Study Guide:Radar

Responsibilities

The responsibilities of a Radar Controller is to maintain the required seperation between aircrafts all the time by using different techniques of sequencing.

Airspace Structure

LOWW is located very close to the Austrian state boundaries with Hungary, Slovakia and the Czech Republik and space within the TMA (Terminal Maneuvering Area) is very limited.
Arrivals are being transferred to LOWW_APP by five independently working ACC sectors (LKAA/ACC Praha, LZBB/ACC Bratislava, LHCC/ACC Budapest, ACC Wien South, ACC Wien North). Therefore final decisions on the arrival sequence are normally made at a distance of approximately 40 NM from touchdown.

LOWW_APP itself operates up to four different sectors, depending on the amount of traffic. Two Upper Radar sectors specify the arrival sequence for the Lower Sectors. Upper Sectors are operated between FL240 and FL110.

The Lower Radar (FL100 and below) will then make final decisions on the arrival sequence by transferring arriving aircraft to the Director, who issues vectors onto the final approach track and sets up a safe flow of landing traffic. Unless otherwise instructed, initial contact on Director frequency (normally 119.800) shall be made by stating the callsign only in order to reduce frequency load.

When the appropriate spacing is assured until touchdown, Director will transfer the arriving aircraft to Tower.

Minimum Radar Separation

A Controller has to make sure that two Aircraft which are under his control never get closer than the minimum radar seperation. If two aircraft get closer than that, this incident is called a conflict.

• The standard Minimum Vertical Seperation is 1000 ft up to FL290 and 2000 ft above that. However Austria is considered RVSM (Reduced Vertical Seperation Minima) airspace so the upper limit of the 1000 ft seperation minimum is raised to FL410. In real life this demands special equipment of the aircraft involved, however on VATSIM all aircraft are considered RVSM capable.
• The Minimum Horizontal Seperation depends on the radar equipment involved. APP Sectors work with a minimum of 3 nm, CTR Sectors use 5 nm.

There are some cases where these minima may be under-run such as visual seperation or formation flights.

MRVA, MSA, MOCA

MRVA (Minimum Radar Vectoring Altitude): The MRVA is defined as the lowest available altitude above Mean Sea Level (MSL) in controlled airspace under consideration of the MSA (Minimum Safe/Sector Altitude) above ground and the airspace structure within a specified area.

MSA (Minimum Safe/Sector Altitude): Minimum Sector Altitude is the minimum altitude that may be used under emergency conditions which will provide a minimum clearance of 1000ft above obstacles and terrain contained within a sector of 25 NM radius centred on a radio navigational aid. MSA can be given as areas between radials from a VOR at the airport.

MOCA (Minimum Obstacle Clearance Altitude): This is the lowest altitude that an aircraft can fly in IMC (Instrument Meteorological Conditions) and still keep safe clearance from terrain and obstacles. MOCA is often lower then MEA (se below). It is only used in emergencies, especially to get below icing.

Structure of Flightplans and Routings

SIDs

SID (Standard Instrument Departure): It is a pre-defined route which aircrafts have to fly to get to their initial airway to follow their desired routing to their destination.

e.g.: Flightplan from LOWW (Wien) to Salzburg (LOWS): SITNI L856 SBG DCT - SITNI is our first waypoint of our routing and let us say for instance that in Vienna Runway 29 is in use. We take a look at our charts and we see that we can plan for a socalled SITNI4C departure route.

SIDs are specified by the local Air Traffic Control. A SID can contain the following navigation aids: R-NAV Waypoints, VORs, NDBs, etc.

STARs

STARs (Standart Terminal Arrival Routes): STARs are pre-defined routes to get an aircraft to the airport.

A STAR falls into three parts namely navigational point, version number and runway (depending on the airport), e.g. GAMLI4W arrival. The point at which the STAR ends is called Initial Approach Fix (IAF). In some cases the STARs continue and end at the Final Approach Fix (FAF), and that means that you as controller don't need to vector the aircraft unless there is other traffic in the way. The only thing you have to do is to instruct the pilot how to descend the aircraft.

There are exceptions of course, where the STARs don't end at the final, but at a navigational point some distance away from the runway. You as a controller must give vectors the last part to the runway. If you for some reason don’t give vectors, the pilot must enter holding at the STAR's ending point (clearance limit).

Types of Instrument Approaches

An instrument approach or instrument approach procedure (IAP) is a type of air navigation that allows pilots to land an aircraft in reduced visibility (Instrument Meteorological Conditions [IMC]) or to reach visual conditions permitting a visual landing.

There are 2 types of approaches:

• Precision Approaches
• Non-Precision Approaches

1.) Precision Approaches

- ILS (Instrument Landing System)
- MLS (Microwave Landing System)
- PAR (Precision Approach Radar)
- GPS (Global Positioning System)
- LAAS (Ground Based Augmentation System [GBAS] for Global Satellite Navigation Systems [GNSS])
- JPALS (Joint Precision Approach and Landing System)
- GCA (Ground Controlled Approach)

2.) Non-Precision Approaches

- Localizer
- VOR
- NDB (with ADF)
- Localizer Type Directional Aid (LDA)
- Simplified Directional Facility (SDF)
- GPS (Global Positioning System)
- TACAN
- Surveillance Radar Approach (SRA) [also known in some countries as ASR approach]
- Visual

Basic Instructions

Vectoring

There are 2 types of vectoring:

• Lateral Vectoring
• Vertical Vectoring

Lateral Vectoring

ABC123, turn left heading 165°
DEF243, turn right heading 300°

When issuing a heading to an aircraft, make sure that you are using a direction ending on 0 (zero) or on 5 (five).

If you provide Radar Vectors to an aircraft then always tell the pilot the reason why you are doing this:

ABC123 turn right heading 080°, radar vectors for ILS approach RWY 11

After vectoring an aircraft you might have to send the aircraft back on its flight planned route:

ABC123, proceed direct to SITNI

It is important to know, that as soon as you take an aircraft of a publsihed route, either by vectoring or by using a direct, you are also responsible for the necessary terrain clearance. To do this always consider the MRVA on the aircrafts path.

Vertical Vectoring

ABC123, climb FL240"
DEF243, descend Altitude 3000 feet, QNH 1016"

As you can see there are 2 types of heights namely Altitude and Flightlevel (FL).

Flightlevel is used for aircraft flying above the Transition Altitude, Transition Level or climbing through and above the Transition Layer (Altimeter in the aircraft is set to Standard Pressure [1013 QNE]).

Altitude is used for aircraft flying below the Transition Altitude or for Aircraft descending through and below the Transition Layer (Altimeter in the aircraft is set to local QNH).

Speed Control

A controller may issue speed instructions within an aircrafts operating limits. There are two possible ways to do this, either by using Indicated Airspeed (FL280 or below) or by specifying a Mach number (FL280 or above).

ABC123, maintain speed 280 knots
DEF456, maintain Mach 0.81

Seperation and Sequencing Techniques

Planning

To effectively use the sequencing techniques explained below we first have to assess the current situation.

Determining current seperation

In VRC and ES their are tools available to determine the seperation between aircraft. One of them is the Seperation Predictor. It is a very comfortable way to determine the point where two aircraft, given a constant speed, will be closest to each other. Furthermore it gives you the minimum distance and the time to go to this point. To constantly survey the distance between to aircraft (or between an aircraft and a point) you can use seperation links (or anchors).

These tools give you an overview over the lateral situation. The vertical situations is a bit more complicated since you have to use a bit of math. If you have two converging aircraft who are not at a constant altitude you need their rate of climb/descend to determine the spacing at their closest point.

APP: AUA265, report rate of climb.
AUA265:rate of climb 2500 feet per minute.

Determining current spacing

Often procedures in a sector include a so called "miles-in-trail" requirement. This means that aircraft flying over the same point and for example have a common destination need to cross the point in a certain distance. Also when working as an approach controller we need to know how close two aircraft will be on approach. How can we determine the current spacing?

First we need to choose a merging point. In a miles in trail requirement this would typically be the handoff point. In the approach area that could be a point somewhere on the approach (e.g. 12 nm final or the point of base turn). Now we can measure the distance of both aircraft to the merging point. If both aircraft have the same speed and are routing direct to the merging point you directly get the spacing at this point. However if differnet speeds are involved things get more complicated. In this case there is no easy and fast way to determine the spacing at the merging point. You will have to use your experience to judge these situations.

Of course you can use this technique to determine the spacing between multiple aircraft.

The concept of positive seperation

Imagine you are the controller in a sector when suddenly the radio communication with your pilots does not work anymore. Take this assumption as the basis of the positive seperation concept. It is policy to always keep aircraft guaranteed safe to each other. This means as soon as you recognize a possible conflict, imeediately resolve it. It's never a good idea to say to yourself "I'll get back to it later" because you might forget it, the voice channel might be blocked and so on.

In the dense approach airspace this is often not easy but it will save you a lot of nerves if you keep converging traffic on different levels!

Resolving conflicts

There are multple ways of resolving a conflict. You can alter the aircrafts flight path, altitude or speed.

Changing an aircrafts altitude to resolve a conflict is relatively easy. Just make sure you achieve the necessary seperation when the two aircraft meet. In the cruise phase you have to keep in mind the aircrafts perfoarmance. Often aircraft can't climb higher due to their weight, so don't be surprised if the pilot rejects the altitude change. ALso have a look at the aircrafts further intentions. For example it is often not a good idea to put an aircraft that has to descend in ahrt time anyway on top of another one. Pilots often prefer to stay at their cruising altitude however in certain situations (e.g. one aircraft overtaking another one) don't hesitate to change the cruise level in accoradance with the pilot.

Speed restrictions for seperation are also possible but mostly you should use them to maintain the present seperation. However in congested airspace where other means of seperation are not possible (e.g. due to terrain) you can also use speeds to achieve a certain seperation. Bear in mind that especially during cruise flight an aircrafts speed margin might not be very large.

Changing an aircrafts flight path to achieve a safe situation is often the best way. Consider the following basic situation:

Two aircraft are flying to the same point at the same altitude. If they keep on flying they will meet each other exactly.

To resolve the conflict you have to change the heading of one of the aircraft. You will soon discover that the best possibility is to turn one aircraft behind the other one.

Speed Control

For efficient sequencing and spacing of arriving aircraft Radar will instruct specific indicated airspeeds to be maintained (speed control). Aircrews are expected to maintain instructed speeds as accurately as possible (+ / - 10knts). In case of unability to maintain instructed speed (weather reasons, operating limitations etc.) ATC has to be informed immediately.

Holding

Useage
The primary use of a holding is delaying aircraft that have arrived over their destination but cannot land yet because of traffic congestion, poor weather, or unavailability of the runway. Several aircraft may fly the same holding pattern at the same time, separated vertically by 1,000 feet or more.

Flying a Hold
Most aircraft have a specific holding speed published by the manufacturer.Maximum holding speeds are established in order to keep aircraft within the protected holding area during their one-minute inbound and outbound legs.

As a rule of thumb the Speed to be flown depends on the altitude or flight level the aircraft is at within the hold as follows:

   * At 6,000' MSL and below: 200 knots
   * From 6,001' to FL 140: 230 knots
   * At and above FL140: 265 knots

• Duration

A Complete hold should take:

   * FL140 and below 4 minutes
   * FL140 and above 5 minutes

• Holding Clearance

A holding clearance issued by ATC includes at least:

- A clearance to the holding fix.
- The direction to hold from the holding fix.
- A specified radial, course, or inbound track.
- If DME is used, the DME distances at which the fix end and outbound end turns are to be
  commenced.
- The altitude or FL to be maintained. 
- The time to expect further clearance or an approach clearance.
- The time to leave the fix in the event of a communications failure.

• Standart Holding Pattern

   * Standard Hold: A hold where all turns are made to the right
   * Non Standard Hold: A hold where all turns are made to the left
   * Holding Course: The course flown on the inbound leg to the holding fix.
   * Inbound Leg: The standard 1 or 1.5 minute leg to the holding fix as Published
   * Holding Fix: This can be a VOR, a VORDME, an Intersection or an NDB
   * Outbound Turn: A standard rate, 180 degrees turn which is begun at the holding Fix.
   * Abeam: The position opposite the holding fix, where the outbound begins.
   * Outbound Leg: This leg is defined by the inbound leg, pilots should adjust the outbound leg
     so that the inbound turn, the other standard 180° turn is completed just as the holding
     course is intercepted.
   * Holding Side: The side of the course where the hold is accomplished.
   * Non Holding Side: The side of the course where you do not want the pilot to be holding

• Non Standart Holding Pattern

A non-standard holding pattern is one in which

- The fix end and outbound end turns are to the left; and/or
- The planned time along the inbound track is other than the standard one-minute or
  one-and-a-half minute leg appropriate for the altitude flown.

• Entry Holding Procedure
  • Direct Entry (aircraft flies directly to the holding fix, and immediately begins the first turn outbound)
  • Parallel Entry (aircraft flies to the holding fix, parallels the inbound course for one minute outbound, and then turns back, flies directly to the fix, and proceeds in the hold from there
  • Teardrop Entry or Offset Entry (aircraft flies to the holding fix, turns into the protected area, flies for one minute, and then turns back inbound, proceeds to the fix and continues from there).

Coordination with adjacent Sectors

The coordination respectively the communication between controllers (and of course pilots) is on of the most important things in aviation.

A clear instruction to the person I want to speak to falls into 4 parts:

- Who am I calling
- What do I want
- How are we going to archieve this (short and clear instructions!) 
- Did the person I called unterstand my instruction properly

VFR Traffic

Flight Information Positions

Flight Information Service (FIS) is an air traffic facility that provides a myriad of services to the pilot, such as pilot briefings, relaying of clearances and broadcasting of weather information. At selected locations, FIS also provides en-route Flight Advisory Services.

Information Positions

• Traffic Information
• Weather Information
• Special Requests

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

Abnormal Situations - Emergencies, Radio Failures

Emergencies

Emergencies are very uncomfortable situations for every controller. Emergencies shall be handeled expeditiously to get them safe down to the ground.

Note: The pilot tells the ATC what his intentions are and what he will do next and not the other way round. ATC keeps all the traffic in the vicinity of the emergency aircraft away to assure that no other aircraft gets injured.

All Weather Operations (AWO)
With Low Visibility Procedures in operation, standard approach runway will be runway 16.
Arrivals will be vectored out of the holdings into the left hand circuit for runway 16. Approximate track distance from the holdings to touchdown shall be calculated with 40 to 70 nautical miles.

Controlling CTR Positions

Area Control Center (ACC) provides ATC to aircraft on the en-route phase of flight. This includes giving information that the pilot needs such as weather and traffic information. The ACC controller has to assure that the seperation is always appropriate regarding to the traffic in the vicinity ( 5 nautical miles lateral, 1000 feet vertical at least ).

ACC is also responsible for all airports where Tower and Approach are not manned. If you are working on the ACC position always remember that this position is a demanding position and requires great knowledge and experience.