5. In the Air

5. In the Air

5.1.1.  General

5.1.2.  Vertical  Separation

5.1.3  Horizontal Separation

5.2. Departure and Sid

5.3. Routes

5.3.1. Route Components

5.3.2. Complete Routes

5.3.3.Airways - Flight Levels and Direction of Flight

5.4. STAR and Arrival 

5.5. Approaches

5.5.1. Type of Approaches

5.5.2. General Principles

5.5.3. Instrument Approaches

5.5.4 Precision Approaches

5.5.5 Non Precision Approaches

5.5.6 Straight In Approach

5.5.7. Circling Approach

5.5.8. ARC Appropach

5.5.9. Visual Approach

5.5.10. Full Procedure Approach 

5.5.11 Further Reference

5.6 Airfield Traffic Pattern

5.6.1. Traffic Pattern

5.6.2. Wind Direction

5.6.3. Layout

5.6.4. Overhead Join

5.6.5. Contra Rotating Pattern

5.6.6. Altitude

5.6.7. Helicopters

5.7 ILS

5.7.1 Course and Glide Slope

5.7.2. Marker Beacons

5.7.3. DME

5.7.4. ILS Categories

5.7.5 Runway Categories

5.7.6. Other Limiting Factors

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5. In the Air  [S]

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

5.1. General  [S]

9.1 VFR – Visual Flight Rules

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.

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5.1.2. Vertical Separation  [S+]

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.

Three easy guidelines for maintaining the vertical separation are 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.

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5.1.3. Horizontal  Separation  [S+]

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
Or
ExAir123, Turn right heading…re-cleared direct ABC VOR
Or
ExAir123, Resume Own Navigation direct ABC VOR (could be misunderstood on VATSIM)

 

Rather than expanding here on different examples we suggest you download an excellent stand alone Separation Tutorial written by the SAG VACC which can be found at:

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Note: Tutorial link to SAG VACC was changed to internal upload due to ISP changes
(Used with the kind permission of SAG VACC)

5.2. Departure and SID  [S+]  

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.

5.3.Route   [S+]  

5.3.1. Route Components   [S+]  

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.

5.3.2. Complete Routes  [C]  

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.