Difference between revisions of "Study Guide:Tower"

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(Moved Delivery and Ground parts to seperate Study Guides.)
(Added an Introduction and made some changes to structure of the Study Guide.)
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'''<span style="color:#ff0000;">This study guide is still work in progress. Stay tuned for further chapters.</span>'''
+
'''<span style="color:#ff0000;">This study guide is still work in progress. Stay tuned for further chapters.</span>'''  
−
==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).
+
== Introduction ==
  
−
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.
+
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 Delivery and Ground Study Guides and that you have some experience controlling on VATSIM.  
  
−
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. 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.
+
== Aircraft and basic Flying Principles  ==
  
−
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.
+
=== Producing Lift  ===
  
−
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.
+
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. 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.
 +
 
 +
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:
  
−
===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:
 
 
{| class="prettytable"
 
{| class="prettytable"
−
|'''Category'''||'''MTOW'''
 
 
|-
 
|-
−
|Light Aircraft (L)||< 7 000 kg
+
| '''Category'''
 +
| '''MTOW'''
 
|-
 
|-
−
|Medium Aircraft (M)||7 000 – 136 000 kg
+
| Light Aircraft (L)  
 +
| &lt; 7 000 kg
 
|-
 
|-
−
|Heavy Aircraft (H)||>136 000 kg
+
| Medium Aircraft (M)
 +
| 7 000 – 136 000 kg
 +
|-
 +
| Heavy Aircraft (H)  
 +
| &gt;136 000 kg
 
|}
 
|}
−
You can find a list of aircrafts in this link [http://www.skybrary.aero/index.php?title=Category:Aircraft&until=D228]
 
−
<br>Weight depicted is MTOW.
 
  
−
====Approach Speed====
+
You can find a list of aircrafts in this link [http://www.skybrary.aero/index.php?title=Category:Aircraft&until=D228] <br>Weight depicted is MTOW.
−
Aircraft are categorized by their reference approach speed (Vref) at maximum landing weight:
+
 
 +
==== Approach Speed ====
 +
 
 +
Aircraft are categorized by their reference approach speed (Vref) at maximum landing weight:  
 +
 
 
{| class="prettytable"
 
{| class="prettytable"
−
|'''Category'''||'''Vref'''
 
 
|-
 
|-
−
|A||<= 90 knots
+
| '''Category'''
 +
| '''Vref'''
 
|-
 
|-
−
|B||91 - 120 knots
+
| A
 +
| &lt;= 90 knots
 
|-
 
|-
−
|C||121 - 140 knots
+
| B
 +
| 91 - 120 knots
 
|-
 
|-
−
|D||141 - 165 knots
+
| C
 +
| 121 - 140 knots
 
|-
 
|-
−
|E||>= 165 knots
+
| D
 +
| 141 - 165 knots
 +
|-
 +
| E  
 +
| &gt;= 165 knots
 
|}
 
|}
  
−
==Working Tower Positions==
+
== 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===
+
Tower is responsible for all movements on the runways as well as for all movements within the control zone. He decides which runways are in use and maintains the ATIS. Tower is also responsible for ground and delivery if they are not online.  
−
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.
+
 
 +
=== Airspace Structure around Major Airports  ===
 +
 
 +
=== ATIS ===
  
−
A ATIS broadcast has to consist of:
+
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.
−
* 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.
+
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
  
−
===Transition Altitude/Transition Level===
+
It is updated every 30 minutes or as soon as significant changes occur.  
−
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.
 
  
−
On the other hand it would not be very practical to use the local pressure while flying at higher altitudes, since terrain is not an issue here and you would have to set a new pressure setting in your altimeter every few minutes.
+
<br>
  
−
To avoid this pilots use the local pressure when departing from an airport until they pass the so called Transition Altitude (TA), where they set the so called standard pressure (QNH 1013 hpa or Altimeter 29.92 inHg). They continue to use this setting until they descend through the Transition Level (TRL) at their destination airport (or an airport on their route), where they set the local pressure again.
+
=== Transition Altitude/Transition Level ===
  
−
In airport charts only TA is given, whereas TRL has to be determined by ATC. Use the following table to calculated your TRL:
+
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.
−
  QNH      < 0977: TA + 3000 ft.
+
 
 +
On the other hand it would not be very practical to use the local pressure while flying at higher altitudes, since terrain is not an issue here and you would have to set a new pressure setting in your altimeter every few minutes.
 +
 
 +
To avoid this pilots use the local pressure when departing from an airport until they pass the so called Transition Altitude (TA), where they set the so called standard pressure (QNH 1013 hpa or Altimeter 29.92 inHg). They continue to use this setting until they descend through the Transition Level (TRL) at their destination airport (or an airport on their route), where they set the local pressure again.
 +
 
 +
In airport charts only TA is given, whereas TRL has to be determined by ATC. Use the following table to calculated your TRL:  
 +
 
 +
  QNH      &lt; 0977: TA + 3000 ft.
 
  QNH 0978 - 1012: TA + 2000 ft.
 
  QNH 0978 - 1012: TA + 2000 ft.
 
  QNH 1013 - 1050: TA + 1000 ft.
 
  QNH 1013 - 1050: TA + 1000 ft.
−
  QNH 1051 >    : TA = TL
+
  QNH 1051 &gt;    &nbsp;: TA = TL
  
−
The room between TA and TRL is called Transition layer. It ensures that the minimum spacing of 1000 ft between aircraft flying in lower part (with local pressure) and the upper part (using Standard pressure).
+
The room between TA and TRL is called Transition layer. It ensures that the minimum spacing of 1000 ft between aircraft flying in lower part (with local pressure) and the upper part (using Standard pressure).  
  
−
===Runway Separation===
+
== Working as a Tower Controller  ==
−
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 '''<span style="color:#ff0000;">only one aircaft may be cleared to use a runway at the same time.</span>''' What this means practically and exceptions from this rule are explained in the following chapters.
 
  
−
=== Departing Traffic ===
+
=== 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 '''<span style="color:#ff0000;">only one aircaft may be cleared to use a runway at the same time.</span>''' 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?  
 
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?  
Line 96: Line 133:
  
 
   e.g.: TWR: AUA2CM, wind 320 degerees at 7 knots, Runway 29, cleared for takeoff.
 
   e.g.: TWR: AUA2CM, wind 320 degerees at 7 knots, Runway 29, cleared for takeoff.
−
  AUA2CM: Cleared for takeoff Runway 29, AUA2CM
+
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:  
 
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!
 
   TWR: AUA2CM, contact Wien Radar on frequency 128.20, bye bye!
−
  AUA2CM: Contacting Wien Radar on frequency 128.20, AUA2CM.
+
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:  
 
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.
 
   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.
+
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''
+
''Note: The two times behind in this instruction is not a typing error but was implemented''
 
  to emphasize that part of the clearance.
 
  to emphasize that part of the clearance.
  
−
This type of clearance is called a conditional clearance. <br> 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.<br> However in some cases this could be very close which leads us to the next chapter but before lets have a look on helicopters.
+
This type of clearance is called a conditional clearance. <br> 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.<br> 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.  
  
−
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.
 
  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.
 
  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.
 
  OEATD: After departure leaving the control zone via Freudenau and Donauturm not above 2500 feet, present position cleared for take-off.
  
−
===Departure Seperation - Based on Type of Aircraft and departure route===
+
=== Departure Seperation ===
−
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:
+
 
 +
==== 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:  
 +
 
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|
+
|  
 
*Two aircraft are departing right after each other.  
 
*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).  
 
*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.
 
*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. <br>
+
 
−
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:
+
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. <br> 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:  
 
<div align="left">
 
<div align="left">
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|Fast followed by slow||3 nm
+
| Fast followed by slow  
 +
| 3 nm
 
|-
 
|-
−
|Matching Types||5 nm
+
| Matching Types  
 +
| 5 nm
 
|-
 
|-
−
|Slow followed by fast||10 nm
+
| Slow followed by fast  
−
|}</div>
+
| 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:
+
|}
 +
</div>  
 +
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
 
   TWR: DLH2441, after departure maintain runway heading, climb initially to 3000 ft
−
  DLH2441: After departure maintaining runway heading, climbing to 3000 ft, DLH2441  
+
DLH2441: After departure maintaining runway heading, climbing to 3000 ft, DLH2441  
−
  TWR: DLH2441, wind 320 degrees at 9 knots, runway 29, cleared for takeoff
+
TWR: DLH2441, wind 320 degrees at 9 knots, runway 29, cleared for takeoff
−
  DLH2441: Cleared for takeoff runway 29, DLH2441
+
DLH2441: Cleared for takeoff runway 29, DLH2441
−
The other main task of ATC is to expedite the flow of traffic. Situation:
+
 
 +
The other main task of ATC is to expedite the flow of traffic. Situation:  
 +
 
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|
+
|  
−
*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.
+
*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.
 
*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===
+
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.
−
There are two ways aircraft influence the air around them when passing through it:
+
 
 +
==== Based on Wake Turbulence Category ====
 +
 
 +
There are two ways aircraft influence the air around them when passing through it:  
 +
 
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|
+
|  
−
*Jetwash produced by the engines
+
*Jetwash produced by the engines  
 
*Turbulence created at the wings and especially at the wingtips
 
*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:
+
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:  
 
<div align="left">
 
<div align="left">
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
| Light Aircraft (L)||< 7 000 kg
+
| Light Aircraft (L)  
 +
| &lt; 7 000 kg
 
|-
 
|-
−
|Medium Aircraft (M)||7 000 – 136 000 kg
+
| Medium Aircraft (M)  
 +
| 7 000 – 136 000 kg
 
|-
 
|-
−
|Heavy Aircraft (H)||>136 000 kg
+
| Heavy Aircraft (H)  
−
|}</div>
+
| &gt;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.<br>
+
|}
−
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:
+
</div>  
 +
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.<br> 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:  
 +
 
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|
+
|  
−
*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 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 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.
 
*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:
+
 
 +
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,
 
   TWR:ESK32C, behind departing heavy B777 line up runway 16 behind and wait,
 
  <u>caution wake turbulence.</u>
 
  <u>caution wake turbulence.</u>
−
  ESK32C: behind departing B777 lining up rwy 29 and waiting, ESK32C.
+
ESK32C: behind departing B777 lining up rwy 29 and waiting, ESK32C.
  
−
=== Arriving Traffic ===
+
=== 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.  
 
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.  
Line 204: Line 266:
  
 
   TWR:MAH224, Linz Tower, wind 300 degerees at 16 knots, runway 27, cleared to land.
 
   TWR:MAH224, Linz Tower, wind 300 degerees at 16 knots, runway 27, cleared to land.
−
  MAH224:cleared to land runway 27, MAH224.
+
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.  
 
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.
 
   AUA26T:Linz Tower, AUA26T established ILS 27.
−
  TWR:AUA26T, Linz Tower, continue approach, wind 300 degrees at 16 knots.
+
TWR:AUA26T, Linz Tower, continue approach, wind 300 degrees at 16 knots.
−
  AUA26T:continuing approach, AUA26T.
+
AUA26T:continuing approach, AUA26T.
  
 
{| class="prettytable"
 
{| class="prettytable"
Line 218: Line 280:
  
 
   TWR:AUA26T wind 310 degrees at 14 knots, runway 27 cleared to land.
 
   TWR:AUA26T wind 310 degrees at 14 knots, runway 27 cleared to land.
−
  AUA26T:Runway 27, cleared to land, MAH224.
+
AUA26T:Runway 27, cleared to land, MAH224.
  
 
Often it is useful to give pilots additional information, such as traffic information or wind:  
 
Often it is useful to give pilots additional information, such as traffic information or wind:  
Line 228: Line 290:
  
 
   CSA276: Wien Tower, CSA276 established ILS 34.
 
   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
+
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.
+
approach runway 34, wind 010 degrees at 4 knots.
−
  CSA276:We have the airbus in sight continuing approach, CSA276.
+
CSA276:We have the airbus in sight continuing approach, CSA276.
  
 
{| class="prettytable"
 
{| class="prettytable"
Line 238: Line 300:
  
 
   AUA81:Wien Tower, AUA81 established ILS 16
 
   AUA81:Wien Tower, AUA81 established ILS 16
−
  TWR:AUA81, Wien Tower, VFR traffic is on left base rwy 16, continue approach, wind 140
+
TWR:AUA81, Wien Tower, VFR traffic is on left base rwy 16, continue approach, wind 140
−
  degrees at 7 knots.
+
degrees at 7 knots.
−
  AUA81:continuing approach, AUA81.
+
AUA81:continuing approach, AUA81.
−
  TWR:AUA81, There is an helicopter operating west of the extended centerline, presently at
+
TWR:AUA81, There is an helicopter operating west of the extended centerline, presently at
−
  your one o'clock position, 5 nm, 1400 ft.
+
your one o'clock position, 5 nm, 1400 ft.
−
  AUA81: Thank you, looking out, AUA81.
+
AUA81: Thank you, looking out, AUA81.
−
  AUA81: traffic in sight, 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.  
  
−
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:
 
  eg. the rescue helicopter from the example above needs to land on your airport:
 
  OEATD: Wien Tower, request landing at the General Aviation Terminal.
 
  OEATD: Wien Tower, request landing at the General Aviation Terminal.
 
  TWR: OEATD, wind 010 degreees 4 knots direct General Aviation Terminal, cleared to land.
 
  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.
+
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  ===
  
−
===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.  
−
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.
 
  
 +
<br> 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.
  
−
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
 
  LOWW_TWR: AUA123, Traffic short final RWY 29, C750, report in sight
 
  AUA123: Traffic in sight, AUA123
 
  AUA123: Traffic in sight, AUA123
 
  LOWW_TWR: AUA123, behind landing C750 line up RWY 29 behind and wait
 
  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
 
  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 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 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:
+
 
 +
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?
 
  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:
+
Again it is a good idea to give the pilot an idea of the traffic situation around him.
 +
 
 +
Example:  
 +
 
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|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.
+
| 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?
 
  TWR:CAL275, are you ready for immediate departure?
 
  CAL275:Affirmitive, ready for immediate departure, CAL275
 
  CAL275:Affirmitive, ready for immediate departure, CAL275
Line 280: Line 347:
 
  immediate takeoff.
 
  immediate takeoff.
 
  CAL275:cleared for immediate takeoff runway 29, CAL275
 
  CAL275:cleared for immediate takeoff runway 29, CAL275
 +
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|After the CAL B747 has taken off.
+
| After the CAL B747 has taken off.
 
|}
 
|}
 +
 
  TWR:AUA289, wind 300 degrees at 7 knots, runway 29, cleared to land.
 
  TWR:AUA289, wind 300 degrees at 7 knots, runway 29, cleared to land.
 
  AUA289:Runway 29, cleared to land, AUA289.
 
  AUA289:Runway 29, cleared to land, AUA289.
Line 290: Line 359:
 
  TWR:AUA2LT, behind landing traffic line up runway 29 behind and wait.
 
  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.
 
  AUA2LT:Behind the landing Airbus, lining up runway 29 behind and waiting, AUA2LT.
 +
 
{| class="prettytable"
 
{| class="prettytable"
 
|-
 
|-
−
|AUA289 has vacated the runway.
+
| AUA289 has vacated the runway.
 
|}
 
|}
 +
 
  TWR:AUA2LT, wind 300 degrees at 8 knots, runway 29 cleared for takeoff, landing traffic is
 
  TWR:AUA2LT, wind 300 degrees at 8 knots, runway 29 cleared for takeoff, landing traffic is
 
  now on a 3,5 nm final.
 
  now on a 3,5 nm final.
 
  AUA2LT:cleread for takeoff runway 29, AUA2LT.
 
  AUA2LT:cleread for takeoff runway 29, AUA2LT.
  
−
==VFR Traffic - Differences==
+
=== VFR 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.
+
 
 +
==== 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''':
  
−
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, 1500ft or below,
 
  TWR:OE-AGA, enter control zone via VFR route Klosterneuburg – Freudenau, 1500ft or below,
 
  QNH 1020, Squawk 4604, report XXXX (i.e. Freudenau), expect runway 29.
 
  QNH 1020, Squawk 4604, report XXXX (i.e. Freudenau), expect runway 29.
 
  TWR:OE-AGA hold (orbit) overhead XXXX (i.e. Freudenau) in XXXX (i.e. 2500ft)
 
  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.<br><br>
+
VFR flights should be guided into downwind, base and final leg for landing.<br><br>  
 +
 
 
  TWR:OE-AGA, enter downwind for runway 29, report on downwind
 
  TWR:OE-AGA, enter downwind for runway 29, report on downwind
 
  TWR:OE-AGA, enter base for runway 29, report on base
 
  TWR:OE-AGA, enter base for runway 29, report on base
  
−
VFR Flights get their Clearance from <u>Tower</u>. After startup, they will contact Ground for taxi, thereafter the Tower will issue the clearance. A possible VFR clearance could be:<br>
+
VFR Flights get their Clearance from <u>Tower</u>. After startup, they will contact Ground for taxi, thereafter the Tower will issue the clearance. A possible VFR clearance could be:<br>  
 +
 
 
  TWR:OE-AGA, verlassen Sie die Kontrollzone über Sichtflugstrecke Klosterneuburg, 1500 Fuß
 
  TWR: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.
 
  oder darunter, QNH 1014, Squawk 4607, Rechtskurve nach dem Abheben so bald als möglich.
Line 320: Line 396:
 
  TWR:OE-AGA, climb 3500 feet, report Donauturm.
 
  TWR:OE-AGA, climb 3500 feet, report Donauturm.
  
−
In the air ATC provides traffic information.
+
In the air ATC provides traffic information.  
 +
 
 
  TWR:OE-AGA, Traffic at your 12 o'clock position, 2100 feet, a PA28 on VFR inbound
 
  TWR:OE-AGA, Traffic at your 12 o'clock position, 2100 feet, a PA28 on VFR inbound
 
  route Klosterneuburg-Freudenau.
 
  route Klosterneuburg-Freudenau.
  
−
When the aircraft leaves the controlzone.
+
When the aircraft leaves the controlzone.  
 +
 
 
  TWR:OE-AGA, set Sqauwk 7000, leaving frequency is approved.
 
  TWR:OE-AGA, set Sqauwk 7000, leaving frequency is approved.
  
−
Wien Tower/Turm can also be contacted in German.
+
Wien Tower/Turm can also be contacted in German.  
 +
 
 +
==== Merging in VFR Traffic  ====
  
−
===Merging in VFR Traffic===
 
 
To manage VFR Traffic efficiently you have to use traffic information and visual seperation.  
 
To manage VFR Traffic efficiently you have to use traffic information and visual seperation.  
 +
 
  TWR: OE-ANX, traffic at your 3 o´clock position, moving right to left, B767, distance 2.5
 
  TWR: OE-ANX, traffic at your 3 o´clock position, moving right to left, B767, distance 2.5
 
  miles, report mentioned traffic in sight
 
  miles, report mentioned traffic in sight
 
  OE-ANX: Traffic in sight, OE-ANX
 
  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:
+
 
 +
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.
 
  TWR:OE-AGA, fly extended right downwind, standby for base.
 
  OE-AGA: Extending right downwind, OE-AGA
 
  OE-AGA: Extending right downwind, OE-AGA
−
To instruct the aircraft to continue it's approach use the following procedure:
+
 
 +
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
 
  TWR: OE-ANX, traffic at your 3 o´clock position, moving right to left, B767, distance 2.5
 
  miles, report mentioned traffic in sight
 
  miles, report mentioned traffic in sight
Line 343: Line 427:
 
  TWR:OE-AGA, behind B767 traffic, enter final RWY 29, caution wake turbulence
 
  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
 
  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:
+
 
 +
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.
 
  TWR: OE-AGA, Make a right three-sixty.
 
  OE-AGA: Making three-sixty to the right.
 
  OE-AGA: Making three-sixty to the right.
 
  TWR: OE-AGA, Orbit left
 
  TWR: OE-AGA, Orbit left
 
  OE-AGA: Orbiting left, OE-AGA
 
  OE-AGA: Orbiting left, OE-AGA
−
The second instructions means, that the pilot should make orbits until further advice.
 
−
===Information Positions===
 
  
−
==Special Situations (High Traffic, Slots, ...)==
+
The second instructions means, that the pilot should make orbits until further advice.
−
===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.
+
==== Information Positions  ====
−
===Additional phrases during periods of high traffic===
+
 
−
In order to expedite the flow of traffic use the following phrases:
+
=== 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 29 cleared for takeoff, expedite
 
  Austrian 125, wind is xxx/xx runway 34 cleared to land, expedite vacating
 
  Austrian 125, wind is xxx/xx runway 34 cleared to land, expedite vacating
Line 361: Line 454:
 
  as soon as practicable
 
  as soon as practicable
  
−
===Opposite runway operations===
+
==== 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.
+
 
 +
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.  
 +
 
 +
== Ressourcen  ==
 +
 
 +
*[http://vateud.net/index.php?option=com_content&view=article&id=77&Itemid=122 VATEUD Training Department]
 +
*[http://de.wikipedia.org/wiki/ICAO-Alphabet Wikipedia: Buchstabentafel]
 +
 
 +
<br>
  
−
== Ressourcen ==
 
−
* [http://vateud.net/index.php?option=com_content&view=article&id=77&Itemid=122 VATEUD Training Department]
 
−
* [http://de.wikipedia.org/wiki/ICAO-Alphabet Wikipedia: Buchstabentafel]
 
−
<br>
 
 
[[Category:Dokumentation]]
 
[[Category:Dokumentation]]

Revision as of 15:40, 2 January 2012

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

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 Delivery and Ground Study Guides and that you have some experience controlling on VATSIM.

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. 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.

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

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

Working Tower Positions

Tower is responsible for all movements on the runways as well as for all movements within the control zone. He decides which runways are in use and maintains the ATIS. Tower is also responsible for ground and delivery if they are not online.

Airspace Structure around Major Airports

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.


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.

On the other hand it would not be very practical to use the local pressure while flying at higher altitudes, since terrain is not an issue here and you would have to set a new pressure setting in your altimeter every few minutes.

To avoid this pilots use the local pressure when departing from an airport until they pass the so called Transition Altitude (TA), where they set the so called standard pressure (QNH 1013 hpa or Altimeter 29.92 inHg). They continue to use this setting until they descend through the Transition Level (TRL) at their destination airport (or an airport on their route), where they set the local pressure again.

In airport charts only TA is given, whereas TRL has to be determined by ATC. Use the following table to calculated your TRL: 

QNH      < 0977: TA + 3000 ft.
QNH 0978 - 1012: TA + 2000 ft.
QNH 1013 - 1050: TA + 1000 ft.
QNH 1051 >     : TA = TL

The room between TA and TRL is called Transition layer. It ensures that the minimum spacing of 1000 ft between aircraft flying in lower part (with local pressure) and the upper part (using Standard pressure).

Working as a Tower Controller

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 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.

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.

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.

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
  1. preceeding departing traffic must have overflown the opposite runway threshold or clearly turned onto either side of the runway.
  2. preceeding landing traffic must have left the runway safety strip with all parts.
  3. 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.

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.

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.

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, 1500ft or below,
QNH 1020, Squawk 4604, 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 their 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 4607, Rechtskurve nach dem Abheben so bald als möglich.
TWR:OE-AGA, leave controlzone via VFR-route Klosterneuburg, 1500 feet or below,
QNH 1014, Squawk 4607,  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 seperation. 

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.

Information Positions

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
as soon as practicable

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.

Ressourcen


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