This is the place where aircraft belong – flying. The preparations done by air traffic control and pilots prior to departure aim to enable a safe and smooth journey through the airspace. In general you might say - the better the preparations done prior to departure, the less work for the air traffic controller and pilot en route
Rules regarding separation follow ICAO document 4444, however in VATEUD these rules vary a bit from country to country especially in relation to reduced separation applied at certain busy airports. It is not in the scope of this guide to give all details regarding separation in all countries in VATEUD, but we will focus on the general rules.
Maintaining separation between aircraft is the main task for air traffic control, a task that can be quite difficult and very demanding. Here you’ll find the rules and some tips on how to maintain good separation in the air. Let’s start with the basics – some guidelines and tips that make separation easier.
- Have a clear strategy what you want the pilot to do. Order and contra orders leads to confusion and frustration.
- Consider what implications your instructions have. It's not a good idea to give a pilot clearance to land if you at the moment before gave another pilot instruction to line up on the same runway.
- Talk clearly and not too fast. It may sound “cool” talking fast but it often leads to misunderstanding which makes it slower.
- Use standard phraseology. This reduces the risk of misunderstanding and confusion.
- Listen to the read back carefully as it was the first time the instruction was given. Mistakes happen easily.
- Act immediately if you have a situation with a potential conflict. Don't wait until the conflict is imminent – then it’s usually too late.
- Don't take on more than you can manage. Take a position which you feel you manage and ask for help if you need it.
Since VATSIM is a radar environment, radar separation may be used in general. A rule of thumb for separartion minima is; 1000ft and 5nm. There are of course several exceptions to this rule of thumb, but you’ll manage most situations just fine with it alone.
Minimum vertical separation is:
- 1000ft below FL 410 (RVSM)
- 2000ft above FL410 (RVSM)
You are allowed to climb or descend an aircraft to a level previously occupied by another aircraft provided that vertical separation is maintained. This is done by observing the transponder echo in mode C. You should check with your local vACC for more information regarding vertical separation in the FIR(s) you will be working in. There are three easy guidelines for maintaining the vertical separation as listed below. There are many ways of achieving the same thing, but some ways interfere more with the flight then others.
- Use level change rather than turns to maintain vertical separation en route.
- Use vertical speed adjustments for descending and climbing aircraft that have conflicting paths en route.
- Use turns and speed (IAS) to maintain separation in the approach stage of the flights.
There are several ways of maintaining horizontal separation, but as long as aircraft are within radar coverage and use an altitude reporting transponder the following rules apply. There are other conditions not covered here that applies for example when crossing oceans, or when flying in other areas where no radar coverage is available.The basic rule is that there should be 5 nm horizontal separation in all directions. You can therefore imagine a circle around each aircraft with 2.5 nm radius to reach the 5 nm requirement between two tangential circles. There are situations when the 5 nm separation can be overruled. Three easy guidelines for maintaining the horizontal separation are listed below. There are many ways of achieving the same thing, but some ways interfere more with the flight than others.
- Use turns to maintain horizontal separation for flights en route.
- If on crossing routes, turn the slower aircraft behind the faster.
- Use turn and speed (IAS) to maintain separation in the approach stage of the flights.
This is a typical situation: Two aircraft (AC1 and AC2) are flying on two different but intersecting airways using the same flight level. As a controller you have to consider all flights crossing an intersection point at the same flight level as a possible separation conflict. If you do not do anything then after about 3 to 5 minutes there two aircraft will be converging at the same altitude.Hence ATC needs to take action.If either of the Aircraft is flying at a FL which is incorrect then the first course of action would be to instruct the aircraft at the wrong altitude to climb or descend as wished by the pilot to the correct FL thereby ensuring the correct minimum vertical separation.If both Aircraft however are on a correct, FL then a very often used instruction is to turn one or both of the conflicting aircraft by 15 to 25 degrees away form each other.
ExAir123, turn left by 15 degrees for separation
Once the potential conflict situation has passed the aircraft should be turned back to follow the previously cleared route.
ExAir123, Proceed on Course
ExAir123, Turn right heading…re-cleared direct ABC VOR
ExAir123, Resume Own Navigation direct ABC VOR (could be misunderstood on VATSIM)
The main elements to use for successful conflict separation are:
If 2 Aircraft are approaching head on: Then both aircraft should be turned to the RIGHT
If 2 aircraft are on the same route and FL then: The slower aircraft should be turned to the RIGHT to allow the faster aircraft to overtake the slower aircraft. If on the other hand ATC turns the faster aircraft, both speeds may become equal and then the conflict would be maintained
Standard Instrument Departures (SID's) are routes that have been developed in order to have standard routings for IFR departures at controlled airports. These routes provide terrain clearance and usually follow minimum noise routings. They lead all aircraft via headings, tracks, radials or fixes in the required direction onto the airway system. SID’s are named after their clearance limit and include a number and a letter. The number shows the version of the SID while the letter usually (depending on the FIR or airport) indicates the runway the SID is suitable for as well as whether it is CNAV or RNAV. IFR departures at larger controlled airports are normally always assigned a SID without exception. At most of the larger airports there are dedicated SID’s than can only be used for Jets or for Propeller aircraft as the case may be.ATC may at any time route and aircraft off a SID, either by radar vectors or by instructing the pilot to fly direct to a navaid or a fix.
TWR IB123, Standard Departure Route Cancelled, after take off, climb to FL110 direct ABC VOR
IB123, Copy Direct to ABC VOR and FL110 once airborne.
In addition to the SID or route clearance issued by DEL, clearances issued by TWR/DEP may specify any or all of the following
- Turn after take-off
- Track to follow before turning on to a desired heading
- Initial cleared altitude or flight level
- Time, point, and/or rate at which changes of level are made
Before an outbound aircraft is transferred to area control any local conflicts must have been resolved or co-ordination effected.
Pilots of all aircraft flying instrument departures are required, on first contact, to inform DEP, APP or CTR as appropriate of their call-sign, SID designator (if appropriate, again this is dependant on the rules in force in certain FIR's), current or passing level and their cleared level. If the SID involves a stepped climb profile then the initial altitude/flight level to which the aircraft is climbing will be given.
A route is a description of the path followed by an aircraft when flying between airports. Most commercial flights will travel from one airport to another, but private aircraft, commercial sightseeing tours, and military aircraft may often do a circular or out-and-back trip and land at the same airport from which they took off
Worldwide, there are a large number of named official airways, along which aircraft fly under the direction of ATC. An airway has no physical existence, but can be thought of as a 'motorway' in the sky. On an ordinary motorway, cars use different lanes to avoid collisions, while on an airway, aircraft fly at different flight levels to avoid collisions. Charts showing airways are published by various suppliers and are usually updated once a month coinciding with the AIRAC cycle. AIRAC (Aeronautical Information Regulation and Control) occurs every fourth Thursday when every country publishes their changes, which are usually to airways.
Each airway starts and finishes at a waypoint, and may contain some intermediate waypoints as well. Airways may cross or join at a waypoint, so an aircraft can change from one airway to another at such points. A complete route between airports often uses several airways. Where there is no suitable airway between two waypoints, and using airways would result in a somewhat roundabout route, ATC may allow a direct waypoint to waypoint routing which does not use an airway (in flight plans abbreviated as 'DCT').
Most waypoints are classified as compulsory reporting points, i.e. the pilot (or the onboard flight management system) reports the aircraft position to air traffic control as the aircraft passes a waypoint. There are two main types of waypoints:
- A named waypoint appears on aviation charts with a known latitude and longitude. Such waypoints over land often have an associated radio beacon so that pilots can more easily check where they are. Useful named waypoints are always on one or more airways.
- A geographic waypoint is a temporary position used in a flight plan, usually in an area where there are no named waypoints, e.g. most oceans in the southern hemisphere. Air traffic control requires that geographic waypoints have latitudes and longitudes which are a whole number of degrees.
Note that airways do not connect directly to airports.
- After take-off an aircraft follows a Departure Procedure (SID or Standard Instrument Departure) which defines a pathway from an airport runway to a waypoint on an airway, so that an aircraft can join the airway system in a controlled manner. Most of the climb portion of a flight will take place on the SID.
- Before landing an aircraft follows an Arrival Procedure (STAR or Standard Terminal Arrival Route) which defines a pathway from a waypoint on an airway to an IAF, so that aircraft can leave the airway system in a controlled manner. Much of the descent portion of a flight will take place on a STAR.
Special routes known as ocean tracks are used across some oceans, mainly in the northern hemisphere to increase traffic capacity on busy routes. Unlike ordinary airways which change infrequently, ocean tracks change twice a day, so as to take advantage of any favourable winds. Flights going with the jet stream may be an hour shorter than those going against it. Ocean tracks often start and finish perhaps a hundred miles offshore at named waypoints to which a number of airways connect. Tracks across northern oceans are suitable for east-west or west-east flights, which constitute the bulk of the traffic in these areas.
There are a number of ways of constructing a route. All scenarios using airways use SIDs and STARs for departure and arrival. Any mention of airways might include a very small number of 'direct' segments to allow for situations when there are no convenient airway junctions. In some cases political considerations may influence the choice of route (e.g. aircraft from one country can't overfly some other country).
- Airway(s) from origin to destination. Most flights over land fall into this category.
- Airway(s) from origin to an ocean edge, then an ocean track, then airway(s) from ocean edge to destination. Most flights over northern oceans fall into this category.
- Airway(s) from origin to an ocean edge, then a free-flight area across an ocean, then airway(s) from ocean edge to destination. Most flights over southern oceans fall into this category
- Free-flight area from origin to destination. This is a relatively uncommon situation for commercial flights.
Even in a free-flight area, air traffic control still requires a position report about once an hour. Flight planning systems organise this by inserting geographic waypoints at suitable intervals. For a jet aircraft these intervals are 10 degrees of longitude for east-bound or west-bound flights and 5 degrees of latitude for north-bound or south-bound flights. In free-flight areas commercial aircraft normally follow a least-time-track so as to use as little time and fuel as possible. A great circle route would have the shortest ground distance, but is unlikely to have the shortest air-distance, due to the effect of head or tail winds. A flight planning system may have to do quite a lot of analysis in order to determine a good free-flight route.
Aircraft routing types used in flight planning are: Airway, Navaid and Direct. A route may be composed of segments of different routing type. For example, a route from Chicago to Rome may include Airway routing over the U.S. and Europe, but Direct routing over the Atlantic Ocean.
Airway routing occurs along pre-defined pathways called Airways. Airways can be thought of as three-dimensional highways for aircraft. In most land areas of the world, aircraft are required to fly airways between the departure and destination airports. The rules governing airway routing cover altitude, airspeed, and requirements for entering and leaving the airway Most airways are eight nautical miles wide, and the airway flight levels keep aircraft separated by at least 1000 vertical feet from aircraft on the flight level above and below. Airways usually intersect at Navaids, which designate the allowed points for changing from one airway to another. The airway structure is divided into high and low altitudes.
As by definition an airway is a control area or portion thereof established in the form of a corridor. Airways normally lead from one navigation aid to another, so from a VOR station to another VOR, but also NDB stations are included in the airway system, as well as five letter code Intersections.
Two airways intersecting each other mark a so-called intersection. Airways may be suitable for both directions, called two-way airways, but there are also airways only suitable for one direction. These airways are called one way airways.
Airway Names Every airway has its own name, which normally consists of one or more letters and one or more numbers. Often when calling an airway the phonetic alphabet is not used, instead "colored" designations are used. A - Amber, B - Blue, G -Green, W - White, R - Red and V - Victor are the most common names for airways. The prefix U means, that the airway is only suitable for the upper airspace.
The same route may be followed by airways in different airspace (lower of upper/higher). The difference usually is the U in their designator for the upper/high airways.
Navaid routing occurs between Navaids which are not always connected by airways. Navaid routing is typically only allowed in the continental U.S. If a flight plan specifies Navaid routing between two Navaids which are connected via an airway, the rules for that particular airway must be followed as if the aircraft was flying Airway routing between those two Navaids. Allowable altitudes are covered in Flight Levels.
Direct routing occurs when one or both of the route segment endpoints are at a latitude/longitude which is not located at an airway. Some flight planning organizations specify that checkpoints generated for a Direct route be a limited distance apart, or limited by time to fly between the checkpoints (i.e., Direct checkpoints could be farther apart for a fast aircraft than for a slow one).
Since the European airspace was unified, the airway system was also standardized to become continuous between the European states.The enroute charts can usually be found in the official webs of aeronautical administrations under the AIP Section and ENR tab. There you will find the charts under tab ENR 6 and the detailed information on direction of flight and flight levels under tab ENR 3 if not depicted in the chart itself.
The edition of enroute charts may vary depending on the European state and the symbols may also vary accordingly. You will always find a legend where everything is explained.
The one-way airways usually have an arrowed box in the route pointing towards the correct direction with its designator in that box and two-way airways usually have their designator in a square box without arrow.
The direction of flight is usually depicted together with the correct flight level (even or odd). The direction of flight is usually depicted as a thin arrow or a symbol. The flight levels may be depicted with the letter E for EVEN flight levels or an O for the ODD ones. Other editors use A or B to indicate the correct flight levels. In any case, the legend of the chart provides all information.In some cases, like for the Spanish enroute charts, no indications on directions or flight levels are indicated. In such situation, the ENR 3 documents (ATS routes) give the direction and levels of flight for any airway.
At (http://www.eurocontrol.int/ead/public/subsite_homepage/homepage.html) you can access the public area where charts (aerodrome and enroute) for the European states can be found and also for many other non EU countries. You should access the BASIC EAD site and register for free to gain full access.
Before the enroute charts were available for the simulation community, it was usual to follow the “semi-circular” rule for flight levels. This rule said to use EVEN flight levels for westbound flights and ODD flight levels for eastbound flights. This rule is partially used in the USA but should not be used in Europe as long as enroute charts are available.
STAR’s or Standard Terminal Arrival Routes exist to lead all IFR traffic from the airway system to the IAFs (Initial Approach Fixes) of an airport. They are named after the waypoint they are starting with and also include a number showing the version the STAR is valid for as well as whether it is CNAV or RNAV.For all instrument approaches the following information is to be passed to the pilot unless it has already been passed and acknowledged
- Type of Approach
- Runway to which the approach will be made
- Runway for landing if different
QNH should only be passed to the pilot by ATC (normally APP) once the Pilot has been instructed to descend below the Transition Level
The initial assigned level to arriving IFR aircraft should normally not be below the appropriate minimum sector altitude or, if this is not known, the highest minimum sector altitude. If a pilot is flying at, or has requested, a lower level then a reminder of the highest sector altitude should be issued.
At aerodromes where radar procedures are in force CTR will negotiate with APP a cleared level for arriving IFR flights and then subsequently transfer control and communications simultaneously when clear of other CTR traffic. Radar procedures are assumed to be in force at all aerodromes in VATSIM. At busy airports, when holding procedures are in effect, coordination and transfer of control will be effected in accordance with local agreements.
CTR will clear arriving aircraft to the holding facility if the flight is remaining within its airspace and will give instructions to hold if necessary unless prior agreement has been reached between CTR and APP that the aircraft will not be required to hold in which case the aircraft may be placed on a radar heading towards the initial approach area by CTR.
APP may issue any instructions to an aircraft released to it by CTR, however such aircraft should not be instructed to climb above, or stop descending above the level at the holding facility agreed with CTR without prior coordination with CTR.
If an arriving aircraft makes its first call to APP not having been handed over from a CTR unit (can happen in VATSIM that no CTR controller is on line in the FIR) the following information shall be passed as soon as practicable
- Runway in use
- Current meteorological information, which should include the surface wind direction and current visibility
- Aerodrome QNH
Even if visual reference to the ground is established before completion of the approach procedure, pilots will normally complete the whole procedure. At the pilot's request however, the flight may be cleared to break off the instrument procedure and carry out a visual approach.
To expedite traffic at any time, an IFR flight may be authorized to execute a visual approach if the pilot reports that he has the airfield or preceding traffic in sight and can maintain visual reference to the surface.
Standard Separation shall be effected between such aircraft and other IFR and/or SVFR aircraft notwithstanding that the flight is now operating by visual reference to the surface.
Where radar vectoring is in use, then the ATC shall vector the aircraft in such a way to achieve the minimum overall delay to arriving flights. On occasions this may necessitate altering the arrival order of inbound aircraft
The Approach Controller main task is to separate arriving traffic in order to maintain an optimum flow of traffic into any given field by means of giving course, altitude and if needed speed restriction instructions to pilots.
In VATSIM, pilots most often request and ATCs most often give ILS approaches regardless of time, weather conditions, or type of aircraft. There are however more types of approach types than only ILS.
So, the aircrafts are now well on their way in to the field, they have followed the STAR and the Approach or Director Controller now has to vector the aircraft in towards the field for a safe and orderly handoff to the Tower Controller for a safe landing.
The most challenging and work intensive part of any flight is the landing phase, as the saying goes a good landing is a controlled crash at the best of times. But before an aircraft actually lands it has to Approach a field.
Approaches are classified as either precision or non-precision, depending on the accuracy and capabilities of the navigational aids (navaids) used. Precision approaches utilize both lateral (course) and vertical (glide-slope) information. Non-precision approaches provide course or glide-slope information only.
An instrument approach or instrument approach procedure (IAP) is a type of air navigation that allows pilots to land an aircraft in reduced visibility (known as instrument meteorological conditions or IMC), or to reach visual conditions permitting a normal landing.
Charts depicting instrument approach procedures are called Terminal Procedures, but are commonly referred to by pilots as "approach plates." These documents graphically depict the specific procedure to be followed by a pilot for a particular type of approach to a given runway. They depict prescribed altitudes and headings to be flown, as well as obstacles, terrain, and potentially conflicting airspace. In addition, they also list missed approach procedures and commonly-used radio frequencies.
The whole of the approach is defined and published in this way so that aircraft can land if they suffer from radio failure; it also allows instrument approaches to be made procedurally at airports where air traffic control does not use radar or in the case of radar failure.
5.5.3. Instrument Approaches [S+]
This kind of approach being the most common in VATSIM in general is made up of 5 distinct phases (segments) of flight:
- Arrival: where the pilot navigates to the Initial Approach Fix (IAF)
- Initial Approach: the phase of flight after the IAF, where the pilot commences the navigation of the aircraft to the Final Approach Fix (FAF), a position aligned with the runway, from where a safe controlled descent back towards the airport can be initiated.
- Intermediate Approach segment: an additional phase in more complex approaches that may be required to navigate to the FAF. This segment begins at the Intermediate Fix (IF)
- Final Approach: between 4 and 12 nm’s (Generally 10 miles final) of straight flight descending at a set rate (usually an angle of between 2.5 and 6 degrees).
- Missed Approach: an optional phase; should the required visual reference for landing or landing clearance not have been obtained at the end of the final approach, this allows the pilot to climb the aircraft to a safe level and navigate to a position to hold and from where another approach can be commenced.
ATC may replace some or all (with the exception of the FAF) of these phases of the approach with radar vectors to the final approach, to allow traffic levels to be increased over those of which a fully procedural approach is capable. It is very common for ATC to vector aircraft to the final approach aid, e.g. the ILS, which is then used for the final approach.If Traffic allows it or indeed if it becomes necessary then ATC can issue specific constraints on the approaching traffic:
ExAir123 Make Short Approach Runway 12
ExAir123 Make Long Approach Runway 07
ExAir123 Extend Downwind Leg Runway 10 due to traffic on final
There are quite a few different systems in use, the main thing they all have in common is the Decision Height which is a specified height in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been acquired. This altitude specified allows the pilot sufficient time to safely re-configure the aircraft to climb and execute the missed approach procedures while avoiding terrain and obstacles.
The following is a brief explanation of the different ILS approach types: some you may have heard about, some not, some are in use others in development. The certain thing is that technology and above all GPS will have a major impact in years to come.
Precision Approaches provides pilots both horizontal (Localizer) and vertical (Glide Path) information and is conducted by the use of an ILS (Instrument Landing System), a MLS (Microwave Landing System) a PAR (Precision Approach Radar) or any of the other rather ”exotic” systems described bellow. ILS - Instrument Landing System (see Section 5.7 bellow)
MLS - Microwave Landing System The Microwave Landing System (MLS) is an all-weather, precision landing system originally intended to replace or supplement the Instrument Landing System (ILS). MLS has a number of operational advantages, including a wide selection of channels to avoid interference with other nearby airports, excellent performance in all weather, and a small "footprint" at the airports.
Although some MLS systems became operational in the 1990s, the widespread deployment initially envisioned by its designers never came to be. GPS-based systems, notably WAAS, allowed the same level of positioning detail with no equipment needed at the airport. GPS/WAAS dramatically lowers the cost of implementing precision landing approaches, and since its introduction most existing MLS systems in North America have been turned off.
MLS continues to be of some interest in Europe, where concerns over the availability of GPS continue to be an issue. A widespread installation in England is currently underway, which included installing MLS receivers on most British Airways aircraft, but the continued deployment of the system is in doubt.
PAR - Precision Approach Radar (Military) is a type of radar guidance system designed to provide lateral and vertical guidance to a pilot for landing up to the missed approach point. Controllers monitoring the PAR displays observe each aircraft's position and issue instructions to the pilot that keep the aircraft on course. It is similar to an Instrument Landing System (ILS) but requires control instructions. Precision Approach Radars are heavily used by Military Air Traffic Control Facilities. Most of these facilities use the FPN-63 Precision Approach Radar. This Radar can provide precision guidance to a distance of 20 miles in normal mode and 15 miles in MTI mode.
GPS (with vertical navigation via WAAS or EGNOS) The Global Positioning System, usually called GPS, is the only fully-functional satellite navigation system. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio to GPS receivers, allowing them to accurately determine their location (longitude, latitude, and altitude) in any weather, day or night, anywhere on Earth. The European Geostationary Navigation Overlay Service (EGNOS) is a satellite navigation system under development by the European Space Agency, the European Commission and EUROCONTROL. It is intended to supplement the GPS systems by reporting on the reliability and accuracy of the signals. According to specifications, horizontal position accuracy should be better than 7 meter. In practice, the horizontal position accuracy is at the meter level. It will consist of three geostationary satellites and a network of ground stations and was intended to be operational in June 2005, but due to delays the date has been pushed back to the first quarter of 2006. It is planned as a precursor to the Galileo positioning system. A similar service is provided in America by the Wide Area Augmentation System (WAAS) system
LAAS - Ground Based Augmentation System (GBAS) for Global Satellite Navigation Systems (GNSS) is an all-weather landing system based on real-time differential correction of the GPS signal. Local reference receivers send data to a central location at the airport. This data is used to formulate a correction message, which is then transmitted to users via a VHF data link. A receiver on an aircraft uses this information to correct GPS signals, which then provides a standard ILS-style display to use while flying a precision approach.
JPALS - Joint Precision Approach and Landing System (military) is a all-weather landing system based on real-time differential correction of the GPS signal, augmented with a local area correction message, and transmitted to the user via secure means. The onboard receiver compares the current GPS-derived position with the local correction signal, deriving a highly-accurate three-dimensional position capable of being used for all-weather approaches via an ILS-style display. While JPALS is similar to LAAS but intended primarily for use by the military, some elements of JPALS may eventually see their way into civilian use to help protect high-value civilian operations against unauthorized signal alteration.
Further Precision aids are the PAPI or precision approach path indicator which is a system consisting of four light units situated on the left side of the runway (or on both sides of the runway, in the case of a military field) in the form of a wing bar.The aircraft is on slope if the two units nearest the runway show red and the two units furthest from the runway show white, too high if all units show white, and too low if all units show red.
Bear in mind though that VATSIM and Flight Simulator constraints only make it possible to simulate the ILS precision approach.
These kind of approaches have a minimum descent altitude in common, the (MDA) this is the equivalent of the DA/DH for non-precision approaches, however there are some significant differences. It is the level below which a pilot making such an approach must not descend his or her aircraft unless the required visual reference to continue the approach has been established. The significant difference compared to a DA is that a missed approach need not be initiated once the aircraft has descended to this level: in non-precision approaches the point at which a missed approach must be initiated is defined as a separate point known as the missed approach point (MAP). Thus, in non-precision approaches, a pilot may descend to the minimum descent altitude and, having not gained visual reference, fly level at the MDA attempting to gain visual reference until the MAP is reached, at which point a missed approach must be initiated if the required visual reference to continue the approach has not been obtained.
If a runway has both precision and non-precision approaches defined, the MDA of the non-precision approach is almost always greater than the DA of the precision approach, due to the lack of vertical guidance of the non-precision approach: the actual difference will also depend on the accuracy of the navaid upon which the approach is based, with ADF approaches tending to have the highest MDAs.
Typical Non Precision approaches are those conducted with the aid of a VOR, VORDME a NDB, and of course a visual approach. Where by the obstacle assessment in the final segment is based on minimum descent altitude (MDA). The Plane is then flown in level flight at the MDA whilst the pilot attempts a visual identification of the airfield. If the runway or airport is not visible by the time the plane reaches the Missed Approach Point (MAP) then the approach has to be aborted and another attempt made from the beginning
When performing a non-precision approach, the pilot shall be given a position report together with handoff to Tower.
ExAir123, you are 15 miles from touchdown, a bit right of extended centerline. Contact Tower on….
ExAir123, you are 10 miles from touchdown, about half a mile east of extended centerline, contact Tower on ………
An approach where the track of the instrument approach procedure is aligned to within 15 degrees of the runway heading, therefore allowing aircraft to land easily after making the approach.
ExAir123 Cleared for the approach, proceed direct to the FAF to cross at 3000 feet report Established
EXAir123 Make Straight-In Approach for Runway 25R turn to heading 240, cleared for the approach
A circling approach is an instrument approach to a runway which is not aligned to within 15 degrees of the track of the instrument approach procedure, and therefore requires some visual maneuvering of the aircraft in the vicinity of the airport after the instrument portion of the approach is completed for the aircraft to become aligned with the runway to land.
ATC must ensure the pilot does not descend below the Minimum Descent Altitude until in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers. The following basic rules apply:
- The pilot will maneuver the shortest path to the base or downwind leg, as appropriate, considering existing weather conditions. There is no restriction from passing over the airport or other runways.
- Circling maneuvers may be made while VFR or IFR traffic is in progress at the airport. Standard left turns or specific instruction from the controller for maneuverings must be considered when circling to land.
- At airports without a control tower, it may be desirable to fly over the airport to observe wind and turn indicators and other traffic which may be on the runway or flying in the vicinity of the airport.
ExAir123 Make Circling Approach, left turn to Runway 19
ExAir123 Cleared for ILS approach runway 14 followed by visual circle to land runway 32
On an ARC approach the pilot maintains a certain predetermined distance from a Navaid. This means that the pilot will fly an arc (semi-circle) around the Navaid.
When the pilot is approaching the FAF he turns towards the centerline and continues the final approach using the appropriate kind of final approach as available at the airfield.
ExAir123 Cleared for ARC Approach Runway 36 maintain 15 DME, ABC VOR report final
An IFR flight may be cleared to execute a visual approach provided that the pilot can maintain visual reference to the terrain and the visual approach is coordinated with aerodrome control. Separation has to be maintained (during daytime, and it is possible to delegate the obligation to maintain separation to the Pilot). The weather must be good enough and the reported ceiling has to be at or above the initial approach altitude.
The clearance for a visual approach during radar vectors shall only be issued after the pilot has reported the aerodrome “field in sight” or the preceding aircraft in sight.
The visual approach is the shortest and most efficient approach considering fuel consumption and time
ExAir123, request vectors for visual approach.
ExAir123, roger, field at your 4 o'clock, turn left heading 160 degrees, report field in sight.
ExAir123 field in sight.
ExAir123, roger, cleared left (right) hand visual (or Straight In) visual runway 33 contact Tower.
A full procedure approach is performed by first flying towards a navaid at the airfield called the initial approach fix.
The pilot then navigates according to the approach plate procedure and will make all the required turns without any further ATC instructions and will report once established on final approach.
This is also the kind of procedure that would be used in the event of a radio communication failure as described in chapter 8.
A full procedure approach is something which can come in quite handy for Center Controllers being responsible for multiple fields on their own, which due to traffic concentration in a particular field are unable to give accurate vectors at secondary fields.
Example: CTR controller for Madrid has traffic inbound also in Malaga
ExAir123 Cleared inbound LEMG runway 13 full procedure Approach report on final.
An Aerodrome Traffic Circuit is a standard path followed by aircraft when taking off or landing.
At an airport, the pattern also known as a circuit is a conventional standard path for coordinating air traffic. It differs from so-called "straight in approaches" and "direct climb outs" in that aircraft using a traffic pattern remain in close proximity to the airport. Patterns are usually employed at small general aviation airfields and military airbases. Most large airports avoid the system, unless there is GA activity as well as commercial flights. However, a pattern of sorts is used at airports in some cases, such as when an aircraft is required to go around.
The use of a pattern at airfields is for air safety. Rather than have aircraft flying around the field in a haphazard fashion, by using a pattern pilots will know from where to expect other air traffic, and be able to see it and avoid it. GA pilots flying under VFR will not be separated by air traffic control, and so the pattern is a vital way to keep things in order.
All aircraft prefer to take off or land facing into the wind. This has the effect of reducing their speed over ground and hence reducing the distance required to perform either maneuver, but mainly to keep lift with reduced engine power.
Many airfields have runways facing a variety of directions. A common scenario is to have two runways arranged at or close to 90 degrees to one another, so that aircraft can always find a suitable runway. Almost all runways are reversible, and aircraft use whichever runway in whichever direction is best suited to the wind. In light and variable wind conditions, the direction of the runway in use might change several times during the day.
However, it is not always necessary or possible to use the runway that is best aligned with the wind. Depending on the length of the runway headwinds up to 10kts can be accepted. It's for example better to take a runway with CAT II ILS with a bit of headwind in case of low visibility than to take the runway that has no headwind but just CAT I ILS.
Traffic patterns can be defined as left-hand or right-hand, according to the turn direction in the pattern. They are usually left-hand because most small airplanes are piloted from the left seat (or the senior pilot or pilot in command sits in the left seat), and so the pilot has better visibility out the left window. Right-hand patterns will be set up for parallel runways, for noise abatement or because of ground features (such as terrain, towers, etc.). Helicopters are encouraged, but not required, to use an opposite pattern from fixed wing traffic due to their slower speed and greater maneuverability. Because the active runway is chosen to meet the wind at the nearest angle (upwind), the circuit orientation also depends on wind direction. Patterns are typically rectangular in basic shape, and include the runway along one long side of the rectangle. Each leg of the pattern has a particular name:
- The section extending from the runway ahead is called the climb out or upwind leg.
- The first short side is called the crosswind leg.
- The long side parallel to the runway but flown in the opposite direction is called the downwind leg.
- The short side ahead of the runway is called the base leg.
- The section from the end of base leg to the start of the runway is called the final approach or finals.
- The area of the airfield adjacent to the runway but opposite the circuit is known as the dead side.
While many airfields operate a completely standard pattern, in other cases it will be modified according to need. For example, military airfields often dispense with the crosswind and base legs, but rather fly these as circular arcs directly joining the upwind and downwind sections.
An aircraft taking off will usually be expected to follow the circuit in use, and one arriving at the field to land will be expected to join the circuit in an orderly fashion before landing. This is often accomplished using an overhead join or by entering the downwind leg at a 45 degree angle abeam midfield traffic permitting. Aircraft are expected to join and leave the circuit in an orderly and safe manner. Sometimes this will be at the discretion of the pilot, while at other times the pilot will be directed by air traffic control.
OY-DH Join Downwind for runway 15, winds 140 at 10kts, number 1 for landing
There is also a procedure known as an orbit which is where an aircraft flies a 360 loop either clockwise or anticlockwise. This is usually for separation with other circuit traffic, and can be the result of a controller’s instruction, else the pilot will report:
OY-DH making 1 left-hand orbit, will advise complete
This is a conventional method for an aircraft to integrate with the air traffic pattern near an airfield, join the circuit and land.
Aircraft may arrive at the landing site from any direction, so a safe means of integrating into existing traffic and aligning with the runway is required. The overhead join is the standard method used predominantly in the UK but also in a number of other European countries, at smaller airports by general aviation aircraft flying under the Visual Flight Rules.
Prior to arrival, the pilot will liaise with air traffic control over the radio to establish the runway in use, the circuit height and direction (left or right hand), and the QFE of the field.
This information is verified by the approaching pilot by over flying the airfield and ascertaining the wind direction (from looking at a wind sock). This involves piloting the aircraft so that it is flying against the direction of the runway but usually at 2000 feet above ground level (AGL). The pilot flies over the runway, looking out for other traffic in the circuit, and descends to circuit height (usually 1000 feet AGL) on the dead side (opposite that of the circuit). He can then safely position himself in the circuit behind or between other traffic without conflicting, and land in turn.
In cases where two or more parallel runways are in operation concurrently, the aircraft operating on the outermost runways are required to perform their patterns in a direction which will not conflict with the other runways. Thus, one runway may be operating with a left-hand pattern direction, and the other one will be operating with a right-hand pattern direction. This allows aircraft to maintain maximum separation during their patterns; however it is important that the aircraft do not stray past the centerline of the runway when joining the final leg, so as to avoid potential collisions. If 3 or more parallel runways exist, then the middle runway(s) can, for obvious reasons, only be used when either a straight in approach is used or when the aircraft joins the pattern from a very wide base leg.
An airfield will define a circuit height or pattern altitude, that is, a nominal altitude above the field (QFE) at which pilots are required to fly while in the circuit. Unless otherwise specified, the standard pattern height is 1000 ft above ground level, although many small airports operate with a pattern height of 800 feet above ground level. Helicopters usually fly their pattern at 500 feet above ground level.
Helicopters also prefer to land facing the wind and are often asked to fly a pattern on arrival or departure. Many airfields operate a special pattern for helicopters to take account of their low airspeed. This is usually a mirror image of the fixed-wing pattern, and often at a slightly lower standard height above surface level; as noted above this altitude is usually 500 feet above ground level.
The most common Approach used in VATSIM. As ATC you will usually vector aircraft in on an intercept course between 20 and 30 degrees offset from the runway heading in order for the aircraft to be established on the localizer in general 10 miles from the touch down zone.
ExAir123, turn right heading 190, cleared ILS runway 22L.
5.7.1. Course and Glide Slope [S+]
The Instrument Landing System (ILS) is a landing navigation system that is used only within a short distance from the airport. Its purpose is to help the pilot land the airplane. Historically is was generally used only when visibility is limited and the pilot cannot see the airport and runway. Now a days it is used in both fiar and bad weather, and most commercial aircraft use ILS for the vast majority of landings.
The system, which is ground-based, broadcasts very precise directional signals. These signals provide a lateral and vertical path to the runway to a distance of 18 nautical miles from the runway.
Equipment on board the plane that allows the pilot to use the ILS consists of a glide slope and Localizer and a marker-beacon receiver. They show the pilot whether the airplane is to the right or left of the centerline and whether it is above or below the glide slope. The marker beacon receiver has a light display that shows when the plane passes over each marker beacon. As the plane crosses each marker beacon, the radio speaker can also broadcast a tone if the pilot has turned on this feature.
The pilot has to fly within range of the ILS in order to use it. When the pilot is approaching an airport, ATC directs the pilot to where the plane will be in range of the ILS. The pilot also tunes his navigational receivers to the ILS frequency.
An ILS consists of two independent sub-systems, one providing lateral (course line) guidance, and the other vertical (glide slope) guidance to aircraft approaching a runway.
Normally approaching aircraft will be flying at an altitude which places them at an altitude between 3000 feet and 4000 feet to pick up the glide-slope. At times it is possible that due to temporary restrictions an aircraft may be coming in higher than normal in these cases the approach clearance needs to include the advise to the pilot that he can follow the glide or not to follow the glide as the case may be.
ExAir123, turn left heading 090, cleared ILS runway 12 Descend on the glide.
ExAir123, turn left heading 090, cleared ILS runway 12, maintain 3000 feet until 5 nm from the runway.
Modern localizer antennas are highly directional. However, usage of older, less directional antennas allows a runway to have a non-precision approach called a localizer back course. This lets aircraft land using the signal transmitted from the back of the localizer array. This signal is reverse sensing so a pilot would have to fly opposite the needle indication. Highly directional antennas do not provide a sufficient signal to support a back-course. Back-course approaches are commonly associated with Category I systems at smaller airports, that do not have an ILS on both ends of the primary runway.
5.7.2. Marker Beacons [S+]
On some installations marker beacons operating at a carrier frequency of 75 MHz are provided. When the transmission from a marker beacon is received it activates an indicator on the pilot's instrument panel and the modulating tone of the beacon is audible to the pilot. The height at which these signals will be received in an aircraft on the correct glide slope is published.
The marker beacons are directed upward within a relatively narrow space. These beacons serve as checkpoints to tell the pilot the airplane's position. Some systems use three marker beacons-an outer, middle, and inner-while others use only an outer and middle beacon. These marker beacons tell the pilot that he has reached an important place along the approach path. For instance, it might tell the pilot that the plane's landing gear should be lowered.
- The outer marker should be located 7.2 km (3.9 NM) from the threshold except that, where this distance is not practicable, the outer marker may be located between 6.5 and 11.1 km (3.5 and 6 NM) from the threshold. The modulation is two dashes per second of a 400 Hz tone, the indicator is blue. The purpose of this beacon is to provide height, distance and equipment functioning checks to aircraft on intermediate and final approach.
- The middle marker should be located so as to indicate, in low visibility conditions, that visual contact with the runway is imminent, Ideally at a distance of 1050m from the threshold. It is modulated with a 1300 Hz tone as alternate dots and dashes.
- The inner marker, when installed, shall be located so as to indicate in low visibility conditions the imminence of arrival at the runway threshold. This is typically the position of an aircraft on the ILS as it reaches Category II minima. The modulation is 3000 Hz dots at 6 per second.
5.7.3. DME [S+]
Distance Measuring Equipment is replacing markers in many installations. This provides more accurate and continuous monitoring of correct progress on the ILS to the pilot, and does not require an installation outside the airport boundary. The DME is frequency paired with the ILS so that it is automatically selected when the ILS is tuned.
5.7.4. ILS Categories [S+]
As outlined in the training manual there are 3 types of ILS Precision Approach Procedures which we recap bellow:
- Approach CAT I: Operation down to minima of 200 ft. decision height (DH) and runway visual range (RVR) 550 Meters. with a high probability of success. (When RVR is not available, 800 meters ground visibility is substituted.)
- Approach CAT II: Operation down to minima 100 ft. decision height (DH) and runway visual range (RVR) 300 Meters.
- Approach CAT III: Operation down to minima prescribed in the carrier’s operating specifications in the operator’s operations manual from a DH of 50ft and RVR of 100 Meters to as low as 0 ft DH and 0 Meters RVR
As you can see Category one (CAT I) is the less accurate, and CAT III is the most accurate. Meaning that the PIC can fly the approach to lower limits (decision heights) on a CAT III ILS than on a CAT I ILS.
In turn all depends on the actual Runway in use, not all runways are equal, some may offer a higher CAT level than others, we therefore also speak about Precision Runways.
5.7.5. Runway Categories [S+]
The visibility is the limiting factor on an approach. If the Cloud base is at 50 ft, but the visibility is 600 meters, you may fly and land with a CAT I ILS. The chances that you can see the runway at 200 ft are very limited, but maybe the approach lights are very bright.
The Precision Runway is one which is served by visual aids and non-visual navigation aids providing lateral and vertical guidance to the operating minima as outlined below in precision Runway CATI, CATII and CATII
- Precision runway CAT I: A runway adequate for instrument approach down to a decision height (DH) lower than 250 ft., but not lower than 200 ft., above "height above aerodrome" (HAA) or "height above touchdown" (HAT) and in operating visibility not less than 0.5 SM or RVR 550 Meters.
- Precision runway CAT II: A runway adequate for instrument approach down to a decision height (DH) lower than 200 ft., but not lower than 100 ft., above "height above aerodrome" (HAA) or "height above touchdown" (HAT) and in operating visibility not less than RVR 300 Meters.
- Precision runway CAT III: which is subdivided into a further there types of precision runway CAT III:
- CAT III A: Operations are conducted or intended to be conducted down to a runway visual range (RVR) not less than 100 Meters and a DH of 50ft.
- CAT III B: Operations are conducted or intended to be conducted down to an RVR not less than 50 Meters. (no DH being applicable).
- CAT III C: Operations are conducted or intended to be conducted with no DH and no RVR limitations.
5.7.6. Other Limiting Factors [S+]
There are more factors which can change the limit such as:
- Pilot Qualification
- Aircraft Classification
Typical Aircraft Classification are:
- CAT A : F50, ATR42, Dash 800
- CAT B : DC9, MD80 & 90 Series, B737, A320
- CAT C : B767, B777, B747, DC10, MD11, A330, A340