Oceanic Air Traffic Services

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Oceanic Air Traffic Services
Will Tidmarsh VATPAC
An overview
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Outline

• Overview of Oceanic Procedures in VATPAC
• Some pictures and real world examples
• Not intended to be a tutorial on oceanic
  techniques these are covered in VATPACs
  Oceanic Manual.
• Questions welcome any time (VATPAC or Real World
  flying, etc). But remember Im only a pilot!

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What is Oceanic Airspace?
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Oceanic Airspace What is it?

• Controlled and uncontrolled airspace over the
  worlds major oceans.
• Nadi FIR Class A
• Brisbane FIR Class A down to 60 South, then
  Class G (uncontrolled).
• Lack of radar coverage means aircraft separation
  is achieved using procedural methods

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Oceanic Airspace VATPAC?
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Procedural Fundamentals

• Two types of procedural separation
• Longitudinal
• one aircraft following another
• one aircraft climbing or descending through the
  level of an opposite direction aircraft
• one aircraft crossing the path of another
• Vertical
• An aircraft cruising or crossing above or below
  another
• Both types are used regularly!

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Longitudinal Separation Basics

• Can use time or distance, but time is the most
  common worldwide (also the most basic no need
  for special ground or aircraft equipment).
• Eg. Most flights SE Asia Europe spend around 6
  hours flight time under time-based longitudinal
  separation.

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Longitudinal Separation Basics

• Time
• Distance
• DME
• RNAV (RNP)
• Here are some useful standards

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Basic Time Standards

• 15 minutes between following aircraft
• If Mach Number Technique used, this is reduced to
  a nominal 10 minutes

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Basic Time Standards contd

• Where aircraft tracks cross each other, 15
  minutes separation is required at track
  intersection.

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Basic Time Standards contd

• Time standards are often cumbersome and very
  conservative
• They restrict traffic flow and airspace capacity
• A big problem on routes from SE Asia to Europe
• Afghanistan is the bottleneck
• Non-RVSM
• Only two routes through the country
• Extensive enroute holding, delays (costly!)
• Solution? BOBCAT!
• Bay of Bengal Cooperative Air Traffic Flow
  Management System
• A centralised flow management system. Takeoff
  Slot times for aircraft departing SIN, BKK and
  KUL at peak times.
• Aims to arrange aircraft into a steady flow
  separated by 10 minutes by the Afghanistan
  (Kabul) FIR boundary
• So far so good

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Basic Distance Standards - DME

• Achieved by comparing distance of two (or more)
  aircraft from a common DME station.
• Eg. Air Canada 522 and Qantas 127, in turn,
  request your DME distance Lord Howe Island
• Only applicable to aircraft on the same or
  closely converging tracks not crossing tracks
• Requires regular distance checks and updates when
  used (to ensure separation is being maintained)

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DME Standard contd

• 20nm separation required between following
  aircraft (15nm if one aircraft climbing or
  descending through the level of another)
• Opposite direction aircraft may climb or descend
  through anothers level once the aircraft have
  passed and there is 10 DME difference between
  them
• Accurate technique (and reduced separation
  standard), but very few DME stations in oceanic
  areas!

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Basic Distance Standards - RNAV

• RNAV refers to an Area Navigation system this
  is usually an aircrafts FMS.
• RNAV distance-based separation may be applied
  between RNAV-equipped aircraft only
• FMS positions are very accurate! So RNAV
  separation standards can be lowered.
• The most efficient form of procedural airspace!

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RNAV Standard contd

• Oceanic airspace often specifies a Required
  Navigation Performance or RNP (eg. RNP10).
• This is a statistical value, and represents the
  maximum cross-track error (in nautical miles)
  expected 95 of the time by aircraft in that
  airspace.
• VATPAC has adopted RNP10 as the standard for its
  Oceanic Airspace.
• (Real world has widely adopted RNP4 in oceanic
  areas, but this requires ADS/CPDLC - to be
  discussed).

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RNP10 Separation Standards

• RNAV RNP10 aircraft climbing, cruising or
  descending on the same track must be separated by
  at least 50nm (with the Mach Number Technique),
  provided that
• each aircraft reports its distance to or from the
  same waypoint
• simultaneous distance checks are regularly
  carried out to ensure that the 50nm separation is
  being maintained
• in the case of aircraft climbing or descending,
  one aircraft maintains a level while vertical
  separation (eg. 1000ft) does not exist

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RNP10 Separation contd

• Aircraft on converging or diverging tracks are
  laterally separated using a table of track angle
  versus distance. This table is reproduced in the
  Oceanic Procedures Manual.
• Opposite direction aircraft may climb or descend
  through the others level after visually sighting
  and passing each other or once 50nm RNAV distance
  has elapsed.

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Recap -Longitudinal Separation

• Time (15 mins, or 10 mins Mach No.)
• Distance
• DME (good, but rare in Oceanic Airspace)
• RNAV (RNP10) (great, when both aircraft approved
  and fitted)
• Next, Vertical Separation

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Vertical Separation Standards

• Primitive, but fail-safe!
• Advent of RVSM (Reduced Vertical Separation
  Minima) has enabled aircraft with accurate
  altimetry systems to be separated by 1000ft
  vertically, rather than 2000ft.
• Has effectively doubled capacity of upper
  airspace
• In the real world, some areas still yet to
  implement RVSM (and are therefore bottlenecks!)
  including.

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Afghanistan
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China (metric altimetry!)
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Vertical Separation contd

• Aircraft being separated by solely vertical means
  shall have the following separation minima
  applied
• 1000ft in RVSM airspace, between RVSM capable
  aircraft
• 2000ft in RVSM airspace, where one or both
  aircraft not RVSM capable
• 2000ft in non-RVSM airspace, at and above FL290
• 1000ft in non-RVSM airspace, below FL290
• 3000ft where one or both aircraft are supersonic
• Note In VATPAC airspace, RVSM exists between
  FL290FL410 (inclusive)
• Some aircraft arent RVSM approved or certified,
  or are incapable of RVSM ops on the day. Eg

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Spare Engine (Fifth Pod) Ops
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Ugly, but useful
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Oceanic Communications

• VHF range insufficient, so High Frequency (HF)
  Radio used. Very long range!
• Noisy and prone to atmospheric interference. (But
  this adds charm!)
• So, radio procedures are more formal
• UAL873 San Francisco, San Francisco, United 873
  on 8867khz
• San Francisco United 873, San Francisco, go
  ahead
• UAL873 San Francisco, United 873 request climb
  FL390

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HF Comms contd - SELCAL

• Selective Calling (SELCAL) allows crews to turn
  their radios down
• If ATC needs to contact the flight, they
  broadcast a unique four letter DTMF code
  corresponding to that aircraft. This activates a
  chime on the flight deck.
• SELCAL is checked with ATC prior to tuning out
• Eg.
• Auckland Evergreen 6985 roger, FL310, Auckland
  guard primary this frequency, secondary 8867,
  LM-AF his four letter SELCAL code.. selcal

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HF Comms contd

• When in VATPAC Oceanic Airspace, voice
  communications are assumed to be on simulated
  HF.
• SELCAL is also simulated.
• The procedures for HF and SELCAL are described in
  the Oceanic Procedures Manual.

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Oceanic Procedures Manual

• This is the primary reference document for
  Oceanic ATC within VATPAC and VATNZ. Presented in
  a user-friendly manner with separation and
  airspace diagrams etc.
• Detailed information on
• Separation standards and techniques
• Position reports
• Communications and simulated SELCAL procedures
• Controller co-ordination
• Pacific airspace classification, callsigns and
  frequencies
• Special VATSIM procedures (eg. time compression)
• Oceanic Controller Endorsement (required for
  controllers)
• Available from VATPAC website.
• Controlling in Oceanic Airspace is an enjoyable
  challenge!

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Real World CPDLC (Datalink)

• The last few years have seen the widespread
  uptake of Controller-Pilot Datalink
  Communications (CPDLC) in many FIRs.
• Connection is established between the aircrafts
  Flight Management Computer and the controllers
  workstation via satellite (or via an ACARS VHF
  ground station, when in range).
• Firstly, we must log on

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CPDLC (Datalink) contd

• Once logged on, we can communicate with the
  controller using pre-formatted or free text
  messages, and send position and meteorological
  data.

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CPDLC (Datalink) contd

• Or even small-talk!

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Real World ADS

• Automatic Dependent Surveillance (ADS) technology
  becoming increasingly widespread.
• The aircraft FMC automatically downlinks aircraft
  position data to the Controller every 30 seconds
  or so, giving a radar-like display of aircraft
  position.
• This allows separation standards to be even
  further reduced (eg. from RNP10/50nm to
  RNP4/30nm)!
• Already implemented in real world South Pacific
  and USA Oceanic airspace.

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Question time!
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Thank you!