- 1 Introduction
- 2 Working Delivery Positions
- 3 Workflow for DEL controllers
- 4 Special Situations (High Traffic, Slots, ...)
This Study Guide has been designed to give you all the information needed to start controlling as a Clearance/Delivery controller on the VATSIM network. It assumes, that you have read and understood the Study Guide:OBS before and have logged in as observer.
Working Delivery Positions
Clearance Delivery is responsible for checking and correcting flightplans of departing aircraft and issue routing clearances to them. This task may sound boring, but is important for upstream controllers: Clearances take time (on the radio) and may block vital commands (like takeoff and landing clearances), and radar stations rely on the checked and cleared values (SIDs and clearance altitudes) for their controlling. If DEL makes mistakes, APP will have trouble.
There are 2 types of flight plans at VATSIM:
- IFR: Any pilot who flies IFR must file a flight plan. It contains the exact routing from departure to arrival, cruise altitude and some more information which controllers need for their job.
- VFR: VFR pilots can file flight plans, but they don't need to. They can simply ask for taxi clearance, take off and continue in uncontrolled airspace.
Flight plans are documents filed by pilots with the local Civil Aviation Authority prior to departure. They generally include basic information such as departure and arrival points, estimated time en route, alternate airports in case of bad weather, type of flight (whether instrument flight rules or visual flight rules), pilot's name and number of people on board.
At VATSIM, flight plans are filed with a VATSIM server. It can be done out of the simulator via the selected VATSIM client (Squawkbox, Xsquawkbox, ...), or via the web.
For IFR flights, flight plans are used by air traffic control to initiate tracking and routing services.
Aircraft routing types used in IFR flight plans are: Airway, Navaid and Direct. A route may be composed of segments of different routing types.
- Airway: Airway routing occurs along pre-defined pathways called Airways. Mostly aircraft are required to fly airways between the departure and destination airports. The rules cover altitude, airspeed, and requirements for entering and leaving the airway (SIDs and STARs). Airways have letters and numbers like "Y868 or "UM125".
- Navaid: Navaid routing occurs between Navaids (short for Navigational Aids) which are not always connected by airways. Navaid flight plans are used for IFR aircraft which don't have a GPS receiver - they can't follow waypoints. Navaid routing is typically only allowed in the continental U.S. If a flight plan specifies Navaid routing between two Navaids which are connected via an airway, the rules for that particular airway must be followed as if the aircraft was flying Airway routing between those two Navaids. Allowable altitudes are covered in Flight Levels.
- Direct: Direct routing occurs when one or both of the route segment endpoints are at a latitude/longitude which is not located at a Navaid.
For VFR flights, their only purpose is to provide needed information should search and rescue operations be required. At VATSIM, a VFR flight plan is handy for controllers, as it shows vital information with the airplane tag on the radar, like the destination.
Flight Plan Syntax
Syntax for IFR flight plans is quite strict, and pilots are encouraged to look up flight plans via online tools (like www.vatroute.net) and paste the code into the routing field. The form is usually <waypoint><route><waypoint><route><destination>, where every waypoint is noted, where the itinerary changes from one route to another (waypoints on the route are omitted). This is necessary, as radar clients (Euroscope) read and interpret this data.
Example: A valid routing from LOWW to EDDM is the following:
SOVIL SITNI DCT BAGSI DCT MATIG DCT AMADI Q113 NAPSA
- SOVIL is the SID exit point (where the aircraft leaves the SID. For more information on the SID, see https://vacc-austria.org/index.php?page=content/chartlist&icao=LOWW).
- SITNI BAGSI MATIG AMADI are enroute waypoints
- Q113 is the route to the STAR entry point for EDDM.
- The "DCT" in-between means that there is no airway between these points: they are "DireCT".
Syntax for VFR flight plans is unregulated and should be self-explanatory (controllers read it themselves). A good code for a VFR flight from LOWW to LOWI might be:
SIERRA SEMMERING MUR MÜRZ LOWZ GERLOS MIKE
- Sector S is the preferred VFR exit route from Vienna TMA
- The rest is a description of a popular route to Innsbruck through scenic mountains
- Mike ist the logical entry into LOWI.
Workflow for DEL controllers
When you log in as DEL, you have to do two things (if waiting pilots jump on you, tell them to stand by until you have done it!):
- Check with the upstream controller (TWR, APP, CTR) for active runways and set active airport and runways in your Euroscope "active runways" dialogue box.
- Check with the upstream controller the active ATIS letter. Set your ATIS dialog box to your airport and the active letter, but don't connect (ATIS is TWR's job). Set this way, Euroscope will show the valid ATIS letter in your METAR list and you don't need to ask every few minutes.
- If there is no Tower or upstream, then create a ATIS.
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 40° 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 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
- Special weather conditions (such as rain)
- Cloud ceiling
- Temperature and Dewpoint
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.
2. Check the flight Plan
At VATSIM, the journey starts with an aircraft popping up at an airport. Initially, the tag (in Euroscope) will show "NOFP", meaning: No flight plan filed so far. Some time later, a destination and more will show up, and that means: The pilot has filed a flight plan. At this point, DEL controller work starts, but Euroscope has done already some work for you. DEL's job is to check and complete it, and to give clearance to the pilot. First, Check, if it is a VFR or IFR flight plan.
For IFR flight plans, ...
- Check, if "From"-Airport is yours and "To"-Airport makes sense. It is unlikely that a C172 will fly to GATB (Timbuktu) without stopovers, as well as a B737 flies VFR to KJFK. If anything looks wrong, then ask the pilot to refile the flight plan.
- Check, if departure runway corresponds to the active runway. If not, then check your runway settings in Euroscope (Pilots never file a particular runway - it's Euroscope setting it for you).
- Check, if cruise altitude is correct: Cruise altitude is stated in flight levels (hundreds of feet): FL280 means 28000 feet (at QNH 1013, to be really correct). For flight levels below FL410, westbound flights have even flight levels, and eastbound flights have odd flight levels. Above FL410, flight levels increase by 20: west is FL430-470-510-550 etc, east is 450-490-530-570 etc (in real, only Concordes request flight levels that high). If the cruise altitude is wrong, ask the pilot for the nearest correct altitudes up or down. If you want, correct the RFL or tell the pilot to file again.
- Check, if there is a valid SID from the active runway to the first waypoint in the flight plan. If not, then look for the cause. It could be an invalid flight plan (a flight plan must contain a waypoint which is the end of a SID - most SIDs have the waypoint in their names: SOVIL*B is the SID leading from LOWW rwy 16 to SOVIL). If the flight plan does not contain any valid waypoint, ask the pilot to refile a correct flight plan. If the flight plan is correct, then you might need to manually select the best SID.
- In some airports (like LOWI), there are more SIDs to the same waypoint, valid for different aircraft (usually, one is "standard" and the other are "special departure" depending on aircraft performance and equipment).
- In most airports, there are special SIDs for aircraft with no FMC (the co-called Non-RNAV departures: they only rely on VOR and NDB).
- Some departures are only for jet or only for prop aircraft.
- Some airports have noise abatement procedures after certain hours in the evening.
Euroscope has already selected the first matching SID in the alphabet. Check, if this SID is applicable to the aircraft type, performance, equipment and time (you might want to check with APP to clarify, which SIDs are correct), and select the best SID.
For VFR flight plans, the task is easier. usually, it contains the destination and a verbal description of the pilot's intention (could be "circuits" or "platzrunde", or "LOWL via Donau").
- Check, if this intention is possible and makes sense (you might check with TWR).
2. Set Squawk and initial clearance altitude
- Set a squawk now. The squawk number space is predefined for each airport and written in the sector file. For normal purposes, automatic squawk allocation in Euroscope works fine. In high traffic situations like Finally Austria, the squawk space runs out quickly, and Euroscope runs mad and shouts "DUPE" (for "duplicate squawk"). Technically, this is not a problem at VATSIM, but annoying. In this case, you have to set squawk codes by hand and start to fill other squawk number spaces, like 2500+. Don't attempt to set a squawk with a number higher than 7 - squawks are octets and don't have 8 and 9 (4707 is good, 4708 does not work).
- Since 2016, real-life technology has changed. The so-called "transponder mode S" ("S" stands for "selective") allows aircraft to be linked with other means than the transponder code. All mode S aircraft receive squawk 1000. This makes Euroscope shout "DUPE" again. To silence this warning, "1000" must be added to the VFR codes ("7000" should be in there too). It's a setting: You do it once and gone.
- Set the initial climb altitude. This differs from airport to airport. LOWW has 5000ft for all SIDs ("A50" in the list), In LOWI, you have to check with APP (it's between FL120 and 160), and Salzburg has different altitudes for different SIDs (look into the SID description).
3. Wait for initial contact
ATC is a service job - you wait for the pilot to come to you, as in real life you don't know if the pilot is on your frequency at all. At some point, the aircraft will call you, ideally with the first (long) phrase. When congested, the short form is used:
LHA123: Wien Delivery, servus. Leipzig Air 123, Info B on board, gate C31, Fokker 70, requesting IFR clearance to München. LHA456: Wien Delivery, Leipzig Air 456 on gate 32 requesting IFR clearance.
Why should the pilot give aircraft and gate information? Because you want to double-triplecheck, if you deal with the correct aircraft: It can happen that you mistake LHA123 with LHA132, but it is unlikely that you mistake a LHA123 B737 to Munich on gate 32 with a LHA132 A320 to Athens on F02.
4. Issue IFR Routing Clearances
First, clear everything which is wrong or unclear in the flight plan, something like ...
DEL: Leipzig Air 123, servus. Sir check your flight plan you fly westbound in that case your flight level must be an even flight level. What do you prefer flight level 310 or 330? LHA123: Flight level 310, Leipzig Air 123.
If you change anything in the flight plan (like RFL=requested flight level), then you must edit his flight plan in Euroscope, and you must tell the pilot:
DEL: LHA123, flight plan amended with new flight level 300.
Then (if you have an amendment, even in one broadcast without readback), issue your clearance:
DEL gives routing clearances to all departing aircraft with the following information:
- aircraft identification
- clearance limit (normally destination aerodrome)
- designator of the assigned SID
- Cleared (initial) flight level
- allocated SSR code (the "squawk")
- any other necessary instructions or information not contained in the SID description, e.g. instructions relating to change of frequency or CTOT (= Calculated take-off time) Slot time (Normally not used on the VATSIM network)
- You may include a confirmation of the ATIS letter.
Normal construction of a routing clearance:
Callsign, cleared to XXXX via XXXXX XX departure, initial climb 5000ft, Squawk 46XX
Austrian 125, cleared to Frankfurt via LUGEM 1C departure, initial climb 5000ft, Squawk 4601, info B is current.
Some Aircraft are not able to follow SIDs for various reasons, most of the time due to missing equipment. In these cases you should issue a so called vectored departure. A vectored departure clearance includes the same components as a normal clearance but instead of the SID you issue instructions to be carried out after departure.
Callsign,cleared to XXXX, after departure RWY XX yyyy, initial climb 5000ft, Squawk 46XX
Austrian 125, cleared to Frankfurt, after departure Runway 29, turn left heading 240 expect vectors to LUGEM, initial climb 5000 ft, Squawk 4601.
You can find the instructions for each Airport within the Study Guide:Airport Details If the pilot responds with a correct readback you should answer with the following phrase:
Callsign, readback correct => Austrian 125, readback correct
Afterwards you either hand the pilot over to GND or wait for his startup request, depending on local procedures. You can do this joint with the readback answer, like:
Austrian 125, readback correct, contact Wien Ground "frequency" 121.60. Bye Bye
Special Situations (High Traffic, Slots, ...)
- Maybe there is no upstream controller. Then you ask the pilot, which runway he wants to use. Then you can clear him.
- Maybe there is a technical problem and TWR cannot connect any ATIS. In this case, you have to check with TWR, which runway is in use, and get the METAR yourself from Euroscope. If the pilot does not find any ATIS, he/she should contact you with the following phrase. Anyway, you should answer him as follows, before any other clearance is given:
LHA123: Wien DEL, Leipzig Air 123, Position E42, requesting airport information. DEL: Leipzig 123, Wien Delivery, servus. Active runway is 34, wind 320 at 10, QNH 1030.
VFR flight plans
The Tower is responsible for VFR Traffic. However, pilots can contact DEL for clearance. You have to enquire with Tower, how to handle that:
- Either direct him to Tower, if Tower wishes to.
- Or ask Tower for the following information and clear the pilot yourself:
- runway to expect (VFR is not bound to the active rwy)
- route to expect
Pilot should call you 10min before Flight for clearance
OE-DLT: C172 at General aviation East, request VFR clearance for Leave controllzone DEL: OE-DLT Active rwy16, cleared to leave via Sector Sierra, 1500ft or below, Squawk 0001. OE-DLT: cleared to leave via Sector Sierra, 1500ft or below, Squawk 0001. DEL: Readback correct, contact Ground 121.600Mhz.
Squawk's like 4601, 4602 and so on are reserved for IFR Flights. For VFR take a Range of 0001 - 0020 for example. Keep in Mind if you have high Traffic and that is in normal time IFR its better you take sqk's like 0002 and so on.
In order to guarantee a safe flow of traffic and to minimize delays in the air so called slots are being used. A slot is a timeframe of five minutes before to ten minutes after the CTOT (Calculated Time Of Takeoff) mentioned before. The aircraft has to depart within this timeframe from its departure airport. On the VATSIM network this system is only used on special occasions.
In real world the are always reserved Slots for the airliners. If they fail the slot time they must wait for a new. The reason is that you won't want too many aircraft in the air with no space to land. Responsible for the Slot Coordianten is the CFMU called "Central Flow Management" Unit in Brussels. The CFMU analyses and calculates traffic demand for 1 day, per week, per month and so on.
Behavior in situations with increased traffic
Sometimes one of your neighboring sectors has to stop accepting traffic. In these cases you should delay an aircrafts start-up clearance.
If possible you should inform the pilot about the expected delay:
Austrian 125, readback correct, expect startup in 10 minutes. "The reason for that is we have an emergency in progress" Austrian 125, startup approved, expect departure in 10 minutes. Thanks for Information
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.