk about some organisational issues. The fourth chapter of this article will then familiarize you with the procedures you need for controlling tower positions.

Euroscope Visibilty Range for Tower should not exceed 50nm (regarding to Vatsim CoC C12)

Aircraft and basic Flying Principles

Producing Lift

For an aircraft to fly the lift force produced by (mostly) the wings has to outweigh the gravitational force that affects the aircraft.

Basically a wing produces lift by deflecting the air it moves through into one direction. According to Newton's third law of motion the lift is produced into the opposite direction. This lift grows with the speed the aircraft has in relation to the air and with the angle the wing draws with the direction of movement. This angle is called Angle of Attack (AoA).

The principle only works as long as a steady airflow around the wing exists. As soon as the airflow seperates from the wings surface the lift starts to decerease. The AoA at which this occurs is called critical Angle of Attack. It depends on the profile of the wing and it's dimensions but for subsonic aircrafts it typically lies between 8 and 21 degrees.

Think of an level flying aircraft that reduces it speed. In order to compensate the reducing lift the pilot has to raise the nose. However at some point the Angle of Attack will cross the critical angle of Attack and the pilot will find himself in a stall. So the speed of an aircraft is limited on the lower side by the so called stall speed but the aircraft is also limit by aerodynamics in higher range of speed (buffeting). Because the stall speed depends on the profile most aircraft are equipped with devices that alter the profile during flight such as flaps or slats (Approach). In General when an aircraft fly it will produce thrust but at same time it produce drag. So if you fly just horizontal (cruise) you have at the same time Lift=weight and thrust=drag. Drag produce automatic noise and that is the big problem. to prevent this we have different procedures in the approach and a lot of research in aviation to reduce the sound of the aircraft but the main part are the engines.

On approach pilots have to fly in a certain speed range in order to conduct a safe landing. The lower boundary is called landing reference speed and is often a fixed multiple of the stall speed. As a result of this the approach speed also depends on weight an aircraft configuration (Flap/Slat setting). For safety the Approach Vapp is higher than Vref and the difference depends mostly on the weather conditions.

Generally you can say that bigger aircraft also have a bigger approach speed however at some point this rule does not work anymore because the Vref depends largely on the aircrafts weight in relation to it's maximum takeoff weight (MTOW). The speed ranges from 50 knots in a C150 up to 170 knots with a fully loaded 747. However for example it is possible that a light 747 is slower than a fully loaded 737.

Aircraft Categories

The most important ways of categorizing aircraft in aviation are by weight or by approach speed.

Weight Categories

Aircraft are categorized into three weight categories:

Category	MTOW
Light Aircraft (L)	< 7 000 kg
Medium Aircraft (M)	7 000 – 136 000 kg
Heavy Aircraft (H)	>136 000 kg
Super Aircraft (S)	is only one: the A380

You can find a list of aircrafts in this link [1]
Weight depicted is MTOW.

Approach Speed

Aircraft are categorized by their reference approach speed (Vref) at maximum landing weight:

Category	Vref
A	<= 90 knots
B	91 - 120 knots
C	121 - 140 knots
D	141 - 165 knots
E	>= 165 knots

Before you start controlling

Tower is responsible ...

- for all movements on the runways - for all movements within the control zone (see "Airspace Structure" below).

Tower decides which runways are in use and maintains the ATIS. Tower is also responsible for ground and delivery if they are not online or if they are not defined for that particular airport (LOWS has DEL, but no GND; LOWI, LOWG and LOWK have only TWR).

Airspace Structure around Major Airports

Major airports in Austria are surrounded by a so called control zone which is a class D airspace. This means that all aircraft need a clearance to enter this piece of airspace. So either they are cleared to an approach or you need to clear them specifically into the control zone. Details will be discussed in the VFR part later on.

Choosing the active runways

The guiding principle in choosing the active runways is that aircraft prefer to depart and land into the wind.

An airport has one runway named 16/34. The wind is reported as 320 degrees at 14 knots. In 
this case runway 34 is chosen as the active runway.

Look at a more complicated example:

LOWW has two runways: 16/34 and 11/29.
Suppose, wind is 020°, and you see: runway 34 is only 20° off, while 110 is 90° off --> runway 34 is the better choice.

Beware: All major airports have preferential runway configurations which depend on approach configuration, noise abatement and terrain.

Generally, tailwind components of up to five knots are normally accepted.

However due to noise abatement and terrain considerations most airports have some kind of preferential runway system. Bear in mind that it is the pilots decision whether he can accept a certain runway because only he knows the performance of his aircraft.

For details on the preferred runway configurations for a specific airport ask your mentor or look into the airport QRS (quick reference sheets). See in the Resources section at the very bottom for links to them.

ATIS

ATIS stands for Automatic Terminal Information Service and is a usually automatically generated broadcast that contains essential informations for pilots. It is continuously broadcasted on a dedicated frequency. On initial contact with the controller, pilots should already have listened to the ATIS and state the identifying letter.

A ATIS broadcast has to consist of:

Name of the Airport
Identification Letter
Time of Observation
Active Runways
Transition Level
Wind direction and velocity
Visibilities
Special weather conditions (such as rain)
Cloud ceiling
Temperature and Dewpoint
QNH
Trends

It is updated every 30 minutes or as soon as significant changes occur. In practice the ATIS function of Euroscope should be used. You can find the necessary files here. Please consult enclosed readme for information how to use this package.

Transition Altitude/Transition Level

Knowing the altitude you are flying is one of the most important informations you need in order to safely operate an airplane. Aircraft Altimeters use the air pressure around them to determine their actual altitude. In order to get correct readings you have to use the actual local pressure in your area. As a memory hook you can use this: The altimeter needle moves in the same direction you turn the rotary knob to adjust the pressure. If you turn it counterclockwise, the needle also turns counterclockwise and therefor indicates a lower altitude.

As ground pressure changes every hundred miles, aircraft would need to update their settings every few minutes. If ALL aircraft would need to do this, it would be terribly unpractical and dangerous. Guess what happens if one forgets? So the altitude is "sliced":

In lower areas (where terrain is near), aircraft have to update local settings. Most aircraft are there only for takeoff and landing, so no big deal.
In higher areas, aircraft all tune a standard setting (QNH 1013 or 29.92 HG) - this setting may be "wrong", but as all aircraft have the same "wrong" setting, it does not matter.

And where is the altitude where that changes?

For climbing aircraft, it is the Transition Altitude, where they change from local to standard pressure.
For descending aircraft, it is the Transition Level, where they change from standard to local pressure.

Between the two, there is a safety layer (called "Transition Layer") which compensates for the difference between local and standard pressure, which is 1000ft minimum, so the stack is:

Upper airspace: measured in Flight Levels (FL220 = Altitude 22.000ft at standard settings)
Transition Level: the lowest Flight Level
Transition layer (to keep distance)
Transition Altitude (TA): the highest altitude cleared at local pressure settings
Lower airspace, where altitude is given (you write "A5000ft").

As the difference between TA and TL varies with pressure (the lower local pressure, the thinner), the size of the Transition Layer varies (the lower local pressure, the thicker). Use the following table to calculated your TRL:

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

Working as a Tower Controller

Setting the right priorities

The moment you are responsible for more than one aircraft you will have to set priorities in your handling. As a general guideline:

aircraft in the air have top priority - you take care of them first. Reason: They can't stop.
aircraft moving on the ground have next priority. They could bump into each other.
aircraft standing on ground have the least priority.

This also means that you will have to tell pilots to stand by while you attend to other matters. Make sure you keep a list of aircraft you told to stand by so you don't forget to call them back. This also means, that you might have to set priority in services which aircraft in the air need first, like setting up ATIS.

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, 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:

LOWW_TWR: AUA2CM, contact Wien Radar frequency 134.670, bye bye!
AUA2CM: Contacting Wien Radar frequency 134.67, 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 and wait behind.
AZA639: behind departing Airbus lining up runway 29 and waiting behind, AZA639.
Note: you must add another "behind" at the end to make sure the aircraft really waits before lining up!

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 but before lets have a look on helicopters.

Helicopters are sometimes able to start from there current position like a Helipad or a normal stand, if he want to depart from a Runway you can use the normal Phrases for VFR Traffic.

e.g.: OEATD: Wien Tower, OEATD at General Aviation Parking ready for departure.
TWR: OEATD, Wien Tower, after departure leave control zone via Freudenau and Donauturm, 2500 feet or below, Wind 290° 6 Knots, present position cleared for take-off.
OEATD: After departure leaving the control zone via Freudenau and Donauturm not above 2500 feet, present position cleared for take-off.

Take care! Phraseology around the runway is vital

In 1977, at the Tenerife Airport, two 747 Jumbo Jets collided on the runway and burst up in flames, killing more than 500 people. There was a simple cause: misunderstandings in the takeoff phraseology: Tower said "standby for takeoff", the pilot understood "cleared for takeoff". So, there is two iron rules which you should never break as Tower controller:

Use the word "takeoff" only when you clear for takeoff: Say "<aircraft> cleared for takeoff" and nothing else. If you have to say anything else (like that the aircraft can leave in 2 minutes), then use the word "departure".
Use the word "landing" only when you clear for landing: Say "<aircraft> cleared to land" and nothing else. If you have to say anything else (like where to leave the runway after touchdown), use the word "arrival".

Departure Separation

There are several factors to take into consideration when deciding what the minimum separation between succeeding aircraft is. It is the tower controller's responsibility to decide which kind of separation to apply. The following types of separation shall be considered:

Time Based Separation
Radar Separation

CAUTION: Regardless of separation minima to be used, the following rule ALWAYS applies:

A departing aircraft will not normally be permitted to commence take-off until

the preceding departing aircraft has crossed the end of the runway-in-use or
has started a turn or
until all preceding landing aircraft are clear of the runway-in-use.

Note that this paragraph is not about the actual clearance. You may clear an aircraft - considering the minima below - for takeoff before the above conditions are fulfilled, taking into account the time it will take the aircraft, until the actual takeoff can be commenced.

Time Based Separation

To avoid hazards created by the turbulence formed at the wing tips of aicraft (wakes), separation based on time shall be applied between succeeding departing traffic. This is due to the fact, that wakes need a certain time to dissipate.

The actual time to apply depends on the wake turbulence category and thus on the weight of the aircraft:

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

2 Minutes

Provided that succeeding aircraft are using:

the same runway
crossing runways if the projected flight path of the second aircraft will cross the projected flight path of the first aircraft at the same altitude or less than 300 m (1 000 ft) below
parallel runways separated by less than 760m (no applicable in Austria)
parallel runways separated by 760 m (2 500 ft) or more, if the projected flight path of the second aircraft will cross the projected flight path of the first aircraft at the same altitude or less than 300 m (1 000 ft) below (not applicable in Austria)

a minimum separation of 2 minutes applies whenever a

Light or Medium	follows	Heavy
Light	follows	Medium

3 Minutes

Provided that succeeding aircraft are taking off from:

an intermediate part of the same runway (read: intersection)
an intermediate part of a parallel runway separated by less than 760 m (2 500 ft) (not applicable in Austria)

a minimum separation of 3 minutes applies whenever a

Light or Medium	follows	Heavy
Light	follows	Medium

Note: In LOWW the following intersections are, for the purposes of wake vortex, NOT considered to be intersection departures:

Runway	Intersections
11	A11 and A12
29	A1 and A2
16	B1 and B2
34	B11 and B12

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

TWR:DLH32C, wind 180 degrees, 3 knots, runway 16 cleared for takeoff, caution wake turbulence.
DLH32C: cleared for takeoff runway 16, DLH32C.

Radar Separation

For radar equipped TWR stations, which in Austria are basically all controlled TWR stations, departure separation shall be as such, that departing aircraft are entering the approach airspace with radar separation. For LOWW_TWR these minima are for example:

Traffic	Distance	Condition
Departing traffic on different SIDs	3 nm	increasing
Departing traffic on same SIDs	5 nm	increasing

Note: LUGEM and MEDIX count as the same SID

Deciding Which Separation to apply

In order to provide an expeditous flow of traffic for departing traffic, it is imperative for the tower controller to always apply the lowest separation minimum. Since time based separation is always the larger of the minima, it should always be strived to achieve radar separation. In principle, taking the minima above into consideration, radar separation may always be applied when suceeding departing traffic is in the same wake turbulence category or if a heavier aircraft is departing behind a lighter one. Otherwise, time based separation has to be applied.

Tips And Tricks

Try to avoid having multiple aircraft using the same SID depart the same runway right after each other. Throw in a departure with another SID in between to utilize the 3nm radar separation minimum instead of 5.
If possible, have heavier planes depart behind lighter ones, so you avoid having to use time based separation. Of course, take this with a grain of salt, since you can't let the heavier aircraft wait forever.
To achieve radar separation as soon as possible, use initial visual turns if weather permits (VMC). Example:

TWR: AUA117M, after departure visual right turn to SOVIL is approved, wind calm, runway 11 cleared for takeoff.

In this case the aircraft will make a very early right turn, allowing you to have the next aircraft takeoff within seconds, provided it is not lighter than the preceeding.

The ground controller should send aircraft to your frequency early enough during taxi - provided that there are no conflicts on the ground - that you should be able to distribute the aircraft onto the different holding points to your needs. Use the holding points in order to prepare a proper departure sequence that allows you to use the lowest minima possible.

Note: According to the austrian AIP, the pilot shall prepare and be ready to use the following intersections for departure:

Runway	Intersections
11	A10
16	B4
29	A3 (west)
34	B10

For those intersections it is normally not necessary to ask a pilot if he is able - it is his obligation to tell ground upon requesting taxi clearance or latest upon initial contact with the tower controller.

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, AUA26T.

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 continue 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.

Helicopters don't need a Runway for the approach, sometimes they are able to land at their parking position, lets have a look on the Phrases.

eg. the rescue helicopter from the example above needs to land on your airport:
OEATD: Wien Tower, request landing at the General Aviation Terminal.
TWR: OEATD, wind 010 degreees 4 knots direct General Aviation Terminal, cleared to land.

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. You can check this site to see a normal peak time. the capacity from EGLL (London) has reached the 90 percent. Make a replay from one day and you can see further problems in the aviation ....[2]

Issuing "late clearances"

If an aircraft approaches for landing and does not receive landing clearance, then it has to go around - no way to avoid that. For each approach, there is a specific point (MAPt: Missed Approach Point) noted in the charts, where either landing clearance is received or go-around has to be initiated. There is no third option. In airports like LOWW, this is no issue, as the MAPt (when using ILS) is almost the runway threshold. Other airports (like LOWI) have the MAPt some miles out.

So, if traffic gets crowded and some bloke misses the turnoff and taxis along the runway, that can get pretty hard: You know that the arriving aircraft will make it in time for a free runway, but the runway is not free yet, and the arriving aircraft is at the MAPt. What can you do? You issue a "late clearance warning" to allow the aircraft to continue his approach:

TWR: LHA123, expect late clearance.
LHA123: expecting late clearance, LHA123.

This means, that the aircraft may continue approach and expect to be cleared in time. Note: it is not "expect late landing clearance", as "landing" is only to be used when clearing to land!

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 behind 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.

VFR Traffic

Differences to handling of IFR Traffic

The essential collision safety principle guiding the VFR pilot is "see and avoid." Pilots flying under VFR assume responsibility for their separation from all other aircraft and are generally not assigned routes or altitudes by air traffic control. Governing agencies establish specific requirements for VFR flight, consisting of minimum visibility, distance from clouds, and altitude to ensure that aircraft operating under VFR can be seen from a far enough distance to ensure safety.

To guide VFR TRaffic through your airspace you make use of VFR Routes, Sectors and reporting Points. Used phrases:

TWR:OE-AGA, enter control zone via VFR route Klosterneuburg – Freudenau, 2500ft or below,
QNH 1020, Squawk 0001, report XXXX (i.e. Freudenau), expect runway 29.
TWR:OE-AGA hold (orbit) overhead XXXX (i.e. Freudenau) in XXXX (i.e. 2500ft)

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

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

VFR Flights get squawk and basic information (active runway, QNH etc.) from Delivery, the route clearance from Tower. After startup, they will contact Ground for taxi, thereafter the Tower will issue the clearance. A possible VFR clearance could be:

TWR:OE-AGA, verlassen Sie die Kontrollzone über Sichtflugstrecke Klosterneuburg, 1500 Fuß
oder darunter, QNH 1014, Squawk 0001, Rechtskurve nach dem Abheben so bald als möglich.
TWR:OE-AGA, leave controlzone via VFR-route Klosterneuburg, 1500 feet or below,
QNH 1014, Squawk 0001,  right turn after departure as soon as possible.

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

In the air ATC provides traffic information.

TWR:OE-AGA, Traffic at your 12 o'clock position, 2100 feet, a PA28 on VFR inbound
route Klosterneuburg-Freudenau.

When the aircraft leaves the controlzone.

TWR:OE-AGA, set Sqauwk 7000, leaving frequency is approved.

Wien Tower/Turm can also be contacted in German.

Merging in VFR Traffic

To manage VFR Traffic efficiently you have to use traffic information and visual separation.

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

Because of other traffic it might be necessary for the aircraft to remain in the downwind leg until the traffic has passed:

TWR:OE-AGA, fly extended right downwind, standby for base.
OE-AGA: Extending right downwind, OE-AGA

To instruct the aircraft to continue it's approach use the following procedure:

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
TWR:OE-AGA, behind B767 traffic, enter final RWY 29, caution wake turbulence
OE-AGA: Behind B767, enter final RWY 29 behind, caution wake turbulence, OE-ANX

When using an extended downwind you should always consider that the aircrafts speed might be considerably lower than the speed of other aircrafts involved. So if an aircraft has to fly a long way out it might take some time for it to come all the way back, generating a big gap in the arrival sequence. Instead you should aim to keep the plane within the vicinity of the airfield:

TWR: OE-AGA, Make a right three-sixty.
OE-AGA: Making three-sixty to the right.
TWR: OE-AGA, Orbit left
OE-AGA: Orbiting left, OE-AGA

The second instructions means, that the pilot should make orbits until further advice.

Special VFR

Could be used when weather Minimums are below VFR condition.

Weather mimimuns for (S)VFR are follow

- Base Cloud at min. 600ft

- visibility min 1500m

Used phrases:

Verlassen Sie Kontrollzone Sonder-VFR über Donauroute. 
Verlassen Sie Kontrollzone Sonder-VFR. Nach dem Abheben geradeaus steigen auf 600 ft, dann Rechtskurve Steuerkurs 340.  
Verlassen Sie Kontrollzone Sonder-VFR. Nach dem Abheben geradeaus bis zur Ende der Raffinerie. Folgen Sie der Donau. Ausflug Richtung Norden genehmigt.

Leave control zone special-VFR via November
Leave control zone special-VFR. After departure climb on runway heading 600 ft then right turn heading 340
Leave control zone special-VFR. After departure climb on runway heading until end of refinery. turn right heading 360, follow the danube. Leaving control zone to the noth approved.

Night VFR

Night VFR is handled like any other VFR flight. Adherence to special procedures associated with flying VFR after ECET and clearance of terrain is responsibility of the PIC.

Coordination with other ATC Stations

Communication from one controller to another is as important as the communication from controller to pilot. This is especially true during high traffic situations where you might be tempted to concentrate solely on what is happening on your frequency. In these situations don't hesitate to take a call from a fellow controller even if it means that a pilot has to wait before you call him back. Secondly if you know a controller is busy, try to keep your conversation with him concise and avoid chatting in a teamspeak channel next to him.

Within VACC Austria we usually use teamspeak to coordinate with each other. The coordination with other ATC units is mostly done per private chat. Other means of communication are the Intercom functions of Euroscope which would be a very nice feature, however often they only work with certain controllers. The ATC Channel within Euroscope should not be used for individual coordination.

When you come online or go offline you should inform neighboring ATC stations.

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

High traffic situations

During high traffic situations communication with adjacent approach sectors is very important. Especially during single runway operations you might have to ask for increased inbound spacing to be able to fit in departing aircraft.

Additional phrases during periods of high traffic

In order to expedite the flow of traffic use the following phrases:

Austrian 125, wind is xxx/xx runway 29 cleared for takeoff, expedite
Austrian 125, wind is xxx/xx runway 34 cleared to land, expedite vacating
OE-ABC, wind xxx/xx, runway 29 cleared for takeoff, after departure right turn

Opposite runway operations

This is one of the more difficult situtions for a Tower controller. You have to consider the departure route of each aircraft to estimate the required spacing to arriving traffic. Again close coordination with approach is very important.

Resources

If you really want to study hard, then read the relevant sections for DEL in the official radio telephony guide from Austrocontrol.

A really good index (and much more orderly is here at Eurocontrol.