Global Positioning System

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Global Positioning System

• What pilot/students need to know!

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GPS Generally

• The GPS is a U.S. satellite based radio
  navigational , positioning, and time transfer
  system operated by the DoD.
• The system provides highly accurate position and
  velocity information and precise time on a
  continuous global basis to properly equipped
  users.

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There are two levels of service

• Standard Positioning Service (SPS)
• Precise Positioning Service (PPS)

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(SPS) and (PPS)

• 100 meters-95
• 300 meters-99.99

• PPS Is more accurate than SPS however it is
  limited to authorized U.S. and users who can
  satisfy specific U.S. requirements

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Each satellite transmits specific code

• It is called a CA or Course/Acquisition code.
• It contains information on the satellites
  position,GPS system time, clock error and the
  health and accuracy of the data.

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Your Receiver...

• matches each satellites CA Code with an identical
  copy of the code contained in the receivers
  database.
• By shifting the receivers code its matching the
  satellite and by comparing this shift with the
  satellite internal clock...wala!..magic!

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Measuring distance

• The distance derived from this computing is
  called pseudo-range because it is not a direct
  measurement but rather, measurement based on
  time.
• Your receiver needs to know the satellites exact
  position in space
• The receiver does the math to tell you where you
  are!

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There are 24 satellites

• A minimum of five satellites are always
  observable by a user anywhere on earth.
• On December 8, 1993 the FAA granted approval to
  use GPS to conduct oceanic, domestic enroute,
  terminal IFR operations, and certain instrument
  approach procedures, under specified conditions

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General Requirements

• The GPS equipment must be approved in accordance
  with TSO C-129.
• Aircraft using GPS under IFR must be equipped
  with an alternate means of navigation.
• Procedures must be established if satellite
  reception is impaired, i.e.. delay or cancel
  flight.

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...more conditions

• The GPS flight must must be conducted in
  accordance with FAA-approved flight manual or
  flight manual supplement.
• Aircraft navigating by GPS are considered (by
  ATC) to be RNAV aircraft. The /R on the flight
  plan tells them that.(GPS goes in remarks)
• Prior to flight GPS NOTAMS

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There are/were three Phases of operations...

• Phase 1 You can use GPS only if ground-based nav
  equipment is monitored and operational.
• Phase II GPS without actively monitoring
  ground-based nav equipment..avionics must be
  installed an working..but not turned on.
• Phase III is where approach plates are titled
  GPS and you do not need other nav gear.

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References

• Aeronautical Information Manual (Navigation Aids
  Chapter 1 Page 1-36)
• FAA Advisory Circular AC 90-94 Guidelines for
  using GPS for IFR...

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Lets talk about the 3 Phases!

• Phase 1 ended February 1994 when the FAA declared
  GPS operational for civil operations.
• Phase II began February 1994 when the FAA
  declared the system useable.
• (Dont need to actively monitor ground-based as
  long as something tells you GPS is working.

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Phase III

• Phase III requires modification of the instrument
  approach procedure name to include GPS on the
  chart. You need neither the traditional avionics
  nor the ground station navaid(s) to be
  operational or monitored to fly non precision
  approach...if RAIM is monitoring the integrity of
  your GPS System.

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What is RAIM

• Receiver Autonomous Integrity Monitoring.
• Your receiver tells you if you are receiving
  adequate signal to fly the GPS...if not, delay
  the flight or cancel as appropriate.
• The reason being that Phase I,II, III have
  additional criteria

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To repeat...

• GPS must be TSOd
• Receiver should have database with airport of
  choice...and no LOC, LDA or SDF approach.
• If approach not in database..it is probably
  unsafe that is why it is not there.
• GPS should store all waypoints depicted on the
  approach chart.

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...more

• Approach must be flown in accordance with FAA
  Aircraft Flight Manual or flight manual
  supplement.
• Any required alternate airport should have an
  approved instrument approach other than
  GPS...NOTAMS is a pilot responsibility.
• The GPS overlay approaches are limited to the
  U.S. national airspace.

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and last but not least...!

• Procedures should be established by the pilot in
  the event of GPS outages..meaning rely on other
  equipment, delay departure or discontinue IFR
  operations.

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Pilot Operations

• To quote AC 90-94, ...All pilots must be
  thoroughly familiar with GPS equipment installed
  in the aircraft and its limitations.
• The pilot should follow the specific start-up and
  self-test procedures for the GPS receiver as
  outlined in the FAA AFM or Flight Manual
  Supplement.

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GPS NOTAMS

• Request from Briefer
• Use identifier GPS, through the Direct User
  Access Terminal System (DUATS)
• ..remember, if the NOTAMS indicate GPS is not
  working...the approach is not authorized.

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Appropriate Approach

• The pilot must select appropriate approach from
  GPS receiver to determine RAIM integrity for that
  approach.
• If GPS is out amend /R flight plan.

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How about the alternate?

• If the GPS aint working...the alternate must
  have an approved approach...other than GPS
  or..Loran-C!...which is anticipated to be
  operational at the estimated time of arrival!
• What do you use?
• ILS, NDB...?

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GPS
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Thats all Folks!